JPH04279291A - Laser beam welding method - Google Patents

Abstract

PURPOSE:To accurately hold a gap between galvanized steel sheets and to perform stable laser beam welding. CONSTITUTION:A sheet of paper 2 is held between the galvanized steel sheets 1a and 1b and the gap is maintained accurately. Even if zinc of the galvanized steel sheets 1a and 1b evaporates by a laser beam 8, it can enter the sheet of paper 2. In addition, the sheet of paper 2 also instantaneously evaporates and burns, the upper and lower steel sheets are joined together by molten iron and laser beam welding can be performed. Since the gap can be maintained accurately by the sheet of paper 2, stable welding with few blowholes can be performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device and a laser welding method for welding surface-treated metals, and more particularly to a laser welding method for welding zinc steel plates with a laser beam.

0002

[Prior Art] With the increase in the output of laser oscillators, the field of application of laser welding, which uses laser beams instead of conventional gas welding or electric welding, is expanding. Demand is high in the center. The steel sheets used in the automobile industry are galvanized steel sheets from the viewpoint of rust prevention. Stable and high-speed laser welding of these galvanized steel plates and the like is required.

However, in lap welding of galvanized steel sheets, the surface plating layer of the steel sheets evaporates when irradiated with a laser beam, causing a large number of blowholes. In particular, if there were no gaps between the steel plates, the evaporated zinc vapor would blow away the molten base material, making welding impossible. This is thought to be because the boiling point of zinc is lower than the melting point of iron, and the evaporation pressure is high, which blows away the molten iron.

For this reason, when welding galvanized steel plates one on top of the other, a gap of several hundred microns is left between the steel plates.
This allows zinc vapor generated from the surface to escape. FIG. 3 is a diagram showing an example in which a gap is provided between galvanized steel plates. When laser welding the galvanized steel plate 21 and the galvanized steel plate 22,
A jig 23 is inserted in between to provide a gap. In this state, laser welding is performed to form a bead 24.

FIG. 4 is a diagram showing another example of providing a gap between galvanized steel sheets. FIG. 4(a) is a plan view, and FIG. 4(b) is a diagram taken along line A-A in FIG. 4(a). FIG. Here, the galvanized steel plates 31 and 32 are laser welded. To create a gap,
Dowel presses 33, 34, 35, and 36 are provided on a galvanized steel plate 31. Welding is performed in this state to form a bead 37.

[0006]

[Problem to be solved by the invention] However, in the example shown in Fig. 3, it is troublesome to adjust the jig in order to maintain the gap accurately, and if the gap is small, the effect of the gap disappears, and if it is large, welding becomes impossible. . Further, in the example of FIG. 4, it is necessary to perform dowel pressing, and a pressing process is required before laser welding. The present invention has been made in view of these points, and it is an object of the present invention to provide a laser welding method that can easily secure a gap between surface-treated metals such as galvanized steel plates and perform stable welding.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a laser beam for welding a surface-treated metal coated with an object whose evaporation temperature is lower than the melting point of the metal using a continuous wave or pulsed waveform laser beam. In the welding method, there is provided a laser welding method characterized in that welding is performed by sandwiching paper or cloth between the surface-treated metals.

[0008]

[Operation] By sandwiching paper or cloth between surface-treated metals, the gap can be accurately secured. During laser welding, the zinc steel plate is melted by the laser beam and penetrated by the laser beam. At this time, the zinc plated on the surface of the galvanized steel sheet quickly escapes into the gaps in the paper or cloth. Also,
Paper and cloth instantly evaporate and burn, and the upper and lower steel plates are connected by molten iron. When the laser beam passes through, this area quickly solidifies and can be laser welded.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of a laser device for implementing the present invention. A paper 2 is sandwiched between the galvanized steel plates 1a and 1b. The thickness of the paper 2 is preferably 50 μm to 300 μm. The thickness of the paper 2 ensures an accurate gap between the galvanized steel plates 1a and 1b. The galvanized steel plates 1a, 1b are clamped to a table 7 by clamps 3a, 3b. On the other hand, the laser beam 8 is focused by the processing head 4 and irradiated onto the processing point 5 . As a result, beads 6 are formed. When the laser beam 8 is irradiated onto the zinc steel plates 1a and 1b, the zinc steel plates 1a and 1b melt and the laser beam 8
penetrates. At this time, the zinc plated on the surfaces of the galvanized steel plates 1a and 1b rapidly escapes into the paper 2. Additionally, the paper 2 instantly evaporates and burns, and the upper and lower steel plates are connected by molten iron. When the laser beam 8 passes, the processing point 5 is solidified and laser welding can be performed.

FIG. 2 is a diagram showing an embodiment of another laser welding method. A part 11a of the galvanized steel plate 11 is bent and paper 13 is placed on both sides of it. On the other hand, another galvanized steel plate 12 is pressed so as to cover it, and laser welding is performed to form a bead 14.
is formed. At this time, the paper 13 is carbonized during welding,
The carbides 15, 16, 17, and 18 remain. In the above explanation, paper was used to secure the gap between the galvanized steel plates, but cloth such as cotton may also be used instead of paper. Further, although the explanation has been given using a galvanized steel plate as an example, the present invention can be similarly applied to other surface-treated metals. Note that a pulsed or continuous wave laser beam can be used.

[0011]

[Effects of the Invention] As explained above, in the present invention, since laser welding is performed by sandwiching paper or cloth between the surface-treated metals, the gap between the surface-treated metals can be accurately secured, and stable laser welding can be performed. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an external view of a laser device for implementing the present invention.

FIG. 2 is a diagram showing an example of another laser welding method.

FIG. 3 is a diagram showing an example in which a gap is provided between galvanized steel plates.

FIG. 4 is a diagram showing another example in which a gap is provided between galvanized steel plates.

[Explanation of symbols]

1a, 1b Galvanized steel plate 2 Paper 3a, 3b Clamp 4 Processing head 5 Processing point 6 Bead 7 Table 8 Laser beam

Claims (3)

[Claims] 1. A laser welding method in which a surface-treated metal coated with an object whose evaporation temperature is lower than the melting point of the metal is welded by a laser beam having a continuous wave or pulsed waveform, in which paper or cloth is placed between the surface-treated metals. A laser welding method characterized by sandwiching and welding. 2. The laser welding method according to claim 1, wherein the surface-treated metal is a zinc steel plate. 3. Bend the ends of the surface-treated metal, adhere the paper or cloth to both sides of the ends, cover the paper or cloth with another surface-treated metal, and weld the ends. The laser welding method according to claim 1.