ASTM A320 / A320M is the standard specification for alloy steel and stainless steel bolting materials intended for low-temperature service. It covers rolled, forged, or strain-hardened bars, bolts, screws, studs, and stud bolts for pressure vessels, valves, flanges, and fittings.

What is the latest edition of ASTM A320?

The current edition is ASTM A320 / A320M-2024, published by ASTM International. It is equivalent to ASME SA-320 in the ASME Boiler and Pressure Vessel Code, Section II Part A.

Which grades does ASTM A320 cover?

ASTM A320 covers alloy steel grades L1, L7, L7M, L7A, L7B, L7C, L43, L70, L71, L72, L73 and austenitic stainless steel grades B8, B8M, B8C, B8F, B8P, B8T, B8LN, B8MLN, each in Class 1 (solution-treated) or Class 2 (strain-hardened) where applicable.

Is ASTM A320 the same as ASME SA-320?

Yes. ASME SA-320 is adopted by ASME from ASTM A320 without technical deviation. Both designations cover identical chemistry, mechanical properties, and Charpy V-notch impact requirements.

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ASTM A320 / A320M Bolting Specification PDF

Below is the complete specification document for ASTM A320 / A320M-2024, the standard for alloy steel and stainless steel bolting materials intended for low-temperature service.

What is ASTM A320 / A320M?

ASTM A320 / A320M is the standard specification published by ASTM International for alloy steel and stainless steel bolting materials intended for low-temperature service. Originally approved in 1948, the specification covers rolled, forged, or strain-hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. The latest edition is ASTM A320 / A320M-2024.

ASTM A320 versus ASME SA-320

ASME SA-320 is adopted by the American Society of Mechanical Engineers from ASTM A320 without technical deviation, and is published in the ASME Boiler and Pressure Vessel Code, Section II Part A. Specifying ASME SA-320 confers automatic acceptance under BPVC Section VIII Division 1 and Division 2 pressure-vessel construction. Project specifications for Saudi Aramco, ADNOC, Petrobras, Saipem and other operators typically cite the ASME SA-320 designation; commercial procurement frameworks typically cite the ASTM A320 designation. Material can be dual-stamped to satisfy both.

Grades covered by ASTM A320 / A320M-2024

The specification covers two material families. The alloy steel L-series is mandated to be Charpy V-notch impact tested at low temperatures; the austenitic stainless B-series is supplied in Class 1 (solution-treated) or Class 2 (strain-hardened) condition. Click any grade for the per-grade chemical, mechanical, and Charpy requirements.

Grade L7 (UNS G41400) AISI 4140 / 4142 chromium-molybdenum alloy steel, quenched and tempered
Grade L7M (UNS G41400) AISI 4140 / 4142 tempered for NACE MR0175 sour-service hardness limits
Grade L43 (UNS G43400) AISI 4340 Ni-Cr-Mo alloy steel for deep hardenability
Grade L7A (UNS G40370) AISI 4037 alloy steel
Grade L7B (UNS G41370) AISI 4137 chromium-molybdenum alloy steel
Grade L7C (UNS G87400) AISI 8740 Ni-Cr-Mo alloy steel
Grades L70 / L71 / L72 / L73 ASME Section II Part A equivalents of L7 / L7A / L7B / L7C
Grade L1 low-carbon controlled-composition alloy steel
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

Per-grade PDF datasheets

In addition to the full standard document above, per-grade PDF datasheets are available for direct download: