Reasons for unqualified low temperature impact properties of Q345E steel

During low temperature impact testing of a batch of Q345E steel, it was found that its low temperature impact performance did not meet the standard requirements. The causes of unqualified impact properties were analyzed by means of scanning electron microscope analysis, inclusion evaluation, metallographic examination and grain size grading. The results show that the sulfide in steel concentrated at the center, and the presence of inclusions led to the destruction of the continuity of the matrix. When subjected to impact forces, the effective stress bearing area and impact absorbing area of the steel became smaller, where cracks initiated and rapidly expand. The large grain size of steel reduced the bonding force between metals, ultimately leading to unqualified impact performance of the steel.