ASTM grade designation · Austenitic stainless
XM-10 The ASTM grade designation for UNS S21900, the 21-6-9 nitrogen-strengthened austenitic stainless steel
XM-10 is a grade designation, not a specification and not a trade name. It identifies UNS S21900 inside ASTM product standards such as A276 for bars and shapes and A314 for billets and bars for forging. The alloy itself is sold in the trade as 21-6-9 or 21Cr-6Ni-9Mn: 19.0 to 21.5 % chromium, 5.50 to 7.50 % nickel, 8.00 to 10.00 % manganese and 0.15 to 0.40 % nitrogen, with a 0.08 % carbon ceiling. Jiangyin Jiangnan Metal Co., Ltd. melts and forges this grade in one works in Jiangyin, Jiangsu Province, China.
The full datasheet for the alloy, with mechanical, physical, corrosion and heat treatment tables, sits on our UNS S21900 page. This page covers the designation itself: where XM-10 comes from, how it differs from XM-11, and what we forge in it.
- UNS number
- S21900
- ASTM grade
- XM-10
- Trade names
- 21-6-9, 21Cr-6Ni-9Mn, Alloy 219
- Family
- Nitrogen-strengthened austenitic
- Carbon ceiling
- 0.08 % max
- Low-carbon twin
- XM-11 / S21904, 0.04 % max
- Molybdenum
- Not a type-analysis element
- Magnetic
- No, including after cold work
- Forging start
- 1150 to 1205 C
- Service ceiling
- 871 C (1600 F)
- Melting
- EF, LF, VOD; ESR on request
- Ring capacity
- OD 50 to 6000 mm, to 30 t
Where the XM designation comes from
ASTM uses XM numbers for grades that were brought into its product standards without an AISI type number. They are internal grade labels. A drawing calling for XM-10 is calling for the S21900 chemistry, and the tolerances, testing and acceptance rules come from whichever product specification the order is placed against. XM-10 on its own does not tell you the product form, the condition or the test requirements.
Three XM grades sit close enough together to be confused on enquiries, and all three are nitrogen-strengthened manganese austenitics. Keep them apart on paperwork.
| Designation | UNS | Trade name | Separating feature |
|---|---|---|---|
| XM-10 | S21900 | 21-6-9 | 0.08 % C max |
| XM-11 | S21904 | 21-6-9 LC | 0.04 % C max, same base chemistry |
| XM-19 | S20910 | Nitronic 50 | Molybdenum, niobium and vanadium added; higher strength and better chloride resistance |
XM-19 is a different alloy, not a variant of XM-10. If chloride resistance is the reason for the enquiry, see Nitronic 50 / XM-19.
XM-10 against XM-11
This is the question that costs the most time on enquiries. The two grades differ in one figure. Everything else in the type analysis is identical, so a mill certificate showing 0.03 % carbon satisfies both. The reverse is not true: material certified only to XM-10 may carry up to 0.08 % carbon and cannot be shipped against an XM-11 order.
| Element | XM-10 / S21900 | XM-11 / S21904 | Our normal aim |
|---|---|---|---|
| Carbon | 0.08 max | 0.04 max | 0.02 to 0.04 |
| Chromium | 19.0 to 21.5 | 19.0 to 21.5 | 20.0 |
| Nickel | 5.50 to 7.50 | 5.50 to 7.50 | 6.0 |
| Manganese | 8.00 to 10.00 | 8.00 to 10.00 | 9.0 |
| Nitrogen | 0.15 to 0.40 | 0.15 to 0.40 | 0.23 to 0.27 |
| Silicon | 1.00 max | 1.00 max | under 0.60 |
| Phosphorus | 0.060 max | 0.060 max | under 0.040 |
| Sulphur | 0.030 max | 0.030 max | under 0.015 |
Specifications that carry the grade
XM-10 is a grade inside product standards. Name the product standard as well as the grade when you order, and state the edition if your project is tied to one.
| Product form | Specification | Applies to |
|---|---|---|
| Bars and shapes | ASTM A276 | XM-10 and XM-11 |
| Billets and bars for forging | ASTM A314 | XM-10 and XM-11 |
| Bars for pressure-vessel use | ASTM A479 / ASME SA-479 | XM-10 and XM-11 |
| Bars, wire, forgings, rings, extrusions | AMS 5656 | S21904 |
| Sheet, plate, strip | AMS 5595 | 21-6-9 chemistry |
| Tube | AMS 5561 | 21-6-9 chemistry |
| Weld wire | AWS A5.9 ER219, AMS 5818 | Matching filler |
Editions change. Check the specification revision in force for your project before releasing a drawing, and tell us which one applies so the certificate matches.
Properties in short
Nitrogen in solid solution puts annealed yield strength at roughly double that of Type 304, which is the usual reason a designer lands on this grade. Corrosion resistance approaches Type 304L, oxidation resistance in air is good, resistance to molten lead oxide is good, and the steel stays non-magnetic after heavy cold work. It is solution strengthened and cannot be hardened by heat treatment.
| Property | Imperial | Metric |
|---|---|---|
| 0.2 % yield, min | 50 ksi | 345 MPa |
| Tensile, min | 90 ksi | 621 MPa |
| Elongation in 2 in., min | 45 % | 45 % |
| Hardness, max | 100 HRB | 241 HBW |
| Density | 0.283 lb/in³ | 7830 kg/m³ |
| Modulus of elasticity | 28.5 × 10³ ksi | 196.5 GPa |
Working the grade
| Operation | Parameters |
|---|---|
| Initial forging | 1150 to 1205 C, 2100 to 2200 F, no intermediate preheat |
| Lower hot-working limit | About 650 C, 1200 F. No hot shortness across the range |
| Cooling after forging | May be cooled rapidly without danger of cracking |
| Annealing | 982 to 1177 C, 1800 to 2150 F, then cool quickly. Around 900 C where grain size is capped |
| Stress relief | 482 to 760 C. Little change to cold-reduced properties up to 677 C, faster change above, rapid softening from 816 C |
| Machining | Normal austenitic practice. Rigid setup and ample coolant because the work-hardening rate is high |
| Welding | Shielded fusion and resistance processes. AWS E/ER219 for near-base-metal strength, E/ER309 otherwise. Oxyacetylene not recommended |
Figures above are condensed. Elevated-temperature tensile data, stress-rupture values, thermal conductivity, expansion coefficients, permeability and corrosion rates are tabulated on the UNS S21900 datasheet.
Forged products we make in XM-10
| Family | Typical items | Size limit |
|---|---|---|
| Seamless rolled rings | Rectangular and contoured section, gear ring blanks, slewing rings, bearing races | OD 50 to 6000 mm |
| Forged rings | Upset and punched rings, retaining rings, valve seat rings | Heavy sections outside the ring-mill envelope |
| Flanges | Weld neck, blind, slip-on, socket weld, lap joint, orifice, long weld neck | Per drawing |
| Shafts and spindles | Stepped, gear, pinion and eccentric shafts, rotors, tie rods | To 14000 mm turned length |
| Bars, blocks, blanks | Round, flat and square bar, die and mould blocks | Per drawing |
| Discs and tube sheets | Solid discs, pierced discs, tube sheets, covers | To 5000 mm machined diameter |
| Cylinders, sleeves, bushings | Hollow forged cylinders, couplings, heavy-wall sections bored from solid | To 1600 mm dia × 10000 mm bored |
| Valve and wellhead parts | Bodies, bonnets, blocks, stems, seat rings, spools, nozzles, manifolds | Per drawing |
Single-piece weight runs to 30 t against a 60 t maximum heat. Minimum order is 10 kg with no minimum piece count, so one prototype forging is accepted.
Where it ends up
Chemical plant
Autoclave closures and rings, scrubber internals, flanges, sleeves and tube sheets in process and pollution-control service.
Aerospace
Structural rings and shafts, engine hardware and hydraulic tubing components where strength per unit section matters.
Non-magnetic hardware
Clamps, instrument parts and structural rings that must stay below a permeability limit after forming.
Cryogenic and steam
Vessel and valve components, steam and autoclave parts held within the 871 C service ceiling.
Melting, testing, certification
Heats run through the electric arc furnace and ladle furnace, then through vacuum oxygen decarburisation to bring carbon down while holding the 0.15 to 0.40 % nitrogen window. That second part is what separates a mill that knows this grade from one that does not: nitrogen is easy to lose. Protective-atmosphere electroslag remelting is available where a remelted product is specified. Maximum heat size is 60 t.
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Documentation to EN 10204 3.1, or 3.2 with third-party witness. Chemical analysis, room-temperature and sub-zero tensile and impact testing, hardness, grain size, PMI, dye penetrant and ASTM A262 intergranular corrosion testing are available. Traceability runs from melt number to shipped part. Works approvals held: CCS, BV, DNV, LR, NK.
Questions we get on this grade
What is XM-10 stainless steel?
XM-10 is an ASTM grade designation, not a trade name. It identifies UNS S21900, a high-manganese austenitic stainless steel strengthened with 0.15 to 0.40 % nitrogen and sold in the trade as 21-6-9 or 21Cr-6Ni-9Mn. The designation appears inside ASTM bar and billet standards such as A276 and A314.
What is the difference between XM-10 and XM-11?
Only the carbon ceiling. XM-10 is S21900 at 0.08 % carbon maximum, XM-11 is S21904 at 0.04 % maximum. Chromium, nickel, manganese, nitrogen, silicon, phosphorus and sulphur ranges are identical. Material certified to XM-11 satisfies an XM-10 order; the reverse does not hold.
Is XM-10 the same as Nitronic 40?
Nitronic 40 is a trade name covering the 21-6-9 chemistry and is quoted against both S21900 and S21904. Since those two carry different carbon ceilings, an enquiry written only as Nitronic 40 is ambiguous. Put the UNS number or the XM designation on the order. Nitronic is a registered trademark of Cleveland-Cliffs Steel Corp.
Which ASTM specifications list grade XM-10?
Bars and shapes under ASTM A276, billets and bars for forging under ASTM A314, bars for pressure-vessel use under ASTM A479 and ASME SA-479. The grade has no standard of its own. Confirm the edition in force against your purchase specification.
What are the minimum mechanical properties of XM-10 bar?
Annealed bar is normally taken at 50 ksi (345 MPa) minimum 0.2 % yield, 90 ksi (621 MPa) minimum tensile, 45 % minimum elongation in 2 inches, hardness capped at 241 HBW or 100 HRB. The governing specification and edition decide what applies to a given order, and heavy forged sections are tested on their own prolongations.
At what temperature is XM-10 forged?
Start at 1150 to 1205 C with no intermediate preheat. The alloy hot works down to roughly 650 C, shows no hot shortness across that range and can be cooled rapidly after forging without cracking. Anneal afterwards at 982 to 1177 C to restore corrosion resistance.
Is XM-10 suitable for seawater service?
No. No deliberate molybdenum, and general corrosion resistance approaching Type 304L, which is short of what chloride-rich seawater, firewater, subsea or sour duty needs. Use duplex, super-duplex, 904L, a 6Mo austenitic or a nickel alloy instead.
Is XM-10 magnetic after cold work?
It stays effectively non-magnetic. Permeability is 1.004 to 1.005 annealed and 1.010 to 1.012 after 60 % cold reduction, below 1.020 at 500 oersteds. That is the reason it gets picked for non-magnetic clamps, instrument parts and structural rings.
What is the minimum order and lead time?
Ten kilograms, no minimum piece count, so a single prototype is accepted. Lead time runs 20 to 60 days depending on size, melting route and test scope. Price is quoted against the drawing, the finished weight and the quantity.
Ask for a price
Send the drawing or the rough dimensions, the governing specification, the quantity and the test scope. We reply with finished weight, price and lead time. Drawings in STEP, DWG, DXF or PDF.
Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone +86 189 2135 9659
Email sales@steelforgepieces.com
Email the drawing Full S21900 datasheet
Data on this page is given for guidance and is not a warranty of properties for a specific forging. Grade and specification references should be checked against the edition in force for your project. Page reviewed .