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Application Of Sheet Metal Design In Laser-Welded Box Structures

Laser welding has the advantages of fast speed, small deformation, beautiful weld seam and high strength. It is widely used in aviation, automobile, medical and other fields.

Among them, the laser self-fusion welding is a non-wireless non-contact welding process, the welding seam has various forms, and has excellent welding seam consistency.

In the field of sheet metal manufacturing, it has huge application potential.

This paper focuses on the application of sheet metal design in laser welding of housing structures with flanged 45° beveled joints.

Sheet metal design in the structure of laser welding box

The material of the box body is 304 stainless steel with a thickness of 1.5mm, and the size of 200mm × 200mm × 115mm. The bending angle of the box is 90 °, 90 ° and 80 ° from bottom to top.

The schematic diagram of the box structure is shown in Figure 1.

Table 1 shows the laser welding parameters.

Schematic diagram of the box structure

Figure 1 Schematic diagram of the box structure

Welding process Laser thermal conduction welding
Power (W) 3000
Speed ​​(m / min) 1.8
Defocus (mm) 10

Table 1 Laser welding parameters

In the traditional welding stainless steel box structure process, in order to obtain a more beautiful welding product, it is usually necessary to carry out grinding and polishing treatment after welding.

Subsequent procedures are cumbersome and take a long time, the welding deformation and welding penetration are extremely likely to occur during the welding process.

Laser welding has huge application potential in the field of sheet metal welding due to its advantages such as fast welding speed, small deformation and beautiful welding seam.

How to apply the advantages of fast laser welding, narrow welding heat affected zone, small deformation and high precision in the welding of box structure has become an urgent problem to be solved.

Design of overlap of laser welding box structure

In the welded stainless steel box structure, the box fillet weld occupies the vast majority of the entire welding process.

In order to obtain a round laser welding seam, we have optimized the amount of overlap in traditional welding.

As shown in Figure 2, Figure 3. Where t is the thickness of the plate, a is the amount of overlap, b is the position of the laser center on the cross section of the plate, and α is the laser tilt angle.

Improvement of fillet welding seam overlap

Figure 2 Improvement of fillet welding seam overlap

Laser welding overlap

Figure 3 Laser welding overlap

The optimized amount of overlap is welded by laser thermal conduction welding.

The defocusing distance is accurately set to 10.00mm and the focusing accuracy to 0.01mm by the automatic focusing system.

By accurately positioning the b value with a high-magnification CCD camera, a rounded laser weld can be achieved without filler wire, as shown in Figure 4b.

The optimization method of the amount of overlap is suitable for plates with a thickness of 3 mm and below, where the a, b, and α values are determined by the t value.

Schematic diagram of the optimization of the amount of overlap and the actual laser welding effect

Figure 4 Schematic diagram of the optimization of the amount of overlap and the actual laser welding effect

Design of the corner release groove of the laser welding box structure

In the welded stainless steel box structure, the optimization of the corner relief groove is also extremely important, which directly affects the effect of the bottom structure of the box.

In the traditional welding process, rectangular or rounded corner relief grooves are generally used.

However, this type of corner relief groove is very easy to cause weld through or not full when laser welding.

The schematic diagram of the corner release slot is shown in Figure 5.

Schematic diagram of corner release slot

Figure 5 Schematic diagram of corner release slot

By calling laser welding corner release groove process block, the product structure is optimized.

After laser welding, a very full and round welding effect can be obtained, almost no secondary treatment is required, and the subsequent processing time is greatly reduced. As shown in Figure 6, Figure 7.

Schematic diagram of laser welding design of corner release groove

Fig. 6 Schematic diagram of laser welding design of corner release groove

Actual laser welding effect of the corner release slot

Figure 7 Actual laser welding effect of the corner release slot

Design of 45 ° bevel interface for laser welding box structure flanging

In the welded stainless steel box structure, due to the amount of bending deformation, it is difficult to close tightly at the position of the 45 ° bevel interface of the flange.

As shown at A in Figure 8. It is extremely difficult to handle by laser welding.

Therefore, the design of the interface will directly affect the welding quality of the box structure.

At the same time, there will be a large gap at B, direct laser welding is difficult to deal with.

Schematic diagram before optimization

Figure 8 Schematic diagram before optimization

For this situation, we have optimized the cabinet structure. During the design, part of the metal of the step surface is cut off, and then two small step surfaces are extended. As shown in Figure 9a.

Then, when unfolding, use the end surface as a reference to make up the previously cut part. As shown in Figure 9b, Figure 9c.

At B in Figure 8, two stepped surfaces are alternately extended to increase the amount of metal compensation to make up for the gap created there, as shown in Figure 9d.

Schematic diagram of the sheet metal design of the 45 ° beveled flange interface

Figure 9 Schematic diagram of the sheet metal design of the 45 ° beveled flange interface

Figure 10 shows the effect after actual laser welding.

It can be seen from Figure 10a that the interface is tightly closed, which fully meets the laser welding process requirements.

The surface of the welding seam is beautiful, the transition is natural, and there is no phenomenon of sink, welding and so on. In Figure 8, B is also filled well.

Laser welding effect of flange 45 ° bevel interface

Figure 10 Laser welding effect of flange 45 ° bevel interface

Conclusions

With the continuous development of the welding process, the traditional sheet metal design scheme will gradually be stretched.

Similarly, in the promotion of laser welding in the sheet metal industry, the introduction of new laser welding sheet metal design solutions will also be imperative.

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