The addition of an appropriate amount of nitrogen to F51 stainless steel not only improves the pitting and SCC resistance of the steel, but also does not significantly reduce the plastic toughness due to the severe coarsening of the grains in the heat affected zone of the weld, and is also insensitive to welding hot cracks. Therefore, the corrosion resistance and mechanical properties of the heat affected zone of the weld are improved. The SCC resistance, wear corrosion resistance and corrosion fatigue resistance in many media are better than those of austenitic stainless steel [1-5]. In particular, the SCC resistance in a Cl-containing environment is particularly excellent [6]. The H2S SCC resistance is better than that of S30403 and S31603.The extended branch seat, also called the short pipe branch seat Nipolet, is commonly used for valve installation and exhaust. The thickness is available in two grades, XS and XXS, with nominal sizes ranging from 1/2 inch to 5 inches, and the ends are sockets or external threads.The branch seat body is made of high-quality forgings, and the materials used are the same as the pipe materials, including carbon steel, alloy steel, stainless steel and other materials.