Ready Stock: M2 – M42 | Custom sizes up to M180
Standard: ASTM A193 / A194 · DIN 931 · UNS S32100 · 1.4541
Certification: EN 10204 3.1 MTC · Third-Party Inspection · 100% Radiography
Temperature Rating: up to 816 °C (1500 °F) | Service Life: 20–25 years
Unifit Fastener, as a special fasteners manufacturer, stockist and exporter of Stainless Steel 321 fasteners (UNS S32100 / Werkstoff 1.4541), provide reliable fasteners solution for all kinds of petrochemical, oil & gas, aerospace, power, marine projects around the world. The one element that makes a difference in Grade 321 is the presence of titanium, which ties up the carbon before it can combine with the chromium to form chromium carbides, which results in a corrosion resistant alloy even after welding or prolonged heating between 427°C and 816°C. This translates to superior corrosion, oxidation and/or high temperature scaling resistance from our SS 321 bolts, nuts, studs, screws and washers compared to standard 304 fasteners. All batches shipped are produced according to ASTM A193 / A194 and Internationally recognised DIN, ISO, BS and JIS standards and have a complete material test certificate (EN 10204 3.1). Engineers and procurement teams can source certified 321 stainless fasteners quickly and efficiently from Unifit Fastener, who has a complete range of stock options from M2 through M42, custom manufacturing options all the way to M180, and mill-direct competitive pricing, without sacrificing quality, documentation or delivery time.
Request a QuoteStainless Steel 321 fasteners are threaded fastening components — bolts, nuts, studs, screws and washers — machined or cold-formed from grade 321, a chromium-nickel austenitic stainless steel stabilised with titanium. The titanium addition (roughly five times the carbon content) prevents carbide precipitation during welding and elevated-temperature service, a phenomenon that would otherwise leave the grain boundaries vulnerable to attack. Because of this, 321 is the preferred choice wherever components are welded and then operated hot.
| Parameter | Specification |
|---|---|
| Grade / UNS | SS 321 / UNS S32100 (also S32109) |
| Werkstoff No. | 1.4541 |
| Standards | ASTM A193 / A194 · ASME SA193 · DIN · ISO · BS · JIS · IS |
| Dimension Standards | DIN 931/933/934 · ASME B18.2.1 / B18.3 · ISO 4032/4033 |
| Size Range | M2 – M42 ready stock; custom up to M180 (3/16″ to 4″) |
| Length | 3 mm – 200 mm (longer on request) |
| Thread Forms | Metric coarse/fine, UNC, UNF, BSW, BSF |
| Surface / Finish | Passivation, polished, mirror, electroplated, PTFE / hot-dip options |
| Pressure Rating | Up to PN16 |
| Certification | EN 10204 3.1 MTC · Third-Party Inspection · 100% Radiography |
| Element | Min | Max |
|---|---|---|
| Carbon (C) | — | 0.08 |
| Manganese (Mn) | — | 2.00 |
| Silicon (Si) | — | 0.75 |
| Phosphorus (P) | — | 0.045 |
| Sulphur (S) | — | 0.030 |
| Chromium (Cr) | 17.00 | 19.00 |
| Nickel (Ni) | 9.00 | 12.00 |
| Titanium (Ti) | 5 × C | 0.70 |
| Nitrogen (N) | — | 0.10 |
| Iron (Fe) | Balance | — |
| Property | Value |
|---|---|
| Tensile Strength | 515 MPa (75 KSI) min |
| Yield Strength (0.2% Proof) | 205 MPa (30 KSI) min |
| Elongation (in 50 mm) | 40% min |
| Hardness – Rockwell B | 95 HRB max |
| Hardness – Brinell | 217 HBW max |
| Property | Value |
|---|---|
| Density | 8,027 kg/m³ |
| Elastic Modulus | 193 GPa |
| Thermal Conductivity (100 °C) | 16.1 W/m·K |
| Specific Heat (0–100 °C) | 500 J/kg·K |
| Service Temperature Range | 427 °C – 816 °C (800 °F – 1500 °F) |
| Standard | Designation |
|---|---|
| UNS (USA) | S32100 |
| Werkstoff (Germany) | 1.4541 |
| EN (Europe) | X6CrNiTi18-10 |
| JIS (Japan) | SUS 321 |
| BS (England) | 321S31 / 58B, 58C |
| AFNOR (France) | Z6CNT18-10 |
| SS (Sweden) | 2337 |
The combination of heat tolerance and weld-stable corrosion resistance makes SS 321 fasteners a go-to grade for demanding, safety-critical assemblies:
| Industry | Typical Use |
|---|---|
| Oil & Gas / Petrochemical | refinery piping, heat exchangers, pressure vessels. |
| Power Generation | steam boilers, superheaters, expansion joints, turbine casings. |
| Aerospace | exhaust systems, engine mounts, high-temperature airframe components. |
| Chemical Processing | reactors, storage tanks and acidic service lines. |
| Marine & Offshore | deck hardware and structural bolting in salt-laden environments. |
| Nuclear & Defence | critical assemblies requiring documented traceability. |
| Property | SS 321 | SS 304 | SS 347 |
|---|---|---|---|
| Stabiliser | Titanium | None | Niobium |
| Max service temp | ~816 °C | ~425 °C (sustained) | ~816 °C |
| Weld corrosion resistance | Excellent | Moderate | Excellent |
| Tensile strength (min) | 515 MPa | 515 MPa | 515 MPa |
| Best for | Welded hot service | General purpose | Higher-strength hot service |
Indicative reference pricing (50-pack). Final quotes vary with size, quantity, thread form and raw-material index — request a live quote for accurate figures.
| Size | Unit Price (approx.) | 50-Pack (approx.) |
|---|---|---|
| M8 x 16 | US $24.26 | US $22.47 |
| M8 x 20 | US $27.56 | US $23.75 |
| M8 x 50 | US $28.05 | US $25.74 |
| M8 x 80 | US $36.04 | US $33.48 |
| M10 x 45 | US $29.04 | US $27.00 |
| M12 x 50 | US $24.63 | US $22.34 |
| Nominal Bolt Size | Thread Length |
|---|---|
| ½" | 1.00" |
| ⅝" | 1.25" |
| ¾" | 1.38" |
| ⅞" | 1.50" |
| 1" | 1.75" |
| 1 ⅛" | 2.00" |
| 1 ¼" | 2.00" |
| 1 ⅜" | 2.25" |
| 1 ½" | 2.25" |
SS 321 fasteners are used in welded, high-temperature and corrosive assemblies — refinery piping, heat exchangers, boilers, exhaust systems and chemical plants — where the titanium stabilisation keeps welded joints corrosion-resistant up to about 816 °C.
In the annealed condition SS 321 is essentially non-magnetic because it is austenitic. Cold working (such as thread rolling) can induce slight magnetism, which is normal and does not affect performance.
Both share a similar chromium-nickel base, but 321 adds titanium. This prevents chromium-carbide precipitation during welding and hot service, so 321 outperforms 304 in welded or elevated-temperature applications while 304 remains a cost-effective general-purpose grade.
SS 321 fasteners are typically rated for continuous service between 427 °C and 816 °C (800 °F to 1500 °F), with good oxidation and creep resistance across that range.
Minimum tensile strength is 515 MPa (75 KSI) and minimum yield strength is 205 MPa (30 KSI), with 40% minimum elongation.
Grade 321 is designated UNS S32100 and Werkstoff No. 1.4541 (EN X6CrNiTi18-10, JIS SUS 321).
Yes. Every order ships with an EN 10204 3.1 certificate, and third-party inspection can be arranged for critical projects.
We hold ready stock from M2 to M42 and manufacture custom sizes up to M180 in metric, UNC, UNF, BSW and BSF thread forms.
Get mill-direct pricing, EN 10204 3.1 certification and fast global dispatch from Unifit Fastener.
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