ASTM A351/A351M

Overview

ASTM A351/A351M is the key ASTM International standard that defines requirements for austenitic stainless steel castings (and some austenitic-ferritic duplex grades) used in pressure-containing components such as valves, flanges, fittings, pump casings, and similar parts.

These castings are designed for service in corrosive environments, high temperatures, or where good weldability and mechanical integrity are required. The standard ensures consistent chemical composition, mechanical properties, heat treatment, and quality.

Latest edition (as of 2026): ASTM A351/A351M-24e1 (published May 2024, with editorial updates).

Scope & Purpose

Covers austenitic (primarily 300-series equivalents) and some austenitic-ferritic (duplex) steel castings
Intended for pressure-containing parts: valves, flanges, fittings, pumps, etc.
Focuses on corrosion resistance, weldability (low-carbon grades), and pressure integrity
Does not cover carbon/low-alloy steels (see ASTM A216) or ferritic/martensitic grades (see ASTM A352/A217)

Common Grades & Equivalents

Grade	UNS	Wrought Equivalent	Key Features	Typical Applications
CF3	J92700	304L	Low carbon (≤0.03% C)	General corrosion, excellent weldability
CF8	J92600	304	Standard 18-8 stainless	General purpose
CF3M	J92800	316L	Low C + 2-3% Mo	Pitting/crevice resistance in chlorides
CF8M	J92900	316	2-3% Mo (higher C)	Marine, chemical, pharma, food
CF8C	J92710	347/348	Nb-stabilized	High-temperature service
CF3MN	J92804	316LN	Low C + Nitrogen	Higher strength + corrosion resistance

Key Requirements

Chemical Composition

Strict limits per grade (e.g., low C in "3" suffix grades for weldability; Mo for pitting resistance).

Mechanical Properties (Min, Room Temp)

Tensile Strength: 70 ksi (485 MPa)
Yield Strength: 30 ksi (205 MPa)
Elongation: 30% min

Heat Treatment: Solution annealing + rapid cooling (water quench typical)
Testing: Tensile, chemical analysis, optional ferrite content, intergranular corrosion tests, NDE (radiography, etc.)
Supplementary Requirements: Optional (e.g., impact testing, additional ferrite measurement)

Why It Matters in Industry

Nearly all major valve manufacturers reference ASTM A351 for stainless steel cast bodies and bonnets (e.g., in API 600 gate valves, API 594 check valves, ball valves, etc.).

Grades like CF8M and CF3M are dominant in chemical processing, oil & gas, pharmaceutical, food & beverage, marine, desalination, and power generation.

Ensures cast components meet ASME B16.34, API, and pressure vessel code requirements for safety and performance.