A chromium-vanadium alloy spring steel used wherever fatigue life and temper resistance matter. With roughly 0.50% carbon plus chromium and vanadium, 50CrV4 / 51CrV4 carries high-cycle valve and suspension springs at temperatures plain carbon grades cannot.
What Is 50CrV4 / 51CrV4 Spring Steel?
50CrV4 (DIN) and 51CrV4 (EN 10089, material 1.8159) are the same chromium-vanadium spring steel under different naming systems. The chromium raises hardenability so thick sections oil-harden through; the vanadium refines the grain and lifts fatigue strength.
It is the standard valve-spring and heavy-suspension grade. Compared with plain 65Mn, 50CrV4 keeps its temper at higher temperature and resists relaxation far better, which is why it is specified for engine and high-cycle springs.
Supply Forms and Sizes
Every form is available soft-annealed (for further forming and machining) or heat-treated to your hardness window.
| Form | Condition | Size Range | Typical Use |
|---|---|---|---|
| Cold-drawn wire | Annealed / oil-tempered | 0.2 – 12 mm | Valve springs, coil springs |
| Hardened & tempered strip | Q&T, edge dressed | 0.2 – 6 mm | Clutch springs, washers |
| Hot-rolled bar | Hot rolled / normalized | 8 – 100 mm | Torsion bars, forgings |
| Flat spring steel | Q&T | 3 – 40 mm | Suspension leaves, brackets |
Chemical Composition (EN 10089 (51CrV4 / 1.8159))
| C | Si | Mn | Cr | V | P max | S max |
|---|---|---|---|---|---|---|
| 0.46 – 0.54 | 0.15 – 0.40 | 0.70 – 1.10 | 0.90 – 1.20 | 0.10 – 0.25 | 0.025 | 0.025 |
Heat analysis is reported on the mill certificate for every lot. If your drawing calls for tighter limits than the standard, flag it at enquiry — ladle-refined heats usually meet it without a surcharge.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Elastic modulus (E) | ~200 GPa |
| Shear modulus (G) | ~79 GPa |
| Thermal conductivity | ~40 W/m·K at room temperature |
| Coefficient of thermal expansion | ~12 ×10⁻₆ /K (20 – 200 °C) |
Mechanical Properties
Typical values for 50CrV4 / 51CrV4 after oil quenching and tempering near 440 °C. The mill certificate is the binding document.
| Condition | Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|---|
| Annealed | ≥ 880 MPa | ≥ 700 MPa | ≥ 12 % | ≤ 269 HB |
| Q&T | 1280 – 1520 MPa | ≥ 1080 MPa | ≥ 9 % | 40 – 48 HRC |
| Oil-tempered wire | 1600 – 2000 MPa | — | — | per size class |
Equivalent Grades
| Standard | Designation |
|---|---|
| Europe EN 10089 | 51CrV4 (1.8159) |
| Germany DIN | 50CrV4 |
| USA AISI / SAE | 6150 (similar) |
| Japan JIS G4801 | SUP10 (similar) |
| China GB/T 1222 | 50CrVA (similar) |
Heat Treatment and Processing
Preheat slowly, then raise to the grade forging range. Work above the lower limit and cool slowly after forging to avoid cracks.
680 – 720 °C, soak, furnace cool. Soft condition for forming and coiling.
840 – 880 °C, oil. Full through-harden even in thicker bar.
400 – 550 °C by required hardness; ~440 °C gives the usual 44 – 48 HRC spring window.
After machining or forming, 200 – 350 °C for 1 – 2 hours, air cool, to stabilise dimensions and relieve residual stress.
Heat-treated bars and plates are supplied with the hardness and test certificate you specify. For critical parts we can control decarburisation depth and supply a spheroidized or soft-annealed structure on request.
Applications of 50CrV4 / 51CrV4 Spring Steel
The classic use — high-cycle life at elevated temperature.
Fatigue resistance keeps the set under continuous load.
Heavy-vehicle springs where plain carbon grades relax.
Compressors, hydraulic and railway springs.
Hardened-and-tempered strip keeps a reliable set.
Where relaxation could fail the assembly.
50CrV4 / 51CrV4 Spring Steel vs Alternative Grades
| Grade | vs 50CrV4 / 51CrV4 Spring Steel | Choose It When |
|---|---|---|
| 50CrV4 | — | High-cycle or warm springs where 65Mn would relax. |
| 65Mn | Cheaper, lower alloy | Light, low-cost strip and wire springs |
| SUP9 / 55Cr3 | Higher hardenability for very thick leaves | Heavy-vehicle leaf springs |
| 9260 (Si-Mn) | Higher Si, cheaper | Large leaf and coil springs, less fatigue critical |
Quality Control and Mill Certificates
Every shipment ships with an EN 10204 3.1 mill certificate covering heat chemical analysis, hardness and the mechanical test on record. On request we add: ultrasonic test on heavy bar and plate, magnetic particle inspection on machined surfaces, and third-party inspection (SGS / BV) before loading. Dimensional tolerances follow the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
What is 50CrV4 equivalent to?
EN 51CrV4 (1.8159) is the same steel; close to AISI 6150, JIS SUP10 and China 50CrVA. Confirm against the certificate for critical parts.
Is 50CrV4 better than 65Mn for springs?
For high-cycle or warm springs, yes — the Cr+V additions lift fatigue strength and temper resistance well above plain 65Mn.
What hardness does 50CrV4 reach?
Typically 40 – 48 HRC in the quenched-and-tempered spring condition.
Can 50CrV4 be welded?
It is hardenable and tends to crack; welding is avoided or done with full pre/post-heat by a qualified procedure.
What is the minimum order quantity?
Mill lots typically start at 500 kg per item; trial wire and strip are often from stock.
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