Steel M33 HT63-65
Hardness band
AISI/SAE M33 · UNS T11333
HT63-65 = hardened & triple tempered
General working condition for cutting tools: best balance of red hardness and residual toughness.
Values for the HT63-65 condition
Other M33 tempers and conditions
M33 is listed in 3 conditions; see the grade overview at M33.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard stock condition for bar, blanks and preforms; machine or grind to shape before hardening. | 550 | 880 | 20 | 240 HB | — |
HT63-65This page Hardened & triple tempered | General working condition for cutting tools: best balance of red hardness and residual toughness. | 1,950 | 2,150 | 1 | 64 HRC | 23 W/m·K |
Hardened & tempered to maximum hardness | Pick for maximum hot hardness and wear life on abrasive/high-speed work where edge chipping risk is acceptable. | — | 2,250 | 0.5 | 66 HRC | — |
What is M33 HT63-65?
M33 HT63-65 is M33 heat treated to HT63-65 — general working condition for cutting tools: best balance of red hardness and residual toughness. M33 HT63-65 has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,150 MPa (312 ksi) — stronger than 100% of steel grades. Elongation at break is 1% and the elastic modulus is 225 GPa (32.6 Msi). M33 HT63-65 has a density of 8.03 g/cm³ (0.29 lb/in³), heavier than 96% of steel grades. It melts at 1,230°C (2,246 °F). ANN is the default condition FabDigit quotes; HT63-65 is available on request or by drawing note.
Advantages
- High strength — 1,950 MPa (283 ksi), better than 100% of steel grades
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Polishes to a fine finish — 78/100, better than 95% of steel grades
Limitations
- Low fracture toughness — 15 MPa·√m (13.7 ksi·√in), worse than 100% of steel grades
- Difficult to machine — 6/100, worse than 100% of steel grades
- Limited formability — 2/100, worse than 100% of steel grades
- Limited ductility — 1%, worse than 99% of steel grades
- Difficult to weld — 8/100, worse than 99% of steel grades
M33 HT63-65 properties
Typical room-temperature values for M33 HT63-65; 20 are specific to this condition. Other listed values are M33 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M33 HT63-65 has a density of 8.03 g/cm³ (0.29 lb/in³), heavier than 96% of steel grades. It melts at 1,230°C (2,246 °F).
Mechanical16
M33 HT63-65 has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,150 MPa (312 ksi) — stronger than 100% of steel grades. Elongation at break is 1% and the elastic modulus is 225 GPa (32.6 Msi).
Thermal6
M33 HT63-65 is rated for continuous service to 600°C (1,112 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades. Thermal expansion is 10.6 µm/m·K (5.89 µin/in·°F).
Electrical3
M33 HT63-65 conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of M33 HT63-65 takes about 62 MJ of energy and emits 4.6 kg of CO₂ — more than 96% of steel grades. Typical recycled content is 35%.
Manufacturability8
M33 HT63-65's machinability is not recommended (6/100, worse than 100% of steel grades); weldability not recommended (8/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M33 HT63-65
Is M33 easy to machine?
Machine only in the annealed condition with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and generous coolant; after hardening it is a grind-only material (soft, friable CBN/SG wheels, avoid grinding burn).
Can M33 be welded?
Not a structural weld metal — repair only, with 500–550 °C preheat, matching HSS filler, and immediate re-temper at 550 °C to avoid quench cracking.
Can M33 be formed, bent or molded?
No cold forming; hot work between about 1100 °C and 900 °C followed by slow furnace cooling and full spheroidize anneal (860–900 °C, 15–25 °C/h to 700 °C).
What surface finishes work on M33?
Cannot be anodized; use steam oxide, black oxide, nitriding or PVD TiN/TiAlN over a fine-ground surface, and oil/VCI-wrap for storage since the 4% Cr gives no rust protection.
M33 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 | 0.85 – 0.92 | 0.89 |
| Mn | 0.15 – 0.4 | 0.28 |
| Si | 0.15 – 0.5 | 0.3 |
| Cr | 3.5 – 4 | 3.75 |
| Mo | 9 – 10 | 9.5 |
| W | 1.3 – 2.1 | 1.7 |
| V | 1 – 1.35 | 1.15 |
| Coprovides hot hardness | 7.75 – 8.75 | 8.25 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
M33 HT63-65 — frequently asked
What is M33 HT63-65 used for?
M33 HT63-65 is typically used for high-speed turning, hard alloy machining and heavy interrupted cuts. In short: high-cobalt hot hardness; 500 °C service rating; for severe high-speed cutting.
What is the yield strength of M33 HT63-65?
M33 HT63-65 has a typical yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,150 MPa (312 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is M33 HT63-65 easy to machine?
Not especially — machinability is rated not recommended (6/100, worse than 100% of steel grades). Machine only in the annealed condition with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and generous coolant; after hardening it is a grind-only material (soft, friable CBN/SG wheels, avoid grinding burn).
Can M33 HT63-65 be welded?
Not readily — weldability is rated not recommended (8/100). Not a structural weld metal — repair only, with 500–550 °C preheat, matching HSS filler, and immediate re-temper at 550 °C to avoid quench cracking.
What surface finishes work on M33 HT63-65?
Cannot be anodized; use steam oxide, black oxide, nitriding or PVD TiN/TiAlN over a fine-ground surface, and oil/VCI-wrap for storage since the 4% Cr gives no rust protection.
Can M33 HT63-65 be formed, bent or molded?
No cold forming; hot work between about 1100 °C and 900 °C followed by slow furnace cooling and full spheroidize anneal (860–900 °C, 15–25 °C/h to 700 °C).
What is the maximum service temperature of M33 HT63-65?
M33 HT63-65 is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between M33-ANN and M33 HT63-65?
ANN is the default condition — standard stock condition for bar, blanks and preforms; machine or grind to shape before hardening. HT63-65: general working condition for cutting tools: best balance of red hardness and residual toughness. Yield strength is 550 MPa in ANN versus 1,950 MPa in HT63-65.
Sources
- ASTM A600 — Standard Specification for Tool Steel High Speed — ASTM International (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- ASM Handbook Vol.16: Machining — ASM International (1989)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- High-speed steel grade datasheets (M-series, cobalt grades) — Erasteel / Böhler / Crucible (2022)
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.