JP2006192438A - Multi-layered welding method of narrow bevel joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To change the tensile stress remained in a weld part on a back side and a face side of a multi-layered weld of a bevel joint of a thick plate into the compressive stress, or to drastically reduce the tensile stress. <P>SOLUTION: In a bevel joint, residual stresses must be reduced at a part of the single side welding and a back side of the welding from a bottom part to a top part of a bevel at which tubular members or plate members such as a container and a pipe consisting of thick austenitic stainless steel butted to each other. In a multi-layered welding method of a narrow bevel joint, the arc welding for laminate welding is performed to the top part of the bevel by properly using two wires of different materials. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-layer welding method for groove joints in which pipe members or flat plate members such as containers and pipes made of thick austenitic stainless steel are abutted against each other, and in particular, the back side and the surface after welding is finished. The present invention relates to a multi-layer welding method for a narrow groove joint that is effective in changing or significantly reducing the tensile stress remaining in the welded portion on the side to a compressive stress.

  Austenitic stainless steel materials used in welded structures such as containers, pipes, and components of nuclear power plants and thermal power plants tend to precipitate Cr carbide at the grain boundaries due to welding, and a Cr-deficient layer near the grain boundaries. It is known that crack formation (sensitization of material) against corrosion is enhanced by the formation of the above. Further, a high tensile residual stress exists in the welded portion (welded metal portion and adjacent heat affected zone), and stress corrosion cracking is likely to occur when used in a severe corrosive environment such as high-temperature water. In order to prevent this stress corrosion cracking, it is necessary to remove one factor from the three factors of sensitization of the material, tensile stress, and corrosive environment. For this reason, in particular, it is strongly required to change or significantly reduce the tensile stress remaining on and near the surface of the welded portion exposed to a corrosive environment such as high-temperature water.

  Conventionally, several welding methods and welding apparatuses for reducing the tensile residual stress of the welded material portion have been proposed. For example, in the piping system heat treatment method described in Patent Document 1 (Japanese Patent Publication No. 53-38246), cooling water is present inside the pipe after welding assembly, and the outside of the pipe is heated so that the inner surface of the pipe and the pipe are heated. It has been proposed to generate a temperature difference with the outer surface, to cause tensile yielding of the inner surface of the tube, and compression yielding of the outer surface of the tube.

  In the preventive maintenance method and apparatus for an austenitic stainless steel welded part described in Patent Document 2 (Japanese Patent Laid-Open No. 2001-141629), the high-frequency heating coil is moved while following the linear welded part, and this high-frequency heating is performed. It has been proposed to have a procedure for heating a welded part to a temperature higher than the stress yield point temperature by a coil, and a procedure for rapidly cooling a jet of cooling water in an overheated region.

  On the other hand, in the method and apparatus for joining metal parts described in Patent Document 3 (Japanese Patent Publication No. 9-512485), the welding material is continuously applied in the vicinity of the tip of the electrode tip that travels at a selected speed (127 cm / min or more). A welding current is continuously melted in the groove by a discharge current from the tip, and a weld bead is formed, and the electrode is joined and electrically connected to the tip. It has been proposed to achieve a final residual stress state that is compressible over a predetermined number of weld passes and is generated without an external heat sink medium.

  Moreover, in the multilayer prime welding method of the narrow groove joint of the austenitic stainless steel described in Patent Document 4 (Japanese Patent Publication No. 62-19953), the layer near the groove deepest portion is made of an austenitic filler material. It has been proposed to weld (weld) and weld at least one outer layer adjacent to the layer using a martensitic filler material.

  Furthermore, in the welding method and welding material described in Patent Document 5 (Japanese Patent Laid-Open No. 11-138290), a martensitic transformation is caused in the weld metal generated by welding in the cooling process after welding, and the weld metal is at room temperature. It has been proposed to make a state of expansion from the start temperature of martensitic transformation (for example, less than 250 ° C. and 170 degrees or less).

Further, in the TIG welding method and solid wire for TIG welding of high-strength steel described in Patent Document 6 (Japanese Patent Application Laid-Open No. 9-253860), the martensitic transformation start temperature of all weld metals is 400 ° C. or less, Welding using solid wire with 7.5 to 12% Ni, C 0.1% or less and H 2ppm or less, with wire feed rate 5-40g / min. It has been proposed to do.

Japanese Patent Publication No. 53-38246 (Patent No. 957324) JP 2001-141629 A Japanese National Patent Publication No. 9-512485 (Patent No. 3215427) Japanese Examined Patent Publication No. 62-19953 (Patent No. 1415054) JP 11-138290 A (Patent No. 3350726) JP-A-9-253860

  In the case of the said patent document 1, it is thought that it is an effective method for changing the tensile residual stress of the piping inner surface which had arisen at the time of welding assembly into a compressive residual stress. However, not only large-scale high-frequency heating equipment different from the welding equipment is required, but also work man-hours and costs for heating the outer peripheral portion at a high temperature while supplying cooling water to the inner peripheral portion of the pipe after welding is required. Become.

  Moreover, in the case of the said patent document 2, the device for reducing a tensile residual stress is made | formed. However, after completion of welding, high-temperature heating is performed by a high-frequency coil that moves on the surface of the linear welding site, and the superheated area is rapidly cooled by jetting cooling water, so that mobile heating and water-cooling facilities are required. In addition, work man-hours and costs for implementing this high-temperature heating and rapid cooling are required.

  On the other hand, in the case of the above-mentioned Patent Document 3, there is a device for reducing the tensile residual stress and the welding strain by using the heat self-cooling effect of the high heat efficiency welding construction and the narrow groove joint without using the heat sink medium outside. Has been. However, there is a high possibility that this tensile residual stress is not changed to a compressive residual stress. In addition, since a thin electrode formed in a non-cylindrical shape (non-circular cross section) different from an inexpensive circular cross-section tungsten electrode rod is used, this thin electrode is expensive to manufacture, and it is also in the groove. The cost of electrode replacement accompanying the consumption of the electrode tip that occurs when inserting and arc welding is also high. As the wire (melting material) supplied and melted in the groove, an austenitic wire having the same composition as the groove joint material to be welded is used, and a martensite wire different from this wire is not used.

  Moreover, in the case of the said patent document 4, in order to reduce the tensile residual stress of a pipe inner surface, the material of a groove joint and the austenite type | system | group wire and martensite type | system | group wire of the same quality are used and welded separately. Although effective in reducing the tensile residual stress, the tensile stress still remains and has not yet been changed to a compressive stress. Further, the martensitic wire is used only for the welded portion of the intermediate layer in the groove, and is not used for the welded portion of the final layer on the groove surface. In addition, since the groove joint has a wide angle, when welding a thick groove joint, the groove cross-sectional area to be welded and the groove shoulder width increase, making it difficult to weld one layer at a time for each pass. 1 and multipass multi-layer welding is required, and there is a high possibility that tensile residual stress and shrinkage deformation increase. The welding method is unknown, but assuming from the examples, there is a high possibility of an arc welding method using a welding wire (a filler metal) as an electrode rather than an arc welding method using non-consumable tungsten as an electrode. .

  Moreover, in the case of the said patent document 5, in order to improve the fatigue strength of a welded joint, it welds using the welding material (it corresponds to a welding wire) which produces a martensitic transformation. Welding objects are mainly welded structures of low-alloy steel materials (such as high-strength steel materials) and cannot be applied to welding austenitic stainless steel materials of different materials. In addition, the place where the tensile residual stress generated by welding is reduced is the welded surface part of fillet joints, T joints and cross joints, or the surface part of double-sided welding of X groove joints. It does not apply to the weld back surface portion that is required for single-sided welding such as a point joint. Furthermore, the welding method is an arc welding method using a welding wire as an electrode, and not an arc welding method using non-consumable tungsten as an electrode.

  In the case of Patent Document 6, it is considered effective for preventing weld cracking of high-strength steel, but it cannot be applied to welding of stainless steel materials of different materials.

  In addition to this, several welding methods have been proposed in which welding is performed using a welding wire that causes martensitic transformation, but it is mainly intended for welding high-tensile steel materials, and not for austenitic stainless steel materials. It is. Similarly to Patent Document 6, the portion of the tensile residual stress that is reduced by welding is the weld surface portion, and the weld back surface that is required for single-sided welding such as a narrow groove joint having a different joint shape and penetration shape. The part is not targeted.

  The object of the present invention is to successfully perform multi-layer welding for laminating from the first layer back wave welding of the groove bottom necessary for the groove joint of the thick plate to the final layer welding of the groove upper surface, and after completion of welding. It is an object of the present invention to provide a multi-layer welding method for a narrow groove joint which is effective for changing or greatly reducing the tensile stress remaining in the welded portion on the back surface side and the front surface side into a compressive stress.

  In order to achieve the above-mentioned object, the inventors of the present invention provide a multi-layer welding method for a narrow groove joint in which a groove in which a pipe member or a flat plate member are butted against each other is laminated and welded from one side. A first welding step using the same kind of wire as the pipe member or flat plate member within a range of 1/5 to 4/5 of the member thickness from the start of welding, and welding from the remaining portion after the first welding step And a second welding process using a wire having a smaller linear expansion coefficient than the tube member or the flat plate member in the range up to the final layer.

  According to the multi-layer welding method of the narrow groove joint of the present invention, by using two kinds of wires and laminating and welding, expansion action and tension are generated in the weld metal part on the surface side, The tensile stress remaining in the vicinity thereof can be changed to a compressive stress, and at the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. As a result, it can contribute to the prevention of residual stress corrosion cracking and the extension of the device life.

  Moreover, the groove sectional area to be welded can be reduced, the amount of wire used can be reduced, and the number of welding steps can be reduced.

  The present invention requires single-sided welding and reduction of residual stress in the welded back surface portion from the groove bottom portion to the groove upper surface portion where pipe members or flat plate members such as containers and pipes made of thick austenitic stainless steel are butted against each other. In the multi-layer welding method of a narrow groove joint, which is a groove joint and uses arc welding to perform lamination welding to the groove top surface using two different types of wires, the total number of laminated bead heights to be welded is The groove depth reaches from 1/5 to 4/5 from the groove back surface, or the remaining groove depth reaches from 1/5 to 4/5 from the groove surface. Until, using the austenitic wire of the same quality as the material of the groove joint, pulse arc welding or direct current arc welding of the non-consumable electrode method of laminating in order from the first layer back wave welding of the groove bottom, And A non-consumable electrode type pulse arc that is used by switching to a martensite wire different from the stenite wire and laminating in order from the welding of the remaining portion in the groove to be continued to the final layer welding of the upper surface of the groove. A multi-pass welding method for narrow groove joints, characterized by performing welding or DC arc welding, is proposed.

  Further, in order to achieve the above object, the present invention provides a single-side welding from a groove bottom portion to a groove top surface portion where a tube member or a flat plate member such as a vessel or piping made of thick austenitic stainless steel is abutted against each other. And a groove joint that requires a reduction in residual stress on the back surface of the weld, and a multi-layer prime welding method for a narrow groove joint that performs arc welding in which two types of wires of different materials are selectively used up to the top surface of the groove The groove width including the groove width of the groove bottom part or the width of the insert material inserted in the center of the groove bottom part is preliminarily formed to a dimension of 4 mm or more and 8 mm or less at the maximum. When one side angle of is formed into a narrow groove shape of 10 ° or less and multilayer build-up welding is performed, the cumulative laminated bead height to be welded is 1/5 or more to 4/5 or less of the plate thickness from the groove back surface. Reach or remain Until the groove depth reaches a range of 1/5 or more to 4/5 or less of the plate thickness from the groove surface, using an austenitic wire of the same quality as the material of the groove joint, Perform non-consumable electrode-type pulse arc welding or direct current arc welding, which are laminated in order from the first layer back wave welding, and then replace and use a martensitic wire different from the austenitic wire, and a groove to be continued. The non-consumable electrode type pulse arc welding or direct current arc welding is performed in order from the welding of the remaining portion to the final layer welding of the upper surface portion of the groove, or replaced with an Inconel wire or the groove joint. Used as a replacement for other austenitic wire with a coefficient of linear expansion smaller than that of the material, reaching the final layer weld on the upper surface of the groove from the remaining weld in the groove to be continued Suggest narrow groove joint method of multi-pass welding and performing pulsed arc welding or DC arc welding of the non-consumable electrode method of laminating in sequence until the.

  Further, in order to achieve the above object, the present invention provides a single-side welding from a groove bottom portion to a groove top surface portion where a tube member or a flat plate member such as a vessel or piping made of thick austenitic stainless steel is abutted against each other. And a groove joint that requires a reduction in residual stress on the back surface of the weld, and a multi-layer prime welding method for a narrow groove joint that performs arc welding in which two types of wires of different materials are selectively used up to the top surface of the groove The groove width including the groove width of the groove bottom part or the width of the insert material inserted in the center of the groove bottom part is preliminarily formed to a dimension of 4 mm or more and 8 mm or less at the maximum. Is formed in a narrow groove shape with a single groove angle of 10 ° or less, and the cumulative laminated bead height to be welded in the narrow groove is in the range from 1/5 to 4/5 of the plate thickness from the groove back surface. Reaching or remaining groove depth When welding is performed from the groove surface until it reaches a range of 1/5 or more to 4/5 or less of the plate thickness, an austenitic wire of the same quality as the material of the groove joint is used, and is narrower than the groove width. Insert a non-consumable electrode having a circular cross-sectional shape into the groove, or a non-consumable electrode in which the lateral width of the electrode lower than the electrode diameter is formed into a flat shape narrower than the groove width. Or another non-consumable electrode having a non-circular cross-sectional shape corresponding to a flat shape narrower than the groove width is inserted into the groove, and formed in and immediately below the arc generated at the tip of the inserted electrode. Non-consumable electrode type pulse arc welding or direct current so that the austenitic wire is fed into the molten pool to be melted and laminated one by one in order from the first layer back wave welding of the groove bottom Arc welding, then In welding work up to the upper surface of the groove to be laminated, replace with at least a martensitic wire different from the austenitic wire, or replace with an Inconel wire or a linear expansion coefficient smaller than the linear expansion coefficient of the groove joint material. It is used by exchanging with another austenitic wire having, and the exchanged wire is fed into the arc and the melt pool formed immediately below the arc to be melted, and the remaining portion in the groove to be continued is welded. The non-consumable electrode type pulse arc welding or direct current arc welding is performed so as to laminate one layer one pass at a time until the final layer welding of the groove upper surface is reached, or the one layer one pass is laminated. If necessary, the above-mentioned non-consumables are arranged so that two layers are stacked one by one as needed, or the final layer is welded with three additional welding passes. A multi-pass welding method for narrow gap joints is proposed, characterized by performing electrode-type pulse arc welding or DC arc welding.

  In addition, the insert material is provided in advance in the groove bottom center of the groove joint so as to protrude to the front side and the back surface side, and this insert material is an insert material made of austenitic stainless steel of the same quality as the groove joint material, Alternatively, an insert material that is the same material as the groove joint material and contains 0.008 to 0.015% of S (weight%), which is one of the chemical compositions, is higher than the groove joint material. Before the first-layer backside welding of the main welding, using the shallow penetration low heat input arc that does not melt to the back side and the temporary attachment condition without wire feed, Tack welding is performed so that the protruding portion of the insert material is melt-bonded, and after the tack welding is completed, the insert material and the joint portion protruding to the back side of the groove bottom portion are melted, and the back side Bee Width can be performed the first layer Uranami welding to form a range of specific values.

  In particular, in the construction of the first layer back wave welding, the first layer welding conditions of a heat input arc that can completely melt from the groove bottom on the front side to the back side are used, and one or more during pulse arc welding or DC arc welding. In this case, the melt pool width on the back surface side or the back bead width in the vicinity of the melt pool is adjusted to a specific value in the range of 4 to 7 mm, preferably in the range of 4 to 6 mm.

  In addition, in the welding construction to laminate from the welding of the remaining portion in the groove to be continued to the final layer welding of the groove upper surface portion, it is replaced with a martensite wire different from the austenite wire, or is replaced with an inconel wire. It is used by exchanging with another austenitic wire having a linear expansion coefficient smaller than the linear expansion coefficient of the groove joint material, and the last welding condition when welding is performed using the austenitic wire before the welding operation. Alternatively, the non-consumable electrode method is used by changing to a welding condition having a heat input smaller than the last welding condition, or by reusing the last welding condition or a welding condition equivalent to the last welding condition. Pulse arc welding or direct current arc welding can be performed. In particular, the martensitic wire contains at least 8 to 12% by weight of Ni of chemical composition and 8 to 12% by weight of Cr, and has a martensitic transformation start temperature of 100 ° C. or higher and 300 ° C. or lower. A wire may be used.

  That is, in the multi-layer welding method of the narrow groove joint of the present invention, the cumulative laminated bead height to be welded reaches or remains in the range from 1/5 to 4/5 of the plate thickness from the back of the groove. Until the groove depth reaches the range of 1/5 or more to 4/5 or less of the plate thickness from the groove surface, using the austenitic wire of the same quality as the material of the groove joint, By applying non-consumable electrode-type pulse arc welding or direct current arc welding, which are laminated in order from the first layer back wave welding, for example, the inner surface or bottom surface of the welding back surface exposed to a corrosive environment such as high-temperature water, and From this weld back surface portion to a predetermined groove depth, it can be reliably filled with austenitic weld metal of the same type as the groove joint material.

Thereafter, the non-consumable electrode is used by exchanging with a martensite wire different from the austenite wire and sequentially stacking from the welding of the remaining portion in the groove to be continued to the final layer welding of the groove upper surface portion. By applying pulse arc welding or direct current arc welding of the type, the martensite transformation and expansion effect by the martensite wire causes expansion action and tension in the weld metal part at room temperature, and the weld back side on the groove bottom side And the tensile stress remaining in the vicinity thereof can be changed to a compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. A martensitic wire undergoes martensitic transformation during the cooling process during welding, and is in a state of being expanded at a normal room temperature (for example, 20 ° C.) than at a martensitic transformation starting temperature (for example, 100 to 300 ° C.). It is preferable to use a martensitic stainless wire that is a metal and has good fusion properties with the welded joint material of austenitic stainless steel to be welded. For example, a martensitic stainless wire containing at least 8 to 12 wt% of chemical composition and 8 to 12 wt% of Cr and having a martensite transformation start temperature of 100 ° C. or higher and 300 ° C. or lower may be used.

  Furthermore, as a result of improving the residual stress by the above-described welding construction, it is not necessary to provide an expensive heat treatment apparatus for removing the residual stress or to perform the heat treatment after the welding is completed, thereby reducing the cost. it can.

  Further, in the multi-layer welding method of the narrow groove joint according to the present invention, the groove width of the groove bottom portion where the pipe member or the flat plate member is abutted with each other or the width of the insert material inserted into the center of the groove bottom portion is included. By forming the groove width to a minimum dimension of 4 mm or more and a maximum dimension of 8 mm or less in advance, and forming a single groove angle up to the groove upper surface to a narrow groove shape of 10 ° or less, the heat input per welding pass Not only can shrink deformation due to welding heat be reduced, but also the cross-sectional area of the groove to be welded can be reduced, so that the amount of wire used can be reduced and the number of welding steps can be reduced.

  In addition, when multi-layer welding is performed, as described above, the cumulative stacked bead height to be welded reaches or remains in the range from 1/5 to 4/5 of the plate thickness from the groove back surface. Until the tip depth reaches the range of 1/5 or more to 4/5 or less of the plate thickness from the groove surface, an austenitic wire of the same quality as the material of the groove joint is used. By performing non-consumable electrode type pulse arc welding or direct current arc welding, which are laminated in order from layer back wave welding, for example, the inner or lower surface of the weld back surface exposed to a corrosive environment such as high-temperature water and the like From the weld back surface portion to a predetermined groove depth, it can be reliably filled with austenitic weld metal of the same type as the groove joint material. Thereafter, the non-consumable electrode is used by exchanging with a martensite wire different from the austenite wire and sequentially stacking from the welding of the remaining portion in the groove to be continued to the final layer welding of the groove upper surface portion. By applying the pulse arc welding or direct current arc welding of the method, as described above, the martensite transformation and expansion effect by the martensite wire causes expansion action and tension in the weld metal part at room temperature, and the groove bottom surface The tensile stress remaining in the weld back surface side and the vicinity thereof can be changed to compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced.

  Also, instead of martensite wire, use in place of inconel wire or replace with other austenite wire having a linear expansion coefficient smaller than that of the groove joint material. The non-consumable electrode type pulse arc welding or direct current arc welding may be performed in which the layers are sequentially laminated from the remaining portion welding to the final layer welding of the groove upper surface portion. By exchanging with another austenitic wire or inconel wire having a linear expansion coefficient smaller than the linear expansion coefficient of the groove joint material, by laminating and welding from the remaining weld in the groove to the groove upper surface portion, A shrinkage suppressing action and a tension due to the deviation of the linear expansion coefficient occur in the weld metal portion, and the tensile stress remaining in the weld back surface portion on the bottom surface side and the vicinity thereof can be changed to a compressive stress or greatly reduced. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced.

  Furthermore, in the multi-layer welding method of the narrow groove joint according to the present invention, the accumulated bead height to be welded in the narrow groove shape is equal to the plate thickness of 1 from the groove back surface. / 5 to 4/5 or less, or when the remaining groove depth reaches from the groove surface to 1/5 or more to 4/5 or less of the plate thickness, Using an austenitic wire of the same type as the material of the tip joint, insert a non-consumable electrode having a circular cross-sectional shape with a diameter smaller than the groove width into the groove, or a lower electrode having a diameter larger than this electrode diameter A non-consumable electrode formed in a flat shape whose lateral width is narrower than the groove width, or another non-consumable electrode having a non-circular cross-sectional shape corresponding to a flat shape narrower than the groove width. Inserted into the arc, and the arc generated at the tip of the inserted electrode Non-consumable electrode type pulse arc welding so that the austenitic wire is fed and melted into a molten pool formed below, and the layers are laminated one by one in order from the first layer backside welding at the groove bottom. Or, by performing direct current arc welding, as described above, the inner surface or the bottom surface of the welded back surface exposed to a corrosive environment such as high-temperature water, and the groove joint material from the welded back surface portion to a predetermined groove depth. Can be reliably filled with austenitic weld metal of the same type, and weld beads for each welding pass can be stacked well. In addition, the amount of heat input for each welding pass and shrinkage deformation due to welding heat can be reduced, and the amount of welding wire used can be reduced and the number of welding steps can be reduced.

  In particular, in the case of a non-consumable electrode having a small circular cross-sectional shape, not only can it be used for the pulse arc welding or the direct current arc welding, but it can be obtained at a low cost, and only the tip of the round electrode rod is a simple electrode polisher. Conical processing can be easily performed, and even when a part of the tip is consumed due to welding, it is easy to rework or attach / remove the consumable part. Further, in the case of a non-consumable electrode in which the width of the lower portion of the large-diameter electrode is formed in a flat shape narrower than the groove width, manufacturing costs for making the flat shape are required. Similarly, only the tip of the electrode can be easily conical processed with a simple electrode grinder, and attachment and removal operations are also easy. In addition, other non-consumable electrodes having a non-circular cross-sectional shape corresponding to a flat shape narrower than the groove width can be used.

  Further, in the welding operation up to the groove upper surface portion to be laminated thereafter, as described above, by replacing the austenite wire with a martensite wire and laminating and welding one layer at a time, each welding pass Welding beads (welded metal of martensitic wire) can be well stacked up to the upper surface of the groove, and as described above, the martensitic wire is welded at room temperature due to the martensitic transformation and expansion effects. An expansion action and tension are generated in the metal portion, and the tensile stress remaining in the weld back surface portion on the groove bottom surface side and in the vicinity thereof can be changed to a compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and the vicinity thereof can be reduced. Further, as described above, the amount of heat input for each welding pass and shrinkage deformation due to welding heat can be reduced, and the amount of welding wire used and the number of welding steps can be reduced. Further, in the course of laminating one pass at a time, the groove is divided into left and right as needed, and laminated one layer by two passes, or the final layer is increased to three passes, and the groove becomes difficult to melt in one pass. Even if the wall surface has a width, both wall surfaces of the groove width can be reliably melted even under the condition that the heat input arc is kept under the same condition or a little lower, and a good welding result can be obtained up to the groove upper surface portion. Furthermore, the cumulative bead width of the final layer can be increased, and the tensile stress remaining on the weld surface portion of the final layer and its vicinity can be reduced. Further, in the welding operation up to the groove upper surface portion to be laminated, in place of the martensite wire, it is replaced with an Inconel wire, or other austenite system having a linear expansion coefficient smaller than the linear expansion coefficient of the groove joint material Switch to a wire and, as described above, stack one layer at a time until welding reaches the final layer weld on the groove upper surface from the welding of the remaining portion in the groove, By performing the non-consumable electrode type pulse arc welding or direct current arc welding so as to be laminated to the left and right as needed and laminated one layer by two passes, or the final layer welding pass is laminated to three passes, Shrinkage suppression action and tension are generated in the weld metal part due to the deviation of the linear expansion coefficient, and the tensile stress remaining in the weld back side and its vicinity on the bottom side can be changed to compressive stress or greatly reduced.At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. Moreover, even if the wall surface has a groove width that is difficult to melt in one pass, not only can both wall surfaces of this groove width be melted reliably, but also a good welding result can be obtained up to the groove upper surface part. The accumulated bead width of the final layer can be made wider.

  In the multi-layer welding method of the narrow groove joint of the present invention, an insert material is provided in advance in the center of the groove bottom of the groove joint so as to protrude to the front side and the back side, respectively. An insert material made of austenitic stainless steel of the same quality as the joint material, or the same material as the groove joint material, and S (weight%), which is one of the chemical compositions, is higher than that of the groove joint material. By using an insert material containing 008 to 0.015%, not only can the effects of gaps and gaps that are likely to occur at the butt portion of the groove bottom portion be mitigated, but also on the back side, which is important in the first layer back wave welding The back bead width to be formed can be reliably formed in a convex shape. In particular, by using an insert material with a high S content, the arc shape is narrowed more than when welding with a normal insert material with a low S content, and convection of the molten metal in the depth direction is performed. Also, penetration is promoted, and a back bead can be easily formed on the back side under welding conditions with a welding current (or heat input) of about 10 to 20% less, and a substantially uniform back bead width is obtained with a convex shape without a dent. It is done. In addition, before the first layer backside welding, using a shallow penetration low heat input arc that does not melt to the back side and temporary attachment conditions without wire feed, the joint portion of the groove bottom portion on the surface side and the insert material By performing tack welding so that the projecting part of the weld is melt-bonded, the groove joint to be welded can be securely joined and fixed, and wire feed is facilitated during the first layer back wave welding of the main welding, and the back bead The adverse effect on formation can be eliminated. Then, after the tack welding is completed, the insert material and the joint projecting to the back side of the groove bottom are melted, and the back bead width on the back side is formed within a specific value range so that the back of the first layer is formed. By performing wave welding, it is possible to weld not only in the downward posture and the upwardly upward posture, which are relatively easy to perform reverse wave welding, but also in all posture welding of pipes that require advanced welding technology, welding in the horizontal posture of the pipe material, flat plate material Even in the upward-facing posture, it is possible to obtain a substantially uniform back bead width with a convex shape without a dent.

  In particular, in the construction of the first layer back wave welding, the first layer welding conditions of a heat input arc that can completely melt from the groove bottom on the front side to the back side are used, and one or more during pulse arc welding or DC arc welding. By adjusting or controlling the condition factor of the rear surface, the melt pool width on the back side or the back bead width in the vicinity of the melt pool is formed in a specific value range of 4 to 7 mm, preferably in the range of 4 to 6 mm. Even if the welder who operates the welding device changes, there is no effect of individual differences, and the target molten pool width and back bead width can be reliably formed within the appropriate range of the specific value on the back side, and a convex shape without dents Thus, a substantially uniform back bead width can be obtained satisfactorily. Condition factors to be adjusted or controlled include, for example, pulsed arc welding peak current, base current, peak voltage or average arc voltage or arc length, welding speed or travel speed, wire feed rate during peak current time or base current time Or the wire feed speed during both hours, and the average current, average arc voltage or arc length, welding speed or running speed, and wire feed speed of DC arc welding. Any one or more of the above-mentioned condition factors is adjusted so that the melt pool width on the back surface side or the back bead width in the vicinity of the melt pool is formed within a specified value range of 4 to 7 mm, preferably 4 to 6 mm. Alternatively, it may be controlled.

  Furthermore, in the welding construction that laminates from the welding of the remaining portion in the groove to be continued to the final layer welding of the groove upper surface portion, it is replaced with a martensite wire different from the austenite wire, or replaced with an inconel wire. It is used by exchanging with another austenitic wire having a linear expansion coefficient smaller than the linear expansion coefficient of the groove joint material, and the last welding condition when welding is performed using the austenitic wire before the welding operation. Alternatively, the non-consumable electrode method is used by changing to a welding condition having a heat input smaller than the last welding condition, or by reusing the last welding condition or a welding condition equivalent to the last welding condition. By performing pulse arc welding or direct current arc welding, as described above, martensitic transformation and expansion effects during the cooling process during welding The expansion agent and tension occurring in the weld metal laminated welded at martensitic wire with, it is possible to change the tensile stress remaining at the back of the weld portion and its vicinity of the bottom side to the compression stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. For example, the martensitic wire contains at least 8 to 12% by weight of Ni of chemical composition and 8 to 12% by weight of Cr, and has a martensitic transformation start temperature of 100 ° C. or higher and 300 ° C. or lower. A wire may be used. Further, instead of this martensitic stainless steel wire, the above-mentioned lamination welding is performed by replacing with another austenitic wire or inconel wire having a linear expansion coefficient smaller than that of the groove joint material, as described above. In addition, the shrinkage suppressing action and the tension due to the deviation of the linear expansion coefficient are generated in the weld metal portion, and the tensile stress remaining in the weld back surface portion on the bottom surface side and the vicinity thereof can be changed to a compressive stress or greatly reduced. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. In addition, by using welding conditions in which the heat input for each welding pass is suppressed to a small level, the weld metal part generated by welding for each pass and cumulative lamination welding and the area of shrinkage deformation, deflection deformation, and heat affected zone of this peripheral part can be reduced. Can be small.

  Hereinafter, the contents of the present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is an embodiment showing an outline of a multi-layer welding method for a narrow groove joint of the present invention. (1) is a state in which a non-consumable electrode and a wire are inserted into a narrow groove of a joint member. The groove cross section before welding, (2) is laminated welding from the groove bottom to a height Hb of about 3/5 of the plate thickness T using an austenitic wire, and then replaced with a martensitic wire. The weld cross section when laminating and welding from the part to the groove upper surface part, (3) is laminating and welding to a shallow height Hb of about ¼ of the plate thickness T using an austenitic wire, as in (2). It is a welding cross section when it replaces | exchanges for a martensite type wire after that and carries out lamination | stacking welding from the remaining deep part to a groove | channel upper surface part. The groove joint members 1 and 2 are containers and pipes that require multi-layer welding to form a back bead 15 on the groove back surfaces 1b and 2b and to be laminated up to the groove top surface on the groove surfaces 1a and 2a. It is a narrow groove joint obtained by abutting a thick plate member such as a guide tube or a thick plate member. In particular, it is a narrow groove joint made of austenitic stainless steel used in nuclear power plants, thermal power plants, chemical plants, etc., and is applied to the welded portion on the back side (back bead 15 portion) by multi-layer welding. It is important to change the residual stress to compressive stress.

As shown in FIG. 1 (1), a non-consumable electrode 6 and a wire to be melted by an arc 10 ignited at the tip of the electrode 6 are inserted into the groove 3 of the narrow groove joint members 1 and 2. Welding is performed. As this non-consumable electrode 6, for example, a commercially available round electrode rod having tungsten as a high melting point material such as W with La ₂ O _3, W with Y ₂ O _3, W with ThO ₂ may be used. . According to this welding test, a small-diameter round electrode 6 (for example, an electrode having an outer diameter of φ1.6 or φ2.4 can be inserted into the groove 3 without processing the flat width of the wide electrode with a narrow width). Even if only the tip of the rod is processed into a conical shape), an arc 10 generated between the tip of the round electrode 6 and the bottom of the groove is generated in the inside of the groove 3 in an atmosphere of shield gas inflow (not shown). The arc can be stably held in the portion of the groove bottom to be melted without rising to the wall surface side. A small round electrode that can be inserted into the groove 3 can be obtained at low cost, and the tip of the round electrode rod can be easily conical processed with a simple electrode grinder. Easy to install and remove and easy to use. Further, instead of the small-diameter round electrode 6, it corresponds to a non-consumable electrode in which the lateral width of the lower part of the large-diameter electrode is formed in a flat shape narrower than the groove width w, or a flat shape narrower than the groove width w. It is also possible to perform welding using other non-consumable electrodes having a non-circular cross-sectional shape. The flat electrode requires manufacturing costs for processing the width of the lower part of the large-diameter round electrode into a flat shape. However, just like the round electrode described above, only the electrode tip is easily conical with a simple electrode polisher. It can be processed and is easily attached to and detached from the welding torch.

  In the first layer back wave welding (back bead forming process) that requires the formation of the back bead, the initial layer conditions of the heat input arc that can be melted to the back side are output and opened as shown in FIGS. 1 (2) and (3). By constructing the back bead 15 so that the width of the back bead 15 is in the range of 4 to 7 mm, preferably in the range of 4 to 6 mm (5 ± 1 mm) on the back side of the front bottom part, the back wave welding is relatively easy. Not only for welding in a downward posture or an upwardly upward posture, but also for all posture welding of pipes that require advanced welding techniques, welding in the horizontal orientation of pipe materials, and welding in the upward orientation of flat plate materials A substantially uniform back bead width in shape can be obtained satisfactorily. The first layer back wave welding will be described in detail with reference to FIGS.

Further, until the cumulative laminated bead height Hb reaches a predetermined range from the groove back surfaces 1b and 2b, as shown in FIGS. 1 (2) and (3), the material of the groove joint members 1 and 2 ( For example, an austenitic wire (for example, an outer diameter of φ0.8 ~
φ1.2, SUS304, SUS308, or SUS316 commercially available wire) is melted in the groove 3 and laminated and welded one layer at a time. In addition, in the case of other austenitic stainless steels (for example, SUS309 series, SUS321 series, etc.) in which the material of the groove joint members 1 and 2 is different, a homogeneous austenitic wire suitable for the material of the joint member is used. That's fine.

  After the end of this lamination welding, replace with a martensitic wire having a martensitic transformation different from the austenitic wire, from the remaining welded portion in the groove 3 to the final layer (bead cross section 30) of the groove upper surface portion, The exchanged martensite wire is fed and melted to the arc welded portion in the groove so as to be laminated and welded one layer at a time. In this way, by laminating and welding in the second laminating welding process, the martensitic transformation and expansion effect by the martensitic wire causes expansion and tension in the weld metal part at room temperature, and the weld back surface on the groove bottom surface side. The tensile stress remaining in the portion and the vicinity thereof can be changed to a compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. The martensitic wire undergoes martensitic transformation in the cooling process during welding, and expands at a normal room temperature (for example, 20 ° C.) than at the start temperature of the martensitic transformation (for example, 100 to 300 ° C.). It is preferable to use a martensitic stainless wire which is a weld metal and has good fusion properties with the weld joint material of the austenitic stainless steel to be welded. For example, a martensitic stainless steel wire containing 8 to 12 wt% of Ni at least in chemical composition and 8 to 12 wt% of Cr and having a martensite transformation start temperature of 100 ° C or higher and 300 ° C or lower (the outer diameter is φ0. 8 to φ1.2 wire) may be used.

  Further, instead of the martensite wire, for example, the wire is replaced with an inconel wire or replaced with another austenite wire having a linear expansion coefficient smaller than that of the groove joint material. Is fed into the arc and in the melt pool (arc welding portion) formed immediately below the arc to melt, and the final layer welding of the groove upper surface portion is reached from the welding of the remaining portion in the groove to be continued. The non-consumable electrode type pulse arc welding or direct current arc welding may be performed so that the layers are laminated one by one in order. In this way, by laminating and welding in the second laminating welding process, shrinkage suppressing action and tension are generated in the weld metal part due to the deviation of the linear expansion coefficient, and the tensile stress remaining in the bottom side of the weld and the vicinity thereof is compressed. It can be changed to stress or greatly reduced. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced.

  Further, when performing non-consumable electrode type pulse arc welding, the pulse frequency at which the high peak current and the low base current to be output at every welding are alternately repeated is a minimum of 1 Hz, a maximum of 500 Hz, and preferably 150 Hz. One or more specific values to be used in the following ranges may be determined, or a plurality of different specific values may be determined in three roughly divided welding processes. A pulse arc of the determined pulse frequency is output for each welding, and the first layer back wave welding including tack welding is performed in the back bead forming step, and then a specific range of laminating is performed in the first laminating welding step. By performing laminating welding for laminating up to the bead height and performing laminating welding for laminating from the welding of the remaining portion in the groove to the final layer welding of the groove upper surface in the next second laminating welding process, From the first layer back wave welding to the final layer welding of the groove upper surface portion, it can be laminated and welded satisfactorily. Moreover, not only can a pulse arc of a target specific pulse frequency be output in a desired welding process and welding pass, but even if the average current is the same as the average current output in DC arc welding, the arc force and The directivity can be increased, and the melting and penetration depth of both wall surfaces and the groove bottom surface in the groove can be promoted. When the pulse frequency at the time of pulse arc welding is about 1 Hz (pulse period time: 1 s), for example, the welding bead ripple shape (wave like a shell pattern) is used in a velocity region where the welding speed is 90 mm / min or more. The eye) tends to become rougher than about 1.5 mm. On the other hand, when the pulse frequency is high at about 300 Hz and about 500 Hz, the pulse cycle time becomes extremely short, so when the power supply cable needs to be extended (for example, 10 times longer than 100 mm), this cable extension is accompanied. As the number of reactors increases, the rectangular peak current waveform changes to a trapezoidal shape or a triangular shape. Therefore, it is desirable to correct the peak current value to be slightly higher in advance. When the pulse frequency is lowered to about 150 Hz or less, for example, a substantially rectangular peak current waveform can be output even if the power feeding cable is extended to 100 m.

Further, the cumulative laminated bead height Hb to be welded using the austenitic wire is preferably in the range of 1/5 or more to 4/5 or less of the plate thickness T from the groove back surfaces 1b and 2b. Alternatively, the groove depth H remaining from the groove surfaces 1a and 2a can be in the range from 1/5 to 4/5 of the plate thickness T. If the cumulative laminated bead height Hb to be welded using the austenitic wire is too smaller than 1/5 of the plate thickness T or the remaining groove depth H is too large than 4/5 of the plate thickness T, This is not preferable because it may impair the corrosion resistance of the welded back surface exposed to a corrosive environment and prevent the progress of corrosion. The minimum value of the laminated bead height Hb varies depending on the thickness of the plate, but it is preferable to weld using an austenitic wire at least at the second weld bead height. On the other hand, if the cumulative laminated bead height Hb to be welded using the austenite wire is too larger than 4/5 of the plate thickness T or the remaining groove depth H is too small than 1/5 of the plate thickness T, After that, since there are too few parts to be laminated and welded to the final layer after replacing with the martensite wire, the expansion effect and tension generated in the weld metal part at room temperature are relatively lowered, and the farthest on the opposite side Further, it is not preferable because the tensile stress remaining in the weld back surface portion and the vicinity thereof cannot be changed to the compressive stress. In addition, in place of the martensite wire, inconel wire or other austenite wire having a linear expansion coefficient smaller than that of the groove joint material is used, the portion to be laminated and welded to the final layer is Since it will be too little, it is not preferable.

  FIG. 2 is another embodiment showing the outline of the multi-layer welding method of the narrow gap joint of the present invention. (1) uses an austenitic wire until the laminated bead height Hb in a specific range is reached. After being laminated and welded, the cross-section is obtained by exchanging with a martensitic wire different from the austenitic wire and using one layer and one pass for laminating and welding to the left and right as needed. (2) is a cross section when the final layer welding pass is increased to 3 passes and laminated welding is performed. Here, for example, from the groove bottom to a height Hb of about 3/5 of the plate thickness T, the austenitic wire homogeneous with the members 1 and 2 of the groove joint is melted in the groove 3 and laminated and welded. ing. After the lamination welding is completed, the martensitic wire having a martensitic transformation different from that of the austenitic wire is used for replacement, and the exchanged martensitic stainless wire is supplied to the arc welding portion in the groove. Then, as shown in FIGS. 2 (1) and 2 (2), the layers are welded one by one for each layer from the welding of the remaining portion in the groove to the final layer welding of the upper surface of the groove, or one layer and one pass. In the course of laminating one by one, the groove is distributed to the left and right as necessary and laminated and welded one by two, or the final layer is welded by increasing the number of welding passes to three.

  By laminating in this way, even if the wall surface has a groove width that is difficult to melt in one pass, both wall surfaces of the groove width can be reliably melted even under conditions where the heat input arc remains the same or slightly lower. And good welding results can be obtained up to the groove upper surface. Also, by performing pulse arc welding that alternately outputs a high peak current and a low base current, even if the average current is the same as the average current output by DC arc welding, the arc force and directivity can be increased, and the groove It is possible to promote the melting and penetration depth of the inner wall surfaces and the groove bottom surface. Further, as described above, the martensite transformation and expansion effect caused by the martensitic wire causes expansion and tension in the weld metal part at room temperature, and the tensile stress remaining in the weld back side on the groove bottom side and in the vicinity thereof. Can be changed to compressive stress, and at the same time, the tensile stress remaining in the weld surface portion of the final layer and the vicinity thereof can be reduced. Further, by increasing the number of welding passes of the final layer to 3 passes, the accumulated bead width of the final layer can be increased, and the tensile stress remaining on the weld surface portion of the final layer and in the vicinity thereof can be further reduced.

  FIG. 3 is another embodiment showing the outline of the multi-layer welding method of the narrow gap joint of the present invention. The main difference from FIG. 2 is that instead of the martensitic wire, Lamination welding is performed using an Inconel wire or another austenite wire having a linear expansion coefficient smaller than that of the groove joint material. That is, the exchanged Inconel wire or other austenite wire having a small coefficient of linear expansion is fed and melted to the arc welded portion 3 in the groove, as shown in FIGS. 3 (1) and (2), In the course of laminating one layer at a time, the layers are distributed to the left and right as necessary, and laminating and welding is performed until the final layer is welded by two layers per layer, or the final layer is welded by increasing the number of welding passes to three.

  By laminating and welding in this way, as described above, a shrinkage suppressing action and tension due to the deviation of the linear expansion coefficient occur in the weld metal part, and the tensile stress remaining on the bottom surface side of the weld and the vicinity thereof is converted to compressive stress. Can be changed or greatly reduced. At the same time, the tensile stress remaining in the weld surface portion of the final layer and in the vicinity thereof can be reduced. Moreover, even if the wall surface of the groove width becomes difficult to melt in one pass, as described above, both wall surfaces of the groove width can be reliably melted even under the condition that the heat input arc is kept under the same condition or a little lower, Good welding results can be obtained up to the groove upper surface. Furthermore, by increasing the number of welding passes of the final layer to 3 passes, the cumulative bead width of the final layer can be increased, and the tensile stress remaining on the weld surface portion of the final layer and in the vicinity thereof can be further reduced.

  FIG. 4 shows the temperature and elongation (1 mm length) of the martensitic wire used in the multi-layer welding method shown in FIGS. 1 and 2 and an austenitic wire (or a groove joint material of the same quality as this wire). It is explanatory drawing which shows typically the relationship with (elongation of hit). FIG. 5 schematically shows the relationship between the tension due to the expansion effect generated in the upper portion of the welded section laminated by martensitic wire and the compressive stress generated in the back surface portion of the welded section laminated by austenite wire. It is explanatory drawing. As shown in FIG. 4, in the case of an austenitic wire (or an austenitic stainless steel groove joint material), as shown by the dotted line, the elongation curve with respect to temperature change (during rising and falling) goes back and forth on the same line. Has changed. On the other hand, in the case of a martensitic wire having martensitic transformation, as shown by a solid line, the elongation curve at the time of temperature rise and the elongation curve at the time of temperature change are different. In particular, the martensitic transformation occurs in the process of lowering the temperature (cooling process from the high temperature region), and at the room temperature after cooling (about 20 ° C), the martensitic transformation starts to expand from the starting temperature Ms. Is shown.

  In the multi-layer welding method of the narrow groove joint of the present invention, lamination welding is performed by using two types of wires having different elongation curves with respect to temperature changes shown in FIG. That is, as shown in FIG. 5, the groove bottom side is laminated and welded using the austenitic wire, and thereafter, the martensitic wire having martensitic transformation is used to open from the remaining portion in the groove. Lamination welding is performed up to the final layer on the top surface. As described above, by laminating and welding two types of wires properly as described above, the martensitic transformation and expansion effect caused by the martensitic wire causes expansion and tension in the weld metal part at room temperature. The tensile stress remaining in the bottom surface side of the weld back surface and its vicinity can be changed to a compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and the vicinity thereof can be reduced. The martensitic wire is a martensitic stainless steel wire that has good fusion properties with the welded joint material of austenitic stainless steel, and as described above, at least 8 to 12% by weight of Ni having a chemical composition and 8% to Cr. A martensitic stainless wire (a wire having an outer diameter of φ0.8 to φ1.2) having a content of ˜12 wt% and a martensite transformation start temperature of 100 ° C. or higher and 300 ° C. or lower may be used. In place of the martensite wire, as described above, another austenite wire having a linear expansion coefficient smaller than that of the inconel wire or the groove joint material can be used.

FIG. 6 is a schematic configuration diagram showing an embodiment of a welding apparatus according to the multi-layer welding method for narrow gap joints of the present invention. The groove joint members 1 and 2 to be welded are pipe members such as containers, pipes and guide pipes made of thick austenitic stainless steel, and a back bead 15 is formed on the back side of the groove bottom.
There are narrow groove joints that require first layer backside welding with (complete penetration) and multi-layer welding up to the top of the groove. Moreover, the narrow groove joint of the flat plate member of a shape product different from the said pipe member may be sufficient. In the embodiment shown in FIG. 6, both the non-consumable electrode 6 mounted on the welding torch 7 (TIG torch) mounted on the welding carriage 5 traveling on the rail and the wire holder 25 for guiding the wire 4 are used. First layer backside welding that inserts into the groove 3 and feeds the wire 4 into the arc 10 and the molten pool generated in the inflow atmosphere of the shield gas 33 to form the back bead 15 on the back side of the groove bottom. It shows the situation of doing. As the shielding gas 33 flowing into the welded portion on the surface side, an inert pure Ar gas, a mixed gas containing Ar + several percent H ₂ , or a mixed gas containing Ar + several tens percent He may be used. When these mixed gases are used, the energy density and arc concentration are increased as compared with pure Ar gas, the molten state and penetration can be improved, and the welding speed can be increased.

  The TIG welding power source 8 is connected between the electrode 6 at the tip of the welding torch 7 and the groove joint members 1 and 2 and can be switched between pulse arc welding and DC arc welding by a switch for selecting a welding mode. It is a welding power source. When pulse arc welding is selected, the peak current, base current, arc voltage, and other conditions required for power supply for this pulse arc welding can be output arbitrarily, and the pulse frequency can be arbitrarily changed (for example, 1 Hz to 500 Hz at maximum). ) Is also possible. When DC arc welding different from pulse arc welding is selected, desired DC current and arc voltage (average arc voltage) corresponding to the welding current (average current) can be output.

  The welding control device 9a commands and controls the traveling of the welding cart 5 on which the welding torch 7 and the wire 4 are mounted, controls the output of the TIG welding power source 8, and controls the left and right and vertical positions of the welding torch 7 (electrode 6). If necessary, command control is performed, supply of the wire 4 to the tip of the electrode 6, adjustment of the left and right position and vertical position of the wire 4 as necessary, and deployment on the back side of the groove joint members 1 and 2 The back side monitoring device 17 is driven. The operation pendant 9b is connected to the welding control device 9a and incorporates welding condition adjusting means, torch position and wire position adjusting means. Control of the peak current during pulse arc welding and its peak current time, base current and its base current time, or time ratio of pulse frequency and peak current, and electrode height by means of welding condition adjusting means built in the operation pendant 9b Set the peak voltage or base voltage or average arc voltage used for (AVC control), peak wire feed and base wire feed, welding speed or running speed corresponding to this welding speed, or set these condition values It can be adjusted by interrupting during welding. Further, the position deviation of the welding torch 7 and the position deviation of the omitted wire 4 can be adjusted by the torch position and wire position adjusting means.

  In addition, when DC arc welding is selected, the welding condition adjusting means uses the average current to be output by DC arc welding, the average arc voltage or arc length used for electrode height control (AVC control), wire feed, and so on. Each condition value of speed, welding speed or traveling speed corresponding to this welding speed can be set, or these condition values can be interrupted and adjusted during welding. Similarly to the pulse arc welding, the position deviation of the welding torch 7 and the position deviation of the wire 4 can be adjusted by the torch position and wire position adjusting means. Further, the welding condition adjusting means incorporated in the operation pendant 9b includes a small heat input temporary attachment condition to be output by tack welding, an initial layer condition to be output by first layer back wave welding, a specific laminated bead height. It has a function that can set, memorize and reproduce multiple lamination conditions that should be output in the construction to be laminated welded, and then multiple lamination conditions to be outputted in the construction to be laminated welded up to the final layer on the groove upper surface. Yes. It may be a welding data file or other means having a function corresponding to this welding condition adjusting means. The operation pendant 9b also serves as a welding execution unit, and is based on the welding conditions for each layer or pass set in advance in the welding condition adjusting unit or a welding data file corresponding to the welding condition adjusting unit. Thus, tack welding, first layer back wave welding, and then second layer welding, third layer to the last layer of the groove upper surface portion can be performed in order. The procedure for laminating and welding to the final layer will be described with reference to FIG.

The welding cart 5 is provided with a second camera 35 for monitoring the welding state on the surface side in the upper middle between the welding torch 7 and the wire holder 25. An image of the welding state on the surface side imaged by the second camera 35 and the pair of camera controllers 36 is displayed on a second image monitor device 37 so as to be monitored. Other second video means and second video display means corresponding to the second camera 35 and the second video monitor device 37 may be used. On the screen of the second video monitor device 43, as shown in the lower left of FIG. 6, the electrode 6 and the wire 4, the arc 10 on the front side and the melted surface inserted into the groove 3 from the groove surfaces 1a and 2a side. The state of the weld bead on the front side formed behind the pool 18, the molten pool 18 and the electrode 6 is displayed. By adjusting or controlling the position of the electrode 6 or the position of the electrode 6 and the position of the wire 4 based on the monitoring result of the welding state on the surface side displayed on the screen of the second video monitor device 37, the position shift of the electrode 6 ( For example, it is possible to eliminate the positional deviation of the electrode in the left and right direction and the positional deviation of the wire 4 (for example, the positional deviation of the wire in the horizontal direction and the vertical direction). Moreover, the factor of welding conditions can also be adjusted or controlled.

  On the other hand, a back side monitoring device 17 is provided on the back side of the groove joint members 1 and 2. The back side monitoring device 17 includes a back side melt pool 16 and a first camera 11 that images the periphery thereof, illumination means 32 (for example, a small-diameter illumination lamp) that illuminates the imaging periphery, and the back side melt. A gas outflow box for supplying a back shield gas 34 (for example, Ar gas) for protecting the pool 16 and the back bead 15 in the peripheral portion is provided. Further, as shown in the lower right part of FIG. 6, the first video monitor device 13 is a back surface imaged by a camera controller 12 and a pair of the first camera 11 or imaging means corresponding to the first camera 11. The image of the molten pool 16 on the side and the peripheral portion is displayed on the screen in real time. At the same time, the size of this image or the size indicating the melt pool width or the back bead width B in the vicinity of the melt pool, and the specific range indicating the appropriate range of the melt pool width or back bead width on the back side to be formed in the first layer back wave welding The value 14 is displayed on the screen of the first video monitor device 13. The first video monitor device 13 may be other video display means corresponding to this. The appropriate range for specifying the melt pool width or back bead width on the back side is 4 to 7 mm, preferably about 4 to 6 mm (or about 5 ± 1 mm). The drawing line (dotted line) or the dimension arrow is displayed on the screen in a monitorable state.

  Thus, by directly displaying on the screen of the first video monitor device 13 or the screen of the first video display means corresponding to the first video monitor device 13, the back surface important in the first layer back wave welding is obtained. Monitoring and observing the formation state and size of the molten pool and back bead on the side, the molten state of the insert 19 protruding on the back side, and the back bead width B of a specific value as images, and the back bead width during welding is appropriate It can be easily determined whether or not it is formed in the range. In particular, the appropriate range of the melt pool width on the back surface side or the back bead width B in the vicinity of the melt pool is specified to be about 4 to 6 mm, and this specific value is directly color-coded and displayed on the screen of the first video monitor device 13. And clearly monitorable. Thereafter, welding is performed to operate the welding apparatus by outputting the initial layer welding conditions and performing the pulse arc welding or DC arc welding so that the back bead width B on the back surface side is formed within an appropriate range of the specific value. Even if the person changes, the influence of individual differences disappears, the target melt pool width and back bead width can be reliably formed in the proper range on the back side, and a substantially uniform back bead width is obtained with a convex shape without a dent. be able to.

  Further, the image processing apparatus 38 processes the image of the molten pool 16 including the insert material 19 on the back surface side and the peripheral portion thereof, and the width B of the molten pool 16 on the back surface side or the width of the back bead 15 in the vicinity of the molten pool 16. B is detected in real time, and the width C of the insert material is also detected. Other detection processing means corresponding to the image processing device 38 may be used. The detection data transmitted in real time to the welding control apparatus 9a side sequentially performs a process of averaging a plurality of values in the welding control apparatus 9a, and compares the averaged detection value with the target specific value. Judgment processing. And based on the result of this determination process, the molten pool B width on the back surface side or the back bead width B near the molten pool is formed within an appropriate range of a specific value (a range of about 4 to 6 mm or about 5 ± 1 mm). As described above, any one or more condition factors of peak current, base current, peak voltage or average arc voltage or arc length, welding speed or running speed of pulse arc welding, or in addition to the above condition factors, during peak current time Any one or more condition factors including the value of the wire feed rate during the base current time or the value of the wire feed rate during both times are controlled to increase or decrease. In the case of DC arc welding, one or more condition factors of average current, average arc voltage or arc length, welding speed or traveling speed, and wire feed speed are controlled to increase or decrease.

For example, if the detection value Bs of the melt pool width on the back surface side detected by the image processing device 38 is smaller than the appropriate range of the specific value (Bs <B1 = 4 mm), the peak current Ip (pulse arc welding Or the average current Ia (during DC arc welding) is increased (Ip + ΔI or Ia + ΔI). On the other hand, if the detected value Bs of the molten pool width is larger than the appropriate range of the specific value (Bs> B2 = 6 mm), the peak current (when using pulse arc welding) or the average current (when using DC arc welding) ) May be decreased (Ip−ΔI or Ia−ΔI). If the detected value Bs of the molten pool width is in a state within an appropriate range (for example, B1 = 4 ≦ Bs ≦ B2 = 6 mm), it is preferable to keep the welding condition during output as it is.

  In this way, by appropriately increasing / decreasing the condition factor based on the determination result of the detected value, the molten pool width and the back bead width in the vicinity of the molten pool can be reduced within an appropriate range for a short time by increasing / decreasing the arc force and heat input. Can be recovered. Also, by controlling the peak voltage, average arc voltage, or wire feed rate at the same time as increasing / decreasing peak current or base current (during pulse arc welding) and average current (during DC arc welding), the back side Thus, the target melt pool width and back bead width can be reliably formed within an appropriate range. Further, the adjustment or increase / decrease control of the one or more conditional factors is performed, and the position of the electrode 6 or the position of the electrode and the position of the wire 4 are adjusted or controlled based on the monitoring result of the welding state on the surface side. In addition to eliminating misalignment of the electrode 6 (eg, misalignment of the electrode in the left-right direction) and misalignment of the wire 4, it is possible not only to form a good back bead width without meandering and poor fusion within an appropriate range of specific values, This can greatly reduce the burden of welding and improve welding quality and productivity.

  Fig. 7 shows the outline of the welding operation of the narrow groove joint. (1) is a cross section before welding, (2) is a cross section when tack welding is performed before main welding, and (3) is main welding. Cross section when first layer back wave welding is performed in the first pass, (4) is a cross section when welding to the second pass using the austenitic wire of the same type as the material of the joint member, and (5) is the total number of laminated layers A cross-section when lamination welding is performed until the bead height Hb reaches about 2/5 of the plate thickness T, (6) shows the remaining welded portion in the groove using a martensite wire different from the austenite wire It is a cross section when carrying out lamination welding from the last layer of a groove | channel upper surface part. As described above, the groove joint members 1, 2 are made of thick plate austenitic stainless steel used in nuclear power plants or thermal power plants, pipe members such as pipes and guide tubes, or flat plate members. There are narrow groove joints that are welded products and require welding to be laminated from the first layer back surface welding of the groove bottom portion to the groove upper surface portion, and the compressive stress of the tensile stress remaining in the welded portion or a significant reduction.

  In an example of this narrow groove joint, as shown in FIG. 7 (1), an insert material 19 is provided at the center of the groove bottom so as to protrude from the front side 1a, 2a and the back side 1b, 2b. The insert material 19 is an austenitic stainless steel material of the same quality as the material of the groove joint members 1 and 2. By providing this insert material, not only can the back bead width B in the proper range (about 4 to 6 mm) be formed in a convex shape on the back surface side, but also the step and gap that are likely to occur at the butted portion of the groove bottom. Impact can be mitigated. The insert material 19 is the same material as the groove joint material, and contains 0.008 to 0.015% of S (weight%), which is one of the chemical compositions, higher than the groove joint material. The insert material 19 is preferably used. In particular, by using the insert material 19 having a high S content, the arc shape is narrowed and melted in the depth direction, compared to welding using a normal insert material 19 having a low S content. The convection and penetration of metal are promoted, and the back bead 15 can be reliably formed on the back side under welding conditions with a welding current (or heat input amount) of about 10 to 20% less, and the back bead width is almost uniform with a convex shape without a dent. Can be obtained. In addition, it is not preferable that the content of S (% by weight) exceeds 0.015% because the sensitivity to weld cracking increases.

On the other hand, the groove width w of the groove bottom portion including the width of the insert material 19 is shown here as an example where the groove width is set to about 6 mm. For example, the minimum value is about 4 mm or about 5 mm, or a little wider about 7 mm. Alternatively, it may be preliminarily formed to have a maximum dimension of approximately 8 mm or a dimension including a decimal point close to these approximate dimensions (for example, approximately 5.3 mm, 6.4 mm, 7.5 mm, etc.). At the same time, the one-sided angle θ up to the top of the narrow groove joint is formed to be 10 ° or less (for example, formed to about 2.5 °, about 5 °, about 7.5 °, about 10 °). It is possible to reliably perform multilayer overlay welding in which narrow gaps 3 are stacked one layer at a time up to the top of the front surfaces 1a and 2a. In addition, the heat input per welding pass, the cumulative heat input of multi-layer welding, and shrinkage deformation due to welding heat can be greatly reduced compared to conventional welding, and the groove cross-sectional area to be welded can be reduced, and the amount of wire used can be reduced. Reduction and welding man-hours can also be reduced. Note that it is possible to perform multi-layer welding of the groove joint with the wide one-side angle θ, but as the plate thickness T or the groove depth increases, the groove cross-sectional area A to be welded increases (A = H ² * tanθ + H * w), the number of welding passes, the welding work time, the cumulative heat input and shrinkage deformation also increase. In order to suppress this, the one-sided angle θ is limited to 10 ° or less. The root face f at the bottom of the groove can be easily melted to the back side by forming it in the range of about 1 to 2.5 mm, preferably about 1.5 mm.

  According to this experiment, if the groove width w of the groove bottom portion including the width of the insert material 19 is formed to be less than 4 mm, it is too narrow, so the outer surface of the electrode 6 inserted into the groove and the groove inner 3 The gap with the wall surface is extremely narrow, and the entire groove width shrinks due to the heat shrinkage caused by the first layer welding and the subsequent welding, and the contact of the electrode 6 to the groove wall surface and the occurrence of arcing easily occur. It becomes difficult to laminate welding. On the other hand, when the groove width w of the groove bottom exceeds 8 mm, it is too wide, so that the number of welding passes and the amount of wire used increase as the groove area increases, resulting in an increase in the number of welding processes. Therefore, as described above, the groove width w is preferably 4 mm or more at the minimum and 8 mm or less at the maximum. In addition, when it becomes difficult on the way to weld one layer at a time, as shown in FIG. 2 and FIG. Both wall surfaces in the groove can be reliably melted, and good welding results can be obtained up to the groove upper surface. Furthermore, by increasing the number of welding passes of the final layer to 3 passes, the cumulative bead width of the final layer can be increased, and the tensile stress remaining on the weld surface portion of the final layer and in the vicinity thereof can be further reduced.

  In the tack welding performed before the first layer back wave welding of the main welding, as shown in FIG. 7 (2), the joint portion on the back surface side of the groove joint members 1 and 2 and the protruding portion of the insert material 19 are not melted. The wire 4 feed is performed so as to output a shallow penetration low heat input arc and a temporary attachment condition without wire feed so as to melt-join the joint portion of the groove bottom portion and the protruding portion of the insert material 19 from the surface side 1a, 2a. It is good to perform tack welding without. By performing tack welding in this manner, a shallow penetration weld bead that does not melt to the back surface side can be well formed on the groove bottom, and the groove joint to be welded can be reliably bonded and fixed. In addition, wire feeding can be facilitated during the first layer backside welding of the main welding, and adverse effects on the back bead formation can be eliminated.

  Then, in the first layer back wave welding in which the back bead 15 needs to be formed in the main welding, the first layer condition of the heat input arc to be melted to the back side is output, and as shown in FIG. While melting so as to melt, the width of the molten pool or the width B of the back bead 15 in the vicinity of the molten pool is formed in a range of about 4 to 6 mm (or a range of about 5 ± 1 mm) of a specific value. For example, in the case of pulse arc welding, an image showing the state and size of the melt pool 16 on the back surface and the back bead 15 near the melt pool displayed on the first image monitor device 13 shown in FIG. The specific value indicating the appropriate range of the target back bead width B is monitored, and the peak current, base current, peak voltage or average is adjusted as necessary so that the back bead width during welding is formed within the range of the specific value. Adjusting or controlling any one or more of the condition factors including the value of arc voltage or arc length, welding speed or running speed, wire feed rate during peak current time or base current time, or wire feed rate during both times Good. A small amount of wire feed during the initial layer welding (for example, less than half that during lamination welding) is sufficient. In the case of DC arc welding, the average current, the average arc voltage or arc length, the welding speed or traveling speed, the wire feed speed, if necessary, so that the same back bead width is formed in the range of the specific value. Any one or more of the condition factors may be adjusted or controlled.

  For example, if the molten pool width or the back bead width is smaller or larger than the appropriate range of the specific value, the peak current (at the time of pulse arc welding) and the average current (at the time of DC arc welding) are adjusted to increase or decrease. By adjusting the arc force and heat input, the molten pool width and the back bead width near the molten pool can be restored to the appropriate range in a short time, which is superior to adjusting the welding speed or running speed with a responsive response. is there. Next to the peak current and the average current, the increase / decrease adjustment of the base current or the adjustment of the arc length or the arc voltage is effective, and the back bead width is restored within an appropriate range. Further, the adjustment of the wire feed speed can finely adjust both the back bead width and the bead height on the surface side by increasing / decreasing the weld metal and changing the temperature of the molten pool. Further, the position of the electrode 6 on the surface side or the position of the electrode and the position of the wire 4 may be adjusted or controlled.

  According to this experiment, for example, when the melt pool width on the back surface side is about 2.5 mm or less, the back bead is formed or not formed, and it becomes an extremely unstable state. Insufficient (no back bead) defect welding results. On the other hand, when the melt pool width on the back side exceeds 7.5 mm, the back bead shape in the downward posture rises to a convex shape of 1 mm or more (the shape that sinks downward), on the contrary, in the upward posture As a result, the back bead shape was recessed by about 1 mm, and the back bead on the back side changed to an uneven shape due to the difference in welding position. Furthermore, when the molten pool width on the back side exceeded about 9 mm, it led to defect welding that melted down. Therefore, as described above, the melt pool width and back bead width on the back side are specified in the range of 4 to 7 mm, preferably in the range of 4 to 6 mm (5 ± 1 mm). In order to obtain an almost uniform back bead.

  Thus, by performing the pulse arc welding or the direct current arc welding so that the melt pool width and the back bead width on the back surface side are formed within the appropriate range of the specific value, the welder operating the welding apparatus is replaced. Even if there is no influence of individual differences, the target melt pool width and back bead width can be reliably formed within the appropriate range of the specified value on the back side, and a substantially uniform back bead width is achieved with a convex shape without a dent. Obtainable. In particular, it is suitable for all-position welding of pipes that require advanced welding techniques, welding in the horizontal orientation of pipe materials, and first layer back-wave welding in the upward orientation of flat plates. Further, the one or more condition values are adjusted or controlled, and the position of the electrode 6 on the front surface side or the position of the electrode 6 and the position of the wire 4 are adjusted or controlled to thereby adjust the position of the electrode 6 (for example, in the left-right direction). Electrode position deviation) and wire 4 position deviation can be eliminated, and a good back bead width without meandering or poor fusion can be formed within an appropriate range of a specific value. Although a small amount of wire feed is shown here, it is also possible to stop the wire feed (no wire) and perform first layer backside welding. Further, here, the welding example in which the insert material 19 is provided at the center of the groove bottom portion of the groove joint members 1 and 2 is shown. However, even in the case of a groove joint without the insert material 19, for example, a downward posture or a standing up If the first layer back wave welding is performed in an advanced posture, the target melt pool width and back bead width can be formed in the appropriate range on the back side, and it is possible to obtain a substantially uniform back bead width with a convex shape. is there. Next, in the second layer welding performed after the first layer back wave welding is completed, an austenitic wire is used, and at least the back bead 15 formed at the time of the first layer welding is reused as shown in FIG. Change to welding conditions that are suppressed to heat input conditions that do not melt (for example, heat input conditions that are 1/2 to 2/3 of the first layer welding conditions), and perform non-consumable pulse arc welding or DC arc welding. I have to. Thus, by suppressing the heat input of the second layer welding and performing welding, remelting of the back bead can be surely prevented, and the height of the beads stacked on the surface side can be increased. In addition, in the welding construction in which the accumulated laminated bead height Hb reaches after the third layer welding, as shown in FIG. 7 (5), at least the first layer welding condition, the second layer welding condition, Change to a plurality of appropriate welding conditions (for example, low heat input conditions of 4 kJ / cm to 12 kJ / cm or arc conditions of an average welding current of about 120 A to 220 A) which are different lamination conditions and correspond to the welding pass. The non-consumable electrode type pulse arc welding or direct current arc welding is performed so as to carry out layer welding one layer at a time. Or, laminar welding is performed by setting the welding conditions to be substantially constant (for example, low heat input conditions specified at about 4 kJ / cm, about 6 kJ / cm, about 8 kJ / cm, about 10 kJ / cm, or about 12 kJ / cm). Thus, the non-consumable electrode type pulse arc welding or DC arc welding can also be performed. The wire feed amount is a meltable wire amount suitable for the heat-injection conditions. For example, the wire feed amount may be fed so that the bead height to be formed is in the range of 0.5 to 2.0 mm. Further, during welding, the position of the electrode 6 or the position of the electrode 6 and the position of the wire 4 are adjusted or controlled based on the monitoring result of the welding state on the surface side displayed on the second video monitor device 37 shown in FIG. Good. Thus, by performing the 1st lamination welding, it can be filled with the weld metal by the austenite type wire from the groove back to predetermined lamination bead height Hb.

  Then, in the welding construction in which the groove is laminated up to the final layer on the upper surface of the groove, the wire is replaced with a martensitic wire having martensitic transformation, and as shown in FIG. From the welded portion 26 to the final layer on the groove upper surface, lamination welding is performed one layer at a time. Further, as shown in FIG. 2, it is possible to perform lamination welding by one layer and two passes by distributing the groove left and right in the course of laminating one layer and one pass. Furthermore, by increasing the number of welding passes of the final layer to 3 passes, the cumulative bead width of the final layer can be increased, and the tensile stress remaining on the weld surface portion of the final layer and in the vicinity thereof can be further reduced.

  In laminate welding using martensite wire, the last welding condition when laminate welding was performed using austenite wire before this lamination welding, or appropriate welding conditions with a smaller heat input than this last welding condition By welding with changing to, it is possible not only to obtain a good welding result up to the groove upper surface portion, but also to reduce the shrinkage deformation, deflection deformation, and heat affected zone region due to welding. Alternatively, by reusing and welding the last welding condition or an appropriate welding condition equivalent to the last welding condition, it is possible to stack with a small number of passes and obtain a good welding result up to the groove upper surface. Can do. In the final layer welding (P = N), as shown in FIG. 7 (6), it is finished so that it slightly rises above the groove surfaces 1a and 2a (for example, an extra height of about 1 mm). In the final layer welding or the previous layer welding and the final layer welding, weaving welding in which the welding torch 4 is swung left and right may be performed. By this weaving welding, it is possible to improve the penetration of both toe ends of the weld bead and to obtain a good weld bead appearance having a wave pattern like a shell pattern.

  In this way, two types of wires are properly used and each is laminated and welded, so that complete penetration welding of pipe members such as thick plate containers and pipes used in nuclear power plants and thermal power plants, and groove joints of flat plate members In addition, it is possible not only to obtain a good welding result without defects from the groove back surface portion to the groove top surface portion even in a welded product that requires a reduction in residual stress. Due to the martensitic transformation and expansion effect caused by the above, expansion action and tension are generated in the weld metal portion at room temperature, and the stress remaining in the weld back surface portion near the groove bottom surface side and the vicinity thereof can be improved to compressive stress. At the same time, the tensile stress remaining in the weld surface portion of the final layer and the vicinity thereof can be reduced. In addition, by using welding conditions in which the heat input for each welding pass is suppressed to a small level, the weld metal part generated by welding for each pass and cumulative lamination welding and the area of shrinkage deformation, deflection deformation, and heat affected zone of this peripheral part can be reduced. Can be small. In addition, as a result of conducting a tensile strength test and a bending strength test of the welded joint, it was a good result having a higher strength than the base material due to the base material fracture and a ductile strength without micro cracks.

Finally, the measurement results of residual stress will be described. FIG. 8 is an example of a measurement result of residual stress on the inner surface of a pipe, which is one of the multi-layered welded structures constructed by the multi-pass welding method for the narrow groove joint of the present invention. Similarly, FIG. 9 is an example of a residual stress measurement result on the outer surface of a pipe that is one of the multi-layer welded structures. The material of the pipe is SUS316L, the outer diameter is 314 mm, the plate thickness is 29.5 mm, and the groove depth is 28 mm. As shown in FIG. 1 (3) and FIG. 7, the welding work is performed using austenite wire (SUS316L system) of the same quality as the piping, and a shallow height of about 2/5 of the groove plate thickness T. Lamination welding is then performed, and then, martensitic stainless wire having martensitic transformation is exchanged and lamination welding is performed under low heat input conditions from the remaining deep portion to the groove upper surface portion. In addition, the residual stress measurement is more accurate than the X-ray diffraction measurement method (the strain gauge opening method (a strain gauge is attached to the measurement location on the inner and outer surfaces of the pipe, and the process of stripping the primary cut to the final slit cutting) This is a result of measurement using the opening step, calculating the circumferential residual stress σθ and the axial residual stress from the measurement result of the circumferential opening strain value εθ and the axial opening strain value εz. .

  As shown in FIG. 8, the residual stress at the weld back surface on the inner surface side of the pipe and its peripheral portion is the axial residual stress σz in the direction perpendicular to the weld line (circled line) and the circumferential residual stress σθ in the weld line direction. Both (the lines marked with ◆) have a compressive stress of about −100 MPa or less. On the other hand, as shown in FIG. 9, the circumferential residual stress σθ (line marked with ◆) in the portion adjacent to the welded portion is about 170 MPa at the maximum, as shown in FIG. Tensile stress. On the other hand, the axial residual stress σz in the direction perpendicular to the weld line (circled line) is a compressive stress of about −100 MPa in the portion adjacent to the weld and the center of the weld.

  For comparison, FIG. 10 shows an example of a residual stress measurement result on the inner surface of a pipe welded using the austenitic wire from the first layer backside welding to the final layer welding. The piping material and size, groove shape, welding conditions and welding method are almost the same, and only martensitic wire is used and only austenitic wire of the same quality as groove joint material is used. Is different. In this case, while the circumferential residual stress σθ is a compressive stress of about −100 MPa or less, the important axial residual stress σz changes to a tensile stress of about 100 MPa at the maximum. By reducing the groove width of the groove joint and performing lamination welding under low heat input welding conditions, it is possible to reduce the residual stress at the important weld back surface and its peripheral part, as shown in FIG. A maximum tensile stress of about 100 MPa remains. On the other hand, by applying the multi-layer welding method of the present invention, as shown in FIG. 8, the residual stress at the important welding back surface portion and its peripheral portion can be improved to compressive stress. As a result of this improvement, it is not necessary to provide an expensive heat treatment apparatus for removing residual stress or perform heat treatment after the completion of welding, and cost can be reduced.

  As described above, according to the multi-layer prime welding method of the narrow groove joint of the present invention, the pipe joint or the flat plate member such as the thick plate container or the pipe which requires the multi-layer prime welding of the groove joint and the residual stress reduction. Even if it exists, lamination welding can be favorably performed from the groove bottom portion to the final layer welding of the groove upper surface portion from the initial layer backside welding. Also, by laminating and welding two types of austenitic wire and martensite separately, expansion action and tension are generated in the weld metal part of the martensite transformation, and tensile stress remaining in the bottom side of the weld back surface and in the vicinity thereof is generated. The compressive stress can be changed, and at the same time, the tensile stress remaining on the weld surface portion of the final layer and in the vicinity thereof can be reduced. In addition, not only can the heat input per welding pass, shrinkage deformation or deflection deformation due to welding, and the heat affected zone be reduced, but the groove cross-sectional area to be welded can be reduced, reducing the amount of wire used and reducing the number of welding processes. Reduction can be achieved. Furthermore, as a result of improving the residual stress, it is not necessary to provide an expensive heat treatment apparatus for removing the residual stress after the completion of welding, or to perform the heat treatment, and not only can the cost be reduced, This contributes to the prevention of residual stress corrosion cracking and the extension of service life when operating in actual equipment such as nuclear power plants.

It is a welding cross section of one Example which shows the outline | summary of the multilayer pile welding method of the narrow groove joint of this invention. It is a welding cross section of another Example which shows the outline | summary of the multilayer pile welding method of the narrow gap joint of this invention. It is a welding cross section of another one Example which shows the outline | summary of the multilayer pile welding method of the narrow gap joint of this invention. Temperature and elongation (elongation per 1 mm length) of martensitic wire and austenitic wire (or a groove joint material of the same quality as this wire) used in the multi-layer welding method shown in FIGS. It is explanatory drawing which shows typically the relationship. It is explanatory drawing which shows typically the relationship between the tension | tensile_strength by the expansion | swelling effect which arises in the upper part of the weld cross section welded by the martensitic wire, and the compressive stress which arises in the back surface part of the weld cross section welded by the austenitic wire. It is a schematic block diagram which shows one implementation of the welding apparatus concerning the multi-layer welding method of the narrow groove joint of this invention. It is a section before welding and after lamination welding which shows the outline of welding construction of a narrow gap joint. It is an example of the residual stress measurement result of the piping inner surface which is one of the multilayer prime-welded structures constructed with the multilayer prime welding method of the narrow groove joint of the present invention. It is an example of the residual stress measurement result of the pipe outer surface which is one of the multilayer weld structures constructed by the multilayer prime welding method of the narrow groove joint of the present invention. It is an example of the residual stress measurement result of the inner surface of the pipe welded using the austenitic wire from the first layer backside welding to the final layer welding.

Explanation of symbols

1, 2 ... groove joint member, 1b, 2b ... groove back surface, 3 ... inside groove, 4 ... wire, 5 ... welding carriage, 6 ... electrode, 7 ... welding torch, 8 ... TIG welding power source, 9a ... welding Control device, 9b ... operation pendant, 10 ... arc, 11 ... first camera, 12 ... camera controller, 13 ... first video monitor device, 14 ... specific value of back bead width B, 15 ... back bead, 16 DESCRIPTION OF SYMBOLS ... Melting pool of back side, 17 ... Monitoring apparatus of back side, 18 ... Molten pool of surface side, 19 ... Insert material, 20 ... Bead cross section of tack welding, 21 ... Bead cross section of first layer back wave welding, 22 ... 2 Bead cross section of pass weld, 23 ... Bead cross section of third pass weld, 30 ... Bead cross section of final layer, 32 ... Illuminating means, 33 ... Shield gas, 34 ... Back gas, 35 ... Second camera, 36 ... Camera Controller,
37 ... second image monitor device, 38 ... image processing device, 39 ... surface side molten pool, 41 ... lamination welding with austenitic wire, 42 ... lamination welding with martensite wire, Hb ... total laminated bead height , H: remaining groove depth, w: groove bottom width, f: root face, θ: single-sided angle.

Claims (7)

In the multi-layer prime welding method for narrow groove joints in which the groove formed by mutually abutting tube members or flat plate members is laminated and welded from one side,
The first welding step is performed by using the same kind of wire as the pipe member or the flat plate member in the range of 1/5 to 4/5 of the member thickness from the start of the lamination welding, and the first welding. And a second welding step using a wire having a smaller linear expansion coefficient than the tube member or flat plate member in a range from the remaining portion to the final weld layer after the step.   2. The multi-layer welding method according to claim 1, wherein the first welding step or the second welding step is performed by non-consumable electrode type pulse arc welding or DC arc welding. Welding method. The multilayer overlay welding method according to claim 1,
A multi-layer welding method, wherein a groove width of a bottom portion of the narrow groove is 4 mm or more and 8 mm or less, and an angle of one side of a member forming the groove is 10 ° or less. The multilayer overlay welding method according to claim 1,
A multilayer overlay welding method comprising providing an austenitic insert material containing 0.008 to 0.15% of a sulfur content at the center of the bottom of the narrow groove joint so as to protrude from the front side and the back side, respectively. The multilayer overlay welding method according to claim 1,
The wire used in the first welding process is an austenitic wire,
The multi-layer welding method, wherein the wire used in the second welding step is one of a martensite wire, an inconel wire, and an austenite wire. The multilayer overlay welding method according to claim 1,
The wire used in the first welding process is an austenitic wire,
The wire used in the second welding process is a martensitic wire,
The martensitic wire uses a wire containing 8 to 12 wt% of Ni and 8 to 12 wt% of Cr and having a martensite transformation start temperature of 100 ° C to 300 ° C. . In the multilayer overlay welding method according to claim 4,
A multi-layer prime welding method for narrow groove joints, comprising a tack welding step in which a joint portion on a surface side of the groove bottom portion and a protruding portion of the insert material are melt-bonded before the first welding step. .

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