C70S
1.1232High-carbon unalloyed steel for springs and cutting tools with 0.65–0.75% carbon. Good combination of hardness and toughness compared to higher-carbon grades. Used for coil springs, leaf springs, saw blades, chisels, and shear blades. Can achieve 50–56 HRC after proper heat treatment. The S suffix indicates suitability for spring applications per EN 10132-4.
Chemical composition comparison (wt%)
Side-by-side: C70S (EN) (EN 10132-4) vs ASTM
| Element | C70S (EN) | ASTM | Overlap |
|---|---|---|---|
| C | 0.65–0.75% | — | — |
| Si | 0.15–0.35% | — | — |
| Mn | 0.5–0.8% | — | — |
| P | ≤ 0.025% | — | — |
| S | ≤ 0.025% | — | — |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Density | ≥ 7.85 | g/cm3 |
| Elastic Modulus | ≥ 210 | GPa |
| Tensile Strength | 1000–1250 | MPa |
| Yield Strength | ≥ 800 | MPa |
| Elongation | ≥ 8 | % |
| Hardness HRC | 50–56 | HRC |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 790–830 °C | water | — | Or oil quench for reduced distortion |
| tempering | 350–500 °C | air | — | Spring temper |
| annealing | 680–710 °C | furnace | — | Soft annealing max 200 HB |
Related materials
S960QL
1.8933Ultra-high-strength quenched and tempered fine-grained structural steel with minimum yield strength 960 MPa. QL designation indicates impact testing at -40°C. Used for mobile cranes, heavy lift equipment, offshore wind turbine towers, mining machinery, and weight-critical structural applications. Weldable with appropriate precautions (preheating, low hydrogen). Dramatically reduces component weight compared to conventional structural steels.
P355NH
1.0565Weldable fine-grained non-alloy steel for pressure vessels with minimum yield strength 355 MPa. NH designation indicates normalized condition with specified elevated temperature properties and impact testing at -20°C. Very widely used pressure vessel grade for boilers, storage tanks, heat exchangers, and pipes transporting hot liquids and pressurized gases. Good weldability and resistance to brittle cracking.
C45E
1.1191Unalloyed special steel with controlled chemistry (E grade) and 0.42–0.50% carbon. Tighter P and S limits than standard C45 for improved consistency. The most widely used medium-carbon steel for quenching and tempering. Good balance of strength (620–850 MPa QT) and toughness. Through-hardening up to ø60mm. Surface hardening by induction to HRC 58. Used for shafts, gears, bolts, connecting rods, crankshafts, and general machine parts.
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