Magnetic pulse welding conditions for high-tensile steel of 1 GPa class and 6061-T6 aluminum alloy sheets

The 6061-T6 sheet and the DP 780 steel sheet were joined under the condition with the gap length d of 1.17 to 1.42 mm and discharge energy W of 3.0 kJ. The impact speed ranged from 430 to 460 m/s. The weld width showed a tendency to increase due to the increase of the collision speed. However, when the gap length exceeds 1.59 mm (impact speed of >460 m/s), the weld width became narrow. Considering that the electromagnetic force continues to apply on the flyer sheet after collides with the fixed sheet, it is desirable to perform the welding in a time shorter than the time tm when the collision time reaches the maximum current value. Therefore, the collision time is considered to be one of factors that affect the welding condition. As a result of experiments in consideration of above conditions, it was possible to achieve a strong lap joint of the 6061-T6 sheet and the DP 980 steel sheet, although the welding condition was limited as compared with the case of the DP 780 steel sheet. Thus, sound lap joint between 6061-T6 sheet and high-tensile steel sheet with 1 GPa class was achieved by magnetic pulse welding.