ASTM A351

USED FOR:

Governs austenitic and austenitic-ferritic (duplex) stainless steel castings for pressure-containing parts: primarily valve bodies, bonnets, pump casings, and similar cast components –  used in corrosion-resistant and high-temperature service.

This is a casting specification, distinct from ASTM A182’s forged stainless steel components and ASTM A217’s chromium-molybdenum alloy steel castings. It applies primarily to austenitic stainless steel castings and also includes certain duplex stainless steel grades.

RELATED STANDARDS:

• Sibling specs: ASTM A216 covers carbon steel castings for moderate-temperature, non-corrosive service; ASTM A217 covers martensitic/low-alloy castings for elevated-temperature creep service where corrosion resistance isn’t the driver; A351 is the casting counterpart to A182’s A351 is the casting counterpart to several ASTM A182 stainless steel forging grades, such as F304 and F316. Duplex casting grades covered by ASTM A351 should be compared with the corresponding duplex wrought grades only where chemistry and properties are equivalent.
• Design code that invokes it: ASME B16.34 references A351 as a listed valve body/bonnet material, ASME B31.3 and ASME B31.1 use allowable stresses from ASME Section II Part D for applicable SA-351 grades used in pressure design. Valve pressure-temperature ratings are established through product standards such as ASME B16.34.
• Dimensional standard that pairs with it: ASME B16.34 governs valve pressure-temperature ratings and wall thickness requirements; as with A217, there’s no separate pipe-schedule dimensional standard since A351 castings are typically valve/pump components with geometry set by the component design itself.

GRADE / TYPE RANGE:
A351 covers austenitic stainless steel casting grades including CF8 (similar in chemistry to Type 304), CF8M (similar in chemistry to Type 316), CF3 and CF3M low-carbon variants, CF8C stabilized grades, and selected duplex stainless steel grades such as CD3MN and CD4MCu, with added molybdenum for improved pitting/crevice corrosion resistance), CF3 and CF3M (low-carbon “L” equivalents of the above, for resistance to sensitization after welding), CF8C (stabilized with columbium/niobium, analogous to 347), and duplex grades such as CD3MN and CD4MCu, which offer higher strength and superior chloride stress corrosion cracking resistance compared to standard austenitics.

As with the wrought grades, the low-carbon “C”-suffix variants trade a modest reduction in high-temperature strength for resistance to carbide precipitation and intergranular corrosion in welded or heat-affected areas, while the duplex grades demand tighter control of ferrite content and heat treatment to achieve their characteristic two-phase microstructure and associated strength/corrosion balance.

Grade selection tracks the same logic as A182’s stainless F-grades, chloride content, sour species, welding/PWHT exposure, and whether duplex-level SCC resistance is warranted.

DESCRIPTION:
A351 covers austenitic and duplex stainless steel castings for valves, pump casings, and similar pressure-retaining components, produced by casting (sand, investment, or centrifugal casting depending on the part) and typically solution-annealed and water-quenched to redissolve carbides and restore optimal corrosion resistance a heat treatment step that is essential to the alloy’s performance, not optional.

The standard specifies chemical composition ranges per grade, mechanical property requirements (tensile, yield, elongation), and casting quality provisions including radiographic or liquid penetrant examination of critical wetted or pressure-boundary surfaces, along with defined weld repair procedures and limits, which, as with other casting standards, are a routine and expected part of casting manufacture rather than an exception.

It also addresses hydrostatic testing where applicable and marking requirements for grade, heat, and manufacturer traceability, with grade identification being particularly important given how visually similar CF8 and CF8M (or CF3 and CF3M) castings can be without proper documentation.

TYPICAL INDUSTRY USE:
Widely used in chemical processing, offshore/marine, pharmaceutical, and food-grade piping systems for cast stainless valve bodies and pump casings wherever corrosion resistance is the primary driver, and in cryogenic service where austenitic stainless retains toughness at low temperature.

IMPORTANT NOTES:

• We saw CF8 specified or supplied where CF8M was required (or the low-carbon CF3/CF3M equivalents mixed up with their standard-carbon counterparts).The molybdenum and carbon content differences are critical to corrosion performance but easy to overlook on a quick document review, so we always verify grade against the actual process fluid chemistry.

• Supplementary requirements can add intergranular corrosion testing (particularly relevant for CF8/CF8M in sensitizing service, since as-cast microstructure behaves somewhat differently from wrought material), additional NDE, or ferrite content verification on duplex grades. 

• NACE MR0175/ISO 15156 compliance is a significant consideration for duplex grades (CD3MN, CD4MCu) in sour service, ferrite content, hardness, and solution heat treatment all interact to determine sour compliance, and we always request the specific ferrite scope/metallographic data and hardness survey.

• Weld repair is standard practice on A351 castings, but repairs on duplex grades require particularly careful control of heat input and post-repair solution annealing to avoid disturbing the austenite-ferrite balance.

• Because cast stainless components (like A217 castings) are typically non-repairable-in-service, fracture-critical parts, we apply the same rigorous MTR/NDE/weld-repair documentation review at receipt as we do for A217, with particular attention to confirming solution annealing was performed after any weld repair, since skipping this step can leave a sensitized, corrosion-susceptible zone.