Industrial Valve Materials Guide: Carbon Steel, Stainless Steel, Alloy Steel and Exotic Alloys

The material of construction for industrial valves must be carefully selected to withstand the process fluid, operating pressure, temperature, and environmental conditions in service. Using an incorrect material can lead to corrosion failure, stress corrosion cracking, hydrogen embrittlement, or mechanical failure — all of which can have catastrophic consequences in high-pressure or toxic service. This guide covers the most commonly specified valve body and trim materials.

Carbon Steel Valve Materials

ASTM A216 WCB — The Standard Industrial Valve Body

WCB (Weld Carbon B) is by far the most commonly specified valve body material globally. It is a cast carbon steel grade with good strength, weldability, and machinability, suitable for temperatures from -29°C to +425°C. WCB is used in oil and gas, water, steam, and general industrial service where corrosion is not a primary concern.

Key properties: Yield strength 250 MPa minimum, UTS 485–655 MPa, excellent weldability, PWHT required for sour service. ASME B16.34 Class 150–2500 ratings available.

ASTM A352 LCB / LCC — Low Temperature Carbon Steel

LCB and LCC grades are nickel-alloyed carbon steel castings for low-temperature service, rated to -46°C (LCB) and -40°C (LCC) without impact test waiver. Used for valves in cold climate installations, LNG receiving terminals, and cryogenic process lines.

Stainless Steel Valve Materials

ASTM A351 CF8 (SS304) and CF8M (SS316)

CF8 (cast equivalent of SS304) and CF8M (cast equivalent of SS316) are the most widely used stainless steel valve body materials. The addition of molybdenum in CF8M/SS316 provides significantly better resistance to chloride pitting corrosion and is the standard choice for seawater, chemical, pharmaceutical, and food industry valve applications.

Temperature range: -196°C to +425°C. Not suitable for temperatures between 400°C and 900°C (sensitisation and carbide precipitation) unless low-carbon grades (CF3, CF3M) or stabilised grades are used.

ASTM A351 CF3 / CF3M — Low-Carbon SS for Welding

The low-carbon variants CF3 (SS304L) and CF3M (SS316L) are used where welding is required and no post-weld heat treatment is practical. Mandatory for pharmaceutical and food industry valves (ASME BPE service) and for valves that will be field-welded into process piping.

Alloy Steel Valve Materials for High Temperature

ASTM A217 WC6 and WC9 — Chrome-Moly Alloy Steel

WC6 (1.25% Cr, 0.5% Mo) and WC9 (2.25% Cr, 1% Mo) are the standard valve body materials for high-temperature service in power plants and petrochemical plants. These chrome-moly grades maintain strength at elevated temperatures and resist oxidation and sulphidation. WC9 is the most commonly specified grade for power plant main steam, reheat steam, and boiler feedwater service.

Temperature range: WC6 up to 593°C, WC9 up to 593°C per ASME B16.34 tables. Post-weld heat treatment (PWHT) is mandatory.

ASTM A217 C5 and C12 — High Chrome Alloy Steel

C5 (5% Cr, 0.5% Mo) and C12 (9% Cr, 1% Mo) are used for valves in high-temperature hydrogen service (to resist hydrogen attack) and in high-sulphidation environments such as crude oil and heavy vacuum residue service in refineries.

Duplex and Super Duplex Stainless Steel

ASTM A890 Grades (CD3MN, CD3MWCuN)

Duplex stainless steels (PREN ≥ 35) and super duplex grades (PREN ≥ 40) combine the corrosion resistance of austenitic stainless with higher yield strength (approximately twice that of 316SS). They are the material of choice for offshore and subsea valves, seawater service, and chemical environments with high chloride content.

Temperature range: -50°C to +300°C (duplex) / -50°C to +250°C (super duplex, thermal age-hardening risk above 300°C).

Exotic Alloys for Severe Corrosion Service

Sour Service: NACE MR0175 / ISO 15156

Valves used in oil and gas production containing hydrogen sulphide (H2S) — known as sour service — must comply with NACE MR0175 / ISO 15156. This standard specifies maximum hardness limits for all metallic components (body, trim, bolting) to prevent sulphide stress corrosion cracking (SSCC). For carbon steel valves in sour service: maximum hardness HRC 22 (Brinell 237 HB) for body and bonnet, with strictly controlled chemistry and heat treatment.

Valve Trim Materials

Valve trim (ball/disc/gate, stem, seat ring) material must be selected independently from the body material. Common trim combinations include: WCB body with SS316 trim (standard); WCB body with Stellite-faced trim (for high-temperature steam); CF8M body with Hastelloy C-276 trim (for concentrated acids); and LCB body with SS316 cryogenic trim (for cold service).