Steel T4-HT65
Heat-treated state
AISI/SAE T4 · UNS T12004
HT65 = hardened & tempered
Maximum hardness / red-hardness setting for finishing tools on hard or abrasive work; toughness is minimal.
Values for the HT65 condition
Other T4 tempers and conditions
T4 is listed in 3 conditions; see the grade overview at T4.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HT65This page Hardened & tempered | Maximum hardness / red-hardness setting for finishing tools on hard or abrasive work; toughness is minimal. | — | — | 0 | 65 HRC | 21 W/m·K |
ANNDefault Annealed | Stock condition for machining tool blanks before hardening; max 269 HB. | 580 | 950 | 12 | 255 HB | 24 W/m·K |
Hardened & tempered | Standard working hardness for general cutting tools needing a balance of edge life and toughness. | 1,900 | 2,100 | 0.5 | 63 HRC | 2.7 % IACS |
What is T4-HT65?
T4-HT65 is T4 heat treated to HT65 — maximum hardness / red-hardness setting for finishing tools on hard or abrasive work; toughness is minimal. T4-HT65 has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Elongation at break is 0% and the elastic modulus is 215 GPa (31.2 Msi). T4-HT65 has a density of 8.75 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,260°C (2,300 °F). ANN is the default condition FabDigit quotes; HT65 is available on request or by drawing note.
Advantages
- High service temperature — 620°C (1,148 °F), better than 99% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 580 MPa (84.1 ksi), better than 75% of steel grades
Limitations
- Limited ductility — 0%, worse than 100% of steel grades
- Difficult to machine — 4/100, worse than 100% of steel grades
- High embodied carbon — 5.5 kg CO₂/kg, worse than 97% of steel grades
- Poor heat conductor — 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
T4-HT65 properties
Typical room-temperature values for T4-HT65; 11 are specific to this condition. Other listed values are T4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
T4-HT65 has a density of 8.75 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,260°C (2,300 °F).
Mechanical15
T4-HT65 has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Elongation at break is 0% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
T4-HT65 is rated for continuous service to 620°C (1,148 °F). It conducts heat at 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades. Thermal expansion is 11.2 µm/m·K (6.22 µin/in·°F).
Electrical3
T4-HT65 conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of T4-HT65 takes about 75 MJ of energy and emits 5.5 kg of CO₂ — more than 97% of steel grades. Typical recycled content is 35%.
Manufacturability8
T4-HT65's machinability is not recommended (4/100, worse than 100% of steel grades); weldability poor (20/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with T4-HT65
Is T4 easy to machine?
Machine only in the annealed state with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and heavy feeds; after hardening the alloy is grind-only and grinds slower than M-series because of the coarse W/V carbides.
Can T4 be welded?
Structural welding is not practised; repair/build-up by TIG or laser with matched HSS filler at 500–550 °C preheat followed by an immediate full temper cycle.
Can T4 be formed, bent or molded?
Hot work only — forge 1100–1150 °C, stop above 950 °C and slow-cool, then anneal 860–880 °C with controlled cooling to ≤269 HB; no cold forming.
What surface finishes work on T4?
Not anodisable; use steam temper (blue oxide), black oxide, phosphating or PVD TiN/TiAlN for edge life, and keep oiled in storage since the 4 % Cr gives no rust protection.
T4 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 | 0.7 – 0.8 | 0.75 |
| Mn | 0.1 – 0.4 | 0.25 |
| Si | 0.2 – 0.4 | 0.3 |
| Cr | 3.75 – 4.5 | 4.1 |
| W | 17.5 – 19 | 18.25 |
| V | 0.8 – 1.2 | 1 |
| Cocobalt addition raises hot hardness vs T1 | 4.25 – 5.75 | 5 |
| Moresidual/optional | ≤ 1 | 0.5 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
T4-HT65 — frequently asked
What is T4-HT65 used for?
T4-HT65 is typically used for lathe tool bits, milling cutters, form tools and heavy-duty drills. In short: cobalt-boosted T1; red hardness to 500 °C; lower toughness than T1.
What is the yield strength of T4-HT65?
T4-HT65 has a typical yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is T4-HT65 easy to machine?
Not especially — machinability is rated not recommended (4/100, worse than 100% of steel grades). Machine only in the annealed state with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and heavy feeds; after hardening the alloy is grind-only and grinds slower than M-series because of the coarse W/V carbides.
Can T4-HT65 be welded?
Not readily — weldability is rated poor (20/100). Structural welding is not practised; repair/build-up by TIG or laser with matched HSS filler at 500–550 °C preheat followed by an immediate full temper cycle.
What surface finishes work on T4-HT65?
Not anodisable; use steam temper (blue oxide), black oxide, phosphating or PVD TiN/TiAlN for edge life, and keep oiled in storage since the 4 % Cr gives no rust protection.
Can T4-HT65 be formed, bent or molded?
Hot work only — forge 1100–1150 °C, stop above 950 °C and slow-cool, then anneal 860–880 °C with controlled cooling to ≤269 HB; no cold forming.
What is the maximum service temperature of T4-HT65?
T4-HT65 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 T4-ANN and T4-HT62?
ANN is the default condition — stock condition for machining tool blanks before hardening; max 269 HB. HT62: standard working hardness for general cutting tools needing a balance of edge life and toughness. Yield strength is 580 MPa in ANN versus 1,900 MPa in HT62.
Sources
- ASTM A600 — Tool Steel, High Speed — ASTM International (2021)
- GB/T 9943 (W18Cr4VCo5) — SAC / (2008)
- JIS G 4403 (SKH3) — JSA (2015)
- 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)
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.