Steel A372 Grade H
ASTM A372 Grade H
A372 Grade H is a mid-to-high strength class of ASTM A372 forged alloy steel, heat treated to higher tensile and yield levels than Grade G for thin-walled, high-pressure vessel applications.
Reference datasheet — A372 Grade H 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-C70 condition
A372 Grade H tempers and conditions
A372 Grade H is supplied in 3 conditions, soft to hard. QT-C70 is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Class 55 | Lowest-strength, highest-toughness class — pick where wall thickness is not weight-critical and maximum ductility/weldability is wanted. | 440 | 620 | 24 | 180 HB | — |
Class 65 | Balanced class — good compromise of strength, toughness and sour-service hardness limits for medium-pressure vessels. | 505 | 655 | 22 | 15 HRC | — |
QT-C70Default Class 70 | Most-specified class for thin-wall high-pressure cylinders and accumulators where wall thickness/weight is minimised. | 540 | 690 | 20 | 18 HRC | — |
What is A372 Grade H?
A372 Grade H is a mid-to-high strength class of ASTM A372 forged alloy steel, heat treated to higher tensile and yield levels than Grade G for thin-walled, high-pressure vessel applications. It is supplied quenched and tempered as Class 55, 65 or 70, with default values of 540 MPa yield, 690 MPa tensile, 20% elongation, about 210 HB (18 HRC / 95 HRB) and service to 400 °C. Machinability is moderate (about 55% of AISI 1212) but corrosion resistance is essentially nil and formability after heat treatment is very low; all welding requires low-hydrogen practice, 200–300 °C preheat and PWHT below the tempering temperature. A372 Grade H 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 H has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 70% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is A372 Grade H used for?
- missile motor cases
- high-pressure cylinders
- artillery components
A372 Grade H properties
Typical room-temperature values for A372 Grade H-QT-C70; bars are the position among steel grades.
Physical3
A372 Grade H 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).
Mechanical17
A372 Grade H has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 70% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade H 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 H conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of A372 Grade H takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 35%.
Manufacturability7
A372 Grade H's machinability is good (55/100, better than 62% of steel grades); weldability fair (45/100); formability poor (30/100).
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 H is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A372 Grade H
Is A372 Grade H easy to machine?
Rough machine before final temper where possible; at 190–235 HB use carbide inserts, 100–160 m/min, rigid setups and generous coolant for deep bores.
Can A372 Grade H be welded?
Low-hydrogen process only, preheat 200–300 °C, interpass control, and PWHT below the tempering temperature; qualify procedures to the vessel code.
Can A372 Grade H be formed, bent or molded?
Hot forge 1100–1230 °C with finish above 900 °C, then austenitize, quench and temper the whole forging; cold forming after Q&T is impractical.
A372 Grade H 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 Ni-Cr-Mo type per ASTM A372 Grade H; verify exact limits against current edition | 0.3 – 0.45 | 0.38 |
| Mn | 0.6 – 1 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Nialloying for hardenability/toughness | 0.4 – 1 | 0.6 |
| Cr | 0.4 – 1.1 | 0.8 |
| Mo | 0.15 – 0.3 | 0.2 |
| Fe | balance |
What surface finishes work on A372 Grade H?
Not anodizable — protect with shot blast + epoxy/zinc-rich paint, phosphate, or plating; nitriding can raise bore wear resistance if kept below the tempering temperature.
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 H in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- A372-H
How much does A372 Grade H cost?
A372 Grade H 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 H — frequently asked
What is A372 Grade H used for?
A372 Grade H is typically used for missile motor cases, high-pressure cylinders and artillery components. In short: highest A372 strength classes; missile case forging steel; machines better than Grade G.
What is the yield strength of A372 Grade H?
A372 Grade H has a typical yield strength of 540 MPa (78.3 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 70% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A372 Grade H easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Rough machine before final temper where possible; at 190–235 HB use carbide inserts, 100–160 m/min, rigid setups and generous coolant for deep bores.
Can A372 Grade H be welded?
With care — weldability is rated fair (45/100). Low-hydrogen process only, preheat 200–300 °C, interpass control, and PWHT below the tempering temperature; qualify procedures to the vessel code.
What surface finishes work on A372 Grade H?
Not anodizable — protect with shot blast + epoxy/zinc-rich paint, phosphate, or plating; nitriding can raise bore wear resistance if kept below the tempering temperature.
Can A372 Grade H be formed, bent or molded?
Hot forge 1100–1230 °C with finish above 900 °C, then austenitize, quench and temper the whole forging; cold forming after Q&T is impractical.
What is the maximum service temperature of A372 Grade H?
A372 Grade H 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 H QT-C70 and A372 Grade H QT-C55?
QT-C70 is the default condition — most-specified class for thin-wall high-pressure cylinders and accumulators where wall thickness/weight is minimised. QT-C55: lowest-strength, highest-toughness class — pick where wall thickness is not weight-critical and maximum ductility/weldability is wanted. Yield strength is 540 MPa in QT-C70 versus 440 MPa in QT-C55.
How much does A372 Grade H cost?
A372 Grade H 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 (2020)
- ASTM A370 — 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)
- NACE MR0175 / ISO 15156 — hardness limits for sour service — AMPP/ISO (2015)
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.