Steel FDSiCrV OT-SP
Finish state
OT-SP = oT + SR + shot peened spring
Choose when the static-grade wire must still see load cycling: peening compressive layer lifts endurance markedly.
Values for the OT-SP condition
Other FDSiCrV tempers and conditions
FDSiCrV is listed in 8 conditions; see the grade overview at FDSiCrV.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OT | Largest supplied sizes for very heavy static springs; hardenability limits the achievable strength. | 1,440 | 1,620 | 8 | 47 HRC | 6.9 % IACS |
OT | Heavy springs (clutch, suspension aids) where load capacity matters more than peak tensile. | 1,530 | 1,720 | 8 | 49 HRC | 6.9 % IACS |
OT | Mid-heavy spring sizes; tensile level drops slightly with section. | 1,630 | 1,830 | 7 | 51 HRC | 6.9 % IACS |
OTDefault Oil hardened and tempered, d 2.0–4.0 mm | Standard stocked condition: quenched-and-tempered wire in the most common spring diameters, coiled cold by the spring maker. | 1,720 | 1,930 | 6 | 53 HRC | 6.9 % IACS |
coiled then stress-relieved 380–420 °C | Condition of the finished spring: stress relief after coiling restores elastic limit, sets free length and lowers relaxation. | 1,780 | 1,900 | 6 | 52 HRC | 6.9 % IACS |
OT-SPThis page OT + SR + shot peened spring | Choose when the static-grade wire must still see load cycling: peening compressive layer lifts endurance markedly. | 1,780 | 1,900 | 6 | 53 HRC | 6.9 % IACS |
OT | Common size band for small compression and torsion springs. | 1,790 | 2,010 | 5.5 | 54 HRC | 6.9 % IACS |
OT fine wire | Pick for small high-stress springs; the finest sizes carry the highest tensile level of the grade. | 1,900 | 2,120 | 5 | 56 HRC | 6.9 % IACS |
What is FDSiCrV OT-SP?
FDSiCrV OT-SP is FDSiCrV supplied in the OT-SP condition — choose when the static-grade wire must still see load cycling: peening compressive layer lifts endurance markedly. FDSiCrV OT-SP has a yield strength of 1,780 MPa (258 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 99% of steel grades. Elongation at break is 6% and the elastic modulus is 200 GPa (29 Msi). FDSiCrV OT-SP 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). OT is the default condition FabDigit quotes; OT-SP 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 weld — 8/100, worse than 99% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Difficult to machine — 18/100, worse than 97% of steel grades
- Low fracture toughness — 36 MPa·√m (32.8 ksi·√in), worse than 93% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
FDSiCrV OT-SP properties
Typical room-temperature values for FDSiCrV OT-SP; 22 are specific to this condition. Other listed values are FDSiCrV reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
FDSiCrV OT-SP 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
FDSiCrV OT-SP has a yield strength of 1,780 MPa (258 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 99% of steel grades. Elongation at break is 6% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
FDSiCrV OT-SP is rated for continuous service to 250°C (482 °F). It conducts heat at 30 W/m·K (17.3 BTU/hr·ft·°F), worse than 83% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
FDSiCrV OT-SP conducts electricity at 6.9 % IACS, worse than 76% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of FDSiCrV OT-SP takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability6
FDSiCrV OT-SP's machinability is poor (18/100, worse than 97% of steel grades); weldability not recommended (8/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FDSiCrV OT-SP
Is FDSiCrV easy to machine?
Delivered at ~50-55 HRC — do not turn or drill; finish springs by grinding ends and tumbling, or machine features before any thermal work.
Can FDSiCrV be welded?
Effectively unweldable for load-carrying joints: high carbon plus Si-Cr-V gives hard, crack-prone HAZ and destroys the tempered structure; use mechanical hooks or captive ends instead.
Can FDSiCrV be formed, bent or molded?
Cold-coil on CNC formers with generous mandrel ratio (D/d ≥ 4) and good lubricity (phosphated wire); always stress relieve 380–420 °C for 20–30 min after coiling, then optionally hot-set and shot peen.
What surface finishes work on FDSiCrV?
Phosphate+oil for storage; for service use zinc, Zn-Ni or Zn-flake/epoxy coating — after acid pickling or electroplating bake 190–220 °C to relieve hydrogen and avoid delayed fracture.
FDSiCrV 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 | 0.51 – 0.59 | 0.55 |
| Siraises elastic limit and relaxation resistance | 1.2 – 1.6 | 1.4 |
| Mn | 0.5 – 0.8 | 0.65 |
| Crhardenability | 0.5 – 0.8 | 0.65 |
| Vgrain refinement, temper resistance | 0.1 – 0.2 | 0.15 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cumax, residual | ≤ 0.12 | — |
| Fe | balance | — |
FDSiCrV OT-SP — frequently asked
What is FDSiCrV OT-SP used for?
FDSiCrV OT-SP is typically used for high-performance valve springs, critical fatigue-loaded springs and high-temperature service springs. In short: highest-strength FD spring wire; maximum design-stress springs; si-Cr-V alloyed, oil-tempered.
What is the yield strength of FDSiCrV OT-SP?
FDSiCrV OT-SP has a typical yield strength of 1,780 MPa (258 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is FDSiCrV OT-SP easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Delivered at ~50-55 HRC — do not turn or drill; finish springs by grinding ends and tumbling, or machine features before any thermal work.
Can FDSiCrV OT-SP be welded?
Not readily — weldability is rated not recommended (8/100). Effectively unweldable for load-carrying joints: high carbon plus Si-Cr-V gives hard, crack-prone HAZ and destroys the tempered structure; use mechanical hooks or captive ends instead.
What surface finishes work on FDSiCrV OT-SP?
Phosphate+oil for storage; for service use zinc, Zn-Ni or Zn-flake/epoxy coating — after acid pickling or electroplating bake 190–220 °C to relieve hydrogen and avoid delayed fracture.
Can FDSiCrV OT-SP be formed, bent or molded?
Cold-coil on CNC formers with generous mandrel ratio (D/d ≥ 4) and good lubricity (phosphated wire); always stress relieve 380–420 °C for 20–30 min after coiling, then optionally hot-set and shot peen.
What is the maximum service temperature of FDSiCrV OT-SP?
FDSiCrV OT-SP 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 FDSiCrV-OT and FDSiCrV OT-SR?
OT is the default condition — standard stocked condition: quenched-and-tempered wire in the most common spring diameters, coiled cold by the spring maker. OT-SR: condition of the finished spring: stress relief after coiling restores elastic limit, sets free length and lowers relaxation. Yield strength is 1,720 MPa in OT versus 1,780 MPa in OT-SR.
Sources
- EN 10270-2 Steel wire for mechanical springs — Part 2: Oil hardened and tempered spring steel wire — CEN (2012)
- EN 13906-1 Cylindrical helical springs — compression springs design — CEN (2013)
- EN ISO 683-14 / 54SiCrV6 spring steel chemistry — ISO (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels (spring steels) — ASM International (1990)
- Oil tempered Si-Cr and Si-Cr-V spring wire datasheets — Kanthal Garphyttan / Suzuki Garphyttan (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.