Stainless Steel
Grade 309S
Fasteners · Mumbai
Why Stainless-Steel Grade 309S Genuinely Differs from General-Purpose Stainless
Standard 304 and 316-series stainless are corrosion-resistant grades first — they perform well against a wide range of chemical attack at moderate temperatures, but that composition wasn’t specifically optimized to resist scaling and oxidation at genuinely sustained high temperatures.
309S takes a different starting point — chromium content is deliberately raised into the 22–24% range, well above the roughly 18% typical of 304-series grades, along with meaningfully higher nickel. That composition shift exists specifically to build a protective, adherent oxide layer that continues to hold up under sustained heat, rather than breaking down and scaling the way lower-chromium grades eventually do at the same temperature.
The “S” suffix carries the same low-carbon logic used across the broader L-grade family — carbon is controlled to a low level specifically to resist chromium carbide precipitation at grain boundaries during and after welding, which matters directly for 309S because this grade is frequently welded into furnace and kiln equipment where weld integrity at high temperature is genuinely critical.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our 309S fastener range is verified by chemical composition and mechanical testing under our ISO 9001:2015 quality system.
Where This Material Genuinely Applies
Genuine Sustained Oxidation Resistance
Elevated chromium content resists scaling at temperatures well beyond general-purpose stainless.
Correct Choice for Welded Furnace Equipment
Low-carbon composition resists weld decay in exactly the equipment types this grade is used in.
Cost-Effective Alternative to Higher-Nickel Grades
Delivers meaningful high-temperature capability at a more accessible cost than 310S or nickel superalloys.
Verified Composition & Mechanical Properties
Batch testing confirms genuine chromium and nickel content for every lot.
Choosing Between Related Heat-Resistant Grades
SS 304 / 304L / 304H
Solid general corrosion resistance, but composition wasn’t specifically built for sustained high-temperature oxidation resistance.
View SS 304 Guide →SS 309S (This Page)
Elevated chromium and nickel deliberately for sustained oxidation resistance, at a more accessible cost than higher-alloy options.
You Are HereSS 310S
Even higher chromium and nickel than 309S, for genuinely more extreme sustained temperatures beyond 309S’s typical service ceiling.
Higher-Tier Grade309S vs 310S — Quick Reference
Confirming the actual sustained service temperature before ordering avoids overpaying for the higher-alloy grade when 309S is sufficient. This table is the quick reference we use with buyers before quoting.
| Aspect | SS 309S | SS 310S |
|---|---|---|
| Chromium Content | ~22–24% | ~24–26% |
| Nickel Content | ~12–15% | ~19–22% |
| Typical Oxidation Resistance Ceiling | ~1000°C | ~1100°C+ |
| Relative Cost | More accessible | Higher, due to nickel content |
309S Specification Details
Nominal Composition
- Chromium 22.0 – 24.0%
- Nickel 12.0 – 15.0%
- Carbon ≤0.08% (Low, “S” Grade)
- Iron Balance
Typical Mechanical Range
- Tensile Strength ~515 MPa Min
- Yield Strength ~205 MPa Min
- Service Temperature Up to ~1000°C
- Elongation 40% Min
Fastener Types We Manufacture
- Bolts & Studs Hex, Heavy Hex
- Nuts Hex, Heavy Hex
- Washers Flat, Spring
- Custom Sizes On Request
Application Areas
Wherever sustained oxidizing heat genuinely exceeds what general-purpose stainless can handle.
Furnace & Kiln Equipment
structural and fastening use
Heat Treatment Equipment
at sustained elevated temperature
Boiler & Combustion Equipment
heat and oxidation exposure
Refractory Anchor Systems
attachment fastening
Petrochemical Process Furnaces
in process furnace equipment
Exhaust & Emissions Equipment
oxidizing exhaust exposure
Ceramic & Glass Manufacturing
and furnace fastening
General Sustained High-Temperature Assembly
requiring oxidation resistance at heat
Standard Export Documentation
Prepared as standard practice for every 309S fastener shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Chemical Composition Report
Confirms actual chromium and nickel content fall within the specified 309S grade range.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/size specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical, dimensional, and high-temperature testing available on request.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
SS 304 / 304L / 304H
Our general-purpose stainless family, without 309S’s dedicated high-temperature composition.
View SS 304 Guide →Incoloy 800HT
Our higher-alloy, nickel-iron-chromium option for sustained temperatures beyond stainless steel’s practical range.
View Incoloy 800HT →Inconel Family
Our nickel-chromium superalloy family for the most demanding high-temperature and corrosion needs.
View Inconel Guide →Stainless Steel Fasteners Manufacturer India
Our broader stainless steel fastener manufacturing capability across all major grades.
View SS Manufacturer Guide →Sustained High Heat?
We’ll Confirm the Right Grade
Tell us your actual sustained service temperature — we’ll confirm whether 309S genuinely fits or whether 310S or a nickel alloy is the better call, and quote with full documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in