SS 321 FastenersASTM A193 B8T · Manufacturer, stockist & exporter, India
Also sold as AISI 321 · UNS S32100 · W.Nr 1.4541 · Titanium-stabilised stainless
SS 321 fasteners — stud bolts, hex bolts, nuts and washers — are made from ASTM A193 B8T bar stock to ASME B18 dimensions. It is a titanium-stabilised austenitic stainless steel, chosen for high-temperature service between 425 and 815 °C. Kanak Steel & Engineering Co. supplies it with EN 10204 3.1 mill certificates from Mumbai to buyers across India, the Gulf, South-East Asia, South America, Europe, the UK and the USA.
- Stock & mill supply
- EN 10204 3.1 / 3.2
- PMI on every heat
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is SS 321 Fasteners?
SS 321 fasteners is a titanium-stabilised austenitic stainless steel supplied as fasteners to ASTM A193 B8T (UNS S32100). Buyers specify it for high-temperature service between 425 and 815 °C. It is also sold as AISI 321, UNS S32100, W.Nr 1.4541.
- What it is
- Titanium-stabilised austenitic stainless steel
- Bar stock
- ASTM A193 B8T
- Dimensions
- ASME B18.2.1 · B18.2.2 · B18.31.2
- Threads
- UNC · UN-8 · metric
- Sizes
- M10 – M64 · ½" – 4"
- Best at
- High-temperature service between 425 and 815 °C
SS 321 Fasteners Specification & Sizes
| Material | ASTM A193 B8T |
|---|---|
| Dimensional standards | ASME B18.2.1 (bolts) · B18.2.2 (nuts) · B18.31.2 (studs) · DIN 931 / 933 / 934 |
| Types | Stud bolt · Hex bolt · Heavy hex nut · Hex nut · Washer · Threaded rod · U-bolt · Eye bolt · Anchor bolt · Foundation bolt · Socket head cap screw · Machine screw |
| Threads | UNC, UN-8 and metric coarse |
| Coating | Plain · PTFE on request |
| Documents | EN 10204 3.1 |
SS 321 Stud Bolts: Grade & Nut Pairing
Pressure bolting in this material is ASTM A193 B8T studs with ASTM A194 8T heavy hex nuts. A193 B8-series bolting comes in Class 1 (carbide solution treated) and Class 2 (strain hardened, higher strength) — state the class.
Torque (T = K × F × d), stud length and coatings are covered in the fasteners guide.
| Galling | Stainless and nickel-alloy threads gall — always use anti-seize, and avoid high-speed tightening |
|---|---|
| Coatings | Usually supplied plain; PTFE coating on request to ease tightening |
| Marking | Grade symbol and maker's mark on each stud end and nut, as the standard requires |
| Certificates | EN 10204 3.1 for the bar heat; mechanical test reports on the finished bolts on request |
SS 321 Fasteners Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 17.0 – 19.0 |
| Nickel | 9.0 – 12.0 |
| Titanium | 5 × (C + N) min, 0.70 max |
| Carbon | 0.08 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Nitrogen | 0.10 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
| Iron | Balance |
SS 321 Fasteners Mechanical Properties
| Annealed plate & sheet | Value |
|---|---|
| Tensile strength | 515 MPa · 75 ksi |
| Yield strength 0.2% | 205 MPa · 30 ksi |
| Elongation | 40% |
| Hardness | 217 HB max |
Density & Physical Properties
| Property | Value |
|---|---|
| Density | 7.92 g/cm³ |
| Melting range | 1400 – 1425 °C |
| Magnetic | Non-magnetic annealed |
| PREN (approx.) | ≈ 18 |
SS 321 Equivalent Grades
Values follow ASTM A240 for UNS S32100. Always check against the edition named on your purchase order.
Six-digit Harmonized System heading (iron and steel, chapter 72–73). Your country adds its own digits — confirm with your customs broker. All HS codes.
How to Verify SS 321 Fasteners with PMI
Positive material identification with a handheld XRF gun confirms the alloy on the piece itself, in seconds, before it is cut or welded. SS 321 is most often mixed up with SS 347 — the table shows which elements tell them apart.
Handheld XRF does not measure carbon or nitrogen; those come from the mill certificate or optical emission (OES) testing. We PMI-test nickel alloys as standard and any grade on request.
| Element | SS 321 | SS 347 |
|---|---|---|
| Nickel | 9.0 – 12.0 | 9.0 – 13.0 |
| Chromium | 17.0 – 19.0 | 17.0 – 19.0 |
| Titanium | 5 × (C + N) min, 0.70 max | residual |
| Niobium | residual | 10 × C min, 1.00 max |
| Iron | Balance | Balance |
| Manganese | 2.00 max | 2.00 max |
SS 321 fasteners by type
SS 321 Fasteners Applications
SS 321 is specified when the cheaper grade will not survive the service but a higher alloy would be more than the job needs. These are the jobs our buyers use it for.
SS 321 Fasteners vs 304, 347 and 310S
| Grade | Fasteners standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 304 | ASTM A193 B8 · A194 8 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 347 | ASTM A193 B8C | ≈ 18 | Welded high-temperature piping in refineries and power plants |
| SS 321 | ASTM A193 B8T | ≈ 18 | High-temperature service between 425 and 815 °C |
| SS 310 / 310S | ASTM A276 / A479 | ≈ 25 | Furnaces, burners and heat treatment at high temperature |
PREN = Cr + 3.3 Mo + 16 N, from mid-range chemistry. A screening guide, not a substitute for corrosion data on your medium.
SS 321 Corrosion Resistance — Element by Element
Each alloying addition has a job. Knowing which one protects against your medium is the quickest way to judge whether 321 fits.
About 18% chromium forms the passive film that makes the steel stainless.
Nickel keeps the structure austenitic — tough at low temperature and easy to form and weld.
Titanium ties up carbon, so 321 keeps its corrosion resistance after long service in the sensitising range.
321H with higher carbon is used above about 540 °C for better creep strength.
How your 321 fasteners order runs
- 01Enquiry review — we confirm size, standard edition and documents against your MR or drawing.
- 02Heat selection & PMI — the mill certificate is checked and material is PMI-tested before processing.
- 03Processing — cutting, machining or bevelling to your specification, with heat numbers marked.
- 04Inspection — your third-party inspector witnesses, or we share photos and test reports.
- 05Packing & dispatch — seaworthy packing from Nhava Sheva (JNPT), Mumbai, FOB or CIF, documents sent before the vessel sails.
Welding & Fabricating SS 321 Fasteners
SS 321 welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER347 (AWS A5.9) |
|---|---|
| Over-alloyed filler | ER321 is rare; ER347 is the usual filler |
| Preheat | Not required; keep interpass temperature low |
| Cutting | Thermal or abrasive cutting; grind off heat-tinted edges before welding |
Follow your approved WPS; this is general guidance. See also 321 fittings and 321 flanges for the matching pipe-system parts.
How to Order SS 321 Fasteners: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Fastener type, size and length
- Thread form
- Material and marking
- Quantity in sets
- Certificate type
- Delivery port and date
SS 321 fasteners for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 321 fasteners — questions buyers ask
Is SS 321 the same as AISI 321?
Yes. AISI 321, UNS S32100, W.Nr 1.4541 all refer to the same material, and fasteners is ordered to ASTM A193 B8T whichever name is on the enquiry.
Why use SS 321 bolts instead of B7 carbon steel?
On SS 321 flanges in corrosive service, carbon-steel bolts corrode first. Matching-alloy bolting avoids galvanic corrosion and bolt failure.
What nut goes with SS 321 stud bolts?
ASTM A194 8T heavy hex nuts.
How do I stop SS 321 bolts galling?
Use an anti-seize compound on threads and nut faces, tighten at moderate speed, and do not reuse galled nuts.
SS 321 or SS 310 / 310S — which should I choose?
SS 321 is chosen for high-temperature service between 425 and 815 °C. SS 310 / 310S is the step up when you need more pitting resistance or strength. See the comparison table on this page, or ask us with your process conditions.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026