Abstract: In order to improve the penetration of laser arc hybrid welding, activating laser arc hybrid welding is proposed. The surface of weld is melted by the tiny laser power protected by oxygen; as a result, there is a layer of oxide on the surface. Then laser arc hybrid welding is used to cover the weld, which can increase the penetration. Results show that the penetration of laser arc hybrid welding is increased about twice. The formation of the weld surface is elegant. The content of oxygen will be increased when surface of weld is melted by laser. The temperature dependence of surface tension gradient can be changed from a negative value to a positive value by oxygen which can increase the penetration. The influence of welding parameters on the welding melts depth and the width is studied. Increasing the preheated power of laser conditioning can increase penetration and reduce the width. Increasing arc current can increase the width and depth of molten weld. The increase of welding speed can reduce the width and depth of molten weld .The increase laser power of hybrid welding can increase the weld penetration and have little influence on the width. Tiny microstructures of weld metal can be produced by activating laser arc hybrid welding, which can improve the tensile strength. The tensile strength of activating laser arc hybrid weld joint can reach 95% of base metal. No crack or defects are noticed on the surfaces during bending experiment, this observation confirms that the toughness of the weld joint is good.

Key words: active welding, fiber laser, hybrid welding, microstructure and properties, stainless steel