The selection of valve materials should be determined according to the corrosiveness, temperature, pressure and other characteristics of the medium. The following are common materials and their applicable media:
1. Cast iron (gray cast iron, ductile iron)
Characteristics: low cost, general corrosion resistance, not resistant to high temperature and high pressure.
Applicable media: water, sewage, air, steam (temperature ≤200℃, pressure ≤1.6MPa). Neutral gas or weakly corrosive liquid (such as mild acid and alkali solution).
Inapplicable media: highly corrosive media (such as concentrated hydrochloric acid, sulfuric acid), high pressure conditions.
2. Carbon steel (WCB, A105, etc.)
Characteristics: high strength, good temperature resistance (-29℃~425℃), but not corrosion resistant. Applicable media: water, steam (high-pressure steam needs to control the temperature ≤425℃), oil and gas, natural gas. Non-corrosive or weakly corrosive gases (such as air, nitrogen). Typical scenarios: petroleum refining, heating pipelines, natural gas transportation.
3. Stainless steel (304, 316, 316L, etc.)
Features: Strong corrosion resistance, 316/316L has better resistance to chloride ion corrosion than 304.
Applicable media
304: nitric acid, food-grade media, water, weak organic acid. 316/316L: seawater, chloride ion solution (such as brine), sulfuric acid (low concentration), acetic acid. Typical scenarios: chemical industry, seawater treatment, food and medicine industry.
4. Duplex stainless steel (2205, 2507)
Features: ferrite + austenite duplex structure, high strength (yield strength ≥ 450MPa), better resistance to chloride ion stress corrosion than 316L.
Applicable media Seawater and brine containing chloride ions (such as marine engineering, chlor-alkali industry). Oil and gas media containing hydrogen sulfide (H2S) (must comply with NACE MR0175 standard). Medium concentration of sulfuric acid and nitric acid solution.
Typical scenarios: offshore platform valves, petrochemical desulfurization equipment.
5. Super austenitic stainless steel (904L, 254SMO)
Features: high nickel and molybdenum content, strong resistance to pitting and crevice corrosion (pitting index PREN>40).
Applicable media: concentrated phosphoric acid, dilute sulfuric acid (temperature ≤60℃), organic acids (such as formic acid, acetic acid). Chloride solution (such as papermaking bleaching liquid, brine in food processing).
Typical scenarios: food industry, papermaking equipment, chemical corrosion-resistant pipelines.
6. Zirconium alloy (Zr702, Zr705)
Features: corrosion resistance is close to that of titanium alloy, but the performance is better in high-temperature hydrochloric acid, and the cost is higher than stainless steel.
Applicable media: high-temperature hydrochloric acid (concentration ≤30%, temperature ≤150℃), sulfuric acid (concentration ≤70%). Molten alkali, strong oxidants (such as nitric acid).
Typical scenarios: chemical reactors, nuclear industry valves (radiation resistant).
7. Alloy steel (1Cr5Mo, 12Cr1MoV, etc.)
Features: high temperature and high pressure resistance, creep resistance, some grades have strong corrosion resistance. Applicable media high temperature steam (temperature ≤ 550℃), superheated steam, petroleum cracking gas. Sulfur-containing oil and gas (such as H2S medium, sulfur-resistant materials must be selected). Typical scenarios: power stations, high-pressure boilers, and petroleum refining.
8. Copper alloy (brass, bronze)
Features: good thermal conductivity, seawater corrosion resistance, and low strength. Applicable media seawater, fresh water, oxygen, and low-temperature liquids (such as liquid oxygen). Weakly corrosive media such as dilute sulfuric acid and acetic acid. Typical scenarios: ships, seawater desalination, instrument valves.
9. Special alloys (titanium alloy, Hastelloy alloy, monel alloy) Applicable media titanium alloy: seawater, wet chlorine, hypochlorite. Hastelloy alloy (C-276): concentrated hydrochloric acid, sulfuric acid, aqua regia, strong oxidants. Monel alloy: hydrofluoric acid, fluoride solution, seawater.
Features: strong corrosion resistance, high temperature resistance, high cost.