ASTM A194/A194M-24 PDF

Full title and description

Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both — designation ASTM A194/A194M-24. The specification defines material, mechanical, dimensional, and testing requirements for a wide range of heavy hex and high-strength nuts intended to be used with bolting materials specified in ASTM A193 and similar high-pressure/high-temperature applications.

Abstract

ASTM A194/A194M-24 covers carbon, alloy, martensitic, and austenitic stainless steel nuts in imperial sizes from 1/4 in. through 4 in. and metric sizes from approximately M6 (or M12 in some listings) through M100 nominal. The standard specifies allowable compositions, heat treatment, mechanical properties, hardness limits, proof-load and cone-proof tests, dimensional allowances (typically referencing heavy-hex forms per ANSI/ASME practices), marking, and optional supplementary requirements (for example S1). It is intended for nuts used in high-pressure or high-temperature service where reliable mechanical performance is required.

General information

• Status: Active / Current specification (latest designation -24).
• Publication date: May 1, 2024.
• Publisher: ASTM International (formerly American Society for Testing and Materials).
• ICS / categories: 21.060.20 (Nuts) — fasteners and mechanical joining components.
• Edition / version: ASTM A194/A194M-24.
• Number of pages: 12 pages (published PDF).

Scope

This specification applies to a variety of carbon, alloy, and stainless steel nuts intended for high-pressure or high-temperature service — including heavy-hex and related nut forms in both inch-pound and SI (“M”) designations. It limits manufacturing methods (hot-wrought bar, with possible further processing), requires conformance to specified chemical and mechanical property limits, and provides optional supplementary requirements that apply only when ordered. The standard also clarifies thread fit and dimensional practice (e.g., ANSI/ASME heavy-hex series and UNC/8UN thread fits by nominal size) and prohibits grade substitutions without purchaser approval.

Key topics and requirements

• Defined grades and materials: multiple carbon, alloy, martensitic and austenitic stainless grades (e.g., common commercial grades such as 2, 2H, 2HM, 3, 4, 6, 7, 7M, 8, 8M, 8T, 16 and others as specified by the table of grades).
• Size ranges: imperial (1/4 in. to 4 in.) and metric (M6–M100 nominal, with some editions listing M12 as lower metric range for certain alloys).
• Mechanical property requirements: minimum tensile and proof loads, hardness limits, and where applicable impact or elevated-temperature requirements.
• Mandatory tests: hardness testing, proof-load testing and cone-proof (where specified), chemical analysis, and visual/dimensional inspection; options for 100% hardness testing for certain “M” variants (e.g., 2HM, 7M) and other supplementary tests when ordered.
• Dimensional and thread fit guidance: reference to heavy-hex form and UN/UNC or 8UN thread fits by nominal size (ANSI/ASME practices typically applied unless otherwise specified).
• Supplementary requirements and marking: optional supplementary requirements (S1, etc.), manufacturer identification and heat/lot marking and traceability provisions.
• Compatibility: intended to be used with bolting materials specified in ASTM A193 (and related piping/pressure equipment bolting standards).

Typical use and users

ASTM A194/A194M nuts are used widely in oil & gas, petrochemical, power generation, pressure-vessel and piping systems, valves, flanges and other high-pressure/high-temperature assemblies. Typical users include fastener manufacturers and distributors, plant engineering and procurement teams, pressure-vessel fabricators, inspection authorities, and maintenance organizations responsible for safety-critical bolted joints.

Related standards

Commonly referenced and complementary standards include ASTM A193 (bolting materials for high-temperature/high-pressure service), ASTM A563 (general requirements for carbon and alloy steel nuts), ANSI/ASME B18.2.2 (heavy hex nut dimensional series), ISO 898-2 (mechanical properties of nuts — metric series), and various coating/finish standards used for corrosion protection. These documents are typically used together to specify complete bolting assemblies that meet mechanical, dimensional and environmental requirements.

Keywords

ASTM A194, A194M, heavy hex nuts, high-pressure bolting, high-temperature bolting, fasteners, ASTM A193, proof load, cone proof, hardness test, nut grades, bolting standards.

FAQ

Q: What is this standard?

A: ASTM A194/A194M-24 is the ASTM International standard specification that sets material, mechanical, dimensional and testing requirements for carbon, alloy and stainless steel nuts intended for high-pressure and/or high-temperature service.

Q: What does it cover?

A: It covers grades, size ranges (imperial and metric), required tests (hardness, proof-load, cone-proof as applicable), chemical and mechanical property limits, dimensional and thread-fit guidance (heavy-hex form and UNC/8UN fits by nominal size unless otherwise specified), marking and optional supplementary requirements.

Q: Who typically uses it?

A: Fastener manufacturers, distributors, plant procurement and engineering, pressure-vessel and piping fabricators, inspection and quality teams, and operations/maintenance groups in industries such as oil & gas, petrochemical, power generation and general heavy industry.

Q: Is it current or superseded?

A: The -24 designation (ASTM A194/A194M-24) is the current active edition published in 2024. Users should confirm they are working to the latest revision and check for any Amendments or Work Items if planning procurement or design.

Q: Is it part of a series?

A: It is commonly paired with related bolting and fastener specifications (notably ASTM A193 for bolts and studs, ASTM A563 for general nut requirements, and ASME/ANSI dimensional standards like B18.2.2). These standards are used together to fully specify bolted joints for pressure and temperature service.

Q: What are the key keywords?

A: Heavy hex nut, high-pressure, high-temperature, proof load, cone proof, hardness, ASTM A193, nut grades (2H, 2HM, 7, 7M, 8, etc.), ANSI B18.2.2.