An electrode for suppressing cracks in aluminum alloy resistance spot welding

Abstract

The invention relates to an electrode for restraining the generation of an aluminum alloy resistance spot welding crack. The electrode is of a vertically-symmetrical structure, and the end surface of the electrode, which is in contact with the surface of an aluminum alloy plate to be processed, is a straight end surface, and an outer ring groove and a central circular groove are formed in the straight end surface. Compared with the prior art, the electrode has the advantages that the tensile stress in a joint heat affected zone can be weakened to achieve the effect of reducing the generation of the crack; through the design of a dent in the edge of the electrode, corresponding pressure stress is applied to counteract the tensile stress, so that the effect of completely restraining the crack is achieved, and further, the stability of the welding quality is ensured.

Description

technical field [0001] The invention belongs to the technical field of spot welding, and in particular relates to an electrode used for suppressing the generation of cracks in aluminum alloy resistance spot welding. Background technique [0002] Aluminum alloy resistance spot welding is the most important welding process method in the automatic production of automobile body, but there is a main problem in aluminum alloy resistance spot welding: due to the large thermal expansion coefficient of aluminum alloy, the plate is more serious and deformed after spot welding Larger, the heat-affected zone is prone to joint cracks, and the indentation is too deep. The cracks mentioned in the present invention refer to the cracks distributed in the heat-affected zone of the joint. It is judged here that it is a kind of liquefaction crack, which starts in the heat-affected zone near the fusion line and expands towards the base metal. The crack formation process is a result of the inter...

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Problems solved by technology

[0002] Aluminum alloy resistance spot welding is the most important welding process method in the automatic production of automobile body, but there is a main problem in aluminum alloy resistance spot welding: due to the large thermal expansion coefficient of aluminum alloy, the plate is more serious and deformed after spot welding Larger, the heat-affected zone is prone to joint cracks, and the indentation is too deep

This is because the welding of aluminum alloys with flat end electrodes that are usually used for welding steel plates tends to cause large deformations on the surface, so that there are more regular liquefaction cracks in the heat-affected zone, and the deformation of the plates is large, and the indentation depth Deep, unstable welding quality

Foreign scholars also try to restrain the cracks in the heat-affected zone of aluminum alloy spot welding joints by using externally added fixtures to restrain the corresponding area, but this method is relatively complicated and not suitable for mass production

At the same time, by adjusting the process, such as by using the flat end electrode multi-pulse process resistance spot welding aluminum alloy plate, it is found that after welding, the warpage deformation of the plate is weakened, and the number of cracks is reduced, but the cracks still cannot be completely eliminated.

[0003] The Chinese patent with the application number 201210405715.6 discloses a method for eliminating reheating cracks of spot welded joints. The plate spot welded joints with a thickness of 0.5-3 mm are subjected to spherical pressure to eliminate residual stress before heat treatment; pressure is applied to the solder joints and surrounding areas For the mold used, the surface in contact with the spot welding joint is a spherical or approximately spherical surface, the radius of curvature is greater than or equal to the radius of the spherical electrode used in spot welding, and the area of ​​the pressurized area is greater than the area of ​​the welding spot and completely covers the welding spot; butt welding The stress applied to the point and the surrounding area exceeds the yield strength of the nugget and the base metal, causing it to undergo plastic deformation; when the spot welding joint is spherically pressurized, the center of the welding point is coaxial with the center of the mold, but the re- Thermal cracks are internal cracks in the nugget, and liquefaction cracks will also appear in the heat-affected zone outside the fusion line when using this patent for spot welding of aluminum alloys. Due to the large thermal expansion coefficient of aluminum alloys, the thermal stress received during the cooling process Therefore, corresponding cracks will still be generated. Based on the above theoretical analysis of cracks, combined with experimental verification, it is found that the liquefaction cracks in the heat-affected zone of aluminum alloy spot welding joints have not been eliminated.

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