Steel A372 Grade J
ASTM A372 Grade J
A372 Grade J is a quenched-and-tempered low-alloy steel forging class under ASTM A372, the specification for seamless forged pressure vessels, and is on file in classes QT-CL55 through QT-CL110 as well as annealed and normalized-and-tempered.
Reference datasheet — A372 Grade J 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 QT-CL70 condition
A372 Grade J tempers and conditions
A372 Grade J is supplied in 8 conditions, soft to hard. QT-CL70 is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Soft intermediate state for rough machining or deep boring before final quench and temper. | 370 | 620 | 26 | 187 HB | — |
Class 55 | Lowest strength class — pick when toughness and weldability matter more than wall-thickness savings. | 420 | 620 | 24 | 180 HB | — |
Normalized and tempered | Alternative to Q&T for heavy sections or where the lower classes are acceptable without full quench. | 450 | 660 | 22 | 14 HRC | 8 % IACS |
Class 65 | Mid-low class for moderately loaded vessel shells with good notch toughness. | 490 | 690 | 22 | 16 HRC | — |
QT-CL70Default Class 70 | Most commonly stocked balance of strength, toughness and fabricability for seamless forged cylinders. | 520 | 720 | 20 | 18 HRC | — |
Class 85 | Intermediate high-strength class where Class 70 walls are too thick but Class 110 toughness is insufficient. | 620 | 790 | 18 | 22 HRC | — |
Class 90 | High-strength class for weight-critical accumulator and gas-cylinder forgings. | 660 | 830 | 17 | 25 HRC | — |
Class 110 | Highest common class — maximum strength-to-weight, but lowest toughness and most sensitive to hydrogen/notches. | 800 | 930 | 15 | 30 HRC | — |
What is A372 Grade J?
A372 Grade J is a quenched-and-tempered low-alloy steel forging class under ASTM A372, the specification for seamless forged pressure vessels, and is on file in classes QT-CL55 through QT-CL110 as well as annealed and normalized-and-tempered. The default condition gives 520 MPa yield, 720 MPa tensile, 20 % elongation and 215 HB (18 HRC), with service to 400 °C. Engineers specify it where a higher strength-to-weight ratio is needed than the lower letter grades provide, usually as forged, pierced and bored cylinders and closures. Weldability is limited and the steel has no inherent corrosion resistance; A372 Grade K is the next strength step. A372 Grade J 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 J has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 67% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is A372 Grade J used for?
- high-pressure vessel forgings
- ordnance forgings
- rocket casings
A372 Grade J properties
Typical room-temperature values for A372 Grade J-QT-CL70; bars are the position among steel grades.
Physical3
A372 Grade J 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 J has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 67% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade J is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A372 Grade J conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of A372 Grade J takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
A372 Grade J's machinability is good (55/100, better than 62% of steel grades); weldability fair (35/100); formability poor (28/100).
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 J is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A372 Grade J
Is A372 Grade J easy to machine?
Rough machine annealed, finish after Q&T; use rigid setups, carbide inserts and moderate speeds — chips get stringy above ~280 HB.
Can A372 Grade J be welded?
Low-hydrogen consumables with 200–300 °C preheat and mandatory PWHT; higher classes are best joined only if the standard's weld provisions allow.
Can A372 Grade J be formed, bent or molded?
Hot forge/pierce at 1100–1200 °C then quench and temper; cold forming is impractical in the hardened classes.
A372 Grade J 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 |
|---|---|---|
| Cmedium-carbon Q&T forging grade; verify exact range against current ASTM A372 Table 1 | 0.35 – 0.5 | 0.42 |
| Mn | 0.6 – 1 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| NiNi-Cr-Mo alloy class | 0.4 – 1 | 0.7 |
| Cr | 0.7 – 1.2 | 0.95 |
| Mo | 0.15 – 0.3 | 0.22 |
| Fe | balance |
What surface finishes work on A372 Grade J?
No anodizing — protect with phosphate + paint, epoxy lining or zinc plating; bake after plating to avoid hydrogen embrittlement in Class 90/110.
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 A372 Grade J in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- A372-J
How much does A372 Grade J cost?
A372 Grade J 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.
A372 Grade J — frequently asked
What is A372 Grade J used for?
A372 Grade J is typically used for high-pressure vessel forgings, ordnance forgings and rocket casings. In short: mid-strength A372 forging class; widest class range in A372; needs preheat and PWHT.
What is the yield strength of A372 Grade J?
A372 Grade J has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 67% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is A372 Grade J easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Rough machine annealed, finish after Q&T; use rigid setups, carbide inserts and moderate speeds — chips get stringy above ~280 HB.
Can A372 Grade J be welded?
With care — weldability is rated fair (35/100). Low-hydrogen consumables with 200–300 °C preheat and mandatory PWHT; higher classes are best joined only if the standard's weld provisions allow.
What surface finishes work on A372 Grade J?
No anodizing — protect with phosphate + paint, epoxy lining or zinc plating; bake after plating to avoid hydrogen embrittlement in Class 90/110.
Can A372 Grade J be formed, bent or molded?
Hot forge/pierce at 1100–1200 °C then quench and temper; cold forming is impractical in the hardened classes.
What is the maximum service temperature of A372 Grade J?
A372 Grade J 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 J QT-CL70 and A372 Grade J-ANN?
QT-CL70 is the default condition — most commonly stocked balance of strength, toughness and fabricability for seamless forged cylinders. ANN: soft intermediate state for rough machining or deep boring before final quench and temper. Yield strength is 520 MPa in QT-CL70 versus 370 MPa in ANN.
How much does A372 Grade J cost?
A372 Grade J 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 A372/A372M Standard Specification for Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels — ASTM International (2021)
- ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products (hardness conversions) — ASTM International (2022)
- 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)
- Machinery's Handbook, machinability and heat-treatment data — Industrial Press (2020)
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.