ASTM A320/A320M-24a PDF

Full title and description

ASTM A320/A320M-24a — Standard Specification for Alloy‑Steel and Stainless Steel Bolting for Low‑Temperature Service. This specification defines chemical, mechanical, and impact requirements for bolting materials and bolting components intended for use in low‑temperature pressure‑containing equipment (vessels, valves, flanges, fittings) and includes grades and classes for both ferritic and austenitic steels.

Abstract

This standard specifies composition, heat treatment, tensile and hardness requirements, and impact‑energy (Charpy) criteria for alloy‑steel and stainless‑steel bars, bolts, studs, and nuts intended for low‑temperature service. It covers multiple material grades and classes, optional supplementary requirements, and both inch‑pound and SI units (M designation). Mechanical and impact testing requirements and recommended test temperatures are included to ensure low‑temperature toughness.

General information

• Status: Active / current specification (latest revision published in 2024; maintained by ASTM Committee A01.22).
• Publication date: 2024 (designation A320/A320M‑24a; published/updated in October 2024).
• Publisher: ASTM International (ASTM).
• ICS / categories: 21.060.01 (Fasteners in general); 77.080.20 (Steels).
• Edition / version: A320/A320M‑24a (DOI: 10.1520/A0320_A0320M‑24 as published by ASTM).
• Number of pages: 8 pages.

Scope

The specification covers alloy and stainless steel bolting materials and bolting components for pressure vessels, valves, flanges, and fittings intended for low‑temperature service. It includes hot‑wrought bars (which may be centerless‑ground or cold‑drawn), solution‑annealed or strain‑hardened austenitic stainless steels, and several designated grades (for example L7, B8, etc.). The standard sets tensile, yield, elongation, hardness, and Charpy impact requirements and specifies required test temperatures and applicable supplementary requirements when ordered. See referenced Specification A962/A962M for the definition of bolting.

Key topics and requirements

• Designation and classification of bolting grades and classes for low‑temperature service (ferritic and austenitic grades such as L7 and B8).
• Chemical composition limits and permitted additional elements for each grade.
• Mechanical property minimums: tensile strength, yield strength, elongation and maximum/minimum hardness values tied to diameter ranges.
• Impact (Charpy) energy requirements and specified test temperatures to demonstrate low‑temperature toughness; impact testing of nuts where applicable.
• Heat‑treatment and condition requirements (solution‑treated, strain‑hardened, tempering/stress relief where applicable).
• Supplementary requirements selectable by purchaser and dual‑unit presentation (inch‑pound and SI/M version).

Typical use and users

Used by design engineers, mechanical engineers, pressure‑vessel and piping specifiers, fastener manufacturers, quality and inspection personnel, procurement departments, and standards compliance officers involved in specifying or supplying bolting for low‑temperature pressure equipment (LNG, cryogenic systems, cold‑service vessels and piping, valves and flanges).

Related standards

Commonly referenced and related documents include Specification A962/A962M (definition of bolting and general requirements), ASTM test standards for mechanical and impact testing (for example A370, E23, E18) and other ASTM bolting/fastener specifications. The standard is developed by ASTM Committee A01 (Subcommittee A01.22).

Keywords

low‑temperature bolting, alloy‑steel bolting, stainless steel bolting, L7, B8, Charpy impact, tensile properties, hardness, pressure vessel bolting, fasteners, A320/A320M‑24a.

FAQ

Q: What is this standard?

A: It is an ASTM International specification (A320/A320M‑24a) that establishes chemical, mechanical, and impact requirements for alloy‑steel and stainless‑steel bolting materials intended for low‑temperature service (pressure vessels, valves, flanges, fittings).

Q: What does it cover?

A: Material grades and classes, composition limits, tensile/yield/elongation and hardness requirements, Charpy impact energy requirements at specified temperatures, heat‑treatment conditions, testing procedures, and optional supplementary requirements. Nuts for use with the bolting are also covered and required to be impact tested when specified.

Q: Who typically uses it?

A: Engineers, fastener manufacturers, inspectors, quality managers, procurement/specification writers, and anyone specifying or supplying bolting for low‑temperature or cryogenic pressure‑containing equipment.

Q: Is it current or superseded?

A: The A320/A320M‑24a edition is the active/current ASTM release from 2024; it is maintained by ASTM and may be subject to future revisions or work items by Committee A01.22. Check ASTM for the most recent maintenance or amendment history.

Q: Is it part of a series?

A: Yes — it belongs to the set of ASTM fastener/material specifications managed by Committee A01 and cross‑references other ASTM standards (for bolting definitions, mechanical testing, and related material specifications). It is presented in both inch‑pound and SI (M) formats as part of the A320/A320M designation.

Q: What are the key keywords?

A: low‑temperature bolting, alloy steel, stainless steel, Charpy, tensile, hardness, L7, B8, pressure vessel fasteners.