(1) Soft sealing material
A. Nitrile rubber (NBR). Nitrile rubber has excellent oil resistance; heat resistance is superior to natural rubber and styrene-butadiene rubber; air tightness and water resistance are better. Nitrile rubber can be divided into butyronitrile-18, butyronitrile-26 and butyronitrile-40. Nitrile rubber is suitable for petroleum products with a temperature of -60 ° C ~ +120 ° C, benzene, formaldehyde, water, acid, alkali medium.
B. Fluororubber (FKM OR VITON). Fluororubber is heat-resistant, acid-base resistant, oil-resistant, saturated water and steam, and has small compression set and good sealing. Fluororubber is suitable for petroleum products, water, acid and alcohol at temperatures from -30 °C to +220 °C.
C. Polytetrafluoroethylene (PTFE). PTFE is resistant to high temperature, chemical corrosion, and low friction coefficient, but has low mechanical strength, is easy to creep, and has low elasticity. It is suitable for corrosive media with a temperature of 170 ° C or less.
(2) Hard sealing material
A. Copper alloy. The copper alloy has good corrosion resistance and good wear resistance in water or steam clock. It is used in medium with PN≤1.6MPa and temperature not exceeding 200°C. It can be fixed on the body by the method of surfacing and casting. . Commonly used grades are ZCuAl10Fe3 (aluminum bronze), ZCuZn38Mn2Pb2 (cast brass).
B. Chrome stainless steel. Chromium stainless steel has good corrosion resistance and is usually used for water, steam and oil, and the temperature does not exceed 450 °C. Commonly used grades are 2Cr13, 1Cr13.
C. Stellite alloy. Sitali carbide corrosion resistance. It has excellent comprehensive properties such as erosion resistance and scratch resistance. It is suitable for various valves and temperature-268°C~+650°C, especially for highly corrosive media. One of the more rational sealing surface materials. Because of the high price, Stellite alloy uses surfacing.
D. Nickel base alloy. Nickel-based alloys are another important material in the field of corrosion resistance. They are commonly used as sealing materials in three parts: Monel, Hastelloy B and Hastelloy C.
Monel is the main material for the resistance to hydrofluoric acid corrosion. It is suitable for alkali, salt, food and air-free acid solvent media at temperatures from -240 ° C to +482 ° C.
Hastelloy B and Hastelloy C are the most comprehensive corrosion-resistant materials in valve sealing surface materials. They are suitable for corrosive mineral acids, sulfuric acid, phosphoric acid, wet HCI gas and strong oxidizing medium with temperature of 371 °C (hardness 14RC). Colleague, apply to chloric acid-free solution and strong oxidizing medium at 538 ° C (23 RC).
E. Iron-based alloy. Iron-based alloy is a newly developed sealing surface material in China. Its wear resistance and scratch resistance are better than 2Cr13, and it has certain corrosion resistance and can replace 2Cr13. Suitable for non-corrosive media with a temperature of 450 ° C or less. Commonly used grades are WF311, WF312 iron-based powder.