... gradually along the seat, have cut off function to realized reliable sealing. 2, used thermometal for valve and semi ball, weld different alloy ... longevity.Valve materials Body material : WCB,LCB,304, 316,WC9 Semi-ball material : WCB+chrome, 304+HF, 316+HF,F22a+HF ... material : 420, 304,316, F22a, PTFEApplicable standard for Valve :Design and Manufacture according to: API608 Length of Face to face : ASME ...