JP3082119B2 - Gas shielded arc welding method of galvanized steel sheet and galvanized steel sheet product welded by the welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas shielded arc welding method suitable for welding galvanized steel sheets and a galvanized steel sheet product welded by the welding method.

[0002]

2. Description of the Related Art In recent years, steel sheets having a surface plated with zinc or a zinc alloy (hereinafter referred to as galvanized steel sheets) have a high corrosion resistance,
Because of its excellent weather resistance, it is used for automotive parts, steel frame members for buildings, and the like, and its demand is increasing year by year.

[0003] Short-gap transfer welding (carbon dioxide welding, MAG welding) and pulsed MAG welding are generally widely used for welding galvanized steel sheets. When performing these arc welding, the zinc plated on the steel sheet surface has a lower melting point than iron, the zinc vaporizes, and this steam zinc tries to diffuse outside through the molten pool and the molten metal, When the solidification rate of the molten metal is high, the vapor zinc is not sufficiently diffused outside and remains as bubbles in the weld metal and on the surface of the weld metal. This steam zinc causes welding defects such as blowholes and pits (hereinafter, referred to as pores). In addition, the generation of steam zinc disturbs the arc and causes a large amount of spatter.

As described above, when a galvanized steel sheet is subjected to short-circuit transfer welding, spatter and porosity are remarkably generated, but when pulse MAG welding is performed, spatter generation is reduced as compared with short-circuit transfer welding. You. Further, since the heat input is large, the diffusion of zinc vapor is promoted, and the generation of pores is suppressed. However, since this heat input is large, it is difficult to cope with welding of a thin plate material while promoting generation of welding defects such as undercut.

[0005] The occurrence of such pores, undercuts, and spatters not only deteriorates the welding quality, but if the frequency of occurrence of these pores, undercuts, and spatters becomes unacceptable, it is necessary to modify the welded portion. In the case where rework cannot be performed, the member may be discarded, resulting in a reduction in work efficiency and a significant uneconomical situation.

[0006] As described above, pulse MAG is also used for short-circuit transfer welding.
Each of the weldings also had disadvantages. Therefore, at present, low-speed welding with a relatively low speed or welding with a gap between steel sheets is performed for the occurrence of pores and spatter, and the welding voltage is reduced for the occurrence of undercut, etc. They responded mainly by devising construction work based on their experience.

[0007]

As described above, in conventional arc welding of galvanized steel sheet, the efficiency is low due to low-speed welding, and defects such as burn-through and undercut are easily generated due to gaps between the steel sheets. . When the welding voltage was lowered, the amount of spatter increased.

[0008] The present invention solves the above-mentioned problems. In arc welding of a galvanized steel sheet, a gas capable of suppressing the generation of pores, spatters and undercuts at a higher welding speed than in the past. An object of the present invention is to provide a shielded arc welding method and a galvanized steel sheet product welded by the welding method.

[0009]

In order to solve the above-mentioned problems, the present invention according to claim 1 provides a method for controlling the degree of vaporization of zinc.
This is a gas shielded arc welding method including a pulse MAG welding process in which a pulse current in a welding current region lower than usual is superimposed, followed by a short-circuit transfer welding process.

According to a second aspect of the present invention, there is provided the welding method according to the first aspect, wherein the shielding gas contains
A gas shielded arc welding method characterized by mixing 7% by volume of oxygen gas.

[0011] Further, in the invention according to claim 3, zinc is a gas.
This is a galvanized steel sheet product obtained by welding by pulse MAG welding in which a pulse current in a welding current region lower than the normal level is superimposed, followed by short-circuit transfer welding.

[0012]

According to the gas shielded arc welding method for galvanized steel sheet of the present invention, diffusion of zinc vapor is promoted by performing pulsed MAG welding in a relatively low welding current region to remove zinc from the surface layer of the galvanized steel sheet. . Subsequently, the surface portion of the steel sheet from which zinc has been removed is short-circuited and transferred to obtain a bead having less spatter and having no welding defects such as pores and undercuts.

Further, when oxygen gas is mixed into the shielding gas, the viscosity of the molten metal is reduced, and the transfer of droplets is facilitated.
Suppresses arc disturbance. For this reason, the generation of spatter is suppressed, the diffusion of the vapor zinc from the molten portion to the outside is promoted, and the generation of pores is suppressed.

[0014]

【Example】

(Embodiment 1) An explanatory schematic diagram of a welding method according to an embodiment of the present invention is shown in FIG. In the figure, reference numeral 1 denotes a state of pulse MAG welding performed in advance, and subsequently, a state of short-circuit transfer welding is denoted by 2
Indicated by

[0015] In the pulse MAG welding, the welding current region is set relatively low to promote the diffusion of zinc vapor generated in the surface layer of the galvanized steel sheet, and to generate a large amount of spatter and generate zinc. Is removed. This allows
In the short-circuit transfer welding performed in the subsequent step 2, welding is performed while the generation of these spatters and pores is suppressed. Further, since the heat input to the base material is reduced, the occurrence of undercut is also suppressed. The shielding gas was mainly composed of a mixed gas of argon gas and carbon dioxide gas.

(Example 2) 2-7% by volume of oxygen gas was mixed in the shielding gas used in the welding method of Example 1 described above.

The mixing of the oxygen gas lowers the viscosity of the molten metal, facilitates the transfer of droplets, and suppresses arc disturbance. For this reason, the generation of spatter is suppressed, the diffusion of steam zinc from the molten portion to the outside is promoted, and the generation of pores is suppressed. If the amount of oxygen gas is too large, the viscosity of the molten portion is too low, and conversely, the molten pool is disturbed, which promotes the generation of spatters and pores. For this reason, good results were obtained when the mixing ratio of oxygen gas was 2 to 7% by volume.

[0018]

As is apparent from the above description, the present invention has the following effects.

(1) The generation of spatters, pores and undercuts can be suppressed, so that the welding quality can be improved.
A method of welding a galvanized steel sheet that can maintain good welding workability by suppressing a decrease in bead appearance, eliminating a reduction in work efficiency such as spatter removal work and repairing a welded portion, and the like can be realized.

(2) By reducing the heat input to the base material, the range of application to welding of a thin plate material can be expanded.

(3) A welded galvanized steel sheet product with few pores and undercuts can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a welding method according to an embodiment of the present invention.

[Explanation of symbols]

 1 Pulse MAG welding 2 Short circuit transfer welding

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-143775 (JP, A) JP-A-61-56777 (JP, A) JP-A-60-255276 (JP, A) JP-A-6-255276 142934 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 9/23 B23K 9/073 B23K 9/09 B23K 9/16 B23K 9/173

Claims (3)

(57) [Claims] In a consumable electrode type welding method in which welding is performed using a gas containing an argon gas or a carbon dioxide gas as a shielding gas, a welding current region lower than a normal level in which zinc is vaporized.
A method of gas-shielded arc welding of galvanized steel sheet, comprising a pulse MAG welding step in which a pulse current is superimposed and a short-circuit transfer welding step. 2. The method according to claim 1, wherein 2 to 7% by volume of oxygen gas is mixed with the shielding gas for welding. 3. A welding electrode having a lower than usual level of vaporization of zinc.
A galvanized steel sheet product which is welded by short-circuit transfer welding, followed by welding by pulse MAG welding in which a pulse current in a flow region is superimposed.