Experimental Study Of The Resistance Spot Weldability Of High Strength Dual Phase Steel

The adoption of lightweight high-strength dual phase steel is an effective way to reduce the vehicle weight, decrease fule consumption, enhance the strength of vehicle parts and ensure safe driving. Resistance spot welding (RSW) is an important process during the manufacturing of a vehicle body, and the qualities of these weld jionts in the vehicle body directly determine the automotive overall quality. So, in this paper, the influences of three main parameters (electrode force, welding current, welding time) on the weldability of a high strength dual-phace steel DP 600 were studied from the following aspects, which are macro-tensile-shear strength, tensile-shear failure mode, weld nugget size and metallographic observation.Firstly, the tensile-shear experiments and all the test and analysis experiments were conducted to study the nugget size, metallograph, micro-hardness, tensile-shear strength, failure mode and weld defects of the weld jionts, which are the main weldabilities. Then these experimental results were analized to find the influence laws of welding parameters on the properties of the weld joints. Further research was carried on about the possible reasons leading to these laws. And through the study of factors affecting the weld properties, the expressions of the tensile-shear strength of the weld joints with different failure modes were developed.In addition, through the experimental study of microscopic and mesoscopic metallograph of the weld joints, the influence laws of the metallographic structure on the properties of the weld joints were abtained. Then the pullout failure mode of the welds, the mechanical properties of the initial failure location and the factors affecting the tensile-shear strength of the weld joints were also studied. And a series of results with practical engineering value were concluded.