某石油钻具公司在钻杆焊区超声波探伤工序中发现，一接头在其倒角台肩面存在横向裂纹。通过宏观观察、金相检验、化学成分分析和能谱分析等方法，对钻杆接头倒角台肩面横向裂纹产生的原因进行了分析。结果表明：接头材料成分不均匀，原材料局部区域存在严重的元素偏析、疏松等冶金缺陷，破坏了基体的连续性；在后续的接头加工工序中，冶金缺陷进一步扩展，最终产生裂纹。最后提出了相关建议以避免此类缺陷造成的损失。

During the ultrasonic flaw detection process of the welding area of drill pipes in an oil drilling company, transversal cracks were found on the chamfer shoulder surface of a drill pipe. Through the macroscopic observation, metallographic examination, chemical composition analysis and energy spectrum analysis, the causes of transverse cracks on the chamfer shoulder surface of the drill pipe joint were analyzed. The results show that:the compositions of the joint material were not uniform, and serious metallurgical defects such as element segregation and looseness existed in the local region of the raw material, which destroyed the continuity of the matrix; in the subsequent manufacturing process, the metallurgical defects further extended, and finally led to the cracks. Related suggestions were put forward in order to avoid the loss caused by this kind of defects.