Steel A372 Grade C
ASTM A372 Grade C
A372 Grade C is a higher-strength carbon steel forging grade of the ASTM A372 series, with increased carbon and manganese content for greater allowable stress in thin-walled pressure vessels.
Reference datasheet — A372 Grade C 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 N+T condition
A372 Grade C tempers and conditions
A372 Grade C is supplied in 4 conditions, soft to hard. N+T is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Soft intermediate condition used between forging operations or for heavy machining before final normalizing/quenching; not a final vessel-service condition. | 315 | 565 | 26 | 163 HB | 9 % IACS |
Normalized | Simplest A372 heat treatment for thicker, lower-stress vessel forgings where the specified minimums are met without tempering. | 415 | 655 | 20 | 197 HB | 9 % IACS |
N+TDefault Normalized and tempered | Most commonly stocked A372 Grade C condition: balanced strength, ductility and residual-stress relief for thin-walled vessel and cylinder forgings. | 420 | 625 | 22 | 187 HB | — |
Quenched and tempered | Choose when maximum allowable stress / thinnest wall is required; gives the highest and most uniform strength through section, with tempering set to keep hardness below sour-service limits. | 550 | 725 | 20 | 20 HRC | — |
What is A372 Grade C?
A372 Grade C is a higher-strength carbon steel forging grade of the ASTM A372 series, with increased carbon and manganese content for greater allowable stress in thin-walled pressure vessels. Supplied normalized, normalized-and-tempered, quenched-and-tempered or annealed, it typically shows 420 MPa yield, 625 MPa tensile, 22 % elongation and 187 HB (91 HRB), and is used for forged and hot-spun cylinder bodies and closures. Cold formability and machinability are limited by the medium carbon content, service temperature is capped at 400 °C, and welding requires preheat and PWHT. Grade B is the nearest alternative when easier fabrication matters more. A372 Grade C has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). A372 Grade C has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is A372 Grade C used for?
- High-pressure gas cylinders
- Pressure vessel forgings
- Aerospace bottle shells
Advantages
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
Limitations
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
A372 Grade C properties
Typical room-temperature values for A372 Grade C-N+T; bars are the position among steel grades.
Physical3
A372 Grade C has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
A372 Grade C has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade C is rated for continuous service to 400°C (752 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A372 Grade C conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of A372 Grade C takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
A372 Grade C's machinability is good (55/100, better than 62% of steel grades); weldability fair (45/100); formability fair (40/100).
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. A372 Grade C is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A372 Grade C
Is A372 Grade C easy to machine?
Machines like 1045-class C-Mn steel at ~55–60 % of 1212; rough-machine in annealed/normalized state, finish after final heat treatment with rigid setups and carbide tooling.
Can A372 Grade C be welded?
Weldable with low-hydrogen SMAW/SAW consumables but CE is high — use 150–250 °C preheat, control interpass, and apply PWHT at ~600–650 °C; avoid welding on quenched-and-tempered vessel walls without requalification.
Can A372 Grade C be formed, bent or molded?
Designed for hot forging/hot spinning of vessel bodies and closures (typ. 1100–1230 °C); cold formability is limited by the medium carbon content — bend radii should be generous.
A372 Grade C 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 |
|---|---|---|
| Chigher C than Grades A/B for increased strength | ≤ 0.48 | 0.42 |
| Mn | 0.6 – 1.65 | 1.2 |
| Sikilled steel | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Fe | balance |
What surface finishes work on A372 Grade C?
No anodizing; protect with shot blast + epoxy/zinc-rich paint, phosphate + oil, or galvanizing, and use internal coatings/liners for wet or sour gas service.
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
How much does A372 Grade C cost?
A372 Grade C 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.
A372 Grade C — frequently asked
What is A372 Grade C used for?
A372 Grade C is typically used for high-pressure gas cylinders, pressure vessel forgings and aerospace bottle shells. In short: higher-carbon A372 forging; hot-spun cylinder grade; stronger than A372 Grade A.
What is the yield strength of A372 Grade C?
A372 Grade C has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A372 Grade C easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like 1045-class C-Mn steel at ~55–60 % of 1212; rough-machine in annealed/normalized state, finish after final heat treatment with rigid setups and carbide tooling.
Can A372 Grade C be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen SMAW/SAW consumables but CE is high — use 150–250 °C preheat, control interpass, and apply PWHT at ~600–650 °C; avoid welding on quenched-and-tempered vessel walls without requalification.
What surface finishes work on A372 Grade C?
No anodizing; protect with shot blast + epoxy/zinc-rich paint, phosphate + oil, or galvanizing, and use internal coatings/liners for wet or sour gas service.
Can A372 Grade C be formed, bent or molded?
Designed for hot forging/hot spinning of vessel bodies and closures (typ. 1100–1230 °C); cold formability is limited by the medium carbon content — bend radii should be generous.
What is the maximum service temperature of A372 Grade C?
A372 Grade C 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.
What is the difference between A372 Grade C N+T and A372 Grade C-QT?
N+T is the default condition — most commonly stocked A372 Grade C condition: balanced strength, ductility and residual-stress relief for thin-walled vessel and cylinder forgings. QT: choose when maximum allowable stress / thinnest wall is required; gives the highest and most uniform strength through section, with tempering set to keep hardness below sour-service limits. Yield strength is 420 MPa in N+T versus 550 MPa in QT.
How much does A372 Grade C cost?
A372 Grade C 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 A372/A372M — Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels — ASTM International (2020)
- ASME BPVC Section II Part D — Material 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)
- ASTM A370 — Mechanical Testing of Steel Products (hardness conversions) — ASTM International (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.