Steel SKH2 QT64-66HRC
Hardness band
JIS SKH2 · AISI/SAE T1
QT64-66HRC = hardened & triple tempered to 64–66 HRC
Maximum wear resistance and red hardness for finishing tools on soft workpieces; least tough — avoid shock loading.
Values for the QT64-66HRC condition
Other SKH2 tempers and conditions
SKH2 is listed in 6 conditions; see the grade overview at SKH2.
- A
- QT60-62HRC
- QT-STEAM
- QT-NIT
- QT62-64HRC
- QT64-66HRC
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard mill condition for machining tool blanks before hardening. | 540 | 880 | 18 | 240 HB | — |
Hardened & triple tempered to 60–62 HRC | Lower-hardness, tougher setting for interrupted cuts, large broaches, form tools and cold-work punches. | — | 2,100 | — | 61 HRC | — |
Hardened & tempered + steam-oxide (blue) surface treatment | Choose for drills/taps where the oxide film holds lubricant and reduces built-up edge on steel. | 2,100 | 2,300 | 0.5 | 63 HRC | 2.8 % IACS |
Hardened & tempered + nitrided / PVD coated | Surface-engineered condition for higher cutting speeds and abrasive workpieces; core properties unchanged. | 2,150 | 2,350 | 0.4 | 64 HRC | 2.8 % IACS |
Hardened & triple tempered to 62–64 HRC | Standard working hardness for general-purpose lathe tools, milling cutters and drills. | — | 2,250 | — | 63 HRC | — |
QT64-66HRCThis page Hardened & triple tempered to 64–66 HRC | Maximum wear resistance and red hardness for finishing tools on soft workpieces; least tough — avoid shock loading. | — | 2,300 | — | 65 HRC | — |
What is SKH2 QT64-66HRC?
SKH2 QT64-66HRC is SKH2 heat treated to QT64-66HRC — maximum wear resistance and red hardness for finishing tools on soft workpieces; least tough — avoid shock loading. SKH2 QT64-66HRC has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 2,300 MPa (334 ksi) — stronger than 70% of steel grades. Elongation at break is 18% and the elastic modulus is 220 GPa (31.9 Msi). SKH2 QT64-66HRC has a density of 8.67 g/cm³ (0.313 lb/in³), heavier than 99% of steel grades. It melts at 1,290°C (2,354 °F). A is the default condition FabDigit quotes; QT64-66HRC is available on request or by drawing note.
Advantages
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- Good corrosion resistance — 22/100, better than 90% of steel grades
Limitations
- Difficult to machine — 5/100, worse than 100% of steel grades
- Poor heat conductor — 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades
- High embodied carbon — 3.4 kg CO₂/kg, worse than 93% of steel grades
- Limited formability — 12/100, worse than 92% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
SKH2 QT64-66HRC properties
Typical room-temperature values for SKH2 QT64-66HRC; 10 are specific to this condition. Other listed values are SKH2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SKH2 QT64-66HRC has a density of 8.67 g/cm³ (0.313 lb/in³), heavier than 99% of steel grades. It melts at 1,290°C (2,354 °F).
Mechanical14
SKH2 QT64-66HRC has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 2,300 MPa (334 ksi) — stronger than 70% of steel grades. Elongation at break is 18% and the elastic modulus is 220 GPa (31.9 Msi).
Thermal6
SKH2 QT64-66HRC is rated for continuous service to 600°C (1,112 °F). It conducts heat at 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades. Thermal expansion is 10.6 µm/m·K (5.89 µin/in·°F).
Electrical3
SKH2 QT64-66HRC conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of SKH2 QT64-66HRC takes about 48 MJ of energy and emits 3.4 kg of CO₂ — more than 93% of steel grades. Typical recycled content is 35%.
Manufacturability7
SKH2 QT64-66HRC's machinability is not recommended (5/100, worse than 100% of steel grades); weldability poor (18/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SKH2 QT64-66HRC
Is SKH2 easy to machine?
Machine only in the annealed condition (≤255 HB) with sharp cobalt-HSS or coated carbide, rigid setups and flood coolant; hardened tools require grinding (Al₂O₃/CBN) or EDM.
Can SKH2 be welded?
Poor weldability — repair welding only with matching HSS filler, 500–550 °C preheat/interpass and immediate re-temper at 550–560 °C to avoid quench cracks.
Can SKH2 be formed, bent or molded?
Hot forge 1100–1150 °C, finish above 950 °C and cool slowly in furnace/vermiculite followed by 850–870 °C anneal; no meaningful cold forming.
What surface finishes work on SKH2?
Hardened surfaces take a mirror polish; protect with black oxide, steam blue, phosphate or PVD TiN/TiAlN — not anodizable and not corrosion-resistant bare.
SKH2 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 | 0.73 – 0.83 | 0.78 |
| Si | ≤ 0.45 | 0.25 |
| Mn | ≤ 0.4 | 0.25 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 3.8 – 4.5 | 4.15 |
| Wprincipal red-hardness element | 17 – 19 | 18 |
| V | 0.8 – 1.2 | 1.1 |
| Moresidual; not a specified alloying addition in SKH2 | ≤ 0.3 | — |
| Fe | balance | — |
SKH2 QT64-66HRC — frequently asked
What is SKH2 QT64-66HRC used for?
SKH2 QT64-66HRC is typically used for drills, reamers and lathe tools. In short: classic tungsten HSS; well-known T1 equivalent; lower cost than cobalt HSS.
What is the yield strength of SKH2 QT64-66HRC?
SKH2 QT64-66HRC has a typical yield strength of 540 MPa (78.3 ksi) and a tensile strength of 2,300 MPa (334 ksi) — stronger than 70% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is SKH2 QT64-66HRC easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 100% of steel grades). Machine only in the annealed condition (≤255 HB) with sharp cobalt-HSS or coated carbide, rigid setups and flood coolant; hardened tools require grinding (Al₂O₃/CBN) or EDM.
Can SKH2 QT64-66HRC be welded?
Not readily — weldability is rated poor (18/100). Poor weldability — repair welding only with matching HSS filler, 500–550 °C preheat/interpass and immediate re-temper at 550–560 °C to avoid quench cracks.
What surface finishes work on SKH2 QT64-66HRC?
Hardened surfaces take a mirror polish; protect with black oxide, steam blue, phosphate or PVD TiN/TiAlN — not anodizable and not corrosion-resistant bare.
Can SKH2 QT64-66HRC be formed, bent or molded?
Hot forge 1100–1150 °C, finish above 950 °C and cool slowly in furnace/vermiculite followed by 850–870 °C anneal; no meaningful cold forming.
What is the maximum service temperature of SKH2 QT64-66HRC?
SKH2 QT64-66HRC 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 SKH2-A and SKH2 QT-NIT?
A is the default condition — standard mill condition for machining tool blanks before hardening. QT-NIT: surface-engineered condition for higher cutting speeds and abrasive workpieces; core properties unchanged. Yield strength is 540 MPa in A versus 2,150 MPa in QT-NIT.
Sources
- JIS G4403 High Speed Tool Steel Materials — JSA (2015)
- GB/T 9943 (W18Cr4V) — SAC (2008)
- ASTM A600 Standard Specification for Tool Steel High Speed (T1) — ASTM (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16: Machining — ASM International (1989)
- High speed steel T1/W18Cr4V technical data — Böhler / Hitachi Metals (typical) (2020)
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.