SS 904L Fasteners Supplier in IndiaUNS N08904 · company QMS ISO 9001:2015
Also sold as Alloy 904L · UNS N08904 · W.Nr 1.4539 · 2RK65
SS 904L fasteners — stud bolts, hex bolts, nuts and washers — available in this alloy. May be machined from ASTM A479 bar (UNS N08904), 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 super-austenitic stainless steel with high nickel, molybdenum and copper, chosen for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. Kanak Steel & Engineering Co. manufactures, trades and exports SS 904L fasteners; depending on the product and order, material is produced or sourced and processed to the PO. 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).
- Mill & traded 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 904L Fasteners?
SS 904L fasteners is a super-austenitic stainless steel with high nickel, molybdenum and copper supplied as fasteners (UNS N08904). May be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing. Buyers specify it for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. It is also sold as Alloy 904L, UNS N08904, W.Nr 1.4539.
- What it is
- Super-austenitic stainless steel with high nickel, molybdenum and copper
- Material
- May be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing
- Feedstock (bar)
- ASTM 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
- Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water
SS 904L Fasteners Specification & Sizes
| Material | May be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing |
|---|---|
| Material / feedstock | ASTM 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 904L Stud Bolts: Grade & Nut Pairing
SS 904L studs and nuts may be machined from ASTM 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 904L Fasteners Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel | As specified |
| Chromium | As specified |
| Molybdenum | As specified |
| Copper | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Nitrogen | 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 N08904.
SS 904L 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 N08904 — Annealed plate & sheet.
Density & Physical Properties
| Property | Value |
|---|---|
| Density | 7.95 g/cm³ |
| Melting range | 1300 – 1390 °C |
| Magnetic | Non-magnetic (annealed) |
| PREN (approx.) | ≈ 35 |
SS 904L 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 904L 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 904L is most often mixed up with Inconel 825 — 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 904L | Inconel 825 |
|---|---|---|
| Nickel | As specified | As specified |
| Chromium | As specified | As specified |
| Molybdenum | As specified | As specified |
| Copper | As specified | As specified |
| Titanium | — | As specified |
| Iron | As specified | As specified |
| Manganese | As specified | As specified |
SS 904L fasteners by type
SS 904L Fasteners Applications
SS 904L 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 904L Fasteners vs 316L, 2205 and 825
| Grade | Fasteners standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 316 / 316L | ASTM A193 B8M · A194 8M | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| Inconel 825 | May be machined from ASTM B425 bar (UNS N08825), where applicable; finished fastener requirements are to the purchase specification or project drawing | ≈ 31 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking |
| Duplex 2205 | ASTM A1082 (S32205) where specified for applicable duplex bolts, studs, cap screws and nuts; for other types, material may be supplied to ASTM A276 / A479 bar where applicable, subject to the purchase specification | ≈ 35 | Strength with chloride resistance at a stainless-steel budget |
| SS 904L | May be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing | ≈ 35 | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
PREN = Cr + 3.3 Mo + 16 N, from mid-range chemistry. A screening guide, not a substitute for corrosion data on your medium.
SS 904L 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 904L fits.
Elevated nickel gives far better resistance to chloride cracking than 316L.
Molybdenum lifts pitting resistance well above ordinary austenitic grades (screening PREN on the grade page).
Copper is what makes 904L the stainless steel of choice for dilute sulphuric acid.
Very low carbon limits carbide precipitation, so welds keep their corrosion resistance.
How your 904L 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 904L Fasteners
SS 904L welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER385 (AWS A5.9) |
|---|---|
| Over-alloyed filler | ERNiCrMo-3 for severe chloride service |
| 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 904L fittings and 904L flanges for the matching pipe-system parts.
How to Order SS 904L 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
Technical documentation
A Kanak Steel technical data sheet for this product is being prepared. It is released as a PDF only after the current standard text, each value and its evidence, and a named technical reviewer have been confirmed — so no draft or placeholder sheet is offered for download.
Need technical data now? Send your enquiry with the standard and edition you are ordering to.
| Document | SS 904L — Fasteners technical data sheet |
|---|---|
| Document ID | KS-TDS-N08904-FS |
| Grade | SS 904L |
| UNS | N08904 |
| Product form | Fasteners |
| Standard | Finished fastener specification not asserted; bar feedstock to ASTM A479 where applicable |
| Status | Under technical review for TDS |
- Technical Data Sheet — Under technical review
SS 904L fasteners — questions buyers ask
Is SS 904L the same as Alloy 904L?
Alloy 904L, UNS N08904, W.Nr 1.4539 are names used for SS 904L (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 A479 bar (UNS N08904), where applicable.
Why use SS 904L bolts instead of B7 carbon steel?
On SS 904L flanges in corrosive service, carbon-steel bolts corrode first. Matching-alloy bolting avoids galvanic corrosion and bolt failure.
What nut goes with SS 904L stud bolts?
Usually a heavy hex nut in the same SS 904L alloy — it may be machined from ASTM A479 bar, where applicable; finished requirements are to the purchase specification or project drawing.
How do I stop SS 904L bolts galling?
Use an anti-seize compound on threads and nut faces, tighten at moderate speed, and do not reuse galled nuts.
SS 904L or Inconel 825 — which should I choose?
SS 904L is chosen for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. Inconel 825 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