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在未控轧控冷的轧制条件下,Q345E钢材终轧温度较高,铌推迟形变奥氏体再结晶的作用不明显。虽然铌/钒复合微合金化钢晶粒有一定程度的细化,由于微合金元素的沉淀强化及热轧态组织中贝氏体的出现,导致含铌微合金化钢低温韧性不能满足使用要求。通过对Q345E钢化学成分进行控制,结合控轧控冷技术,并采取合理的热处理工艺,使Q345E钢在保证高强度的基础上,-40℃低温冲击韧性得到明显提高。
Under the condition of uncontrolled rolling and controlled cold rolling, the finish rolling temperature of Q345E steel is higher, and the effect of delayed niobium deformation austenite recrystallization is not obvious. Although the niobium / vanadium composite microalloyed steel grains are refined to some extent, the low temperature toughness of niobium-containing microalloyed steel can not meet the requirements due to the precipitation strengthening of microalloying elements and the occurrence of bainite in the hot-rolled microstructure . By controlling the chemical composition of Q345E steel, combined with controlled rolling and controlled cooling technology, and taking reasonable heat treatment process, the Q345E steel obviously improves the low temperature impact toughness at -40 ℃ on the basis of ensuring high strength.