Stainless Steel S21603
UNS S21603 · AISI/SAE XM-18
S21603 (XM-18) is the low-carbon version of S21600, a nitrogen-strengthened Cr-Mn-Ni austenitic stainless.
Reference datasheet — S21603 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
S21603 tempers and conditions
S21603 is supplied in 7 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault Annealed (solution annealed ~1065–1120 °C, water quenched) | Standard stocked condition for plate, sheet, bar and forgings; best corrosion resistance, weldability and formability. | 450 | 760 | 48 | 200 HB | — |
Hot worked / as-forged (not solution annealed) | As-forged or hot-rolled bar supplied for subsequent machining and annealing; corrosion performance not guaranteed until solution treated. | 500 | 800 | 38 | 20 HRC | 2 % IACS |
Cold Drawn / cold finished bar (light cold work) | Choose for straight, close-tolerance bar with a modest strength bump over annealed; typical for shafts and fasteners stock. | 690 | 900 | 25 | 25 HRC | 2 % IACS |
Quarter hard | Light temper rolling for sheet/strip and high-strength fasteners where some bend ductility is still needed. | 690 | 900 | 25 | 25 HRC | 2 % IACS |
Half hard | Mid temper for springy strip, clamps and high-load non-magnetic fittings. | 790 | 1,035 | 15 | 30 HRC | 2 % IACS |
Three-quarter hard | High-strength strip/wire temper where forming is limited to gentle bends. | 930 | 1,170 | 12 | 35 HRC | 2 % IACS |
Cold worked, Full Hard (strain hardened) | Maximum strength strip/wire for springs and high-tensile non-magnetic parts; essentially no cold formability and reduced SCC margin. | 1,030 | 1,280 | 8 | 39 HRC | 2 % IACS |
What is S21603?
S21603 (XM-18) is the low-carbon version of S21600, a nitrogen-strengthened Cr-Mn-Ni austenitic stainless. The lower carbon avoids sensitization in weld heat-affected zones while keeping high strength: about 450 MPa yield, 760 MPa tensile, 48% elongation and 200 HB (93 HRB) annealed, in bar, plate and cold-drawn tempers to full hard. It is chosen for welded pressure and structural work up to roughly 815 °C, but machining is slow, cold work-hardening is rapid, and availability is narrower than the 300-series; S21600 suits non-welded high-strength parts and 316L substitutes where lower strength is acceptable. S21603 has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,370°C (2,498 °F). S21603 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 48% and the elastic modulus is 200 GPa (29 Msi).
What is S21603 used for?
- welded structural components
- pressure vessels
- fasteners
Advantages
- Ductile — tolerates forming and impact — 48%, better than 85% of stainless steel grades
- High service temperature — 815°C (1,499 °F), better than 77% of stainless steel grades
Limitations
- Low electrical conductivity — 2 % IACS, worse than 77% of stainless steel grades
S21603 properties
Typical room-temperature values for S21603-Annealed; bars are the position among stainless steel grades.
Physical3
S21603 has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical14
S21603 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 48% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
S21603 is rated for continuous service to 815°C (1,499 °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 16 µm/m·K (8.89 µin/in·°F).
Electrical3
S21603 conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 63% of stainless steel grades.
Sustainability4
Producing a kilogram of S21603 takes about 70 MJ of energy and emits 5 kg of CO₂ — more than 81% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
S21603's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability very good (75/100); 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. S21603 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S21603
Is S21603 easy to machine?
Treat as a difficult austenitic: rigid setups, positive-rake sharp carbide, heavy feeds and flood coolant to cut under the work-hardened skin; expect ~30 % of 1212 speeds.
Can S21603 be welded?
Readily welded by GTAW/GMAW without pre- or post-heat using over-alloyed filler (ER209, ER240 or ER316L for lower strength); ≤0.03 % C avoids sensitization, keep interpass below ~150 °C.
Can S21603 be formed, bent or molded?
Cold forms well but work-hardens fast — use larger bend radii, extra press tonnage and interstage solution anneals at 1065–1120 °C with rapid quench; hot work 1150–1230 °C, finish above 950 °C.
S21603 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 S21600 | ≤ 0.03 | 0.02 |
| Mn | 7.5 – 9 | 8.3 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | |
| S | ≤ 0.03 | |
| Cr | 17.5 – 22 | 20 |
| Ni | 5 – 7 | 6 |
| Mo | 2 – 3 | 2.5 |
| Nprimary strengthener | 0.25 – 0.5 | 0.35 |
| Fe | balance |
What surface finishes work on S21603?
Passivate per ASTM A967 or electropolish after fabrication; not anodizable, and pickling should use nitric-hydrofluoric baths sized for the high-Mn scale.
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 S21603 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- AISI / SAE
- XM-18
- Similar grades
- S21600
How much does S21603 cost?
S21603 is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
S21603 — frequently asked
What is S21603 used for?
S21603 is typically used for welded structural components, pressure vessels and fasteners. In short: weldable version of XM-17; low-carbon high-strength austenitic; no post-weld heat treatment.
What is the yield strength of S21603?
S21603 has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is S21603 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Treat as a difficult austenitic: rigid setups, positive-rake sharp carbide, heavy feeds and flood coolant to cut under the work-hardened skin; expect ~30 % of 1212 speeds.
Can S21603 be welded?
Yes — weldability is rated very good (75/100). Readily welded by GTAW/GMAW without pre- or post-heat using over-alloyed filler (ER209, ER240 or ER316L for lower strength); ≤0.03 % C avoids sensitization, keep interpass below ~150 °C.
What surface finishes work on S21603?
Passivate per ASTM A967 or electropolish after fabrication; not anodizable, and pickling should use nitric-hydrofluoric baths sized for the high-Mn scale.
Can S21603 be formed, bent or molded?
Cold forms well but work-hardens fast — use larger bend radii, extra press tonnage and interstage solution anneals at 1065–1120 °C with rapid quench; hot work 1150–1230 °C, finish above 950 °C.
What is the maximum service temperature of S21603?
S21603 is rated for continuous use to about 815°C (1,499 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does S21603 cost?
S21603 is a premium-cost stainless steel ($$$), cheaper than about 51% 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 A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- SAE/ASTM DS-56 (UNS) Metals & Alloys in the Unified Numbering System — S21600/S21603 — SAE International / ASTM (2017)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
- Nitrogen-strengthened Cr-Mn austenitic stainless product data (216/21-6-9 family) — Specialty stainless producers (2022)
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.