Effect of Heat Treatment on Low Temperature Impact Toughness of GB T1591 Q345D Steel Plate

GB T1591 Q345D steel plate and so on low-alloy high-strength steel is the most widely used engineering structural steel among iron and steel materials. GB T1591 Q345D steel plate is widely used in various sectors of national economic construction, especially in infrastructure construction and basic manufacturing industries, such as construction of oil pipelines, oil platforms, bridges, large buildings, and manufacturing of ships, vehicles, containers and machinery, chemical industry and light industrial equipment.

The main reason for the low impact energy of steel materials at low temperature is that phosphorus is dissolved in ferrite, which decreases the plasticity and toughness of steel at room temperature and increases the brittle transition temperature, leading to brittleness of steel. This brittleness phenomenon is more serious at low temperature. The addition of isoalloying elements in steel greatly strengthens the matrix in the form of solid solution and precipitation, but reduces the plasticity of the steel material, especially the impact toughness at low temperature.

GB T1591 Q345D steel plate has a high requirement for low temperature impact energy. The low temperature impact energy of GB T1591 Q345D steel plate can be significantly increased by 880 Dec and 900Dec normalizing for one hour and 450Dec tempering, which can homogenize and refine the ferrite and pearlite structure.