Steel M47 HT-68
Hardness band
AISI/SAE M47 · UNS T11347
HT-68 = hardened & tempered to maximum hardness
Top-hardness setting (higher austenitizing temperature) for finishing cutters on abrasive materials where toughness can be sacrificed.
Values for the HT-68 condition
Other M47 tempers and conditions
M47 is listed in 5 conditions; see the grade overview at M47.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Electrical sheet after quality-development anneal (customer full anneal) | Condition in which magnetic properties are actually realised — soft, grain-grown laminations after the ~790 °C decarburising/annealing cycle. | 210 | 340 | 33 | 100 HB | — |
Semi-processed non-oriented electrical sheet | Lowest-cost lamination sheet for small motors and ballasts, supplied hard-rolled for punching and annealed by the laminator afterwards. | 320 | 430 | 22 | 125 HB | 7.8 % IACS |
ANNDefault Annealed | Standard mill-supplied condition for machining or grinding tool blanks before hardening. | 570 | 890 | 18 | 25 HRC | 24 W/m·K |
HT-68This page Hardened & tempered to maximum hardness | Top-hardness setting (higher austenitizing temperature) for finishing cutters on abrasive materials where toughness can be sacrificed. | 2,000 | 2,100 | 0.5 | 68 HRC | 2.8 % IACS |
Hardened & triple tempered | Normal service condition: austenitize ~1190–1210 °C, quench, temper 3 × 1 h at ~540–550 °C for high red hardness. | — | 2,300 | 1 | 66 HRC | 21 W/m·K |
What is M47 HT-68?
M47 HT-68 is M47 heat treated to HT-68 — top-hardness setting (higher austenitizing temperature) for finishing cutters on abrasive materials where toughness can be sacrificed. M47 HT-68 has a yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 100% of steel grades. Elongation at break is 0.5% and the elastic modulus is 217 GPa (31.5 Msi). M47 HT-68 has a density of 8.03 g/cm³ (0.29 lb/in³), heavier than 96% of steel grades. It melts at 1,250°C (2,282 °F). ANN is the default condition FabDigit quotes; HT-68 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 — 600°C (1,112 °F), better than 98% 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
- Low fracture toughness — 13 MPa·√m (11.8 ksi·√in), worse than 100% of steel grades
- Difficult to machine — 6/100, worse than 100% of steel grades
- Difficult to weld — 3/100, worse than 100% of steel grades
- Limited formability — 1/100, worse than 100% of steel grades
M47 HT-68 properties
Typical room-temperature values for M47 HT-68; 23 are specific to this condition. Other listed values are M47 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M47 HT-68 has a density of 8.03 g/cm³ (0.29 lb/in³), heavier than 96% of steel grades. It melts at 1,250°C (2,282 °F).
Mechanical15
M47 HT-68 has a yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 100% of steel grades. Elongation at break is 0.5% and the elastic modulus is 217 GPa (31.5 Msi).
Thermal6
M47 HT-68 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 11 µm/m·K (6.11 µin/in·°F).
Electrical3
M47 HT-68 conducts electricity at 2.8 % IACS, worse than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of M47 HT-68 takes about 58 MJ of energy and emits 3.6 kg of CO₂ — more than 95% of steel grades. Typical recycled content is 35%.
Manufacturability8
M47 HT-68's machinability is not recommended (6/100, worse than 100% of steel grades); weldability not recommended (3/100); formability not recommended (1/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M47 HT-68
Is M47 easy to machine?
Machine only in the annealed state (≈255 HB, ~30 % of AISI 1212) with rigid setups and cobalt/carbide tooling; after hardening it is a grind-only material — use soft-grade CBN or SG alumina wheels and copious coolant to avoid grinding burn.
Can M47 be welded?
Not a structural weld metal; repair welding of tool edges only, with 500–550 °C preheat, matching Co-HSS or Ni-based filler and an immediate re-temper.
Can M47 be formed, bent or molded?
Hot work between about 1100 and 900 °C with slow furnace cooling; no meaningful cold formability — the A683 electrical-sheet variant, by contrast, is punched cold and then annealed.
What surface finishes work on M47?
Cannot be anodized; standard finishes are steam/black oxide, nitriding (thin case, watch edge brittleness) or PVD TiN/TiAlN applied below the 540 °C temper, plus oil film for storage.
M47 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 |
|---|---|---|
| Chigh-speed tool steel M47, ASTM A600 / UNS T11347 | 1.05 – 1.15 | 1.1 |
| Mn | 0.15 – 0.4 | 0.3 |
| Si | 0.2 – 0.65 | 0.4 |
| Cr | 3.5 – 4.25 | 3.85 |
| Mo | 9.25 – 10 | 9.6 |
| W | 1.15 – 1.85 | 1.5 |
| V | 1.15 – 1.35 | 1.25 |
| Co | 4.75 – 5.25 | 5 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| FeBalance. NOTE: the ASTM A683 'M47' electrical sheet of the same name is an unrelated low-carbon Fe–Si sheet (C ≤ 0.03, Si+Al ≈ 0.5–1.5 %, Mn ≈ 0.3), specified by core loss rather than chemistry. | balance | — |
M47 HT-68 — frequently asked
What is M47 HT-68 used for?
M47 HT-68 is typically used for low-cost fractional-hp motors, toys and small solenoids. In short: cheapest M-series lamination grade; price over magnetic performance; grind-only when hardened.
What is the yield strength of M47 HT-68?
M47 HT-68 has a typical yield strength of 2,000 MPa (290 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is M47 HT-68 easy to machine?
Not especially — machinability is rated not recommended (6/100, worse than 100% of steel grades). Machine only in the annealed state (≈255 HB, ~30 % of AISI 1212) with rigid setups and cobalt/carbide tooling; after hardening it is a grind-only material — use soft-grade CBN or SG alumina wheels and copious coolant to avoid grinding burn.
Can M47 HT-68 be welded?
Not readily — weldability is rated not recommended (3/100). Not a structural weld metal; repair welding of tool edges only, with 500–550 °C preheat, matching Co-HSS or Ni-based filler and an immediate re-temper.
What surface finishes work on M47 HT-68?
Cannot be anodized; standard finishes are steam/black oxide, nitriding (thin case, watch edge brittleness) or PVD TiN/TiAlN applied below the 540 °C temper, plus oil film for storage.
Can M47 HT-68 be formed, bent or molded?
Hot work between about 1100 and 900 °C with slow furnace cooling; no meaningful cold formability — the A683 electrical-sheet variant, by contrast, is punched cold and then annealed.
What is the maximum service temperature of M47 HT-68?
M47 HT-68 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 M47-ANN and M47 HT-68?
ANN is the default condition — standard mill-supplied condition for machining or grinding tool blanks before hardening. HT-68: top-hardness setting (higher austenitizing temperature) for finishing cutters on abrasive materials where toughness can be sacrificed. Yield strength is 570 MPa in ANN versus 2,000 MPa in HT-68.
Sources
- ASTM A600 — Standard Specification for Tool Steel High Speed — ASTM International (2016)
- ASTM A683 — Standard Specification for Nonoriented Electrical Steel, Semiprocessed Types — ASTM International (2019)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 16: Machining — ASM International (1989)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- SAE J438 / UNS T11347 designation data — SAE International (2017)
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.