ASTM A193

Covers — alloy-steel and stainless-steel bolting (studs, bolts) for high-temperature or high-pressure and special-purpose service: alloy grade B7/B16, stainless B8/B8M and their strain-hardened classes, with chemistry, mechanical properties, and heat treatment.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Matching nuts → ASTM A194.
• Low-temperature (impact-tested) bolting → ASTM A320 (L7).
• General-purpose low-strength bolting → ASTM A307.
• Bolt head/thread dimensions → ASME B18.2.1; joint assembly → ASME PCC-1.

A193 defines the bolt material and strength; pair it with the correct A194 nut and assemble to PCC-1.

A193 sets minimum requirements per bolting grade:

• Chemistry — alloy (Cr-Mo B7/B16) or austenitic stainless (B8/B8M) composition.
• Mechanical Properties — tensile/yield and hardness by grade and diameter (strength derates in large diameters for B7).
• Heat Treatment — quench-and-temper (B7/B16) or solution-anneal/strain-harden (B8/B8M classes).
• Testing & Marking — tension/hardness testing and grade/manufacturer marking on the bolt end.

ASTM A193 is the primary bolting material specification for high-temperature and high-pressure flanged joints. Grade B7 — quenched-and-tempered chromium-molybdenum — is the industry default stud, while B8/B8M (304/316 stainless) grades provide corrosion resistance at lower strength.

A193 defines the material; it is always used with a matching A194 nut and assembled to a controlled bolt load (ASME PCC-1). Because B7 has no impact requirement, low-temperature joints use A320 L7 instead, and B7 strength derates in large diameters.

Engineering Note: Always specify the bolt/nut pair together (B7 with 2H, B8 with 8) and confirm the minimum design temperature — an A193 B7 stud in cold service is a classic brittle-fracture risk.