SS 310 / 310S FastenersASTM A276 UNS S31008 · Manufacturer, stockist & exporter, India
Also sold as AISI 310S · UNS S31008 · W.Nr 1.4845 · Heat-resisting stainless
SS 310 / 310S fasteners — stud bolts, hex bolts, nuts and washers — are made from ASTM A276 / A479 bar stock to ASME B18 dimensions. It is a heat-resisting austenitic stainless steel with 25% chromium and 20% nickel, chosen for furnaces, burners and heat treatment at high temperature. 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 310 / 310S Fasteners?
SS 310 / 310S fasteners is a heat-resisting austenitic stainless steel with 25% chromium and 20% nickel supplied as fasteners to ASTM A276 / A479 (UNS S31008). Buyers specify it for furnaces, burners and heat treatment at high temperature. It is also sold as AISI 310S, UNS S31008, W.Nr 1.4845.
- What it is
- Heat-resisting austenitic stainless steel with 25% chromium and 20% nickel
- Bar stock
- ASTM A276 / A479
- Dimensions
- ASME B18.2.1 · B18.2.2 · B18.31.2
- Threads
- UNC · UN-8 · metric
- Sizes
- M10 – M64 · ½" – 4"
- Best at
- Furnaces, burners and heat treatment at high temperature
SS 310 / 310S Fasteners Specification & Sizes
| Material | ASTM A276 / A479 |
|---|---|
| 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 310 / 310S Stud Bolts: Grade & Nut Pairing
SS 310 / 310S studs and nuts are machined from ASTM A276 / A479 bar; the nut is usually the same alloy. 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 310 / 310S Fasteners Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 24.0 – 26.0 |
| Nickel | 19.0 – 22.0 |
| Carbon | 0.08 max |
| Manganese | 2.00 max |
| Silicon | 1.50 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
| Iron | Balance |
SS 310 / 310S 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 | 7.9 g/cm³ |
| Melting range | 1400 – 1450 °C |
| Magnetic | Non-magnetic annealed |
| PREN (approx.) | ≈ 25 |
SS 310 / 310S Equivalent Grades
Values follow ASTM A240 for UNS S31008. 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 310 / 310S 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 310 / 310S is most often mixed up with SS 304 — 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 310 / 310S | SS 304 |
|---|---|---|
| Nickel | 19.0 – 22.0 | 8.0 – 10.5 |
| Chromium | 24.0 – 26.0 | 17.5 – 19.5 |
| Iron | Balance | Balance |
| Manganese | 2.00 max | 2.00 max |
SS 310 / 310S fasteners by type
SS 310 / 310S Fasteners Applications
SS 310 / 310S 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 310 / 310S Fasteners vs 304, 321 and 800
| Grade | Fasteners standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| Incoloy 800 / 800H / 800HT | ASTM B408 | — | Furnaces, petrochemical heaters and high-temperature piping |
| SS 304 | ASTM A193 B8 · A194 8 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| 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 310 / 310S 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 310S fits.
25% chromium builds a tight scale that resists oxidation in continuous service up to about 1100 °C.
20% nickel keeps the alloy austenitic and strong at furnace temperatures.
Silicon improves resistance to scaling and carburising atmospheres.
Without molybdenum, 310S is not a chloride grade — use it for heat, not for seawater.
How your 310S 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 310 / 310S Fasteners
SS 310 / 310S welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER310 (AWS A5.9) |
|---|---|
| Over-alloyed filler | ERNiCr-3 for joints to nickel alloys |
| 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 310S fittings and 310S flanges for the matching pipe-system parts.
How to Order SS 310 / 310S 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 310 / 310S fasteners for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 310 / 310S fasteners — questions buyers ask
Is SS 310 / 310S the same as AISI 310S?
Yes. AISI 310S, UNS S31008, W.Nr 1.4845 all refer to the same material, and fasteners is ordered to ASTM A276 / A479 whichever name is on the enquiry.
Why use SS 310 / 310S bolts instead of B7 carbon steel?
On SS 310 / 310S flanges in corrosive service, carbon-steel bolts corrode first. Matching-alloy bolting avoids galvanic corrosion and bolt failure.
What nut goes with SS 310 / 310S stud bolts?
A heavy hex nut machined from the same SS 310 / 310S bar (ASTM A276 / A479), unless the project specifies otherwise.
How do I stop SS 310 / 310S bolts galling?
Use an anti-seize compound on threads and nut faces, tighten at moderate speed, and do not reuse galled nuts.
SS 310 / 310S or Incoloy 800 / 800H / 800HT — which should I choose?
SS 310 / 310S is chosen for furnaces, burners and heat treatment at high temperature. Incoloy 800 / 800H / 800HT 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