Effect of alloying elements on expulsion in electric resistance spot welding of advanced high strength steels

This study examined the effects of alloying elements, which are normally used to modify the composition of advanced high strength steels, on the expulsion phenomenon during resistance spot welding as well as the effects of alloying elements on the expulsion limit current (ELC). An equation for the ELC prediction was derived from the correlation between the ELC and alloying element: ELC (kA) =9.85-0.74Si-0.67Al-0.28C-0.20Mn-0.18Cr. The coefficient of determination between the calculated and measured values was sufficiently high (R-2 =0.94). The extent of the effects of the alloying elements on the ELC was in the order of Si, Al, C, Mn and Cr. From the correlations among the ELC and resistivity R, the coefficient of thermal expansion a and yield strength (YS1200 degrees C), the ELC was calculated to be ELC (kA) =9.3-0.057R-0.035 alpha+0.22YS(1200 degrees C), and the coefficient of determination was sufficiently high (R-2=0.96).