Microstructure and Properties of Q690D High Strength Low Alloy Steel

摘要

As one of the core equipment components of oil and gas drilling rig, derrick is also the main heavy-duty component. Working environment of derrick is quite bad, the material for which should have not only high strength, but also good plasticity, toughness and weldability. In this paper, the chemical composition, microstructure, tensile properties, impact properties and hardness of three typical Q690D high strength low alloy steel manufactured from different methods were studied. The application feasibility of Q690 for drilling derrick manufacture was analyzed. The experimental results show that the carbon equivalent, tensile properties and impact absorption energy of Q690D steel with different thickness obtained by TMCP and Q-T process were obviously higher than the requirement of corresponding standard. TMCP Q690D steel had better toughness, lower carbon content and carbon equivalent, and its micro-structure was granular bainite. Carbon content of Q-T Q690D steel plate was relatively higher than that of TMCP Q690D, and the toughness was slightly lower than that of TMCP Q690D. The microstructure Q-T Q690D was tempered sorbite, and there was certain zonal segregation in center part. The thickness of steel plate used in derrick was usually less than 40 mm, whose manufacturing technology of Q690D was mature. There is broad application prospect in the field of drilling equipment. The application of Q69GD for drilling equipment not only improve the strength grade of equipment materials, but also help to optimize the design of components and ensure service safety.