Steel 54SiCr6 +TH
Hardness band
EN 54SiCr6
+TH = treated to a specified hardness range
Intermediate pre-treated bar supplied inside an agreed hardness window for predictable machining and straightening behaviour.
Values for the +TH condition
Other 54SiCr6 tempers and conditions
54SiCr6 is listed in 9 conditions; see the grade overview at 54SiCr6.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold heading, cold drawing or deep cold forming of blanks; spheroidized carbides give the softest, most ductile state. | 460 | 760 | 18 | 215 HB | — |
Annealed | Pick when the bar must be machined, straightened or cold formed before hardening; lowest strength, best chip formation. | 500 | 800 | 15 | 230 HB | — |
Treated for high shearability | Bar delivered at a controlled soft hardness so billets can be cold sheared without cracking prior to forging or hardening. | 500 | 830 | 14 | 21 HRC | 6.5 % IACS |
Treatable to a specified core hardness range | Delivered soft with a guarantee that after the agreed quench-and-temper cycle the core hardness falls in the contracted band (typically 44–50 HRC for this grade). | 520 | 860 | 13 | 47 HRC | 6.5 % IACS |
+THThis page Treated to a specified hardness range | Intermediate pre-treated bar supplied inside an agreed hardness window for predictable machining and straightening behaviour. | 560 | 900 | 13 | 26 HRC | 6.5 % IACS |
Supplied with specified hardenability (Jominy) band | Order this when the spring or component is hardened by the buyer and a guaranteed Jominy hardenability band is required; mechanical values are those of the as-rolled/annealed delivery state. | 620 | 1,000 | 12 | 60 HRC | 6 % IACS |
Hot rolled | Cheapest delivery form for spring makers who austenitize and quench the coiled or formed part themselves. | 650 | 1,050 | 11 | 32 HRC | 6 % IACS |
+QTDefault Quenched and tempered | Standard in-service condition for coil/leaf springs: oil quench from ~870 °C, temper 400–480 °C to 44–51 HRC for maximum elastic limit and fatigue life. | 1,550 | 1,750 | 7 | 48 HRC | — |
Oil hardened and tempered spring wire | Continuously oil-hardened-and-tempered wire based on this chemistry for valve springs and small high-duty coil springs; highest tensile of all forms. | 1,750 | 1,950 | 6 | 52 HRC | 6 % IACS |
What is 54SiCr6 +TH?
54SiCr6 +TH is 54SiCr6 heat treated to +TH — intermediate pre-treated bar supplied inside an agreed hardness window for predictable machining and straightening behaviour. 54SiCr6 +TH has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Elongation at break is 13% and the elastic modulus is 206 GPa (29.9 Msi). 54SiCr6 +TH has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). +QT is the default condition FabDigit quotes; +TH is available on request or by drawing note.
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
- Low electrical conductivity — 6.5 % IACS, worse than 77% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
54SiCr6 +TH properties
Typical room-temperature values for 54SiCr6 +TH; 22 are specific to this condition. Other listed values are 54SiCr6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
54SiCr6 +TH has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
54SiCr6 +TH has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Elongation at break is 13% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
54SiCr6 +TH is rated for continuous service to 250°C (482 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
54SiCr6 +TH conducts electricity at 6.5 % IACS, worse than 77% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 54SiCr6 +TH takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 35%.
Manufacturability8
54SiCr6 +TH's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (25/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 54SiCr6 +TH
Is 54SiCr6 easy to machine?
Machine in +A/+AC/+S condition with carbide tooling and rigid setups; at 45–50 HRC only grinding, hard turning with CBN, or EDM are practical.
Can 54SiCr6 be welded?
Essentially not recommended — high C+Si gives cold-crack sensitivity; if unavoidable use 250–350 °C preheat, low-hydrogen filler and immediate post-weld temper, accepting loss of spring properties.
Can 54SiCr6 be formed, bent or molded?
Hot coil/forge at 1000–1150 °C or cold form only in the spheroidized (+AC) state; oil-tempered wire is coiled cold and stress relieved at 380–420 °C.
What surface finishes work on 54SiCr6?
Shot peen springs after tempering for fatigue life, then phosphate + epoxy/zinc-flake coating; avoid acid pickling and electroplating at full strength due to hydrogen embrittlement risk.
54SiCr6 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 and temper resistance | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
54SiCr6 +TH — frequently asked
What is 54SiCr6 +TH used for?
54SiCr6 +TH is typically used for coil springs, leaf springs and torsion bars. In short: standard Si-Cr spring steel; high elastic limit; not for welded assemblies.
What is the yield strength of 54SiCr6 +TH?
54SiCr6 +TH has a typical yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 54SiCr6 +TH easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in +A/+AC/+S condition with carbide tooling and rigid setups; at 45–50 HRC only grinding, hard turning with CBN, or EDM are practical.
Can 54SiCr6 +TH be welded?
Not readily — weldability is rated poor (25/100). Essentially not recommended — high C+Si gives cold-crack sensitivity; if unavoidable use 250–350 °C preheat, low-hydrogen filler and immediate post-weld temper, accepting loss of spring properties.
What surface finishes work on 54SiCr6 +TH?
Shot peen springs after tempering for fatigue life, then phosphate + epoxy/zinc-flake coating; avoid acid pickling and electroplating at full strength due to hydrogen embrittlement risk.
Can 54SiCr6 +TH be formed, bent or molded?
Hot coil/forge at 1000–1150 °C or cold form only in the spheroidized (+AC) state; oil-tempered wire is coiled cold and stress relieved at 380–420 °C.
What is the maximum service temperature of 54SiCr6 +TH?
54SiCr6 +TH 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 54SiCr6 +QT and 54SiCr6-OT?
+QT is the default condition — standard in-service condition for coil/leaf springs: oil quench from ~870 °C, temper 400–480 °C to 44–51 HRC for maximum elastic limit and fatigue life. OT: continuously oil-hardened-and-tempered wire based on this chemistry for valve springs and small high-duty coil springs; highest tensile of all forms. Yield strength is 1,550 MPa in +QT versus 1,750 MPa in OT.
Sources
- EN 10089 — Hot rolled steels for quenched and tempered springs — CEN (2002)
- EN 10083-1/-3 — Steels for quenching and tempering (delivery conditions +A, +AC, +S, +H, +QT) — CEN (2006)
- EN 10270-2 — Steel wire for mechanical springs, oil hardened and tempered (VDSiCr) — CEN (2012)
- SAE J404 / J1249 — Chemical compositions and spring steel wire (9254) — SAE International (2009)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (spring steels) — ASM International (1990)
- Spring steel bar 54SiCr6 (1.7102) datasheets — Ovako / Sidenor / Böhler (2022)
- (54SiCr6/9254/60Si2Mn) — Mysteel / 1688 (2025)
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.