Steel 50CrVA-OT (Oil-Tempered spring wire)
Heat-treated state
GB 50CrVA · AISI/SAE 6150 · JIS SUP10
Continuously quenched-and-tempered round wire for cold-coiled valve, clutch and suspension springs; strength rises as diameter falls.
Values for the OT condition
Other 50CrVA tempers and conditions
50CrVA is listed in 9 conditions; see the grade overview at 50CrVA.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Cold-rolled annealed strip | Thin strip for stamped flat springs, clips and shims that are hardened and tempered after blanking. | 480 | 760 | 18 | 18 HRC | 8.5 % IACS |
Solution annealed | Pick for machining, cold coiling of heavy bar and stock that will be hardened after forming. | 500 | 780 | 20 | 225 HB | — |
Normalized | Grain-refining condition used to homogenize forgings before hardening; rarely a service condition. | 620 | 950 | 14 | 30 HRC | — |
Hot rolled | Cheapest mill condition for spring makers who hot-form then quench and temper in-house. | 650 | 1,000 | 12 | 30 HRC | 7.8 % IACS |
Cold drawn | Use for precise-diameter bar and cold-coiling wire that will be stress-relieved or hardened afterwards. | 720 | 900 | 9 | 27 HRC | 7.8 % IACS |
QTDefault Quenched and tempered | Standard spring/torsion-bar condition: best balance of ~1300–1400 MPa strength, ductility and fatigue life. | 1,200 | 1,350 | 12 | 43 HRC | — |
Q&T 45–48 HRC | Higher-stress leaf and coil springs, torsion bars and clamps where set resistance beats toughness. | 1,420 | 1,570 | 9 | 46 HRC | — |
OTThis page Oil-Tempered spring wire | Continuously quenched-and-tempered round wire for cold-coiled valve, clutch and suspension springs; strength rises as diameter falls. | 1,550 | 1,750 | 8 | 50 HRC | 7.5 % IACS |
Q&T 50–53 HRC | Maximum-strength condition for punches, chisels, blades, disc springs and shear knives; low toughness. | 1,620 | 1,800 | 7 | 51 HRC | — |
What is 50CrVA-OT?
50CrVA-OT is 50CrVA heat treated to OT — continuously quenched-and-tempered round wire for cold-coiled valve, clutch and suspension springs; strength rises as diameter falls. 50CrVA-OT has a yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,750 MPa (254 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi). 50CrVA-OT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). QT is the default condition FabDigit quotes; OT is available on request or by drawing note.
Advantages
- High strength — 1,550 MPa (225 ksi), better than 97% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 10/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
50CrVA-OT properties
Typical room-temperature values for 50CrVA-OT; 22 are specific to this condition. Other listed values are 50CrVA reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
50CrVA-OT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
50CrVA-OT has a yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,750 MPa (254 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
50CrVA-OT is rated for continuous service to 250°C (482 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
50CrVA-OT conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 50CrVA-OT takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
50CrVA-OT's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (10/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 50CrVA-OT
Is 50CrVA easy to machine?
Machine in the annealed condition (≈60 % of 1212) with carbide tooling; above ~45 HRC switch to grinding, CBN turning or EDM.
Can 50CrVA be welded?
Poor weldability — CE ≈ 0.85: preheat 300–400 °C, low-hydrogen consumables and immediate temper, or avoid welding on sprung parts entirely.
Can 50CrVA be formed, bent or molded?
Hot form at 900–1100 °C or cold-coil in annealed/oil-tempered condition; harden from 850–870 °C in oil, temper 400–500 °C, then shot peen for fatigue life.
What surface finishes work on 50CrVA?
No corrosion resistance: use phosphate + oil, black oxide, painted/powder-coated leaf springs, or Zn/Zn-Ni plating with bake-out at 190–210 °C to avoid hydrogen embrittlement.
50CrVA 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 |
|---|---|---|
| CGB/T 1222-2016 | 0.46 – 0.54 | 0.5 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.8 – 1.1 | 0.95 |
| Vgrain refiner, carbide former | 0.1 – 0.2 | 0.15 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Niresidual | ≤ 0.35 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
50CrVA-OT — frequently asked
What is 50CrVA-OT used for?
50CrVA-OT is typically used for coil springs, leaf springs, torsion bars and valve springs. In short: high-fatigue spring steel; tougher than 60Si2Mn; poor weldability, high strength.
What is the yield strength of 50CrVA-OT?
50CrVA-OT has a typical yield strength of 1,550 MPa (225 ksi) and a tensile strength of 1,750 MPa (254 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 50CrVA-OT easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Machine in the annealed condition (≈60 % of 1212) with carbide tooling; above ~45 HRC switch to grinding, CBN turning or EDM.
Can 50CrVA-OT be welded?
Not readily — weldability is rated not recommended (10/100). Poor weldability — CE ≈ 0.85: preheat 300–400 °C, low-hydrogen consumables and immediate temper, or avoid welding on sprung parts entirely.
What surface finishes work on 50CrVA-OT?
No corrosion resistance: use phosphate + oil, black oxide, painted/powder-coated leaf springs, or Zn/Zn-Ni plating with bake-out at 190–210 °C to avoid hydrogen embrittlement.
Can 50CrVA-OT be formed, bent or molded?
Hot form at 900–1100 °C or cold-coil in annealed/oil-tempered condition; harden from 850–870 °C in oil, temper 400–500 °C, then shot peen for fatigue life.
What is the maximum service temperature of 50CrVA-OT?
50CrVA-OT is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50CrVA-QT and 50CrVA CR-ANN?
QT is the default condition — standard spring/torsion-bar condition: best balance of ~1300–1400 MPa strength, ductility and fatigue life. CR-ANN: thin strip for stamped flat springs, clips and shims that are hardened and tempered after blanking. Yield strength is 1,200 MPa in QT versus 480 MPa in CR-ANN.
Sources
- GB/T 1222 (2016)
- EN 10089 Hot-rolled steels for quenched and tempered springs (50CrV4, 1.8159) — CEN (2002)
- SAE J404 / ASTM A231 Chromium-vanadium alloy steel spring wire (6150) — SAE / ASTM (2019)
- JIS G 4801 Spring steels (SUP10) — JISC (2011)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook (machinability and heat-treatment data) — Industrial Press (2020)
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.