Forged steel gate valve has three kinds of bonnet design, the first is a bolt-type valve bonnet, connected by concave and convex surface, stainless steel with flexible graphite spiral wound gasket, ring can also be used on request connection, the second is the welding bonnet, Sealing by thread after welding, according to demand can also be used directly rigid welding, the third is self-sealing bonnet, threaded and self-sealing bonnet connection.