S690QL is a premium high-strength structural steel grade, which is manufactured in accordance with the European standard EN 10025-6 . It belongs to the quenched and tempered steel series, and each letter and number in its grade has specific meaning: S stands for structural steel, 690 represents its minimum yield strength of 690 MPa, Q refers to the quenching and tempering heat treatment process, and L indicates it has excellent performance in low notch toughness testing .
Chemical Composition
The chemical composition of S690QL includes:
Carbon (C): Max 0.20%
Silicon (Si): Max 0.80%
Manganese (Mn): Max 1.70%
Phosphorus (P): Max 0.020%
Sulfur (S): Max 0.010%
Chromium (Cr): Max 1.50%
Molybdenum (Mo): Max 0.70%
Nickel (Ni): Max 2.00%
Boron (B): Max 0.005%
These elements contribute to the steel's strength, toughness, and weldability.
Key Features of S690QL Ultra High Strength Steel
Exceptional Strength
High Yield Strength: The most notable feature of S690QL is its high yield strength of 690 MPa. This allows for the creation of lighter and thinner structures without compromising on strength or stability.
Enhanced Toughness: S690QL exhibits excellent toughness, even at low temperatures. This makes it suitable for use in harsh environments where standard steels might fail.
Superior Weldability
Despite its high strength, S690QL maintains good weldability. This is a crucial feature for structural applications, as it allows for the creation of complex structures without the risk of brittle weld joints.
High Ductility
Formability: The steel's high ductility ensures that it can be easily formed and fabricated into various shapes and sizes, meeting diverse engineering requirements.
Resistance to Wear and Tear
S690QL is known for its excellent resistance to abrasion and impact. This makes it ideal for applications where wear and tear are significant concerns, such as mining equipment, heavy machinery, and transportation vehicles.
It is a low-alloy steel with strict limits on chemical composition, the maximum content of carbon is 0.20%, and it is alloyed with elements such as manganese, chromium, nickel and molybdenum, which endows it with excellent comprehensive performance . In terms of mechanical properties, when the nominal thickness of S690QL is between 3mm and 50mm, its minimum yield strength is 690 MPa and tensile strength ranges from 770 to 940 MPa, with the minimum elongation after fracture reaching 14% . What's more, it has remarkable low-temperature toughness, its longitudinal V-notch impact energy can reach 50J at 0°C, 40J at -20°C and 30J at -40°C , which enables it to work stably in cold environments. It also has good weldability and can be processed by common welding methods, and its welded joints can maintain high strength .
Thanks to its superior performance, S690QL is widely used in various fields that require high structural reliability and load-bearing capacity. It is a key material for heavy engineering equipment like cranes and earthmoving machinery, can be applied to offshore platforms and marine structures to resist harsh marine environments, and is also used in large-span bridges, wind turbine supports and transport vehicle components . Its high strength-to-weight ratio can help optimize the structure design, reduce the overall weight of products while ensuring strength, and further improve energy efficiency .