LAUSR

Abstract Al-Si coated press-hardened steel (PHS) welding was carried out using fiber laser with Ar and air atmospheres under different atmospheres. The formation mechanism of δ -ferrite in welded seam (WS) was: the melting Al-Si coating diffused into molten pool such that the stabilization of high-temperature δ -ferrite was improved as well as the phase transformation ( δ  →  γ ) was restrained by the effect of laser rapid cooling. Al-content in δ -ferrite of WS with Ar atmospheres was more than air atmospheres, leading to less δ -ferrite. A few of oxygen and nitrogen were ionized and droplet reaction zone with strong dissolution did not occur during laser lap welding, so welding defects were not obtained. Moreover, O element reacted with Al in the molten pool to form oxides of less than 1 μm (Al 2 O 3 ), it did not deteriorate the properties of WS.