Steel A372 Grade B-N (Normalized)
Heat-treated state
ASTM A372 Grade B
Simplest permitted heat treatment; used when the specified minimums are met without tempering and residual-stress control is less critical.
Values for the N condition
Other A372 Grade B tempers and conditions
A372 Grade B is listed in 4 conditions; see the grade overview at A372 Grade B.
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 | — |
NThis page 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-N?
A372 Grade B-N is A372 Grade B heat treated to N — simplest permitted heat treatment; used when the specified minimums are met without tempering and residual-stress control is less critical. A372 Grade B-N has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 610 MPa (88.5 ksi) — weaker than 57% of steel grades. Elongation at break is 23% and the elastic modulus is 205 GPa (29.7 Msi). A372 Grade B-N 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). Q&T is the default condition FabDigit quotes; N is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
A372 Grade B-N properties
Typical room-temperature values for A372 Grade B-N; 22 are specific to this condition. Other listed values are A372 Grade B reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A372 Grade B-N 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-N has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 610 MPa (88.5 ksi) — weaker than 57% of steel grades. Elongation at break is 23% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade B-N is rated for continuous service to 400°C (752 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
A372 Grade B-N 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-N 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-N's machinability is good (58/100, better than 75% of steel grades); weldability good (60/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A372 Grade B-N
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.
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.
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 | — |
A372 Grade B-N — frequently asked
What is A372 Grade B-N used for?
A372 Grade B-N 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-N?
A372 Grade B-N has a typical yield strength of 405 MPa (58.7 ksi) and a tensile strength of 610 MPa (88.5 ksi) — weaker than 57% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A372 Grade B-N easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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-N be welded?
Yes — weldability is rated good (60/100). 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-N?
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-N 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-N?
A372 Grade B-N 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.