Home

ASTM A320 / A320M Standard Summary & PDF Reference

Low-Temperature Bolting Specification (latest edition: A320/A320M-22)

ASTM A320 / A320M-22 is the standard specification for alloy-steel and stainless-steel bolting materials intended for low-temperature service. The standard covers rolled, forged, or strain-hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. Originally approved in 1948, ASTM A320 is published jointly with its metric companion A320M and is equivalent to ASME SA-320 in the ASME Boiler and Pressure Vessel Code, Section II Part A.

Scope

The specification applies to bolting materials used at low service temperatures where notch toughness is required. It covers two material families: ferritic and martensitic alloy steels (the L-series) and austenitic stainless steels (the B-series). Charpy V-notch impact testing is mandatory for the alloy-steel grades.

Grades covered

Grade L7 (UNS G41400) AISI 4140 / 4142 chromium-molybdenum alloy steel
Grade L7M (UNS G41400) tempered AISI 4140 / 4142 for sour service
Grade L7A (UNS G40370) AISI 4037 alloy steel
Grade L7B (UNS G41370) AISI 4137 alloy steel
Grade L7C (UNS G87400) AISI 8740 Ni-Cr-Mo alloy steel
Grade L43 (UNS G43400) AISI 4340 Ni-Cr-Mo alloy steel
Grades L70 / L71 / L72 / L73 ASME Section II equivalents of L7 / L7A / L7B / L7C
Grade L1 low-carbon alloy steel for moderate-strength service
Grade B8 (UNS S30400) AISI 304 austenitic stainless steel
Grade B8M (UNS S31600) AISI 316 molybdenum-bearing stainless
Grade B8C (UNS S34700) AISI 347 niobium-stabilized stainless
Grade B8F (UNS S30300) AISI 303 free-machining stainless
Grade B8P (UNS S30500) AISI 305 low-work-hardening stainless
Grade B8T (UNS S32100) AISI 321 titanium-stabilized stainless
Grade B8LN (UNS S30451) 304LN low-carbon nitrogen-strengthened
Grade B8MLN (UNS S31653) 316LN low-carbon nitrogen-strengthened

PDF datasheets by grade

Per-grade PDF datasheets are available from the TorqBolt product reference library: