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This guide is for lab and facility staff who meet “ASTM A240” on an equipment datasheet, a quote or a material certificate and need to know what the designation tells them. It is general reference information, not engineering or purchasing advice.
Short answer
ASTM A240 is the ASTM International specification for chromium, chromium-nickel and chromium-manganese-nickel stainless steel in flat-rolled form: plate, sheet and strip, for pressure vessels and for general applications. On a datasheet, “ASTM A240” next to a grade such as 304 or 316 means the flat product is supplied to that specification. It does not describe tube, pipe or bar.
Definition and scope
The full title, as shown on ASTM’s store page, is “Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications.” Its scope statement says it covers chromium, chromium-nickel and chromium-manganese-nickel stainless steel plate, sheet and strip for those two uses. ASTM writes the specification as A240/A240M, the “M” designation being the SI-unit form.
Two points from the scope text are easy to miss:
- Inch-pound values and SI values are each regarded separately as standard, and the two systems are not exact equivalents of one another.
- Unless the order specifies the “M” designation, the material is furnished in inch-pound units.
ASTM’s store lists A240/A240M-26 as the active edition. Confirm the edition named on a purchase document against ASTM’s current listing; this page describes the scope and does not reproduce the standard’s requirements.
How the designation appears on a datasheet
Mill datasheets usually list several specification names in one row. ATI’s published product data for grade 304 plate and sheet, for example, lists “ASTM A240, ASTM A666, ASME SA-240” under specifications, while its grade 316 data lists “ASTM A240, ASME SA-240” for plate, sheet and strip. The “ASME SA-240” entry is a separate ASME designation shown next to the ASTM one on the same product.
Reading the row correctly means asking three things: which product form the specification covers (flat-rolled only), which grade is named next to it, and whether the order asks for inch-pound or “M” (SI) units.
Worked comparison: two common grades supplied to A240
The table below uses one manufacturer’s published values for flat products listed to A240, as shown on ATI’s product pages, checked 2026-10-30. It illustrates what a datasheet row contains; it is not the specification’s own requirement table and not a substitute for the mill certificate of the material actually delivered.
| Property (ATI published data) | Grade 304 | Grade 316 |
|---|---|---|
| Chromium, wt% | 17.5 to 19.5 | 16.0 to 18.0 |
| Nickel, wt% | 8.0 to 10.5 | 10.0 to 14.0 |
| Molybdenum, wt% | not listed | 2.00 to 3.00 |
| Carbon, wt% max | 0.07 | 0.08 |
| Tensile strength, min | 75 ksi (515 MPa) | 75 ksi (515 MPa) |
| Yield strength, min | 30 ksi (205 MPa) | 30 ksi (205 MPa) |
| Elongation, min | 40% | 40% |
| Hardness, max | 92 HRB | 95 HRB |
Two things stand out. The strength minimums are the same for both grades, so the choice between them is a composition question (the molybdenum in 316), not a strength one. And hardness is given as a maximum, not a target. For a side-by-side of the grades themselves, see the 304 vs 316 stainless steel comparison.
Related standards by product form
Because A240 covers flat-rolled stainless, other product forms are designated separately. CASRAI’s sanitary tubing guide covers the tube specifications, including ASTM A269 for tubing and how it differs from A270 and A213; see the stainless steel sanitary tubing size chart. Surface finishing after fabrication is a separate topic with its own standards, covered in the guide to passivation of stainless steel.
Where it matters for lab and equipment materials
Flat-rolled stainless is the starting material for many pieces of lab and clinical equipment: tanks, vessel bodies, panels, work surfaces and enclosures. When a specification sheet for such equipment cites A240 and a grade, it identifies the sheet or plate the item is made from. What the item is exposed to is a separate question: the chemical compatibility chart for wetted materials covers how material choice relates to the chemicals in contact with it.
A short checklist for reading a document that cites A240:
- Is the item flat-rolled (plate, sheet, strip)? If it is tube, pipe or bar, A240 is not the governing specification.
- Which grade is named, and is it the grade the equipment specification calls for?
- Does the cited edition match the edition the order requires?
- Does the document use inch-pound or “M” (SI) values, and are they being compared like for like?
- Does the document cite ASTM A240, ASME SA-240 or both, and does the order require that form?
Common misunderstandings
A240 is a tube or bar specification
It is not. A240 covers plate, sheet and strip. Tubing and other forms carry other designations.
A240 and A240M are different materials
They are the same specification expressed in two unit systems, and the scope text says the two sets of values are not exact equivalents, so values should not be mixed between them.
Hardness values are targets
In the manufacturer data above they are maximums (92 HRB for 304, 95 HRB for 316), not typical values.
Meeting A240 says how the surface was finished
A240 is a material specification for the flat product. Post-fabrication treatment such as passivation is a separate process with separate standards.
FAQ
What is ASTM A240?
The ASTM specification for chromium, chromium-nickel and chromium-manganese-nickel stainless steel plate, sheet and strip, for pressure vessels and for general applications.
Does ASTM A240 cover tube or pipe?
No. It covers flat-rolled plate, sheet and strip. Tubing is designated separately; the tubing guide linked above covers A269, A270 and A213.
What does ASME SA-240 mean?
It is the ASME designation that manufacturer datasheets list alongside ASTM A240 for the same flat products; ATI’s data for grades 304 and 316 shows both side by side on plate and sheet. The two names are separate designations, so check which one the order requires.
Are the inch-pound and SI values in A240 interchangeable?
No. Each system is regarded separately as standard and they are not exact equivalents. Material is furnished in inch-pound units unless the order specifies the “M” designation.
Sources
- ASTM International, A240/A240M scope and title as shown on its store page (A240/A240M-05a listing; A240/A240M-26 is shown as the active edition), https://store.astm.org/a0240_a0240m-05a.html, checked 2026-10-30. Consult the current standard for requirements.
- ATI, Grade 304 product data, https://atimaterials.com/Products/ati-304, checked 2026-10-30.
- ATI, Grade 316 product data, https://atimaterials.com/Products/ati-316, checked 2026-10-30.
