Steel A203
ASTM A203 · UNS K21590
A203 is an ASTM nickel alloy steel pressure-vessel plate supplied with 2.25 % Ni (Grades A and B) or 3.5 % Ni (Grades D and E), UNS K21590, normally normalized, with a quenched-and-tempered Grade F and stress-relieved conditions also on file.
Reference datasheet — A203 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 GR-E-N condition
A203 tempers and conditions
A203 is supplied in 6 conditions, soft to hard. GR-E-N 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 |
|---|---|---|---|---|---|---|
Grade A | Lowest-strength 2.25%Ni plate for vessels down to about −59 °C where weight is not critical. | 290 | 490 | 28 | 140 HB | 40 W/m·K |
Grade D | Standard 3.5%Ni plate for cryogenic vessels and piping down to about −101 °C at moderate design stress. | 295 | 490 | 28 | 143 HB | 35 W/m·K |
Grade B | Choose when 2.25%Ni toughness is enough but a 70–90 ksi tensile class is needed to cut wall thickness. | 320 | 530 | 25 | 152 HB | 39 W/m·K |
GR-E-NDefault Grade E | Most commonly stocked A203 plate: 3.5%Ni toughness to −101 °C with the higher 70–90 ksi tensile class. | 325 | 535 | 25 | 156 HB | 35 W/m·K |
Stress relieved | Condition after 595–635 °C post-weld heat treatment of formed heads and welded shells; slightly lower yield, restored toughness. | 335 | 520 | 28 | 152 HB | 7.5 % IACS |
Grade F | Pick when the highest A203 design stress (55 ksi yield) is needed together with −101 °C toughness; Q&T supply only. | 630 | 745 | 22 | 21 HRC | 35 W/m·K |
What is A203?
A203 is an ASTM nickel alloy steel pressure-vessel plate supplied with 2.25 % Ni (Grades A and B) or 3.5 % Ni (Grades D and E), UNS K21590, normally normalized, with a quenched-and-tempered Grade F and stress-relieved conditions also on file. Engineers select it for vessels, shells and formed heads that must retain notch toughness at low temperature. Normalized plate runs about 325 MPa yield, 535 MPa tensile, 25 % elongation, 156 HB, 204 GPa modulus and 35 W/m·K, with a 370 °C service ceiling and density 7.87 g/cm³. Corrosion resistance is that of carbon steel (score 16), so coating or cladding is required; austenitic stainless is the alternative for deeper cryogenic duty. A203 has a density of 7.87 g/cm³ (0.284 lb/in³), heavier than 92% of steel grades. It melts at 1,415°C (2,579 °F). A203 has a yield strength of 325 MPa (47.1 ksi) and a tensile strength of 535 MPa (77.6 ksi) — weaker than 80% of steel grades. Elongation at break is 25% and the elastic modulus is 204 GPa (29.6 Msi).
What is A203 used for?
- Cryogenic pressure vessels
- LNG/LPG storage tanks
- Low-temperature piping heads
- Refrigeration equipment
Advantages
- Tough — resists crack growth — 155 MPa·√m (141.1 ksi·√in), better than 97% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- High embodied carbon — 2.7 kg CO₂/kg, worse than 89% of steel grades
- Low strength — 325 MPa (47.1 ksi), worse than 80% of steel grades
- Poor heat conductor — 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades
A203 properties
Typical room-temperature values for A203-GR-E-N; bars are the position among steel grades.
Physical3
A203 has a density of 7.87 g/cm³ (0.284 lb/in³), heavier than 92% of steel grades. It melts at 1,415°C (2,579 °F).
Mechanical16
A203 has a yield strength of 325 MPa (47.1 ksi) and a tensile strength of 535 MPa (77.6 ksi) — weaker than 80% of steel grades. Elongation at break is 25% and the elastic modulus is 204 GPa (29.6 Msi).
Thermal6
A203 is rated for continuous service to 370°C (698 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades. Thermal expansion is 11.2 µm/m·K (6.22 µin/in·°F).
Electrical3
A203 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of A203 takes about 36 MJ of energy and emits 2.7 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 28%.
Manufacturability7
A203's machinability is fair (52/100, better than 52% of steel grades); weldability good (63/100); formability good (58/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. A203 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A203
Is A203 easy to machine?
Machines like a 160–190 HB low-alloy steel — use rigid setups, sharp positive-rake carbide and generous coolant; the nickel makes chips gummier than plain carbon plate so run moderate speed with heavier feed.
Can A203 be welded?
Readily welded by SMAW/SAW/GTAW with matching 2.5Ni or 3.5Ni low-hydrogen consumables; preheat 100–150 °C for thick sections, control interpass and heat input, and PWHT at 595–635 °C where the code requires it, verifying weld-metal CVN at the design temperature.
Can A203 be formed, bent or molded?
Hot form above 900 °C then re-normalize, or cold roll/press heads with generous bend radii (≥2t) and re-heat-treat if cold strain exceeds 5 % to restore low-temperature toughness.
A203 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 |
|---|---|---|
| CGrade A/D ≤0.17, Grade B ≤0.21, Grade E/F ≤0.20 (heat analysis; limits rise slightly with thickness) | ≤ 0.2 | 0.17 |
| Mn0.80 max for Grade F and for heavier plate | ≤ 0.7 | 0.6 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.03 | 0.01 |
| Si | 0.15 – 0.4 | 0.28 |
| NiGrades D/E/F; Grades A/B are 2.10–2.50 % Ni | 3.25 – 3.75 | 3.5 |
| Fe | balance |
What surface finishes work on A203?
No anodizing possible; blast to SA 2.5 and apply epoxy/zinc-rich paint, metallizing or cladding for wet and marine service — the base steel corrodes like ordinary carbon steel.
Surface treatments FabDigit runs on 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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A203 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K21590
- ASTM
- A203 Grade A/B/D/E
How much does A203 cost?
A203 is a standard-cost steel ($$), cheaper than about 71% 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.
A203 — frequently asked
What is A203 used for?
A203 is typically used for cryogenic pressure vessels, LNG/LPG storage tanks, low-temperature piping heads and refrigeration equipment. In short: nickel plate for cryogenic vessels; tougher than carbon steel plate; weldable with matching Ni consumables.
What is the yield strength of A203?
A203 has a typical yield strength of 325 MPa (47.1 ksi) and a tensile strength of 535 MPa (77.6 ksi) — weaker than 80% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is A203 easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machines like a 160–190 HB low-alloy steel — use rigid setups, sharp positive-rake carbide and generous coolant; the nickel makes chips gummier than plain carbon plate so run moderate speed with heavier feed.
Can A203 be welded?
Yes — weldability is rated good (63/100). Readily welded by SMAW/SAW/GTAW with matching 2.5Ni or 3.5Ni low-hydrogen consumables; preheat 100–150 °C for thick sections, control interpass and heat input, and PWHT at 595–635 °C where the code requires it, verifying weld-metal CVN at the design temperature.
What surface finishes work on A203?
No anodizing possible; blast to SA 2.5 and apply epoxy/zinc-rich paint, metallizing or cladding for wet and marine service — the base steel corrodes like ordinary carbon steel.
Can A203 be formed, bent or molded?
Hot form above 900 °C then re-normalize, or cold roll/press heads with generous bend radii (≥2t) and re-heat-treat if cold strain exceeds 5 % to restore low-temperature toughness.
What is the maximum service temperature of A203?
A203 is rated for continuous use to about 370°C (698 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A203 GR-E-N and A203 GR-F-QT?
GR-E-N is the default condition — most commonly stocked A203 plate: 3.5%Ni toughness to −101 °C with the higher 70–90 ksi tensile class. GR-F-QT: pick when the highest A203 design stress (55 ksi yield) is needed together with −101 °C toughness; Q&T supply only. Yield strength is 325 MPa in GR-E-N versus 630 MPa in GR-F-QT.
How much does A203 cost?
A203 is a standard-cost steel ($$), cheaper than about 71% 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 A203/A203M — Pressure Vessel Plates, Alloy Steel, Nickel — ASTM International (2022)
- ASME BPVC Section II Part A / Part D — SA-203 material and allowable stresses — ASME (2023)
- ASME BPVC Section VIII Div.1 UCS/UHA impact-test requirements — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Low-temperature nickel steel plate datasheets (2.25Ni / 3.5Ni pressure-vessel plate) — Dillinger / NSSMC / Baosteel (2022)
- GB/T 3531 (comparison grades 09MnNiDR / 3.5Ni) — SAC (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.