Stainless steel butt welding elbow before welding, butt welding elbow in order to avoid welding deformation, the group into an integral elbow on both sides of the outermost tile at both ends of the alignment, with stainless steel arc plate and keel reinforcement. According to the conventional welding method, argon filled welding is needed. Considering the welding cost and the large diameter of the waist pipe of a small rice, it is difficult to fill with argon. Considering the above factors, two welders inside and outside should be used to weld symmetrically at the same time, which not only solves the problem of argon filled well, but also gives a good shape. Argon spot welding process is adopted. Welding rod A022 and welding wire: HOOCr21Nil0. The bottom layer is argon arc welding. Before electric welding operation, brush chalk on the left and right sides of the welding seam within 100mm to prevent spatter and adhesion on the pipe surface. Before electric welding operation, use small current. Multilayer, multi-channel, continuous welding. After the overall welding, polish the welding spot and splash on the surface of the welding elbow, conduct non-destructive inspection on the prefabricated welded tile, and pickling and passivation on the surface of the internal and external welds. Transport the pickling elbow to the installation site for on-site installation.