SS 321 Square TubeASTM A554 · Manufacturer, trader & exporter, India
AISI 321 · UNS S32100
An SS 321 square tube is square hollow section, made from SS 321 to ASTM A554 (ornamental) · A312 / A790 for pressure. Square tube is used for frames, handrails, architecture and structures.
- ASTM A554
- ASTM A554 / EN 10219
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 321 Square Tube?
- What it is
- Square hollow section
- Material
- ASTM A554 (ornamental) · A312 / A790 for pressure
- Dimensions
- ASTM A554 / EN 10219
- Grade
- SS 321 · UNS S32100
- Best at
- High-temperature service between 425 and 815 °C
SS 321 Square Tube Specification
| Product | SS 321 Square Tube |
|---|---|
| Material standard | ASTM A554 (ornamental) · A312 / A790 for pressure |
| Dimensional standard | ASTM A554 / EN 10219 |
| Sizes | OD × wall to order |
| Length | Random, double random or cut lengths |
| Testing | PMI (as specified in the PO) · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 or 3.2 on request / as specified in the PO |
When to Choose a Square Tube
Square tube is used for frames, handrails, architecture and structures.
- Square hollow section
- Polished or mill finish
- Cut lengths
More on choosing: Square tube guide.
SS 321 Square Tube: Why 321 for square tubes
Square tube is used for frames, handrails, architecture and structures. In SS 321, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless tubulars are the default for corrosive and hygienic service. SS 321 is picked for high-temperature service between 425 and 815 °C. |
|---|---|
| Typical service | Aircraft exhaust — Manifolds, bellows and exhaust systems. |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER347 (AWS A5.9) |
SS 321 Square Tube Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Titanium | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Nitrogen | As specified |
| Phosphorus | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S32100.
SS 321 Square Tube Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S32100 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 321 grade page.
Standards on this page
Other SS 321 pipes & tubes
SS 321 Square Tube — questions buyers ask
What finishes are available on square tube?
Mill finish, 180–320 grit polish and hairline, depending on grade.
Can SS 321 square tubes be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
Which standard covers SS 321 square tubes?
The material is ASTM A554 (ornamental) · A312 / A790 for pressure; dimensions follow ASTM A554 / EN 10219. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 321 square tube?
The alloy price, the size and dimensions, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 or 3.2 certificates available on request / as specified in the PO; dimensional reports as required. PMI can be arranged depending on product and requirements, as specified in the PO.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026