C55R
1.1209Unalloyed special steel with controlled sulfur (R grade, S 0.020–0.040%) and 0.55% carbon for improved machinability. Same base composition as C55E but with intentional sulfur for better chip formation. Used for high-volume machined components requiring moderate to high strength: shafts, axles, gears, and wear-resistant machine parts.
Chemical composition comparison (wt%)
Side-by-side: C55R (EN) (EN 10083-2:2006) vs ASTM
| Element | C55R (EN) | ASTM | Overlap |
|---|---|---|---|
| C | 0.52–0.6% | — | — |
| Si | ≤ 0.4% | — | — |
| Mn | 0.6–0.9% | — | — |
| P | ≤ 0.025% | — | — |
| S | 0.02–0.04% | — | — |
Mechanical properties
Normalized
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 650–800 | MPa |
| Yield Strength | ≥ 370 | MPa |
| Elongation | ≥ 14 | % |
| Hardness HB | 195–240 | HB |
| Density | ≥ 7.85 | g/cm3 |
| Elastic Modulus | ≥ 210 | GPa |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| normalizing | 830–860 °C | air | — | — |
| quenching | 810–840 °C | oil | — | — |
| tempering | 550–660 °C | air | — | — |
| annealing | 650–700 °C | furnace | — | Soft annealing max 225 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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