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Gray cast iron used for producing the low-pressure valves, suitable for pressure below than PN1.0MPa and not larger than PN1.6MPa unless the small size valves can be used. And temperature usually between -10-100℃, can't exceed this temperature, otherwise, the valve body will be broken. The common medium is water, also can be used for gas, ammonia, air and etc. The disadvantage for gray cast iron is poor tensile resistance, easy to break, unmalleable; the advantage is low cost, cheap price. The valves with gray cast iron can’t be used for hydrochloric acid, nitric acid and other corrosive media, but can be used for concentrated sulfuric acid media.
Malleable cast iron is suitable for working condition with pressure of PN2.5MPa, have certain tensile resistance, malleable function, working temperature can reach to 300℃, and the working medium is same as the gray cast iron.
Spheroidal graphite cast iron's character is using temperature keeping same as malleable cast iron, and its advantage is suitable for working condition with medium of sulfuric acid, nitric acid, acid salt and etc. And the material is malleable, with good tensile resistance, working pressure below 25kg.
Carbon steel is used for medium of oil, steam and no corrosive gas, air, liquid, and working temperature is between -29~425℃. It have good tensile resistance, usually used from low pressure to high pressure, and used widely, working pressure is between PN1.0MPa-42MPa.
Stainless steel valve is suitable for steam and oil with high temperature between -196℃~650℃; also can be used in weakly corrosive medium with temperature between -30~200℃. 316 and 316L optimize material base on 304, with better corrosion resistance, usually used in acetic acid and other corrosive medium. And 321 stainless steel has strong corrosion resistance to stainless steel intergranular corrosion.
Brass usually used for water heating system, pressure under 16kg. Red copper and copper alloy suit for oxygen, seawater and other corrosive oxidizing media, and they have good corrosion resistance for organic matter and etc. Cannot be used for medium of nitric acid, concentrated sulfuric acid, and forbid to contact with ammonia because have no resistance to it. Now, you can easily solve the problem: brass vs stainless steel ball valve, which one should I buy?
Aluminum alloy have good corrosion resistance for strong oxidation of concentrated sulfuric acid, the higher the purity of aluminum, the better its corrosion resistance. But compared with stainless steel, its ability is much lower, generally used for lower corrosive media. Aluminum alloy valves are generally used in tank cars, because of the light weight of the valve body.
Ceramic material have good corrosion resistance and wear-resisting property, but its disadvantage is that it can be only used in low pressure conditions, generally as lining materials.
Fiberglass reinforced plastic,such as epoxy resin FRP can be used in hydrochloric acid, oleic acid and other media, with good corrosion resistance, pressure under 10kg.
Plastic valves, with good corrosion resistance but poor pressure resistance, it can't be used in strong acid, alkali and other corrosive media, working temperature usually under 100℃.
PTFE, F46 are lining materials, have good corrosive function and used widely.
Manufacturer should consider the medium's concentration, temperature, pressure and other factors first, then choosing the materials.
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