ASTM A479 Stainless Steel Bar for Boilers and Pressure Vessels

What ASTM A479 Covers

ASTM A479 governs wrought stainless steel bar and shapes intended for pressurized construction. It is the specification a vessel fabricator calls out when round bar, flats, or hex are used as internals, trays, baffles, support lugs, tube sheets, studs, or machined components inside equipment built to a construction code such as the ASME Boiler and Pressure Vessel Code. The specification fixes composition limits, minimum mechanical properties in the supplied condition, required heat treatment, and the tests a mill performs before certifying a heat.

What separates A479 from the general-purpose bar standard is intent. Both describe the same base alloys, but A479 adds the mechanical qualification and documentation discipline that code work demands, so the material can be used with confidence in a load-bearing, pressure-retaining assembly.

A479 and ASME SA-479

When a vessel is built to the ASME Boiler and Pressure Vessel Code, the material is usually ordered to the ASME edition, SA-479. SA-479 mirrors ASTM A479 in chemistry and mechanical requirements; the ASME designation signals that the heat is acceptable for code construction. On the purchase order and the mill test certificate, stating the exact edition you need avoids receiving-inspection disputes later.

A479 Within the Round-Bar Range

Every A479 grade is held ex-stock as finished stainless steel round bar, part of our broader round-bar program. Bar is cut and dispatched immediately, and every order ships with an EN 10204 3.1 (or 3.2 on request) mill test certificate confirming the heat against the specification.

A479 vs A276: Which Bar Specification to Order

Buyers often ask which stainless bar spec belongs on the PO. The difference is not the alloy, it is the service and the paperwork.

For general machined parts and non-pressure fabrication, the companion ASTM A276 stainless steel bar standard applies the same chemistry without the construction-code overlay.

Grades Supplied to ASTM A479

Austenitic grades carry most A479 bar work. The table lists the grades we stock to A479 with their UNS numbers and the attribute that drives selection.

Chemistry That Drives Bar Selection

A479 fixes the composition window for each grade. The elements below decide which bar belongs in the vessel.

The molybdenum content is what separates 316 from 304 on pitting resistance, and the copper-bearing, high-molybdenum chemistry of 904L super-austenitic stainless is what lets it resist sulfuric acid where 316 cannot. For the method behind these numbers, see the PREN and pitting resistance guide.

Mechanical Properties and Heat Treatment

A479 lists mechanical property minimums for each grade in the condition supplied, and austenitic bar is furnished solution-annealed. Solution annealing, a hold at high temperature followed by rapid cooling, dissolves chromium carbides and locks the alloy in its most corrosion-resistant state, which is exactly why a pressure vessel wants it. Typical annealed austenitic minimums are a tensile strength around 515 MPa (75 ksi), yield (0.2% offset) around 205 MPa (30 ksi), and elongation near 40%, with hardness capped by grade.

Where bar is welded and then held in the 425–815 °C range, specify an L grade (C ≤ 0.03%) to avoid sensitization and the intergranular attack that follows, or choose a stabilized grade such as 321 or 347. The guide to preventing sensitization, the solution annealing explainer, and the intergranular corrosion explainer cover why low-carbon and stabilized grades matter in welded code assemblies.

How to Choose the Right A479 Grade

Grade selection for vessel bar follows the same logic as for plate: match the alloy to the real service environment inside the vessel, not to habit.

• General and non-chloride service: 304 or 304L bar handles most vessel internals. See pressure vessels and boilers applications.
• Chloride, marine, and coastal exposure: step up to 316 or 316L for the molybdenum. Compare the families in 304 vs 316 and 304L vs 316L.
• Hot concentrated chlorides or sulfuric acid: move to 904L before reaching for more expensive alloys.
• Elevated temperature: 321, 347, or 310S hold up where plain 304 would scale or sensitize.

A common and costly error is defaulting to 304 for chloride-adjacent duty, where it pits. Confirm the actual service chlorides before choosing 304 over 316, since stepping up is far cheaper than a failed component. Our stainless grade selection guide and grade selector tool walk through the decision, and the pressure-vessel steel explainer sets the bar grade in the context of the whole vessel.

Related Standards and Forms

A479 governs stainless bar for pressurized construction; neighboring specifications cover the same alloys in other forms and services within a vessel build.

For nickel-alloy long products outside the stainless range, bar is supplied to the relevant ASTM B-series specification rather than A479.

Quality, Testing, and Traceability

Every bar order is backed by an EN 10204 3.1 or 3.2 mill test certificate, confirming chemistry and mechanical properties against the A479 limits for the supplied heat. Material comes from genuine mill sources, and third-party inspection by TÜV SÜD, Bureau Veritas, DNV, SGS, or ABS can be arranged. Nandini Steel has been an ISO 9001:2015-certified stockist and supplier since 2003, with full material traceability from heat to dispatch.

Frequently Asked Questions

Request a Quote

Need A479 stainless bar for a vessel or boiler, cut to size? Contact Nandini Steel for live pricing and ex-stock availability. Call +91 22 43404600, WhatsApp +91 99202 09184, email reachus@nandinisteel.com, or send an RFQ through our contact page.