Characteristics of CO2 Laser Welded TRIP Steel Sheet

Abstract

Characteristics of CO2 laser welded 1000 MPa grade Transformation Induced Plasticity steel plate were investigated under different welding power, welding speed and shield gas. Decreasing welding power, increasing welding speed or using mixed shield gas (Ar+He) all reduced the porosity in the weld metal (WM). The weld metal and HAZ near the WM had maximum hardness. In tensile strength test of load perpendicular to the weld axis, the specimens had same tensile properties as that of the raw material. For the load parallel with the weld axis, the specimens prepared with Ar had equal yield strength (YS) and tensile strength (TS) to that of the raw material. But the elongation was lower than that of the raw material. The specimens prepared with shield gas He had higher YS, TS and lower elongation compared with that of the raw material. The welded joint had lower formability than that of the raw material. The formability of specimens prepared with low welding power or mixed shield gas Ar+He was improved compared with that of the specimens prepared using high power or single shield gas Ar.