A silicon-manganese spring steel (China GB 60Si2MnA, close to JIS SUP7 and EN 56Si7). The high silicon lifts the elastic limit and resistance to set, so it is the domestic Chinese workhorse for heavy leaf and coil springs — the same role as AISI 9260.
What Is 60Si2MnA / SUP7 Spring Steel?
60Si2MnA is a Chinese silicon-manganese spring steel and the direct twin of JIS SUP7 and EN 56Si7 (and of AISI 9260). The ~1.6% silicon raises the elastic limit and flattens the stress-strain curve, so springs hold their set far better than plain carbon grades.
It is the standard for automotive and heavy leaf springs and large coil springs across Chinese manufacturing. It is not stainless and needs corrosion protection in service.
Supply Forms and Sizes
Every form is available soft-annealed (for further forming and machining) or heat-treated to your hardness window.
| Form | Condition | Size Range | Typical Use |
|---|---|---|---|
| Hot-rolled plate | Hot rolled / normalized | 3 – 50 mm | Leaf springs, blades |
| Hot-rolled bar | Hot rolled / cold drawn | 10 – 120 mm | Coil springs, forgings |
| Hardened & tempered strip | Q&T | 0.5 – 8 mm | Flat springs, washers |
| Cold-drawn wire | Annealed / oil-tempered | 1 – 14 mm | Coil springs |
Chemical Composition (GB/T 1222 (60Si2MnA))
| C | Si | Mn | Cr max | Ni max | P max | S max |
|---|---|---|---|---|---|---|
| 0.56 – 0.64 | 1.50 – 2.00 | 0.70 – 1.00 | 0.35 | 0.35 | 0.025 | 0.025 |
Heat analysis is reported on the mill certificate for every lot. If your drawing calls for tighter limits than the standard, flag it at enquiry — ladle-refined heats usually meet it without a surcharge.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Elastic modulus (E) | ~200 GPa |
| Shear modulus (G) | ~79 GPa |
| Thermal conductivity | ~40 W/m·K at room temperature |
| Coefficient of thermal expansion | ~12 ×10⁻₆ /K (20 – 200 °C) |
Mechanical Properties
Typical values for 60Si2MnA after oil quenching and tempering near 460 °C. The mill certificate is the binding document.
| Condition | Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|---|
| Hot rolled, annealed | ≥ 980 MPa | ≥ 830 MPa | ≥ 11 % | ≤ 321 HB |
| Q&T | 1180 – 1420 MPa | ≥ 1030 MPa | ≥ 9 % | 44 – 48 HRC |
| Oil-tempered wire | 1500 – 1900 MPa | — | — | per size class |
Equivalent Grades
| Standard | Designation |
|---|---|
| China GB/T 1222 | 60Si2MnA |
| Japan JIS G4801 | SUP7 |
| Europe EN | 56Si7 (similar) |
| USA AISI | 9260 (similar) |
Heat Treatment and Processing
Preheat slowly, then raise to the grade forging range. Work above the lower limit and cool slowly after forging to avoid cracks.
780 – 840 °C, soak, furnace cool. Soft condition for forming and coiling.
840 – 870 °C, oil. The high Si needs care on decarburisation control.
400 – 520 °C by required hardness; ~460 °C gives the usual 44 – 48 HRC spring window.
After machining or forming, 200 – 350 °C for 1 – 2 hours, air cool, to stabilise dimensions and relieve residual stress.
Heat-treated bars and plates are supplied with the hardness and test certificate you specify. For critical parts we can control decarburisation depth and supply a spheroidized or soft-annealed structure on request.
Applications of 60Si2MnA / SUP7 Spring Steel
The classic use; high Si keeps the spring set under load.
Suspension and buffer springs for commercial vehicles.
Tines, sweeps and linkage springs in heavy duty.
Hardened-and-tempered strip at 44 – 48 HRC.
From 60Si2MnA bar for high-load machined springs.
Good edge and toughness for band tools.
60Si2MnA / SUP7 Spring Steel vs Alternative Grades
| Grade | vs 60Si2MnA / SUP7 Spring Steel | Choose It When |
|---|---|---|
| 60Si2MnA | — | Heavy Chinese leaf/coil springs; Si-Mn elastic limit. |
| 9260 | Same Si-Mn family (US) | When AISI 9260 is specified |
| 65Mn | Cheaper, lower Si | Light strip and wire springs |
| SUP9 / 55Cr3 | Higher hardenability | Thick leaf plate needing oil through-hardening |
Quality Control and Mill Certificates
Every shipment ships with an EN 10204 3.1 mill certificate covering heat chemical analysis, hardness and the mechanical test on record. On request we add: ultrasonic test on heavy bar and plate, magnetic particle inspection on machined surfaces, and third-party inspection (SGS / BV) before loading. Dimensional tolerances follow the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
What is 60Si2MnA equivalent to?
JIS SUP7, European 56Si7 and AISI 9260 are the same silicon-manganese spring steel; confirm against the certificate for critical parts.
What is special about 60Si2MnA?
The ~1.6% silicon raises the elastic limit and resistance to set, so springs stay strong and keep their shape better than plain carbon grades.
What hardness does 60Si2MnA reach?
Typically 44 – 48 HRC in the quenched-and-tempered spring condition.
Does 60Si2MnA rust?
It is not stainless; keep it oiled or coated in humid or outdoor service.
What is the minimum order quantity?
Mill lots typically start at 500 kg per item; trial bar and plate are often from stock.
Related Products
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