Q345B钢铸坯断裂原因分析与预防措施

对Q345B钢连铸坯的断口形貌进行了宏观分析，结合光学显微组织的观察与分析，研究了连铸坯断裂的原因。结果表明：Q345B钢连铸坯内部存在中间裂纹，冷却过程中在热应力、相变应力及铸坯自重共同作用下进一步扩展，导致铸坯断裂。通过加强设备的维护与检修，优化扇形段二冷制度， 低过热度浇铸和稳定铸坯拉速等工艺措施预防铸坯断裂。

Cracking Analysis of Q345B Continuous Casting Slab and Precaution Measures

The cause for the fracture of continuous casting slab was studied combing with the observation of optical microstructure.The results showed that the intermediate cracks were inside the slab,which would expand in the cooling process by heat stress,phase transformation stress and self-gravity,and the slab cracked at last.In order to prevent the cracks,measure like enhancing examination and repairing of the equipment,optimizing second rolling system,stabilizing stretching speed and low overheating degree of molten steel,etc should be taken.