For carbon steel gate valve, the seat is usually forged steel. The sealing surface of the seat is spray welded with hard alloy specified by the customer, Renewable threaded seat is used for NPS 10 gate valves, and welded on seat can be also optional if being requested by the customer, Welded on seat is used for NPS 10 carbon steel gate valves. For Stainless steel gate valve, integral seal is usually adopted, or to weld hard alloy directly integrally.