Products Description
S690QL is a high-strength structural steel grade classified under the EN 10025-6 standard. It is primarily a quenched and tempered steel, known for its excellent mechanical properties and weldability.
The main alloying elements in S690QL include carbon, manganese, silicon, and small amounts of chromium, molybdenum, and vanadium.
These elements contribute significantly to the steel's strength, toughness, and overall performance in demanding applications.
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.12 - 0.20 |
| Mn (Manganese) | 1.00 - 1.60 |
| Si (Silicon) | 0.10 - 0.50 |
| Cr (Chromium) | 0.20 - 0.50 |
| Mo (Molybdenum) | 0.10 - 0.30 |
| V (Vanadium) | 0.02 - 0.10 |
| P (Phosphorus) | ≤ 0.025 |
| S (Sulfur) | ≤ 0.015 |
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Quenched & Tempered | Room Temp | 690 - 770 MPa | 100 - 112 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Quenched & Tempered | Room Temp | ≥ 690 MPa | ≥ 100 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | Room Temp | ≥ 20% | ≥ 20% | ASTM E8 |
| Reduction of Area | Quenched & Tempered | Room Temp | ≥ 50% | ≥ 50% | ASTM E8 |
| Hardness (Brinell) | Quenched & Tempered | Room Temp | 200 - 250 HB | 200 - 250 HB | ASTM E10 |
| Impact Strength | Quenched & Tempered | -40°C (-40°F) | ≥ 27 J | ≥ 20 ft-lbf | ASTM E23 |
Mechanical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | Room Temp | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1420 - 1540 °C | 2590 - 2810 °F |
| Thermal Conductivity | Room Temp | 50 W/m·K | 34.5 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temp | 0.46 kJ/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.0000017 Ω·m | 0.0000017 Ω·in |
Applications of S690QL High Yield Structural Steel
S690QL high yield structural steel is a quenched and tempered (Q&T) grade with a minimum yield strength of 690 MPa and a tensile strength of 770–940 MPa. It combines excellent toughness with good weldability, making it widely used in high-load and lightweight engineering applications.
Typical applications include:
- Heavy Transportation
Used in the manufacturing of heavy trucks, semi-trailers, and construction transport vehicle frames and load-bearing beams.
Compared with standard S355 steel, S690QL enables a 30–40% weight reduction, significantly improving load efficiency and fuel economy.
- Machine Building
Suitable for mining machinery, excavators, booms, crushers, and other industrial equipment.
Maintains ≥ 30 J impact energy at –40 °C, ensuring safety and reliability in low-temperature and harsh environments.
- Steel Constructions
Extensively applied in bridges, high-rise buildings, stadiums, and industrial plants.
Its high strength allows the use of thinner plates while maintaining the same load-bearing capacity, leading to a 20–30% reduction in steel consumption and overall cost savings.
- Lifting Equipment
Commonly used for crane booms, mobile lifting equipment, and forklifts.
Provides yield strength above 700 MPa under extreme loads, ensuring long-term operational safety.
