JPH11226765A - Laser welding structure of galvanized steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding structure that exhausts the evaporation gas of a plating material, a gas generating at the time of laser welding of a galvanized steel sheet. SOLUTION: The galvanized steel sheet 30, which is used for a panel member of an car body structure for example, is plated with a coat material such as zinc on the steel sheet. As a pre-processing for laser welding with two of these galvanized steel sheets superimposed, blasting is performed against the joining faces 32. The rugged face 40 remains on the galvanized steel sheet, forming an exhaust passage for the evaporation gas generating at the time of laser welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A plated steel sheet obtained by plating a surface of a steel sheet with a coated plate is widely used as a panel member of an automobile body structure. In many cases, a panel member constituting a vehicle body is formed into a predetermined shape by superposing a plurality of panel elements that have been pressed in advance and welding and joining them by a laser welding machine or the like. When two sheets of plated steel sheet are overlapped and subjected to laser welding, the coating material plated on the surface of the steel sheet evaporates to generate gas. This gas becomes bubbles and remains in the weld bead, causing a decrease in welding strength. Therefore, means for discharging the gas from the laser weld is required.

For example, Japanese Patent Application Laid-Open No. 4-327385 discloses a technique in which a gas vent groove is formed in advance along with welding of a steel plate.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser welding structure of a plated steel sheet for discharging gas generated at a laser welding portion by simpler means.

[0005]

The laser welding structure of a plated steel sheet according to the present invention is obtained by subjecting a welding joint surface of two superposed plated steel sheets to a blasting treatment as a pretreatment for laser welding. .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing how a laser welding process is performed on a panel matching structure according to the present invention. The laser processing head 1 has a tapered conical nozzle portion 12 at the tip of a cylindrical lens holder 10. Inside of the lens holder 10, condenser lens 14 is provided to focus the laser beam LB is a collimated light transmitted from the laser beam generator (not shown), it focuses on welding portions W ₁ .

A protective glass 16 is provided on the nozzle portion 12 side of the condenser lens 14 to prevent spatter and the like generated at the welded portion W _{1 from} adhering to the condenser lens 14. An assist gas is appropriately supplied into the nozzle 12 to assist the welding process and to cool the nozzle 12. The welding portion W _1, two plated steel 20, 30 are arranged superimposed, two plated steel 20, 30 are formed bead B along the weld line is welded.

FIG. 2 is an explanatory view of a plated steel sheet which has been subjected to welding pretreatment according to the present invention. The plated steel plate 30 is a plate in which a coating material such as zinc is plated on the surface of the steel plate, and the welding joint surface 32 is subjected to blast processing in advance. Blasting is a process in which particles of blasting material such as sand and silica stone are sprayed onto the welded joint surface of the plated steel sheet by high-pressure water or compressed air, and the surface of the blasted welded joint surface 32 is A large number of minute uneven surfaces 40 are formed.

[0009] When laser welding is performed by superimposing the plated steel sheets which have been subjected to the welding pretreatment, gas and the like generated at the joint surface are discharged from the minute gap generated by the uneven surface 40 formed by spraying the blast particles. Discharged to
The bubbles are prevented from remaining in the bead portion B.
Therefore, a bead portion B having a predetermined strength is formed, and the strength of the welded portion is ensured.

FIG. 3 is an explanatory view showing another embodiment of the present invention. A scissoring process is performed on the welding joint surface 32 of the plated steel plate 30 as a pre-welding process.
Many fine grooves 50 are formed on the welded joint surface 32 by the scissors processing. At the time of the welding process, the evaporated gas is discharged from the groove, so that it is possible to prevent bubbles from remaining in the bead portion B. Therefore, the strength of the weld is ensured.

[0011]

As described above, according to the present invention, when the plated steel sheets are overlapped with each other and subjected to laser welding, the treatment for releasing the vaporized gas such as a plating coat material generated at the time of welding is performed on the welded joint surface. In addition, harmful gas bubbles and the like do not remain in the bead of the welded portion, and the welding strength can be secured.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a laser welding process according to the present invention.

FIG. 2 is an explanatory diagram of a pretreatment for laser welding of a plated steel sheet according to the present invention.

FIG. 3 is another explanatory view of a pretreatment for laser welding of a plated steel sheet according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser processing head 10 Lens holder 12 Nozzle 14 Condensing lens 16 Protective glass 20, 30 Plated steel plate 40 Uneven surface 50 Scissors processing groove

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[Procedure amendment]

[Submission date] February 25, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

Claims (1)

[Claims] 1. A laser welded structure of a plated steel sheet obtained by subjecting a welded joint surface of two superposed plated steel sheets to blast processing as pretreatment for laser welding.