JP2008087044A - Flux-cored wire for titania gas-shielded arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flux-cored wire for gas-shielded arc welding which is free from any drop of molten metal even when a root gap is wide in the vertical upward welding, excellent in welding work efficiency, excellent in mechanical properties of a weld metal, and suitable for welding in all attitudes. <P>SOLUTION: The flux-cored wire contains, by mass, 6-12% TiO<SB>2</SB>, 0.4-0.8% Al<SB>2</SB>O<SB>3</SB>, 0.1-0.5% SiO<SB>2</SB>, 0.05-0.2% ZrO<SB>2</SB>, 1.0-3.0% Mn, 0.4-0.9% Si, 0.1-0.3% Al, 0.4-0.8% Mg based on the total mass of the wire, and further, as necessary, C, F, Cr, Cu, Ni, V, Nb, Ti and/or Zr, and the balance Fe with impurities, where (TiO<SB>2</SB>+Al<SB>2</SB>O<SB>3</SB>)/(SiO<SB>2</SB>+ZrO<SB>2</SB>): 10-20, Mg/(Si+Al): 0.4-0.7, Na+K: 0.05-0.12, and Na/K: ≥0.3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flux-cored wire for titania-based gas shielded arc welding that can be applied to welding mild steel, high-strength steel, low-alloy steel, and the like. The present invention relates to a flux-cored wire for titania-based gas shielded arc welding with improved welding workability such as quantity and mechanical performance of weld metal.

  In shipyards, the development of automated welding and high efficiency is being promoted in order to promote labor saving and high efficiency in welding work, which accounts for about 30% of the process. In particular, for downward butt welding and horizontal fillet welding, a welding robot, a line welder, and the like have been introduced, and a large number of dedicated welding materials have been developed. On the other hand, with regard to the vertical-advanced welding position, which is mainly used for block joints in shipbuilding, automation is not possible because the applicable welding location is narrow and the structure cannot be reversed. Since it is not advanced and a very high level of welding skill is required, it is very difficult to improve the efficiency and defeat.

On the other hand, Patent Document 1 proposes a flux-cored wire capable of standing-up advance welding with a high current by containing a large amount of Al ₂ O ₃ , MgO, and ZrO ₂ as essential components (conventionally). Technology 1). Further, Patent Document 2 proposes a flux-cored wire for titania arc welding suitable for all-position welding by further improving the stand-up improvement while maintaining workability and weld metal performance in all-position welding. (Prior art 2). Further, Patent Document 3 proposes a flux-cored wire that is similarly excellent in stand-up advanceability and good in low-temperature toughness of the weld metal (Prior Art 3).

JP-A-8-99192 JP2004-34078 JP 2005-319508 A

  However, in the above-described prior art, when the root interval is wide in the case of rising fillet welding, due to insufficient viscosity of the slag and the molten metal itself, the molten metal tends to sag and the bead shape becomes poor. This does not take into account the poor groove accuracy of structures in actual shipbuilding and the like, and the applicable condition range is extremely narrow. Further, the conventional technique 1 has a problem that the slag peelability is not good, and the conventional technique 2 has a problem that the amount of spatter generated is still large. As described above, the conventional flux-cored wire has a problem in the vertical improvement weldability, and thus cannot be effectively used for all-position welding.

  The present invention has been made in view of such problems, and there is no dripping of molten metal even under severe welding conditions such as a wide root gap in vertical welding, and slag removability is good and sputtering is performed. An object of the present invention is to provide a flux-cored wire for titania-based gas shielded arc welding suitable for all-position welding, which has good welding workability with a small amount of generation and excellent mechanical properties of the weld metal.

The flux-cored wire for titania-based gas shielded arc welding according to the present invention is a flux-cored wire for titania-based gas shielded arc welding formed by filling a soft steel or alloy steel sheath with a flux. Per mass,
TiO ₂ : 6 to 12% by mass,
Al ₂ O ₃ : 0.4 to 0.8% by mass,
SiO ₂ : 0.1 to 0.5% by mass,
ZrO ₂ : 0.05 to 0.20 mass%,
Mn: 1.0 to 3.0% by mass,
Si: 0.4 to 0.9 mass%,
Al: 0.1 to 0.3% by mass,
Mg: 0.4 to 0.8% by mass,
Containing
The balance is Fe and inevitable impurities,
(TiO ₂ + Al ₂ O ₃ ) / (SiO ₂ + ZrO ₂ ): 10 to 20,
Mg / (Si + Al): 0.4 to 0.7 (when Mg and Si and Al are present in the form of an alloy, the content in terms of Mg, Si and Al),
Na + K: 0.05 to 0.12% by mass (when Na and K are present in the form of a compound or alloy, the content converted to Na and K),
Na / K: 0.3 or more (when Na and K are present in the form of a compound or an alloy, the content converted to Na and K),
It is characterized by being.

The other flux-cored wire for titania-based gas shielded arc welding according to the present invention is a flux-cored wire for titania-based gas shielded arc welding formed by filling a flux in a soft steel or alloy steel sheath, Per total wire mass,
TiO ₂ : 6 to 12% by mass,
Al ₂ O ₃ : 0.4 to 0.8% by mass,
SiO ₂ : 0.1 to 0.5% by mass,
ZrO ₂ : 0.05 to 0.20 mass%,
Mn: 1.0 to 3.0% by mass,
Si: 0.4 to 0.9 mass%,
Al: 0.1 to 0.3% by mass,
Mg: 0.4 to 0.8% by mass,
C: 0.01 to 0.12% by mass,
F: 0.05 to 0.10% by mass,
Containing
Further, each containing at least one selected from the group consisting of Cr, Cu, Ni, V, Nb, Ti, and Zr is 0.1% by mass or less,
The balance is Fe and inevitable impurities,
(TiO ₂ + Al ₂ O ₃ ) / (SiO ₂ + ZrO ₂ ): 10 to 20,
Mg / (Si + Al): 0.4 to 0.7 (when Mg and Si and Al are present in the form of an alloy, the content in terms of Mg, Si and Al),
Na + K: 0.05 to 0.12% by mass (when Na and K are present in the form of a compound or alloy, the content converted to Na and K),
Na / K: 0.3 or more (when Na and K are present in the form of a compound or an alloy, the content converted to Na and K),
It is characterized by being.

  According to the present invention, in vertical welding, even under severe welding conditions such as a wide root gap, there is no dripping of molten metal, good slag removability, little spatter generation, and good Welding workability is obtained. As a result, according to the present invention, a flux-cored wire for gas shield arc welding suitable for all-position welding can be obtained, and a weld metal having excellent mechanical properties can be obtained.

  Hereinafter, the flux-cored wire for gas shielded arc welding of the present invention will be described in detail. First, the inventors of the present application changed the composition of slag generally performed in order to prevent dripping of the molten metal causing the bead shape failure while improving the slag peelability, and the freezing point of the slag. We examined the means to increase

In order to obtain a high melting point slag, as described in Patent Document 1, Al ₂ O ₃ .MgO.ZrO ₂ is effective, but Al ₂ O ₃ .MgO has an action of degrading the slag peelability. ZrO ₂ has an effect of increasing the amount of spatter generated. Therefore, as a means for preventing bead shape defects without degrading the slag removability and spatter generation amount, (1) increasing the amount of TiO ₂ added to produce high melting point slag and not degrade slag removability (2) Addition of Al ₂ O ₃ that generates high-melting-point slag within a range that does not deteriorate the slag removability, (3) Suppression of addition of SiO ₂ that secures arc stability but generates low-melting-point slag, (4 ) Result of adjusting the content of each of TiO ₂ , Al ₂ O ₃ , SiO ₂ , and ZrO _{2 while} suppressing the addition amount of ZrO ₂ , which has the disadvantage of generating high melting point slag but increasing the amount of spatter generated It has been found that it is more effective to adjust the ratio of the total content of TiO ₂ and Al ₂ O _{3 to} the total content of SiO ₂ and ZrO ₂ .

Furthermore, in addition to accelerating solidification of the slag, it is necessary to have a composition and characteristics that prevent the molten metal itself from dripping. For this purpose, the amount of oxygen in the molten metal is generally reduced, and the molten metal is heated at a high temperature. It is effective to increase the viscosity. Patent Document 1 describes that Al and Si are effective as deoxidizers. However, depending on the amount of Al added, Al deteriorates the slag removability due to the formation of Al ₂ O ₃ and the toughness of the weld metal. Deteriorate. In addition, depending on the amount of Si added, the slag solidification point is reduced due to the generation of SiO ₂ , the strength of the weld metal is increased, and the toughness is deteriorated. In the present invention, Mg is effective as a strong deoxidizer for reducing the oxygen content in the molten metal without adversely affecting the strength and toughness of the weld metal, and the content of Mg relative to the total content of Al and Si It has been found that adjusting the ratio of the amounts is effective.

  Further, in order to eliminate the dripping of the molten metal, it is also effective to suppress the vibration of the molten pool, and from the viewpoint of reducing the spatter generation amount, Na and K (Na When K is present in a compound or alloy, it is effective to adjust the ratio of Na content to the total content of alkali metals and the K content of Na and K, respectively. I found it.

  Next, regarding the composition of the flux-cored wire of the present invention, the reason for adding the component and the reason for limiting the composition will be described. However, the content of each of these components is the content per total mass of the wire. Moreover, the composition of this flux wire is a composition of the components contained in all the components including the flux and the outer skin.

“TiO ₂ : 6 to 12% by mass”
TiO ₂ acts as a slag former and arc stabilizer. If TiO ₂ is less than 6% by mass, a slag amount sufficient to support the molten metal cannot be secured, and the molten metal will sag. In addition, when TiO ₂ exceeds 12 wt%, too much slag formation amount, slag inclusion is likely to occur.

“Al ₂ O ₃ : 0.4 to 0.8 mass%”
Al ₂ O ₃ has the effect of increasing the slag freezing point. If Al ₂ O ₃ is less than 0.4% by mass, the effect is not obtained. If Al ₂ O ₃ exceeds 0.8% by mass, the slag removability deteriorates.

“SiO ₂ 0.1 to 0.5 mass%”
SiO ₂ acts as a slag forming agent and an arc stabilizer. If SiO ₂ is less than 0.1% by mass, the arc becomes unstable and the occurrence of spatter increases, and if SiO ₂ exceeds 0.5% by mass, the freezing point of the slag decreases and the molten metal drips down. End up.

“ZrO ₂ : 0.05 to 0.20 mass%”
ZrO ₂ has the effect of increasing the slag freezing point and improving the slag peelability. When ZrO ₂ is less than 0.05% by mass, slag seizure deteriorates due to seizure of slag, and when ZrO ₂ exceeds 0.20% by mass, the occurrence of spatter increases.

“Mn: 1.0 to 3.0% by mass”
Mn acts as a deoxidizer and has the effect of improving the strength and toughness of the weld metal. If Mn is less than 1.5% by mass, deoxidation is insufficient, so that molten metal droops due to a decrease in viscosity, welding defects such as blow holes occur, and strength and toughness deteriorate. If Mn exceeds 3% by mass, the strength of the weld metal becomes too high. More preferably, Mn is 1.55 to 2.05 mass%. This Mn can be added by metal Mn or an iron alloy (Fe-Mn, Fe-Si-Mn, etc.).

“Si: 0.4 to 0.9 mass%”
Si acts as a deoxidizer and has the effect of improving the strength and toughness of the weld metal. When Si is less than 0.4% by mass, deoxidation is insufficient, so that molten metal droops due to a decrease in viscosity, welding defects such as blow holes occur, and strength and toughness deteriorate. When Si exceeds 0.9 mass%, the strength of the weld metal increases and the toughness decreases. This amount of Si is a converted value of Si contained in metal Si or iron alloy (Fe—Si, Fe—Si—Mn, Ca—Si, etc.).

“Al: 0.1 to 0.3 mass%”
Al acts as a deoxidizer and slag former. If Al is less than 0.1% by mass, dripping of the molten metal tends to occur. When Al exceeds 0.3 mass%, the slag peelability deteriorates and the toughness of the weld metal decreases. More preferably, Al is 0.2 to 0.3% by mass. This amount of Al is a conversion value of Al contained in metal Al or iron alloy (Fe-Al).

“Mg: 0.4 to 0.8 mass%”
Mg acts as a strong deoxidizer. If Mg is less than 0.4% by mass, dripping of the molten metal due to a decrease in viscosity due to insufficient deoxidation occurs, and the toughness of the weld metal deteriorates. When Mg exceeds 0.8 mass%, MgO which is a deoxidation product will increase excessively in a molten slag, and the amount of dripping of a molten metal and the generation amount of spatter will also increase. This Mg is the conversion value of Mg contained in metal Mg or various alloys (Al-Mg, Ni-Mg, etc.).

“C: 0.01 to 0.12 mass%”
C has the effect of improving the strength and toughness of the weld metal, so it can be added. When C is added, the content is 0.01 to 0.12% by mass, preferably 0.03 to 0.10% by mass. When C is added excessively, the strength of the weld metal is excessively increased and crack resistance is deteriorated.

“F: 0.05 to 0.10% by mass”
F promotes the release of hydrogen gas that has entered the molten pool and prevents the formation of pits and gas grooves, so it can be added. When F is added, the content is 0.05 to 0.10% by mass. When F is added excessively, spatter increases.

“At least one selected from the group consisting of Cr, Cu, Ni, V, Nb, Ti, and Zr: each 0.1% by mass or less”
Cr, Cu, Ni, V, Nb, Ti, and Zr, as alloy components, contribute to improving the strength of the weld metal and contribute to improving corrosion resistance. However, the excessive addition of Cr, Cu, Ni, V, Nb, Ti, and Zr increases the strength of the weld metal and deteriorates the crack resistance. When these components are contained, respectively. 0.1 mass% or less. Including C and F described above, Cr, Cu, Ni, V, Nb, Ti, and Zr may be contained, but may not be contained.

“X = (TiO ₂ + Al ₂ O ₃ ) / (SiO ₂ + ZrO ₂ ): 10 to 20”
Even if TiO ₂ , Al ₂ O ₃ , SiO ₂ , and ZrO ₂ are within the above-mentioned ranges, the ratio x of the total content of TiO ₂ and Al ₂ O _{3 to} the total content of SiO ₂ and ZrO ₂ is 10 If it is less than this, the fluidity of the slag is increased and the molten metal cannot be supported. On the other hand, when the ratio x exceeds 20, the slag is burned more and the slag peelability is deteriorated. That is, when the total content of SiO ₂ that generates low melting point slag and ZrO ₂ that increases the amount of spatter generated is the denominator, and the total content of TiO ₂ and Al ₂ O ₃ that generates high melting point slag is the numerator. By adjusting the ratio x within an appropriate range of 10 to 20, it is possible to improve the stand-up advanceability without deteriorating the slag peelability and the amount of spatter generated.

“Y = Mg / (Si + Al): 0.4 to 0.7 (when Mg, Si, and Al are present in the form of an alloy, the content in terms of Mg, Si, and Al)”
Even if the contents of Mg, Al, and Si are within the above-described ranges, if the ratio y of Mg to the total content of Si and Al is less than 0.4, the strength of the weld metal increases and the toughness decreases. . When y exceeds 0.7, molten metal drips down and the occurrence of spatter increases. In other words, it is effective for the advancement, but the total content of Si and Al, which can degrade the mechanical properties of the weld metal, is used as the denominator to improve the viscosity of the molten metal and its strong deoxidation performance. Without reducing the mechanical properties of the weld metal by adjusting the ratio y when the Mg content, which improves the toughness of the weld metal, as a molecule, is adjusted to an appropriate range of 0.4 to 0.7. It is possible to improve the standing improvement.

“Na + K: 0.05 to 0.12% by mass, Na / K: 0.3 or more (when Na and K are present in a compound or alloy, contents converted to Na and K, respectively)”
Na and K have an action as an arc stabilizer, and can prevent the molten metal from dripping by suppressing vibration of the molten pool. When the total content of Na and K is less than 0.05% by mass, the above-described effects cannot be obtained. It is easy for dripping. On the other hand, if the ratio of Na content to K content is less than 0.3, the arc stability deteriorates, the amount of spatter generated increases, and the molten metal tends to sag.

  Note that alloy elements such as Si and Mn can be added from the outer skin and / or flux. Further, in order to improve the corrosion resistance, high strength, high temperature corrosion resistance, etc. of the welded portion, alloy components other than the above (Cr, Cu, Ni, V, Nb, etc.) can be added. In addition, fluorides can be added. Moreover, there is no restriction | limiting in the state of a wire surface, and the filling form of the flux in a wire cross section. In addition, as components other than the above, there are Fe, which is a constituent component of the outer shell, iron alloys such as Fe-Mn, Fe-Si, and iron powder, and the remainder is inevitable impurities. Inevitable impurities include P, S, Sb, As, Pb, and the like, and these inevitable impurities need to be regulated to 0.1% by mass or less in total.

  Next, effects of the embodiment of the present invention will be described in comparison with a comparative example that is out of the scope of the present invention. Table 1 below shows examples of raw materials for each component defined in the present invention. The raw materials shown in Table 1 are appropriately blended and filled in a steel (JIS G 23 3141, SPCC) outer shell, and the ratio of the flux to the total weight of the wire is 15% by mass. A flux-cored wire was produced. Tables 2 and 3 show analytical values of the component contents of the flux-cored wires of Examples and Comparative Examples. The remaining main component other than the components in Tables 2 and 3 is Fe, and includes P, S, N, Cu, and the like as inevitable impurities.

The flux-cored wires of Comparative Examples 1 to 22 and Examples 1 to 15 shown in Tables 2 and 3 above are used, steel plates of JIS G 3106 and SM490A are used as materials to be welded, and 100% by mass CO2 as shielding gas. ₂ was supplied at a flow rate of 25 liters / minute, the following welding tests (1) to (3) were performed, and the weldability was evaluated.

(1) Evaluation of standing improvement progress weldability By the method shown in Table 4 below, a bead sag test was performed in standing improvement progress welding, and standing improvement progress weldability was evaluated.

(2) Evaluation of welding workability and slag peelability Welding workability was evaluated by fillet welding, and sensory evaluation of spatter generation and slag peelability were evaluated. The evaluation criteria are as follows.
(2-1) Evaluation of welding workability Small amount of spatter generation (spatter generation amount: less than 1.5 g / min): ○
Slightly large spatter generation amount (spatter generation amount: 1.5 g / min or more): ×
(2-2) Evaluation of slag peelability Good slag peelability (slag natural peel rate (= slag natural peel length / weld length): 25% or more): ○
Slag peelability is poor (slag natural peel rate (= slag natural peel length / weld length): less than 25%): ×

(3) A test steel plate corresponding to JIS G 3106 (SM490A) was used and welded by the test method shown in Table 5 below in accordance with the test method for all weld metals specified in JIS Z 3313.
The evaluation criteria are as follows.
Absorption energy by Charpy impact test of 60J or more and less than 90J: ○
Absorption energy by Charpy impact test is less than 60J: ×
Tables 6 and 7 below show the evaluation results of the welding tests described above.

As shown in Tables 6 and 7, in Comparative Example 1, since TiO ₂ is out of its lower limit, only the stand-up improvement is inferior, and in Comparative Example 2, only TiO ₂ is out of its upper limit. Therefore, dripping of the molten metal due to an excessive amount of the slag forming agent, an increase in large grain spatter, and deterioration of mechanical properties due to poor deoxidation occurred. In Comparative Example 3, since only Al ₂ O ₃ is out of the lower limit value, the improvement in standing up is inferior due to a decrease in the viscosity of the slag. In Comparative Example 4, only Al ₂ O ₃ is out of the upper limit value. For this reason, poor slag releasability due to seizure of slag onto the weld metal occurs. In Comparative Example 5, since SiO ₂ is out of the lower limit value and the (TiO ₂ + Al ₂ O ₃ ) / SiO ₂ + ZrO ₂ ) ratio x is out of the upper limit value, solidification becomes too fast, and conversely, slag Deterioration of the standing improvement due to obstruction was observed. In Comparative Example 6, since only SiO ₂ deviated from the upper limit value, the solidification of the slag was slow, the slag could not hold the molten metal, and the dripping of the molten metal occurred.

In Comparative Example 7, since only ZrO ₂ is out of the lower limit value, slag peelability failure due to slag sticking to the weld metal occurs. In Comparative Example 8, since only ZrO ₂ was out of the upper limit, solidification of the slag was delayed and dripping of the molten metal occurred. In Comparative Example 9, TiO ₂ , Al ₂ O ₃ , SiO ₂ , and ZrO ₂ are within the specified range, but only the (TiO ₂ + Al ₂ O ₃ ) / [SiO ₂ + ZrO ₂ ) ratio x has its lower limit. The slag solidified slowly and the viscosity was low, so that dripping of the molten metal occurred. In Comparative Example 10, TiO ₂ , Al ₂ O ₃ , SiO ₂ , and ZrO ₂ are within the specified range, but only the (TiO ₂ + Al ₂ O ₃ ) / [SiO ₂ + ZrO ₂ ) ratio x has its upper limit. As a result, the solidification of the slag became too fast, the deterioration of the standing improvement due to the slag interfering with the slag, and the poor slag peelability due to the slag sticking to the weld metal occurred.

  In Comparative Example 11, since only Mn is out of the upper limit, the amount of Mn in the weld metal is excessive, and the tensile strength is low. Further, in Comparative Example 11, deterioration of the standing improvement due to excessive generation of MnO, which is a low melting point compound, was observed in the slag, and large spatter was also generated. In Comparative Example 12, since only Mn is out of the lower limit, the deoxidation performance is inferior, the impact performance of the weld metal is inferior, and a weld defect due to poor deoxidation occurs. In Comparative Example 13, only Si is outside the lower limit value, so the deoxidation performance is inferior and the impact performance of the weld metal is inferior. In Comparative Example 13, the concentration of the arc was strong and the stand-up improvement was inferior. In Comparative Example 14, since only Si deviated from the upper limit, the amount of Si in the weld metal was excessive, and the impact performance was deteriorated due to the excessively high tensile strength.

In Comparative Example 15, since only Al was out of the lower limit, deterioration of the standing improvement due to a decrease in the viscosity of the molten metal was observed. In Comparative Example 16, since only Al deviated from the upper limit value, the impact performance of the weld metal was inferior, and deterioration of slag peelability due to excessive generation of Al ₂ O _{3 in} the slag was observed. In Comparative Example 17, only Mg was out of the lower limit value, so that the deoxidation performance was inferior, the impact performance of the weld metal was inferior, and deterioration of the standing improvement due to the decrease in the viscosity of the molten metal was observed. In Comparative Example 18, since only Mg is out of the upper limit, the yield in the weld metal of Mn and Si due to excessive deoxidation performance becomes too high, and the impact performance deteriorates due to the tensile strength becoming too high. It was seen. In addition, large spatter increased and deterioration of slag removability due to excessive MgO generation in the slag was observed.

In Comparative Example 19, Si, Al, and Mg are in their specified ranges, but the Mg / (Si + Al) ratio y is out of the lower limit value, so that the impact performance is deteriorated due to excessive increase in the tensile strength of the weld metal. It was observed. In Comparative Example 20, Si, Al, and Mg are within the specified ranges, but the Mg / (Si + Al) ratio y is outside the upper limit value, so deterioration of the standing improvement due to insufficient viscosity of the molten metal is seen. It was. In Comparative Example 21, since Na + K was out of the lower limit value, the arc concentration was strong, the vertical improvement progress was deteriorated, and large spatter was generated. In Comparative Example 22, since Na + K was out of the upper limit, deterioration of the standing improvement due to excessive generation of Na ₂ O and K ₂ O, which are low melting point compounds, was observed. In Comparative Example 23, Na + K was within the specified range, but Na + K was out of the lower limit value, so large spatter increased.

  On the other hand, since all of Examples 1 to 15 satisfied all the prescribed ranges of the present invention, all the above welding characteristics were good.

  In addition, although the welding workability | operativity of downward and horizontal fillet welding was confirmed by the same test, the Example of this invention was all favorable.

  As described above in detail, according to the present invention, the welding workability such as the spatter generation amount and the slag peelability, and the mechanical properties of the weld metal are not deteriorated, and the high welding current and the wide welding can be achieved by the vertical improvement welding posture. Even under severe welding conditions such as route spacing, dripping of molten metal and slag can be prevented.

Claims (2)

In the flux-cored wire for titania-based gas shielded arc welding formed by filling the outer skin made of mild steel or alloy steel with flux, the entire outer skin and flux, per total mass of the wire,
TiO ₂ : 6 to 12% by mass,
Al ₂ O ₃ : 0.4 to 0.8% by mass,
SiO ₂ : 0.1 to 0.5% by mass,
ZrO ₂ : 0.05 to 0.20 mass%,
Mn: 1.0 to 3.0% by mass,
Si: 0.4 to 0.9 mass%,
Al: 0.1 to 0.3% by mass,
Mg: 0.4 to 0.8% by mass,
Containing
The balance is Fe and inevitable impurities,
(TiO ₂ + Al ₂ O ₃ ) / (SiO ₂ + ZrO ₂ ): 10 to 20,
Mg / (Si + Al): 0.4 to 0.7 (when Mg and Si and Al are present in the form of an alloy, the content in terms of Mg, Si and Al),
Na + K: 0.05 to 0.12% by mass (when Na and K are present in the form of a compound or alloy, the content converted to Na and K),
Na / K: 0.3 or more (when Na and K are present in the form of a compound or an alloy, the content converted to Na and K),
A flux-cored wire for titania-based gas shielded arc welding. In the flux-cored wire for titania-based gas shielded arc welding formed by filling the outer skin made of mild steel or alloy steel with flux, the entire outer skin and flux, per total mass of the wire,
TiO ₂ : 6 to 12% by mass,
Al ₂ O ₃ : 0.4 to 0.8% by mass,
SiO ₂ : 0.1 to 0.5% by mass,
ZrO ₂ : 0.05 to 0.20 mass%,
Mn: 1.0 to 3.0% by mass,
Si: 0.4 to 0.9 mass%,
Al: 0.1 to 0.3% by mass,
Mg: 0.4 to 0.8% by mass,
C: 0.01 to 0.12% by mass,
F: 0.05 to 0.10% by mass,
Containing
Further, each containing at least one selected from the group consisting of Cr, Cu, Ni, V, Nb, Ti, and Zr is 0.1% by mass or less,
The balance is Fe and inevitable impurities,
(TiO ₂ + Al ₂ O ₃ ) / (SiO ₂ + ZrO ₂ ): 10 to 20,
Mg / (Si + Al): 0.4 to 0.7 (when Mg and Si and Al are present in the form of an alloy, the content in terms of Mg, Si and Al),
Na + K: 0.05 to 0.12% by mass (when Na and K are present in the form of a compound or alloy, the content converted to Na and K),
Na / K: 0.3 or more (when Na and K are present in the form of a compound or an alloy, the content converted to Na and K),
A flux-cored wire for titania-based gas shielded arc welding.