Steel VDSiCr-NIT
Finish state
GB VDSiCr
NIT = oT + gas nitrided (+ peened) valve spring
Top-end high-rev valve springs: nitrided case ~700–900 HV gives maximum fatigue and sag resistance at elevated temperature.
Values for the NIT condition
Other VDSiCr tempers and conditions
VDSiCr is listed in 6 conditions; see the grade overview at VDSiCr.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
d 5.0–8.0 mm oil hardened and tempered | Larger diameters for suspension, clutch and heavy-duty valve springs; strength drops with section size. | 1,660 | 1,880 | 7 | 53 HRC | 6.6 % IACS |
NITThis page OT + gas nitrided (+ peened) valve spring | Top-end high-rev valve springs: nitrided case ~700–900 HV gives maximum fatigue and sag resistance at elevated temperature. | 1,780 | 2,000 | 4 | 62 HRC | 6.5 % IACS |
OTDefault Oil hardened and tempered wire, d 2.0–4.0 mm | Standard as-delivered valve-spring wire size range; pick for engine valve springs and high-stress small coil springs. | 1,800 | 2,030 | 6 | 55 HRC | 6.6 % IACS |
OT + stress relieved + shot peened | Choose when fatigue life at high shear stress governs — compressive surface stress raises endurance markedly. | 1,810 | 2,000 | 6 | 57 HRC | 6.6 % IACS |
Stress relieved | Standard post-coiling treatment: restores elastic limit and relaxation resistance after cold coiling. | 1,830 | 2,000 | 6.5 | 54 HRC | 6.6 % IACS |
OT fine wire | Highest strength size class; used for small valve springs, clutch damper and precision springs. | 1,900 | 2,150 | 5 | 57 HRC | 6.6 % IACS |
What is VDSiCr-NIT?
VDSiCr-NIT is VDSiCr supplied in the NIT condition — top-end high-rev valve springs: nitrided case ~700–900 HV gives maximum fatigue and sag resistance at elevated temperature. VDSiCr-NIT has a yield strength of 1,780 MPa (258 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Elongation at break is 4% and the elastic modulus is 206 GPa (29.9 Msi). VDSiCr-NIT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,420°C (2,588 °F). OT is the default condition FabDigit quotes; NIT is available on request or by drawing note.
Advantages
- High strength — 1,780 MPa (258 ksi), better than 99% of steel grades
Limitations
- Difficult to machine — 3/100, worse than 100% of steel grades
- Difficult to weld — 3/100, worse than 100% of steel grades
- Limited ductility — 4%, worse than 98% of steel grades
- Low fracture toughness — 25 MPa·√m (22.8 ksi·√in), worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
VDSiCr-NIT properties
Typical room-temperature values for VDSiCr-NIT; 22 are specific to this condition. Other listed values are VDSiCr reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
VDSiCr-NIT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
VDSiCr-NIT has a yield strength of 1,780 MPa (258 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Elongation at break is 4% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
VDSiCr-NIT is rated for continuous service to 220°C (428 °F). It conducts heat at 41 W/m·K (23.7 BTU/hr·ft·°F), worse than 62% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
VDSiCr-NIT conducts electricity at 6.5 % IACS, worse than 77% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of VDSiCr-NIT takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability5
VDSiCr-NIT's machinability is not recommended (3/100, worse than 100% of steel grades); weldability not recommended (3/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with VDSiCr-NIT
Is VDSiCr easy to machine?
Delivered at ~55 HRC — grind or EDM only; ends are ground, not turned, and any nick becomes a fatigue origin.
Can VDSiCr be welded?
Effectively unweldable in service condition; only resistance/friction butt joins with full re-quench-and-temper are acceptable.
Can VDSiCr be formed, bent or molded?
Cold coil on CNC spring machines with generous mandrel ratio (C ≥ 4), then stress relieve 400–430 °C; hot setting/presetting is standard before peening.
What surface finishes work on VDSiCr?
Shot peen (often dual/stress peen), optional gas nitriding, then phosphate + epoxy or zinc-flake coating; avoid acid pickling and electroplating without hydrogen bake-out.
VDSiCr 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 | 0.5 – 0.6 | 0.55 |
| Si | 1.2 – 1.6 | 1.4 |
| Mn | 0.5 – 0.9 | 0.7 |
| Cr | 0.5 – 0.8 | 0.65 |
| Pvalve spring quality, low residuals | ≤ 0.02 | 0.01 |
| S | ≤ 0.02 | 0.01 |
| Curesidual | ≤ 0.12 | 0.05 |
| Fe | balance | — |
VDSiCr-NIT — frequently asked
What is VDSiCr-NIT used for?
VDSiCr-NIT is typically used for engine valve springs, high-cycle fatigue springs and precision mechanical springs. In short: standard high-stress valve wire; strong relaxation resistance; nitridable spring grade.
What is the yield strength of VDSiCr-NIT?
VDSiCr-NIT has a typical yield strength of 1,780 MPa (258 ksi) and a tensile strength of 2,000 MPa (290 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is VDSiCr-NIT easy to machine?
Not especially — machinability is rated not recommended (3/100, worse than 100% of steel grades). Delivered at ~55 HRC — grind or EDM only; ends are ground, not turned, and any nick becomes a fatigue origin.
Can VDSiCr-NIT be welded?
Not readily — weldability is rated not recommended (3/100). Effectively unweldable in service condition; only resistance/friction butt joins with full re-quench-and-temper are acceptable.
What surface finishes work on VDSiCr-NIT?
Shot peen (often dual/stress peen), optional gas nitriding, then phosphate + epoxy or zinc-flake coating; avoid acid pickling and electroplating without hydrogen bake-out.
Can VDSiCr-NIT be formed, bent or molded?
Cold coil on CNC spring machines with generous mandrel ratio (C ≥ 4), then stress relieve 400–430 °C; hot setting/presetting is standard before peening.
What is the maximum service temperature of VDSiCr-NIT?
VDSiCr-NIT is rated for continuous use to about 220°C (428 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between VDSiCr-OT and VDSiCr OT-FINE?
OT is the default condition — standard as-delivered valve-spring wire size range; pick for engine valve springs and high-stress small coil springs. OT-FINE: highest strength size class; used for small valve springs, clutch damper and precision springs. Yield strength is 1,800 MPa in OT versus 1,900 MPa in OT-FINE.
Sources
- EN 10270-2 Steel wire for mechanical springs — Part 2: Oil hardened and tempered spring steel wire — CEN (2012)
- SAE J157 / SAE 9254 chrome-silicon oil tempered spring wire — SAE International (2018)
- JIS G 3561 SWOSC-V oil tempered Si-Cr valve spring wire — JSA (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (spring steels) — ASM International (1990)
- EN 13906-1 Cylindrical helical springs — design and calculation — CEN (2013)
- Oil tempered Si-Cr valve spring wire datasheets — Suzuki Garphyttan / Kobe Steel (2022)
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.