Special Alloy Valves: Materials, Properties, and Applications #
Special alloy valves are engineered to meet the demanding requirements of various industrial environments, offering enhanced resistance to corrosion, high temperatures, and aggressive chemicals. Below is an overview of the main categories of special alloy valves, their material characteristics, and typical applications.
Austenitic Stainless Steel #
| Designation | Material Characteristics | Typical Applications |
|---|---|---|
| A351-CF8 (304) | Highly resistant to corrosion from nitric acid and organic acids at ambient temperature. | Pulp and paper mills, chemical processes, seawater services. |
| A351-CG8M (317) | Excellent resistance to pitting and crevice corrosion; highly resistant to medium concentrations of boiling acetic acid and dilute hydrochloric acid. | Equipment for processing organic acids, oil pipelines, seawater services. |
| A351-CF3M (316L) A351-CN7M (Alloy 20) |
Superior resistance to stress corrosion cracking in 20%–40% sulfuric acid; resistant to phosphoric acid at any concentration, even when boiling. | Process equipment handling sulfuric acid and phosphoric acid. |
Duplex Stainless Steel #
| Designation | Material Characteristics | Typical Applications |
|---|---|---|
| A995-4A (CD3MN · S31803) | Outstanding corrosion resistance, combining the beneficial properties of austenitic and ferritic stainless steels. Features high ductility, toughness, strength, good resistance to intercrystalline and chloride stress corrosion, good weldability, and high thermal conductivity. S32760 contains higher levels of Cr, Mo, and N than S31803, with a PREN value of 40. | Process equipment in seawater systems, salt manufacturing, urea production, and other highly corrosive environments. |
| A995-6A (CD3MWCuN · S32760) | (See above for properties; S32760 is a higher alloyed duplex stainless steel.) | Same as above. |
Ni-Cu Alloy #
| Designation | Material Characteristics | Typical Applications |
|---|---|---|
| A494-M35-1 (Monel®) | Excellent corrosion resistance, especially to de-aerated hydrochloric and hydrofluoric acids, high-temperature seawater, and steam. Age-hardened M-25S offers superior galling resistance due to high silicon content. | Marine fixtures, chemical equipment exposed to hydrofluoric acid, seawater, and alkaline solutions. |
| A494-M35-2 (Monel®) A494-M25S (S Monel®) |
(See above for properties.) | Same as above. |
Ni-Cr-Mo Alloy #
| Designation | Material Characteristics | Typical Applications |
|---|---|---|
| A494-CW12MW (Hastelloy® C) | Resistant to oxidizing acids such as wet chlorine gas and chlorine dioxide, acetic acid, seawater, and brine solutions. Exceptional resistance to oxidizing atmospheres up to 1040°C. | Pulp and paper, food processing equipment, seawater services, and chemical equipment handling oxidizing acids. |
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