Unifit Fastener forges and supplies UNS S31600 / EN 1.4401 flat, spring, Belleville, fender and star washers in M2-M100 sizes, backed by heat-number traceability and MTC 3.1 on every lot.
Ready stock - Custom sizes on drawing - Same-week dispatch | Mumbai, India to Middle East, Europe, Africa, Asia & the Americas
A stainless steel 316 washer is a load-distributing disc placed under a bolt head or nut to spread clamping force, protect the mating surface, and prevent the joint from loosening. What sets the 316 and 316L grades apart from common 304 washers is the addition of 2–3% molybdenum, the single element that lets these washers resist pitting and crevice corrosion in salt water, de-icing chemicals, and acidic process media. At Unifit Fastener, we manufacture the full family of 316 washers — plain, spring, Belleville, fender, star and square — from certified UNS S31600 / EN 1.4401 raw material, then passivate and test each batch before it leaves the floor. The result is a washer that keeps its clamp load in the harshest coastal, marine and chemical environments, where a lesser grade would streak, pit and fail. Whether you need five pieces for a trial or full container loads for a desalination plant, every washer is traceable to its heat number and shipped with a Mill Test Certificate to EN 10204 / 3.1.
Request a Quote| Parameter | Specification |
|---|---|
| Material Grade | SS 316, SS 316L, SS 316H |
| Standards | ASTM A193 / ASME SA193, DIN, ISO, BS, EN, JIS |
| UNS / Werkstoff No. | UNS S31600 / S31603 - EN 1.4401 / 1.4404 |
| Size Range | M2 to M100 (3/32" to 4") |
| Outer Diameter | 5 mm to 300 mm |
| Thickness | 0.3 mm to 12 mm |
| Length / Bore | 3 mm to 200 mm (bore as per drawing) |
| Origin | Indian - European - Japanese (on request) |
| Surface Finish | Bright Annealed, Passivated (ASTM A967), Polished, Natural Mill, PTFE, Zinc, Xylan, Nickel-plated, Dacromet, HDG |
| Heat Treatment | Annealing, Stress Relieving, Quenching & Tempering |
| Test Certificate | EN 10204 / 3.1 MTC, NABL lab report |
| MOQ | 5 pieces (trial) - bulk on request |
| Free Samples | Yes - pre-production sample before mass run |
| Delivery | Ready stock 7-15 days - custom on schedule |
| HSN Code | 7318.22.00 (Other washers, iron/steel) |
Precise, heat-verified chemistry is what gives a 316 washer its corrosion resistance. Values below are in weight percent (%), balance iron.
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N |
|---|---|---|---|---|---|---|---|---|---|
| 316 (min) | - | - | - | - | - | 16.0 | 2.00 | 10.0 | - |
| 316 (max) | 0.08 | 2.0 | 0.75 | 0.045 | 0.030 | 18.0 | 3.00 | 14.0 | 0.10 |
| 316L (min) | - | - | - | - | - | 16.0 | 2.00 | 10.0 | - |
| 316L (max) | 0.03 | 2.0 | 0.75 | 0.045 | 0.030 | 18.0 | 3.00 | 14.0 | 0.10 |
| 316H (min) | 0.04 | - | - | - | - | 16.0 | 2.00 | 10.0 | - |
| 316H (max) | 0.10 | 2.0 | 0.75 | 0.045 | 0.030 | 18.0 | 3.00 | 14.0 | - |
| Grade | Tensile Strength (MPa) min | Yield 0.2% Proof (MPa) min | Elongation (% in 50 mm) min | Rockwell B (HRB) max | Brinell (HB) max |
|---|---|---|---|---|---|
| 316 | 515 | 205 | 40 | 95 | 217 |
| 316L | 485 | 170 | 40 | 95 | 217 |
| 316H | 515 | 205 | 40 | 95 | 217 |
| Property | Value |
|---|---|
| Density | 8.0 g/cm3 (8000 kg/m3) |
| Melting Point | 1400 C (2550 F) |
| Elastic Modulus | 193 GPa |
| Thermal Conductivity (100 C) | 16.3 W/m-K |
| Specific Heat (0-100 C) | 500 J/kg-K |
| Electrical Resistivity | 740 n-ohm-m |
| Coefficient of Thermal Expansion (0-100 C) | 15.9 um/m-C |
| Magnetic Response | Essentially non-magnetic (annealed) |
| Grade | UNS | Werkstoff | Old British BS | Euronorm Name | Swedish SS | Japanese JIS |
|---|---|---|---|---|---|---|
| 316 | S31600 | 1.4401 | 316S31 / 58H | X5CrNiMo17-12-2 | 2347 | SUS 316 |
| 316L | S31603 | 1.4404 | 316S11 | X2CrNiMo17-12-2 | 2348 | SUS 316L |
| 316H | S31609 | 1.4401 | 316S51 | - | - | SUS 316H |
All dimensions in mm. Flattening force and residual spring force in Newtons (N).
| Bolt Size | d1 H14 | d2 H14 | s | h max | h min | Flattening Force N | Residual Spring N |
|---|---|---|---|---|---|---|---|
| 4 | 4.3 | 9 | 1.0 | 1.30 | 1.12 | 4050 | 1400 |
| 5 | 5.3 | 11 | 1.2 | 1.55 | 1.35 | 6700 | 2300 |
| 6 | 6.4 | 14 | 1.5 | 2.00 | 1.70 | 9400 | 4200 |
| 8 | 8.4 | 18 | 2.0 | 2.60 | 2.24 | 17200 | 7700 |
| 10 | 10.5 | 23 | 2.5 | 3.20 | 2.80 | 27500 | 12400 |
| 12 | 13 | 29 | 3.0 | 3.95 | 3.43 | 40000 | 18000 |
| 14 | 15 | 35 | 3.5 | 4.65 | 4.04 | 55000 | 25000 |
| 16 | 17 | 39 | 4.0 | 5.25 | 4.58 | 75000 | 34000 |
| 18 | 19 | 42 | 4.5 | 5.80 | 5.08 | 95000 | 57000 |
| 20 | 21 | 45 | 5.0 | 6.40 | 5.60 | 122000 | 73000 |
| 24 | 25 | 56 | 6.0 | 7.75 | 6.77 | 175000 | 122000 |
| 30 | 31 | 70 | 7.0 | 9.20 | 8.00 | 280000 | 196000 |
| Nominal Size | ID min (A) | ID max (A) | OD (B) | Width (C) | Thickness (D) |
|---|---|---|---|---|---|
| M3 | 3.1 | 3.4 | 6.2 | 1.2 | 0.7 |
| M4 | 4.1 | 4.4 | 7.6 | 1.4 | 0.8 |
| M5 | 5.1 | 5.4 | 9.2 | 1.7 | 1.1 |
| M6 | 6.1 | 6.5 | 11.8 | 2.35 | 1.5 |
| M8 | 8.1 | 8.5 | 14.8 | 2.65 | 1.9 |
| M10 | 10.2 | 10.7 | 18.1 | 3.3 | 2.05 |
| M12 | 12.2 | 12.7 | 21.1 | 3.8 | 2.35 |
| M16 | 16.2 | 17 | 27.4 | 4.8 | 3.3 |
| M20 | 20.2 | 21.2 | 33.6 | 5.8 | 3.8 |
| M24 | 24.5 | 25.5 | 40 | 6.75 | 4.8 |
| M30 | 30.5 | 31.7 | 48.2 | 7.75 | 5.8 |
Approximate weight in kilograms per 1,000 pieces. Contact Unifit for exact weights by drawing.
| Size | Wt (kg/1000) | Size | Wt (kg/1000) | Size | Wt (kg/1000) |
|---|---|---|---|---|---|
| M1.6 | 0.024 | M12 | 6.27 | M36 | 92.1 |
| M2 | 0.037 | M14 | 8.62 | M39 | 133 |
| M2.5 | 0.088 | M16 | 11.3 | M40 | 130 |
| M3 | 0.119 | M18 | 14.7 | M42 | 183 |
| M4 | 0.308 | M20 | 17.2 | M45 | 220 |
| M5 | 0.443 | M22 | 18.3 | M48 | 294 |
| M6 | 1.02 | M24 | 32.3 | M52 | 330 |
| M7 | 1.39 | M27 | 42.3 | M56 | 425 |
| M8 | 1.83 | M30 | 53.6 | M60 | 458 |
| M10 | 3.57 | M33 | 75.3 | M64 | 492 |
Unifit quotes factory-direct - per kg or per 1,000 pieces - with no trader mark-up. Final price depends on size, thickness, finish, quantity and certification level. Prices below are indicative; request a live quote for your BOQ.
| Product | Indicative FOB (US $) |
|---|---|
| DIN 125A SS 316 Flat Washer | $0.08 - $0.09 / piece |
| 316 Stainless Steel Wave Washer | $0.012 - $0.021 / piece |
| 316 Stainless Steel EPDM Sealing Washer | $0.03 - $0.10 / piece |
| 316 E-Type Retaining Ring, DIN 6799 (circlip) | approx $0.10 / piece |
| 316L Flat Washer DIN 125 | $0.05 - $0.20 / piece |
| DIN 9021 316 Fender (large OD) Washer | $0.03 - $0.05 / piece |
| DIN 6797 316 Star / Tooth Lock Washer | $0.01 - $0.09 / piece |
| 316 Serrated Lock Washer | $0.05 - $0.20 / piece |
| Large Heavy-Duty 316 Square-Hole Flat Washer | $0.003 - $0.20 / piece |
| A4 316 Square-End Spring Washer | approx $0.01 / piece |
Unifit manufactures 316 washers to German DIN, American ASTM/ASME/SAE, International ISO, British BS, European EN, Japanese JIS, Indian IS and other national standards, including:
| Flat / Plain Washers | Spring & Lock Washers | Hardened & Special |
|---|---|---|
| DIN 125A / 125B (ISO 7089/7090) | DIN 127 Spring Lock Washer | ASTM F436 / F436M Hardened |
| DIN 126 Plain (ISO 7091) | DIN 128 Curved & Wave | ASTM A193 B8M / A194 8M |
| DIN 433 for cheese-head screws | DIN 6796 Conical Spring | JIS B 1186 Hardened Flat |
| DIN 9021 / 7349 Heavy Duty | DIN 6797 Toothed Lock | BS 4395 HSFG Washer |
| ISO 7089 / DIN 7989 SS Flat | DIN 6798 Serrated | IS 2016 / AS NZS 1252 |
| BS 4320 Flat Washer A-D | DIN 434 / 435 Square Taper | NF E25-513 Hardened |
The difference comes down to molybdenum. Where 304 washers begin to pit in chloride environments, 316 keeps performing. Use this comparison to specify correctly.
| Parameter | SS 304 Washer | SS 316 Washer |
|---|---|---|
| Molybdenum Content | 0% | 2-3% |
| Nickel Content | 8 - 10.5% | 10 - 14% |
| PREN (Pitting Resistance) | approx 18 | approx 24 |
| Max Chloride Exposure | approx 200 ppm | approx 1000 ppm |
| Best For | Indoor, dry, low-corrosion | Marine, chemical, coastal, food-grade |
| Relative Cost Index (304 = 100) | 100 | approx 135 |
Every Unifit 316 washer follows a controlled, six-stage process with traceability at each step:
Unifit backs every 316 washer lot with documented testing. We can supply the following certificates and reports on request:
| Certification | Certification |
|---|---|
| ISO 9001:2015 (Quality) | ISO 14001:2015 (Environment) |
| OHSAS 18001:2007 (Safety) | PED 2014/68/EU Certified |
| ASTM A967 Passivation | Petrofac Approved (on request) |
316-grade washers are the default choice wherever chlorides, moisture or aggressive chemistry attack the joint. Unifit supplies to:
| Industry | Typical Use |
|---|---|
| Marine & Shipbuilding | Decks, rails, seawater fittings |
| Desalination Plants | High-chloride process assemblies |
| Offshore Oil & Gas | Platform structures, seawater duty |
| Swimming Pool & Spa | Chlorinated-water equipment |
| Coastal & Structural Construction | Bridges, facades, waterfront builds |
| Chemical & Petrochemical Plants | Acidic and corrosive service |
| Pharma & Biotech Skids | Clean-room, hygienic fastening |
| Pump & Valve Assembly | Seawater and slurry duty |
| Power Generation & Wind Towers | Weather-exposed structural bolting |
| Food, Dairy & Beverage | Corrosion-safe, wash-down joints |
Unifit ships 316 washers worldwide - including the UAE, Saudi Arabia, Qatar, Kuwait, Oman, USA, Canada, UK, Germany, Italy, France, Spain, Netherlands, Malaysia, Singapore, Vietnam, Philippines, Indonesia, South Korea, Japan, Brazil, Peru, Colombia, Argentina, South Africa, Nigeria, Kenya, Egypt, Turkey, Russia and Australia - with weekly dispatch on standard stock sizes.
| Term | Detail |
|---|---|
| Payment Terms | T/T, L/C, Western Union, PayPal, Trade Assurance (30% deposit, balance before shipping) |
| Port of Dispatch | Mumbai / Nhava Sheva, Maharashtra, India |
| Delivery Time | Standard stock 7-15 days |
| HSN Code | 7318.22.00 - GST 18% (domestic) - RoDTEP eligible |
| Free Samples | Yes, pre-production approval samples |
A. In its annealed condition a 316 washer is essentially non-magnetic. Heavy cold-working can induce very slight magnetism, but for practical purposes 316 is treated as non-magnetic.
A. The 2-3% molybdenum in 316 gives it markedly better resistance to chloride pitting and crevice corrosion than 304, which is why 316 is specified for marine, coastal and chemical service.
A. Yes. Grade 316 is the standard choice for seawater and chloride-rich environments, offering roughly 2.5x the salt-spray life of 304.
A. 316L has a lower maximum carbon content (<=0.03%), which resists sensitization during welding. Choose 316L for welded assemblies and standard 316 where slightly higher strength is preferred.
A. Every lot ships with an EN 10204 / 3.1 MTC traceable to the heat number. PMI, salt-spray and PED certificates are available on request.
A. Yes. We produce non-standard bores, ODs, thicknesses and profiles to your drawing, with a free pre-production sample before the main run.
A. Trials start at just 5 pieces. Bulk and container-load pricing is available for production quantities.
A. Bright annealed, passivated (ASTM A967), polished, natural mill, plus PTFE, Xylan, zinc, nickel-plated, Dacromet and hot-dip galvanised coatings.
Send your size, quantity and schedule - get a factory price with MTC 3.1 in 24 hours. Ready stock and custom sizes for marine, chemical and coastal projects across India, the UAE, Europe and beyond.
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