아연도금강판 SGAPH440 소재의 MAG 및 LASER 용접특성 평가

Abstract

Lower-Arm is one of the critical components in automotive suspension module. It plays an important role on the effect of absorbing and relaxing the vibration and also it influences in wheel alignment. Generally the production of Lower-Arm is used MAG welding after fixing the component with jig system. The tails-end process is needed due to the foundational problems in the welding process such as spatters and weld defects in porosities and weld shapes. These problems increase working hours and production expenses. Therefore, the purpose of this study is to verify the effects on welding process of MAG and LASER welding and analyze the weldability. Lap-joint fillet was applied to weld two 2mm thick Galvannealed Steel sheets (SGAPH440) which has been used in actual Lower-Arm. The mechanical and metallurgical properties were considered to evaluate each step of the welding process. Two solid wires with differently chemical composition rate of 0.19% and 0.22% of Silicon(Si) and Manganese(Mn) were used in MAG welding. In this case, more spatters were observed from the solid wire containing more Mn and Si. The weldability was evaluated in terms of Bead. There is no lack of penetration, fairly fine porosity and good penetration were observed in all conditions. However, there were more spatters in KC solid wire than MC solid wire. Welded joints quality was evaluated according to ISO 5817(Undercut, Porosity, Lack of penetration, Excessive throat thickness) and ISO 13919-1(Porosity, Lack of fusion, Deviation from specified joint axis). The result for estimate welded joints could be obtained quality level for stringent(B) in MAG and LASER. The highest tensile-shear strength of the MAG welded joints was 18.1kN and LASER welded joints was 16.7kN. The highest hardness values were proved that 230.3Hv in MAG and 293.5HV in LASER.