Niobium-stabilised austenitic bolts engineered for high-temperature service, weld-decay resistance and long fatigue life. Available M3–M100 in hex, stud, eye, U, square and anchor styles — dispatched with full traceability.
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Stainless steel 347 bolts are niobium (columbium)-stabilized austenitic bolts constructed for applications where the regular 304 or 316 bolts cannot be used—high temperature, thermal cycling, and/or harsh chemical exposure. The small amount of niobium helps to tie up the carbon before it reacts with chromium, which is why the material does not suffer from weld decay and intergranular corrosion after welding or long periods of time at 425 to 815 °C. It is this one metallurgical advantage that makes the engineers specify SS 347 and its more highly carbonized counterpart SS 347H for refinery heaters, boiler assemblies, expansion joints, and exhausts that never cool down.
You can find Stainless Steel 347 / 347H bolts at Unifit Fastener, which are produced and supplied to ASTM A193, ASME SA193, and ASTM F593 and are available in sizes M3 to M100 and lengths up to 200 mm. All lots are shipped with an EN 10204 3.1 mill test certificate and not a promise—verified chemistry and mechanicals. From standard hex bolts by the pallet to a custom eye bolt run against a drawing, our team converts inquiries into traceable fasteners, ready to install—quickly and at fair mill-direct pricing.
Stainless Steel 347 (UNS S34700, Werkstoff 1.4550) is a chromium-nickel austenitic grade stabilised with niobium and tantalum. Grade 347H (UNS S34709, 1.4961) is the higher-carbon variant (0.04–0.10% C) that delivers superior creep strength for parts running continuously above 500 °C.
Because the stabilising element is fixed into stable carbides, both grades keep their corrosion resistance in the heat-affected zone after welding — a property plain 304 cannot match without post-weld annealing. This makes 347 bolts the go-to choice wherever fasteners are welded, cycled through temperature, or exposed to intergranular attack.
| Parameter | Specification |
|---|---|
| Specifications | ASTM A193 / ASME SA193 / ASTM F593 |
| Standards | DIN, ISO, JIS, GB, IS, BS, ASTM & international |
| Dimension standards | DIN 931, 933, 934, 7991, 976, 125; ASME B18.2.1, B18.3 |
| Thread standards | ASME B1.1 (UN), B1.13M (metric); UNC, UNF, BSW, BSF, metric |
| Size | M3 – M100 | 3/16" – 4" | custom sizes |
| Length | 3 mm – 200 mm | custom lengths |
| Head styles | Hex, square, round, flange, T-head, triangular, countersunk |
| Surface finish | Plain / passivated; PTFE, zinc, xylan, cadmium on request |
| Test certificate | EN 10204 3.1 / PED 97/23/EC compliant |
| Place of origin | India |
| Grade | C | Mn | Si | P | S | Cr | Nb (Cb) | Ni | Fe |
|---|---|---|---|---|---|---|---|---|---|
| 347 | 0.08 max | 2.0 max | 1.0 max | 0.045 max | 0.030 max | 17.0–20.0 | 10×C–1.10 | 9.0–13.0 | Bal. |
| 347H | 0.04–0.10 | 2.0 max | 1.0 max | 0.045 max | 0.030 max | 17.0–19.0 | 8×C–1.10 | 9.0–13.0 | Bal. |
Nb = niobium (columbium); the stabilising element that gives grade 347 its weld-decay resistance.
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| Tensile strength | 515 MPa min | 75,000 psi |
| Yield strength (0.2%) | 205 MPa min | 30,000 psi |
| Elongation | 35% min | 35% min |
| Density | 8.0 g/cm³ | 0.289 lb/in³ |
| Melting point | 1454 °C | 2650 °F |
| Grade | UNS | Werkstoff | JIS | EN | GOST |
|---|---|---|---|---|---|
| 347 | S34700 | 1.4550 | SUS 347 | X6CrNiNb18-10 | 08Ch18N12B |
| 347H | S34709 | 1.4961 | SUS 347H | X6CrNiNb18-12 | — |
| Industry | Typical Use |
|---|---|
| Oil, Gas & Refining | Heater tubes, exhaust flanges, high-temp piping |
| Power Generation | Boiler assemblies, superheaters, expansion joints |
| Petrochemical | Reactor internals, columns operating under heat |
| Construction & Infra | Bridges, high-rise structures, rail tracks |
| Aerospace & Exhaust | Manifolds and systems exposed to thermal cycling |
| Heat Treatment | Furnace fixtures and hardware near 800 °C |
| ASTM Standards | IS Standards | DIN Standards | ISO / ANSI / BS Standards |
|---|---|---|---|
| ASTM A193 Grade B8C | 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 347 and 347H Bolts depends on factors such as bolt size, length, thread type, quantity, manufacturing standard, and surface finish. At Unifit Fastener, we manufacture and supply premium-quality SS 347 and SS 347H bolts in accordance with ASTM, ASME, DIN, ISO, and IS standards at competitive prices for customers in India and worldwide.
For the latest Stainless Steel 347/347H Bolts price list, bulk order discounts, or a customized quotation, please contact our sales team.
| Product | Price Availability |
|---|---|
| Stainless Steel 347 Hex Bolts | Available on Request |
| Stainless Steel 347H Hex Bolts | Available on Request |
| Stainless Steel 347 Heavy Hex Bolts | Get Latest Price |
| Stainless Steel 347H Heavy Hex Bolts | Get Latest Price |
| Stainless Steel 347/347H Stud Bolts | Get Latest Price |
| Stainless Steel 347/347H U Bolts | Get Latest Price |
| Stainless Steel 347/347H Anchor Bolts | Get Latest Price |
| Stainless Steel 347/347H Eye Bolts | Get Latest Price |
Phone: +91 22 66518521
Email: chirag@unifitmetalloys.com
Note: Prices are subject to change based on raw material costs, bolt dimensions, quantity, specifications, and delivery location. Contact us for the latest pricing, stock 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 347 | SS 347H | SS 321 |
|---|---|---|---|
| Stabiliser | Niobium (Nb) | Niobium (Nb) | Titanium (Ti) |
| Carbon | 0.08% max | 0.04–0.10% | 0.08% max |
| Best for | General high-temp | Creep / >500 °C | High-temp, welded |
| Creep strength | Good | Superior | Good |
| Weld-decay resistance | Excellent | Excellent | Very good |
Rule of thumb: choose 347H when parts run continuously above 500 °C and creep matters; standard 347 covers most other high-temperature, corrosion-critical jobs.
Dual-certified to ASTM & ASME codes · EN 10204 3.1 · PED 97/23/EC · Merkblatt AD 2000 W2. Certificates include heat number, chemistry and mechanical results for full traceability.
It is a niobium-stabilised austenitic stainless fastener (UNS S34700) made to ASTM A193. The niobium ties up carbon so the bolt resists intergranular corrosion and weld decay, which makes it ideal for welded, high-temperature assemblies.
Both are niobium-stabilised, but 347H carries a controlled higher carbon range (0.04–0.10%) that gives better creep strength for continuous service above 500 °C. Standard 347 suits general high-temperature and corrosion-critical use.
The primary specification is ASTM A193 / ASME SA193 for high-temperature bolting; ASTM F593 also applies. Dimensions follow DIN and ASME B18 series.
SS 347 bolts perform reliably in continuous service up to roughly 815 °C, retaining strength and oxidation resistance well beyond the range of 304 grade.
Yes. Every order ships with an EN 10204 3.1 mill test certificate showing the heat number, full chemistry and mechanical properties. Third-party inspection is welcome.
Standard stock covers M3–M100 (3/16"–4") in lengths from 3 mm to 200 mm. Custom sizes, heads and threads are produced against your drawing.