Zero-gap laser welding of zinc coated steels in a lap joint configuration

Abstract

Zinc coated steels, which provide excellent corrosion resistance, are increasingly used in the automotive industry. Due to the lower boiling point of zinc (906°C) than the melting point of steel (over 1300°C), a highly-pressurized zinc vapor is always produced during zero-gap lap joint laser welding process. In order to weld zinc coated steels in lap joint configuration, a gap with 0.1 mm-0.2mm thick is usually required, which provides a passage for a highly-pressurized zinc vapor to escape.In this paper, an innovative laser welding technique has been developed to weld zinc coated steels in a zero-gap lap joint configuration. High quality welds were achieved. The key is to consistently produce a stable keyhole assisted by an external vacuum system. Through the stable keyhole, the highly-pressurized zinc vapor was vent out from the faying surface. Mechanical properties of the welds were evaluated by the tensile shear test and hardness measurement. Microstructure is analysed by optical microscopy.Zinc coated steels, which provide excellent corrosion resistance, are increasingly used in the automotive industry. Due to the lower boiling point of zinc (906°C) than the melting point of steel (over 1300°C), a highly-pressurized zinc vapor is always produced during zero-gap lap joint laser welding process. In order to weld zinc coated steels in lap joint configuration, a gap with 0.1 mm-0.2mm thick is usually required, which provides a passage for a highly-pressurized zinc vapor to escape.In this paper, an innovative laser welding technique has been developed to weld zinc coated steels in a zero-gap lap joint configuration. High quality welds were achieved. The key is to consistently produce a stable keyhole assisted by an external vacuum system. Through the stable keyhole, the highly-pressurized zinc vapor was vent out from the faying surface. Mechanical properties of the welds were evaluated by the tensile shear test and hardness measurement. Microstructure is analysed by optical microscopy.