Steel T7
AISI/SAE T7 · GB T7A
T7 is an unalloyed water-hardening carbon tool steel from the Chinese GB/T 1298 T-series, and at roughly 0.65–0.74 % C it is the lowest-carbon, toughest member, trading wear resistance for impact resistance.
Reference datasheet — T7 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 A condition
T7 tempers and conditions
T7 is supplied in 8 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
T7 is an unalloyed water-hardening carbon tool steel from the Chinese GB/T 1298 T-series, and at roughly 0.65–0.74 % C it is the lowest-carbon, toughest member, trading wear resistance for impact resistance. It is used for shock-loaded edges and is stocked as annealed, hot-rolled, normalized and cold-drawn bar, in QT60, QT57 and QT50 quench-and-temper conditions, and as the cleaner T7A variant. Annealed values are 400 MPa yield, 660 MPa tensile, 22 % elongation, 183 HB and 48 W/m·K thermal conductivity. Hardening depth is shallow and requires a water quench; choose T8 or T10 for more wear resistance, or an alloy tool steel when distortion control matters. T7 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). T7 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 660 MPa (95.7 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
What is T7 used for?
- chisels
- hammers
- punches
- hand tools
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- 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
Limitations
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
T7 properties
Typical room-temperature values for T7-A; bars are the position among steel grades.
Physical3
T7 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 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 660 MPa (95.7 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
T7 is rated for continuous service to 250°C (482 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
T7 conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of T7 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's machinability is good (60/100, better than 83% of steel grades); weldability poor (15/100); formability fair (45/100).
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. T7 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with T7
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.
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 |
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.
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 T7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- GB (China)
- T7A
How much does T7 cost?
T7 is a budget-cost steel ($), cheaper than about 90% 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.
T7 — frequently asked
What is T7 used for?
T7 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?
T7 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 660 MPa (95.7 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is T7 easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% 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 be welded?
Not readily — weldability is rated poor (15/100). 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?
Grind and polish after hardening, then protect with black oxide, phosphating, oiling or hard chrome — the steel has no intrinsic corrosion resistance.
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 is the maximum service temperature of T7?
T7 is rated for continuous use to about 250°C (482 °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.
How much does T7 cost?
T7 is a budget-cost steel ($), cheaper than about 90% 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
- 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; 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.