Research On The Measurement And Welding Characterization Of Dynamic Resistance In Spot Welding Of Dual Phase Steel

The dual phase steel has high strength, high toughness, and good corrosion as well as good weldability. It has been widely used in automotive body manufacturing. It is very important to study the resistance spot welding of dual phase steel for the safety of the automotive body and lightweight of automobile. In this paper, the resistance spot welding of Dual Phase Steel600is researched, the relationship between the welding parameters and spot welding quality is detailedly studied through dynamic resistance testing, and the temperature field in resistance spot welding and nugget formation process is attentively analyzed through the thermoelectric finite element numerical simulation. Comparative analysis of the experimental study and numerical simulation study conclusions provide the basis for online monitoring of resistance spot welding.Collecting the critical welding parameters of the welding current and the inter-electrode voltage through constructing welding parameter data acquisition system, combined with the dynamic resistance curve, dynamic resistance variation law is studied, and the influence of welding current and electrode pressure on the dynamic resistance is analyzed and summarized, at the same time, dynamic resistance variation law when weld splashing and cold joint happens is also discussed. This provides a basis for the use of dynamic resistance to monitoring the quality of resistance spot welding of dual phase steel.The nugget growth process and temperature field results are obtained from resistance spot welding thermoelectric numerical simulation which is based on two-dimensional axisymmetric model fully considered boundary conditions, thermoelectric parameters of material, latent heat of phase transition, the effect of contact resistance and the loading of welding current. Within a certain range, the welding current and the nugget size are positive correlation. Nugget formation process undergone three stages, they are plastic adhesion stage, rapid growth stage and slow growth stage. The radial growth of the nugget has volatility and its growth rate is significantly greater than the axial growth rate.It can be concluded from the comparative analysis of the experimental value and numerical simulation value of the nugget under different welding parameters that the nugget diameter variation and specific dimensions coincided well when weldment splash and over firing didn’t occur. This verified the accuracy of the thermoelectric simulation analysis.