A chromium-bearing spring steel (AISI 5160) with about 0.60% carbon plus chromium for deeper oil hardenability. It is the standard American grade for heavy automotive leaf and coil springs where plain carbon 65Mn would not through-harden.
What Is 5160 Spring Steel?
5160 is an AISI chromium spring steel. The ~0.8% chromium lifts hardenability so bars and plate through-harden in oil, giving the uniform hardness a heavy suspension spring needs across a thick section.
It is the workhorse for truck and trailer leaf springs, large coil springs and railway suspension. It is not stainless and must be protected against corrosion 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, wear plates |
| Hot-rolled bar | Hot rolled / cold drawn | 10 – 120 mm | Coil springs, forgings |
| Hardened & tempered strip | Q&T | 0.5 – 8 mm | Heavy washers, blades |
| Cold-drawn wire | Annealed / oil-tempered | 1 – 14 mm | Coil springs |
Chemical Composition (AISI 5160)
| C | Mn | Si | Cr | P max | S max |
|---|---|---|---|---|---|
| 0.56 – 0.64 | 0.75 – 1.00 | 0.15 – 0.35 | 0.70 – 0.90 | 0.035 | 0.040 |
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 5160 after oil quenching and tempering near 480 °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 | 1220 – 1470 MPa | ≥ 1070 MPa | ≥ 8 % | 44 – 49 HRC |
| Oil-tempered wire | 1500 – 1900 MPa | — | — | per size class |
Equivalent Grades
| Standard | Designation |
|---|---|
| USA AISI / SAE | 5160 |
| Europe EN | 56Cr7 (similar) |
| Japan JIS G4801 | SUP9 (similar) |
| China GB/T 1222 | 55Cr3 (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 machining.
830 – 860 °C, oil. Full hardenability for thick plate.
400 – 540 °C by required hardness; ~480 °C gives the usual 44 – 49 HRC leaf-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 5160 Spring Steel
The main use; chromium lets thick plate through-harden in oil.
Truck, trailer and railway suspension coils.
Thick sections that must harden uniformly.
Tines, sweeps and linkage springs in heavy duty.
Hardened-and-tempered strip at 44 – 49 HRC.
From 5160 bar for high-load machined springs.
5160 Spring Steel vs Alternative Grades
| Grade | vs 5160 Spring Steel | Choose It When |
|---|---|---|
| 5160 | — | Thick leaf/coil springs needing oil through-hardening (US spec). |
| 65Mn | Cheaper, lower hardenability | Light leaf, strip and wire springs |
| SUP9 / 55Cr3 | Very close chemistry | When JIS or EN spec is called out |
| 50CrV4 | Adds V for fatigue and temper | High-cycle or warm engine springs |
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 5160 equivalent to?
Closest are JIS SUP9, European 56Cr7 and China 55Cr3; all chromium spring steels of similar carbon. Confirm against the certificate for critical parts.
Is 5160 good for leaf springs?
Yes — its chromium gives the hardenability to fully oil-quench thick plate, exactly what heavy leaf springs need.
What hardness does 5160 reach?
Typically 44 – 49 HRC in the quenched-and-tempered condition.
5160 vs 65Mn?
5160 hardens thicker sections and lasts longer under load, at higher cost; 65Mn suits light, low-cost springs.
What is the minimum order quantity?
Mill lots typically start at 500 kg per item; trial plate and bar are often from stock.
Related Products
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