Abstract Scope |
The 304 austenitic stainless steel with a thickness of 7.5 mm was welded by high-power fiber laser welding. Firstly, the influence of process parameters on the macro-forming of welds was investigated. Secondly, the laser welding process was studied in detail through high-speed camera according to the typical welding beads forming state. Finally the microstructure and properties of the welded joints obtained by the optimized process were analyzed. The results showed that the process window was narrow, and defects such as welding pool depression and root humping often occured during penetration. There were both zero defocusing high-speed welding and large defocusing low-speed welding windows. The observation results of the welding process showed that the state of the keyhole determined the flow state of the molten pool. Zero defocusing high-speed welding conditions, the keyhole penetrated the base metal, the molten pool was small and the cooling rate was fast, so the molten metal remained in its original position. Large defocusing low-speed welding conditions, the large keyhole was stable without penetrating the base metal and the width of the root of the molten pool was large enough to avoid the formation of humping. Due to the FA solidification mode of the weld, the weld microstructure consisted of a large amount of austenite and a small amount of ferrite, hardness of the weld consisted of massive austenite was similar to that of base metal. The maximum tensile stress of the joint is 689.2 MPa, which is 98% of the base metal. Through the optimization of the laser welding process, the effective connection of 7.5mm 304 stainless steel plates can be realized. |