S690QL1 steel is a high-strength, quenched and tempered structural steel plate, defined by the EN 10025-6 standard. It is primarily used for demanding applications that require exceptional strength and toughness, particularly in cold environments.
Key Properties
The 'S' in S690QL1 stands for structural steel, '690' indicates the minimum yield strength in MPa, 'Q' means it is supplied in the quenched and tempered condition, and 'L1' specifies that it has enhanced impact toughness tested at -60°C.
| Property | Value (for nominal thickness ≤ 50mm) | Source |
|---|---|---|
| Minimum Yield Strength | 690 MPa | |
| Tensile Strength | 770 - 940 MPa | |
| Elongation | Minimum 14% | |
| Impact Toughness | Minimum 30 J at -60°C (Transverse) |
Common Applications
S690QL1 steel is known for its high strength-to-weight ratio, which allows for lighter designs without compromising safety or performance. Its superior mechanical properties make it suitable for:
Heavy engineering and construction machinery
Cranes and lifting equipment
Bridges and offshore platforms
Mining equipment
Pressure vessels and structural components
Chemical composition % of steel S690QL1 (1.8988): EN 10025-6-2004
| C | Si | Mn | Ni | P | S | Cr | Mo | V | N | Nb | Ti | Cu | Zr | B | CEV |
| max 0.2 | max 0.8 | max 1.7 | max 2 | max 0.02 | max 0.01 | max 1.5 | max 0.7 | max 0.12 | max 0.015 | max 0.06 | max 0.05 | max 0.5 | max 0.15 | max 0.005 | max 0.83 |
What does "QL1" mean in S690QL1?
The "QL1" in the steel grade S690QL1 is a sub-grade designation defined by the European standard EN 10025-6. It specifies the required impact toughness (toughness class) at low temperatures.
Here's the breakdown:
Q: Stands for "Quenched and Tempered" – the heat treatment process that gives the steel its high strength and toughness.
L: Stands for "Low Temperature" service, meaning the steel is guaranteed to maintain toughness in freezing conditions.
1: The number "1" indicates the specific temperature and minimum impact energy requirement for the Charpy V-notch test. For S690QL1, this means:
Test Temperature: -60°C (-76°F)
Minimum Impact Energy: ≥ 40 Joules (average of 3 tests)
In summary:
S690QL1 is a quenched and tempered steel with 690 MPa yield strength, specially certified to deliver at least 40 Joules of impact energy at -60°C. This makes it suitable for the most extreme cold-region applications, such as Arctic offshore structures, critical components in polar exploration, or specialized machinery operating in deep cold where failure is not an option.
Comparison with other common sub-grades:
S690Q: Typically tested at 0°C.
S690QL: Tested at -40°C with a requirement of ≥ 27 J.
S690QL1: Tested at -60°C with a requirement of ≥ 40 J (higher toughness at a lower temperature).
What is S690QL1 steel?
S690QL1 is a high-strength quenched and tempered structural steel grade with a minimum yield strength of 690 MPa, optimized for enhanced toughness at low temperatures (down to -60°C).
What does "QL1" mean in S690QL1?
The "QL1" indicates a sub-grade with specific impact toughness requirements at -60°C, ensuring higher resistance to brittle fracture in extreme cold environments.
What are the main applications of S690QL1?
It is used in critical components for Arctic engineering, offshore platforms, wind turbine towers in cold climates, and heavy-duty mining equipment operating below -40°C.
How does S690QL1 differ from S690QL?
S690QL1 guarantees impact toughness at a lower temperature (-60°C) compared to S690QL (typically -40°C), making it suitable for more severe cold conditions.
What is the chemical composition of S690QL1?
It contains low-carbon alloying elements like manganese, silicon, nickel, chromium, molybdenum, and vanadium, with strict control of impurities to ensure weldability and toughness.
How to weld S690QL1 steel correctly?
Welding requires low-hydrogen electrodes, preheating (100-150°C), controlled heat input, and post-weld stress relief to maintain toughness and prevent hydrogen-induced cracking.
Is S690QL1 corrosion resistant?
No, S690QL1 is not inherently corrosion-resistant. It requires protective coatings (e.g., galvanizing or painting) for use in corrosive environments.
What standards apply to S690QL1?
It is defined under European standard EN 10025-6, with additional specifications for low-temperature impact testing and quality levels.
Can S690QL1 be machined easily?
Machining S690QL1 is challenging due to its high strength; it requires rigid tools, adequate cooling, and optimized cutting parameters to avoid excessive tool wear.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
