Stainless Steel 321H · supply condition
Stainless Steel 321H-1/4 Hard
Properties of the 1/4 Hard condition, compared with the other 321H tempers.
Lightly temper-rolled strip for springy clips, gaskets and expansion-joint bellows where extra yield strength is wanted at near-ambient temperature.
What is 321H-1/4 Hard?
321H-1/4 Hard is 321H supplied in the 1/4 Hard condition — lightly temper-rolled strip for springy clips, gaskets and expansion-joint bellows where extra yield strength is wanted at near-ambient temperature. 321H-1/4 Hard has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 193 GPa (28 Msi). 321H-1/4 Hard has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 67% 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
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 84% of stainless steel grades
- Readily welded — 82/100, better than 83% of stainless steel grades
- High strength — 530 MPa (76.9 ksi), better than 81% of stainless steel grades
Limitations
- Limited ductility — 15%, worse than 89% of stainless steel grades
- Hard to polish — 60/100, worse than 80% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
- High embodied carbon — 5.5 kg CO₂/kg, worse than 77% of stainless steel grades
321H-1/4 Hard properties
Typical room-temperature values for 321H-1/4 Hard — 9 properties are specific to this condition; the rest are grade-level values shared by every 321H temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.
Physical3
321H-1/4 Hard has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 67% of stainless steel grades. It melts at 1,398°C (2,548 °F).
Mechanical16
321H-1/4 Hard has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
321H-1/4 Hard is rated for continuous service to 400°C (752 °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
321H-1/4 Hard conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (64/100), better than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of 321H-1/4 Hard takes about 56 MJ of energy and emits 5.5 kg of CO₂ — more than 59% of stainless steel grades. Typical recycled content is 55%.
Manufacturability7
321H-1/4 Hard's machinability is fair (40/100, better than 73% of stainless steel grades); weldability very good (82/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 321H tempers and conditions
321H is also supplied in 5 other conditions. The full side-by-side table is on the 321H overview.
- Solution AnnealedDefaultDefault mill condition for 321H plate, sheet, tube and pipe; maximum ductility and corrosion resistance, ASME-qualified for elevated-temperature service.240 MPa yield · 160 HB
- 1/4 HardLightly temper-rolled strip for springy clips, gaskets and expansion-joint bellows where extra yield strength is wanted at near-ambient temperature.530 MPa yield · 25 HRC
- Cold DrawnCold-finished bar with higher strength, closer tolerance and better surface for machined fasteners and shafts; anneal or stabilize before long high-temperature exposure.415 MPa yield · 200 HB
- AnnealedGeneric soft mill-annealed condition for cold-rolled sheet, strip and annealed bar; use when maximum formability is needed.250 MPa yield · 165 HB
- Hot Rolled AnnealedStandard supply state for thick 321H plate and hot-finished bar for pressure vessels and structural high-temperature parts.235 MPa yield · 165 HB
Working with 321H-1/4 Hard
Is 321H easy to machine?
Treat as a gummy work-hardening austenitic: rigid setup, positive-rake sharp carbide, 0.15–0.35 mm/rev feed, 60–110 m/min, flood coolant, never dwell — TiC particles accelerate tool wear versus 304.
Can 321H be welded?
Excellent by GTAW/GMAW/SMAW without post-weld anneal; use ER347/E347 or ER321 filler (Nb-stabilized filler avoids Ti burn-off), keep heat input moderate and interpass low, no preheat, avoid carbon pickup and use back purge on tube.
Can 321H be formed, bent or molded?
Cold forms readily but work-hardens faster than 304 — allow ~15 % more press force, generous bend radii and interstage anneal at 1050–1100 °C for severe draws; hot work 1150–1200 °C, finish above 900 °C then solution anneal.
What surface finishes work on 321H?
Not anodizable: pickle in HNO₃/HF and passivate in nitric or citric acid; Ti carbonitride stringers can leave streaks in mirror polish, so electropolishing or bead blast is preferred for high-purity or decorative surfaces.
321H 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 |
|---|---|---|
| Craised carbon vs. 321 for creep strength | 0.04 – 0.1 | 0.06 |
| Cr | 17 – 19 | 18 |
| Ni | 9 – 12 | 10.5 |
| Tispec minimum = 4×(C+N); 0.24 shown as practical minimum | 0.24 – 0.7 | 0.4 |
| Mn | ≤ 2 | 1.2 |
| Si | ≤ 0.75 | 0.5 |
| N | ≤ 0.1 | 0.02 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance | — |
321H-1/4 Hard — frequently asked
What is 321H-1/4 Hard used for?
321H-1/4 Hard is typically used for aircraft and engine exhaust manifolds, high-temperature pressure pipework, boiler and superheater components, expansion joints and bellows, refinery heater tubes and headers and furnace and heat-treatment fixtures. In short: high-temp titanium-stabilized stainless.
What is the yield strength of 321H-1/4 Hard?
321H-1/4 Hard has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 81% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is 321H-1/4 Hard easy to machine?
Not especially — machinability is rated fair (40/100, better than 73% of stainless steel grades). Treat as a gummy work-hardening austenitic: rigid setup, positive-rake sharp carbide, 0.15–0.35 mm/rev feed, 60–110 m/min, flood coolant, never dwell — TiC particles accelerate tool wear versus 304.
Can 321H-1/4 Hard be welded?
Yes — weldability is rated very good (82/100). Excellent by GTAW/GMAW/SMAW without post-weld anneal; use ER347/E347 or ER321 filler (Nb-stabilized filler avoids Ti burn-off), keep heat input moderate and interpass low, no preheat, avoid carbon pickup and use back purge on tube.
What surface finishes work on 321H-1/4 Hard?
Not anodizable: pickle in HNO₃/HF and passivate in nitric or citric acid; Ti carbonitride stringers can leave streaks in mirror polish, so electropolishing or bead blast is preferred for high-purity or decorative surfaces.
Can 321H-1/4 Hard be formed, bent or molded?
Cold forms readily but work-hardens faster than 304 — allow ~15 % more press force, generous bend radii and interstage anneal at 1050–1100 °C for severe draws; hot work 1150–1200 °C, finish above 900 °C then solution anneal.
What is the maximum service temperature of 321H-1/4 Hard?
321H-1/4 Hard 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.
Can FabDigit make parts in 321H-1/4 Hard?
Yes — 321H-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 A213/A213M — Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — ASTM International (2022)
- ASTM A312 / A276 — Austenitic Stainless Steel Pipe and Bars — ASTM International (2022)
- ASME BPVC Section II Part D — Properties (Metric) — ASME (2023)
- GB/T 24511 / GB/T 1220 — (06Cr18Ni11Ti) — SAC (2017)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Outokumpu 4878 / 321H stainless steel data sheet — Outokumpu (2023)
- Sandvik 8R30 / TP321H tube data sheet — Alleima (Sandvik Materials Technology) (2022)
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.