Chemical composition, ASTM A666 and A240 limits
| Element | Min % | Max % |
|---|---|---|
| Chromium (Cr) | 15.00 | 17.00 |
| Manganese (Mn) | 7.00 | 9.00 |
| Nickel (Ni) | 1.50 | 3.00 |
| Nitrogen (N) | 0.15 | 0.30 |
| Carbon (C) | — | 0.030 |
| Silicon (Si) | — | 1.00 |
| Copper (Cu) | — | 1.00 |
| Phosphorus (P) | — | 0.040 |
| Sulfur (S) | — | 0.030 |
| Iron (Fe) | Balance | |
Melting route for our forging stock is EAF plus VOD, with ESR available on request where tighter cleanliness is required.
Designations and cross-references
| Form or context | Designation |
|---|---|
| UNS number | S20400 |
| Sheet, strip, plate, flat bar | ASTM A666, ASTM A240, ASME SA240 |
| Trade name | Nitronic 30, a Cleveland-Cliffs trademark |
| Weld filler | AWS A5.9 Class ER209 (UNS S20980), also E/ER308L and 309L |
| Common shorthand | Type 204, 204 stainless |
Nitronic is a registered trademark of Cleveland-Cliffs Steel Corp., successor to AK Steel. We supply to the UNS S20400 specification. The trade name appears for identification only and does not imply the material is of that producer's manufacture.
Mechanical properties
Two different sets of figures circulate for this grade, and confusing them is a common cause of dispute at inspection. The first is the specification minimum for annealed material. The second is the typical result annealed product actually achieves, which sits well above the minimum.
| Property | Specification minimum | Typical, annealed |
|---|---|---|
| Ultimate tensile strength | 95 ksi (655 MPa) | 110 ksi (758 MPa) |
| Yield strength, 0.2% offset | 48 ksi (330 MPa) | 55 ksi (379 MPa) |
| Elongation in 2 in. (50 mm) | 35% | 50% |
| Hardness | 241 HBW / 100 HRB max | About 95 HRB |
Typical values come from producer data for annealed flat product. Forged sections are tested to the applicable purchase specification. Test location, direction and section size all affect the result, so please state the test requirement on the drawing or purchase order.
Effect of cold work
S20400 is not hardenable by heat treatment. All strengthening above the annealed condition comes from cold work, and the response is steep. Published data for cold-reduced flat product shows ultimate tensile strength roughly doubling between the annealed condition and 60% reduction, with yield strength climbing from the high 40s ksi into the 180 ksi range as elongation falls from above 50% into single digits. The same deformation forms martensite, so hardness, work-hardening rate and abrasion resistance all rise together. For forged parts this matters mainly in machining allowance and in any post-forge cold sizing or straightening.
Forging, annealing and fabrication
Forging
Heat to about 1093 C (2000 F) and soak to equalise, then raise to about 1176 C (2150 F) and equalise before forging. Hot working is generally carried out in the 1175 to 1200 C range.
Annealing
Soak at 1038 to 1121 C (1900 to 2050 F), then quench rapidly in water or air.
Stress relief
Where only fabrication or machining stresses need relaxing, heating in the 500 to 600 C (932 to 1112 F) range with controlled cooling is used. No thermal hardening occurs.
Machining
Similar in character to 300-series austenitics, but the high work-hardening rate calls for rigid set-ups, carbide tooling, lower cutting speeds and chip breakers, since chips are tough and stringy.
Welding
Fusion welded with the usual arc processes, no preheat or postheat required. Use slower arc travel than for standard austenitics. Fillers ER209, E/ER308L, 309L. A little ferrite in the deposit limits hot cracking.
Forming
Good hot and cold formability. Intermediate annealing may be needed in heavy cold forming to restore ductility and avoid cracking.
Corrosion and wear behaviour
S20400 is specified for aqueous and atmospheric corrosion combined with wet abrasion, not as a high-alloy corrosion-resistant grade. Pitting resistance measured in 10% FeCl3 is better than Type 304. In sulfuric and hydrochloric acid it is considerably better than Types 409 and 410 and approaches Type 304 in more dilute solutions. As a class, stainless steels substantially out-wear abrasion-resistant carbon steels once conditions are even mildly corrosive, and S20400 is positioned as a more cost-effective choice than Types 409 and 304 in wet abrasive duty. It is commonly put forward as a replacement for AR400 in liner and chute service.
Where S20400 forgings are used
The established application set follows directly from the grade's strengths: strength-to-weight, toughness, weldability and wet abrasion resistance at a low alloy cost.
- Coal and mineral handling. Chute liners, screens, coal buckets, hopper cars, magnetic ore separator screens, and the shafts, sleeves and rolled rings that carry them.
- Bulk solids handling and water infrastructure. Hoppers, mixing tanks, well screens, water supply and control structures, sewage treatment plant structures.
- Transport structures. Truck and bus frames and bumpers, rapid transit structurals, where tensilized material offers up to roughly three times the strength-to-weight ratio of carbon steel, plus rear frames of refrigerated trucks and shipboard container structurals.
- Fasteners and hardware. Hose clamps, safety belt anchors, and general mechanical and structural components needing strength with corrosion resistance.
Because these are structural and wear duties rather than pressure containment, the forged items most often ordered in S20400 are rolled rings, shafts, bushings, sleeves, discs and blanks for machined wear parts, rather than pressure-boundary flanges.
Forged product forms in UNS S20400
All items are made to customer drawing or specification by open-die forging and ring rolling.
| Category | Items |
|---|---|
| Rings | Seamless rolled rings, forged rings, retaining rings, valve seat rings |
| Round and bar | Forged round bars, shafts, eccentric shafts, spindles, crankshafts, stems |
| Discs and blocks | Forged discs, blocks, blanks, gear blanks, wheels |
| Hollow | Forged tubes, pipes, sleeves, bushings, hollow bars, cylinders |
| Flat and plate type | Tube sheets, flanges, plates, forged bodies |
| Valve and machine parts | Valve bodies, valve blocks, nozzles, manifolds, rolls |
When enquiring, please state required dimensions, weight, quantity, heat-treatment condition, test requirements and acceptance standard, and send the drawing if you have one.
Testing and certification
Ultrasonic examination is carried out to the standard nominated on the order, commonly EN 10228-3, SEP 1921 or ASTM A388. Material certification is issued to EN 10204 3.1, or EN 10204 3.2 with third-party witness and endorsement where specified. Chemical analysis, tensile testing, hardness and dimensional reports are supplied with each heat and lot. Additional NDT, impact testing or corrosion testing can be arranged against the purchase specification.
Frequently asked questions
What is UNS S20400 stainless steel?
A nitrogen and manganese strengthened austenitic stainless steel containing 15.00-17.00% Cr, 7.00-9.00% Mn, 1.50-3.00% Ni and 0.15-0.30% N, listed in ASTM A666 and A240. It was developed for aqueous corrosion resistance combined with good toughness, wear resistance and economy, and provides about 50% higher yield strength than Type 304L.
How much manganese does UNS S20400 contain?
7.00 to 9.00 percent. Several web datasheets repeat a typo of 15-17%. Producer data and the ASTM A666 composition limits both give 7.00-9.00% Mn.
Is UNS S20400 magnetic?
Essentially non-magnetic as annealed, but it becomes magnetic with cold work, which distinguishes it from the other nitrogen-strengthened grades in this family. Deformation martensite forms, taking Ferrite Number from 0 to roughly 27 at 40% cold reduction and raising strength and abrasion resistance at the same time.
Can UNS S20400 be hardened by heat treatment?
No. It hardens only by cold work. Thermal cycles are used for annealing, at 1038-1121 C with rapid quench, or for stress relief at roughly 500-600 C with controlled cooling, not for hardening.
What is the difference between 204 and 304 stainless steel?
S20400 substitutes manganese and nitrogen for much of the nickel, which lowers cost and raises strength. Yield strength is around 50% higher than 304L, and pitting resistance in 10% FeCl3 testing is better than 304. In exchange it work-hardens faster, becomes magnetic when cold worked, and is less dependable in reducing acids. In less aggressive media it performs comparably to 304. In chloride-rich or acid service, 304 or a higher alloy is usually the safer specification.
Is S20400 suitable for seawater or subsea service?
It should not be specified on that basis. It is molybdenum-free and low in nickel. For seawater, firewater, subsea and high-chloride systems use a duplex, super-duplex or super-austenitic grade such as F51, F53, F55, F44, 904L or Sanicro 28, all of which we forge.
What minimum order quantity and lead time apply?
Both depend on part weight and on whether the grade is in stock as forging stock at the time of enquiry. Send the drawing, quantity and required certification level to sales@steelforgepieces.com, or call +86-189-2135-9659, and we will confirm feasibility, weight, price and schedule.
Data sources
- ASTM A666, Standard Specification for Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate, and Flat Bar, which lists S20400 composition and annealed mechanical requirements.
- Cleveland-Cliffs, NITRONIC 30 Stainless Steel Product Data, March 2022: composition, typical annealed and cold-worked properties, cold work and Ferrite Number data, corrosive wear and weldability.
- Armco NITRONIC 30 Stainless Steel technical bulletin: composition, annealed mechanical properties and physical properties.
- Published heat-treatment and forging practice for the grade: anneal 1038-1121 C with rapid quench, forge after equalising at about 1093 C then about 1176 C.
Figures on this page are for guidance in material selection. They do not replace the purchase specification, and properties achieved in a forged section depend on size, reduction and test location. Request a stamped mill certificate for contractual values. Page last reviewed 4 October 2026.