F65锻造方坯和轮毂超声波探伤缺陷分析

利用超声波检测、低倍检验、金相显微镜、拉伸试验机及扫描电镜对锻造厂的F65锻造方坯和轮毂锻件的裂纹成因进行宏观及显微组织分析，为深海采油高压传输管法兰的缺陷特征的研究提供可行的方法。结果表明：裂纹是组织残余应力所致，裂纹成因与材料冶金缺陷及氢致裂纹无关，裂纹主要沿条带组织中的贝氏体呈穿晶扩展，与粗大不均匀的铁素体与贝氏体交替分布的带状显微组织有关。锻件的组织应力与锻坯对角线锻造残余剪切应力叠加为裂纹提供了外在条件，其显微组织粗大不均匀是产生裂纹的内在原因。

Defect analysis of F65 forging billet and hub by ultrasonic flaw detection

The macroscopical and microscopic structures on F65 forging billet and hub forging were analyzed by means of ultrasonic testing, microstructure inspection, metallographic microscope, tensile testing machine and scanning electron microscope to discuss the causes of cracking, which provided a feasible method for the research of defect characteristics of high pressure transmission pipe flange in deep sea oil production. The results showed that the cracking was caused by the residual stress of the structure. The cause of the crack was not related to the metallurgical defects and hydrogen induced cracks of the material. The cracks were mainly propagated along the bainite in the strip structure, which was related to the strip microstructure with alternating distribution of coarse and uneven ferrite and bainite. The superposition of the structural stress of forgings and the residual shear stress of diagonal forging provided the external conditions for the cracks. The internal cause of the cracks was the uneven microstructure.