Spot welding process method for high carbon equivalent cold-rolling dual phase steel

Abstract

The invention relates to a spot welding process method for high carbon equivalent cold-rolling dual phase steel. The cold-rolling dual phase steel has carbon equivalent Ceq greater than or equal to 0.5; the spot welding process comprises three stages, namely a preheating stage, a welding stage and a slow cooling stage, and at least comprises the welding stage; at the preheating stage, structure rigidity of a steel plate is eliminated to obtain uniform contact resistance; at the welding stage, a molten core is formed, and textures and stress of the molten core of the steel plate are improved byusing a multi-pulse process; at the slow cooling stage, the cooling speed of a molten core metal is reduced after the molten core is formed at a welding spot, and then various properties of the welding spot are improved. By adopting the spot welding process, texture constitution and stress states of a molten core part can be improved, the problem that cracks can be easily caused at a molten coreline part when spot welding is carried out on the cold-rolling dual phase steel of which the carbon equivalent Ceq is not smaller than 0.5, is solved, and the spot welding quality can be improved.

Description

technical field [0001] The invention relates to the field of welding technology, in particular to a spot welding process for high-carbon equivalent cold-rolled dual-phase steel. Background technique [0002] As the strength requirements of cold-rolled dual-phase steel (also known as DP steel) become higher and higher, the content of alloy components in the steel is also higher and higher, and the carbon equivalent level increases accordingly, resulting in a significant increase in the hardening tendency of the steel plate. Especially for cold-rolled dual-phase steel with carbon equivalent Ceq≥0.5, after welding by conventional spot welding process, cracks are prone to appear at the nugget line of the solder joint and expand to the core of the melt, seriously affecting the strength and performance of the solder joint. Restricted the popularization and application of this steel plate. [0003] At present, the processes commonly used for spot welding high-strength steel plates...

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Problems solved by technology

[0007] The invention provides a high carbon equivalent cold-rolled dual-phase steel spot welding process, which can improve the structure composition and stress state of the nugget part, and effectively solve the nugget during spot welding of cold-rolled dual-phase steel with carbon equivalent Ceq≥0.5 The problem of cracks easily appearing in the wire part improves the quality of spot welding

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