Steel M50
AISI/SAE M50 · UNS T11350 · EN 80MoCrV42-16
M50 (UNS T11350) is a molybdenum high-speed tool steel adapted for rolling-element bearings, normally supplied VAR or VIM-VAR so that cleanliness supports rolling-contact fatigue life.
Values for the Annealed condition
M50 tempers and conditions
M50 is supplied in 7 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault spheroidize annealed bar/forging stock | Standard supply condition for machining rings, gears and forging preforms before hardening. | 570 | 860 | 12 | 22 HRC | 26 W/m·K |
Hot rolled / forged, un-annealed bar | Mill-supplied hot worked bar before spheroidize annealing; must be annealed prior to machining. | 880 | 1,150 | 8 | 37 HRC | 2.9 % IACS |
Hardened & double/triple tempered to 58–60 HRC | Lower-hardness heat treat used where a little extra toughness is wanted in gears or lightly loaded races. | 1,950 | 2,250 | 2 | 59 HRC | 23 W/m·K |
Vacuum arc remelted stock | Single-remelt cleanliness grade for industrial bearings and tooling where full aerospace purity is not required. | 2,100 | 2,400 | 1.5 | 61 HRC | 2.7 % IACS |
Hardened & triple tempered to 60–62 HRC | Standard aero main-shaft bearing condition — best balance of rolling contact fatigue life and toughness. | 2,150 | 2,450 | 1.5 | 61 HRC | 23 W/m·K |
Vacuum induction melted + vacuum arc remelted | Aerospace double-vacuum melt with very low oxygen and inclusion content — required for engine main-shaft bearings. | 2,200 | 2,500 | 2 | 62 HRC | 2.7 % IACS |
Hardened & tempered to 62–65 HRC | Maximum wear resistance for balls, rollers and cutting-type tooling; lowest toughness of the M50 conditions. | 2,300 | 2,600 | 1 | 64 HRC | 23 W/m·K |
What is M50?
M50 (UNS T11350) is a molybdenum high-speed tool steel adapted for rolling-element bearings, normally supplied VAR or VIM-VAR so that cleanliness supports rolling-contact fatigue life. Annealed bar (570 MPa yield, 860 MPa tensile, 12 % elongation, 240 HB) is machined and then hardened to 58–65 HRC for jet engine and high-speed spindle bearings that must retain hot hardness at service temperatures to about 200 °C; thermal conductivity is 26 W/m·K. It is effectively non-weldable, slow to machine (machinability 35), and the 4 % Cr gives no stainless behaviour, so parts need oil, conversion coating or plating. 52100 is the usual alternative where operating temperatures are lower. M50 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). M50 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).
What is M50 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
- Precision cam followers
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
- High embodied carbon — 3.6 kg CO₂/kg, worse than 94% 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
- Limited formability — 12/100, worse than 92% of steel grades
M50 properties
Typical room-temperature values for M50-Annealed; bars are the position among steel grades.
Physical3
M50 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 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 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 87% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
M50 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 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's machinability is fair (35/100, worse than 84% 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.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. M50 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with M50
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).
Manufacturability
The process limits FabDigit applies to M50. Every M50 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Poor35 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel M50 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T11350
- EN / DIN / Werkstoff-Nr.
- 80MoCrV42-16
- Also called
- 6491
How much does M50 cost?
M50 is a premium-cost steel ($$$), pricier than about 57% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
M50 — frequently asked
What is M50 used for?
M50 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?
M50 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 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% 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 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?
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 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?
M50 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.
What is the difference between M50 Annealed and M50 VIM-VAR?
Annealed is the default condition — standard supply condition for machining rings, gears and forging preforms before hardening. VIM-VAR: aerospace double-vacuum melt with very low oxygen and inclusion content — required for engine main-shaft bearings. Yield strength is 570 MPa in Annealed versus 2,200 MPa in VIM-VAR.
How much does M50 cost?
M50 is a premium-cost steel ($$$), pricier than about 57% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in M50?
Yes — M50 is available for CNC machining; every part is priced by an engineer rather than instantly. 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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.