Steel A372 Grade B
ASTM A372 Grade B
A372 Grade B is a medium-strength carbon steel forging grade in the ASTM A372 series, normally supplied quenched-and-tempered or normalized-and-tempered for thin-walled pressure vessel components.
Reference datasheet — A372 Grade B 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 Q&T condition
A372 Grade B tempers and conditions
A372 Grade B is supplied in 4 conditions, soft to hard. Q&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 |
|---|---|---|---|---|---|---|
full anneal (intermediate/machining condition) | Not a final A372 delivery condition; used for rough-machining or re-forging blanks before final normalizing/quench-and-temper. | 300 | 540 | 28 | 156 HB | — |
Normalized | Simplest permitted heat treatment; used when the specified minimums are met without tempering and residual-stress control is less critical. | 405 | 610 | 23 | 183 HB | 10 % IACS |
Normalized and tempered | Choose for larger or complex forgings where quench distortion/cracking is a risk; slightly lower strength and toughness than Q&T. | 425 | 620 | 24 | 187 HB | — |
Q&TDefault Quenched and tempered | Standard delivery condition for thin-wall forged cylinders and accumulator shells; best strength/toughness combination for A372 Gr. B. | 470 | 655 | 22 | 197 HB | — |
What is A372 Grade B?
A372 Grade B is a medium-strength carbon steel forging grade in the ASTM A372 series, normally supplied quenched-and-tempered or normalized-and-tempered for thin-walled pressure vessel components. It delivers 470 MPa yield, 655 MPa tensile, 22 % elongation and 197 HB (93 HRB), so it carries more pressure than Grade A in the same wall thickness. Machinability drops to about 55 on the 1212 scale, service is limited to 400 °C, and welding needs preheat plus PWHT because the carbon equivalent reaches 0.5–0.6. At these strength levels hydrogen embrittlement during pickling or plating must be controlled. A372 Grade B 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). A372 Grade B has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 655 MPa (95 ksi) — stronger than 57% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is A372 Grade B used for?
- Gas cylinders
- Pressure vessel end closures
- High-pressure accumulators
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
A372 Grade B properties
Typical room-temperature values for A372 Grade B-Q&T; bars are the position among steel grades.
Physical3
A372 Grade B 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
A372 Grade B has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 655 MPa (95 ksi) — stronger than 57% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade B 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 µm/m·K (6.67 µin/in·°F).
Electrical3
A372 Grade B conducts electricity at 10 % IACS, better than 83% 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 B takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
A372 Grade B's machinability is good (55/100, better than 62% of steel grades); weldability good (55/100); 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 B is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A372 Grade B
Is A372 Grade B easy to machine?
Machines like Q&T 1035–1045: rigid setups, carbide inserts at 90–140 m/min, flood coolant; rough-machine soft and finish after final heat treatment to control distortion.
Can A372 Grade B be welded?
CE ≈ 0.5–0.6, so preheat 150–250 °C, low-hydrogen consumables and PWHT at 590–650 °C; keep interpass temperature controlled to avoid hard HAZ and hydrogen cracking.
Can A372 Grade B be formed, bent or molded?
Designed for hot forging/back-extrusion of seamless thin-wall shells at 1100–1250 °C, finishing above ~900 °C; cold forming is limited to gentle bends with generous radii.
A372 Grade B 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 |
|---|---|---|
| Cladle analysis, carbon-steel grade | ≤ 0.35 | 0.3 |
| Mn | 0.6 – 1.35 | 1 |
| Sikilled steel | 0.15 – 0.35 | 0.25 |
| Pmax per current ASTM A372 edition | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on A372 Grade B?
No inherent corrosion resistance — shot blast plus epoxy/zinc-rich paint, phosphate or hot-dip/electroless coating; avoid electroplating without baking due to hydrogen embrittlement risk at these strength levels.
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 B cost?
A372 Grade B 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 B — frequently asked
What is A372 Grade B used for?
A372 Grade B is typically used for gas cylinders, pressure vessel end closures and high-pressure accumulators. In short: mid-strength A372 forging; stronger than A372 Grade A; Q&T thin-wall vessel steel.
What is the yield strength of A372 Grade B?
A372 Grade B has a typical yield strength of 470 MPa (68.2 ksi) and a tensile strength of 655 MPa (95 ksi) — stronger than 57% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A372 Grade B easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like Q&T 1035–1045: rigid setups, carbide inserts at 90–140 m/min, flood coolant; rough-machine soft and finish after final heat treatment to control distortion.
Can A372 Grade B be welded?
Yes — weldability is rated good (55/100). CE ≈ 0.5–0.6, so preheat 150–250 °C, low-hydrogen consumables and PWHT at 590–650 °C; keep interpass temperature controlled to avoid hard HAZ and hydrogen cracking.
What surface finishes work on A372 Grade B?
No inherent corrosion resistance — shot blast plus epoxy/zinc-rich paint, phosphate or hot-dip/electroless coating; avoid electroplating without baking due to hydrogen embrittlement risk at these strength levels.
Can A372 Grade B be formed, bent or molded?
Designed for hot forging/back-extrusion of seamless thin-wall shells at 1100–1250 °C, finishing above ~900 °C; cold forming is limited to gentle bends with generous radii.
What is the maximum service temperature of A372 Grade B?
A372 Grade B 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 B Q&T and A372 Grade B-N?
Q&T is the default condition — standard delivery condition for thin-wall forged cylinders and accumulator shells; best strength/toughness combination for A372 Gr. B. N: simplest permitted heat treatment; used when the specified minimums are met without tempering and residual-stress control is less critical. Yield strength is 470 MPa in Q&T versus 405 MPa in N.
How much does A372 Grade B cost?
A372 Grade B 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 Standard Specification for Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels — ASTM International (2021)
- 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 Test Methods and Definitions for 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.