S690QL1
1.8988High-strength quenched and tempered fine-grained structural steel with minimum yield strength 690 MPa and guaranteed impact toughness at -60°C (QL1 designation). The most demanding low-temperature variant of the S690 series. Used for arctic offshore structures, mobile cranes operating in extreme cold, heavy lifting equipment, and safety-critical structural applications requiring both high strength and exceptional low-temperature toughness.
Chemical composition comparison (wt%)
Side-by-side: S690QL1 (EN) (EN 10025-6:2004) vs ASTM
| Element | S690QL1 (EN) | ASTM | Overlap |
|---|---|---|---|
| C | ≤ 0.2% | — | — |
| Si | ≤ 0.8% | — | — |
| Mn | ≤ 1.7% | — | — |
| P | ≤ 0.02% | — | — |
| S | ≤ 0.01% | — | — |
| Cr | ≤ 1.5% | — | — |
| Mo | ≤ 0.7% | — | — |
| Ni | ≤ 2% | — | — |
| V | ≤ 0.12% | — | — |
| B | ≤ 0.005% | — | — |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 770–940 | MPa |
| Yield Strength | ≥ 690 | MPa |
| Elongation | ≥ 14 | % |
| 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 | — | — |
| stress_relief | 530–580 °C | furnace | — | Max 580°C to avoid softening |
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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