Manufacturer, stockist & global exporter of titanium-stabilised SS 321 bolts engineered for service up to 816°C.
Unifit Fastener is a reputable manufacturer, stockist, and exporter of Stainless Steel 321 bolts, which is a grade of titanium-stabilized austenitic stainless steel that is valued for its performance properties when ordinary stainless steel fails. Our SS 321 bolts are the reliable choice for equipment subjected to hot operating temperatures, temperature fluctuations, and harsh chemical environments since they are alloyed with titanium to resist the chromium-carbide precipitation that leads to intergranular corrosion after welding. The strength of each UNS S32100 bolt we ship will hold up indefinitely at temperatures up to approximately 816°C and will with greater ease resist the effects of oxidation and scaling than grade 304. All of our fasteners, with their respective thread sizes ranging from M3 to M100, come in metric, UNC, UNF, BSW, and BSF threads and are accompanied by an EN10204 3.1 mill test certificate. In addition to certified 321 bolts, We offer tight tolerances of ±0.03 mm, fast global dispatch, and third-party inspection, providing refineries, power plants, exhaust manufacturers, and boiler manufacturers with a high degree of confidence when it comes to sourcing their 321 bolts. Get a free sample or same-day quote to get the ball rolling.
A Stainless Steel 321 bolt is a threaded fastener made from austenitic grade 321 (UNS S32100) — essentially an 18/8 chromium-nickel stainless steel with a deliberate titanium addition. That titanium "stabilises" the alloy: during welding or prolonged high-temperature service, titanium locks up carbon before it can combine with chromium, preventing sensitisation and the weld-decay it causes. The result is a bolt that keeps its corrosion resistance and mechanical integrity in the 425–900°C band where standard 304 fasteners would weaken.
| Specification | Details |
|---|---|
| Standard | ASTM A193 / ASME SA193 · DIN · ISO · JIS · BS · IS · GB |
| Material Grade | SS 321 / UNS S32100 / DIN 1.4541 / AISI 321 |
| Size Range | M3 – M100 | 3/16" – 4" | custom sizes |
| Bolt Length | 3 mm – 200 mm | custom lengths |
| Dimension Standards | DIN 931, 933, 934, 976, 7991, 125 · ASME B18.2.1, B18.3 |
| Thread Types | Metric, UNC, UNF, BSW, BSF (or as required) |
| Thread Config | ASME B1.1 2A/3A · 2B/3B (inch) · B1.13M 6h-6G (metric coarse) |
| Form | Hex, square, round, threaded as per gauge |
| Head Style | Hex, square, round, flange, flat, T-head, truss, button |
| Neck Type | Hex, square, triangular, oval, knurled |
| Surface Finish | Passivation, plain, black oxide, zinc, PTFE/Xylan, galvanized |
| Tolerance | OEM / ODM · ±0.03 mm |
| Test Certificate | EN 10204 3.1 · PED 97/23/EC · AD 2000 W2 |
| Origin | India |
| C | Mn | Si | P | S | Cr | Ni | Ti | N |
|---|---|---|---|---|---|---|---|---|
| 0.08 max | 2.0 max | 1.0 max | 0.045 max | 0.030 max | 17.0–19.0 | 9.0–12.0 | 5×(C+N)–0.70 | 0.10 max |
| Property | Value (min) |
|---|---|
| Tensile Strength | 515 MPa (75,000 psi) |
| Yield Strength (0.2% offset) | 205 MPa (30,000 psi) |
| Elongation (in 50 mm) | 40% |
| Hardness — Rockwell B (max) | 95 HRB |
| Hardness — Brinell (max) | 217 HB |
| Density | 8.0 g/cm³ |
| Melting Point | 1457°C (2650°F) |
| Service Temperature | up to ~816°C |
| Magnetic Permeability | ≤ 1.02 (annealed) |
| Standard (SS) | Werkstoff Nr. | UNS | JIS | EN |
|---|---|---|---|---|
| SS 321 | 1.4541 | S32100 | SUS 321 | X6CrNiTi18-10 |
All dimensions in inches unless noted. E = body diameter, F = width across flats, G = width across corners, H = head height.
| Nom. Size | E (max) | F (across flats) | G (across corners) | H (head height) |
|---|---|---|---|---|
| 1/4" | 0.260 | 0.438 | 0.505 | 11/64 |
| 5/16" | 0.324 | 0.500 | 0.577 | 7/32 |
| 3/8" | 0.388 | 0.562 | 0.650 | 1/4 |
| 1/2" | 0.515 | 0.750 | 0.866 | 11/32 |
| 5/8" | 0.642 | 0.938 | 1.083 | 27/64 |
| 3/4" | 0.768 | 1.125 | 1.299 | 1/2 |
| 7/8" | 0.895 | 1.312 | 1.516 | 37/64 |
| 1" | 1.022 | 1.500 | 1.732 | 43/64 |
| 1-1/4" | 1.277 | 1.875 | 2.165 | 27/32 |
| 1-1/2" | 1.531 | 2.250 | 2.598 | 1 |
Full ASME B18.2.1 / DIN 931 dimension charts up to 4" available on request or in the downloadable spec sheet.
Indicative standard dry torque values in inch-pounds. Always confirm against your joint design, lubrication and engineering spec before final tightening.
| Bolt Size | Threads/Inch | STD Dry Torque (in-lb) |
|---|---|---|
| 1/4" | 20 | 75.2 – 78.8 |
| 5/16" | 18 | 132 – 138 |
| 3/8" | 16 | 236 – 247 |
| 7/16" | 14 | 376 – 393 |
| 1/2" | 13 | 517 – 542 |
| 9/16" | 12 | 682 – 713 |
| 5/8" | 11 | 1110 – 1160 |
| 3/4" | 10 | 1530 – 1582 |
| 7/8" | 9 | 2328 – 2430 |
| 1" | 8 | 3440 – 3595 |
Grade 321's high-temperature strength and oxidation resistance make it the go-to fastener wherever heat and corrosion meet:
| ASTM Standards | IS Standards | DIN Standards | ISO / ANSI / BS Standards |
|---|---|---|---|
| ASTM A193 Grade B8T | IS 1363 | DIN 444 | ISO 4014 |
| ASTM A193 | IS 1364 | DIN 580 | ISO 4017 |
| ASTM A320 | IS 1367 | DIN 931 | ISO 4762 |
| ASTM F593 | IS 3757 | DIN 933 | ISO 7412 |
| ASTM F1554 (Anchor Bolts) | IS 6639 | DIN 960 | ISO 8676 |
| ASTM F568 (where applicable) | DIN 961 | ANSI B18.2.1 | |
| DIN 976 | ANSI B18.2.3 | ||
| DIN 6921 | ANSI B18.3 | ||
| DIN 6922 | BS EN ISO 4014 | ||
| DIN 6914 | BS EN ISO 4017 | ||
| DIN 6915 | BS 3692 | ||
| DIN 7990 |
The price of Stainless Steel 321 Bolts varies depending on the bolt size, length, thread type, quantity, manufacturing standard, and surface finish. At Unifit Fastener, we supply premium-quality SS 321 bolts manufactured in accordance with ASTM, ASME, DIN, ISO, and IS standards at competitive prices for domestic and international markets.
For the latest Stainless Steel 321 Bolts price list, bulk order discounts, or a customized quotation, please get in touch with our sales team.
| Product | Price Availability |
|---|---|
| Stainless Steel 321 Hex Bolts | Available on Request |
| Stainless Steel 321 Heavy Hex Bolts | Get Latest Price |
| Stainless Steel 321 Stud Bolts | Get Latest Price |
| Stainless Steel 321 Eye Bolts | Get Latest Price |
| Stainless Steel 321 U Bolts | Get Latest Price |
| Stainless Steel 321 Anchor Bolts | Get Latest Price |
| Stainless Steel 321 Carriage Bolts | Get Latest Price |
| Stainless Steel 321 Flange Bolts | Get Latest Price |
Phone: +91 22 66518521
Email: chirag@unifitmetalloys.com
Note: Prices are subject to change based on raw material costs, dimensions, quantity, specifications, and delivery location. Contact us for the latest pricing, availability, and bulk order discounts.
| Nominal Size | Thread Type | Available Lengths | Metric Equivalent |
|---|---|---|---|
| 1/4"-20 | UNC | 1/2" – 4" | M6 |
| 5/16"-18 | UNC | 1/2" – 6" | M8 |
| 3/8"-16 | UNC | 1" – 8" | M10 |
| 1/2"-13 | UNC | 1" – 10" | M12 |
| 5/8"-11 | UNC | 1-1/2" – 12" | M16 |
| 3/4"-10 | UNC | 2" – 12" | M20 |
| 7/8"-9 | UNC | 2" – 12" | M22 |
| 1"-8 | UNC | 2" – 16" | M24 |
| M6 | Metric Coarse | 12–100 mm | 1/4" |
| M8 | Metric Coarse | 16–120 mm | 5/16" |
| M10 | Metric Coarse | 20–150 mm | 3/8" |
| M12 | Metric Coarse | 25–200 mm | 1/2" |
| M16 | Metric Coarse | 30–250 mm | 5/8" |
| M20 | Metric Coarse | 40–300 mm | 3/4" |
| M24 | Metric Coarse | 50–300 mm | 1" |
| M27 | Metric Coarse | 60–350 mm | – |
| M30 | Metric Coarse | 70–400 mm | – |
| M36 | Metric Coarse | 80–500 mm | – |
Approximate Weight in kg per 100 Pieces (As per IS 1363 / ISO 4017 Dimensions)
| Length (mm) | M5 | M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 |
|---|---|---|---|---|---|---|---|---|---|---|
| 16 | 0.448 | 0.743 | 1.590 | 3.211 | – | – | – | – | – | – |
| 20 | 0.598 | 0.812 | 1.711 | 3.411 | 4.892 | – | – | – | – | – |
| 25 | 0.660 | 0.897 | 1.871 | 3.660 | 5.252 | 8.170 | – | – | – | – |
| 30 | 0.737 | 1.010 | 2.070 | 3.912 | 5.574 | 9.690 | 10.707 | – | 18.657 | – |
| 35 | 0.804 | 1.120 | 2.271 | 4.223 | 5.974 | 10.000 | 11.416 | 16.026 | 19.608 | – |
| 40 | 0.881 | 1.230 | 2.470 | 4.533 | 6.410 | 10.288 | 12.107 | 16.667 | 20.747 | – |
| 45 | 0.958 | 1.340 | 2.671 | 4.840 | 6.859 | 10.504 | 12.821 | 17.241 | 21.739 | – |
| 50 | 1.030 | 1.450 | 2.870 | 5.155 | 7.299 | 11.261 | 13.624 | 17.857 | 22.727 | 28.409 |
| 60 | – | 1.670 | 3.270 | 5.774 | 8.183 | 12.255 | 15.244 | 20.000 | 25.126 | 32.051 |
| 80 | – | 2.111 | 4.072 | 7.013 | 10.000 | 13.889 | 18.248 | 24.510 | 30.303 | 40.000 |
| 100 | – | – | 4.873 | 8.251 | 11.820 | 16.340 | 21.459 | 27.778 | 35.714 | 46.296 |
| 120 | – | – | – | 9.506 | 13.624 | 18.797 | 24.631 | 32.895 | 40.984 | 50.000 |
| 150 | – | – | – | 11.312 | 16.340 | 22.222 | 29.412 | 37.594 | 48.544 | 58.824 |
| 200 | – | – | – | 14.327 | 20.833 | 29.586 | 37.594 | 49.020 | 60.976 | 73.529 |
| 250 | – | – | – | 17.301 | 25.381 | – | 45.455 | – | 74.627 | 87.719 |
| 300 | – | – | – | 20.325 | 29.940 | – | 53.763 | – | 87.719 | 104.167 |
| 400 | – | – | – | – | 39.063 | – | 69.444 | – | 113.636 | – |
| Property | SS 321 | SS 304 | SS 347 |
|---|---|---|---|
| Stabiliser | Titanium | None | Niobium (Nb) |
| Max service temp | ~816°C | ~425°C (sustained) | ~816°C |
| Weld-decay resistance | Excellent | Poor (sensitises) | Excellent |
| Best for | Hot + welded parts | General purpose | Hot + heavy welds |
| Relative cost | Moderate | Lowest | Higher |
| Typical UNS | S32100 | S30400 | S34700 |
Choose 321 when parts are welded and run hot; choose 347 for the heaviest sections needing extra stabilisation; choose 304 for standard, cooler service.
Wire drawing → cold heading / cold forging → hot forging (for large sizes) → insert thread tapping → CNC machining → heat treatment → surface finishing → inspection → packing.
| Code | Condition Furnished |
|---|---|
| CW | Headed & rolled from annealed stock, acquiring a degree of cold work |
| AF | Headed & rolled from annealed stock, then re-annealed |
| A | Machined from annealed / solution-annealed stock (retains base properties) |
| SH | Machined from strain-hardened / cold-worked stock for specific properties |
A. SS 321 bolts are used in high-temperature and corrosive service — exhaust systems, boilers, heat exchangers, pressure vessels, expansion joints and petrochemical plants — because the titanium-stabilised grade keeps its strength and corrosion resistance up to around 816°C.
A. Grade 321 adds titanium, which prevents chromium-carbide precipitation (weld decay) and lets the bolt run hot to ~816°C. Grade 304 has no stabiliser and is better suited to general, lower-temperature use up to about 425°C in sustained service.
A. Stainless Steel 321 is UNS S32100, Werkstoff (DIN) 1.4541, JIS SUS 321 and EN X6CrNiTi18-10.
A. They offer continuous service up to roughly 816°C and resist oxidation and scaling well above that intermittently, which is why they are specified for exhaust, furnace and boiler applications.
A. Unifit Fastener supplies SS 321 bolts from M3 to M100 (3/16" to 4") in metric, UNC, UNF, BSW and BSF threads, in lengths from 3 mm to 200 mm, plus custom sizes to drawing.
A. Yes. Every consignment ships with an EN 10204 Type 3.1 mill test certificate showing chemical composition and mechanical properties, with PED 97/23/EC certification available on request.
A. In the annealed condition grade 321 is essentially non-magnetic (magnetic permeability ≤ 1.02); heavy cold work can induce slight magnetism.
Get certified UNS S32100 bolts from ready stock — with EN 10204 3.1 documentation, free samples and worldwide export.
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