Stainless Steel 312
AISI/SAE 312 · UNS S31200 · ASTM A789/A790 UNS S31200
AISI 312 (UNS S31200) is an early-generation 22Cr-5Ni-3Mo-N duplex stainless covered by ASTM A789/A790, offering higher strength and chloride pitting resistance than 316L.
Reference datasheet — 312 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 SA condition
312 tempers and conditions
312 is supplied in 3 conditions, soft to hard. SA is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefault Solution Annealed + Quenched | Standard delivery condition for all wrought product forms — balanced ~50/50 austenite/ferrite, best corrosion resistance and toughness. | 530 | 760 | 30 | 24 HRC | 2.2 % IACS |
Hot Finished / Forged + Solution Annealed Bar & Forgings | Bar, forged flanges and valve bodies solution annealed after hot work — general machined-component stock. | 540 | 760 | 28 | 25 HRC | 2.2 % IACS |
Cold drawn | Cold-drawn bar or tube for higher strength, tighter tolerance and better surface — reduced ductility and toughness. | 720 | 880 | 20 | 30 HRC | 2.2 % IACS |
Supply forms, finishes and certifications
Ways 312 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
SA-Plate | Solution Annealed Plate / Sheet | Supply form |
SA-SMLS | Solution Annealed Seamless Pipe / Tube | Supply form |
SA-WLD | Solution Annealed Welded Pipe / Tube | Supply form |
What is 312?
AISI 312 (UNS S31200) is an early-generation 22Cr-5Ni-3Mo-N duplex stainless covered by ASTM A789/A790, offering higher strength and chloride pitting resistance than 316L. Solution-annealed product provides 530 MPa yield, 760 MPa tensile, 30 % elongation and about 250 HB (24 HRC) as plate, seamless and welded tube, hot-finished and cold-drawn bar. Service is capped at 280 °C, ferrite balance must be controlled during welding, and the grade is largely superseded by 2205, which is the default choice for new designs and easier to source. 312 has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,385°C (2,525 °F). 312 has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 30% and the elastic modulus is 200 GPa (29 Msi).
What is 312 used for?
- chemical process piping
- heat exchangers
- pressure vessels
- marine equipment
Advantages
- High strength — 530 MPa (76.9 ksi), better than 81% of stainless steel grades
Limitations
- Limited service temperature — 280°C (536 °F), worse than 96% of stainless steel grades
312 properties
Typical room-temperature values for 312-SA; bars are the position among stainless steel grades.
Physical3
312 has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,385°C (2,525 °F).
Mechanical17
312 has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 30% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
312 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
312 conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 73% of stainless steel grades.
Sustainability4
Producing a kilogram of 312 takes about 55 MJ of energy and emits 4.6 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
312's machinability is fair (35/100, better than 51% of stainless steel grades); weldability very good (70/100); formability fair (45/100).
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. 312 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 312
Is 312 easy to machine?
Work-hardens rapidly and cuts tough like 2205 — use rigid setups, sharp coated carbide, heavy positive feeds, ~25 % of 1212 speeds and copious coolant; avoid dwelling.
Can 312 be welded?
Weldable by GTAW/GMAW/SMAW with 25Cr over-alloyed or 2209-type filler and N-bearing shielding; hold heat input ~0.5–2.5 kJ/mm, interpass <150 °C to keep ferrite 35–65 % and avoid σ-phase; no PWHT unless full re-solution anneal.
Can 312 be formed, bent or molded?
Cold form with ~2× the force of 304 and generous springback allowance; hot form 950–1150 °C followed by full solution anneal 1020–1100 °C and rapid water quench.
312 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 duplex | ≤ 0.03 | 0.02 |
| Mn | ≤ 2 | 1.2 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 24 – 26 | 25 |
| Ni | 5.5 – 6.5 | 6 |
| Mo | 1.2 – 2 | 1.7 |
| Naustenite stabiliser, boosts pitting resistance | 0.14 – 0.2 | 0.17 |
| Fe | balance | — |
What surface finishes work on 312?
Pickle and passivate (HNO₃/HF) after hot work or welding to restore the passive film; electropolishes and mechanically polishes well; never anodized.
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 312 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S31200
- ASTM
- A789/A790 UNS S31200
How much does 312 cost?
312 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.
312 — frequently asked
What is 312 used for?
312 is typically used for chemical process piping, heat exchangers, pressure vessels and marine equipment. In short: early-generation duplex; higher strength than 316L; 280 °C service limit.
What is the yield strength of 312?
312 has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 81% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is 312 easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Work-hardens rapidly and cuts tough like 2205 — use rigid setups, sharp coated carbide, heavy positive feeds, ~25 % of 1212 speeds and copious coolant; avoid dwelling.
Can 312 be welded?
Yes — weldability is rated very good (70/100). Weldable by GTAW/GMAW/SMAW with 25Cr over-alloyed or 2209-type filler and N-bearing shielding; hold heat input ~0.5–2.5 kJ/mm, interpass <150 °C to keep ferrite 35–65 % and avoid σ-phase; no PWHT unless full re-solution anneal.
What surface finishes work on 312?
Pickle and passivate (HNO₃/HF) after hot work or welding to restore the passive film; electropolishes and mechanically polishes well; never anodized.
Can 312 be formed, bent or molded?
Cold form with ~2× the force of 304 and generous springback allowance; hot form 950–1150 °C followed by full solution anneal 1020–1100 °C and rapid water quench.
What is the maximum service temperature of 312?
312 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 312-SA and 312-CD?
SA is the default condition — standard delivery condition for all wrought product forms — balanced ~50/50 austenite/ferrite, best corrosion resistance and toughness. CD: cold-drawn bar or tube for higher strength, tighter tolerance and better surface — reduced ductility and toughness. Yield strength is 530 MPa in SA versus 720 MPa in CD.
How much does 312 cost?
312 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 A790/A790M Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe — ASTM International (2023)
- ASTM A789/A789M Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service — ASTM International (2023)
- ASTM A240/A240M Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip — ASTM International (2022)
- SAE J1086 / ASTM DS-56 Unified Numbering System (UNS S31200) — SAE/ASTM (2017)
- 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)
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.