Effect of process parameters on optimum welding condition of DP590 steel by friction stir welding

In the automotive industry, vehicle weight reduction techniques have been actively studied to improve the rate of fuel consumption and to cope with the regulation restricting exhaust gas. For this reason, advanced high-strength steel (AHSS) is preferred in the automobile industry as its tensile strength is 590 MPa and over. In this study, to obtain the optimum welding condition, the friction stir welding (FSW) process applied to AHSS was considered. The FSW experiment was performed on a stir plate using a Si3N4 tool and a 1.4-mm-thick DP590 steel sheet manufactured by cold rolling. In addition, to investigate the temperature distribution of the advancing and retreating sides in the welding state, the tool rotation speed of 800 rpm, and the welding speed of 180 mm/min, a K-type thermocouple was inserted in the backing plate, and the peak temperature was evaluated at each point. Especially, the correlation between the heat input per unit length and the formation of the FSW zone was minutely analyzed.