SS 310 / 310S FastenersUNS S31008 · Manufacturer, trader & 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 — available in this alloy. May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing. Dimensions to ASME B18 where applicable, or your drawing. State the finished fastener specification your project requires on the order. 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. manufactures, trades and exports it from Mumbai; EN 10204 3.1 or 3.2 certificates are available on request / as specified in the PO. Markets we have supplied to include Oman, UAE, Saudi Arabia, Brazil, Argentina, Spain and Chile (India is the home market).
- Stock & mill supply
- EN 10204 3.1 / 3.2
- PMI on request
- 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 (UNS S31008). May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing. 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
- Material
- May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing
- Feedstock (bar)
- ASTM A276 / A479, where applicable
- 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 | May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing |
|---|---|
| Material / feedstock | ASTM A276 / A479 — a bar specification, where applicable; it covers the bar, not the finished fastener |
| Manufacturing route | By type: bolts, studs, cap screws and nuts may be machined from bar, where applicable; threaded rod, U-bolts, eye bolts, anchor and foundation bolts are route-dependent; washers not asserted — all to the purchase specification or project drawing |
| Dimensional standards | ASME B18.2.1 (bolts) · B18.2.2 (nuts) · B18.31.2 (studs) · DIN 931 / 933 / 934 (legacy DIN) |
| 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 may be machined from ASTM A276 / A479 bar, where applicable; the finished fastener specification is to the purchase specification or project drawing, and 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
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
| Iron | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S31008.
SS 310 / 310S Fasteners Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S31008 — Annealed plate & sheet.
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
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. PMI can be arranged on request — state it on your enquiry.
Under technical review for TDS.
| Element | SS 310 / 310S | SS 304 |
|---|---|---|
| Nickel | As specified | As specified |
| Chromium | As specified | As specified |
| Iron | As specified | As specified |
| Manganese | As specified | As specified |
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 | May be machined from ASTM B408 bar (UNS N08800), where applicable; finished fastener requirements are to the purchase specification or project drawing | — | 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 | May be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing | ≈ 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 against your order; PMI can be arranged depending on product and requirements, as specified in the PO.
- 03Processing — cutting, machining or bevelling to your specification, with heat numbers marked as specified in the PO.
- 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.
Standards on this page
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 — questions buyers ask
Is SS 310 / 310S the same as AISI 310S?
AISI 310S, UNS S31008, W.Nr 1.4845 are names used for SS 310 / 310S (W.Nr / EN numbers and older UNS variants are the closest designations; their limits can differ slightly, so specify the UNS number and ASTM grade on the order). Whichever name is on the enquiry, fasteners: may be machined from ASTM A276 / A479 bar (UNS S31008), where applicable.
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?
Usually a heavy hex nut in the same SS 310 / 310S alloy — it may be machined from ASTM A276 / A479 bar, where applicable; finished requirements are to the purchase specification or project drawing.
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