Steel A372 Grade A-QT (Quenched and tempered)
Heat-treated state
ASTM A372 Grade A
Optional for thin sections where higher yield and better toughness than normalized are wanted while keeping Grade A chemistry.
Values for the QT condition
Other A372 Grade A tempers and conditions
A372 Grade A is listed in 5 conditions; see the grade overview at A372 Grade A.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for heavy machining, deep cold forming or re-forging; strength may fall below the A372 spec minima until re-normalized. | 250 | 460 | 32 | 130 HB | — |
As-forged | Intermediate mill condition only — properties are non-uniform and A372 requires subsequent normalizing or Q&T before acceptance. | 290 | 520 | 22 | 160 HB | 10 % IACS |
Normalized and tempered | Pick when residual stresses and hardness scatter must be tightened (e.g. NACE hardness cap, machining stability). | 295 | 510 | 28 | 148 HB | 10 % IACS |
NDefault Normalized | Standard supply condition for A372 Grade A thin-walled cylinder forgings; uniform fine grain, meets 485/248 MPa minima. | 300 | 530 | 26 | 155 HB | — |
QTThis page Quenched and tempered | Optional for thin sections where higher yield and better toughness than normalized are wanted while keeping Grade A chemistry. | 420 | 600 | 23 | 185 HB | 9.5 % IACS |
What is A372 Grade A-QT?
A372 Grade A-QT is A372 Grade A heat treated to QT — optional for thin sections where higher yield and better toughness than normalized are wanted while keeping Grade A chemistry. A372 Grade A-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Elongation at break is 23% and the elastic modulus is 200 GPa (29 Msi). A372 Grade A-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). N is the default condition FabDigit quotes; QT is available on request or by drawing note.
Advantages
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
A372 Grade A-QT properties
Typical room-temperature values for A372 Grade A-QT; 22 are specific to this condition. Other listed values are A372 Grade A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A372 Grade A-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).
Mechanical16
A372 Grade A-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Elongation at break is 23% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
A372 Grade A-QT is rated for continuous service to 425°C (797 °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 A-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 A-QT takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability8
A372 Grade A-QT's machinability is good (55/100, better than 62% of steel grades); weldability very good (70/100); formability fair (48/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A372 Grade A-QT
Is A372 Grade A easy to machine?
Machines like normalized 1030–1035: ~60 % of 1212, carbide inserts at 150–200 m/min, good chip control in the normalized state.
Can A372 Grade A be welded?
Readily welded by SMAW/GMAW/SAW with E70-class consumables; CE ≈0.45 so preheat 100–150 °C for sections over ~25 mm and PWHT per ASME as required.
Can A372 Grade A be formed, bent or molded?
Hot forged 1100–1250 °C then normalized; cold expansion/necking of thin cylinder walls is feasible in the annealed or normalized state with generous bend radii.
What surface finishes work on A372 Grade A?
No anodizing — protect with shot blast + zinc/epoxy paint, phosphate or electroless nickel; bare surfaces flash-rust within hours in humid air.
A372 Grade A 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 |
|---|---|---|
| Ccarbon-steel Grade A | ≤ 0.35 | 0.3 |
| Mn | 0.6 – 0.9 | 0.75 |
| Si | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Fe | balance | — |
A372 Grade A-QT — frequently asked
What is A372 Grade A-QT used for?
A372 Grade A-QT is typically used for gas cylinders, thin-wall pressure vessel forgings and accumulator shells. In short: most weldable A372 grade; lowest-strength A372 forging; easiest-forming cylinder steel.
What is the yield strength of A372 Grade A-QT?
A372 Grade A-QT has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is A372 Grade A-QT easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like normalized 1030–1035: ~60 % of 1212, carbide inserts at 150–200 m/min, good chip control in the normalized state.
Can A372 Grade A-QT be welded?
Yes — weldability is rated very good (70/100). Readily welded by SMAW/GMAW/SAW with E70-class consumables; CE ≈0.45 so preheat 100–150 °C for sections over ~25 mm and PWHT per ASME as required.
What surface finishes work on A372 Grade A-QT?
No anodizing — protect with shot blast + zinc/epoxy paint, phosphate or electroless nickel; bare surfaces flash-rust within hours in humid air.
Can A372 Grade A-QT be formed, bent or molded?
Hot forged 1100–1250 °C then normalized; cold expansion/necking of thin cylinder walls is feasible in the annealed or normalized state with generous bend radii.
What is the maximum service temperature of A372 Grade A-QT?
A372 Grade A-QT is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A372 Grade A-N and A372 Grade A-QT?
N is the default condition — standard supply condition for A372 Grade A thin-walled cylinder forgings; uniform fine grain, meets 485/248 MPa minima. QT: optional for thin sections where higher yield and better toughness than normalized are wanted while keeping Grade A chemistry. Yield strength is 300 MPa in N versus 420 MPa in QT.
Sources
- ASTM A372/A372M — Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels — ASTM International (2020)
- ASME BPVC Section II Part D — Material Properties — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASTM A370 — 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.