Steel FDSiCr-ANN (Annealed)
Heat-treated state
Intermediate supply condition for cold heading, machining or hot coiling followed by full quench and temper.
Values for the ANN condition
Other FDSiCr tempers and conditions
FDSiCr is listed in 6 conditions; see the grade overview at FDSiCr.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNThis page 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-ANN?
FDSiCr-ANN is FDSiCr heat treated to ANN — intermediate supply condition for cold heading, machining or hot coiling followed by full quench and temper. FDSiCr-ANN has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 63% of steel grades. Elongation at break is 16% and the elastic modulus is 206 GPa (29.9 Msi). FDSiCr-ANN 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; ANN is available on request or by drawing note.
Advantages
- Forms and bends easily — 70/100, better than 86% of steel grades
FDSiCr-ANN properties
Typical room-temperature values for FDSiCr-ANN; 23 are specific to this condition. Other listed values are FDSiCr reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
FDSiCr-ANN 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-ANN has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 63% of steel grades. Elongation at break is 16% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
FDSiCr-ANN is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
FDSiCr-ANN conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of FDSiCr-ANN 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-ANN's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FDSiCr-ANN
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.
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.
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 | — |
FDSiCr-ANN — frequently asked
What is FDSiCr-ANN used for?
FDSiCr-ANN 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-ANN?
FDSiCr-ANN has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 63% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is FDSiCr-ANN easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% 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-ANN be welded?
With care — weldability is rated fair (35/100). 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-ANN?
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-ANN 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-ANN?
FDSiCr-ANN is rated for continuous use to about 400°C (752 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.