High-temperature, oxidation-resistant bolting in UNS S31000 / S31008 / S31009 — bolts, nuts, washers, studs & anchors to ASTM F593 / F594. Ready stock in Mumbai, India. Global export.
✓ ISO 9001:2015 & PED 2014/68/EU quality system ✓ EN 10204 3.1 test certificate ✓ M3–M56 & custom sizes
Unifit Fastener is a reputable manufacturer, supplier and stockist of Stainless Steel 310 / 310S fasteners, which are designed for the most severe applications that require high temperatures and corrosion resistance. The 310 series of austenitic stainless steels are 25% chromium, 20% nickel, and are exceptionally resistant to oxidation and scaling to approximately 1150 °C with grade 310S (UNS S31008) being the low carbon version of grade 310 which is resistant to sensitisation and intergranular attack during welding and cyclic heating. Whether you're using them in furnace hardware, heat exchangers, a petrochemical reactor, as power plant or cryogenic service, our SS 310/310S bolts, nuts, washers, stud bolts and anchors provide reliable strength where standard 304 and 316 fasteners fall short. All fasteners manufactured from fully traceable quality checked raw material and supplied with fully dual certified ASME & ASTM codes and EN 10204 3.1 documentation. Unifit Fastener's ready stock in Mumbai, precision cold-forging and CNC machining process coupled with its quick turnaround time for exports to any part of the world makes it a perfect choice for sourcing the right grade, size and finish for every client of EPC contractor, OEM and MRO.
Request a QuoteSS 310 and 310S belong to the heat-resistant austenitic family. Their high chromium and nickel content forms a stable, tightly adherent oxide scale that protects the metal during continuous exposure to elevated temperatures, while the fully austenitic structure retains excellent toughness even at cryogenic lows. We also stock 310H (UNS S31009), a controlled higher-carbon variant optimised for creep and rupture strength in sustained high-temperature service.
| Grade | UNS | Werkstoff | Best Suited For |
|---|---|---|---|
| SS 310 | S31000 | 1.4841 | High-temperature strength, general heat & oxidation resistance |
| SS 310S | S31008 | 1.4845 | Welded & cyclic-heat parts — low carbon resists sensitisation |
| SS 310H | S31009 | — | Sustained high-temperature creep / rupture applications |
| Parameter | Details |
|---|---|
| Standards | ASTM / ASME SA/A 193, A194, F593, F594, F1554 |
| Dimensional Standards | DIN, ISO, ANSI/ASME B18, BS, UNI, GOST |
| Bolt / Screw Size | M3 – M56 | 3/16" – 2" | custom sizes |
| Machine Screw Size | M1.6 – M12 |
| Self-Tapping Screw | No. 2 – No. 14 |
| Length Range | 3 mm – 200 mm (and above on request) |
| Thread Type | UNC, UNF, BSW, BSF, Metric coarse/fine, ISO 261/965 |
| Thread Finish | Rolled or cut/tapped (rolled preferred for strength) |
| Head Drive | Hex, socket, six-lobe, Phillips, slotted, square |
| Surface / Coating | Self-colour, passivated, PTFE/Teflon, HDG, zinc, xylan, black oxide |
| Test Certificate | EN 10204 3.1 manufacturer test certificate |
| Certifications | ISO 9001:2015, PED 97/23/EC, AD 2000-Merkblatt W0/W2 |
| Packing | Bulk, small boxes, cartons on pallets, or per customer request |
Nominal composition per ASTM A240 / A276. Values are maximum unless a range is shown.
| Grade | C | Mn | Si | P | S | Cr | Ni | Fe |
|---|---|---|---|---|---|---|---|---|
| 310 (S31000) | 0.25 | 2.00 | 1.50 | 0.045 | 0.030 | 24.0–26.0 | 19.0–22.0 | Bal. |
| 310S (S31008) | 0.08 | 2.00 | 1.50 | 0.045 | 0.030 | 24.0–26.0 | 19.0–22.0 | Bal. |
| 310H (S31009) | 0.04–0.10 | 2.00 | 1.50 | 0.045 | 0.030 | 24.0–26.0 | 19.0–22.0 | Bal. |
| Parameter | Metric Sizes | Imperial Sizes |
|---|---|---|
| Diameter | M3 – M56 (Custom sizes available up to M100) | 3/16" – 2-1/2" (Larger sizes on request) |
| Length | 6 mm – 1000 mm | 1/4" – 39" |
| Thread Types | Metric Coarse, Metric Fine, UNC, UNF, BSW, BSF | UNC, UNF, BSW, BSF |
| Bolt Types | Hex Bolts, Heavy Hex Bolts, Stud Bolts, U-Bolts, Eye Bolts, Anchor Bolts | Available in standard and custom designs |
| Nut Types | Hex Nuts, Heavy Hex Nuts, Lock Nuts, Jam Nuts, Wing Nuts | Standard & Custom |
| Washer Types | Plain Washers, Spring Washers, Square Washers, Fender Washers | Standard & Custom |
| Threaded Rods | M3 – M56 | 3/16" – 2-1/2" |
| Standards | ASTM A193 B8/B8M, ASTM F593, ASTM A194, ASTM F594, DIN, ISO, ANSI/ASME B18, BS, JIS | International Standards |
| Finish | Plain, Pickled & Passivated, PTFE Coated, Xylan Coated, Zinc Plated, Hot-Dip Galvanized, Black Oxide | As per requirement |
| Manufacturing | Cold Forged / Hot Forged / CNC Machined | Custom Manufactured |
| Property | Value (SS 310 / 310S) |
|---|---|
| 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) | ≤ 95 HRB |
| Density | 7.9 – 8.0 g/cm³ |
| Melting Range | ≈ 1400 °C (2550 °F) |
| Property | Value |
|---|---|
| Elastic Modulus | ≈ 200 GPa |
| Thermal Conductivity (100 °C) | ≈ 14.2 W/m·K |
| Mean Thermal Expansion (0–100 °C) | ≈ 15.9 µm/m·°C |
| Specific Heat (0–100 °C) | ≈ 500 J/kg·K |
| Electrical Resistivity | ≈ 0.72 µΩ·m |
| Magnetic Permeability | Low — essentially non-magnetic (annealed) |
| Grade | Werkstoff | UNS | JIS | BS | GOST | EN |
|---|---|---|---|---|---|---|
| SS 310 | 1.4841 | S31000 | SUS 310 | 310S24 | 20Ch25N20S2 | X15CrNi25-20 |
| SS 310S | 1.4845 | S31008 | SUS 310S | 310S16 | 20Ch23N18 | X8CrNi25-21 |
| SS 310H | — | S31009 | — | — | — | — |
| Thread Diameter (in.) | Width Across Flats (F) | Flats Tolerance (Max–Min) | Corner Width (G) (Max–Min) | Head Height (H) (Nominal) | Head Height Tolerance (Max–Min) |
|---|---|---|---|---|---|
| 1/4 | 7/16 | 0.438 – 0.428 | 0.505 – 0.488 | 7/32 | 0.226 – 0.212 |
| 5/16 | 1/2 | 0.500 – 0.489 | 0.577 – 0.557 | 17/64 | 0.273 – 0.258 |
| 3/8 | 9/16 | 0.562 – 0.551 | 0.650 – 0.628 | 21/64 | 0.337 – 0.319 |
| 7/16 | 11/16 | 0.688 – 0.675 | 0.794 – 0.768 | 3/8 | 0.385 – 0.365 |
| 1/2 | 3/4 | 0.750 – 0.736 | 0.866 – 0.840 | 7/16 | 0.448 – 0.427 |
| 9/16 | 7/8 | 0.875 – 0.861 | 1.010 – 0.982 | 31/64 | 0.496 – 0.473 |
| 5/8 | 15/16 | 0.938 – 0.922 | 1.083 – 1.051 | 35/64 | 0.559 – 0.535 |
| 3/4 | 1-1/8 | 1.125 – 1.088 | 1.299 – 1.240 | 41/64 | 0.665 – 0.617 |
| 7/8 | 1-5/16 | 1.312 – 1.269 | 1.516 – 1.447 | 3/4 | 0.776 – 0.724 |
| 1 | 1-1/2 | 1.500 – 1.450 | 1.732 – 1.653 | 55/64 | 0.887 – 0.831 |
| 1-1/8 | 1-11/16 | 1.688 – 1.631 | 1.949 – 1.859 | 31/32 | 0.999 – 0.939 |
| 1-3/8 | 2-1/16 | 2.062 – 1.994 | 2.382 – 2.273 | 1-11/64 | 1.206 – 1.138 |
| 1-1/2 | 2-1/4 | 2.250 – 2.175 | 2.598 – 2.480 | 1-9/32 | 1.317 – 1.245 |
| 1-5/8 | 2-7/16 | 2.438 – 2.356 | 2.815 – 2.686 | 1-25/64 | 1.429 – 1.353 |
| 1-3/4 | 2-5/8 | 2.625 – 2.538 | 3.031 – 2.893 | 1-1/2 | 1.540 – 1.460 |
| 2 | 3 | 3.000 – 2.900 | 3.464 – 3.306 | 1-23/32 | 1.763 – 1.675 |
| 2-1/4 | 3-3/8 | 3.375 – 3.263 | 3.897 – 3.719 | 1-15/16 | 1.986 – 1.890 |
| 2-1/2 | 3-3/4 | 3.750 – 3.625 | 4.330 – 4.133 | 2-5/32 | 2.209 – 2.105 |
| 2-3/4 | 4-1/8 | 4.125 – 3.988 | 4.763 – 4.546 | 2-3/8 | 2.431 – 2.319 |
| Nut Size (mm) | Across Flats (mm) | Hex Nut Height (mm) | Jam Nut Height (mm) |
|---|---|---|---|
| M3 | 5.5 | 2.4 | 1.8 |
| M4 | 7 | 3.2 | 2.2 |
| M5 | 8 | 4.0 | 2.7 |
| M6 | 10 | 5.0 | 3.2 |
| M8 | 13 | 6.5 | 4.0 |
| M10 | 17 | 8.0 | 5.0 |
| M12 | 19 | 10.0 | 6.0 |
| M16 | 24 | 13.0 | 8.0 |
| M20 | 30 | 16.0 | 10.0 |
| M24 | 36 | 19.0 | 12.0 |
The heat and corrosion resistance of SS 310/310S makes it the default bolting choice across process and high-temperature industries:
| Industry | Typical Use |
|---|---|
| Petrochemical & Refineries | reactors, furnace bolting, heat-exchanger flange fasteners |
| Power Generation | boiler, superheater and turbine hardware |
| Chemical Processing | acid and sulphur-bearing environments, pressure-vessel studs |
| Heat Treatment & Furnaces | muffle, radiant-tube and kiln fasteners |
| Pulp & Paper | digesters, recovery boilers, high-temperature ducting |
| Cryogenic & LNG | sub-zero bolting that stays tough at −196 °C |
| Food, Oil & Gas, Cement | sanitary and abrasive-service fastening |
| Property | SS 304 | SS 316 | SS 310 / 310S |
|---|---|---|---|
| Chromium / Nickel | 18 / 8 | 16–18 / 10–14 | 24–26 / 19–22 |
| Max Continuous Temp. | ~870 °C | ~870 °C | ~1150 °C |
| Oxidation / Scaling Resistance | Good | Good | Excellent |
| Chloride Pitting Resistance | Moderate | High (Mo) | Moderate |
| Typical Use | General purpose | Marine / chemical | High-temp / furnace |
Production follows a controlled sequence — raw-material verification, forming (cold or hot forging), thread rolling, heat treatment/annealing, surface finishing and 100% inspection — before packing. Our quality system is certified to ISO 9001:2015 and supports PED 97/23/EC and AD 2000-Merkblatt W0/W2 requirements.
| Type | Standards |
|---|---|
| Bolts / Screws | ASTM/ASME A193/SA193, F593; DIN 931, 933, 912, 6912, 7991; ISO 4014, 4017, 4762; ANSI B18.2.1, B18.3 |
| Nuts | ASTM/ASME A194/SA194, F594; DIN 934, 6923, 985; ISO 4032, 4033, 7040; ANSI B18.2.2 |
| Studs / Rods | ASTM A193, F593; DIN 976, 938, 939; BS 4882 |
| Washers | DIN 125, 127, 9021, 6796; ISO 7089/7090; ANSI B18.22.1 |
Prices vary with size, quantity, standard and finish. The figures below are indicative starting points — request a live quote for accurate, order-specific rates.
| Product | Indicative Price (USD) |
|---|---|
| SS 310 Bolt & Nut set | US $0.01 – 0.10 / piece |
| SS 310 Hex Bolt with Nut & Washer | US $0.02 – 0.10 / piece |
| SS 310 Stud Bolt / Threaded Rod | US $0.80 – 4.70 / kg |
| SS 310 Socket Cap Screw | US $0.35 – 5.00 / piece |
| High-volume / bulk | US $1,200 – 4,500 / ton |
Prices last reviewed for reference only. Click "Request a Quote" for the current price list and ready-stock position.
Both share the same 25% Cr / 20% Ni base. The key difference is carbon: 310S (UNS S31008) has a lower carbon limit (0.08% vs 0.25%), which reduces carbide precipitation and sensitisation. That makes 310S the better choice for welded assemblies and repeated heating-cooling cycles, while 310 offers marginally higher hot strength.
SS 310/310S resists oxidation in continuous service up to about 1150 °C and in intermittent service up to roughly 1035 °C. Above around 1035 °C, continuous exposure is preferred over cycling to keep the protective oxide scale intact.
In the annealed condition they are fully austenitic and essentially non-magnetic. Heavy cold working (such as thread rolling) can induce slight magnetic response, but for practical purposes these fasteners are treated as non-magnetic.
Our bolting is supplied to ASTM/ASME A193/SA193 and F593 (bolts/screws) and A194/SA194 and F594 (nuts), with dimensions to DIN, ISO, ANSI/ASME B18, BS and GOST. Each lot ships with an EN 10204 3.1 test certificate.
Yes. We stock and manufacture 310H (UNS S31009) for creep-critical high-temperature service, and we produce custom sizes, threads, head styles and coatings from M3 up to M56 and beyond on request.
Yes. We hold deep ready stock in Mumbai for same-day dispatch of standard items and export worldwide with proper documentation and secure packing to 40+ countries.
Unifit Fastener delivers certified quality, ready stock and mill-direct pricing — with EN 10204 3.1 documentation on every order.
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