UNS S30900 is the UNS designation for AISI Type 309, a heat-resistant austenitic stainless steel with 22.0 to 24.0 percent chromium, 12.0 to 15.0 percent nickel and up to 0.20 percent carbon, balance iron. The high chromium gives superior oxidation resistance and better retention of room-temperature strength at elevated temperature than Alloy 304, with service to 1038 C (1900 F) under non-cyclic oxidising conditions. It is a high-temperature grade, not a wet-corrosion grade. Forgings are covered by ASTM A473. The related pressure-part grade in ASTM A182 is F309H (UNS S30909).
Jiangyin Jiangnan Metal Co., Ltd. manufactures UNS S30900 open-die forgings and seamless rolled rings to customer drawing: forged rings, rolled rings, flanges, round bars, discs, sleeves, bushings, tube sheets, shafts and forged hollows. Melting routes include EAF plus VOD, with ESR remelt where the application calls for improved cleanliness and tighter segregation control.
Which standard applies to UNS S30900 forgings
ASTM A473, Standard Specification for Stainless Steel Forgings, covers austenitic, austenitic-ferritic, ferritic and martensitic stainless steel forgings for general use and for low- or high-temperature service. Its grade table lists UNS S30900 as Type 309, so A473 is the correct base specification for general S30900 forgings.
Specification note. ASTM A182 and ASME SA-182 do not contain UNS S30900. The 309-family grade in A182 is F309H, UNS S30909, a carbon-controlled 0.04 to 0.10 percent C modification intended for high-temperature pressure-boundary parts such as flanges, fittings and valve bodies. If your line class or ASME B16.5 flange order calls for A182 309, the grade you need is almost certainly F309H rather than S30900. We supply either, so please state which on the enquiry and the certificate will match your specification.
| Grade | UNS | Carbon, % | Typical product specification | Purpose of the variant |
|---|---|---|---|---|
| 309 | S30900 | 0.20 max | ASTM A473 forgings, ASTM A240 / ASME SA-240 plate, AMS 5523 | Base heat-resistant grade |
| 309S | S30908 | 0.08 max | ASTM A473, ASTM A240 / SA-240 | Low carbon for easier fabrication and less carbide precipitation on welding |
| 309H | S30909 | 0.04 to 0.10 | ASTM A182 F309H forged pressure parts, ASTM A240 | Carbon controlled for enhanced creep resistance |
Chemical composition of UNS S30900
Weight percent. All figures are maximum unless a range is shown.
| Element | 309, S30900 | 309S, S30908 | 309H, S30909 (A182 F309H) |
|---|---|---|---|
| Carbon, C | 0.20 max | 0.08 max | 0.04 to 0.10 |
| Chromium, Cr | 22.0 to 24.0 | 22.0 to 24.0 | 22.0 to 24.0 |
| Nickel, Ni | 12.0 to 15.0 | 12.0 to 15.0 | 12.0 to 15.0 |
| Manganese, Mn | 2.00 max | 2.00 max | 2.00 max |
| Silicon, Si | 0.75 max under A240, 1.00 max under A182 F309H | 0.75 max | 1.00 max |
| Phosphorus, P | 0.045 max | 0.045 max | 0.045 max |
| Sulfur, S | 0.030 max | 0.030 max | 0.030 max |
| Iron, Fe | Balance | Balance | Balance |
The silicon limit differs between standards. ASTM A240 Type 309 restricts silicon to 0.75 percent maximum, while ASTM A182 F309H permits 1.00 percent maximum. Confirm which limit your purchase specification invokes before the heat is fixed.
Mechanical properties
Two sets of figures matter when ordering forgings. The specified minimums are what appears on the mill certificate and what the material is accepted against. The typical values are representative annealed results and should not be used as design allowables.
| Property | ASTM A240 Type 309, min | ASTM A182 F309H, min | Typical annealed |
|---|---|---|---|
| Tensile strength | 75 ksi (515 MPa) | 75 ksi (515 MPa) | 85,000 psi (586 MPa) |
| Yield strength, 0.2 % offset | 30 ksi (205 MPa) | 30 ksi (205 MPa) | 45,000 psi (310 MPa) |
| Elongation in 2 in. (50 mm) | 40 % | 30 % | 50 % |
| Reduction of area | Not specified | 50 % | Not applicable |
| Hardness | Not specified | Not specified | 202 HBN max |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.89 g/cm3 | 0.285 lb/in3 |
| Modulus of elasticity | 193 GPa | 28.5 x 10^6 psi |
| Melting range | 1480 to 1530 C | 2500 to 2590 F |
| Specific heat 0 to 100 C | 502 J/kg.K | 0.12 BTU/lb.F at 32 to 212 F |
| Thermal conductivity at 100 C | 15.6 W/m.K | 9.0 BTU/hr/ft2/ft/F at 212 F |
| Electrical resistivity at 20 C | 78 micro-ohm.cm | 30.7 micro-ohm.in |
High-temperature performance and service limits
Alloy 309 resists oxidation to 1900 F (1038 C) under non-cyclic conditions. Frequent thermal cycling reduces that oxidation resistance to roughly 1850 F (1010 C). Because of the high chromium and comparatively low nickel, the grade performs well in sulfur-bearing atmospheres up to 1832 F (1000 C).
| Atmosphere | Limit, C | Limit, F |
|---|---|---|
| Oxidising, sulfur up to 2 g/m3, continuous service | 1050 | 1922 |
| Oxidising, sulfur up to 2 g/m3, peak temperature | 1100 | 2012 |
| Oxidising, sulfur above 2 g/m3, maximum | 950 | 1742 |
| Low-oxygen atmosphere, sulfur up to 2 g/m3 | 1000 | 1832 |
| Nitriding or carburising atmospheres | 850 to 950 | 1562 to 1742 |
The grade is not recommended for highly carburising atmospheres, where it shows only moderate resistance to carbon absorption. It does not match Alloy 600 (UNS N06600) or Alloy 800 (UNS N08800) in reducing, nitriding or carburising service, but it outperforms most other heat-resistant stainless steels in those conditions.
Sigma phase
Held between 1202 and 1742 F (650 to 950 C), Alloy 309 is subject to sigma phase precipitation, which embrittles the material. A solution anneal at 2012 to 2102 F (1100 to 1150 C) restores a degree of toughness. For this reason the forging sequence, soak time and post-forge heat treatment are specified on every S30900 job we run, and cold forming of parts destined for long-term high-temperature exposure is not recommended.
Typical creep data
| Temperature | Creep strain, MPa | Creep rupture, MPa | ||||
|---|---|---|---|---|---|---|
| 1,000 h | 10,000 h | 100,000 h | 1,000 h | 10,000 h | 100,000 h | |
| 600 C / 1112 F | 120 | 80 | 40 | 190 | 120 | 65 |
| 700 C / 1292 F | 50 | 25 | 20 | 75 | 36 | 16 |
| 800 C / 1472 F | 20 | 10 | 8 | 35 | 18 | 7.5 |
| 900 C / 1652 F | 8 | 4 | 3 | 15 | 8.5 | 3 |
| 1000 C / 1832 F | 4 | 2.5 | 1.5 | 8 | 4 | 1.5 |
Corrosion behaviour and limits
Alloy 309 is not designed for service in wet corrosive environments. The high carbon content that benefits creep properties has a detrimental effect on aqueous corrosion resistance, and the grade is prone to intergranular corrosion after long-term exposure at high temperature. Its 23 percent chromium does make it more corrosion-resistant than most heat-resistant alloys, but that comparison is within the heat-resistant family and is not a basis for using it in chloride, seawater or acid service.
For wet, chloride-bearing or acidic duty, specify a different grade and we will forge it from the same shop.
A182 F51, Duplex 2205
Chloride-bearing process and seawater-adjacent service with high strength.
International equivalents and cross-reference
| System | Designation | Note |
|---|---|---|
| UNS | S30900 | Type 309 base grade |
| AISI and ASTM type | 309 | Also 309S as S30908 and 309H as S30909 |
| EN steel name | X12CrNi23-13 | Austenitic heat-resisting steel, EN 10095 |
| EN material number | 1.4833 | Corresponds most closely to 309S, not to the higher-carbon 309 |
| JIS | SUS 309 and SUS 309S | Japanese equivalents of the 309 pair |
| Fittings designation | ASTM WP309 | Wrought fittings |
Where a drawing calls for 1.4833 and the purchase order says 309, the two are not strictly interchangeable on carbon, because 1.4833 sits in the 309S carbon range. Tell us which certificate the end client will audit against and we will melt to the tighter of the two.
Forging, heat treatment and fabrication data
Hot working
Heat uniformly to 1742 to 2192 F (950 to 1200 C). After hot forming, a final anneal at 1832 to 2101 F (1000 to 1150 C) followed by rapid quenching is recommended. This is standard on every S30900 forging leaving our shop unless the customer specifies otherwise.
Cold forming
The grade is quite ductile and forms in a manner close to 316. Cold forming of pieces destined for long-term high-temperature exposure is not recommended because of susceptibility to carbide and sigma phase precipitation.
Welding
Alloy 309 is readily welded by most standard processes including TIG, plasma, MIG, SMAW, SAW and FCAW. Where the best post-weld corrosion behaviour is required, the low-carbon 309S variant is preferred to limit carbide precipitation.
Manufacturing route
Melting
EAF plus VOD, with ESR remelt available where cleanliness, ingot soundness and reduced segregation are critical.
Open-die forging
Upsetting, drawing out and punching to develop a worked, directional grain flow instead of a cut-from-plate structure.
Ring rolling
Seamless rolled rings with circumferential grain flow for hoop-loaded parts.
Heat treatment
Solution anneal at 1100 to 1150 C with rapid quench to dissolve carbides and sigma phase.
Machining
Rough or finish machining to drawing, including proof-machined rings and discs.
Inspection
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 as specified, plus PMI, chemistry and mechanical testing.
UNS S30900 product forms
| Form | Typical use in this grade |
|---|---|
| Forged rings and seamless rolled rings | Furnace retaining rings, kiln and calciner rings, burner mounting rings |
| Forged flanges | High-temperature piping and recuperator connections, with A182 F309H specified for pressure-boundary duty |
| Forged round bars and billets | Machined furnace hardware, hangers, fasteners, pins |
| Forged discs and blanks | Fan hubs, damper plates, cover plates for thermal processing equipment |
| Forged bushings and sleeves | Hot-zone bushings, roller sleeves, walking-beam components |
| Forged tube sheets | Recuperator and heat exchanger tube sheets in hot gas service |
| Forged shafts and spindles | Furnace fan shafts, kiln drive components |
| Forged hollows and pipe blanks | Machined piping spools and nozzle bodies for hot gas duty |
Applications
These are the service areas documented for the grade. Wet-corrosion applications sometimes listed for 309 elsewhere are left out, because the grade is not suited to them.
Furnaces
Burners, doors, fans, piping and recuperators.
Fluidised bed furnaces
Grids, piping and wind boxes.
Thermal processing
Annealing covers and boxes, burner grids, doors, fans, lead pans, neutral salt pots, muffles, retorts, recuperators and walking beams.
Petroleum refining
Catalytic recovery systems and recuperators.
Power generation
Pulverised coal burners and tube hangers.
Waste treatment
Incinerators, rotary kilns and calciners.
Paper mill equipment
High-temperature mill components.
Testing, documentation and certification
Ultrasonic testing is performed to the standard nominated on the order, EN 10228-3, SEP 1921 or ASTM A388. Material certificates are issued to EN 10204 3.1, or to EN 10204 3.2 with third-party witness such as TUV, BV, DNV, SGS or Lloyds where required. Chemical analysis, tensile testing, hardness, grain size and positive material identification are reported on the certificate, and supplementary requirements from ASTM A473 can be invoked on request.
Frequently asked questions
What is UNS S30900?
UNS S30900 is the Unified Numbering System designation for AISI Type 309, a heat-resistant austenitic stainless steel containing 22.0 to 24.0 percent chromium and 12.0 to 15.0 percent nickel with up to 0.20 percent carbon, balance iron. The high chromium and nickel give corrosion resistance comparable to Alloy 304 with superior oxidation resistance and better retention of room-temperature strength at elevated temperature.
Which ASTM standard covers UNS S30900 forgings?
ASTM A473, Standard Specification for Stainless Steel Forgings, lists UNS S30900 as Type 309. ASTM A182 does not include S30900. Its 309-family grade is F309H, UNS S30909, with carbon controlled at 0.04 to 0.10 percent. For plate the governing specifications are ASTM A240, ASME SA-240 and AMS 5523.
What is the maximum service temperature of Alloy 309?
1900 F (1038 C) under non-cyclic oxidising conditions. Frequent thermal cycling reduces this to roughly 1850 F (1010 C). In oxidising conditions with sulfur up to 2 g/m3, continuous service is rated at 1050 C with a peak of 1100 C.
What is the difference between 309, 309S and 309H?
All three carry 22 to 24 percent chromium and 12 to 15 percent nickel and differ in carbon. 309 as S30900 allows up to 0.20 percent carbon. 309S as S30908 is capped at 0.08 percent for easier fabrication and reduced carbide precipitation on welding. 309H as S30909 is controlled at 0.04 to 0.10 percent for enhanced creep resistance. In many cases a single heat satisfies both the 309S and 309H requirements on carbon and grain size.
What is the European equivalent of UNS S30900?
X12CrNi23-13, material number 1.4833, an austenitic heat-resisting steel under EN 10095. Note that 1.4833 aligns most closely with 309S rather than with the higher-carbon 309, so the two are not automatically interchangeable where carbon is a controlled parameter.
Can UNS S30900 be used in seawater, chloride or acid service?
No. Alloy 309 is not designed for wet corrosive environments. The high carbon content is detrimental to aqueous corrosion resistance and the grade is prone to intergranular corrosion after long-term high-temperature exposure. For those duties specify duplex as F51, super duplex as F53 or F55, or a super-austenitic grade such as 904L or F44, all of which we forge.
How is sigma phase embrittlement avoided in 309 forgings?
Avoid prolonged exposure between 1202 and 1742 F (650 to 950 C), which is the sigma phase precipitation range. Where exposure has occurred, a solution anneal at 2012 to 2102 F (1100 to 1150 C) restores a degree of toughness. Our standard route after hot forming is an anneal at 1832 to 2101 F (1000 to 1150 C) followed by rapid quenching.
What is needed to quote a UNS S30900 forging?
A drawing or the finished dimensions, the quantity, the governing specification such as ASTM A473, A182 F309H or EN 1.4833, the certificate level required as EN 10204 3.1 or 3.2, and any NDT requirement such as EN 10228-3 or ASTM A388 with the acceptance class. Send it to sales@steelforgepieces.com or call 0086-189-2135-9659.
Request a UNS S30900 forging quotation
Send a drawing or dimensions and we will return a price, a forging route and a delivery schedule. Mixed-grade enquiries across stainless, nickel alloy, tool steel and alloy steel can go in one RFQ.
Open-Die Forging Factory
Related grades
Technical data last reviewed 5 October 2026. Published by Jiangyin Jiangnan Metal Co., Ltd. Composition, mechanical, physical, creep and temperature data compiled from published ASTM A473, ASTM A240, ASTM A182 and EN 10095 grade data. Figures are for guidance, are not design allowables and are not a warranty of suitability for a particular application. Confirm the governing specification revision with us before ordering.