3. The valve body adopts high-quality steel castings, both ends of which are processed into U-shaped groove and directly butt welding with pipes. The chemical composition and properties of the two materials are similar, and the welding performance is excellent, without welding the intermediate itD;The four-open ring adopts 38CrMoAlA to resist nitriding, ensure its thermal strength, wear resistance, corrosion resistance, scratch prevention, easy to disassemble and assemble;Middle cavity self-sealing washer, high temperature steam corrugated asbestos washer, internal braid 18-8 filament to ensure sealing and prolong service life;Surface welding 1Cr18Ni9Ti, anti-rust, anti-erosion, multiple tests can ensure the seal.