800MPa级水电钢表面裂纹原因分析及防止措施

Cause Analysis and Preventive Measures of Surface Crack of 800MPa Grade Hydropower Steel

通过采用金相显微镜、SEM等方法,分析了800CF钢的表面裂纹,认为铸坯表面冷却不均匀,反复相变过程中在奥氏体晶界上析出的AlN及Nb、V的碳氮化物导致了裂纹的产生,同时析出物扩大了钢的塑性低谷区宽度,增加了钢的热脆性,在矫直力等外力的作用下产生裂纹或使已经产生的裂纹扩展。通过采取一系列相应的控制措施,使800CF钢的表面裂纹发生率由30%降低至0.4%。

In this paper,the surface cracks of 800 CF steel are analyzed by means of metallographic microscope and SEM.It is considered that the uneven cooling of the billet surface,Al N and Nb,V carbonitride precipitated on the austenite grain boundary during the repeated phase transformation process lead to the cracks.At the same time,the precipitates enlarge the width of the plastic trough,increase the hot brittleness of the steel,and produce under the action of external forces such as straightening force A crack or propagation of a crack that has been produced.Through a series of corresponding control measures,the surface crack rate of 800 CF steel is reduced from 30%to 0.4%.