304L stainless steel pipes have very good plasticity and toughness, which determines that it has good bending, crimping and stamping formability, so it is easy to make various shapes of components, containers or pipes, and its welding workload is much larger than other stainless steels. This kind of steel with good toughness and plasticity does not undergo any quenching hardening, so although its linear expansion coefficient is much larger than that of carbon steel, the elastoplastic stress strain during the welding process is very large, but cold cracks rarely occur. There is no quenching hardening area in the welded joint of 304L stainless steel pipe, and because it has a strong work hardening ability, its tensile strength is still not low even if the area is softened by welding heat. However, there is an L σ three-phase zone in the solidification process of 304L stainless steel pipe fittings, and the solidification process is complex, so there are various controversies so far, so the systematic welding research also has certain theoretical significance. www.sy-pipe.com