Stainless Steel Forgings / Austenitic / High Carbon
UNS S31609 Forgings 316H rolled rings, flanges, bars, discs and shafts to ASTM A182 Grade F316H
UNS S31609 is type 316 with carbon deliberately held between 0.04 and 0.10 percent. The usual name for it is 316H, and ASTM A182 calls the forging grade F316H. The carbon minimum is the point of the grade: carbide at the grain boundaries resists creep, which is why ASME Section II Part D carries allowable stresses for 316H to roughly 816 °C while 316L stops at 427 °C.
Room-temperature minimums are unchanged from plain 316 at 515 MPa tensile and 205 MPa yield. Buying S31609 for a 200 °C service gains nothing and costs more. It earns its price above about 425 °C.
- UNS
- S31609
- Also called
- 316H, SS 316H, 1.4919
- Forging spec
- ASTM A182 / A182M Grade F316H
- Other forms
- A240 plate, A312 TP316H pipe, A213 TP316H tube, A403 WP316H fittings, A479 bar
- Carbon
- 0.04 – 0.10 % (minimum specified)
- Tensile, min
- 515 MPa / 75 ksi
- Yield, min
- 205 MPa / 30 ksi
- Anneal
- 1040 – 1120 °C, rapid cool
- Code limit
- ASME II-D listed to approx. 816 °C
- Max ring OD
- 6,000 mm on the 6 m ring mill
- Max piece
- 30,000 kg
Product forms in S31609
Everything below is forged from steel melted in our own furnaces, so the certificate traces back to a heat number rather than to a purchased billet. We work to your drawing, in the as-forged, proof-machined or finish-machined condition.
| Form | Size envelope | Where it goes | Standards |
|---|---|---|---|
| Seamless rolled rings | OD 50 – 6,000 mm | Exchanger shell courses, tower and vessel rings, gear ring and slewing ring blanks | A182 F316H, A965 |
| Forged rings, retaining and seat rings | to 30 t single piece | Sections outside the ring-mill envelope, heavy-reduction work | A182 F316H |
| Flanges: weld neck, blind, slip-on, socket weld, lap joint, orifice, long weld neck | to 5,000 mm machined dia | Creep-range steam and process piping | A182 F316H; ASME B16.5, B16.47; MSS SP-44 |
| Round bars, shafts, spindles, eccentric shafts | to 14,000 mm turned length | Turbine and compressor rotors, gearbox and press components | A182 F316H, A479 |
| Discs, tube sheets, covers, blocks | to 5,000 mm machined dia | Exchangers and pressure vessels, supplied proof-machined for volumetric inspection | A182 F316H |
| Bored cylinders, sleeves, bushings, forged pipe | to 1,600 mm dia × 10,000 mm | Hollow sections bored from solid forged blanks | A182 F316H |
| Valve and wellhead parts: bodies, bonnets, stems, seat rings, nozzles, manifolds | from 10 kg | Ball, gate, globe, check and plug valves; Christmas trees, wellheads, risers | A182 F316H; API 6A; NACE MR0175 / ISO 15156 on request |
| Minimum order 10 kg with no minimum piece count. Lead time 20 to 60 days depending on section and heat-treatment route. | |||
Chemical composition
Forging and plate limits are the same except for silicon, which A240 holds tighter. Order against A182 for forgings and do not accept a plate certificate in its place.
| Element | A182 F316H forgings | A240 plate | What it does here |
|---|---|---|---|
| Carbon | 0.04 – 0.10 | 0.04 – 0.10 | Grain-boundary carbide, which is what raises creep-rupture strength |
| Chromium | 16.0 – 18.0 | 16.0 – 18.0 | Passive film and oxidation resistance |
| Nickel | 10.0 – 14.0 | 10.0 – 14.0 | Holds the austenite stable, keeps hot ductility |
| Molybdenum | 2.00 – 3.00 | 2.00 – 3.00 | Pitting resistance, and hot corrosion in sulphur-bearing gas |
| Manganese | 2.00 max | 2.00 max | Austenite stabiliser, deoxidation |
| Silicon | 1.00 max | 0.75 max | Oxidation resistance |
| Phosphorus | 0.045 max | 0.045 max | Residual, held down for weldability |
| Sulphur | 0.030 max | 0.030 max | Residual, lower sulphur gives better forged surface |
| Iron | Balance | Balance | Matrix |
Check the carbon figure on the certificate before you accept the material. A heat reporting 0.025 percent carbon is 316 or 316L with an F316H heading on the paperwork, and it will not hold the creep strength the design assumed. Above 0.10 percent the sensitisation risk in the weld heat-affected zone climbs instead. We report carbon per heat and will send the analysis before forging starts.
Mechanical properties
| Property | A182 F316H forgings | A240 plate, for comparison |
|---|---|---|
| Tensile strength, min | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield strength, 0.2 % offset, min | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Elongation, 50 mm or 4D, min | 30 % | 40 % |
| Reduction of area, min | 50 % | not specified |
| Modulus of elasticity | approx. 193 GPa | |
| Magnetic response, annealed | Essentially non-magnetic | |
| The elongation difference is a common source of rejected paperwork. Forgings are tested to 30 percent, not the 40 percent figure quoted on plate data sheets. | ||
Creep-rupture strength, 100,000 hours
These are typical published ranges for 316H-type material, not specification minimums, and they move with carbon and nitrogen in the individual heat. Design against the allowable stress tables in the ASME edition your code work references, not against this table.
| Temperature | 316 / 316L type | 316H | Gain |
|---|---|---|---|
| 500 °C | 95 – 110 MPa | 115 – 130 MPa | approx. 20 % |
| 600 °C | 45 – 55 MPa | 60 – 72 MPa | approx. 30 % |
| 650 °C | 30 – 38 MPa | 40 – 50 MPa | approx. 33 % |
Melting, heat treatment, machining, welding
Melting route
S31609 runs through the electric arc furnace, a ladle furnace for desulphurisation and alloy trim, then vacuum oxygen decarburisation where carbon and nitrogen need tight control. That last step matters for an H grade, because carbon has to land inside a 0.06 percent window rather than simply below a ceiling. Maximum heat size is 60 tonnes. Electroslag remelting is available when the specification calls for a remelted ingot.
Solution annealing
Supplied solution annealed at 1040 to 1120 °C, water quenched or force cooled. Slow cooling through 425 to 870 °C precipitates chromium carbide at the grain boundaries and leaves the adjacent metal chromium-poor, so the cooling rate is controlled rather than left to the furnace. Fourteen heat-treatment furnaces are on site, including car-bottom chambers to 8,000 mm long and two pit furnaces 15,000 mm deep for vertical quenching of long shafts.
Machining
S31609 work-hardens quickly and tears rather than chips cleanly, which puts it well below martensitic 410 for machinability and roughly level with 304. Rigid setups, positive rake, sharp inserts, heavy constant feed and plenty of coolant. Dwelling glazes the cut and kills the tool. We can supply proof-machined or finish-machined if you would rather not fight it.
Welding
Match the carbon with ER316H or E316H filler to AWS A5.9 and A5.4. Substituting 316L filler in a creep-loaded joint puts the weakest metal where the stress is. No preheat needed, keep interpass temperature and heat input down, and post-weld heat treatment is not normally required. The failure mode seen in service is intergranular creep cracking in the heat-affected zone of thick weldments, not pitting.
Temperature range and grade selection
| Range | Behaviour |
|---|---|
| to −196 °C | Austenite keeps its toughness, so the grade is usable cryogenically, though that is not what it was developed for. |
| ambient – 425 °C | No strength advantage over 316 or 316L. For welded corrosive service in this range, 316L is cheaper and resists sensitisation better. |
| 425 – 540 °C | Creep begins to govern. 316L loses its ASME listing at 427 °C; S31609 remains code-usable. |
| 540 – 700 °C | The band the grade exists for. Creep controls the design and long-term ageing brings out carbide and sigma-phase precipitates. |
| 700 – 816 °C | Upper end of pressure-retaining design. Oxidation becomes a co-limiting factor alongside creep. |
| above 870 °C | Oxidation-limited. Move to 310S, 253 MA or a nickel-base alloy. |
Neighbouring grades
| Grade | Carbon | Pick it when |
|---|---|---|
| 316L, S31603 | 0.030 max | Service stays under 427 °C and weld corrosion resistance matters more than creep strength. |
| 316, S31600 | 0.080 max | General corrosion duty with no sustained load in the creep range. |
| 316Ti, S31635 | 0.080 max, Ti-stabilised | Welded assemblies held statically at 400 to 900 °C where intergranular attack is the main risk. Creep strength is lower than 316H, so it is not a substitute for a stressed part. |
| 304H, S30409 | 0.04 – 0.10 | Dry oxidising heat with no chlorides and no sulphur. Cheaper, but it has no molybdenum. |
| 347H, S34709 | 0.04 – 0.10 | Creep service that also needs niobium stabilisation against sensitisation. |
| S31609, 316H | 0.04 – 0.10 | Sustained stress above roughly 425 °C in an atmosphere carrying chlorides, sulphur compounds or process acids. |
Where these forgings end up
In fossil power, S31609 goes into superheater and reheater components, steam headers and main steam piping. Refineries use it for hydroprocessing reactor internals, reformer and furnace parts, transfer lines and services exposed to polythionic acid. Chemical plants take it for sulphuric acid plant components and hot process piping.
Waste-to-energy plants use it on heat recovery surfaces and flue gas ducting. Concentrated solar plants use it for molten nitrate salt receivers, hot salt tanks and the piping between them. Oil and gas work covers hot manifolds, wellhead and Christmas tree components and subsea production hardware. Nuclear, pulp and paper, pharmaceutical, rubber, plastics and textile plants order it as exchangers, condensers, evaporators, columns, towers, silos, preheaters and recuperators.
Inspection and certification
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, whichever the order specifies. Certificates to EN 10204 3.1, or 3.2 with third-party endorsement from CCS, BV, DNV, LR or NK, all of which approve this works. Added on request: positive material identification, grain size to ASTM E112, intergranular corrosion testing to ASTM A262 Practice E, impact testing, hardness survey and a dimensional report.
Questions we get asked
Is UNS S31609 the same thing as 316H?
Yes. S31609 is the Unified Numbering System code for 316H. The same metal appears as Grade F316H in ASTM A182 forgings, UNS S31609 in A240 plate, TP316H in A312 pipe and A213 tube, WP316H in A403 fittings, and EN 1.4919 in European numbering.
What separates S31609 from S31600?
Carbon, and nothing else of consequence. S31600 caps carbon near 0.08 percent with no floor; S31609 specifies a 0.04 to 0.10 percent band. Chromium, nickel and molybdenum ranges match, and so do the room-temperature strength minimums. The carbon floor is what buys creep strength above about 500 °C.
Is 1.4401 the European equivalent?
No, and this mix-up shows up on supplier data sheets regularly. EN 1.4401 is X5CrNiMo17-12-2, which is plain 316 with carbon capped at 0.08 percent and no minimum. The number that carries the high-carbon requirement is 1.4919. A certificate headed "316H / 1.4401" contradicts itself.
How hot can S31609 run?
For pressure-retaining design, about 816 °C, which is where ASME Section II Part D stops listing an allowable stress for the grade. Unloaded oxidation-limited parts can see roughly 870 °C. Above that the grade is the wrong choice and 310S or a nickel alloy should be used.
What heat treatment comes with the forging?
Solution anneal at 1040 to 1120 °C followed by rapid cooling. The thing to avoid is any hold or slow cool through 425 to 870 °C, which sensitises the steel by dropping chromium carbide onto the grain boundaries.
Will it survive seawater?
No. With 2 to 3 percent molybdenum its PREN sits around 24 to 27, better than 304H near 18 to 20, but short of what seawater needs whether flowing or stagnant. Specify super duplex such as S32750 or S32760, or a 6 percent molybdenum grade, for those duties.
What sizes can you forge, and what is the minimum order?
Rolled rings to 6,000 mm outside diameter on the 6 m radial-axial mill, single pieces to 30 tonnes under the 6,300 t press, shafts to 14,000 mm turned length, discs and tube sheets to 5,000 mm machined diameter, and bored sections to 1,600 mm diameter by 10,000 mm. Minimum order is 10 kg with no minimum piece count.
How is S31609 priced?
Per piece against your drawing, not per kilogram off a list. The figure depends on finished weight, the input billet weight after forging allowance, section thickness, the heat-treatment route, how much machining we carry out and which NDT and certification you need. Nickel and molybdenum surcharges also move with the alloy market, so a published price would be wrong within weeks. Send the drawing and we will quote.
Who forges this, and what does the works actually run?
Jiangyin Jiangnan Metal Co., Ltd., at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province 214423, China, working since 1997 with 460 staff including 9 senior and 32 intermediate engineers. Steel is melted on site through EAF, LF, VOD, VIM, VAR and ESR routes up to 60 tonne heats, then forged on a 6,300 t press and three ring mills, heat treated in 14 furnaces and machined in-house. Approvals are held from CCS, BV, DNV, LR and NK. Reach us at sales@steelforgepieces.com or +86 189 2135 9659.
Quote a S31609 forging
Send the drawing, or just the rough dimensions and quantity. Useful to include: applicable standard, heat-treatment condition, NDT requirement and certificate type. We will come back with feasibility, weight and price.
Jiangyin Jiangnan Metal Co., Ltd. · No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province 214423, China
Related stainless grades
- A182 F316
- A182 F316L
- A182 F321
- AISI 321H
- AISI 347H
- A182 F347
- A182 F44
- 904L
- A182 F51
- A182 F53
- A182 F55
- Nitronic 50
- All stainless grades
Data compiled from ASTM A182/A182M, ASTM A240 and ASME Boiler and Pressure Vessel Code Section II Part D. Creep figures are indicative and not specification minimums; confirm against the certified mill test report and the code edition governing your design. Reviewed 5 October 2026 by the technical department, Jiangyin Jiangnan Metal Co., Ltd.