Microstructure and mechanical properties of dissimilar steel plate resistance plug welding joints

A new type of hybrid welding method called resistance plug welding （RPW） was firstly adopted to achieve the connecting of dissimilar steel,mainly as for the poor welding characteristics of high strength steel produced by increasing carbon,manganese, silicon, etc. Microstructures and mechanical properties of RPW joint were analyzed by optical microscope,micro-hardness test and shear tensile measurement. Experimental results indicate that the RPW joint has a rounded rectangle nugget,and the size is larger than elliptical nugget of resistance spot welding （RSW） joint; the hardness value of RPW joint is evenly distributed,accordingly there is no hard brittle phases; the shear tensile strength of RPW joint increases by 20% in comparison with RSW joint under the same welding conditions.