Steel M50 VIM-VAR
Grade
AISI/SAE M50 · UNS T11350 · EN 80MoCrV42-16
VIM-VAR = vacuum induction melted + vacuum arc remelted
Aerospace double-vacuum melt with very low oxygen and inclusion content — required for engine main-shaft bearings.
Values for the VIM-VAR condition
Other M50 tempers and conditions
M50 is listed in 7 conditions; see the grade overview at M50.
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 |
VIM-VARThis page 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 VIM-VAR?
M50 VIM-VAR is M50 in the VIM-VAR grade — aerospace double-vacuum melt with very low oxygen and inclusion content — required for engine main-shaft bearings. M50 VIM-VAR has a yield strength of 2,200 MPa (319 ksi) and a tensile strength of 2,500 MPa (363 ksi) — stronger than 100% of steel grades. Elongation at break is 2% and the elastic modulus is 208 GPa (30.2 Msi). M50 VIM-VAR 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; VIM-VAR is available on request or by drawing note.
Advantages
- High strength — 2,200 MPa (319 ksi), better than 100% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
Limitations
- Difficult to machine — 6/100, worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 2/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Low fracture toughness — 22 MPa·√m (20 ksi·√in), worse than 98% of steel grades
M50 VIM-VAR properties
Typical room-temperature values for M50 VIM-VAR; 22 are specific to this condition. Other listed values are M50 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M50 VIM-VAR 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 VIM-VAR has a yield strength of 2,200 MPa (319 ksi) and a tensile strength of 2,500 MPa (363 ksi) — stronger than 100% of steel grades. Elongation at break is 2% and the elastic modulus is 208 GPa (30.2 Msi).
Thermal6
M50 VIM-VAR is rated for continuous service to 315°C (599 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
M50 VIM-VAR conducts electricity at 2.7 % IACS, worse than 96% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of M50 VIM-VAR 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 VIM-VAR's machinability is not recommended (6/100, worse than 100% of steel grades); weldability not recommended (5/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M50 VIM-VAR
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 VIM-VAR — frequently asked
What is M50 VIM-VAR used for?
M50 VIM-VAR 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 VIM-VAR?
M50 VIM-VAR has a typical yield strength of 2,200 MPa (319 ksi) and a tensile strength of 2,500 MPa (363 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is M50 VIM-VAR easy to machine?
Not especially — machinability is rated not recommended (6/100, 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 VIM-VAR be welded?
Not readily — weldability is rated not recommended (5/100). 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 VIM-VAR?
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 VIM-VAR 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 VIM-VAR?
M50 VIM-VAR 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.
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.
Can FabDigit make parts in M50 VIM-VAR?
Yes — M50 VIM-VAR 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.