JP2013248621A - Welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve low sputtering and few pore relating to welding of a galvanized steel sheet.SOLUTION: A welding method for welding a surface-treated member includes a first step of plasma welding to remove the surface treatment of the member, and a second step of GMA welding following the first step, wherein the GMA welding of the second step is pulsed GMA welding, by which an arc generated by the plasma welding of the first step is shaken and the surface treatment of the member is removed.

Description

  The present invention relates to a welding method that is effective in reducing spatter, blowholes, and pits when welding a surface-treated member such as a galvanized steel sheet.

  In recent years, since galvanized steel sheets are excellent in rust prevention and corrosion resistance, they are used for automobile parts, building steel members and the like, and their demand is increasing year by year.

  However, there are problems with the use of galvanized steel sheets. Zinc plated on the steel sheet surface has a lower melting point than iron. Therefore, when the galvanized steel sheet is welded, the zinc is vaporized. And zinc vapor | steam tries to spread | diffuse outside through a molten pool and a molten metal. When the solidification of the molten metal is fast, zinc vapor cannot be diffused to the outside and remains as blowholes or pits (hereinafter referred to as pores) in the weld metal or on the weld metal surface. These can also lead to serious weld defects. Zinc vapor also disturbed the arc and caused a large amount of spatter.

  Regarding welding of galvanized steel sheets, residual zinc vapor and bumping are prevented by various methods, and welding defects such as pores are reduced. For example, it is known that welding is performed by pulse GMA welding in which a pulse current in a welding current region lower than usual at which zinc is vaporized is superimposed, and then welding is performed by short-circuit transfer welding (for example, Patent Documents). 1). As shown in FIG. 6, the diffusion of zinc vapor is promoted by the preceding pulse GMA welding to remove zinc from the surface layer of the galvanized steel sheet. However, this was less effective for lap welding.

  With regard to lap welding of galvanized steel sheets, a method is known in which zinc vapor is released by providing a gap between the steel sheets (see, for example, Patent Document 2). In addition, a method of previously deforming a welding work is also known (see, for example, Patent Document 3). However, these methods include practically useless processes and the like, and are difficult to implement in practice.

Japanese Unexamined Patent Publication No. 7-9148 JP 2003-334681 A JP 2003-31453 A

  The above-described conventional galvanized steel sheet welding methods have a problem that the effect is low with respect to lap welding and a problem that it is difficult to realize in practice.

  An object of the present invention is to provide a welding method for a galvanized steel sheet that is widely applied to welding workpieces of various galvanized steel sheets and realizes low spatter and low porosity.

  In order to solve the above problems, the welding method of the present invention is a welding method for welding a member subjected to surface treatment, and a first step of performing plasma welding to remove the surface treatment of the member; A welding method comprising a second step of performing GMA welding subsequent to the first step, wherein the surface treatment of the member is removed by swinging an arc generated by the plasma welding of the first step. Is.

  In the welding method of the present invention, in addition to the above, the GMA welding in the second step is pulse GMA welding, and the arc generated by the plasma welding in the first step is oscillated by performing the pulse GMA welding. It is something to be made.

  In addition to the above, the welding method of the present invention is a welding method for welding the overlapped portion of two members subjected to surface treatment, and only the upper plate is melted by plasma welding in the first step. By doing so, the surface treatment of the overlapping portion of the two members is removed by heat that melts the upper plate.

  In the welding method of the present invention, in addition to the above, the surface-treated member is a galvanized steel sheet.

  As described above, according to the present invention, the first step of performing plasma welding to remove the surface treatment of the member, and the second step of performing GMA welding subsequent to the first step are provided. The GMA welding in this step is pulse GMA welding, and by performing pulse GMA welding, the arc generated by the plasma welding in the first step is swung to remove the surface treatment of the member. Thereby, low spatter and low pores can be realized in welding of a surface-treated member such as a galvanized steel sheet.

The figure which shows the outline of the state which is performing the welding method in Embodiment 1 of this invention The figure which shows the direction of the electric current and magnetic field in Embodiment 2 of this invention The figure which shows the relationship of the arc of plasma welding and pulse GMA welding in Embodiment 2 of this invention. The figure which shows the part which overlaps when the two galvanized steel plates in Embodiment 3 of this invention are piled up The figure which shows the volatilization direction of the surface treatment of the overlapping part of the two galvanized steel plates in Embodiment 3 of this invention The figure which shows the outline of the state which is performing the conventional welding method

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 is a diagram showing an outline of a state in which the welding method in the first embodiment is performed. FIG. 1 shows a state in which a first galvanized steel plate 3 and a second galvanized steel plate 4 are stacked as an example of a surface-treated member. And the state which is welding with respect to this 1st galvanized steel plate 3 and the 2nd galvanized steel plate 4 using the 1st welding torch 1 and the 2nd welding torch 2 is shown.

  Here, the first welding torch 1 is moved ahead of the second welding torch 2 in the welding progress direction. The second welding torch 2 is moved behind the first welding torch 1 with respect to the welding progress direction, and performs welding following the first welding torch 1. The first welding torch 1 performs plasma welding. The second welding torch 2 performs GMA welding, more specifically, pulse GMA welding.

  In FIG. 1, by performing plasma welding with the first welding torch 1, the weld joint between the first galvanized steel plate 3 and the second galvanized steel plate 4 is melted. Thereby, the zinc in the surface of the 1st galvanized steel plate 3 and the 2nd galvanized steel plate 4 is volatilized. Zinc causes a large amount of spatter and pores.

  By doing in this way, in the pulse GMA welding by the 2nd welding torch 2 performed following the plasma welding by the 1st welding torch 1, the surface of the 1st galvanized steel plate 3 and the surface of the 2nd galvanized steel plate 4 is used. Welding can be performed with less zinc. Therefore, welding can be performed in a state close to that in the case of welding a steel plate that has not been surface-treated.

  In addition, what is necessary is just to perform the plasma welding performed using the 1st welding torch 1 on the welding conditions which can evaporate the zinc which is a surface treatment. And this welding condition should just obtain | require by experiment etc. previously according to a welding target object, for example.

  As described above, according to the first embodiment, by causing plasma welding to precede, zinc which causes a large amount of spatter and pores is volatilized, and in pulse GMA welding subsequent to plasma welding, zinc on the surface of the steel sheet is used. Therefore, it is possible to perform welding in a state where there is a small amount, and it is possible to reduce generation of spatter and pores.

  In the first embodiment, the first welding torch 1 and the second welding torch 2 are each a relative of two welding torches such as a welding torch used for generally known tandem welding. The position may be fixed, and welding may be performed by attaching to an industrial robot. Alternatively, two industrial robots are used, the first welding torch 1 is attached to one industrial robot, the second welding torch 2 is attached to the other industrial robot, and the two industrial robots are operated. Welding may be performed.

(Embodiment 2)
In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The main difference from the first embodiment is that the first galvanizing is performed over a wide range by swinging the preceding plasma welding arc in the front-rear direction with respect to the welding direction or in the oblique front-rear direction with respect to the welding direction. This is the point that zinc on the surface of the steel plate 3 or the second galvanized steel plate 4 is volatilized.

  FIG. 2 is a diagram showing the current and magnetic field direction of plasma welding by the first welding torch 1 and pulse GMA welding by the second welding torch 2 in the second embodiment. The direction of the first current 5 in plasma welding is a direction from the base material (galvanized steel sheet) toward the welding torch. On the other hand, the direction of the second current 6 in the pulse GMA welding is a direction from the welding torch toward the base material. The direction of the magnetic field can be determined from the directions of the first current 5 and the second current 6. In FIG. 2, the direction of the magnetic field due to the first current 5 of plasma welding is indicated by the first magnetic field 7. The direction of the magnetic field due to the second current 6 of the pulse GMA welding is indicated by the second magnetic field 8. It can be seen that the direction of the first magnetic field 7 and the direction of the second magnetic field 8 are in the same direction and are repelling each other.

  FIG. 3 is a diagram showing the influence of the second arc 10 by pulse GMA welding on the first arc 9 by plasma welding. Pulse GMA welding is a welding method in which the peak current with the highest current and the base current with the lowest current are alternately switched. The positional relationship between the first welding torch 1 for plasma welding and the second welding torch 2 for pulse GMA welding is parallel to the welding direction.

  FIG. 3A shows a state when the peak current is output and the current is high. In FIG. 3A, since the second magnetic field 8 shown in FIG. 2 is in a strong state, the influence on the first magnetic field 7 is large, and the first arc 9 has the second repulsive property due to the repulsive nature. The direction is away from the arc 10.

  On the other hand, FIG. 3B shows a state when the base current is output and the current is low. In FIG. 3B, since the second magnetic field 8 shown in FIG. 2 is in a weak state, the influence on the first magnetic field 7 is small, and the first arc 9 hardly affects the second arc 10. It does not receive, and it remains facing almost vertically.

  Under the influence of pulse GMA welding in which peak current and base current are alternately switched, the first arc 9 by plasma welding swings back and forth with respect to the welding direction, and the surface of the galvanized steel sheet is more extensive than when it does not swing. Of zinc can be volatilized.

  Further, the positional relationship between the first welding torch 1 for plasma welding and the second welding torch 2 for pulse GMA welding may be slightly shifted from parallel to the welding direction. By doing in this way, the 1st arc 9 by the plasma welding which was rocking | fluctuating back and forth when it was parallel will rock | fluctuate in the back-and-forth direction diagonally with respect to the welding direction. Thereby, the zinc of the surface of a galvanized steel plate can be volatilized more widely, and it can make it easier to volatilize zinc compared with the case where it rocks in the front-back direction.

  As described above, according to the second embodiment, zinc on the surface of the galvanized steel sheet is volatilized widely by swinging the first arc 9 of the preceding plasma welding in the front-rear direction or the oblique front-rear direction. be able to.

(Embodiment 3)
In the third embodiment, the same components as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The main difference from the first embodiment and the second embodiment is that in the lap welding of the galvanized steel sheet (hereinafter referred to as lap welding), the upper plate (first zinc) is formed by plasma welding of the first welding torch 1. The plated steel plate 3) is melted, and the surface treatment of the overlapping portion of the first galvanized steel plate 3 and the second galvanized steel plate 4 is removed.

  FIG. 4 is a schematic diagram for easily showing the overlapping portion when the first galvanized steel plate 3 and the second galvanized steel plate 4 which are two galvanized steel plates are overlapped. In FIG. 4, the color-coded part shows the part surface-treated with zinc to be removed in the third embodiment.

  FIG. 5 is a view showing the direction of zinc volatilization when the upper plate of the overlapped portion of two galvanized steel plates is plasma-welded. In FIG. 5, the hatched portion indicates a portion where the first galvanized steel plate 3 as the upper plate is melted by plasma welding using the preceding first welding torch 1. Moreover, in FIG. 5, six arrows have shown the direction in which the zinc of the part which the galvanized steel plate overlapped by volatilizing an upper plate volatilizes.

  In the lap welding of galvanized steel sheets, the color-coded portions of zinc in FIG. 4 were the cause of a large amount of spatter and pores. The upper plate is melted by plasma welding of the preceding first welding torch 1, and heat is applied to the overlapping portions of the galvanized steel plates. Thereby, volatilization of the zinc of the overlapping part of a galvanized steel plate is promoted. By doing in this way, in the pulse GMA welding by the 2nd welding torch 2 performed following the plasma welding by the 1st welding torch 1 which precedes, it can weld in the state where there is little zinc on the steel plate surface, Welding can be performed in a state close to the case of welding an untreated steel plate.

  As described above, according to the third embodiment, in the lap welding of galvanized steel sheets, only the upper plate is melted by plasma welding of the preceding first welding torch 1, and the surface of the overlapped portion of the galvanized steel sheets In the pulse GMA welding following the plasma welding after removing the treatment, it is possible to perform the welding with a small amount of zinc on the steel sheet surface.

  In addition, when both the upper plate and the lower plate are melted by plasma welding, that is, when plasma welding is performed including the overlapping portion of the galvanized steel plate, the plasma welding itself takes place from the overlapping portion of the galvanized steel plate. It will inhibit the volatilization to some extent. However, as in the third embodiment, since only the upper plate is melted by plasma welding, plasma welding is not performed on the overlapped portion of the galvanized steel plates. It does not inhibit zinc from evaporating from the mating part. Therefore, compared with the case where both the upper plate and the lower plate are melted by plasma welding, the generation of spatter and pores can be further reduced.

  As described above, according to the present invention, the first step of performing plasma welding to remove the surface treatment of the member and the second step of performing pulse GMA welding following the first step are provided, Since low spatter and low porosity can be realized in the welding of steel plates, it is industrially useful as a welding method for welding members subjected to surface treatment.

DESCRIPTION OF SYMBOLS 1 1st welding torch 2 2nd welding torch 3 1st galvanized steel plate 4 2nd galvanized steel plate 5 1st electric current 6 2nd electric current 7 1st magnetic field 8 2nd magnetic field 9 1st Arc 10 Second arc

Claims (4)

It is a welding method for welding the surface-treated member,
A first step of performing plasma welding to remove the surface treatment of the member;
A welding method comprising a second step of performing GMA welding subsequent to the first step,
A welding method for removing surface treatment of the member by swinging an arc generated by the plasma welding in the first step. The welding method according to claim 1, wherein the second step GMA welding is pulse GMA welding, and the arc generated by the plasma welding in the first step is swung by performing the pulse GMA welding. A welding method for welding an overlapped portion of two members subjected to surface treatment, wherein only the upper plate is melted by plasma welding in a first step, whereby the above-mentioned 2 is generated by heat that melts the upper plate. The welding method according to claim 1 or 2, wherein the surface treatment of the overlapped portion of the sheet members is removed. The welding method according to any one of claims 1 to 3, wherein the surface-treated member is a galvanized steel sheet.

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