JPH0416275B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a raw material flux for welding materials, and more specifically, it is suitable for coating materials for coated arc welding rods, sintered fluxes for submerged arc welding, fluxes for flux-cored wires, etc. This invention relates to a flux raw material for welding materials that has improved welding workability, particularly arc stability. (Prior art) Raw material fluxes for welding materials used in shielded arc welding, submerged arc welding, MIG welding, carbon dioxide arc welding, etc. generally consist of slag agents, shielding agents, arc stabilizers, alloy components, deoxidizers, etc. It is suitably adjusted and used as a coating material for coated arc welding rods, sintered flux for submerged arc welding, flux for flux-cored wire, etc. according to various welding methods. Among these flux constituents, the deoxidizing agent together with the shielding agent protects the arc from the atmosphere and maintains the arc in a reducing atmosphere, reducing alloy components and improving the yield of metal powder and other weld metal. It is an ingredient that plays a very important role. By the way, conventionally, such deoxidizers include:
Metal powders such as Mg, Al, Mn, Fe-Si, Fe-
Intermetallic compounds or alloy powders such as Mn, Fe-Zr, Fe-Ti, REM-Ca-Si are used (e.g.
(Japanese Patent Application Laid-open No. 61-206597). (Problem to be Solved by the Invention) However, when the amount of such a deoxidizing agent increases, it adversely affects the stability of the arc.
If there are problems such as an increase in the amount of spatter or fume, poor slag coverage, and difficulty in obtaining a good bead shape, and further deterioration of arc stability, blowholes may be necessary. It may also be the cause of occurrence. These are thought to occur because the addition of a deoxidizing agent lowers the oxygen concentration in the arc and changes the physical properties of the molten metal (suspended droplets), particularly the surface tension and physical properties of the slag. Therefore, in the past, it was not possible to sufficiently add such a deoxidizing agent to the flux, and welding had to be carried out without deoxidizing, which increased the amount of oxygen in the weld metal and affected its mechanical performance, such as toughness. There were also quite a few negative effects, such as variations in values. The present invention has been made to solve the problems of the prior art described above, and even when the amount of deoxidizing agent in the raw material flux is increased, arc stability is good and excellent welding can be achieved. Another object of the present invention is to provide a flux raw material for welding materials that has workability. (Means for Solving the Problems) In order to achieve the above object, the present inventor first of all aimed at maintaining arc stability even when a large amount of deoxidizing agent was added. An attempt was made to adjust the flux composition in order to lower the surface tension of the molten metal (suspending droplets) and make it easier for the molten metal to spray and transfer. In other words, O, P, S,
O (oxygen) group elements such as Se and Te and rare earth elements were added to the flux. However, since Se and Te are highly toxic, and P and S cause cracks in the weld metal, it has been found that none of the O group elements can be used. On the other hand, when rare earth elements were added, although the surface tension of the molten metal could be reduced, the viscosity of the molten slag increased and the arc stability was not improved as much as expected.
This increase in the viscosity of the molten slag is thought to be due to the fact that all oxides of rare earth elements have high melting points. Based on the above results, the present inventor changed his point of view and attempted to improve arc stability by adding an alkali metal with a low ionization voltage to the flux to make it easier to generate an arc. In this case, alkali metals themselves are generally very unstable and cannot be used as they are immediately oxidized in the air, so they are added to the flux in the form of oxides, fluorides, carbonates, and complex compounds containing these. did. As a result, in the method of adding these alkali metal compounds, as the amount added is increased to improve arc stability, the viscosity of the slag is adversely affected, and the arc becomes less concentrated. Various adverse effects occurred, such as the arc becoming unstable such as butterflies, and the moisture absorption resistance of the flux deteriorating, especially in coated arc welding rods and fluxes for submerged arc welding. In this regard, there has been an attempt (Japanese Patent Publication No. 62-25479) to contain lithium among alkali metals in the flux in the form of lithium oxide, and to reduce the lithium in an arc using a reducing agent contained at the same time.
I have a similar problem. However, according to the experimental research conducted by the present inventors, it was found that the method of adding alkali metals did have various negative effects when added in large amounts, but it was found that adding a small amount had an effect of improving arc stability. Since we expected that the effect of alkali metals on improving arc stability would be greatly affected by the manner in which they were added, we further investigated various ways in which they were added.
As a result, through numerous experimental results, alkali metals basically improve arc stability, but
When added to flux in the form of compounds such as oxides, decomposition reactions of the compounds inevitably occur, and counterions (O, F ions) and decomposed gases (CO ₂ , CO) are generated, which can cause arcing. It was found that the stability deteriorated. Therefore, it has been found that arc stability can be sufficiently improved if it is possible to add the alkali metal element in the form of a metal, in other words, if it is possible to add the alkali metal element in the form of a metal, which does not cause the decomposition of such compounds and the generation of ions or decomposed gases. Based on this, we have repeatedly conducted experimental research on the mode of addition in the form of metals. As a result, considering that alkali metals are generally very unstable in the atmosphere and cannot be applied as they are, when they are made to exist in certain metals, such as Al, Mg, Si, Ca, and Fe, It was found that alkali metals can exist stably, and that the arc stability improvement effect far exceeds initial expectations. This is where the present invention is made. That is, the flux raw material for welding materials according to the present invention contains at least Li, Li,
It is characterized by using metallic powder (provided that intermetallic compound and alloy powder) containing one or more of Na and K at a concentration of 0.1 to 50 at%. The present invention will be explained in detail below based on examples. As mentioned above, the alkali metals Li, Na, K, Rb, and Cs generally exist stably in other metals such as Al, Mg, Si, Ca, and Fe, so one or more of them is usually used. By dissolving two or more of the latter in other metals, they are used as an alkali metal-containing alloy or an intermetallic compound. Of course, it can also be used as an alloy of two or more alkali metals.
Possible depending on the case. In this way, when used in the form of metal powders such as intermetallic compounds and alloys (hereinafter referred to as metallic powders) rather than in the form of non-metallic compounds such as oxides, the melting point of alkali metals is low, so the oxides The alkali metal vapor or ions migrate into the arc more easily than when added with compounds such as
Since counter ions and decomposition gases are not generated,
The arc stability is significantly improved, which in turn has the effect of significantly improving welding workability, and since the alkali metal itself is a strong deoxidizing agent, it is added as a deoxidizing agent with excellent arc stability. can do. When adding such alkali metal-containing metallic powder to the raw material flux, it can be added to the flux in the following manner. As the alkali metal, any alkali metal element may be used alone, or two or three components may be used.
Although they may be used in combination like other components, at least one of Li, Na, and K may be used in view of the arc stability improvement effect, deoxidizing effect, ease of handling, etc.
It is necessary to use one species or two or more species. Among these alkali metals, Li is better from the viewpoint of stability and safety in producing the alkali metal-containing metallic powder. In order to improve arc stability, other metals containing alkali metals are preferably metals that can be added in bulk and in a large amount to the flux at the same weight, in other words, they can be uniformly distributed. Low density Al and/or Mg
is better. Of course, metals other than Al and Mg such as Si, Ca, Fe, Zr, Zn, Cu, and Mn may also be used, but arc stability may be further improved if these are added as a third component to Al or Mg. be. In particular, since alkali metals themselves are strong deoxidizing agents, Al containing alkali metals,
In addition to the effect of improving arc stability, deoxidizing agents such as Mg significantly increase the deoxidizing effect of Al and Mg, making it possible to reduce the amount of deoxidizing agent added to the flux. This effect is thought to be due to the fact that the addition of alkali metals deteriorates the stability of Al and Mg, which improves the deoxidizing effect. In fact, in the case of Al powder containing alkali metals, when a metal dust explosion test was conducted,
The results showed that metal dust explosions were more likely to occur than Al powder. The content of the alkali metal contained in the above-mentioned other metals is preferably in the range of 0.1 to 50 at% in order to effectively improve the arc stability.
Furthermore, considering handling stability, it is 0.5 to 30at.
% is preferred. In addition, the third component above is several ppm~
It is preferable to add it in a range of several percent. For example, Al
In the case of Mg and other Zr, Si, Ca, Fe,
No problem occurred even when Zn, Cu, Mn, etc. were added in the above ranges. The amount of alkali metal-containing metallic powder added to the flux raw material varies slightly depending on the type of flux to be applied, but it is preferably 10 ppm or more. Depending on the amount, up to about 15wt%, e.g.
It can be added in a range of 5 to 15 wt%.
Of the alkali metals, Na and K are effective in deoxidizing and improving arc stability when added in small amounts (1 ppm to several 100 ppm in terms of Na and K), but when added in large amounts, Li addition Please note that the alkali metal-containing metallic powder will be more unstable and difficult to handle than in the case of In particular, among alkali metals, Li is preferable due to its effect on improving arc stability and ease of handling;
In the case of containing metallic powder, if the amount of Li is less than 0.1at%, there is not much effect on improving arc stability.
It is desirable to contain 0.1at% or more, and 10at%
In the above cases, stability can be improved by oxidizing or carbonating the metal surface. However, if the content exceeds 50at%, the metallic powder becomes very easily oxidized and air oxidation on the surface becomes unstoppable, making it dangerous to handle and making it difficult to obtain metallic powder of a certain quality. . When adding metallic powder having such a configuration to the flux, it is desirable that 50% or more of the total particle size be in the range of 74 to 350 μm. As the particle size of 350μm or more increases, the mixability with other flux components becomes worse, and the particle size increases.
If it is less than 74 μm, the risk of metal dust explosion increases significantly, which is not desirable. (Example) Next, an example of the present invention will be shown. Example 1 Li-containing metallic powder (alloy powder) having the chemical composition (at%) shown in Table 1 was processed using the gas atomization method and REP.
(rotating electrode) method or mechanical crushing method. In any of the obtained powders, at least 50% of the particles were within the range of 74 to 350 μm in particle size at the time of powder production. here,
A particle size of 350 μm means that the particle passes through a node with an opening of 350 μm, and may be long and thin.

[Table] Next, a jointed flux-cored wire having the flux composition (wt%) shown in Table 2 was produced using the Li-containing alloy powder in a conventional manner. The chemical composition and flux filling rate of the hoop material used are shown in Table 3. Using the flux-cored wires W-1 and W-2 thus obtained, welding was performed under the conditions shown in Table 4, and the arc stability and toughness of the weld metal were investigated. The results are shown in Table 5. In Table 5, regarding the evaluation of arc stability, fluctuations in arc length during welding (downward beam on plate) were investigated using high-speed video.
○ if the variation in arc length is within twice the wire diameter
The evaluation was made by marking the case with a mark, and by marking the case of twice or more with an x mark. In addition, regarding the variation in toughness of weld metal,
Using a JISZ2202 No. 4 test piece, a Charpy impact test was conducted in accordance with JISZ2242 at a test temperature of 0°C, and the variation in absorbed energy was 3 for n = 5.
The evaluation was done by marking the case of less than Kgf·m with ◯, and the case of exceeding 3 Kgf·m with × mark. The danger of metal powder is evaluated based on the survey results shown in Table 1. If there is no risk of metal dust explosion, mark ○, and if there is significant oxidation on the powder surface, mark △. Cases where there is a risk of cutting powder igniting are marked with an x. The Li-containing alloy used in test No. 11 in Table 4 is Li-containing alloy No. L in Table 1.
-9 and pure Al powder mixed at a ratio of 1:1 (weight ratio).

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[Table] As is clear from Table 5, the Li concentration is too low.
In Test No. 1, in which Al alloy powder was added to the flux, there was a large variation in arc length and large variation in toughness, but Li-containing alloy powder or mixed powder with a Li concentration of 0.1 at% or more was found. In the case of Tests No. 2 to No. 13 in which Li was added to the flux, the arc stabilizing effect and deoxidizing effect of metal Li combined to provide good arc stability and stable toughness values. Test No. 13 was an example in which Al alloy powder containing 50 at% or more of Li was added to the flux. Although no particular adverse effect was observed on the performance of the wire, as shown in Table 1, Li-containing Al alloy powder was added to the flux. There was a problem in handling Al alloy powder. Note that this example is for flux-cored wire with a seam.
This is an example of adding Li-containing alloy powder, but even when applied to seamless flux-cored wire,
A similar effect was obtained. Example 2 Using the Li-containing Al alloy powder shown in Table 1,
A coated arc welding rod having the flux composition (wt%) shown in the table was manufactured by a conventional method. The amount of water glass added was 15 ml per 100 g, and the coated rod was dried at 450° C. for 1 hr. In addition, the core wire uses a mild steel core wire with a diameter of 4.0 mmφ, and the coating diameter is 6.25 mmφ.
And so. Next, using the thus obtained coated arc welding rod, welding was performed under conditions of a voltage of 32V and a current of 280A.
Bead-on-plate welding was performed on the base metal of SM41B material, and the arc stability was investigated. The results are shown in Table 7. In addition, arc stability is evaluated by blowhole resistance at arc start. Arc starts are performed 10 times, and as a result of X-ray transmission, if the number of blowholes is 10 or less per average of n = 3, it is evaluated as ○. Evaluation was made with a mark, and a case where the number exceeded 10 was evaluated with an x mark.
Furthermore, the danger of metal powder was evaluated in the same manner as in Table 5. As is clear from Table 7, the Li concentration is too low.
In Test No. 1, in which Al alloy powder was added to the coating material, the blowhole resistance at arc start was poor, but in Test No. 2, in which Al alloy powder with a Li concentration of 0.1 at% or more was used, In No. 8, the blowhole resistance at arc start was improved due to the arc stabilizing effect of metal Li. Test No. 8 is an example using Al alloy powder containing 50 at% or more of Li, but although the blowhole resistance at arc start was improved, as shown in Table 1, Li-containing Al alloy powder There was a problem in handling Al alloy powder.

【table】

[Table] In each of the above examples, cases where Li is used among the alkali metals are shown, but other metals such as Na and K can also be used to improve arc stability.
Needless to say, it can exhibit a deoxidizing effect. (Effects of the Invention) As detailed above, according to the present invention, an intermetallic compound containing at least one or more of Li, Na, and K among alkali metals can be used as a flux raw material for welding materials. Since metallic powder in the form of a metal such as an alloy is used, even when the amount of deoxidizing agent is increased, the arc stability is significantly improved and the mechanical performance of the weld metal is improved.
Welding workability can be significantly improved.

Claims (1)

[Claims] 1 Among alkali metals, at least Li, Na,
and K at a concentration of 0.1 to 50 at% (provided that intermetallic compounds and alloy powders) is used as a flux raw material for welding materials.