JP2001276989A - Laser lap welding method for plating steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply release evaporating gas of constituent elements produced from plating layers to the outside when welding plating steel plates by a laser lap welding. SOLUTION: A slit 4b is intermittently formed on a welding line Lw of an upper plating steel plate by a laser beam as a preliminary process, when laser-welding through the welding line Lw of overlapped plating steel plates 4 and 5. Then, a portion, in which the slit 4b is not formed on the welding line Lw, is laser-welded while both sides of a laser irradiating portion is pushed by a pressure roll. Evaporation gas of constituent elements produced from the plating layers between connecting surfaces 4a and 5a is released outside via the slit 4b. Subsequently, the slit 4b is laser-welded to block by means of a melting metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lap laser welding method for a plated steel sheet used for an automobile body or the like.

[0002]

2. Description of the Related Art Conventionally, galvanized steel sheets have been used as surface-treated steel sheets for automobiles. However, since galvanized steel sheets have a relatively high corrosion rate of zinc, it is necessary to use a thick steel sheet in order to expect a long-term rust prevention effect. Light weight plating is required.

[0003] Therefore, in order to suppress the activity of the galvanized layer, the steel sheet is hot-dip galvanized, then subjected to alloying treatment, and subjected to Fe-Zn interdiffusion to form an alloyed molten layer. Galvanized steel sheets have been commercialized and widely used.

An alloyed hot-dip galvanized steel sheet can easily increase the amount of adhesion compared with an electroplated steel sheet economically, and is a steel sheet which can easily be improved in corrosion resistance by thickening.

[0005] However, when laser heavy welding is performed in a state in which zinc-based galvanized steel sheets including such alloyed hot-dip galvanized steel sheets are stacked, a large amount of zinc vapor is generated from a plating layer between joining surfaces, and this vapor is generated. A large number of defects (defects called pits) in the bead, such as blowholes or bead surface dents, occur due to the gas being confined in the molten metal, and the bead roughness worsens. It has been known.

[0006] For this reason, various techniques of performing lap laser welding in a state where a gas exhaust passage is formed between the joining surfaces of the plated steel sheets have been attempted. For example, Japanese Patent Application Laid-Open No. H11-226765 discloses a technique for performing the welding. There is disclosed a technique in which unevenness is formed by blasting, a gas exhaust path is formed by the unevenness, and component evaporation gas generated during lap laser welding is released to the outside through the gas outlet path.

[0007]

However, it is necessary to strictly control the height of the gap between the joining surfaces of the gas discharge path during lap laser welding.

That is, if the height of the gap between the joining surfaces is too narrow, the gas cannot be completely released before the welded portion solidifies, and the above-described poor welding occurs.
If the height of the gap is too wide, the molten metal flows into the gas discharge path, causing inconvenience such that the coated steel sheet irradiated with the laser beam is melted.

Therefore, in the case of lap laser welding, the height of the gap between the joining surfaces must be strictly controlled using a dedicated jig or the like, which increases the number of working steps and lowers production efficiency. There are inconveniences.

The present invention has been made in view of the above circumstances, and has no problem in that a gas exhaust passage generated between a plating layer between bonding surfaces is released to the outside with a simple structure without providing a gas discharge path between bonding surfaces. It is an object of the present invention to provide a lap laser welding method for a plated steel sheet that can be performed.

[0011]

In order to achieve the above object, a first lap laser welding method for a plated steel sheet according to the present invention is directed to a lap laser welding method for a plated steel sheet in which mutually opposed plated steel sheets are laser-welded. After the slit is intermittently formed on the welding line of the plated steel sheet on the side irradiated with the laser beam by using the laser beam, a portion of the welding line where the slit is not formed is laser-welded.

In such a configuration, after the two plated steel sheets are overlapped, a slit is formed intermittently using laser light on the welding line of the plated steel sheet to be irradiated with the laser light, and thereafter, Then, a portion of the welding line where no slit is formed is laser-welded. At that time, the component evaporative gas generated from the plating layer on the joint surface is discharged to the outside through the slit.

The second method of lap laser welding of plated steel sheets is a method of lap laser welding of plated steel sheets in which mutually opposed plated steel sheets are laser-welded. And forming a slit intermittently using the method and removing the plating layer of the lower plated steel sheet exposed from the slit, and then laser welding a portion of the welding line where the slit is not formed. .

In such a configuration, after the two plated steel sheets are overlapped, the slit is formed intermittently by using the laser light on the welding line of the plated steel sheet to be irradiated with the laser light. Then, the plating layer of the lower plated steel sheet exposed from the slit is removed by using the heat of the laser beam, and then the portion of the welding line where the slit is not formed is laser-welded. At that time, the component evaporative gas generated from the plating layer on the joint surface is discharged to the outside through the slit.

A third method of lap laser welding of a plated steel sheet is the method of the first or second method of lap laser welding of a plated steel sheet, wherein a laser beam is welded to a portion of the welding line where the slit is not formed, and then the slit is formed. Laser welding is performed while the molten metal is supplemented.

In such a configuration, after a portion of the welding line where the above-mentioned slit is not formed is laser-welded, laser welding is performed while filling the slit with molten metal, and this slit is closed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is an enlarged view of a welding head portion of a lap laser welding apparatus, FIG. 2 is an enlarged sectional view of a joining surface of a plated steel sheet, FIG. 3 is a perspective view of a joining surface of a plated steel sheet, and FIG. 5 is an enlarged cross-sectional view of the portion shown in FIG.
It is sectional drawing of the different state of the same site | part.

Reference numeral 1 in the drawing denotes a welding head, and a roller arm 2 is fixed to the welding head 1, and pressure rollers 3 are pivotally supported on both sides of the welding arm 1 of the roller arm 2.

The welding head 1 is connected to a robot arm (not shown) or the like. By the operation of the robot arm, the welding line Lw of the two superposed plated steel plates 4 and 5 is formed.
(See FIG. 3) The upper side is moved while being pressed against both sides by a pair of pressure rollers 3, and at this time, two plated steel sheets 4, 4 are emitted by a laser beam emitted from the welding head 1.
5 is continuous line welded. Reference numeral 21 denotes plated steel sheets 4 and 5
Is shown only between the joint surfaces 4a and 5a in the figure, but is actually formed on the entire periphery of the plated steel plates 4 and 5.

As shown in FIG. 3, a slit 4b is formed intermittently on the welding line Lw of the upper plated steel sheet 4. The slit 4b is post-processed by laser light irradiation, and laser-welds a portion on the welding line Lw where no gap is formed between the slits 4b. Reference numeral 22 denotes a bead formed by laser welding.

After the completion of the lap laser welding, the slit 4b is filled with the molten metal 24 and closed.

In such a configuration, the joining surfaces 4a and 5a of the two plated steel plates 4 and 5 are overlapped, and a laser beam from the welding head 1 is irradiated on the welding line Lw of the upper plated steel plate 4. As a pre-process for laser welding, first, a slit 4 is formed in the upper plated steel sheet 4 using this laser beam.
b is formed intermittently. At the same time, using the heat at this time, the plating layer in the portion of the lower plated steel sheet 5 exposed to the slit 4b is evaporated.

Next, laser welding is performed on the welding line Lw.
First, both the plated steel plates 4 and 5 are pressed by the pressure roller 3, and while the welding head 1 is moved along the welding line Lw, a portion where the slit 4a is not formed is irradiated with laser light to perform lap laser welding.

At this time, since the pressure roller 3 presses both sides of the laser irradiation part, both the plated steel plates 4 and 5 are pressed.
The laser welding is performed in a state where the joining surfaces 4a and 5a are in close contact with each other, so that stable welding can be performed without being affected by the surface shape.

In the case of laser welding, the joining surfaces 4a, 5a
The component evaporation gas generated from the intermediate plating layer 21 is discharged outside through the slit 4b. Therefore, no component evaporation gas remains in the bead 22 formed by laser welding, and it is possible to avoid occurrence of welding defects such as blow holes and bits, and to obtain stable welding quality.

After the laser welding has been completed,
The slit 4b is laser-welded while supplementing the molten metal using the filler wire 23, and the slit 4b is closed. At this time, the plating layer formed on the surface of the lower plated steel sheet 5 exposed to the slit 4b
No welding failure occurs because it has been removed when forming.

As described above, according to the present embodiment, the slits 4b are formed intermittently in advance on the welding line Lw, and are generated from the plating layer 21 between the joining surfaces 4a and 5a during laser welding. Since the component evaporating gas is emitted to the outside through the slit 4b, there is no need to provide a gas discharge path between the joining surfaces 4a and 5a, and laser welding is performed in a state where both joining surfaces are in close contact with each other. As a result, laser welding can be performed without being affected by the surface shapes of the plated steel plates 4 and 5, and stable welding quality can be obtained and productivity is improved. be able to.

[0028]

As described above, according to the present invention,
Since the slit is formed intermittently on the welding line of the plated steel plate on the side where the laser beam is irradiated, the component evaporative gas from the plating layer between the joint surfaces generated during laser welding is released outside through the slit Therefore, there is no need to provide a gas exhaust path between the joining surfaces, and the components can be simplified,
In addition, laser welding can be performed without being affected by the surface shape of the plated steel sheet, stable welding quality can be obtained, and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a welding head portion of a lap laser welding apparatus.

FIG. 2 is an enlarged sectional view of a joint surface of a plated steel sheet.

FIG. 3 is a perspective view of a joint surface of a plated steel sheet.

FIG. 4 is an enlarged cross-sectional view of another portion of the joining surface of the plated steel sheet.

FIG. 5 is a sectional view of the same part as in FIG. 2 in a different state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding head 2 Roller arm 3 Pressure roller 4, 5 Plating steel plate 4a, 5a Joining surface 4b Slit 21 Plating layer 22 Bead 23 Filler wire 24 Molten metal Lw Welding wire

Claims (3)

[Claims] In a lap laser welding method for a plated steel sheet in which a plated steel sheet facing each other is laser-welded, a slit is formed intermittently on a welding line of the plated steel sheet to be irradiated with the laser light using the laser light. Then, a laser welding method is performed on a portion of the welding line where the slit is not formed, by laser welding. 2. A lap laser welding method for a plated steel sheet in which mutually opposed plated steel sheets are laser-welded, wherein a slit is intermittently formed on a welding line of the plated steel sheet to be irradiated with the laser light using the laser light. Lap laser welding of a plated steel sheet, wherein a portion of the welding line where the slit is not formed is laser-welded after removing a plating layer of a lower plated steel sheet exposed from the slit. 3. The plated steel sheet according to claim 1, wherein after laser welding a portion of the welding line where the slit is not formed, laser welding is performed while filling the slit with molten metal. Laser welding method.