JPH02235597A - Wire for gas shielded arc welding of galvanized steel sheet - Google Patents

Abstract

PURPOSE:To form weld beads free from pits and blowholes by forming the flux of the flux cored wire for welding galvanized steel sheets of a mixture composed of Fe as an essential component and a deoxidizing agent and arc stabilizer and incorporating specific ratios of few C, P, Zr or further Ti and Nb into the wire. CONSTITUTION:The flux compsn. of the flux cored wire used at the time of gas shielded arc welding of the galvanized steel sheets is constituted of the mixture composed, by weight%, of 65 to 90% Fe, 5 to 30% deoxidizing agent consisting of Si, Mn and the iron alloy thereof, and 0.1 to 10% arc stabilizer consisting of an alkaline metal and Li or the compd thereof and the flux fills a steel sheath at 10 to 35% flux rate. Also, 0.10 to 0.30% C, 0.025 to 0.15% P, and 0.01 to 0.15% Zr are used as the essential components or further one or two kinds of 0.01 to 0.15% Ti and 0.01 to 0.15% Nb are incorporated into the flux or the steel sheath.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a flux-cored wire for welding galvanized steel, and particularly relates to a flux-cored wire for welding galvanized steel (hereinafter referred to as "galvanized steel") whose surface is plated with zinc or an alloy containing zinc. This is a flux-cored wire that can minimize the occurrence of pores such as pits (pores that appear on the surface of the weld metal) and blowholes (pores that exist inside the weld metal) when welding. be.

(Conventional technology) In recent years, the use of galvanized steel sheets has been rapidly expanding in the automobile and housing industries in order to improve the durability of steel sheets and steel materials from the perspective of corrosion protection. In the automobile industry, the purpose is to improve the rust resistance against salt spraying as an antifreeze agent in cold regions such as North America, and in the housing industry, the purpose is to improve the rust resistance of lightweight steel-framed houses.

Although galvanized steel sheets have these excellent properties, compared to regular steel sheets that have not been surface treated,
The problem is that its weldability (mainly porosity resistance and amount of spatter generation) is extremely poor. Therefore, at present, coated arc welding or solid wire is used, and low speed welding (3
(approximately 0 cm/min) or welding with a gap between steel plates (0.5 m/min)
This has been dealt with mainly through construction techniques based on experience. (Problems to be Solved by the Invention) As described above, in conventional arc welding of galvanized steel sheets, coated arc welding rods or solid wires are used, low-speed welding or welding with gaps between the steel sheets, etc. This has been used to deal with the occurrence of pores (pits, blowholes, etc.) and an increase in the amount of spatter generated. However, in such construction, efficiency is low because the welding speed is slow, and defects such as burn-through and undercut are likely to occur due to the so-called gaps between the plates.

On the other hand, an increase in welding speed and a decrease in the gap between steel sheets will lead to an increase in the number of pores and an increase in the amount of spatter generated. Various studies have pointed out that this is due to the influence of zinc in the layer.

That is, when galvanized steel sheets are arc welded, many pores are generated in the weld metal due to zinc vapor decomposed and dissipated by arc heat, which may significantly deteriorate the mechanical properties of the welded joint. In addition, with regard to welding workability, there is a problem in that the arc is disturbed due to the influence of zinc vapor, increasing the amount of spatter generated, and the welding work efficiency is significantly reduced due to the removal work. Furthermore, there is also the problem that zinc turns into zinc oxide due to arc heat, increasing welding fumes.

The present invention was made in view of this situation, and includes:
When arc welding galvanized steel sheets, even if the welding speed is higher than before and the gaps between the steel sheets are small or non-existent, there are extremely few pores such as pits and blowholes in the weld metal, and welding workability is further improved. It is an object of the present invention to provide a flux-cored wire for arc welding galvanized steel plates that generates less spatter on both surfaces.

(Means for Solving the Problems) In order to achieve the above object, the present inventors first investigated the effect of the amount of zinc in the plating layer (hereinafter referred to as "zinc basis weight") on the generation of pores (bits, blowholes, etc.). and the effects of welding conditions were investigated. As a result, it was found that the amount of zinc vapor generated by arc heat and the difficulty of releasing zinc vapor from the molten metal into the atmosphere greatly influenced the number of pores.

That is, when the zinc basis weight is less than 1°, naturally the amount of pan lead vapor generated is small, and the number of pores generated thereby is also small. In addition, if it is extremely difficult to release zinc vapor into the atmosphere, for example, if the viscosity or cooling rate of the molten metal is extremely high and the generation, growth, and floating of zinc vapor in the molten metal is suppressed, pores may be The number of occurrences will decrease. On the other hand, when release into the atmosphere is extremely easy, for example, when the viscosity or cooling rate of the molten metal is very low, it is easy for zinc vapor to grow, float, and release into the atmosphere in the molten metal.
The number of pores will decrease. Based on these phenomena, and as a result of further intensive research, we found that the characteristics that the wire should have are: 1. In order to suppress the generation of zinc vapor, the penetration depth should be shallow.

■Improve the stability of the arc (the number of droplet transfer short circuits, etc.) to promote stirring of the molten pool in order to facilitate the floating of zinc vapor in the molten metal.

■Reducing the amount of slag generated to facilitate the release of zinc vapor from molten metal.

■In order to prevent molten zinc from vaporizing, a component that forms a compound with zinc is added to the wire. ■In order to suppress the generation and growth of zinc vapor, the viscosity is increased by lowering the amount of oxygen in the molten metal or adding trace components.

As a welding material, we found that it has excellent porosity (bit, blowhole) resistance, and has a practical level of spatter generation, arc stability, slag generation, bead appearance shape, etc. This led to the invention of a wire for gas-shielded arc welding for galvanized steel sheets that can be suppressed to within a problem-free range.

That is, the wire for gas-shielded arc welding of galvanized steel sheets according to the present invention contains 65 to 90% Fa, 5 to 30% deoxidizer mainly composed of Si and Mn, and 0.1 to 10% arc stabilizer. A flux-cored wire in which a steel shell is filled with flux at a flux rate of 10 to 35%, and C: 0.10 to 0.30% based on the total weight of the wire. P:0.025
~0.15% and Zr: 0.01~0.15% as essential components, and optionally further contains Ti: 0.01~0.
．． 15% and Nb: 0.01 to 0.15% or 2
It is characterized by containing seeds as an essential component.

The present invention will be explained in more detail below.

(1) Type of wire As a wire for gas-shielded arc welding of galvanized steel sheets, first of all, to suppress the generation of zinc vapor, use a flux with a shallower penetration depth than solid wire, as shown in Figure 1. Cored wire is suitable.

In addition, in order to stir the molten pool and promote the floating and release of zinc vapor, as shown in Figure 1, it is necessary to improve the arc stability (droplet transfer, number of short circuits, etc.) by adding trace amounts of elements rather than solid wire. Franx-cored wire, which has excellent properties, is more suitable.

Table 1 shows the results using a 1.2 mmφ solid wire (JI SYGWI 2) and a metal flux-cored wire (JISYGW 24), and using a shielding gas (100% CO, 20 Q/min). , thyristor controlled power supply, 120AX17~18V
X 60 c+a/win, protrusion length 15mm,
Under the welding conditions for the lap fillet joint shape shown in Figure 2,
Zinc weight: 90/90g/m”, plate thickness: 2.3m
m galvanized steel plates are welded, and the result (penetration depth,
This is an example comparing the arc stability and porosity of solid wire and wire with flags.

Furthermore, in order to reduce the amount of slag generated and promote the release of zinc vapor from the molten pool to the atmosphere, metal flux-cored wire is preferable to titania-based flag-cored wire, as shown in Figure 3. Are suitable.

Here, FIG. 3 shows a solid wire (JI SYGW 2) of 1.2lφ, a metal flag-cored wire (JISYGW24), a titania-based flux-cored wire (J r SYGW24), and 2.
O nhmφ's Senorefushi Noredwire (Jcho SYF
W11) and 3.2mmφ coated arc welding rod (JIS
D4313), and in the case of gas-shielded arc welding, a shielding gas (100% CO, 20Q/sin) was used, a thyristor-controlled power source was used, and the welding conditions were 1.
For 2m+aφ wire: 1 20AX60cm/+m
in, 200AX60c for 2.0mmφ wire
/win, 100AX40 for coated arc welding rods
cm+/■in, under the conditions of the lap fillet joint shape shown in Figure 2, the zinc weight is 90/90g/ugly 2.
This is an example of welding galvanized steel plates with a thickness of 2.3s+m and comparing the results (number of blowholes and bits). Therefore, in the present invention, a metal flux-cored wire is used as the wire.

(2) Amount of Fe in flux: 65 to 90% In order to have the characteristics of the metal flux-cored wire described above, first, the amount of iron powder in the flags must be 6S to 90%. If it is less than 65%, the amount of slab generated increases due to the increased content of deoxidizers, arc stabilizers, etc., which prevents the release of zinc vapor into the atmosphere and makes it easier for pores (pits) to occur. %, the content of deoxidizing agent or arc stabilizer will be insufficient, and the viscosity of molten metal will decrease, and the stability of arc and droplet transfer will decrease, resulting in the generation of pores (pits, blowholes) and spatter. The amount increases.

Therefore, 65 to 90% of iron powder should be contained in the flux. (3) Deoxidizing agent in flux = 5 to 30% Adjusts the viscosity of molten metal and the amount of slag generated to control the growth, floating, and release of zinc vapor to the atmosphere, forming pores (bits, blowholes) In order to control the generation of spatter, welding workability such as bead appearance and shape, and mechanical performance such as strength and toughness of the weld metal within a range that does not cause any practical problems, desorption is added during flux. Contain 5-30% of acid agent.

Note that Si and Mn are mainly used as the deoxidizing agent, but there are no particular restrictions.

However, if the content of the deoxidizing agent in the flux is less than 5%, the viscosity of the molten metal decreases due to an increase in the amount of oxygen in the molten metal, and the number of pores (pits, blowholes) increases. In addition, when the content is extremely low, the viscosity of the molten metal becomes extremely low, making it easier for zinc vapor to float to the surface, reducing the number of pores (blowholes).
The viscosity of the droplets also decreases, making them more likely to scatter due to zinc vapor during the transition from the wire to the molten pool.
The amount of spatter generated increases. Furthermore, insufficient deoxidation may lead to poor bead appearance, reduced toughness of weld metal, or Si. Problems such as a decrease in the strength of the weld metal due to insufficient content of Mn etc. occur.

Moreover, when it exceeds 30%, the amount of slab generated increases, which prevents zinc vapor from being released into the atmosphere, and increases the number of pores (pits). Also, Si in the weld metal. Since the yield of Mn increases, the strength becomes too high and the toughness decreases as a result.

Therefore, the deoxidizer should be contained in the flux in an amount of 5 to 30%.

In addition, Si. Deoxidizing agents such as Mn can be added alone to the flux, or they can be added to the flux as well as Fe-Si, Fe-M, Fe-S
i-Mn. It may be added as a compound such as Fe-Si-Zr. Furthermore, it may be added to the outer metal.

(4) Arc stabilizer in flux 20.1 to 10% In order to suppress arc instability caused by zinc vapor, reduce the amount of spatter, and stabilize the bead appearance and shape, Stabilizer in Flags 0.1-1
Contain 0%. As the arc stabilizer, alkali metals, lithium, or their compounds are mainly used, but there are no particular restrictions. However, the content of arc stabilizer in the flux is 0.1
If it is less than %, the arc becomes unstable, resulting in increased spatter generation and poor bead appearance and shape. Also,
If it exceeds 10%, the amount of slab generated increases, which prevents zinc vapor from being released into the atmosphere and increases the number of pores (bits).

Therefore, the arc stabilizer is 0.1 to 1
0% shall be added.

(5) Flux rate = 10 to 35% To obtain the characteristics of the metal flag-cored wire shown in (1) using a flux consisting of the above components (2) to (4), the flux rate (wire The ratio of flux weight to weight must be 10 to 35%. If the flux rate is less than 10%, the characteristics of a flux-cored wire, such as shallower penetration depth and superior arc stability compared to solid wire, will decrease, resulting in the occurrence of pores (pits, blowholes). The effect of suppressing or reducing the amount of spatter generated is reduced. On the other hand, when the flux rate exceeds 35%, the content of the deoxidizing agent and the arc stabilizer increases, so the amount of slab generation increases, and the effect of suppressing the generation of pores (pits) decreases. Also, since the outer metal becomes thinner, the current density increases there, and the melting of the outer metal precedes the melting of the flux. This makes the arc and droplet transfer unstable.

Therefore, the flux rate should be 10 to 35%. (6) Amount of C in the whole wire: 0.10-0.30% As is clear from Figure 4, the carbon in the wire (in the sheath metal and/or flux) is C○ or C in the molten metal. C.O.
It has the effect of stirring the molten pool by causing a deoxidizing reaction that generates two gases, and by stabilizing the transfer of droplets from the wire to the molten pool. This action promotes the floating of zinc vapor in the molten metal and its release into the atmosphere, reducing the number of pores (pits, blowholes). For this reason, the amount of C in the total wire is set to 0.10 to 0.30%. However, if the amount of C in the total wire is less than 0.10%, the above-mentioned stirring action of the molten pool will not be sufficient, and no effect will be seen in reducing the number of pores (pits, blowholes). Also, 0.30
%, the amount of C○ or C○2 gas generated increases, and conversely, pores are generated due to them. Furthermore, the droplets explode due to the pressure of these gases generated in the droplets, increasing the amount of splatter and fume generated.

Therefore, the amount of C in the whole wire is 0.10-0.30%
shall be.

Note that carbon may be added to the flux as a single carbon element, or may be added in the form of being contained in other raw materials such as Fe-Mn-C. Furthermore, it may be added to the outer metal.

Here, FIG. 4 shows 1.2+IIlφ with the amount of C changed.
Welding conditions were 12 using a metal flux-cored wire, shielding gas (100% CO2, 20 Q/win), and a thyristor-controlled power source.
0 A x 6 0cm/win. Under the conditions of the lap fillet joint shape shown in Figure 1, the zinc weight is 90/90.
This is an example of welding a sub-button-plated steel plate with a g/II of 12 and a thickness of 2.3 cm, and examining the results (number of blowholes and pits) in relation to the C content. (7) P content in all wires: 0.025~0.15%
As is clear from FIG. 5, P in the wire forms stable compounds (P-Zn series, P-Zn-Fe series, etc.) with zinc at temperatures above the melting point of zinc.

As a result, the amount of zinc vapor generated decreases and pores (pits,
The occurrence of blowholes is suppressed. For this purpose, P is contained in the total wire in an amount of 0.025 to 0.15%. However, the amount of P in the whole wire is less than 0.025% (usually 0.010 to 0.02 when not intentionally added).
When the zinc content is about 0%), the amount of compounds formed with zinc is insufficient, so the effect of suppressing the generation of pores is extremely small. In addition, if it exceeds 0.15%, the amount of P concentrated in the final solidification region of the molten metal increases, making it more susceptible to cracking (especially hot cracking), and increasing the welding conditions, groove gap (root gap), etc. ), cracks may occur depending on the construction conditions.

Therefore, the content of P in the whole wire is 0.025~0
．． 10%.

Note that phosphorus may be added to the flux as a single phosphorus substance, or may be added in the form of being contained in other raw materials such as Fe--P. Furthermore, it may be added to the outer metal.

Here, Fig. 5 shows the results (blowholes, pits, This is an example in which the number of occurrences) was investigated in relation to the amount of P.

(8) (7) Zr amount in all wires: O. O L-0.1
5% As is clear from FIG. 6, Zr in the wire, like P, forms stable compounds with zinc (Zr--Zn system, etc.) at temperatures above the melting point of zinc. Therefore, the amount of zinc vapor generated is reduced, and the generation of pores (pits, blowholes) is suppressed. Furthermore, since Zr has a deoxidizing effect, it works to lower the amount of oxygen in the molten metal and increase its viscosity. Furthermore, Zr itself has the effect of increasing the viscosity of molten iron. As the viscosity of the molten metal increases in this way, the growth of zinc vapor is suppressed and the number of pores (pits, blowholes) is reduced. For this purpose, Zr was added in the wire to 0.
0 1 to 0.15%.

However, if the amount of Zr in the total wire is less than 0.01%, the amount of compounds formed with zinc is small, so the amount of zinc vapor generated hardly decreases. Also, the increase in viscosity of the molten gold shoulder is not sufficient to suppress the growth of zinc vapor. Therefore, it is not effective in reducing the number of pores (pits, blowholes). Moreover, if it exceeds 0.15%, slag due to Zr oxide increases, which prevents release of zinc vapor from the molten metal to the atmosphere and increases the number of pores (pits). In addition, the diameter of the droplet increases due to its increased viscosity.
The transition to the molten pool becomes unstable due to the influence of zinc vapor,
It tends to scatter as large spatter particles. In other words, it is not effective in reducing the number of pores (pits) generated, and conversely it reduces welding workability in terms of the amount of spatter generated and droplet transfer.

From the above, Zr is contained in the entire wire in an amount of 0.01 to 0.15%.

Note that Zr may be added alone to the flux, or may be added as a compound or other Fe-Zr-Si. It may be added in the form of a raw material such as Fe-Zr. Furthermore, it may be added to the outer skin metal. Here, in Fig. 6, 1.2lφ metal flux-cored wire with varying Zr content is used, and the other conditions are as follows.
This is an example in which the results (the number of blowholes and pits) were investigated in relation to the Zr content in the same way as the test shown in the figure.

Regarding only the reduction in the number of pores (pits, blowholes), when the zinc basis weight is small (for example, 10 to 3
0g/♂) contains C. P. Effects can also be obtained by adding each element of Zr alone. However, when the amount of zinc per unit area is large (for example, 60 to 90 g/m2), the effect is insufficient when added alone, and a practically sufficient effect is obtained when added in combination.

(9) Ti content in all wires: 0.01 to 0.15%, Nb content in all wires: 0.01 to 0.15% More resistant to the above-mentioned C-P-Zr system. If it is necessary to improve porosity or increase the strength of weld metal, add 0.01 to 0.15% Ti to the entire wire and 0.01 to 0.1% Nb to the entire wire.
~0.15% of one or both of them is contained. These Ti
Like Zr, both Nb and Zn form compounds with zinc and increase the viscosity of molten metal, so they are effective in reducing the number of pores (pits, blowholes).

However, the content of Ti and Nb in the whole wire is 0, respectively.
．． If it is less than 0.01%, the amount of zinc vapor generated will not be sufficiently reduced because the amount of compounds formed with zinc will be small. Also, the increase in viscosity of the molten metal is not sufficient to suppress the growth of zinc vapor. For this reason, pores (bits, blowholes)
No effect was observed in reducing the number of occurrences.

Moreover, when the Ti content exceeds 0.15%, slag due to Ti oxide increases, which prevents release of zinc vapor from the molten metal to the atmosphere and increases the number of pores (pits). Furthermore, since the amount of Ti oxides remaining in the weld metal increases, the mechanical performance of the weld metal, such as crack resistance, deteriorates.

In addition, Nb has the effect of increasing the strength of the weld metal, but if it is contained in an amount exceeding 0.15%, it becomes excessive and the mechanical performance such as elongation and toughness of the weld metal deteriorates. From the above, it is assumed that one or two types of Ti and Nb are contained in the whole wire in the range of 0.01 to 0.15%, respectively, as necessary.

Note that Tj and Nb may be added alone to the flux, or may be added in the form of a compound or other raw materials. Furthermore, it may be added to the outer shell metal.

These elements (C.P.
Zr, Ti. Nb) can be contained in either the flux or the outer metal, or both. The flux-cored wire having the above composition is mainly used for mild steel and 50 kgf/am'' class high-strength steel, but there are no particular restrictions on the steel type, and there are no restrictions on the cross-sectional shape of the wire. , for example, FIG. 7(A).
(B). (C). Various shapes such as those shown in CD) can be used. The wire diameter and shielding gas composition also vary depending on the application: 0.8+imφ, 1.2IIIlψ, 1.
4mmφ, 1.6mmφ, 2. It can be arbitrarily selected from wires such as Q mmφ, 100% CO2, Ar-Co, mixed gas, etc.

Furthermore, although there are no particular restrictions on the welding power source, as shown in Figure 8, by using an inverter power source that is effective in maintaining arc stability, it is possible to improve porosity resistance and reduce the amount of spatter generated. In this respect, the effects of the present invention are further exhibited, which is preferable.

Here, FIG. 8 shows l. Using 2n++aφ metal franked wire, shielding gas (100% CO
2.80%Ar+20%CO,,20Q/mi
n), 120A x 60cm/win
, under the conditions of the lap fillet joint shown in Fig. 2, using various power supplies, the zinc weight is 90/oz/m'' and the plate thickness is 2.
．． This is an example of welding 3■ galvanized steel sheets and examining the results (number of blowholes and pits) in relation to the type of power source. Next, examples of the present invention will be shown.

(Example) Flux-cored wires having the compositions and flux rates shown in Tables 1 and 2 were manufactured. In addition, the wire diameter is 1.21II
lφ, and mild steel was used for the outer skin metal. Therefore, C.
P. Zr. Ti and Nb were mainly added and adjusted from Flags. In addition, Fe is iron powder, and deoxidizers are Si and Mn.
iron alloy was used.

Using these wires, a gas shield arc welding test was conducted according to the following welding procedure.

Welding instructions> ・Wire: Metal flux-cored wire, 1.20I
Illφ ・Shield gas: 100% C○2, 2 0 Q /wi
n・Steel plate: sub-button weight 90/90g/m”, plate thickness 2.3+am・Joint shape double fillet (see Figure 2)・Welding conditions:
l 2 0 A amount, cracking resistance, etc.) are also listed in each table.

As is clear from each table, even at high welding speeds, all the examples of the present invention have extremely few pores such as pits in the weld metal, have good arc stability, good bead appearance, and have little spatter and slag. , exhibiting excellent welding workability. [Blank below] (Effects of the Invention) As detailed above, according to the present invention, when arc welding galvanized steel sheets with various zinc coating weights, it is possible to arc weld galvanized steel sheets with various zinc coating weights at a higher welding speed than before, and with the gap between the steel sheets being minute or smaller. Even in the case where there are no pores such as pits and blowholes in the weld metal, excellent welding workability can be obtained, such as very few pores such as pits and blowholes, and a small amount of spatter generated.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the penetration depth and arc stability in the case of gas-shielded arc welding using solid wire and metallic flux-cored wire, and the photograph in the figure is a photograph showing the macrostructure of the weld metal. Figure 2 shows the joint shape and lap fillet welding procedure, Figure 3 shows the relationship between various welding wires and penetration depth, and Figure 4 shows the amount of carbon in the whole wire and pores (pits, blowholes). Figure 5 is a diagram showing the relationship between the amount of P in all wires and the number of pores (pits, blowholes) generated, and Figure 6 is a diagram showing the relationship between the amount of Zr in all wires and the number of pores (pits, blowholes) generated. 1., Broichi Hall)
A diagram showing the relationship between the number of occurrences, Figures 7 (A) to (D) are diagrams showing examples of cross-sectional shapes of flux-cored wires, and Figure 8 shows pores (pits, blowholes) when using various power sources.
It is a figure showing the number of occurrences. DESCRIPTION OF SYMBOLS 1... Test plate (galvanized steel plate), 2... Galvanized layer, 3... Torch, M... Shell metal, F... Flux. Patent Applicant: Kobe Steel, Ltd. Patent Attorney Takashi Nakamura (A) Figure Figure (B) Figure Figure Amount in Gold Wire? wGノζ■冫目图电解、／）Dan I Jhihishirubusu

Claims (2)

[Claims] (1) 65 to 90% Fe in weight% (the same applies hereinafter);
A steel shell is filled with a flux containing 5 to 30% of a deoxidizing agent mainly composed of Si and Mn and 0.1 to 10% of an arc stabilizer so that the flux rate is 10 to 35%. A flux-cored wire, and
Per total wire weight, C: 0.10-0.30%, P: 0
．． 025-0.15% and Zr: 0.01-0.15%
A wire for gas-shielded arc welding of galvanized steel sheets, characterized by containing as an essential component. (2) The flux-cored wire further includes Ti: 0.01 to 0.15% and Nb: 0.0% based on the total weight of the wire.
The flux-cored wire according to claim 1, which contains 1 to 0.15% of one or two kinds as essential components.