Steel A372 Grade D-QT (Quenched and tempered)
Heat-treated state · default condition
ASTM A372 Grade D
The standard delivery condition for Grade D forgings; use when full specified 690/515 MPa pressure-vessel properties are required.
Values for the QT condition
Other A372 Grade D tempers and conditions
A372 Grade D is listed in 3 conditions; see the grade overview at A372 Grade D.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition, used for rough machining or deep boring of shells before final Q&T of the finished forging. | 310 | 570 | 23 | 6 HRC | 10 % IACS |
Normalized | Grain-refined pre-heat-treat condition of rough forgings before the final quench and temper; not acceptable as final Grade D delivery state. | 350 | 640 | 20 | 11 HRC | 9.8 % IACS |
QTDefaultThis page Quenched and tempered | The standard delivery condition for Grade D forgings; use when full specified 690/515 MPa pressure-vessel properties are required. | 550 | 725 | 18 | 20 HRC | — |
What is A372 Grade D-QT?
A372 Grade D-QT is A372 Grade D heat treated to QT — the standard delivery condition for Grade D forgings; use when full specified 690/515 MPa pressure-vessel properties are required. A372 Grade D-QT has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 725 MPa (105 ksi) — stronger than 71% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). A372 Grade D-QT 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).
Advantages
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
A372 Grade D-QT properties
Typical room-temperature values for A372 Grade D-QT; 11 are specific to this condition. Other listed values are A372 Grade D reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A372 Grade D-QT 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).
Mechanical17
A372 Grade D-QT has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 725 MPa (105 ksi) — stronger than 71% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A372 Grade D-QT is rated for continuous service to 400°C (752 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A372 Grade D-QT conducts electricity at 9.5 % IACS, better than 75% 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 D-QT takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
A372 Grade D-QT's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A372 Grade D-QT
Is A372 Grade D easy to machine?
Machine in the annealed or normalized state where possible; at 200–250 HB use rigid setups, carbide inserts at ~120–180 m/min and generous coolant to control work hardening on bores.
Can A372 Grade D be welded?
Weldable with low-hydrogen consumables but the ~0.6 carbon equivalent demands 150–260 °C preheat and PWHT; any welding after quench-and-temper needs re-qualification of properties.
Can A372 Grade D be formed, bent or molded?
Shaped by hot forging/back-extrusion of thin-walled shells at 1100–1200 °C; cold forming of the Q&T material is essentially limited to light straightening.
What surface finishes work on A372 Grade D?
No corrosion resistance of its own — shot blast then paint, zinc-rich primer, phosphate-and-oil or plating; keep plating baths and pickling controlled to avoid hydrogen embrittlement and bake after plating.
A372 Grade D 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; heat analysis per ASTM A372 carbon grades | 0.35 – 0.5 | 0.45 |
| Mn | 0.6 – 1.1 | 0.85 |
| Sikilled steel | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Fe | balance | — |
A372 Grade D-QT — frequently asked
What is A372 Grade D-QT used for?
A372 Grade D-QT is typically used for high-pressure gas cylinders, rocket motor cases and pressure vessel forgings requiring max strength. In short: strongest basic A372 carbon grade; Q&T high-pressure forging steel; lowest-ductility A372 grade.
What is the yield strength of A372 Grade D-QT?
A372 Grade D-QT has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 725 MPa (105 ksi) — stronger than 71% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A372 Grade D-QT easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine in the annealed or normalized state where possible; at 200–250 HB use rigid setups, carbide inserts at ~120–180 m/min and generous coolant to control work hardening on bores.
Can A372 Grade D-QT be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but the ~0.6 carbon equivalent demands 150–260 °C preheat and PWHT; any welding after quench-and-temper needs re-qualification of properties.
What surface finishes work on A372 Grade D-QT?
No corrosion resistance of its own — shot blast then paint, zinc-rich primer, phosphate-and-oil or plating; keep plating baths and pickling controlled to avoid hydrogen embrittlement and bake after plating.
Can A372 Grade D-QT be formed, bent or molded?
Shaped by hot forging/back-extrusion of thin-walled shells at 1100–1200 °C; cold forming of the Q&T material is essentially limited to light straightening.
What is the maximum service temperature of A372 Grade D-QT?
A372 Grade D-QT 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 D-QT and A372 Grade D-A?
QT is the default condition — the standard delivery condition for Grade D forgings; use when full specified 690/515 MPa pressure-vessel properties are required. A: softest condition, used for rough machining or deep boring of shells before final Q&T of the finished forging. Yield strength is 550 MPa in QT versus 310 MPa in A.
Sources
- ASTM A372/A372M — Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels — ASTM International (2020)
- 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 conversion tables) — ASTM International (2022)
- ASME BPVC Section II Part D / Section VIII Div. 1 — ASME (2023)
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.