Steel M50 · temper · default condition
Steel M50 Annealed
Properties of the Annealed condition, compared with the other M50 tempers.
Standard supply condition for machining rings, gears and forging preforms before hardening.
What is M50 Annealed?
M50 Annealed is M50 in the Annealed temper — standard supply condition for machining rings, gears and forging preforms before hardening. M50 Annealed has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 74% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi). M50 Annealed 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).
Advantages
- Polishes to a fine finish — 85/100, better than 99% of steel grades
Limitations
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
- High embodied carbon — 3.6 kg CO₂/kg, worse than 93% of steel grades
- Limited formability — 12/100, worse than 91% of steel grades
M50 Annealed properties
Typical room-temperature values for M50 Annealed — 12 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 Annealed 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 Annealed has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 74% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
M50 Annealed is rated for continuous service to 200°C (392 °F). It conducts heat at 26 W/m·K (15 BTU/hr·ft·°F), worse than 86% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
M50 Annealed 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 Annealed 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 Annealed's machinability is fair (35/100, worse than 83% of steel grades); weldability not recommended (10/100); formability not recommended (12/100).
Common Calculations5
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 Annealed
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 Annealed — frequently asked
What is M50 Annealed used for?
M50 Annealed 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 Annealed?
M50 Annealed has a typical yield strength of 570 MPa (82.7 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 74% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is M50 Annealed easy to machine?
Not especially — machinability is rated fair (35/100, worse than 83% 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 Annealed 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 Annealed?
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 Annealed 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 Annealed?
M50 Annealed is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in M50 Annealed?
Yes — M50 Annealed 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.