Home / Stainless Steel / Nitronic 32
Nitrogen-alloyed austenitic stainless steel
Nitronic 32 Forgings UNS S24100, XM-28. Seamless rolled rings, flanges, bars, discs, shafts.
Nitronic 32 is a low-nickel, high-manganese austenitic stainless steel strengthened by nitrogen. Published mill data gives it about twice the yield strength of Type 304 with comparable corrosion resistance.
Manganese at 11 to 14 percent and nitrogen at 0.20 to 0.45 percent hold the austenite that nickel would normally stabilise, which is why the nickel range is only 0.50 to 2.50 percent. Strength comes from nitrogen in solution and from cold work, so the grade is supplied annealed or cold worked. It does not respond to hardening heat treatment.
We melt this grade in our own furnaces, forge it on our own presses and ring mills, heat treat it in our own furnaces and machine it in our own shop. The certificate traces the part back to the melt number.
What the grade is for
Nitronic 32 is specified for two reasons: a part has to carry more load than Type 304 can carry in the same envelope, or the nickel content has to stay low. It is not a chloride-service alloy and it is not a wear-resistant alloy.
The published application list for the grade centres on high-strength cold-formed and cold-headed work: clamps for pole line hardware, concrete reinforcing accessories, shafting, dam gate stems, skid wire for underground transmission lines, abrasion and corrosion-resistant screens, high-strength non-magnetic springs, wire forms, racks and cages, fasteners and communication hardware. In forged form the common requests are shafting, gate stems, screen and hopper hardware, water-control parts and structural components where a low-nickel stainless with Type 304-class corrosion resistance and much higher yield strength suits the duty.
Two points worth checking before you specify this grade.
Nitronic 32 is not the anti-galling grade. That is Nitronic 60, UNS S21800, a silicon-bearing alloy selected for wear and galling resistance. The two are often confused because of the shared trade name.
Nitronic 32 is also not a seawater or hot-chloride alloy. Mill data states that its corrosion resistance approaches Type 304 in weak acid and pitting media but falls somewhat below Type 304 in more aggressive media, and that the higher carbon content leaves it less resistant to intergranular attack. For seawater, subsea, flue-gas desulphurisation or strong acid duty we would quote duplex, super-austenitic or nickel alloy instead, and we will say so on the quotation rather than take the order on the wrong grade.
Chemical composition
| Element | Content (%) | Note |
|---|---|---|
| Carbon, C | 0.15 max | Higher than Type 304, governs sensitisation behaviour |
| Manganese, Mn | 11.00 to 14.00 | Austenite stabiliser in place of nickel |
| Silicon, Si | 1.00 max | |
| Phosphorus, P | 0.060 max | 0.045 max in the Electralloy nominal analysis |
| Sulphur, S | 0.030 max | |
| Chromium, Cr | 16.50 to 19.00 | AZoM lists 16.5 to 19.5 |
| Nickel, Ni | 0.50 to 2.50 | |
| Nitrogen, N | 0.20 to 0.45 | Principal strengthening addition |
| Iron, Fe | Balance |
Where published sources differ on a range, both figures are shown. The governing limits on any order are those of your purchase specification. Send the specification and edition and we will certify against it.
Mechanical and physical properties
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 690 MPa | 100,000 psi |
| Yield strength, 0.2 % offset | 379 MPa | 55,000 psi |
| Elongation at break | 30 % | 30 % |
| Hardness | HRB 92 | HRB 92 |
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.83 g/cm³ | 0.283 lb/in³ |
| Melting range | 1450 to 1510 °C | 2642 to 2750 °F |
| Thermal expansion, 23 to 93 °C | 16.16 µm/m·°C | 8.98 µin/in·°F |
Heavy open-die forgings are tested in the delivered section rather than on a thin coupon, so state the test location and orientation your specification calls for. Where mid-wall properties govern, tell us at enquiry stage and we will plan the forging reduction and the sacrificial test extension around it.
Forging, heat treatment, machining, welding
Forging
Published practice is to forge at 1093 °C (2000 °F) and then heat to 1177 °C (2150 °F). Our own route on heavier sections is to bring the stock to roughly 1093 °C, soak until the section has equalised, then raise to roughly 1177 °C and equalise again before the first blow. The alloy work-hardens quickly, so reheats are planned into the sequence rather than called for when the piece stops moving. In-process annealing is carried out between 1038 and 1093 °C (1900 and 2000 °F).
Annealing
Anneal at 1038 to 1121 °C (1900 to 2050 °F) and quench in water or air. Avoid slow cooling through the carbide range. The grade hardens by cold work only.
Machining
Machining calls for slow speeds, positive feeds and plenty of lubricant. The combination of high yield strength and a high work-hardening rate punishes light feeds and flexible set-ups, so we machine these forgings on rigid vertical and horizontal lathes with deliberate depth of cut. Forgings leave as-forged, proof machined or finish machined to drawing.
Welding
The alloy welds by gas tungsten arc, gas metal arc and submerged arc. Pre-heating is not required.
Shapes we forge in Nitronic 32
Every item below is forged from one piece of steel melted on site. No welding, no casting, no billet of unknown origin.
Seamless rolled rings
Ring-rolled from a punched preform on radial-axial mills of 1 m, 3 m and 6 m, to 6,000 mm outside diameter. Rectangular or contoured section.
Forged rings
Upset and punched rings for sections outside the ring-mill envelope, and from OD 50 mm where a rolled ring is too large a route.
Flanges
Weld neck, blind, slip-on, socket weld, lap joint, orifice and long weld neck, to ASME B16.5 and B16.47 dimensions.
Round bars and blocks
Forged round, flat and square bar above normal rolled-bar availability, as feedstock for machined valve bodies and hardware.
Discs and tube sheets
Solid forged discs, tube sheets and covers, supplied proof machined for volumetric inspection.
Shafts and spindles
Stepped shafts, gate stems, eccentric shafts and spindles. Turned length to 14,000 mm, with a 15 m well furnace for vertical quenching.
Sleeves and bushings
Hollow forged cylinders, sleeves, bushings and couplings bored from solid forged blanks to 1,600 mm diameter by 10,000 mm.
Valve parts
Bodies, bonnets, stems, seat rings and blocks for ball, gate, globe, check and plug valves.
Why order this grade from the melt shop
Nitronic 32 carries 0.20 to 0.45 percent nitrogen. Nitrogen is the thing that makes the grade work, and it is the thing that is easiest to lose or to get wrong if the billet was bought in.
This works melts its own steel. Stainless and duplex grades run through the electric arc furnace, a ladle furnace and vacuum oxygen decarburisation, which is the route used where low carbon or tight nitrogen control matters. Protective-atmosphere electroslag remelting is available for nitrogen-alloyed grades where cleanness also has to be held. Because the chemistry is aimed at the forging it will become, rather than accepted as delivered on someone else's certificate, the nitrogen level on a Nitronic 32 order is set in our furnace and reported from our melt number.
| Stage | Equipment | Capacity |
|---|---|---|
| Primary melting | Electric arc furnace, ladle furnace | 60 t maximum heat |
| Vacuum degassing | Vacuum oxygen decarburisation | 30 t and 60 t |
| Remelting | Protective-atmosphere electroslag furnace | 3 t and 6 t |
| Forging | Hydraulic open-die presses | 6,300 t, 4,000 t, 2,000 t |
| Ring rolling | Radial-axial ring mills | 6 m, 3 m, 1 m |
| Heat treatment | Car-bottom and well-type furnaces | 14 furnaces, 15 m deep pit furnaces |
| Single piece | Finished forging | 30 t maximum |
Inspection and certification
Each order is covered by a certificate traceable to the heat. Chemical analysis, tensile testing, hardness and grain size are standard, with impact testing where the specification calls for it. Ultrasonic examination is available to EN 10228-3, SEP 1921 or ASTM A388, with dye penetrant inspection on machined surfaces. Certification is issued to EN 10204 3.1, or 3.2 with a third-party body attending. The works holds CCS, BV, DNV, LR and NK approvals and ships to North America, Europe, the Middle East and Asia-Pacific.
Questions we are asked
Is Nitronic 32 the same thing as XM-28 and UNS S24100?
Yes. Nitronic 32 is the trade name, UNS S24100 is the alloy number, XM-28 is the ASTM designation, and Alloy 241 turns up on older drawings. Quote whichever one your drawing carries.
Which specification should go on the enquiry?
For forging stock, ASTM A314 covers stainless steel billets and bars for forging. AZoM also lists ASTM A580, the wire specification, as an equivalent designation for the grade. If a customer or project specification applies instead, send it with the drawing.
Can the grade be heat treated to a higher strength?
No. It hardens by cold work only. For forgings that means the annealed condition, or cold-finished bar where the section allows.
Is it magnetic?
The published application list includes high-strength non-magnetic springs, which reflects the low magnetic permeability of the annealed austenitic structure. If a permeability limit is a design requirement, state the limit and the test method on the enquiry so it can be verified rather than assumed.
Will it pass ASTM A262?
Not after sensitising. The Electralloy data sheet states that the higher carbon content leaves the alloy less resistant to intergranular attack than Type 304 and that it will not pass ASTM A262 tests when sensitised at 1250 °F (677 °C). Plan the thermal history accordingly.
What size and quantity will you take?
Minimum order is 10 kg with no minimum piece count, up to 30 t in a single piece. Lead time runs 20 to 60 days depending on grade, section and heat treatment.
Do you supply the other Nitronic grades?
Yes, including Nitronic 30, 33, 40, 50 and 60. Nitronic 60 is the one to ask about if galling or wear is the problem you are solving.
Quote a Nitronic 32 forging
Send a drawing or rough dimensions with the quantity, specification and delivery condition. Quotations normally go out within one working day.
Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone, WhatsApp and WeChat +86 189 2135 9659
Email sales@steelforgepieces.com
Sources for the alloy data on this page
- Electralloy, Nitronic 32 Austenitic Stainless Steel Alloy (UNS S24100, XM 28). Composition, applications, corrosion behaviour, ASTM A262 note.
- Ulbrich Stainless Steels and Special Metals, Nitronic 32 Stainless Steel. Yield strength relative to Type 304.
- AZoM, Super Alloy Nitronic 32 (UNS S24100). Annealed properties, density, melting range, thermal expansion, forging and annealing temperatures, welding and machining.
Nitronic is a registered trademark of AK Steel and is used here only to identify the alloy. Data is published for general guidance and is not a warranty of fitness for a particular design.