Steel A757 Grade C3 Q&T+PWHT
Heat-treated state
ASTM A757 Grade C3
Q&T+PWHT = q&T + post-weld heat treatment
Condition for castings weld-repaired after heat treatment; re-tempered (or re-quenched and tempered) to restore HAZ toughness for certification.
Values for the Q&T+PWHT condition
Other A757 Grade C3 tempers and conditions
A757 Grade C3 is listed in 4 conditions; see the grade overview at A757 Grade C3.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Ordered when the foundry ships rough castings for machining before final heat treatment; not an A757-certifiable delivery condition. | 300 | 500 | 26 | 150 HB | 7 % IACS |
Normalized and tempered | Air-cooled alternative used for large or geometrically awkward castings; slightly lower strength and less uniform toughness than the quenched condition. | 400 | 570 | 24 | 175 HB | 6.6 % IACS |
Q&T+PWHTThis page Q&T + post-weld heat treatment | Condition for castings weld-repaired after heat treatment; re-tempered (or re-quenched and tempered) to restore HAZ toughness for certification. | 445 | 600 | 24 | 185 HB | 6.6 % IACS |
Q&TDefault Quenched and tempered | Standard A757 Grade C3 delivery condition: liquid-quenched and tempered for the best combination of strength and low-temperature notch toughness. | 460 | 620 | 24 | 190 HB | — |
What is A757 Grade C3 Q&T+PWHT?
A757 Grade C3 Q&T+PWHT is A757 Grade C3 heat treated to Q&T+PWHT — condition for castings weld-repaired after heat treatment; re-tempered (or re-quenched and tempered) to restore HAZ toughness for certification. A757 Grade C3 Q&T+PWHT has a yield strength of 445 MPa (64.5 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 51% of steel grades. Elongation at break is 24% and the elastic modulus is 202 GPa (29.3 Msi). A757 Grade C3 Q&T+PWHT 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; Q&T+PWHT is available on request or by drawing note.
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
A757 Grade C3 Q&T+PWHT properties
Typical room-temperature values for A757 Grade C3 Q&T+PWHT; 23 are specific to this condition. Other listed values are A757 Grade C3 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A757 Grade C3 Q&T+PWHT 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).
Mechanical15
A757 Grade C3 Q&T+PWHT has a yield strength of 445 MPa (64.5 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 51% of steel grades. Elongation at break is 24% and the elastic modulus is 202 GPa (29.3 Msi).
Thermal6
A757 Grade C3 Q&T+PWHT is rated for continuous service to 400°C (752 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical2
A757 Grade C3 Q&T+PWHT has an electrical resistivity of 2.6×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of A757 Grade C3 Q&T+PWHT takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 85%.
Manufacturability8
A757 Grade C3 Q&T+PWHT's machinability is good (57/100, better than 71% of steel grades); weldability good (62/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A757 Grade C3 Q&T+PWHT
Is A757 Grade C3 easy to machine?
Machines like Q&T 4130/4340-class steel at 170–220 HB — rigid setups, sharp carbide, 80–140 m/min; watch for hard spots and residual sand/scale on unfinished cast surfaces.
Can A757 Grade C3 be welded?
Readily weldable with low-hydrogen E80xx/ER80S-type consumables at 100–200 °C preheat; major weld repairs must be followed by re-tempering or full re-heat-treatment to keep low-temperature CVN values.
Can A757 Grade C3 be formed, bent or molded?
Sand or investment cast with generous risering and directional solidification; low-carbon Ni chemistry gives moderate fluidity and high solidification shrinkage (~2.2 %), so gating and feeding design govern soundness.
What surface finishes work on A757 Grade C3?
Shot blast to SA 2.5 then paint, zinc-rich primer or metallise for atmospheric/marine duty; electroless nickel or hard chrome available for wear faces — no anodising (ferrous).
A757 Grade C3 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 |
|---|---|---|
| CA757 controls properties/toughness; carbon kept low for weldability and CVN | ≤ 0.22 | 0.15 |
| Mn | 0.4 – 0.9 | 0.65 |
| Si | ≤ 0.6 | 0.35 |
| Presidual limit; low P essential for low-temperature toughness | ≤ 0.03 | 0.02 |
| Sresidual limit | ≤ 0.03 | 0.01 |
| Niclass C grades are nickel steels; indicative range — exact Ni level is by producer/purchaser agreement | 2.5 – 4.5 | 3.5 |
| Croptional hardenability addition | ≤ 0.6 | 0.2 |
| Mooptional hardenability addition | ≤ 0.35 | 0.15 |
| Vresidual/optional | ≤ 0.05 | — |
| Fe | balance | — |
A757 Grade C3 Q&T+PWHT — frequently asked
What is A757 Grade C3 Q&T+PWHT used for?
A757 Grade C3 Q&T+PWHT is typically used for structural machine castings, low-temperature service pressure parts and mining and construction equipment castings. In short: toughness-qualified steel casting; low-temperature pressure service; weldable cast alloy steel.
What is the yield strength of A757 Grade C3 Q&T+PWHT?
A757 Grade C3 Q&T+PWHT has a typical yield strength of 445 MPa (64.5 ksi) and a tensile strength of 600 MPa (87 ksi) — stronger than 51% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A757 Grade C3 Q&T+PWHT easy to machine?
Reasonably — machinability is rated good (57/100, better than 71% of steel grades). Machines like Q&T 4130/4340-class steel at 170–220 HB — rigid setups, sharp carbide, 80–140 m/min; watch for hard spots and residual sand/scale on unfinished cast surfaces.
Can A757 Grade C3 Q&T+PWHT be welded?
Yes — weldability is rated good (62/100). Readily weldable with low-hydrogen E80xx/ER80S-type consumables at 100–200 °C preheat; major weld repairs must be followed by re-tempering or full re-heat-treatment to keep low-temperature CVN values.
What surface finishes work on A757 Grade C3 Q&T+PWHT?
Shot blast to SA 2.5 then paint, zinc-rich primer or metallise for atmospheric/marine duty; electroless nickel or hard chrome available for wear faces — no anodising (ferrous).
Can A757 Grade C3 Q&T+PWHT be formed, bent or molded?
Sand or investment cast with generous risering and directional solidification; low-carbon Ni chemistry gives moderate fluidity and high solidification shrinkage (~2.2 %), so gating and feeding design govern soundness.
What is the maximum service temperature of A757 Grade C3 Q&T+PWHT?
A757 Grade C3 Q&T+PWHT 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 A757 Grade C3 Q&T and A757 Grade C3-ANN?
Q&T is the default condition — standard A757 Grade C3 delivery condition: liquid-quenched and tempered for the best combination of strength and low-temperature notch toughness. ANN: ordered when the foundry ships rough castings for machining before final heat treatment; not an A757-certifiable delivery condition. Yield strength is 460 MPa in Q&T versus 300 MPa in ANN.
Sources
- ASTM A757/A757M — Steel Castings, Ferritic and Martensitic, for Pressure-Containing and Other Applications, for Low-Temperature Service — ASTM International (2023)
- ASTM A352/A352M — Steel Castings, Ferritic and Martensitic, for Pressure-Containing Parts, Suitable for Low-Temperature Service — ASTM International (2023)
- ASTM A148/A148M — High-Strength Steel Castings for Structural Purposes — ASTM International (2019)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM International (1995)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
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.