Stainless Steel 321H
AISI/SAE 321H · UNS S32109 · ASTM A240 TP321H
321H is the higher-carbon, titanium-stabilized austenitic stainless of the 321 family (S32109, 1.4878, X8CrNiTi18-10, A240 TP321H), where the added carbon improves creep strength and the titanium ties up carbon to prevent intergranular attack after welding.
Values for the Solution Annealed condition
321H tempers and conditions
321H is supplied in 6 conditions, soft to hard. Solution Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
870–900 °C hold after solution anneal | Extra stabilizing soak that converts residual carbon to TiC; specified for refinery service to resist polythionic-acid and intergranular stress-corrosion cracking. | 235 | 575 | 42 | 160 HB | 2.4 % IACS |
Hot Rolled, Annealed and Pickled (HRAP plate / hot-finished bar) | Standard supply state for thick 321H plate and hot-finished bar for pressure vessels and structural high-temperature parts. | 235 | 560 | 45 | 165 HB | 2.4 % IACS |
Solution AnnealedDefault 1050–1100 °C, rapid cooled | Default mill condition for 321H plate, sheet, tube and pipe; maximum ductility and corrosion resistance, ASME-qualified for elevated-temperature service. | 240 | 585 | 45 | 160 HB | — |
mill-annealed sheet/strip and bar | Generic soft mill-annealed condition for cold-rolled sheet, strip and annealed bar; use when maximum formability is needed. | 250 | 600 | 45 | 165 HB | 2.4 % IACS |
cold-finished bar/wire (light cold work) | Cold-finished bar with higher strength, closer tolerance and better surface for machined fasteners and shafts; anneal or stabilize before long high-temperature exposure. | 415 | 690 | 30 | 200 HB | — |
Quarter hard | Lightly temper-rolled strip for springy clips, gaskets and expansion-joint bellows where extra yield strength is wanted at near-ambient temperature. | 530 | 790 | 15 | 25 HRC | 2.4 % IACS |
What is 321H?
321H is the higher-carbon, titanium-stabilized austenitic stainless of the 321 family (S32109, 1.4878, X8CrNiTi18-10, A240 TP321H), where the added carbon improves creep strength and the titanium ties up carbon to prevent intergranular attack after welding. Annealed material gives about 240 MPa yield, 585 MPa tensile, 45 % elongation and 160 HB, with service to 900 °C, in plate, sheet, cold-drawn bar, tube and stabilize-annealed conditions. Corrosion resistance is 304-level rather than 316-level, and TiC particles make it abrasive to cut (machinability 40); use 347H when niobium stabilization or a mirror finish is preferred. 321H 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). 321H has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 96% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
What is 321H used for?
- Aircraft and engine exhaust manifolds
- High-temperature pressure pipework
- Boiler and superheater components
- Expansion joints and bellows
- Refinery heater tubes and headers
- Furnace and heat-treatment fixtures
- Steam and gas turbine ducting
Advantages
- Forms and bends easily — 78/100, better than 90% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- High service temperature — 900°C (1,652 °F), better than 85% of stainless steel grades
- Readily welded — 82/100, better than 84% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Low strength — 240 MPa (34.8 ksi), worse than 96% of stainless steel grades
- Hard to polish — 60/100, worse than 80% of stainless steel grades
- High embodied carbon — 5.5 kg CO₂/kg, worse than 77% of stainless steel grades
321H properties
Typical room-temperature values for 321H-Solution Annealed; bars are the position among stainless steel grades.
Physical3
321H 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
321H has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 96% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
321H is rated for continuous service to 900°C (1,652 °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 conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (64/100), better than 54% of stainless steel grades.
Sustainability4
Producing a kilogram of 321H 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's machinability is fair (40/100, better than 72% of stainless steel grades); weldability very good (82/100); formability very good (78/100).
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. 321H is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 321H
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.
Manufacturability
The process limits FabDigit applies to 321H. Every 321H part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair40 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better78 / 100 |
|---|---|
| Weldability | Excellent82 / 100 |
| Bendable | Yes |
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 |
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.
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).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 321H in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S32109
- ASTM
- A240 TP321H
- Similar grades
- 1.4878X8CrNiTi18-10
How much does 321H cost?
321H is a premium-cost stainless steel ($$$), pricier than about 58% 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.
321H — frequently asked
What is 321H used for?
321H 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?
321H has a typical yield strength of 240 MPa (34.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 96% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is 321H easy to machine?
Not especially — machinability is rated fair (40/100, better than 72% 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 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?
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 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?
321H is rated for continuous use to about 900°C (1,652 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 321H cost?
321H is a premium-cost stainless steel ($$$), pricier than about 58% 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.
Can FabDigit make parts in 321H?
Yes — 321H is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. 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; 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.