Steel 56SiCr7 +CH
Heat-treated state
EN 56SiCr7
+CH = restricted / core hardenability guaranteed
Specify the narrowed core-hardenability band for high-volume spring production that needs batch-to-batch consistency of quenched hardness, here 49 HRC and 1500 MPa yield.
Values for the +CH condition
Other 56SiCr7 tempers and conditions
56SiCr7 is listed in 9 conditions; see the grade overview at 56SiCr7.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick spheroidize-annealed stock for cold heading, cold coiling and cold extrusion of spring blanks; globular carbides give the lowest hardness, 215 HB, and the best cold formability. | 430 | 740 | 18 | 215 HB | — |
Annealed | Order soft annealed to ferrite plus pearlite when the bar must be machined or cold coiled first; hardness is capped near 248 HB and strength is restored later by quench and temper. | 470 | 820 | 15 | 21 HRC | — |
Treated for high shearability | Choose when billets are cut on automatic cold-shear lines; structure and hardness near 250 HB are adjusted to give flat, crack-free shear faces on spring bar feedstock. | 500 | 850 | 14 | 24 HRC | 4.9 % IACS |
Supplied with specified hardenability | Order against a Jominy hardenability band when quenched hardness distribution must be guaranteed in large-section torsion bars and thick springs; as-delivered properties match annealed or hot-rolled bar. | 540 | 900 | 13 | 26 HRC | 4.9 % IACS |
Hot rolled | Cheapest as-delivered form: hot-rolled bar and coil at 285 HB, intended for hot coiling of springs that are quenched and tempered as a finished part afterwards. | 600 | 1,000 | 12 | 30 HRC | 4.9 % IACS |
Cold drawn | Use cold-drawn bright bar or wire for accurate size and bright surface at 800 MPa yield; ductility drops to 8% elongation and cold-coiled springs need a stress-relief temper. | 800 | 1,000 | 8 | 31 HRC | 4.9 % IACS |
+CHThis page Restricted / core hardenability guaranteed | Specify the narrowed core-hardenability band for high-volume spring production that needs batch-to-batch consistency of quenched hardness, here 49 HRC and 1500 MPa yield. | 1,500 | 1,700 | 8 | 49 HRC | 4.9 % IACS |
+QTDefault Quenched and tempered | Standard in-service spring condition: oil quench from 860–880 °C plus 420–480 °C temper gives 48–52 HRC and 1550 MPa yield for suspension springs and torsion bars, with no formability left. | 1,550 | 1,750 | 7 | 51 HRC | — |
Oil hardened and tempered spring wire | Choose fine wire oil quenched and tempered in line to 55 HRC for valve springs and highly stressed cold-coiled suspension springs that need only a low-temperature stress relief after coiling. | 1,780 | 1,980 | 6 | 55 HRC | — |
What is 56SiCr7 +CH?
56SiCr7 +CH is 56SiCr7 heat treated to +CH — specify the narrowed core-hardenability band for high-volume spring production that needs batch-to-batch consistency of quenched hardness, here 49 HRC and 1500 MPa yield. 56SiCr7 +CH has a yield strength of 1,500 MPa (218 ksi) and a tensile strength of 1,700 MPa (247 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 200 GPa (29 Msi). 56SiCr7 +CH has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,400°C (2,552 °F). +QT is the default condition FabDigit quotes; +CH is available on request or by drawing note.
Advantages
- High strength — 1,500 MPa (218 ksi), better than 97% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Difficult to machine — 24/100, worse than 95% of steel grades
- Low fracture toughness — 38 MPa·√m (34.6 ksi·√in), worse than 93% of steel grades
- Limited formability — 11/100, worse than 93% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
56SiCr7 +CH properties
Typical room-temperature values for 56SiCr7 +CH; 22 are specific to this condition. Other listed values are 56SiCr7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
56SiCr7 +CH has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
56SiCr7 +CH has a yield strength of 1,500 MPa (218 ksi) and a tensile strength of 1,700 MPa (247 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
56SiCr7 +CH 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 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
56SiCr7 +CH conducts electricity at 4.9 % IACS, worse than 82% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 56SiCr7 +CH takes about 28 MJ of energy and emits 2 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
56SiCr7 +CH's machinability is poor (24/100, worse than 95% of steel grades); weldability poor (15/100); formability not recommended (11/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 56SiCr7 +CH
Is 56SiCr7 easy to machine?
In the annealed (+A/+AC) condition turning and milling are normal with carbide tooling, at roughly 50 % of AISI 1212. After quenching and tempering to 50 HRC only grinding or CBN hard turning remain practical.
Can 56SiCr7 be welded?
The high carbon equivalent and high silicon content make the steel very prone to hardening cracks, so as a rule it is not welded. If unavoidable, preheat 250-350 °C, use low-hydrogen consumables and temper immediately after welding; joint fatigue strength drops sharply.
Can 56SiCr7 be formed, bent or molded?
Hot coil at 900-950 °C, then oil quench from 860-880 °C and temper at 420-480 °C. Fine wire is cold coiled from oil-tempered wire and stress relieved at 250 °C; finished springs must be shot peened, usually stress peened, to reach the design fatigue life.
What surface finishes work on 56SiCr7?
Control the decarburized layer during heat treatment (high silicon is sensitive) by using a protective atmosphere or leaving machining allowance for removal. Normal protection is shot peening plus phosphating, epoxy powder or zinc-flake coating; electroplated parts require strict hydrogen bake-out to prevent embrittlement.
56SiCr7 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 | 0.52 – 0.6 | 0.56 |
| Sihigh Si raises elastic limit and relaxation resistance; increases decarburisation risk | 1.6 – 2 | 1.8 |
| Mn | 0.7 – 1 | 0.85 |
| Crhardenability and temper resistance | 0.2 – 0.45 | 0.3 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
56SiCr7 +CH — frequently asked
What is 56SiCr7 +CH used for?
56SiCr7 +CH is typically used for heavy coil springs, valve springs, suspension coil springs, clutch and diaphragm springs, torsion bars and cold-coiled oil-tempered spring wire. In short: higher-alloy Si-Cr spring steel; fatigue-driven spring service; decarburization sensitive.
What is the yield strength of 56SiCr7 +CH?
56SiCr7 +CH has a typical yield strength of 1,500 MPa (218 ksi) and a tensile strength of 1,700 MPa (247 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 56SiCr7 +CH easy to machine?
Not especially — machinability is rated poor (24/100, worse than 95% of steel grades). In the annealed (+A/+AC) condition turning and milling are normal with carbide tooling, at roughly 50 % of AISI 1212. After quenching and tempering to 50 HRC only grinding or CBN hard turning remain practical.
Can 56SiCr7 +CH be welded?
Not readily — weldability is rated poor (15/100). The high carbon equivalent and high silicon content make the steel very prone to hardening cracks, so as a rule it is not welded. If unavoidable, preheat 250-350 °C, use low-hydrogen consumables and temper immediately after welding; joint fatigue strength drops sharply.
What surface finishes work on 56SiCr7 +CH?
Control the decarburized layer during heat treatment (high silicon is sensitive) by using a protective atmosphere or leaving machining allowance for removal. Normal protection is shot peening plus phosphating, epoxy powder or zinc-flake coating; electroplated parts require strict hydrogen bake-out to prevent embrittlement.
Can 56SiCr7 +CH be formed, bent or molded?
Hot coil at 900-950 °C, then oil quench from 860-880 °C and temper at 420-480 °C. Fine wire is cold coiled from oil-tempered wire and stress relieved at 250 °C; finished springs must be shot peened, usually stress peened, to reach the design fatigue life.
What is the maximum service temperature of 56SiCr7 +CH?
56SiCr7 +CH 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 56SiCr7 +QT and 56SiCr7-OT?
+QT is the default condition — standard in-service spring condition: oil quench from 860–880 °C plus 420–480 °C temper gives 48–52 HRC and 1550 MPa yield for suspension springs and torsion bars, with no formability left. OT: choose fine wire oil quenched and tempered in line to 55 HRC for valve springs and highly stressed cold-coiled suspension springs that need only a low-temperature stress relief after coiling. Yield strength is 1,550 MPa in +QT versus 1,780 MPa in OT.
Sources
- EN 10089 — Hot rolled steels for quenched and tempered springs — CEN (2002)
- EN 10270-2 — Steel wire for mechanical springs, oil hardened and tempered — CEN (2011)
- EN 10083-1/-3 — Steels for quenching and tempering (delivery conditions +A, +AC, +S, +H) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (spring steels) — ASM International (1990)
- EN 13906-1 — Cylindrical helical springs, compression springs design — CEN (2013)
- Si-Cr spring steel bar/wire datasheets (1.7106 / 55SiCr6-3 class) — European long-product mills (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.