Mechanical Characteristics of High Power CO2 Laser Welding Joints of Ultra-fine Grained High Strength Steel

Mechanical properties of laser welded ultra-fine grained high strength steel were examined using a 20 kW CO2 laser facility. The welded joints showed good tensile strength as all pieces were broken at the base metal. In CTOD test the critical CTOD value was the lowest at the weld metal. To prevent the fracture path deviation (FPD) in Charpy impact test, we used three-weld test assembly. The results confirmed that reduction in carbon quantity improved the weld metal toughness.