Experimental study on electrode wear mechanism in resistance spot welding of high strength hot galvanization steels

Surface alloying mechanism on the electrode end face was complex and its wear was serious in welding of high strength hot galvanization steel.Elements composition and metallography experiment of the worn electrode were carried out to study the alloying on electrode end surface and microstructure evolvement.It was shown that the elements of Al, Zn etc were found in alloying layer.Different alloys were formed for different contents of Al, Zn at different temperatures, which decreased conductivity and heat conduction on electrode face.Al in coating was one of the main reasons that led to serious electrode wear.Pitting was grown obviously and micro cracks were produced at pitting region for higher temperature and pressure, the molten metal in coating penetrated into the electrode interior and accelerated electrode invalidation.The metal structure in recrystallization region was changed from columnar crystal to equiaxed crystal, which decreased hardness and anti-plastic deformation capability of electrode.