Stainless Steel XM-21
UNS S30452
XM-21 (UNS S30452) is a nitrogen-strengthened variant of Type 304 austenitic stainless, using interstitial nitrogen instead of carbon to raise strength without giving up the corrosion resistance or weldability of 304.
Reference datasheet — XM-21 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
XM-21 tempers and conditions
XM-21 is supplied in 6 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (1040–1120 °C, water quenched) | Standard stocked condition for plate, sheet, bar and tube; best corrosion resistance, ductility and weldability. | 400 | 690 | 48 | 200 HB | — |
Cold drawn | Choose for straight, close-tolerance bar with higher yield strength than annealed; retains good ductility. | 600 | 790 | 25 | 21 HRC | 2.4 % IACS |
Quarter hard | Sheet/strip temper for moderate strength increase while still allowing bending and mild forming. | 650 | 900 | 18 | 25 HRC | 2.4 % IACS |
Half hard | Use where high strength with limited bending is needed, e.g. structural strip, clamps and springs-of-convenience. | 800 | 1,060 | 12 | 32 HRC | 2.4 % IACS |
Three-quarter hard | Near-maximum strength strip for flat parts formed only by shallow bends or blanking. | 960 | 1,230 | 8 | 37 HRC | 2.4 % IACS |
Full hard | Maximum strength flat product for blanked, non-formed parts; very limited ductility and higher magnetic permeability. | 1,000 | 1,310 | 5 | 41 HRC | 2.4 % IACS |
What is XM-21?
XM-21 (UNS S30452) is a nitrogen-strengthened variant of Type 304 austenitic stainless, using interstitial nitrogen instead of carbon to raise strength without giving up the corrosion resistance or weldability of 304. In the annealed condition it shows about 400 MPa yield, 690 MPa tensile, 48 % elongation and 200 HB (92 HRB), and it is stocked as plate, sheet, bar and tube in Annealed, CD and 1/4H through full-hard tempers. The trade-off is a faster work-hardening rate, so machining and press loads are higher than for 304; where the extra yield strength is not needed, standard 304/304L is cheaper and more widely available. XM-21 has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F). XM-21 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of stainless steel grades. Elongation at break is 48% and the elastic modulus is 195 GPa (28.3 Msi).
What is XM-21 used for?
- Cryogenic storage vessels
- Structural pressure equipment
- Pressure vessel shells and heads
- Cryogenic piping and transfer lines
- Chemical process tanks
- Tank trailer and railcar bodies
- Structural sections for corrosive environments
Advantages
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Readily welded — 85/100, better than 87% of stainless steel grades
- Ductile — tolerates forming and impact — 48%, better than 85% of stainless steel grades
- Forms and bends easily — 70/100, better than 79% of stainless steel grades
XM-21 properties
Typical room-temperature values for XM-21-Annealed; bars are the position among stainless steel grades.
Physical3
XM-21 has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical14
XM-21 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of stainless steel grades. Elongation at break is 48% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
XM-21 is rated for continuous service to 800°C (1,472 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
XM-21 conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (70/100), better than 68% of stainless steel grades.
Sustainability4
Producing a kilogram of XM-21 takes about 53 MJ of energy and emits 4.5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 70%.
Manufacturability8
XM-21's machinability is fair (35/100, better than 51% of stainless steel grades); weldability excellent (85/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. XM-21 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with XM-21
Is XM-21 easy to machine?
Machines like 304 but work-hardens faster due to nitrogen — use rigid setups, positive-rake sharp carbide, heavy feed, no dwell, and flood coolant.
Can XM-21 be welded?
Readily welded by GTAW/GMAW/SMAW without preheat; use 308L/309L or high-nitrogen filler, keep interpass below ~150 °C and limit heat input to preserve the nitrogen strength benefit.
Can XM-21 be formed, bent or molded?
Cold forms and deep draws similar to 304 but needs roughly 20–30 % higher press loads and larger bend radii; hot work at 1150–1200 °C followed by solution anneal.
XM-21 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | ≤ 0.08 | 0.05 |
| Mn | ≤ 2 | 1.6 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Cr | 18 – 20 | 19 |
| Ni | 8 – 10.5 | 9 |
| Nnitrogen strengthening — the defining addition vs Type 304 | 0.16 – 0.3 | 0.22 |
| Fe | balance |
What surface finishes work on XM-21?
Not anodizable; pickle and passivate per ASTM A967, or electropolish/mechanically polish to No.4–No.8 finish for hygienic and decorative service.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel XM-21 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S30452
How much does XM-21 cost?
XM-21 is a standard-cost stainless steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
XM-21 — frequently asked
What is XM-21 used for?
XM-21 is typically used for cryogenic storage vessels, structural pressure equipment, pressure vessel shells and heads, cryogenic piping and transfer lines, chemical process tanks and tank trailer and railcar bodies. In short: nitrogen-strengthened 304; higher yield than 304; retains 304 weldability.
What is the yield strength of XM-21?
XM-21 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is XM-21 easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machines like 304 but work-hardens faster due to nitrogen — use rigid setups, positive-rake sharp carbide, heavy feed, no dwell, and flood coolant.
Can XM-21 be welded?
Yes — weldability is rated excellent (85/100). Readily welded by GTAW/GMAW/SMAW without preheat; use 308L/309L or high-nitrogen filler, keep interpass below ~150 °C and limit heat input to preserve the nitrogen strength benefit.
What surface finishes work on XM-21?
Not anodizable; pickle and passivate per ASTM A967, or electropolish/mechanically polish to No.4–No.8 finish for hygienic and decorative service.
Can XM-21 be formed, bent or molded?
Cold forms and deep draws similar to 304 but needs roughly 20–30 % higher press loads and larger bend radii; hot work at 1150–1200 °C followed by solution anneal.
What is the maximum service temperature of XM-21?
XM-21 is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between XM-21 Annealed and XM-21-FH?
Annealed is the default condition — standard stocked condition for plate, sheet, bar and tube; best corrosion resistance, ductility and weldability. FH: maximum strength flat product for blanked, non-formed parts; very limited ductility and higher magnetic permeability. Yield strength is 400 MPa in Annealed versus 1,000 MPa in FH.
How much does XM-21 cost?
XM-21 is a standard-cost stainless steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (UNS S30452, XM-21) — ASTM International (2023)
- ASTM A276/A479 — Stainless Steel Bars and Shapes — ASTM International (2022)
- ASTM A666 — Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate and Flat Bar — ASTM International (2015)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- SAE J405 / UNS S30452 chemical composition listing — SAE International (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.