Due to the complexity of operating environment in marine engineering, petrochemical industries and pressure vessels, steel plate are required for ultra-high strength as well as a good low-temperature toughness and performance uniformity. It is widely accepted that alloy elements purifying and controlling, refining the effective grain size, and increasing the number of large-angle grain boundaries are the major methods to improve the toughness. Recently we have found in Drop-weight Impact Test of High Grade Pipeline that the crack of cleavage fracture is closely related to the rotating cube texture {001} <110> intensity. Therefore, the research on hot rolling texture optimization to improve the low temperature toughness of research material has begun to attract attention. Professor Xu Yun-bo and doctoral student Yang Xiao-long carried out a systematical research on X100 pipeline steel toughness at low temperature and relationship between anisotropy and crystallographic texture.
The study found that, in the rolling direction of 45°, the impact specimen brings the most {001} cleavage plane grains, and the least {110} slip plane grains, which means the pipeline steel tends to suffer cleavage fracture in 45° direction, having the lowest impact energy. Through optimizing TMCP process and controlling original texture of austenite type and intensity, followed by controlling cooling regulatory transformation texture type and intensity, we can significantly reduce steel brittleness {001} <110> component strength, and significantly increase toughness of {332} <113>component strength, in order to greatly improve the platform energy and low temperature impact toughness, and its anisotropic behavior. For example, at -60 ℃, the impact energy of X100 steel increased from 60J to more than 180J, with SA larger than 80%. Related papers have already been published in Materials Science and Engineering A, which is an international renowned magazine in material and engineering. The research results provide a new solution to further improve the low temperature toughness of ultra-high strength heavy plate.