Nitronic 50 Forgings Rolled rings, flanges, shafts, discs, sleeves and tube sheets in nitrogen-strengthened austenitic stainless steel

Limits below are the ASTM A182 grade FXM-19 forging limits. Plate specifications written to ASTM A240 restrict silicon tighter, to 0.75 per cent maximum, so check which document your drawing calls before the melt is aimed.

Nitrogen and manganese carry the strengthening. Nitrogen sits interstitially and raises yield strength sharply; manganese is there mainly to keep that much nitrogen in solution. The 11.5 to 13.5 per cent nickel is what holds the structure fully austenitic. Drop the nickel and the microstructure moves toward duplex, with higher strength but less toughness, which is the practical reason this grade costs more than a duplex of similar strength.

Specified minimum properties, annealed

Typical values across temperature

Mill data for annealed material. Use these for comparison only; acceptance values are those of the purchase order.

Strain-hardened levels

Where the annealed grade is not strong enough, S20910 is also supplied strain-hardened in graded levels, published for bar. Section size caps what is reachable, and for sour service the NACE hardness ceiling governs which level you may use. On heavy open-die work the achievable condition depends on the reduction route, so state the strength level, hardness limit and test location on the enquiry and we will confirm before quoting.

Thermal data

Electrical resistivity is about 820 microhm·mm at 24 °C.

Higher chromium and molybdenum than 316 put the pitting resistance equivalent number near 34, against about 25 for 316L. Super duplex grades run above 40, but with a different toughness and fabrication profile, and that difference is usually why an engineer specifies S20910 instead.

Reported performance is good in many reducing and oxidising acids, in chlorides and in pitting environments, including seawater, boiling 65 per cent nitric acid, ferric sulphate-sulphuric acid and ammonium carbamate. Like most stainless steels it can still crack by stress corrosion in hot chlorides; in boiling 42 per cent magnesium chloride it is reported to resist cracking about as well as 316.

The grade is listed in NACE MR0175 / ISO 15156 for sour service on the strength of its resistance to sulphide stress cracking. Acceptance in a specific sour application still depends on meeting the hardness limit and the environmental envelope in the standard, both of which are tied to supplied condition and section size.

Most forging suppliers in China buy billet. We start at the furnace, which lets the chemistry be aimed at the part it will become rather than accepted as delivered.

Works approvals held: CCS, BV, DNV, LR and NK. Minimum order is 10 kg with no minimum piece count, and normal lead time runs 20 to 60 days depending on size and testing.

Notes for your machine shop

S20910 machines harder than 316. Run slower speeds with higher feeds, keep tools sharp, and never let an edge ride the surface without cutting, because the work-hardening rate will glaze it and the next pass will suffer. Chips come off tough and stringy, so chip breakers or curlers earn their keep. Forming follows normal austenitic practice but needs more force, and in-process annealing at 1065 to 1120 °C may be required on severe work.

For welding, conventional stainless processes apply. ER209 filler, also sold as Nitronic 50W, matches the base composition and gives a joint at base-metal strength; adding 3 to 5 per cent nitrogen to the shielding gas helps. Where lower joint strength is acceptable, 316L filler can be used. If you plan on electron beam or laser welding, raise it with us first, since the nitrogen content can cause outgassing in autogenous high-energy-density welds.

Sectors that buy this grade from us most often are chemical and fertiliser plant, where urea reactors, carbamate pumps, exchangers and valves see ammonium carbamate; marine and offshore, covering seawater pumps, ballast gate valves, rod rigging and subsea hardware; oil and gas production, including downhole and wellhead equipment under sour conditions; nuclear waste handling, such as calcination systems and canisters; and pulp and paper, food processing and pharmaceutical equipment. Low magnetic permeability also puts it into non-magnetic instrument and implant work, and ASTM F1314 covers bar for surgical implants.

Related grades we forge: A286, 17-4 PH, 15-5 PH, 17-7 PH, PH 13-8 Mo, AISI 330, Incoloy 825 and Inconel 625. Full list on the stainless steel and nickel alloy pages.

What is Nitronic 50 equivalent to?

It is the same material as UNS S20910 and the ASTM generic designation XM-19, written FXM-19 for forgings under ASTM A182, and it corresponds closely to European 1.3964. The 1.3964 and S20910 designations are commonly treated as interchangeable, but they are not identical in every detail, so on a critical part confirm which specification the drawing actually calls.

Is it stronger than 316?

Yes. Annealed S20910 carries a specified minimum yield of 380 MPa, roughly double annealed 304 or 316, and typical annealed yield sits near 448 MPa at room temperature. Strain-hardened levels reach 180 ksi minimum yield on small bar sizes.

Can it be used in sour service?

It is listed in NACE MR0175 / ISO 15156 and in NACE MR0103 for its resistance to sulphide stress cracking. Whether it qualifies for your specific well still depends on meeting the hardness limit and the environmental limits in the standard, and those are decided by supplied condition and section size. Send the sour-service data sheet with the enquiry and we will confirm the heat treatment route before manufacture.

What forging and annealing temperatures do you use?

Forging runs at 1150 to 1205 °C. Published mill guidance extends to 1232 °C at the top end, and we set the practice to the section being worked. Solution annealing is 1065 to 1120 °C followed by rapid cooling. No preheat to an intermediate temperature is needed, and the material can be cooled quickly after hot work without cracking. The grade is not hardenable by heat treatment.

Why is it hard to machine?

Because it work-hardens quickly. Cutting speeds have to come down while feeds go up, the set-up has to be rigid, and the tool must stay engaged in the cut. Where the design allows, ordering in the solution-annealed condition rather than strain-hardened makes the machining markedly easier.

What sizes can you make?

Rings up to 6,000 mm outside diameter on the 6 m radial-axial mill, shafts to 14,000 mm turned length, discs and tube sheets to 5,000 mm machined diameter, bored cylinders to 1,600 mm diameter by 10,000 mm, and single pieces up to 30 t. The small end starts at rings of 50 mm outside diameter and a 10 kg minimum order.

Who makes these parts?

Jiangyin Jiangnan Metal Co., Ltd., an integrated melting works and open-die forge at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, operating since 1997 with 460 staff. Contact sales@steelforgepieces.com or +86 189 2135 9659.

1. ATI, technical data sheet for ATI 50 / ATI XM-19, UNS S20910. Composition to ASTM A240, thermal expansion and conductivity, resistivity, typical tensile data from −320 to 1000 °F, forging and annealing practice, machinability, weldability, corrosion behaviour.
2. ASTM A182 / A182M grade FXM-19, forging composition limits and specified minimum mechanical properties.
3. Cleveland-Cliffs, Armco Nitronic 50 product data bulletin, hot working temperature range and general grade behaviour.
4. Langley Alloys, grade notes for Nitronic 50, pitting resistance equivalent comparison against 316L and super duplex, NACE MR0175 listing, role of nickel in holding austenite.
5. Aircraft Materials, Nitronic 50 data sheet, high-strength bar levels 1 to 5 and specification list.
6. voestalpine Specialty Metals, notes on the relationship between 1.3964, Alloy 50 and XM-19.
7. AZoM, grade reference for Nitronic 50 (XM-19), density, specification cross-list, applications.
8. Midalloy, product bulletin for ER209 bare wire, use as filler for S20910 base metal.

Nitronic is a registered trademark of AK Steel Corporation, part of Cleveland-Cliffs Inc. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with, endorsed by or licensed by the trademark holder. The name appears here only to identify the generic grade UNS S20910 / ASTM XM-19, which is the material we melt and forge. Property figures on this page are taken from the published sources listed above and are given for comparison; the values that govern acceptance are those stated in the purchase order and the applicable standard. Page last revised 3 October 2026.