Steel TDSiCr OT+SR
Heat-treated state
OT+SR = oT + stress relieved after coiling
Standard post-coiling treatment: raises elastic limit and reduces set/relaxation.
Values for the OT+SR condition
Other TDSiCr tempers and conditions
TDSiCr is listed in 8 conditions; see the grade overview at TDSiCr.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OT, d > 10.0 mm | Heaviest supplied sizes; lowest strength class, best cross-section toughness. | 1,510 | 1,700 | 8 | 49 HRC | 5.7 % IACS |
OT, d = 8.00–10.00 mm | Large suspension / off-highway springs, usually hot- or warm-coiled aids. | 1,580 | 1,780 | 7 | 51 HRC | 5.7 % IACS |
OT, d = 5.00–8.00 mm | Heavier springs where strength drops with section but toughness improves. | 1,660 | 1,870 | 7 | 52 HRC | 5.7 % IACS |
OT, d = 3.00–5.00 mm | Mid-size band for automotive clutch, seat and machinery springs. | 1,740 | 1,960 | 6 | 54 HRC | 5.7 % IACS |
OT-D1.6-3.0Default OT, d = 1.60–3.00 mm | Default stocked size band for general dynamic compression and torsion springs. | 1,830 | 2,060 | 6 | 55 HRC | 5.7 % IACS |
OT+SRThis page OT + stress relieved after coiling | Standard post-coiling treatment: raises elastic limit and reduces set/relaxation. | 1,880 | 2,020 | 6 | 54 HRC | 5.7 % IACS |
OT + shot peened (and stress relieved) spring | Pick for high-cycle dynamic springs: compressive surface stress greatly raises fatigue life. | 1,880 | 2,020 | 6 | 55 HRC | 5.7 % IACS |
OT, d = 0.50–1.60 mm | Highest strength class; small clutch, latch and instrument springs. | 1,960 | 2,200 | 5 | 57 HRC | 5.7 % IACS |
What is TDSiCr OT+SR?
TDSiCr OT+SR is TDSiCr heat treated to OT+SR — standard post-coiling treatment: raises elastic limit and reduces set/relaxation. TDSiCr OT+SR has a yield strength of 1,880 MPa (273 ksi) and a tensile strength of 2,020 MPa (293 ksi) — stronger than 99% of steel grades. Elongation at break is 6% and the elastic modulus is 206 GPa (29.9 Msi). TDSiCr OT+SR 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-D1.6-3.0 is the default condition FabDigit quotes; OT+SR is available on request or by drawing note.
Advantages
- High strength — 1,880 MPa (273 ksi), better than 99% of steel grades
Limitations
- Difficult to machine — 11/100, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low fracture toughness — 42 MPa·√m (38.2 ksi·√in), worse than 92% of steel grades
TDSiCr OT+SR properties
Typical room-temperature values for TDSiCr OT+SR; 22 are specific to this condition. Other listed values are TDSiCr reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
TDSiCr OT+SR 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).
Mechanical15
TDSiCr OT+SR has a yield strength of 1,880 MPa (273 ksi) and a tensile strength of 2,020 MPa (293 ksi) — stronger than 99% of steel grades. Elongation at break is 6% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
TDSiCr OT+SR is rated for continuous service to 200°C (392 °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 µm/m·K (6.67 µin/in·°F).
Electrical3
TDSiCr OT+SR conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of TDSiCr OT+SR takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
TDSiCr OT+SR's machinability is not recommended (11/100, worse than 99% of steel grades); weldability not recommended (10/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with TDSiCr OT+SR
Is TDSiCr easy to machine?
Supplied at 50–57 HRC — effectively not machinable; use grinding, cut-off wheels or ends ground after coiling.
Can TDSiCr be welded?
Not weldable in the spring condition (0.55 %C, martensite cracking and local tempering); use mechanical ends or hooks formed from the wire itself.
Can TDSiCr be formed, bent or molded?
Cold coil with generous mandrel ratio (D/d ≥ 4), then stress relieve at 380–420 °C; avoid nicks and tooling marks that become fatigue initiators.
What surface finishes work on TDSiCr?
Shot peen for dynamic duty, then phosphate + oil, zinc-flake (Dacromet/Geomet) or powder coat; avoid acid pickling/electroplating without bake-out due to hydrogen embrittlement risk.
TDSiCr 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 |
| Siraises relaxation resistance | 1.2 – 1.6 | 1.4 |
| Mn | 0.5 – 0.9 | 0.7 |
| Cr | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cu | ≤ 0.2 | — |
| Fe | balance | — |
TDSiCr OT+SR — frequently asked
What is TDSiCr OT+SR used for?
TDSiCr OT+SR is typically used for mechanical springs, clutch springs, general compression springs and torsion springs. In short: stronger than carbon spring wire; general-purpose oil-tempered wire; non-valve spring grade.
What is the yield strength of TDSiCr OT+SR?
TDSiCr OT+SR has a typical yield strength of 1,880 MPa (273 ksi) and a tensile strength of 2,020 MPa (293 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is TDSiCr OT+SR easy to machine?
Not especially — machinability is rated not recommended (11/100, worse than 99% of steel grades). Supplied at 50–57 HRC — effectively not machinable; use grinding, cut-off wheels or ends ground after coiling.
Can TDSiCr OT+SR be welded?
Not readily — weldability is rated not recommended (10/100). Not weldable in the spring condition (0.55 %C, martensite cracking and local tempering); use mechanical ends or hooks formed from the wire itself.
What surface finishes work on TDSiCr OT+SR?
Shot peen for dynamic duty, then phosphate + oil, zinc-flake (Dacromet/Geomet) or powder coat; avoid acid pickling/electroplating without bake-out due to hydrogen embrittlement risk.
Can TDSiCr OT+SR be formed, bent or molded?
Cold coil with generous mandrel ratio (D/d ≥ 4), then stress relieve at 380–420 °C; avoid nicks and tooling marks that become fatigue initiators.
What is the maximum service temperature of TDSiCr OT+SR?
TDSiCr OT+SR is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
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 (E, G values) — CEN (2013)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys (spring steels) — ASM International (1990)
- Oil tempered Si-Cr spring wire datasheets — Suzuki Garphyttan / Kiswire (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.