We are Riddhi Siddhi Impex, a Mumbai-based Stainless Steel 309 Foils manufacturer and supplier, established in 2002. Our slitting lines produce this heat-resisting austenitic foil to ASTM A240 / ASME SA-240 in gauges from 0.03-0.08 mm. As an ISO 9001, 14001, and 45001 certified firm, we keep a ready stock and a monthly supply capacity of 400-500 tonnes. We also provide EN 10204 Type 3.1 / 3.2 mill test certificates on request.
309 Stainless Steel foils are ultra-thin flat products rolled from an austenitic grade carrying 22.0 to 24.0% chromium and 12.0 to 15.0% nickel. That chemistry holds a protective oxide scale in oxidising atmospheres up to 1095 °C continuously, or near 980 °C where temperatures cycle. Density is close to 8.0 g/cm³. Against the 18-8 family, the richer analysis slows scaling and keeps thin sections ductile after long spells at red heat, which is why heat treaters seal tool steel inside Type 309 foil envelopes before hardening.
Every 309 stainless steel foil order starts as a source coil on our lines in Mumbai. These Stainless Steel Coils are annealed to ASTM A240 in any width from 3 mm to 2000 mm, and thin gauges below 0.20 mm double as Stainless Steel 309 shim stock. Inspection covers gauge, edge, and surface before dispatch, with certificates issued on request.
We provide ASTM A240 Type 309 foil in annealed soft condition, slit from ready stock to your exact width, with four surface finishes and edge options.
| Parameter | Details |
|---|---|
| Standard | ASTM A240 / ASME SA-240 |
| Aerospace Standard | AMS 5523 |
| Thickness | 0.03 mm to 0.08 mm |
| Width | 3 mm to 2000 mm |
| Width Tolerance | ±0.1 mm |
| Condition | Annealed (Soft) |
| Supply Forms | Cold rolled |
| Surface Finish | BA (Bright Annealed), 2B, Matte, Matte PVC |
| Edge | Slit edge, Mill edge, Deburred edge, Round edge |
Chromium between 22.0 and 24.0% forms the adherent scale that gives AISI 309 stainless steel foil its heat resistance, while nickel stabilises the austenite. Full A240 limits appear below.
| Element | Composition (% by weight) |
|---|---|
| Carbon (C) | 0.20 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.030 max |
| Silicon (Si) | 0.75 max |
| Chromium (Cr) | 22.0 to 24.0 |
| Nickel (Ni) | 12.0 to 15.0 |
| Nitrogen (N) | 0.10 max |
| Iron (Fe) | Balance |
Annealed Type 309 foil reaches a 515 MPa tensile minimum, 205 MPa yield, and 40% elongation, so it wraps and forms without cracking. The grade carries no temper ladder, and figures below roughly 0.38 mm gauge are indicative rather than certified.
| Property | Value (Annealed) |
|---|---|
|
Tensile Strength, minimum
|
515 MPa (75 ksi) |
|
Yield Strength (0.2% offset), minimum
|
205 MPa (30 ksi) |
|
Elongation in 50 mm, minimum
|
40% |
|
Hardness, maximum
|
217 HBW / 95 HRB |
Procurement teams working to a regional specification can cross-check UNS S30900 foil against the designations below. Each entry names the same 22-24 chromium heat-resisting austenitic analysis.
| Country / Standard | Designation |
|---|---|
| USA (UNS) | S30900 |
| Europe (EN) | X12CrNi23-13 |
| Germany (W.Nr) | 1.4833 |
| Japan (JIS) | SUS309 |
| China (GB) | 06Cr23Ni13 |
| Russia (GOST) | 20Х23Н13 |
These 3 industries utilise most of the SS 309 foil leaving our slitting lines. In each, buyers select the grade for scale resistance and strength retention at temperature rather than room-temperature properties.
Heat treaters fold dies, punches, and gauge blocks into Alloy 309 foil pouches so hardening cycles run without decarburisation or surface scaling. A crimped envelope excludes furnace atmosphere at a fraction of the cost of vacuum equipment. Furnace builders take the same foil for muffle linings, baffles, and radiant tube wraps that face red heat daily.
Process plants specify 309 SS foil around reformer seals, flare tips, and duct joints exposed to hot sulphur-bearing gases and combustion products. The 22.0 to 24.0% chromium content slows sulphidation attack that thins ordinary austenitics quickly. Thin slit widths let maintenance crews shim and seal equipment in place during shutdown windows.
Boiler and turbine contractors use UNS S30900 foil in expansion seals, superheater spacers, and lagging strips that flex through every thermal cycle. Strength holds through repeated excursions towards 980 °C in cycling service. Precision slitting to ±0.1 mm keeps multi-ply seal assemblies flat, so sealing faces stay tight between outages.
Consignments move from our Mumbai and Taloja warehouses in wooden cases or on pallets, export papers complete.
| Parameter | Details |
|---|---|
| Packaging | Wooden cases, pallet packing |
| Incoterms | FOB, CIF, CFR, EXW Mumbai |
| Dispatch Points | Mumbai and Taloja warehouses |
| Standard Lead Time | 4 to 5 days |
| Urgent Dispatch | 2 to 3 days |
| Payment Terms | Advance, credit, LC |
| Certification | EN 10204 Type 3.1 / 3.2 mill test certificates on request |
Stainless Steel 309 Foils cost around ₹700-₹1,000 per kg in India, or $8-$12 per kg for export buyers. Nickel surcharges, gauge, slit width, finish, and order volume shift the figure week to week. Call or WhatsApp us for today's rate.
We manufacture Stainless Steel 309 foil from 0.03 mm to 0.08 mm thick, slit to any width between 3 mm and 2000 mm at ±0.1 mm. Heavier flat-rolled material falls under our SS 309 Coil and strip ranges.
SS 309 foil holds 22.0 to 24.0% chromium and 12.0 to 15.0% nickel against the 18-8 analysis of 304, so it resists oxidation up to 1095 °C, where 304 scales beyond roughly 870 °C. Type 309 is the pick once service heat passes what 304 tolerates.
309 stainless steel foil withstands oxidation up to about 1095 °C in continuous service and 980 °C under intermittent heating. Cyclic conditions spall the protective scale sooner, which lowers the practical ceiling.
Our finish options on SS 309 foil are BA (Bright Annealed), 2B, Matte, and Matte PVC. Buyers can pair any of them with slit, mill, deburred, or round edges.
You can buy from a reliable 309 Stainless Steel Foil supplier like Riddhi Siddhi Impex in Mumbai. Ready stock dispatches in 4 to 5 days, urgent orders in 2 to 3 days, and as a manufacturer, supplier, and exporter, we serve buyers across India and abroad. Send your size on call or WhatsApp, and we will provide a quote within 24 hours.
