Steel A302
ASTM A302
A302 Grade A/B/C/D is a Mn-Mo (Grades A and B) and Mn-Mo-Ni (Grades C and D) alloy steel plate developed for thick-section pressure vessels, including nuclear reactor vessels.
Reference datasheet — A302 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 GrB-N condition
A302 tempers and conditions
A302 is supplied in 9 conditions, soft to hard. GrB-N is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Grade A | Lowest-strength Mn-Mo grade; pick when 310 MPa minimum yield and easy fabrication of moderate-thickness shells is enough. | 360 | 550 | 24 | 170 HB | — |
Stress relieved | Condition after simulated post-weld heat treatment cycles — the basis for design values in welded, heavy-wall vessels. | 375 | 565 | 25 | 170 HB | 7.9 % IACS |
As-rolled | Lowest-cost supply condition allowed for thinner plate where impact requirements are modest. | 390 | 600 | 21 | 11 HRC | 7.8 % IACS |
Normalized and tempered | Tempering after normalizing (620–660 °C) to stabilise properties and reduce residual stress before welding. | 395 | 575 | 24 | 175 HB | 7.8 % IACS |
GrB-NDefault Grade B | The workhorse A302 grade (higher Mn than A); default stock condition for boiler drums and heavy pressure-vessel shells at 345 MPa minimum yield. | 400 | 590 | 22 | 180 HB | — |
Normalized | Grain-refining normalize (~900 °C, air cool) — standard heavy-plate condition balancing strength and toughness. | 400 | 590 | 22 | 180 HB | 7.8 % IACS |
Grade C | Grade A chemistry plus 0.4–0.7 % Ni; choose when Grade A/B strength is needed with better notch toughness and section hardenability. | 405 | 590 | 23 | 185 HB | — |
Grade D | Highest-hardenability A302 grade (Grade B Mn level plus Ni); used for the thickest sections and the best low-temperature toughness, closest to A533 Type B. | 415 | 600 | 23 | 190 HB | — |
Quenched and tempered | Optional Q&T route giving the highest strength and upper-shelf toughness in very heavy sections — the practice that evolved into ASTM A533. | 480 | 640 | 21 | 17 HRC | — |
What is A302?
A302 Grade A/B/C/D is a Mn-Mo (Grades A and B) and Mn-Mo-Ni (Grades C and D) alloy steel plate developed for thick-section pressure vessels, including nuclear reactor vessels. It is supplied as-rolled, normalized, normalized and tempered, quenched and tempered, or stress relieved; the default condition gives 400 MPa yield, 590 MPa tensile, 22 % elongation and about 180 HB (89 HRB). Weldability is good (score 70) with low-hydrogen Mn-Mo consumables, but preheat and 595–650 °C PWHT are standard practice, and the plate needs paint or cladding because it has no corrosion resistance. A299 is the lower-cost C-Mn alternative for thinner shells. A302 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). A302 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is A302 used for?
- Nuclear reactor vessels
- Heavy-wall pressure vessels
- Boiler drums
Advantages
- Tough — resists crack growth — 150 MPa·√m (136.5 ksi·√in), better than 96% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
A302 properties
Typical room-temperature values for A302-GrB-N; bars are the position among steel grades.
Physical3
A302 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
A302 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A302 is rated for continuous service to 450°C (842 °F). It conducts heat at 41 W/m·K (23.7 BTU/hr·ft·°F), worse than 62% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
A302 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of A302 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability6
A302's machinability is good (55/100, better than 62% of steel grades); weldability very good (70/100); formability good (55/100).
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. A302 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A302
Is A302 easy to machine?
Machines like normalized 4130/1330 at ~60 % of AISI 1212; use rigid setups, carbide inserts at 120–180 m/min and generous coolant for heavy plate edge prep.
Can A302 be welded?
Readily welded by SAW/SMAW/GTAW with low-hydrogen Mn-Mo consumables; preheat 100–200 °C by thickness and PWHT at 595–650 °C is standard for pressure-vessel construction.
Can A302 be formed, bent or molded?
Hot-form heads and shells at 900–1000 °C followed by re-normalizing; cold rolling of shells is possible in thinner gauges with generous bend radii (≥2t).
A302 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 |
|---|---|---|
| Cheat analysis maximum, all grades | ≤ 0.25 | 0.2 |
| Mn0.95–1.30 for Grades A and C; 1.15–1.50 for Grades B and D | 0.95 – 1.5 | 1.3 |
| Si | 0.15 – 0.4 | 0.25 |
| Mo | 0.45 – 0.6 | 0.52 |
| NiGrades C and D only; not specified for Grades A and B | 0.4 – 0.7 | 0.55 |
| Plow P preferred for irradiation resistance | ≤ 0.04 | 0.01 |
| S | ≤ 0.04 | 0.01 |
| Cunot specified; kept low (<0.10) in nuclear-quality plate to limit irradiation embrittlement | ≈ 0.1 | 0.1 |
| Fe | balance |
What surface finishes work on A302?
No self-protection — blast and paint, or apply stainless/Alloy 600 weld overlay or roll-bonded cladding for wetted surfaces.
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 A302 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- A302 Grade A/B/C/D
- Also called
- predecessor to A533
How much does A302 cost?
A302 is a budget-cost steel ($), cheaper than about 90% 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.
A302 — frequently asked
What is A302 used for?
A302 is typically used for nuclear reactor vessels, heavy-wall pressure vessels and boiler drums. In short: mn-Mo nuclear vessel plate; heavy-section pressure grade; weldable with mandatory PWHT.
What is the yield strength of A302?
A302 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is A302 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like normalized 4130/1330 at ~60 % of AISI 1212; use rigid setups, carbide inserts at 120–180 m/min and generous coolant for heavy plate edge prep.
Can A302 be welded?
Yes — weldability is rated very good (70/100). Readily welded by SAW/SMAW/GTAW with low-hydrogen Mn-Mo consumables; preheat 100–200 °C by thickness and PWHT at 595–650 °C is standard for pressure-vessel construction.
What surface finishes work on A302?
No self-protection — blast and paint, or apply stainless/Alloy 600 weld overlay or roll-bonded cladding for wetted surfaces.
Can A302 be formed, bent or molded?
Hot-form heads and shells at 900–1000 °C followed by re-normalizing; cold rolling of shells is possible in thinner gauges with generous bend radii (≥2t).
What is the maximum service temperature of A302?
A302 is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A302 GrB-N and A302-QT?
GrB-N is the default condition — the workhorse A302 grade (higher Mn than A); default stock condition for boiler drums and heavy pressure-vessel shells at 345 MPa minimum yield. QT: optional Q&T route giving the highest strength and upper-shelf toughness in very heavy sections — the practice that evolved into ASTM A533. Yield strength is 400 MPa in GrB-N versus 480 MPa in QT.
How much does A302 cost?
A302 is a budget-cost steel ($), cheaper than about 90% 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 A302/A302M — Pressure Vessel Plates, Alloy Steel, Manganese-Molybdenum and Manganese-Molybdenum-Nickel — ASTM International (2017)
- ASME BPVC Section II Part A (SA-302) and Part D (allowable stresses, physical properties) — 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)
- Heavy Section Steel Technology (HSST) Program plate 02 characterization reports — Oak Ridge National Laboratory (1985)
- GB/T 713 (15MnMoR / 13MnNiMoR comparison grades) — 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.