Stainless Steel 321-1/4 Hard
Supply condition
AISI/SAE 321 · UNS S32100 · ASTM A240 TP321 · EN 1.4541, X6CrNiTi18-10 · JIS SUS321
1/4 Hard = quarter hard
Use where moderate spring-back and higher yield are required but some bending is still needed.
Values for the 1/4 Hard condition
Other 321 tempers and conditions
321 is listed in 6 conditions; see the grade overview at 321.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
softened mill condition (sheet/strip/bar, ASTM A240/A276 minimums) | Generic annealed supply condition; use when only the standard minimum mechanical guarantees are needed. | 235 | 600 | 45 | 150 HB | 2.4 % IACS |
Solution AnnealedDefault 1010–1120 °C, rapid cooled (mill annealed) | Standard stocked condition for plate, sheet, bar, pipe and fittings — maximum ductility and corrosion resistance. | 240 | 620 | 45 | 150 HB | — |
321H | Choose 321H when ASME creep allowables above ~540 °C are needed (C 0.04–0.10 %); otherwise identical processing to 321. | 245 | 620 | 45 | 150 HB | 2.4 % IACS |
Cold Drawn Bar / Wire (lightly cold worked) | Pick for machined shafts and fasteners needing higher yield and better surface/straightness than annealed bar. | 550 | 760 | 22 | 215 HB | — |
1/4 HardThis page Quarter hard | Use where moderate spring-back and higher yield are required but some bending is still needed. | 600 | 900 | 12 | 25 HRC | 2.4 % IACS |
Half hard | High-strength strip for clamps, shims and lightly formed springs; forming limited to gentle bends. | 760 | 1,035 | 8 | 32 HRC | 2.4 % IACS |
What is 321-1/4 Hard?
321-1/4 Hard is 321 supplied in the 1/4 Hard condition — use where moderate spring-back and higher yield are required but some bending is still needed. 321-1/4 Hard has a yield strength of 600 MPa (87 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 86% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 193 GPa (28 Msi). 321-1/4 Hard has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,398°C (2,548 °F). Solution Annealed is the default condition FabDigit quotes; 1/4 Hard is available on request or by drawing note.
Advantages
- Readily welded — 85/100, better than 87% of stainless steel grades
- High strength — 600 MPa (87 ksi), better than 86% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
Limitations
- Limited ductility — 12%, worse than 95% of stainless steel grades
- Limited service temperature — 300°C (572 °F), worse than 90% of stainless steel grades
- High embodied carbon — 6 kg CO₂/kg, worse than 88% of stainless steel grades
321-1/4 Hard properties
Typical room-temperature values for 321-1/4 Hard; 23 are specific to this condition. Other listed values are 321 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
321-1/4 Hard has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,398°C (2,548 °F).
Mechanical16
321-1/4 Hard has a yield strength of 600 MPa (87 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 86% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
321-1/4 Hard is rated for continuous service to 300°C (572 °F). It conducts heat at 16.1 W/m·K (9.3 BTU/hr·ft·°F), better than 61% of stainless steel grades. Thermal expansion is 16.6 µm/m·K (9.22 µin/in·°F).
Electrical3
321-1/4 Hard conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of 321-1/4 Hard takes about 60 MJ of energy and emits 6 kg of CO₂ — more than 70% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
321-1/4 Hard's machinability is fair (35/100, better than 51% of stainless steel grades); weldability excellent (85/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 321-1/4 Hard
Is 321 easy to machine?
Machines like 304 but titanium carbides accelerate tool wear — use rigid setups, sharp carbide/coated tools, positive rake, 30–60 m/min, heavy feed and flood coolant to avoid work hardening and gumming.
Can 321 be welded?
Excellent by GTAW/GMAW/SMAW/plasma with ER321/ER347 filler; Ti stabilization means no post-weld solution anneal is needed for service in the 425–900 °C sensitization band, but keep interpass temperature low and avoid over-heating to limit distortion.
Can 321 be formed, bent or molded?
Good deep-drawing and bending in the annealed condition; work-hardens rapidly (n ≈ 0.4), so allow generous spring-back, intermediate anneals for severe draws, and expect higher press loads than mild steel.
What surface finishes work on 321?
Pickle and passivate (ASTM A967) or electropolish after welding to restore the chromium oxide film; No.4/mirror polishing is achievable but Ti inclusions can leave faint streaks on bright-annealed or mirror finishes.
321 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 |
|---|---|---|
| C0.04–0.10 for 321H | ≤ 0.08 | 0.05 |
| Si | ≤ 0.75 | 0.5 |
| Mn | ≤ 2 | 1.3 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Cr | 17 – 19 | 17.8 |
| Ni | 9 – 12 | 10 |
| Timin 5×(C+N) per ASTM A240; min 4×(C+N) for 321H | ≤ 0.7 | 0.35 |
| N | ≤ 0.1 | 0.02 |
| Fe | balance | — |
321-1/4 Hard — frequently asked
What is 321-1/4 Hard used for?
321-1/4 Hard is typically used for aircraft exhaust manifolds, chemical process piping, heat exchanger tubing, expansion joints and bellows, annealing furnace hoods and boiler components. In short: creep resistant high-temp.
What is the yield strength of 321-1/4 Hard?
321-1/4 Hard has a typical yield strength of 600 MPa (87 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 86% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is 321-1/4 Hard easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machines like 304 but titanium carbides accelerate tool wear — use rigid setups, sharp carbide/coated tools, positive rake, 30–60 m/min, heavy feed and flood coolant to avoid work hardening and gumming.
Can 321-1/4 Hard be welded?
Yes — weldability is rated excellent (85/100). Excellent by GTAW/GMAW/SMAW/plasma with ER321/ER347 filler; Ti stabilization means no post-weld solution anneal is needed for service in the 425–900 °C sensitization band, but keep interpass temperature low and avoid over-heating to limit distortion.
What surface finishes work on 321-1/4 Hard?
Pickle and passivate (ASTM A967) or electropolish after welding to restore the chromium oxide film; No.4/mirror polishing is achievable but Ti inclusions can leave faint streaks on bright-annealed or mirror finishes.
Can 321-1/4 Hard be formed, bent or molded?
Good deep-drawing and bending in the annealed condition; work-hardens rapidly (n ≈ 0.4), so allow generous spring-back, intermediate anneals for severe draws, and expect higher press loads than mild steel.
What is the maximum service temperature of 321-1/4 Hard?
321-1/4 Hard is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 321-1/4 Hard?
Yes — 321-1/4 Hard is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip — ASTM International (2023)
- ASTM A276/A479 — Stainless Steel Bars and Shapes — ASTM International (2022)
- EN 10088-2 (X6CrNiTi18-10, 1.4541) — CEN (2014)
- GB/T 20878 / GB/T 4237 (06Cr18Ni11Ti) — SAC (2015)
- JIS G 4304/G 4305 (SUS321) — JSA (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Outokumpu Stainless Steel Handbook — Outokumpu (2013)
- Sandvik / Alleima 321 and 321H alloy datasheets — Alleima (2023)
- (SMM) / Mysteel — SMM / Mysteel (2025)
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.