ASTM Specifications for Stainless Steel Bar: A276, A479, A484 and A564

An ASTM stainless steel bar specification is a standard published by ASTM International that fixes the composition, condition, mechanical properties and general requirements to which stainless steel bar is made and supplied. Four specifications cover most stainless bar in the ASTM system. ASTM A276 covers bars and shapes without reference to a particular service. ASTM A479 covers bars and shapes for boilers and other pressure vessels, and the American Society of Mechanical Engineers adopts it as SA-479. ASTM A484 holds the general requirements, among them the permitted variations in size and straightness, that the product specifications share. ASTM A564 covers the age-hardening grades such as 17-4 PH. Two further specifications sit beside them: A582 for the free-machining grades and A314 for billets and bars intended for forging. A grade designation such as 316L or S31603 fixes the composition only; the specification fixes the product. This article sets out the scope of each specification, the differences between A276 and A479, and the European counterparts of the common bar grades.

The ASTM stainless bar specifications

Each ASTM bar specification is a product specification: it names the product forms it covers, the grades by UNS number, the conditions in which the bar is supplied, and the tests that prove it. Each also cites ASTM A484 for the requirements that every bar specification shares, so that a bar ordered to any one of them inherits the same rules on dimensions, straightness, analysis tolerances and marking.

ASTM A276: stainless steel bars and shapes

ASTM A276/A276M covers hot-finished and cold-finished stainless steel bars, except bars for reforging. The forms are rounds, squares and hexagons, together with hot-rolled or extruded shapes such as angles, tees and channels, in the more commonly used stainless steel types. Two groups are excluded by name: bars for reforging, which fall under A314, and free-machining bars designed for optimum machinability, which fall under A582. The grades are designated by UNS number, with the AISI type number kept as the common name, so 304 appears as S30400 and 316L as S31603.

A276 defines five conditions by letter. Condition A is annealed. Condition H is hardened and tempered at a relatively low temperature, and Condition T is hardened and tempered at a relatively high temperature; these two apply to the hardenable martensitic grades. Condition S is strain hardened by relatively light cold work, and Condition B by relatively severe cold work. The specification requires the tensile strength, yield strength, elongation and Brinell hardness to be determined, and sets the required values by grade, condition and finish. For 304 bar, hot finished in Condition A, the minima are 205 MPa yield strength, 515 MPa tensile strength and 40 percent elongation. The minima for the other common bar grades are tabulated in the yield strength and tensile strength article.

A276 states its values in inch-pound units and in SI units. The two systems are not exact equivalents and are used independently: a bar is furnished to the inch-pound values unless the "M" designation, A276M, is specified. The same rule applies to A479 and A484.

ASTM A479 and ASME SA-479: bars for pressure vessels

ASTM A479/A479M, Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels, covers the same product forms as A276: hot-finished and cold-finished rounds, squares and hexagons, and hot-rolled or extruded angles, tees and channels. Its purpose is narrower. A479 bar is made for boiler and pressure vessel construction, and the specification lists austenitic, austenitic-ferritic (duplex), ferritic and martensitic grades for that service. The American Society of Mechanical Engineers adopts it into Section II, Part A of the Boiler and Pressure Vessel Code as SA-479/SA-479M, and a pressure part designed to that code calls for SA-479 bar.

The requirements follow from the service. The tensile strength, yield strength, elongation and hardness are determined for every grade in its specified heat treatment condition. The austenitic grades are supplied heat treated and carry a corrosion test requirement, because a pressure part is commonly welded and then exposed to a process fluid. The higher-carbon H grades, such as 304H, 321H and 347H, are listed for service at elevated temperature. A479 also defines a strain-hardened 316 for parts that need more strength than the annealed grade gives: the bar is solution annealed and then cold worked to one of two levels, Level 1 and Level 2, each with its own minimum properties. The duplex grades UNS S31803 and S32205 are bar grades of A479 as well.

A276 against A479

The two specifications cover the same forms in many of the same grades, and both take their general requirements from A484. They differ in the service each is written for and in what follows from that service.

A heat that meets the requirements of both specifications can be supplied to both at once. The choice between them follows the design code of the finished part. A pressure part built to the ASME code calls for A479 or SA-479. A part outside a pressure code, such as a shaft or a general machined component, can be specified to A276, or to the equivalent grade under EN 10088-3 where the design is European.

ASTM A484: general requirements

ASTM A484/A484M, Standard Specification for General Requirements for Stainless Steel Bars, Billets, Shapes, and Forgings, is not a product specification. It holds the requirements common to eleven product specifications: A276, A314, A458, A477, A479, A564, A565, A582, A638, A705 and A831. Each of these cites A484, and bar supplied to any of them inherits its clauses. Flat-rolled products other than bar fall under ASTM A480 instead, and coiled wire under ASTM A555.

The clauses of A484 cover the conditions in which material is furnished (hot worked, annealed, cold worked or heat treated), the tolerances on product analysis, the permitted variations in diameter, out-of-round, straightness, length and weight, and the methods of test and marking. The standard also sets an order of precedence. Where a product specification and A484 conflict, the product specification governs. A more stringent requirement in the purchase order governs both, provided it does not set aside a requirement of either, for example by waiving a test.

The dimensional tables of A484 are the tolerance basis for hot rolled stainless bar in the ASTM system. They state a plus-and-minus allowance about the nominal size that widens with the size, which is a different system from the ISO 286 classes used for bright bar. The two are compared, with the deviations in millimetres, in the tolerance classes article.

ASTM A564 and A314

ASTM A564/A564M covers hot-rolled and cold-finished age-hardening stainless steel bars and shapes: rounds, squares, hexagons, bar shapes, angles, tees and channels. Its grades are the precipitation hardening stainless steels, among them Type 630 (UNS S17400, known as 17-4 PH), Types 631 and 632, XM-16 and XM-25. Type 630, XM-16 and XM-25 may be supplied solution annealed or age hardened. Each age-hardened condition is named by its ageing temperature in degrees Fahrenheit, from H900 to H1150, and carries its own minimum strength and hardness. The condition table for 17-4 PH is printed on the precipitation hardening steels page.

Free-machining bar, the resulphurised grades that A276 excludes, is specified to ASTM A582/A582M, set out in the article on free-machining stainless steel.

ASTM A314 covers stainless steel billets and bars intended only for forging. The material is supplied annealed, with its surface conditioned by chipping or grinding, and the specification sets the chemical composition of each grade. The properties of the finished part are set by the forging specification, such as ASTM A473 for stainless steel forgings.

ASTM bar grades and their EN 10088-3 counterparts

Outside North America the same bar is specified to EN 10088-3, which identifies a grade by an EN material number and a steel name in place of a UNS number. The table pairs the common ASTM bar grades with the nearest EN 10088-3 grade. A pair is a nearest counterpart and not an identity. The composition windows differ in small ways: 304 requires 18.0 to 20.0 percent chromium under ASTM A276 and 1.4301 requires 17.5 to 19.5 percent under EN 10088-3, so a heat at 17.5 percent chromium meets one and not the other. The European standard, its condition symbols and its finish codes are set out in the article on EN 10088-3 and EN 10278, and further pairings are listed in the equivalents tables.

ASTM bar from Laxcon Steels

Laxcon Steels melts, rolls and finishes stainless steel bar at Sanand, Gujarat. Its hot rolled round bar, from 16 to 125 mm, names ASTM A276, A479, A484 and A314 among its governing standards, and its bright bar, from 5 to 115 mm, names A276, A479 and A484. Precipitation hardening bar is supplied to ASTM A564. TUV India has qualified Laxcon Steels as a manufacturer of special materials to NORSOK M-650 for hot rolled bars in ASTM A479 grade 316 and in the duplex grades UNS S32205 and S31803. The Central Boilers Board recognises the plant as a Well Known Steel Maker under the Indian Boiler Regulations 1950 for boiler quality ingots, billets, blooms, rolled bars and rounds. Mechanical testing is carried out in the plant's NABL-accredited laboratory, described on the quality page.

Frequently asked questions

What is the difference between ASTM A276 and A479?

ASTM A276 covers stainless steel bars and shapes without naming a service. ASTM A479 covers the same forms for boilers and other pressure vessels, adds a corrosion test requirement and a specified heat treatment for the austenitic grades, defines a strain-hardened 316, and is adopted by ASME as SA-479. A pressure part built to the ASME code calls for A479.

Is ASME SA-479 the same as ASTM A479?

SA-479 is ASTM A479 adopted into Section II, Part A of the ASME Boiler and Pressure Vessel Code. ASME adopts the ASTM text, in some cases with stated additions, and the SA designation is the one a code pressure part calls for. A bar that meets both can be supplied to both designations.

What does ASTM A484 cover?

ASTM A484 is the general requirements specification for stainless steel bars, billets, shapes and forgings. It sets the permitted variations in size, out-of-round, straightness, length and weight, the product analysis tolerances, and the test and marking requirements shared by A276, A479, A564, A582, A314 and six other product specifications.

Which ASTM specification covers 17-4 PH bar?

ASTM A564 covers 17-4 PH bar as Type 630, UNS S17400. The bar is supplied solution annealed or age hardened to a condition from H900 to H1150, each with its own minimum strength and hardness.

What is the European equivalent of ASTM A276?

EN 10088-3 is the European standard for stainless steel bar for general purposes. It sets composition, condition and mechanical properties as A276 does, while the dimensions and tolerances come from separate standards such as EN 10060 for hot rolled round bar and EN 10278 for bright bar.

Sources

• ASTM A276/A276M-25, Standard Specification for Stainless Steel Bars and Shapes.
• ASTM A479/A479M-26, Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels.
• ASME Boiler and Pressure Vessel Code, Section II, Part A, SA-479/SA-479M.
• ASTM A484/A484M-24b, Standard Specification for General Requirements for Stainless Steel Bars, Billets, Shapes, and Forgings.
• ASTM A564/A564M-25, Standard Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes.
• ASTM A582/A582M, Standard Specification for Free-Machining Stainless Steel Bars.
• ASTM A314-25, Standard Specification for Stainless Steel Billets and Bars for Forging.
• EN 10088-3:2023, Stainless steels, Part 3: technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion resisting steels for general purposes.