Steel T6 HT-65
Heat-treated state
AISI/SAE T6 · UNS T12006
HT-65 = hardened & tempered
Full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials.
Values for the HT-65 condition
Other T6 tempers and conditions
T6 is listed in 3 conditions; see the grade overview at T6.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard mill-supplied bar/blank condition for machining tool blanks before hardening. | 590 | 900 | 12 | 262 HB | 22 W/m·K |
HT-65This page Hardened & tempered | Full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials. | 2,000 | 2,200 | 0.5 | 65 HRC | 20 W/m·K |
Hardened & tempered | Choose when interrupted cuts or large tool sections demand more toughness than absolute peak hardness. | 2,000 | 2,200 | 0.5 | 63 HRC | 2.9 % IACS |
What is T6 HT-65?
T6 HT-65 is T6 heat treated to HT-65 — full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials. T6 HT-65 has a yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,200 MPa (319 ksi) — stronger than 100% of steel grades. Elongation at break is 0.5% and the elastic modulus is 225 GPa (32.6 Msi). T6 HT-65 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 100% of steel grades. It melts at 1,400°C (2,552 °F). ANN is the default condition FabDigit quotes; HT-65 is available on request or by drawing note.
Advantages
- High strength — 2,000 MPa (290 ksi), better than 100% of steel grades
- High service temperature — 620°C (1,148 °F), better than 99% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Limited ductility — 0.5%, worse than 100% of steel grades
- Heavy — 8.89 g/cm³ (0.321 lb/in³), worse than 100% of steel grades
- Difficult to machine — 5/100, worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 1/100, worse than 100% of steel grades
T6 HT-65 properties
Typical room-temperature values for T6 HT-65; 21 are specific to this condition. Other listed values are T6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
T6 HT-65 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 100% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical14
T6 HT-65 has a yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,200 MPa (319 ksi) — stronger than 100% of steel grades. Elongation at break is 0.5% and the elastic modulus is 225 GPa (32.6 Msi).
Thermal6
T6 HT-65 is rated for continuous service to 620°C (1,148 °F). It conducts heat at 20 W/m·K (11.6 BTU/hr·ft·°F), worse than 96% of steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
T6 HT-65 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of T6 HT-65 takes about 90 MJ of energy and emits 6.5 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 40%.
Manufacturability8
T6 HT-65's machinability is not recommended (5/100, worse than 100% of steel grades); weldability not recommended (5/100); formability not recommended (1/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with T6 HT-65
Is T6 easy to machine?
Machine only in the annealed condition with rigid setups, sharp carbide or cobalt-HSS tools and generous coolant; hardened T6 must be ground or EDM'd, and grinding requires soft, friable wheels to avoid burn/cracking.
Can T6 be welded?
Not a structural weld grade — repair only, with 500–550 °C preheat, matching HSS filler and immediate re-temper; otherwise cracking is near certain.
Can T6 be formed, bent or molded?
Hot work at 1000–1150 °C with slow, controlled cooling and immediate annealing; no meaningful cold forming, and the coarse tungsten carbide network makes it crack-sensitive.
What surface finishes work on T6?
Steam oxide, black oxide, nitriding or PVD TiN/TiAlN are standard; the alloy rusts without a coating or oil film, and mirror polishing is limited by primary carbides.
T6 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 |
|---|---|---|
| C | 0.75 – 0.85 | 0.8 |
| Mn | 0.2 – 0.4 | 0.3 |
| Si | 0.2 – 0.4 | 0.3 |
| Cr | 3.75 – 4.5 | 4.1 |
| Wprimary carbide former, red hardness | 18.5 – 21 | 20 |
| V | 1.5 – 2.1 | 1.8 |
| Cohighest Co of the T-series; maximum hot hardness | 11 – 13 | 12 |
| Mo | 0.4 – 1 | 0.7 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
T6 HT-65 — frequently asked
What is T6 HT-65 used for?
T6 HT-65 is typically used for heavy interrupted cuts, high-speed lathe tools, milling cutters for hard alloys and hot forming tools. In short: highest red-hardness tungsten HSS; 12% cobalt grade; crack-sensitive, hard to grind.
What is the yield strength of T6 HT-65?
T6 HT-65 has a typical yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,200 MPa (319 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is T6 HT-65 easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 100% of steel grades). Machine only in the annealed condition with rigid setups, sharp carbide or cobalt-HSS tools and generous coolant; hardened T6 must be ground or EDM'd, and grinding requires soft, friable wheels to avoid burn/cracking.
Can T6 HT-65 be welded?
Not readily — weldability is rated not recommended (5/100). Not a structural weld grade — repair only, with 500–550 °C preheat, matching HSS filler and immediate re-temper; otherwise cracking is near certain.
What surface finishes work on T6 HT-65?
Steam oxide, black oxide, nitriding or PVD TiN/TiAlN are standard; the alloy rusts without a coating or oil film, and mirror polishing is limited by primary carbides.
Can T6 HT-65 be formed, bent or molded?
Hot work at 1000–1150 °C with slow, controlled cooling and immediate annealing; no meaningful cold forming, and the coarse tungsten carbide network makes it crack-sensitive.
What is the maximum service temperature of T6 HT-65?
T6 HT-65 is rated for continuous use to about 620°C (1,148 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between T6-ANN and T6 HT-65?
ANN is the default condition — standard mill-supplied bar/blank condition for machining tool blanks before hardening. HT-65: full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials. Yield strength is 590 MPa in ANN versus 2,000 MPa in HT-65.
Sources
- ASTM A600 — Tool Steel, High Speed, Tool and Die Steels — ASTM International (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
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.