Laser - mig hybrid weldability of high stregnth steel for car industry

Abstract

To improve fuel efficiency, the high strength steel sheet was increased in car body. But high alloy contents in high strength steel caused some problem such as crack, porosity and insufficient dynamic property of weld joint. In this study, characteristics of weld were evaluated in laser and hybrid welding for 590MPa grade TRIP steel sheet. To evaluate the weld properties, metallurgical inspection, SEM, tensile test, formability test and high cycle fatigue test were conducted. The results were as follows. There was remarkable change of welding current and arc voltage wave form. Arc column and metal transfer was stabilized by laser induced plasma. The penetration depth was increased by laser - MIG hybrid welding. The bead width in hybrid welding was wider than laser welding. Tensile strength of hybrid welded specimen was lower slightly than laser welding. Erichsen value was decreased in hybrid welding. Because Si content of weld metal was decreased in hybrid welding. It was not clear that the high cycle fatigue property was improved by laser – MIG hybrid welding or not.To improve fuel efficiency, the high strength steel sheet was increased in car body. But high alloy contents in high strength steel caused some problem such as crack, porosity and insufficient dynamic property of weld joint. In this study, characteristics of weld were evaluated in laser and hybrid welding for 590MPa grade TRIP steel sheet. To evaluate the weld properties, metallurgical inspection, SEM, tensile test, formability test and high cycle fatigue test were conducted. The results were as follows. There was remarkable change of welding current and arc voltage wave form. Arc column and metal transfer was stabilized by laser induced plasma. The penetration depth was increased by laser - MIG hybrid welding. The bead width in hybrid welding was wider than laser welding. Tensile strength of hybrid welded specimen was lower slightly than laser welding. Erichsen value was decreased in hybrid welding. Because Si content of weld metal was decreased in hybrid welding. It was not clear that the high cycle fat...