Abstract
In this paper,the spot welding technology of a new kind of 22 MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder.Through a series of technology and test experiments,we have obtained the optimal spot welding technological parameter condition.According to the results,the relations among spot welding technological parameter,welding nugget,mechanical property and fracture mode were discussed.The effects of all the welding parameters such as welding current,welding time and electrode force on the quality of joint can be boiled down to one thing—the diameter of welding nugget.The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation.There are two typical fracture models of 22 MnMoB hot stamping quenched steel sheet,i.e.,interfacial fracture and nugget pullout.Other than mild steel or normal high strength steel,in the shearing tensile test,hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure,welding soft zone and the porosity level of fusion zone.
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