Steel T7-QT57
Hardness band
AISI/SAE T7 · GB T7A
QT57 = water quenched + 200–250 °C temper
Balanced hardness/toughness setting for cold chisels, punches and riveting tools.
Values for the QT57 condition
Other T7 tempers and conditions
T7 is listed in 8 conditions; see the grade overview at T7.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard delivery condition for bar and flat stock; softest, best machinability, ready for machining then hardening. | 400 | 660 | 22 | 183 HB | 48 W/m·K |
High-grade quality | Same carbon range with tighter sulphur/phosphorus limits and cleaner steel — choose for tools that must survive repeated heavy impact. | 405 | 670 | 24 | 11 HRC | 9.5 % IACS |
Hot rolled | As-rolled bar with mill scale; cheapest form, normally annealed before machining. | 430 | 780 | 14 | 20 HRC | 9.5 % IACS |
Normalized | Used to refine grain and break up network carbide before spheroidizing or hardening. | 450 | 800 | 15 | 22 HRC | 9.5 % IACS |
Cold drawn | Bright drawn bar with close tolerance and good surface for direct machining of small tools. | 640 | 820 | 9 | 23 HRC | 9.5 % IACS |
Water quenched + 300–400 °C temper | Toughest hardened setting — for heavy-impact chisels, pneumatic tool bits and spring-like sections. | 1,400 | 1,600 | 6 | 48 HRC | — |
QT57This page Water quenched + 200–250 °C temper | Balanced hardness/toughness setting for cold chisels, punches and riveting tools. | 1,650 | 1,950 | 2 | 57 HRC | 8.5 % IACS |
Water quenched + 150–180 °C temper | Maximum hardness condition for cutting edges on chisels and punches where wear matters more than shock. | — | 2,100 | — | 61 HRC | 44 W/m·K |
What is T7-QT57?
T7-QT57 is T7 heat treated to QT57 — balanced hardness/toughness setting for cold chisels, punches and riveting tools. T7-QT57 has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 205 GPa (29.7 Msi). T7-QT57 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F). A is the default condition FabDigit quotes; QT57 is available on request or by drawing note.
Advantages
- High strength — 1,650 MPa (239 ksi), better than 99% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Difficult to machine — 10/100, worse than 99% of steel grades
- Limited formability — 3/100, worse than 99% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
T7-QT57 properties
Typical room-temperature values for T7-QT57; 22 are specific to this condition. Other listed values are T7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
T7-QT57 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
T7-QT57 has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
T7-QT57 is rated for continuous service to 200°C (392 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
T7-QT57 conducts electricity at 8.5 % IACS, better than 63% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of T7-QT57 takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
T7-QT57's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with T7-QT57
Is T7 easy to machine?
Machine in the spheroidize-annealed condition (~62 % of AISI 1212) with HSS or coated carbide; once hardened above 55 HRC only grinding or EDM is practical.
Can T7 be welded?
Poor weldability — high carbon promotes martensite and quench cracking; if unavoidable, preheat 300–400 °C, use low-hydrogen or Ni-base filler and temper immediately after.
Can T7 be formed, bent or molded?
Forge 1050–1150 °C and stop above 800 °C, then slow cool; cold bending only in the annealed state with generous radii.
What surface finishes work on T7?
Grind and polish after hardening, then protect with black oxide, phosphating, oiling or hard chrome — the steel has no intrinsic corrosion resistance.
T7 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 |
|---|---|---|
| CGB/T 1298 | 0.65 – 0.74 | 0.7 |
| Si | ≤ 0.35 | 0.22 |
| Mn | ≤ 0.4 | 0.25 |
| PT7A ≤0.030 | ≤ 0.04 | — |
| ST7A ≤0.020 | ≤ 0.03 | — |
| Crresidual; ≤0.10 for some deliveries | ≤ 0.25 | — |
| Niresidual | ≤ 0.2 | — |
| Curesidual; ≤0.25 for T7A | ≤ 0.3 | — |
| Fe | balance | — |
T7-QT57 — frequently asked
What is T7-QT57 used for?
T7-QT57 is typically used for chisels, hammers, punches and hand tools. In short: toughest carbon tool steel; impact-tool carbon grade; lowest carbon of T-series.
What is the yield strength of T7-QT57?
T7-QT57 has a typical yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is T7-QT57 easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine in the spheroidize-annealed condition (~62 % of AISI 1212) with HSS or coated carbide; once hardened above 55 HRC only grinding or EDM is practical.
Can T7-QT57 be welded?
Not readily — weldability is rated not recommended (5/100). Poor weldability — high carbon promotes martensite and quench cracking; if unavoidable, preheat 300–400 °C, use low-hydrogen or Ni-base filler and temper immediately after.
What surface finishes work on T7-QT57?
Grind and polish after hardening, then protect with black oxide, phosphating, oiling or hard chrome — the steel has no intrinsic corrosion resistance.
Can T7-QT57 be formed, bent or molded?
Forge 1050–1150 °C and stop above 800 °C, then slow cool; cold bending only in the annealed state with generous radii.
What is the maximum service temperature of T7-QT57?
T7-QT57 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between T7-A and T7-QT57?
A is the default condition — standard delivery condition for bar and flat stock; softest, best machinability, ready for machining then hardening. QT57: balanced hardness/toughness setting for cold chisels, punches and riveting tools. Yield strength is 400 MPa in A versus 1,650 MPa in QT57.
Sources
- GB/T 1299 (heat treatment and hardness requirements) — SAC (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (W-type water-hardening tool steels) — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
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.