GB Q690

Metallurgical Characteristics

GB Q690 is a low carbon, high strength structural steel featuring a fine-grained microstructure achieved through controlled rolling and accelerated cooling processes. The steel exhibits a predominantly ferritic-bainitic microstructure with dispersed carbide precipitates, providing excellent combination of strength, toughness, and weldability. The controlled addition of microalloying elements such as vanadium, niobium, and titanium enables precipitation strengthening and grain refinement.

Heat Treatment & Processing

MetalZenith employs advanced Thermomechanical Controlled Processing (TMCP) as the primary production route for GB Q690 steel. The process involves controlled rolling at temperatures between 850-950°C followed by accelerated cooling to achieve optimal mechanical properties. Alternative heat treatment options include normalizing at 900-950°C or quenching and tempering with austenitizing at 900-930°C, quenching in water or oil, and tempering at 580-650°C depending on specific application requirements.

Manufacturing Process Excellence

Our manufacturing process begins with careful selection of raw materials and precise charge calculation to achieve target chemistry. Steel is melted in electric arc furnaces with secondary refining through ladle furnace and vacuum degassing to ensure low inclusion content and optimal cleanliness. Continuous casting produces high-quality billets and slabs, which are subsequently processed through our state-of-the-art rolling mills equipped with advanced process control systems for precise temperature and deformation control.

Quality Standards & Certifications

GB Q690 steel manufactured by MetalZenith complies with GB/T 1591-2018 standard and equivalent international specifications including EN 10025-6 S690QL and ASTM A514. Our quality management system is certified to ISO 9001:2015, and we maintain additional certifications including ISO 14001 for environmental management and OHSAS 18001 for occupational health and safety. Each production batch undergoes comprehensive testing including chemical analysis by optical emission spectroscopy, mechanical property verification, ultrasonic testing for internal soundness, and dimensional inspection.

Welding & Fabrication Guidelines

GB Q690 steel exhibits excellent weldability when proper procedures are followed. Preheating to 100-150°C is recommended for sections thicker than 25mm. Low hydrogen welding consumables should be used with interpass temperatures maintained below 250°C. Post-weld heat treatment may be beneficial for stress relief in critical applications. The steel can be readily formed, machined, and fabricated using conventional methods, though higher cutting forces may be required due to its high strength level.