Steel M50 · hardness band
Steel M50 HT 58-60 HRC
Properties of the HT 58-60 HRC condition, compared with the other M50 tempers.
Lower-hardness heat treat used where a little extra toughness is wanted in gears or lightly loaded races.
What is M50 HT 58-60 HRC?
M50 HT 58-60 HRC is M50 heat treated to HT 58-60 HRC — lower-hardness heat treat used where a little extra toughness is wanted in gears or lightly loaded races. M50 HT 58-60 HRC has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Elongation at break is 2% and the elastic modulus is 207 GPa (30 Msi). M50 HT 58-60 HRC has a density of 8 g/cm³ (0.289 lb/in³), heavier than 95% of steel grades. It melts at 1,400°C (2,552 °F). Annealed is the default condition FabDigit quotes; HT 58-60 HRC is available on request or by drawing note.
Advantages
- High strength — 1,950 MPa (283 ksi), better than 100% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Low fracture toughness — 24 MPa·√m (21.8 ksi·√in), worse than 98% of steel grades
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
M50 HT 58-60 HRC properties
Typical room-temperature values for M50 HT 58-60 HRC — 14 properties are specific to this condition; the rest are grade-level values shared by every M50 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
M50 HT 58-60 HRC has a density of 8 g/cm³ (0.289 lb/in³), heavier than 95% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical17
M50 HT 58-60 HRC has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Elongation at break is 2% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
M50 HT 58-60 HRC is rated for continuous service to 315°C (599 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 91% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
M50 HT 58-60 HRC conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of M50 HT 58-60 HRC takes about 50 MJ of energy and emits 3.6 kg of CO₂ — more than 93% of steel grades. Typical recycled content is 15%.
Manufacturability8
M50 HT 58-60 HRC's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (10/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other M50 tempers and conditions
M50 is also supplied in 6 other conditions. The full side-by-side table is on the M50 overview.
- AnnealedDefaultStandard supply condition for machining rings, gears and forging preforms before hardening.570 MPa yield · 22 HRC
- HT 62-65 HRCMaximum wear resistance for balls, rollers and cutting-type tooling; lowest toughness of the M50 conditions.2,300 MPa yield · 64 HRC
- HT 60-62 HRCStandard aero main-shaft bearing condition — best balance of rolling contact fatigue life and toughness.2,150 MPa yield · 61 HRC
- HT 58-60 HRCLower-hardness heat treat used where a little extra toughness is wanted in gears or lightly loaded races.1,950 MPa yield · 59 HRC
Working with M50 HT 58-60 HRC
Is M50 easy to machine?
Machine only in the annealed condition (~240 HB) with rigid setups and coated carbide; after hardening to 60+ HRC use CBN turning or vitrified/CBN grinding with generous coolant to avoid grinding burn.
Can M50 be welded?
Essentially not weldable for structural use — high carbon and strong air-hardening cause quench cracking; any repair needs 500–550 °C preheat, matching filler and immediate re-temper.
Can M50 be formed, bent or molded?
Hot forge 1050–1150 °C, finish above 950 °C and slow-cool to the anneal; no meaningful cold forming. Harden 1090–1120 °C (salt or vacuum), oil/gas quench, then triple temper at 540–565 °C with intermediate cooling to room temperature (deep-freeze optional).
What surface finishes work on M50?
Superfinish/lap raceways to Ra < 0.05 µm; protect with oil, black oxide, phosphate or thin dense chrome — the 4% Cr does not confer stainless behaviour, and low-temperature ion nitriding or DLC is used where extra scuffing resistance is needed.
M50 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 | 0.77 – 0.85 | 0.8 |
| Mn | 0.15 – 0.35 | 0.25 |
| Si | 0.1 – 0.25 | 0.2 |
| Cr | 3.75 – 4.25 | 4.1 |
| Mo | 4 – 4.5 | 4.25 |
| V | 0.9 – 1.1 | 1 |
| Wresidual | ≤ 0.25 | — |
| Niresidual | ≤ 0.15 | — |
| Coresidual | ≤ 0.25 | — |
| Curesidual | ≤ 0.1 | — |
| P | ≤ 0.02 | — |
| SAMS 6491 VIM-VAR limit | ≤ 0.01 | — |
| O10 ppm max typical for VIM-VAR | ≤ 0 | 6×10⁻⁴ |
| Fe | balance | — |
M50 HT 58-60 HRC — frequently asked
What is M50 HT 58-60 HRC used for?
M50 HT 58-60 HRC is typically used for aircraft engine mainshaft bearing rings, aerospace bearing balls and rollers, gas turbine accessory bearings, high-speed machine tool spindle bearings, rolling-contact test specimens and precision cam followers. In short: high-speed M50 tool.
What is the yield strength of M50 HT 58-60 HRC?
M50 HT 58-60 HRC has a typical yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is M50 HT 58-60 HRC easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine only in the annealed condition (~240 HB) with rigid setups and coated carbide; after hardening to 60+ HRC use CBN turning or vitrified/CBN grinding with generous coolant to avoid grinding burn.
Can M50 HT 58-60 HRC be welded?
Not readily — weldability is rated not recommended (10/100). Essentially not weldable for structural use — high carbon and strong air-hardening cause quench cracking; any repair needs 500–550 °C preheat, matching filler and immediate re-temper.
What surface finishes work on M50 HT 58-60 HRC?
Superfinish/lap raceways to Ra < 0.05 µm; protect with oil, black oxide, phosphate or thin dense chrome — the 4% Cr does not confer stainless behaviour, and low-temperature ion nitriding or DLC is used where extra scuffing resistance is needed.
Can M50 HT 58-60 HRC be formed, bent or molded?
Hot forge 1050–1150 °C, finish above 950 °C and slow-cool to the anneal; no meaningful cold forming. Harden 1090–1120 °C (salt or vacuum), oil/gas quench, then triple temper at 540–565 °C with intermediate cooling to room temperature (deep-freeze optional).
What is the maximum service temperature of M50 HT 58-60 HRC?
M50 HT 58-60 HRC is rated for continuous use to about 315°C (599 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in M50 HT 58-60 HRC?
Yes — M50 HT 58-60 HRC is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- AMS 6491 — Steel Bars, Forgings and Tubing, 4.1Cr-4.2Mo-1.0V, Premium Aircraft-Quality, Consumable Electrode Vacuum Melted — SAE International (2020)
- AMS 6490 — Steel Bars and Forgings, M50, Consumable Electrode Vacuum Melted — SAE International (2018)
- 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 Specialty Handbook: Tool Materials — ASM International (1995)
- Bearing-quality M50 VIM-VAR bar datasheets (Böhler, Latrobe/Carpenter, Aubert & Duval) — various producers (2023)
- GB/T 3077 / 8Cr4Mo4V (2015)
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.