S620Q
1.8914Quenched and tempered fine-grained structural steel with minimum yield strength 620 MPa. Q designation indicates impact testing at room temperature. High-performance grade bridging the gap between S550 and S690. Used for heavy-duty crane booms, mining equipment, structural components requiring weight optimization, and safety-critical applications.
Chemical composition comparison (wt%)
Side-by-side: S620Q (EN) (EN 10025-6:2004) vs ASTM
| Element | S620Q (EN) | ASTM | Overlap |
|---|---|---|---|
| C | ≤ 0.2% | — | — |
| Si | ≤ 0.8% | — | — |
| Mn | ≤ 1.7% | — | — |
| P | ≤ 0.025% | — | — |
| S | ≤ 0.015% | — | — |
| Cr | ≤ 1.5% | — | — |
| Mo | ≤ 0.7% | — | — |
| Ni | ≤ 2% | — | — |
| V | ≤ 0.12% | — | — |
| B | ≤ 0.005% | — | — |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 700–890 | MPa |
| Yield Strength | ≥ 620 | MPa |
| Elongation | ≥ 15 | % |
| impact_kv | ≥ 30 | J |
| Density | ≥ 7.85 | g/cm3 |
| Elastic Modulus | ≥ 210 | GPa |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 880–940 °C | water | — | Quenched and tempered at mill |
| tempering | 550–680 °C | air | — | — |
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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