JPH0159079B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to the improvement of flux-cored wire used in gas-shielded arc welding of stainless steel, and more specifically, the present invention relates to the improvement of flux-cored wire used in gas _- shielded arc welding of stainless steel. This invention relates to a flux-cored wire for stainless steel welding that has excellent droplet transfer properties and good welding efficiency. [Prior art] Gas-shielded arc welding of stainless steel using flux-cored wire protects the weld metal by both a slag shield and a gas shield created by the flux built into the wire, so the bead shape is smaller than MIG welding using solid wire. It is rapidly becoming popular because it has good properties and is less prone to defects such as blowholes and poor fusion. In particular, applications in vertical positions and thinner plates are being considered, and demand for thin wires of 1.2 mmφ, 1.0 mmφ or smaller is increasing. However, in the case of flux-cored wire for stainless steel welding, a large amount of alloy components are added to the flux to adjust the difference between the outer stainless steel component and the target weld metal component, and to compensate for the consumption of the alloy component by welding. It must be contained in
Moreover, since the electrical resistance of the stainless steel outer shell is high, spatter tends to occur frequently. Furthermore, as pointed out in Japanese Patent Application Laid-Open No. 49-123140, in flux-cored wire, the welding current flows only to the outer sheath of the wire, which delays the melting of the flux in the core, causing the legs of the arc to move around. There are problems in that the arc is disturbed and the concentration of the arc is poor, but these problems are especially noticeable in the case of stainless steel welding wire because the electrical resistance of the outer sheath is high and the wall thickness is thin. The problem could not be solved only by adjusting the particle size of the built-in flux as disclosed in the same publication. Regarding the reduction of spatter generation,
Publication No. 70993 discloses a technology in which SiO ₂ is contained in the wire in an amount more than 10 times that of metal fluoride, but metal fluoride is an effective component for improving pitting resistance and adjusting the melting point of slag. The above-mentioned limitation of less than one-tenth of SiO ₂ in consideration of the necessity of containing other components and the appropriate range of flux filling rate can be a considerable obstacle in designing the performance of flux-cored wires. It was hot. Furthermore, when welding stainless steel, it is necessary to remove spatter because it can become a starting point for corrosion, and in order to reduce the number of work steps, there has been a demand from various fields for further reduction of spatter. [Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to reduce the amount of spatter, reduce the arc state, and improve droplet migration. The purpose of the present invention is to provide a flux-cored wire for stainless steel welding that has excellent welding efficiency and excellent welding efficiency. [Means for Solving the Problems] As a result of intensive studies aimed at reducing spatter during gas-shielded arc welding of stainless steel using flux-cored wire, the present inventors found that the amount of spatter generated is due to the small amount of slag content in the wire. We found a new _SiO2 - _ZrO2 - _TiO2- based component range as a slag system that exhibits sufficient slag envelopment and good slag removability even with a small amount of slag. It has also been found that arc conditions and droplet transferability can be improved by increasing the content of metal components in the flux to make it easier to melt the flux. The present invention is based on the above findings, and its gist is that the total weight of the wire is
3.7% _SiO2 , 0.7-2.0% _ZrO2 , 0.7-4.2%
_TiO2 , 0.1-0.7% metal fluoride, 0.3-2.3%
In addition to containing Mn in the flux, the total slag component in the flux is 4.5 to 4.5% of the total weight of the wire.
9.5%, the total metal component in the flux accounts for 59 to 85% of the total weight of the flux, and the flux-cored wire for stainless steel welding is characterized in that it contains substantially no carbonates. The present invention will be explained in detail below along with its operation. [Function] First, the flux-cored wire of the present invention is
A wire having a cross-sectional shape as shown in Figures a to d, examples of which are shown in Figure b
- Those with seam 3 as shown in d, or a in the same figure
It may be seamless as shown in the figure. Mild steel, ferritic stainless steel, and austenitic stainless steel can be used as the outer skin material, but in the case of austenitic stainless steel welding wires, it is difficult to design the composition to use mild steel or ferritic stainless steel outer skin. It is. Next, the present invention is based on the following experimental results. First, using SUS 304L steel strips and pipes, we manufactured flux-cored wires with a wire diameter of 1.2 mm equivalent to JIS Z3323YF-308L with different cross-sectional shapes, flux compositions, and filling rates as shown in Figure 1. DCRP200A, 31V, on steel plate
By performing carbon dioxide arc welding under the welding conditions of 30cm/min and collecting and weighing the spatter generated during the welding in a copper collection container, we can compare the amount of spatter generated for each wire and determine the influence on the amount of spatter generated. The factors were considered. The study range for the flux filling rate was 9 to 30%. As a result, they focused on the fact that there was a weak correlation between the weight per unit length of the wire and the amount of spatter generated. We have come to understand a clear trend between In other words, FIG. 2 shows the relationship between the content of slag components in the wire and the amount of spatter generated.
It has become clear that the amount of spatter generated is almost unrelated to the cross-sectional shape of the wire or the flux filling rate in the wire, and decreases as the amount of slag components in the wire decreases. This is because wires with a low slag component content have a low flux filling rate and a thick outer skin thickness, or have a large amount of metal components in the flux, and the proportion of metal substances in the wire cross section is large. This is thought to be caused by a substantial decrease in the current density during welding. However, slag in flux-cored wire for gas-shielded arc welding is added to adjust the bead shape and protect the weld metal, and if the amount is insufficient, the above effects cannot be achieved, and the slag will form the bead. It is not possible to simply reduce the amount of slag because it will stick to the surface and deteriorate the bead shape and bead appearance. Therefore, the inventors of the present invention have repeatedly studied the melting point and fluidity of slag with the aim of developing a slag component system that does not impair slag encapsulation and slag removability even with a small amount of slag. of
It was discovered that SiO ₂ −ZrO ₂ −TiO ₂ based slag is suitable. Next, as a result of various studies in order to accelerate the timing of melting of the flux portion, we investigated the phenomenon of the flux column protruding, which causes a delay in the melting of the internal flux relative to the wire sheath, making the arc unstable and deteriorating arc concentration. It has been found that the higher the metal component content in the flux, the more concentrated and stable the arc is, and the droplets also take on a mostly spray-like transfer form, resulting in an extremely stable arc with uniform arc sound. This phenomenon can be understood as follows. That is,
Generally, oxides and fluorides are used as components that form slag, but among these, fluorides and
Alkali metal oxides such as NA ₂ O and K ₂ O have a significant effect on slag physical properties and arc conditions, so their usage is inevitably limited, and slag
The main component is composed of oxides such as SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ and MgO. However, all of these main component oxides have higher melting points than the outer stainless steel, and this is thought to be the cause of the time lag in melting between the outer stainless steel and the internal flux mentioned above. If a large amount of metal powder with a relatively low melting point enters between these high melting point oxide grains, the metal itself may become an arc generation point, or even if it does not become an arc generation point, it is more likely than the surrounding high melting point oxides. Since the flux is melted first, it becomes extremely easy to melt the entire flux, and as a result, the time difference between melting with the outer skin is almost eliminated, the protrusion phenomenon of the flux column is eliminated, and the arc condition and droplet migration are thought to be improved. . The effect of improving the arc condition by increasing the metal content was particularly noticeable in wires with simple circular cross sections as shown in FIGS. 1a, b, and c. The reasons for limiting the various numerical values defined in the present invention will be described below. First, to explain the slag component, which can be said to be the basis of the present invention, SiO ₂ is a necessary component to form a slag with good encapsulation properties, but if it is less than 1.5%, the effect can be exhibited, and the slag encapsulation property is reduced. However, if it exceeds 3.7%, the slag will seize and the releasability will deteriorate. In addition, as raw materials for SiO ₂ , in addition to silica sand and silica stone, subcomponents of raw materials such as wollastonite, zircon sand, and potassium feldspar can be used. ZrO ₂ is a component that gives fluidity to slag and is effective in reducing the amount of slag. If it is less than 0.7%, the effect is insufficient, and if it exceeds 2.0%, the flux becomes difficult to dissolve. The difference in melting time between the wire sheath and the internal flux increases, deteriorating the arc condition. Although zirconium oxide, zircon flour, zircon sand, etc. can be used as raw materials, it is desirable to use zircon sand with a low melting point. TiO ₂ forms a dense slag with good releasability, but if it is less than 0.7%, the effect is not exhibited;
If it exceeds this, the fluidity of the slag will deteriorate, the amount of slag required to ensure slag envelopment will increase, and spatter will be more likely to occur. As raw materials, rutile, titanium white, titanium slag, illuminite, and titanates such as potassium titanate, sodium titanate, and calcium titanate are used alone or in combination. Metal fluoride is added to adjust the melting point of slag and improve pitting resistance. If it is less than 0.1%, pitting resistance cannot be ensured, and if it exceeds 0.7%, the slag melting point becomes too low and the bead shape deteriorates. At the same time, spatter is likely to occur due to the generation of fluorine gas. Metal fluorides include CaF ₂ , NaF,
AlF ₃ , MgF ₂ , LiF, etc. are used alone or in combination, and within the above range, the effects are almost the same for all fluorides. In the present invention, slag components refer to nonmetallic components such as oxides and fluorides, and in addition to the above, Al ₂ O ₃ is used to adjust the basicity of the slag and finely adjust the melting point and fluidity of the slag. , FeO, MgO, CaO,
MnO, BaO, Cr ₂ O ₃ used for adjusting alloy yield,
NiO, Na ₂ O used for slight adjustment of arc condition,
K ₂ O, Li ₂ O, Bi ₂ O ₃ , PbO, etc. used for improving slag removability, and impurities such as P, S, etc. derived from these raw materials are also included. One of the key points of the present invention is that the total slag component including these is in the range of 4.5 to 9.5% of the total weight of the wire.
If it exceeds 9.5%, the amount of spatter will increase as mentioned above, and if it is less than 4.5%, no matter how good the slag type is, the amount of slag will be insufficient and it will be impossible for the slag to cover the bead surface. It depends. Note that excessive amounts of alkali metal oxides such as Na ₂ O and K ₂ O can cause an increase in spatter, so the total
The total amount should be within 0.6% because low melting point metal oxides such as Bi ₂ O ₃ cause deterioration of the bead shape and decrease in toughness.
Each is preferably 0.2% or less. In addition, depending on the raw material particle size, flux components, filling method, etc., flux may be used after being granulated with a binding agent.
It is necessary to mix the raw materials by considering in advance that SiO ₂ , Na ₂ O, K ₂ O, etc. will increase. Next, Mn is added as a deoxidizing agent, and has the effect of improving cracking resistance and stabilizing the arc, but if it is less than 0.3%, the effect cannot be exhibited;
Exceeding this will impair slag fluidity and slag removability. Note that the Mn referred to here refers to metallic manganese or ferromanganese, and does not include Mn derived from iron powder or stainless steel powder. This is because the Mn contained in iron powder or stainless steel powder, which is about 2% at most, cannot be expected to be effective as a deoxidizing agent. In the present invention, metal components include alloying agents such as Ni, Cr, Mo, Nb, W, and Cu that are normally used in stainless steel, deoxidizing agents such as Al, Ti, and Mn, and ferroalloys containing these components. means iron powder, stainless steel powder, etc. In particular, iron powder, stainless steel powder, and ferroalloy can be used depending on the component composition in order to adjust the metal component content in the flux. In other words, JIS Z3323 standardizes various stainless steel flux-cored wires to match the various stainless steels on the market. When designing a wire equivalent to YF-309 or YF-309J, it is necessary to increase the amount of alloy components in the flux, so use pure nickel or pure chromium powder, which has a relatively low alloy component.
In the case of YF-308 equivalent wire, the metal content in the flux must be kept high by using metal powder with a low alloy content, such as iron powder, stainless steel powder, or ferrochrome. Regarding weld metal components in various standard wires,
In consideration of wear due to welding, the amount of wire alloy is designed using the following formula as a guide. M _D = M _C × (100−R) + M _F × R / 100−S M _D : Alloy content in the weld metal without wear (%) M _C : Alloy content in the outer skin (%) M _F : Alloy content in flux (%) R: Flux filling rate (%) S: Slag content in wire (%) For example, in the case of carbon dioxide arc welding, Ni is almost 100% and Cr is about 90%. %, and the yield increases slightly as the proportion of argon in the shielding gas increases. In the present invention, the metal component in the flux is set to 59 to 85% of the total weight of the flux.If it is less than 59%, the timing of flux melting will be delayed, resulting in a stable arc state with uniform arc sound due to spray-like droplet transfer. Moreover, if it exceeds 85%, the flux filling rate in the wire will have to be high due to the balance with the slag component content, and wire breakage problems will easily occur in the wire drawing process. Finally, since carbonate decomposes during welding and generates carbon dioxide gas, which causes spatter, it is desirable that its content be small, and it is not actively added. In the present invention, "substantially not containing" means that the permissible limit when the material is mixed as an unavoidable impurity in other raw materials is 0.05% or less based on the total weight of the wire in terms of CO ₂ . The effects of the present invention will be specifically explained using examples below. [Example] Using stainless steel strips and pipes shown in Table 1, JIS Z3323YF-
Wires equivalent to 308L, YF-309L, and YF-316L are manufactured, and DCRP200A, 31V,
Carbon dioxide arc welding was performed in a downward position under welding conditions of 30 cm/min, and the welding workability of each method was compared. The wire diameter is 1.2 mm, and the type using pipes P1, P2, and P3 as the outer sheath is the seamless type shown in Figure 1a, the type using steel strips H1 and H2 is the seamless type shown in Figure 1b, and the type using steel strip H3 is shown in Figure 1b. The cross-sectional shape shown in FIG. 1d was used. The results are shown in Table 3. SiO ₂ , ZrO ₂
Or wire No. 15 with low metal fluoride content,
16, 18, 46, wire No. 10 with low slag content,
Both Nos. 15 and 43 had insufficient slag encapsulation. In addition, wire No. with high SiO ₂ or Mn content.
11, 14, 41, Wire No. 17 with low _TiO2 content,
Sample No. 47 had poor slag removability. Furthermore, wire Nos. 44 and 52 with high ZrO ₂ content, wires No. 8, 12, 41, 42, 50, and 51 with low metal component content for flux, and wire No. 19 with low Mn content are There were problems with the condition and droplet migration. Wires No. 12 and 45, which have a high TiO ₂ content, have no choice but to increase the amount of slag component in order to ensure slag encapsulation.
Similar to 41 and 42, the amount of spatter generated increased. Further, wire No. 13 with a high metal fluoride content generated a large amount of gas and a large amount of spatter. In contrast, in the case of the present invention, in which the flux component range and the slag component amount are appropriate, and the metal component content in the flux is high, the arc condition and droplet transferability are good, the amount of spatter is small, and the slag There were no problems with encapsulation or slag removability, and extremely good welding workability was demonstrated. In addition, the evaluation of welding workability in Table 3 is as follows:
◎: Very good, 〇: Good, △: Slightly poor, ×:
This indicates a defect.

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〔Effect of the invention〕

As described above, the present invention improves the flux composition of flux-cored wire for stainless steel welding by
By specifying the range of SiO ₂ −ZrO ₂ −TiO ₂ components that exhibit sufficient slag encapsulation and peelability even with a small amount of slag, it is possible to reduce the amount of spatter generated.
Furthermore, by increasing the content of metal components in the flux, arc conditions and droplet migration properties have been improved, making it possible to reduce the work of removing spatter after welding, which greatly improves the work efficiency of stainless steel welding. It is something that contributes.

[Brief explanation of drawings]

FIGS. 1a, b, c, and d are schematic diagrams showing the cross-sectional shapes of various flux-cored wires, and FIG. 2 is a diagram showing the relationship between the content of slag components in the wires and the amount of spatter generated. 1... Outer skin, 2... Filling flux, 3... Seam.

Claims (1)

[Claims] 1 1.5-3.7% SiO ₂ based on the total weight of the wire, 0.7-
The flux contains 2.0% _ZrO2 , 0.7~4.2% _TiO2 , 0.1~0.7% metal fluoride, and 0.3~2.3% Mn, and the total slag component in the flux is 4.5% of the total weight of the wire. ~9.5%, and the total metal content in the flux is 59% of the total weight of the flux.
A flux-cored wire for stainless steel welding, which is characterized in that it accounts for ~85% and contains substantially no carbonates.