ASTM A276/A276M-06a Stainless Steel Bars: Grades, Properties and Tolerances
May 29, 2025
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What ASTM A276/A276M-06a Covers
ASTM A276/A276M-06a is the ASTM International specification for hot-finished or cold-finished stainless steel bars, other than those intended for reforging. It covers round, square, hexagonal and flat bars produced from austenitic, martensitic and ferritic stainless steels, and it is the specification most often quoted when a machined part, fastener stock or general engineering component is ordered in stainless steel.
The A276 designation uses inch-pound units; A276M is the metric version of the same specification. The suffix 06a identifies the 2006 revision, which incorporated minor editorial and technical updates to the earlier 2006 edition. Reinforcing bar, rebar and wire are outside the scope of A276 and are governed by separate ASTM specifications.
Grades and UNS Designations
The specification spans three metallurgical families, and the family determines magnetic response, hardenability and weldability.
| Grade | UNS | Family | Typical use of bar stock |
|---|---|---|---|
| 304 | S30400 | Austenitic | General corrosion-resistant machined parts |
| 304L | S30403 | Austenitic | Welded assemblies, low-carbon duty |
| 316 | S31600 | Austenitic | Chemical, marine and food equipment parts |
| 316L | S31603 | Austenitic | Pharmaceutical, chloride-bearing service |
| 410 | S41000 | Martensitic | Hardenable shafts, valve trim, cutlery |
| 430 | S43000 | Ferritic | Decorative and mildly corrosive duty |
| 446 | S44600 | Ferritic | High-temperature oxidation resistance |
Mechanical Properties and Composition of Type 316L
Type 316L is the workhorse grade for corrosion-resistant bar stock. The table below lists the annealed minimum requirements applied to A276 bar.
| Property | Requirement |
|---|---|
| Tensile strength | 485 MPa (70 ksi) min |
| Yield strength, 0.2% offset | 170 MPa (25 ksi) min |
| Elongation in 50 mm (2 in.) | 30% min |
| Hardness | 217 HBW max |
| Element | Composition, % |
|---|---|
| Carbon (C) | 0.030 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.030 max |
| Chromium (Cr) | 16.0-18.0 |
| Nickel (Ni) | 10.0-14.0 |
| Molybdenum (Mo) | 2.00-3.00 |
Bar Forms, Dimensions and Tolerances
Round bar: commonly supplied from 1/8 in. to 12 in. in diameter.
Flat bar: typically up to 12 in. in width and 3 in. in thickness.
Square and hexagon bar: produced in the sizes needed for fasteners, valve stems and machined fittings.
Tolerances: dimensional limits, straightness, length and surface condition follow ASTM A484/A484M, the general requirements specification that accompanies A276.
Condition also matters: hot-finished bar is economical and well suited to heavy machining, while cold-finished bar gives a smoother surface, tighter dimensional tolerance and better consistency for automatic screw machines and precision components.
A276 Compared with A479
| Item | ASTM A276 | ASTM A479 |
|---|---|---|
| Typical application | Structural and machining bars | Pressure vessels and pressure piping |
| Heat treatment | Optional unless specified | Mandatory for most grades |
| Product form | Hot- or cold-finished bars | Bars and shapes for code applications |
Where a component falls under ASME pressure vessel or pressure piping rules, A479 is the appropriate specification because heat treatment and testing are mandatory. For general structural, fastener and machining work, A276 is the usual and more economical choice.
Duplex and Other Bar Grades
Duplex stainless bar such as UNS S31803 and its closely related UNS S32205 grade is also available under ASTM A276. The duplex microstructure delivers roughly twice the yield strength of 316L together with markedly better chloride stress corrosion resistance. The European designation for this family is EN 1.4462, and the material is specified by that number or by the UNS code rather than by mill trade names, which keeps drawings and purchase orders unambiguous.
Frequently Asked Questions
Q: Is ASTM A276 material magnetic?
It depends on the family. Martensitic grades such as 410 and ferritic grades such as 430 are magnetic. Austenitic grades such as 304 and 316 are essentially non-magnetic in the annealed condition, though cold working can make them weakly magnetic.
Q: Can ASTM A276 bar be used for pressure vessels?
Not as the primary specification. Pressure vessel and ASME code work calls for ASTM A479 bar, where heat treatment and testing requirements are mandatory.
Q: What is the difference between hot-finished and cold-finished A276 bar?
Cold-finished bar has a better surface finish and tighter tolerances, which suits precision machining. Hot-finished bar is more economical and adequate for heavy-load machining and structural parts.
Q: Does A276 cover stainless steel wire or rebar?
No. Wire and reinforcing bar are excluded and are covered by their own ASTM specifications.
Q: Does A276 apply to re-forging stock?
No. Bars intended for reforging are excluded from A276 and are ordered to the applicable forging stock specification.
Q: Which specification controls A276 bar tolerances?
ASTM A484/A484M. It sets the dimensional, straightness, length and surface acceptance limits that A276 bar is inspected against.
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