Steel 56Si7
EN 56Si7
56Si7 (1.5026, AISI 9255) is the higher-carbon member of the Si7 spring steel group, reaching about 1450 MPa yield, 1650 MPa tensile and 465 HB (48 HRC) in the quenched and tempered state, and it is also stocked as +QT+SP shot-peened material.
Reference datasheet — 56Si7 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 +QT condition
56Si7 tempers and conditions
56Si7 is supplied in 8 conditions, soft to hard. +QT is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest, most ductile delivery state — pick it for cold coiling, deep drawing or heavy cold upsetting before hardening. | 420 | 720 | 20 | 205 HB | — |
Treated for high shearability | Bar/coil heat treated to a low, uniform hardness so blanks can be cold sheared or cropped without cracking before hot/warm forming. | 440 | 760 | 18 | 17 HRC | 6 % IACS |
Annealed | Choose for machining, straightening or bar/strip stock that will be hardened after forming. | 470 | 800 | 16 | 230 HB | 42 W/m·K |
Treated to a specified core hardenability band | Same soft delivery state as +H but with the hardenability band certified on the core of heavy sections such as thick leaf-spring or torsion-bar stock. | 510 | 880 | 14 | 23 HRC | 5.9 % IACS |
Treated to a specified hardenability band | Order this when the mill must certify an end-quench (Jominy) hardenability band; supplied soft/hot-rolled and hardened by the spring maker. | 520 | 900 | 14 | 25 HRC | 5.9 % IACS |
Hot rolled | Cheapest mill state for hot-coiled springs that will be austenitized straight from the forming heat; hardness and decarburization vary. | 570 | 1,000 | 12 | 29 HRC | 5.8 % IACS |
+QTDefault Quenched and tempered | Standard finished spring condition: oil-quenched from ~860 °C and tempered 400–480 °C for maximum elastic limit and fatigue life. | 1,450 | 1,650 | 7 | 48 HRC | — |
+QT + shot peened | Q&T springs that are shot- or stress-peened to add compressive surface stress — the standard choice for high-cycle automotive suspension springs. | 1,450 | 1,650 | 6 | 49 HRC | 5.7 % IACS |
What is 56Si7?
56Si7 (1.5026, AISI 9255) is the higher-carbon member of the Si7 spring steel group, reaching about 1450 MPa yield, 1650 MPa tensile and 465 HB (48 HRC) in the quenched and tempered state, and it is also stocked as +QT+SP shot-peened material. It is chosen for coil and leaf springs where fatigue and elastic strength govern, in flat bar, round bar and wire forms. Elongation falls to 7 %, formability and machinability are low, service is capped at 250 °C and there is no corrosion resistance or practical weldability. Use 46Si7 where slightly better formability is needed, or 51CrV4 for thicker sections. 56Si7 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F). 56Si7 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Elongation at break is 7% and the elastic modulus is 206 GPa (29.9 Msi).
What is 56Si7 used for?
- heavy-duty coil springs
- leaf springs
- clutch springs
Advantages
- High strength — 1,450 MPa (210 ksi), better than 97% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 7%, worse than 96% of steel grades
- Limited formability — 12/100, worse than 92% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
56Si7 properties
Typical room-temperature values for 56Si7-+QT; bars are the position among steel grades.
Physical3
56Si7 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
56Si7 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Elongation at break is 7% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
56Si7 is rated for continuous service to 250°C (482 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
56Si7 conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 56Si7 takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
56Si7's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (15/100); formability not recommended (12/100).
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. 56Si7 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 56Si7
Is 56Si7 easy to machine?
Machine only in the +A/+AC/+S soft states with rigid setups and carbide tooling — the high silicon is abrasive and the Q&T condition (≈48 HRC) needs grinding or CBN.
Can 56Si7 be welded?
Effectively non-weldable for load-bearing joints; if unavoidable, preheat 250–350 °C, low-hydrogen filler and immediate post-weld temper, and never weld a finished spring.
Can 56Si7 be formed, bent or molded?
Hot coil/roll at 850–1000 °C, or cold form only from spheroidize-annealed stock followed by austenitize 850–870 °C, oil quench and temper 400–480 °C; guard against surface decarburization.
56Si7 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 |
|---|---|---|
| CAISI 9255 range 0.51–0.59 | 0.52 – 0.6 | 0.56 |
| SiAISI 9255 range 1.80–2.20 | 1.6 – 2 | 1.8 |
| Mn | 0.6 – 1 | 0.8 |
| Crresidual limit | ≤ 0.4 | 0.15 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on 56Si7?
No corrosion resistance — shot peen, then phosphate + epoxy paint, powder coat or zinc-flake; avoid acid pickling and electrolytic zinc plating without baking due to hydrogen embrittlement.
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 56Si7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 1.5026
- Similar grades
- 9255
How much does 56Si7 cost?
56Si7 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
56Si7 — frequently asked
What is 56Si7 used for?
56Si7 is typically used for heavy-duty coil springs, leaf springs and clutch springs. In short: highest strength of the Si7 springs; 1650 MPa at 48 HRC; shot-peened stock available.
What is the yield strength of 56Si7?
56Si7 has a typical yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 56Si7 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine only in the +A/+AC/+S soft states with rigid setups and carbide tooling — the high silicon is abrasive and the Q&T condition (≈48 HRC) needs grinding or CBN.
Can 56Si7 be welded?
Not readily — weldability is rated poor (15/100). Effectively non-weldable for load-bearing joints; if unavoidable, preheat 250–350 °C, low-hydrogen filler and immediate post-weld temper, and never weld a finished spring.
What surface finishes work on 56Si7?
No corrosion resistance — shot peen, then phosphate + epoxy paint, powder coat or zinc-flake; avoid acid pickling and electrolytic zinc plating without baking due to hydrogen embrittlement.
Can 56Si7 be formed, bent or molded?
Hot coil/roll at 850–1000 °C, or cold form only from spheroidize-annealed stock followed by austenitize 850–870 °C, oil quench and temper 400–480 °C; guard against surface decarburization.
What is the maximum service temperature of 56Si7?
56Si7 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 56Si7 cost?
56Si7 is a budget-cost steel ($), cheaper than about 90% 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 10089 — Hot-rolled steels for quenched and tempered springs — CEN (2002)
- EN 10083-1 — Steels for quenching and tempering: delivery conditions (+A, +AC, +S, +QT, +H) — CEN (2006)
- DIN 17221 — Hot-rolled steels for quenched and tempered springs (56Si7 / 1.5026) — DIN (1988)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (spring steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture (spring steel fatigue data) — ASM International (1996)
- SAE J404 / GB/T 1222 — spring steel chemical compositions (9255, 60Si2Mn analogues) — SAE / SAC (2016)
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.