Overheating sensitive is low but there is a great decarburizing tendency.Especially in the high content of Si and Carbon,the carbon is prone to be graphited which cause the steel brittle.Used for the damping plate spring ,coil spring,cylinder valve spring and heat-resistant spring within 250 in the car,tractor and locomotive.
| Chemical composition: | | | | | |
| C | Mn | Si | S | P | Cr |
| 0.52-0.60 | 0.60-0.90 | 1.50-2.00 | ≤0.035 | ≤0.035 | ≤0.35 |
| Ni | Cu | | | | |
| ≤0.35 | ≤0.25 | | | | |
| | | | | |
| Mechanical Properties: |
| Intensity of tensionσb(MPa):≥1274(130) |
| Yield stressσs(MPa):≥1176(120) |
| Tensile stretch:δ10(%)≥6 |
| Section shrinkage:Ψ(%)≥30 |
| Hardness: hot rolling ≤302HB; cold drawing and heat treatment≤321HB |
| Heat treatment regime and metallurgical structure: |
| Heat treatment regime: quenched::870±20, oil cooling; tempering:480±50 (if special condition,±30) |
| Metallurgical structure: troostite |
| Delivery condition: Heat-treatment or not heat-treatment for hot rolling steel. Heat-treatment for cold drawing steel. |