Steel FDSiCr
FDSiCr is a silicon-chromium alloyed spring steel wire of the ASTM A401 class, drawn and oil-tempered for high strength and good relaxation resistance.
Reference datasheet — FDSiCr is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the OT condition
FDSiCr tempers and conditions
FDSiCr is supplied in 6 conditions, soft to hard. OT is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Intermediate supply condition for cold heading, machining or hot coiling followed by full quench and temper. | 500 | 780 | 16 | 20 HRC | 8 % IACS |
oil hardened and tempered, d 5.0–10.0 mm | Large suspension/clutch springs; strength drops with section but relaxation resistance is retained. | 1,520 | 1,720 | 8 | 50 HRC | 7 % IACS |
OTDefault Oil hardened and tempered, d 2.0–5.0 mm | Standard stocked condition: coil the spring directly from the wire, then low-temperature stress relieve. | 1,680 | 1,900 | 6 | 54 HRC | — |
Stress relieved | Mandatory post-coiling treatment: restores elastic limit, stabilises free length and improves set/relaxation resistance. | 1,750 | 1,880 | 6 | 53 HRC | 7 % IACS |
Stress relieved and shot peened spring | Pick when cyclic life governs: compressive surface stress from peening markedly raises the fatigue limit. | 1,750 | 1,880 | 6 | 54 HRC | 7 % IACS |
OT fine wire | Choose for small compression/torsion springs where the highest tensile level of the FDSiCr class is available. | 1,820 | 2,050 | 5 | 56 HRC | 7 % IACS |
What is FDSiCr?
FDSiCr is a silicon-chromium alloyed spring steel wire of the ASTM A401 class, drawn and oil-tempered for high strength and good relaxation resistance. It is the standard wire for valve springs and other high-cycle fatigue springs and is stocked in standard, fine and heavy OT diameters plus stress-relieved and stress-relieved/shot-peened conditions. Default values are 1680 MPa yield, 1900 MPa tensile, 6 % elongation, about 54 HRC and service to 250 °C. Formability is limited and the wire is essentially unweldable at working hardness with no corrosion resistance, so coating with hydrogen bake-out is required; FDSiCrV adds vanadium for still higher design stress. FDSiCr 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). FDSiCr has a yield strength of 1,680 MPa (244 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 206 GPa (29.9 Msi).
What is FDSiCr used for?
- valve springs
- high-fatigue mechanical springs
- suspension-related small springs
Advantages
- High strength — 1,680 MPa (244 ksi), better than 99% of steel grades
Limitations
- Difficult to machine — 15/100, worse than 98% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
FDSiCr properties
Typical room-temperature values for FDSiCr-OT; bars are the position among steel grades.
Physical3
FDSiCr 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).
Mechanical12
FDSiCr has a yield strength of 1,680 MPa (244 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 206 GPa (29.9 Msi).
Thermal6
FDSiCr is rated for continuous service to 250°C (482 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
FDSiCr conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of FDSiCr takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability6
FDSiCr's machinability is poor (15/100, worse than 98% of steel grades); weldability poor (15/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. FDSiCr is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FDSiCr
Is FDSiCr easy to machine?
Not a machining grade in the OT condition (~54 HRC) — grind or use in the annealed rod condition, then quench and temper.
Can FDSiCr be welded?
Essentially unweldable in service condition; only resistance/laser tack joints with immediate local re-temper, otherwise cracking in the HAZ.
Can FDSiCr be formed, bent or molded?
Cold coil at spring index ≥4, then stress relieve 350–420 °C for 20–40 min and preset; avoid sharp bends and tight hook radii.
FDSiCr 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, temper resistance | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Cumax, residual | ≤ 0.12 | |
| Fe | balance |
What surface finishes work on FDSiCr?
Shot peen for fatigue duty; protect with zinc phosphate + oil, Zn or Zn-Ni plating with 190–220 °C hydrogen bake-out within 4 h, or epoxy/powder coating.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel FDSiCr in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- A401
How much does FDSiCr cost?
FDSiCr is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FDSiCr — frequently asked
What is FDSiCr used for?
FDSiCr is typically used for valve springs, high-fatigue mechanical springs and suspension-related small springs. In short: valve-spring grade wire; good relaxation resistance; 250 °C service capability.
What is the yield strength of FDSiCr?
FDSiCr has a typical yield strength of 1,680 MPa (244 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is FDSiCr easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Not a machining grade in the OT condition (~54 HRC) — grind or use in the annealed rod condition, then quench and temper.
Can FDSiCr be welded?
Not readily — weldability is rated poor (15/100). Essentially unweldable in service condition; only resistance/laser tack joints with immediate local re-temper, otherwise cracking in the HAZ.
What surface finishes work on FDSiCr?
Shot peen for fatigue duty; protect with zinc phosphate + oil, Zn or Zn-Ni plating with 190–220 °C hydrogen bake-out within 4 h, or epoxy/powder coating.
Can FDSiCr be formed, bent or molded?
Cold coil at spring index ≥4, then stress relieve 350–420 °C for 20–40 min and preset; avoid sharp bends and tight hook radii.
What is the maximum service temperature of FDSiCr?
FDSiCr 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 FDSiCr-OT and FDSiCr-ANN?
OT is the default condition — standard stocked condition: coil the spring directly from the wire, then low-temperature stress relieve. ANN: intermediate supply condition for cold heading, machining or hot coiling followed by full quench and temper. Yield strength is 1,680 MPa in OT versus 500 MPa in ANN.
How much does FDSiCr cost?
FDSiCr is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- EN 10270-2 Steel wire for mechanical springs — Part 2: Oil hardened and tempered spring steel wire — CEN (2012)
- ASTM A401 Standard Specification for Steel Wire, Chromium-Silicon Alloy — ASTM (2020)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- EN 13906-1 Cylindrical helical springs — compression springs (design moduli) — CEN (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.