# UNS S32100 (Type 321) Stainless Steel Forgings

**UNS S32100 is Type 321 stainless steel, a titanium-stabilised austenitic grade with 17 to 19 percent chromium and 9 to 12 percent nickel. In forged form it is ordered as ASTM A182 Grade F321.**

Titanium is added at not less than five times the carbon content. It forms titanium carbide in preference to chromium carbide, so chromium stays dissolved in the matrix instead of precipitating at grain boundaries. This is why Type 321 resists intergranular corrosion after exposure to roughly 427 to 816 C (800 to 1500 F), where unstabilised grades such as 304 are attacked. General corrosion resistance is comparable to 304.

Supplied by Jiangyin Jiangnan Metal Co., Ltd., an integrated melting works and open-die forge at Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, operating since 1997.

Source page: https://www.steelforgepieces.com/Stainless-Steel/UNS-S32100.html

## Grade identification

| Field | Value |
|---|---|
| UNS number | S32100 |
| AISI type | 321 |
| Forging specification | ASTM A182 / A182M Grade F321 |
| EN material number | 1.4541 (X6CrNiTi18-10) |
| BS | 321S31, 321S51 |
| JIS | SUS 321 |
| AMS, bar and forging | AMS 5510, AMS 5645 |
| Higher-carbon variant | 321H, UNS S32109, EN 1.4878 |
| Stabilising element | Titanium, 5 x C minimum to 0.70 percent maximum |
| Delivery condition | Solution annealed 1020 to 1100 C, water quenched |

## UNS S32100 is not AISI 310H

These are two different alloys and must not be substituted. UNS S32100 is Type 321, titanium-stabilised 18Cr-10Ni. AISI 310H is UNS S31009, a high-carbon 25Cr-20Ni heat-resistant grade for sustained load service above roughly 650 C. They differ in chromium, nickel, carbon, strengthening mechanism and service temperature. The two are frequently paired in online grade tables, which is an error.

## Chemical composition, ASTM A182 F321

| Element | Symbol | Weight percent |
|---|---|---|
| Carbon | C | 0.08 max |
| Manganese | Mn | 2.00 max |
| Phosphorus | P | 0.045 max |
| Sulfur | S | 0.030 max |
| Silicon | Si | 1.00 max |
| Chromium | Cr | 17.00 to 19.00 |
| Nickel | Ni | 9.00 to 12.00 |
| Titanium | Ti | 5 x C min, 0.70 max |
| Iron | Fe | Balance |

The 0.70 percent titanium ceiling matters as much as the minimum, because excess titanium forms coarse inclusions that spoil surface finish and machinability. Some editions and readings of A182 set the F321 titanium minimum as 5 x (C + N) rather than against carbon alone; state the basis on the enquiry if the distinction affects your design margin. For F321H the titanium minimum is commonly 4 x C.

Note that A182 forgings allow 1.00 percent silicon maximum while A240 plate is usually held to 0.75 percent maximum. Comparing a forging certificate against a plate data sheet causes avoidable rejections.

## Mechanical properties

Required room-temperature minimums, ASTM A182 Grade F321, solution annealed:

| Property | Imperial | Metric |
|---|---|---|
| Tensile strength | 75 ksi | 515 MPa |
| Yield strength, 0.2 percent offset | 30 ksi | 205 MPa |
| Elongation in 2 in. or 4D | 30 percent | 30 percent |
| Reduction of area | 50 percent | 50 percent |
| Reduction of area, transverse | 45 percent | 45 percent |

These are acceptance minimums, not expected results. Properly solution-annealed material normally tests well above them.

Indicative short-term tensile properties against temperature. These are published typical values, not acceptance values, and they describe nothing about creep or stress rupture:

| Temperature, F | Temperature, C | Tensile, ksi | 0.2 percent yield, ksi |
|---|---|---|---|
| 68 | 20 | 84 | 38 |
| 400 | 204 | 62 | 20.5 |
| 600 | 316 | 62 | 18 |
| 800 | 427 | 62 | 17 |
| 1000 | 538 | 59.5 | 16.5 |
| 1200 | 649 | 45.5 | 16 |
| 1400 | 760 | 27.5 | 14 |

For sustained load above roughly 540 C, design to the creep and rupture allowables in the governing code and consider whether 321H is the correct specification. Where the duty is genuinely 25Cr-20Ni oxidation and creep service, the right grade is 310H.

## Physical properties

| Property | Typical value |
|---|---|
| Density | About 7.9 g/cm3, reported range 7.85 to 8.05 |
| Thermal conductivity | About 14 to 17 W/m.K near ambient, about 16.3 at 100 C |
| Melting range | About 1371 to 1400 C |
| Electrical resistivity | About 72 micro-ohm.cm |
| Magnetic response | Non-magnetic solution annealed, slightly magnetic after cold work |

## Why the grade is stabilised

Hold an unstabilised austenitic stainless steel in the band from about 427 to 816 C, or cool it slowly through that band, and carbon migrates to grain boundaries and combines with chromium. The zones beside those carbides end up short of chromium, lose their passive film and become a path for intergranular attack. This is sensitisation, and it appears in anything welded, stress relieved or run hot.

Titanium has a far stronger affinity for carbon than chromium does, so the titanium addition ties carbon up as stable titanium carbide during heat treatment and leaves chromium available for corrosion protection.

In forgings the benefit applies twice. Heavy open-die sections and large rolled rings cool slowly from forging temperature and spend real time in the sensitisation band before reaching service, so stabilisation makes the grade far more forgiving in thick sections than 304 or 304L. Titanium carbides are stable at forging temperature and do not dissolve and re-precipitate the way chromium carbides do, so grain boundary chemistry stays predictable through the forging sequence.

## Production route

Steel is melted and refined on site, forged or ring rolled, heat treated, machined and tested without leaving the plant, so chemistry can be aimed at the forging it will become rather than accepted as delivered, and the certificate traces a part back to its melt number.

| Stage | Equipment |
|---|---|
| Melting | Electric arc furnace, ladle furnace, vacuum oxygen decarburisation. 60 t maximum heat. Electroslag remelting available |
| Forging | Hydraulic open-die presses 6,300 t, 4,000 t, 2,000 t. Hammers 750 kg to 5 t |
| Ring rolling | Radial-axial mills 6 m, 3 m, 1 m |
| Heat treatment | 14 furnaces. Solution annealed 1020 to 1100 C, water quenched. Pit furnaces 15,000 mm deep for vertical quenching |
| Machining | Vertical lathes to 5,000 mm swing, horizontal lathes to 14,000 mm, CNC to 2,000 x 10,000 mm, deep-hole drilling to 1,600 x 10,000 mm |
| Inspection | Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 |
| Certification | EN 10204 type 3.1, or type 3.2 with third-party endorsement |
| Approvals | CCS, BV, DNV, LR, NK |

Rapid cooling from solution temperature decides whether this grade performs. A sluggish quench on a heavy section defeats the reason for buying a stabilised steel, so quench arrangements are matched to section thickness. If the application needs a stabilising anneal in addition to solution annealing, which is usual for severe polythionic acid or hot caustic service, state it on the enquiry.

## Size envelope

| Product | Limit | Set by |
|---|---|---|
| Seamless rolled rings | to OD 6,000 mm | 6 m radial-axial ring mill |
| Small rings | from OD 50 mm | Upset-and-punch route |
| Forged shafts | to 14,000 mm turned length | Horizontal lathe, 15 m pit furnace |
| Discs, tube sheets, blocks | to 5,000 mm machined diameter | 5,000 mm vertical lathe |
| Bored cylinders, hollow shafts | to 1,600 mm dia x 10,000 mm | CNC deep-hole drilling machine |
| Single piece weight | to 30,000 kg | 60 t heat, 6,300 t press |
| Minimum order | 10 kg, no minimum piece count | Commercial |
| Lead time | 20 to 60 days | Size, heat treatment, machining |

## Product forms

Seamless rolled rings, contoured rolled rings, forged rings, retaining rings, valve seat rings, gear and bearing blanks, slewing rings. Weld neck, blind, slip-on, socket weld, lap joint, orifice and long weld neck flanges, hubs and nozzles. Round, flat and square bars, stepped shafts, gear and pinion shafts, eccentric shafts, crankshafts, spindles, tie rods. Solid forged discs, tube sheets, covers, closure heads, die and mould blocks. Forged cylinders, sleeves, bushings, couplings, heavy-wall pipe sections bored from solid. Valve bodies, bonnets, stems, blocks, spools, manifolds, gears, rolls and wheels.

Every item is forged from a single piece of steel melted on site, with no welding and no purchased billet of unknown origin.

## Applications

| Industry | Components and service |
|---|---|
| Petroleum refining | Flanges, shafts, rings and pipe components in polythionic acid service |
| Chemical processing | Expansion joint parts, nozzles, reactor and vessel components, thermal oxidiser internals |
| Pulp and paper | Digester components, liquor tank parts, machine rolls and shafts, exchanger parts |
| Oil and gas, offshore | Tube sheets, flanges and shafts for subsea and deepwater systems, compressor parts |
| Power and rotating equipment | Turbine and compressor rings, gearbox gears, spindles, transmission bars |
| Aerospace | Piston engine manifolds and exhaust components under cyclic heating |
| Valves | Bodies, stems, seat rings and blocks for ball, gate, globe, check and plug valves |
| Food and pharmaceutical | Processing and storage equipment, vessel and agitator components |
| Shipbuilding and heavy machinery | Forged wheels, rolls, manifolds, structural forgings |

Stabilisation fixes sensitisation, not chloride pitting. Type 321 carries no molybdenum, so its pitting resistance is much the same as 304. In warm chloride, brackish or seawater service choose a higher alloy such as A182 F51, F55, F44, 904L or Incoloy 825.

## Grade selection

| Grade | UNS | Stabiliser | Carbon | Specified when |
|---|---|---|---|---|
| 321 | S32100 | Titanium, 5 x C min | 0.08 max | 304-level corrosion resistance is enough but the part is welded or runs at 427 to 816 C |
| 304 | S30400 | None | 0.08 max | General service, no sustained exposure to the sensitisation range |
| 321H | S32109 | Titanium, 4 x C min | 0.04 to 0.10 | Creep and stress-rupture strength needed for long-term hot service |
| 347 | S34700 | Niobium | 0.08 max | Stabilised behaviour wanted but titanium unwelcome |
| 310H | S31009 | None, 25Cr-20Ni | 0.04 to 0.10 | Oxidation resistance and creep strength above roughly 650 C. Different alloy class |

The 321 against 347 choice usually comes down to fabrication preference and to whatever the end user specification already names. The 321 against 321H choice comes down to whether the code case needs creep allowables.

## Questions and answers

**What is UNS S32100?**
The Unified Numbering System designation for Type 321 stainless steel, a titanium-stabilised austenitic grade with 17 to 19 percent chromium and 9 to 12 percent nickel. Forgings are ordered as ASTM A182 Grade F321.

**Is UNS S32100 the same as AISI 310H?**
No. UNS S32100 is Type 321, titanium-stabilised 18Cr-10Ni. AISI 310H is UNS S31009, a high-carbon 25Cr-20Ni heat-resistant grade. They are not interchangeable.

**What is the difference between 321 and 321H?**
Carbon content. 321 is 0.08 percent maximum; 321H is held to a controlled 0.04 to 0.10 percent range for higher creep and stress-rupture strength.

**What are the minimum mechanical properties of A182 F321 forgings?**
515 MPa (75 ksi) tensile, 205 MPa (30 ksi) yield at 0.2 percent offset, 30 percent elongation, 50 percent reduction of area.

**How is it heat treated after forging?**
Solution annealed at 1020 to 1100 C and water quenched. Rapid cooling through the sensitisation range is essential.

**What are the European and Japanese equivalents?**
EN 1.4541 (X6CrNiTi18-10) and JIS SUS 321. Also BS 321S31 and AMS 5510 / AMS 5645.

**Does 321 resist chloride pitting better than 304?**
No. Stabilisation addresses sensitisation, not pitting. Type 321 has no molybdenum, so pitting resistance is comparable to 304.

**What testing and certification is available?**
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Certificates to EN 10204 type 3.1 or 3.2. The works holds CCS, BV, DNV, LR and NK approvals.

## Contact

| Field | Detail |
|---|---|
| Company | Jiangyin Jiangnan Metal Co., Ltd. |
| Business | Integrated melting works, open-die forge, ring rolling mill |
| Established | 1997 |
| Plant | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone | +86 189 2135 9659 |
| Email | sales@steelforgepieces.com |

Send the drawing or finished size, the governing specification, quantity and test requirements for a quotation.

Composition and mechanical minimums are quoted from ASTM A182 / A182M Grade F321. Elevated-temperature and physical values are published typical data for guidance. The specification on the purchase order and the certificate for the heat supplied take precedence. Last reviewed 2026-10-07.