Stainless Steel S21904 1/2H
Supply condition
UNS S21904 · AISI/SAE XM-11
1/2H = half hard
Higher-strength strip/bar for springs, clamps and load-carrying panels with limited bending.
Values for the 1/2H condition
Other S21904 tempers and conditions
S21904 is listed in 7 conditions; see the grade overview at S21904.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (~1040–1120 °C, rapid cool) | Standard stocked condition: maximum ductility and cryogenic toughness, best for welded fabrication and forming. | 415 | 745 | 48 | 200 HB | — |
Hot rolled | As-hot-worked heavy bar and plate for subsequent machining or annealing; properties vary with finishing temperature. | 480 | 800 | 40 | 21 HRC | 2.4 % IACS |
Cold drawn | Pick for machined shafts and fasteners needing ~690 MPa yield with better straightness and surface than annealed bar. | 690 | 900 | 25 | 28 HRC | — |
Quarter hard | Use where roughly double annealed yield strength is needed while keeping ~20% elongation for mild forming. | 760 | 965 | 20 | 30 HRC | — |
1/2HThis page Half hard | Higher-strength strip/bar for springs, clamps and load-carrying panels with limited bending. | 895 | 1,105 | 15 | 35 HRC | — |
Three-quarter hard | For high-strength flat springs and thin high-load sections where only gentle radii are formed. | 1,035 | 1,240 | 12 | 38 HRC | — |
Full hard | Maximum strength strip/wire for spring clips and high-strength non-magnetic fasteners; essentially no formability. | 1,170 | 1,380 | 8 | 42 HRC | — |
What is S21904 1/2H?
S21904 1/2H is S21904 supplied in the 1/2H condition — higher-strength strip/bar for springs, clamps and load-carrying panels with limited bending. S21904 1/2H has a yield strength of 895 MPa (130 ksi) and a tensile strength of 1,105 MPa (160 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 200 GPa (29 Msi). S21904 1/2H has a density of 7.83 g/cm³ (0.283 lb/in³), heavier than 58% of stainless steel grades. It melts at 1,370°C (2,498 °F). Annealed is the default condition FabDigit quotes; 1/2H is available on request or by drawing note.
Advantages
- High strength — 895 MPa (130 ksi), better than 98% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
Limitations
- Limited ductility — 15%, worse than 89% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
S21904 1/2H properties
Typical room-temperature values for S21904 1/2H; 12 are specific to this condition. Other listed values are S21904 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
S21904 1/2H has a density of 7.83 g/cm³ (0.283 lb/in³), heavier than 58% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
S21904 1/2H has a yield strength of 895 MPa (130 ksi) and a tensile strength of 1,105 MPa (160 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
S21904 1/2H is rated for continuous service to 400°C (752 °F). It conducts heat at 14.5 W/m·K (8.38 BTU/hr·ft·°F), worse than 72% of stainless steel grades. Thermal expansion is 15.1 µm/m·K (8.39 µin/in·°F).
Electrical3
S21904 1/2H conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (56/100), worse than 66% of stainless steel grades.
Sustainability4
Producing a kilogram of S21904 1/2H takes about 57 MJ of energy and emits 5.4 kg of CO₂ — more than 62% of stainless steel grades. Typical recycled content is 55%.
Manufacturability8
S21904 1/2H's machinability is poor (32/100, worse than 62% of stainless steel grades); weldability good (60/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S21904 1/2H
Is S21904 easy to machine?
Machine like a high-nitrogen austenitic: rigid setups, sharp positive-rake carbide, heavy feed with slow speed (~30% of 1212), flood coolant, and never dwell — it work-hardens instantly.
Can S21904 be welded?
Readily welded by GTAW/GMAW/SMAW without preheat or PWHT; use matching 21-6-9 or 209/240 filler (or ER308L for lower-strength joints), keep heat input low and avoid nitrogen loss from excessive arc exposure.
Can S21904 be formed, bent or molded?
Cold forms well but needs roughly twice the press force of 304 and generous bend radii; hot work at 1040–1200 °C then water quench, and re-anneal after severe cold work to restore ductility.
What surface finishes work on S21904?
Passivate per ASTM A967 or electropolish; takes a bright mechanical polish, but do not anodize — pickling of high-Mn scale requires stronger acid mixes than 304.
S21904 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 |
|---|---|---|
| Clow-carbon version of S21900 | ≤ 0.04 | 0.03 |
| Mn | 8 – 10 | 9 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.06 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Cr | 19 – 21.5 | 20.3 |
| Ni | 5.5 – 7.5 | 6.5 |
| Nprincipal strengthener | 0.15 – 0.4 | 0.3 |
| Fe | balance | — |
S21904 1/2H — frequently asked
What is S21904 1/2H used for?
S21904 1/2H is typically used for welded cryogenic tanks, aerospace structures and marine fasteners. In short: weldable Nitronic 40; best weldability in family; cryogenic toughness retained.
What is the yield strength of S21904 1/2H?
S21904 1/2H has a typical yield strength of 895 MPa (130 ksi) and a tensile strength of 1,105 MPa (160 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is S21904 1/2H easy to machine?
Not especially — machinability is rated poor (32/100, worse than 62% of stainless steel grades). Machine like a high-nitrogen austenitic: rigid setups, sharp positive-rake carbide, heavy feed with slow speed (~30% of 1212), flood coolant, and never dwell — it work-hardens instantly.
Can S21904 1/2H be welded?
Yes — weldability is rated good (60/100). Readily welded by GTAW/GMAW/SMAW without preheat or PWHT; use matching 21-6-9 or 209/240 filler (or ER308L for lower-strength joints), keep heat input low and avoid nitrogen loss from excessive arc exposure.
What surface finishes work on S21904 1/2H?
Passivate per ASTM A967 or electropolish; takes a bright mechanical polish, but do not anodize — pickling of high-Mn scale requires stronger acid mixes than 304.
Can S21904 1/2H be formed, bent or molded?
Cold forms well but needs roughly twice the press force of 304 and generous bend radii; hot work at 1040–1200 °C then water quench, and re-anneal after severe cold work to restore ductility.
What is the maximum service temperature of S21904 1/2H?
S21904 1/2H is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S21904 Annealed and S21904-FH?
Annealed is the default condition — standard stocked condition: maximum ductility and cryogenic toughness, best for welded fabrication and forming. FH: maximum strength strip/wire for spring clips and high-strength non-magnetic fasteners; essentially no formability. Yield strength is 415 MPa in Annealed versus 1,170 MPa in FH.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip — ASTM International (2023)
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Boilers and Pressure Vessels — ASTM International (2021)
- SAE/AMS 5561 & AMS 5656 (21Cr-6Ni-9Mn tube and bar) — SAE International (2019)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- Nitronic 40 (21-6-9) alloy datasheet — Specialty metals producer (2020)
- MMPDS-type typical/design allowables for 21-6-9 stainless — Battelle/FAA (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.