Stainless Steel S81921
UNS S81921
A low-nickel, manganese-nitrogen alloyed lean duplex stainless steel (~19-21% Cr) that substitutes Mn for costly Ni while retaining a balanced ferrite-austenite structure and good stress-corrosion resistance.
Reference datasheet — S81921 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
S81921 tempers and conditions
S81921 is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Welded & annealed tube/pipe (ASTM A789/A790 class) | Standard condition for welded pipe and tubing — post-weld solution anneal restores phase balance and corrosion performance across the weld. | 515 | 720 | 32 | 22 HRC | 2.2 % IACS |
AnnealedDefault solution annealed (~1020–1100 °C) and rapid water quenched | Standard supply condition for plate, sheet, bar, pipe and fittings; balanced ferrite/austenite with optimum corrosion resistance and toughness. | 520 | 730 | 35 | 21 HRC | — |
Cold drawn | Pick for bar, shafting and fasteners needing tighter tolerance, better straightness and higher yield strength than annealed bar. | 700 | 860 | 20 | 28 HRC | 2.2 % IACS |
Quarter hard | Light cold work for strip and structural profiles where extra yield strength is wanted with usable bendability. | 720 | 900 | 18 | 30 HRC | 2.2 % IACS |
Half hard | For springy strip, clamps and weight-optimised structural strip where high strength beats formability. | 850 | 1,020 | 12 | 34 HRC | 2.2 % IACS |
Supply forms, finishes and certifications
Ways S81921 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
2B | Cold rolled, annealed, pickled and skin-passed sheet | Surface finish |
HRAP | No.1 | Surface finish |
What is S81921?
A low-nickel, manganese-nitrogen alloyed lean duplex stainless steel (~19-21% Cr) that substitutes Mn for costly Ni while retaining a balanced ferrite-austenite structure and good stress-corrosion resistance. S81921 has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,420°C (2,588 °F). S81921 has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi).
What is S81921 used for?
- storage tanks
- structural components
- transport tankers
- low-chloride process equipment
Advantages
- Low embodied carbon — 3.6 kg CO₂/kg, better than 83% of stainless steel grades
- High strength — 520 MPa (75.4 ksi), better than 79% of stainless steel grades
Limitations
- Limited service temperature — 280°C (536 °F), worse than 96% of stainless steel grades
S81921 properties
Typical room-temperature values for S81921-Annealed; bars are the position among stainless steel grades.
Physical3
S81921 has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,420°C (2,588 °F).
Mechanical17
S81921 has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
S81921 is rated for continuous service to 280°C (536 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 59% of stainless steel grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
S81921 conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (63/100), better than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of S81921 takes about 52 MJ of energy and emits 3.6 kg of CO₂ — less than 76% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
S81921's machinability is fair (40/100, better than 72% of stainless steel grades); weldability very good (70/100); formability good (55/100).
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. S81921 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S81921
Is S81921 easy to machine?
Cuts like a tough, work-hardening duplex: use rigid setups, sharp positive-rake carbide, heavy feeds with no dwell, ~60–70 % of 304 speeds and flood coolant.
Can S81921 be welded?
Weld with GTAW/GMAW/SMAW using 2209 or matching lean-duplex filler and Ar+2%N₂ backing; keep heat input ~0.5–2.0 kJ/mm and interpass <150 °C to hold ~50/50 ferrite-austenite; no preheat, no post-weld temper in the 300–1000 °C range.
Can S81921 be formed, bent or molded?
Cold forms well but needs roughly twice the press force of 304 with large springback allowance; hot form at 950–1150 °C followed by full solution anneal and water quench.
S81921 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 | ≤ 0.03 | 0.02 |
| MnMn substitutes for Ni and stabilises N solubility | 2 – 4 | 3 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.03 | 0 |
| Cr | 19 – 21.5 | 20 |
| Nilean-Ni design | 2 – 4 | 3 |
| Momax; usually residual level | ≤ 1 | 0.3 |
| Cu | ≤ 1 | 0.3 |
| Naustenite stabiliser, raises strength and pitting resistance | 0.14 – 0.2 | 0.17 |
| Fe | balance |
What surface finishes work on S81921?
Pickle and passivate (HNO₃-HF) after hot work or welding to remove heat tint; can be mechanically polished, bead blasted or electropolished — no anodizing.
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
How much does S81921 cost?
S81921 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.
S81921 — frequently asked
What is S81921 used for?
S81921 is typically used for storage tanks, structural components, transport tankers and low-chloride process equipment. In short: low-nickel duplex, lower cost; twice the yield of 304; below 2205 in pitting.
What is the yield strength of S81921?
S81921 has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is S81921 easy to machine?
Not especially — machinability is rated fair (40/100, better than 72% of stainless steel grades). Cuts like a tough, work-hardening duplex: use rigid setups, sharp positive-rake carbide, heavy feeds with no dwell, ~60–70 % of 304 speeds and flood coolant.
Can S81921 be welded?
Yes — weldability is rated very good (70/100). Weld with GTAW/GMAW/SMAW using 2209 or matching lean-duplex filler and Ar+2%N₂ backing; keep heat input ~0.5–2.0 kJ/mm and interpass <150 °C to hold ~50/50 ferrite-austenite; no preheat, no post-weld temper in the 300–1000 °C range.
What surface finishes work on S81921?
Pickle and passivate (HNO₃-HF) after hot work or welding to remove heat tint; can be mechanically polished, bead blasted or electropolished — no anodizing.
Can S81921 be formed, bent or molded?
Cold forms well but needs roughly twice the press force of 304 with large springback allowance; hot form at 950–1150 °C followed by full solution anneal and water quench.
What is the maximum service temperature of S81921?
S81921 is rated for continuous use to about 280°C (536 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S81921 Annealed and S81921-CD?
Annealed is the default condition — standard supply condition for plate, sheet, bar, pipe and fittings; balanced ferrite/austenite with optimum corrosion resistance and toughness. CD: pick for bar, shafting and fasteners needing tighter tolerance, better straightness and higher yield strength than annealed bar. Yield strength is 520 MPa in Annealed versus 700 MPa in CD.
How much does S81921 cost?
S81921 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 — ASTM International (2023)
- ASTM A789/A790 — Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing and Pipe — ASTM International (2021)
- ASTM A276/A479 — Stainless Steel Bars and Shapes — ASTM International (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Practical Guidelines for the Fabrication of Duplex Stainless Steels — IMOA (2014)
- Lean duplex stainless steel plate/coil datasheets (2101/2003-class) — Outokumpu / TISCO / Baosteel (2023)
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.