Steel 51CrV4 · heat-treated state
Steel 51CrV4 +S
Properties of the +S condition, compared with the other 51CrV4 tempers.
Softened delivery condition with hardness held below a set ceiling so bar and wire can be cold-sheared or cropped cleanly without cracking.
What is 51CrV4 +S?
51CrV4 +S is 51CrV4 heat treated to +S — softened delivery condition with hardness held below a set ceiling so bar and wire can be cold-sheared or cropped cleanly without cracking. 51CrV4 +S has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 51% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi). 51CrV4 +S 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). Annealed is the default condition FabDigit quotes; +S is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 77% of steel grades
- Low electrical conductivity — 6.9 % IACS, worse than 76% of steel grades
51CrV4 +S properties
Typical room-temperature values for 51CrV4 +S — 32 properties are specific to this condition; the rest are grade-level values shared by every 51CrV4 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
51CrV4 +S 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).
Mechanical13
51CrV4 +S has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 51% of steel grades. Elongation at break is 18% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
51CrV4 +S is rated for continuous service to 300°C (572 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
51CrV4 +S conducts electricity at 6.9 % IACS, worse than 76% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 51CrV4 +S takes about 24 MJ of energy and emits 1.9 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 40%.
Manufacturability7
51CrV4 +S's machinability is fair (52/100, better than 52% of steel grades); weldability poor (28/100); formability fair (48/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 51CrV4 tempers and conditions
51CrV4 is also supplied in 9 other conditions. The full side-by-side table is on the 51CrV4 overview.
- AnnealedDefaultStandard stock condition for bar and strip that will be machined or formed and then hardened by the customer.520 MPa yield · 230 HB
- Hardened & TemperedFull spring hardness for leaf springs, saw/knife blades and hand tools where maximum elastic limit is needed and ductility can be sacrificed.1,500 MPa yield · 50 HRC
- Q&TBest strength/toughness compromise for torsion bars, coil springs and highly loaded machine parts.1,150 MPa yield · 42 HRC
- +CHBar/rod delivered heat-treated to a specified core-strength (core hardness) band, giving uniform mid-range strength and good machinability before final hardening.460 MPa yield · 210 HB
- +SSoftened delivery condition with hardness held below a set ceiling so bar and wire can be cold-sheared or cropped cleanly without cracking.430 MPa yield · 215 HB
- +ACLong sub-critical anneal that rounds the carbides into globular form, giving the lowest hardness and best cold-forming/machining behaviour of this grade.380 MPa yield · 190 HB
Working with 51CrV4 +S
Is 51CrV4 easy to machine?
Machine in the annealed condition (≈55 % of 1212) with rigid setups and carbide tooling; above 40 HRC switch to CBN/ceramic or grinding.
Can 51CrV4 be welded?
Poor weldability at 0.5 % C — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper; avoid welding on finished springs.
Can 51CrV4 be formed, bent or molded?
Cold form or coil only in the annealed/soft state (bend radii ≥3 t), then austenitise 840–870 °C, oil quench and temper 400–520 °C; hot form 850–1050 °C.
What surface finishes work on 51CrV4?
Not anodisable; shot-peen springs for fatigue life, then phosphate + epoxy, zinc or Zn-Ni plating with bake-out at 200 °C to avoid hydrogen embrittlement.
51CrV4 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 | 0.47 – 0.55 | 0.51 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.7 – 1.1 | 0.9 |
| Cr | 0.9 – 1.2 | 1.05 |
| Vgrain refinement, secondary carbides | 0.1 – 0.25 | 0.15 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
51CrV4 +S — frequently asked
What is 51CrV4 +S used for?
51CrV4 +S is typically used for leaf springs, coil springs and springs. In short: vanadium chromium spring bar.
What is the yield strength of 51CrV4 +S?
51CrV4 +S has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 51CrV4 +S easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machine in the annealed condition (≈55 % of 1212) with rigid setups and carbide tooling; above 40 HRC switch to CBN/ceramic or grinding.
Can 51CrV4 +S be welded?
Not readily — weldability is rated poor (28/100). Poor weldability at 0.5 % C — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper; avoid welding on finished springs.
What surface finishes work on 51CrV4 +S?
Not anodisable; shot-peen springs for fatigue life, then phosphate + epoxy, zinc or Zn-Ni plating with bake-out at 200 °C to avoid hydrogen embrittlement.
Can 51CrV4 +S be formed, bent or molded?
Cold form or coil only in the annealed/soft state (bend radii ≥3 t), then austenitise 840–870 °C, oil quench and temper 400–520 °C; hot form 850–1050 °C.
What is the maximum service temperature of 51CrV4 +S?
51CrV4 +S is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 51CrV4 +S?
Yes — 51CrV4 +S is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- EN 10089 — Hot rolled steels for quenched and tempered springs — CEN (2002)
- EN 10270-2 — Steel wire for mechanical springs: oil hardened and tempered — CEN (2011)
- GB/T 1222 — (50CrVA) — SAC (2016)
- SAE J404 / ASTM A231 (AISI 6150 Cr-V spring steel) — SAE / ASTM (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Cr-V spring steel 1.8159 datasheet — Böhler / Ovako / Saarstahl (2022)
- EN 13906-1 — Cylindrical helical springs, design — CEN (2013)
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.