Modeling and process analysis of resistance spot welded DP600 joints based on regression analysis

Dual-phase steel has been used in many industrial fields because of its high strength, low yield ratio and good welding performance. In this paper, a novel framework for welding quality prediction and analysis was proposed by using statistical analysis techniques. The relationship between the welding process parameters (welding time, welding current and electrode force) and the nugget diameter of resistance spot welded dual-phase steel DP600 with a thickness of 1.7mm was obtained by means of nonlinear stepwise regression analysis. The effects and interactions of the welding process parameters on the nugget diameter were discussed. The critical nugget diameter induced pullout failure mode was obtained based on stress analysis of the nugget during a tensile-shear test. The undesired and satisfying combinations of process parameters for the interfacial and pullout failure mode of the welded joints were obtained using the model; the mechanical properties, microstructure and microhardness of the welding joints for the verification tests were also investigated. [Display omitted] •The relationship between welding parameters and nugget diameter was quadratic in the range discussed.•The critical nugget diameter for the IF mode that transformed into the PF mode was 3.51 multiples of the thickness of steel.•The suitable process parameter combination was the one resulting in the nugget whose diameter was larger than 5.97mm.•Both the fusion zone and the heat affected zone mainly consisted of a martensitic structure.