S690QL is a high-strength quenched and tempered structural steel with a minimum yield strength of 690 MPa, specifically designed to maintain good impact toughness at temperatures as low as -40°C, making it suitable for cold-climate applications like offshore platforms and Arctic machinery.
S690QL1 is a more advanced sub-grade of S690QL, offering even higher guaranteed impact toughness (≥40 J) at a significantly lower temperature of -60°C, ensuring superior resistance to brittle fracture in extreme polar environments or critically demanding cold-region engineering projects.
How does S690QL1 differ from S690QL?
The primary difference between S690QL1 and S690QL lies in their guaranteed impact toughness at different low temperatures, as defined by the European standard EN 10025-6. Both are quenched and tempered steels with a minimum yield strength of 690 MPa, but they are graded for different service environments.
Here is a clear comparison:
‑40°C (‑40°F)
‑60°C (‑76°F) Minimum Required Impact Energy (Charpy V‑notch, average of 3 tests) ≥ 27 Joules ≥ 40 Joules Typical Application Environment Cold climates, e.g., offshore in the North Sea, winter construction, mining in sub‑Arctic regions. Extreme Arctic/Antarctic conditions, deep‑cold offshore, cryogenic‑influenced structures, or where design codes demand higher toughness at lower temperatures. Toughness Assurance Level High toughness for most cold‑region applications. Even higher toughness at a significantly lower temperature, providing an extra safety margin against brittle fracture in the most severe conditions. Cost & Availability More commonly produced and stocked; relatively lower cost. More specialized, often made‑to‑order; premium priced due to stricter production controls and testing.
Key Takeaway:
S690QL is the standard low‑temperature grade for general cold‑climate applications (down to ‑40°C).
S690QL1 is a more stringent sub‑grade designed for extreme cold service (down to ‑60°C) with higher absorbed energy requirements. It is used where the operational environment is exceptionally harsh or where engineering standards specify higher toughness reserves.
In short, S690QL1 is a "colder‑tougher" version of S690QL, selected when the environment or safety regulations demand guaranteed performance below ‑40°C.
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.
