某批使用后的钻杆接头在进行无损探伤时发现裂纹和刺漏。通过宏观观察、磁粉探伤分析、化学成分分析、力学性能测试、金相检验、断口分析等方法对接头出现裂纹和刺漏的原因进行了分析。结果表明：钻井时由于钻杆接头上扣扭矩不足，造成主台肩面接触压力较小，内外螺纹配合松散产生动态载荷，螺纹牙底应力分布发生变化，局部应力集中加剧，造成其疲劳强度下降并在螺纹牙底形成疲劳裂纹源，在拉伸载荷作用下裂纹进一步扩展并穿透到接头螺纹内壁，导致内部高压泥浆液从副台肩和贯穿裂纹流入螺纹通道，并由失去密封性的主台肩面冲出并冲刷腐蚀，最终导致接头出现刺漏失效。

Some cracks and punctures were found out when a patch of used drill pipe joints were detected with nondestructive testing method. By means of macroscopic observation, magnetic particle inspection, chemical composition analysis, mechanical property test, metallographic examination and fracture analysis, the causes of crack and leakage of the joints were analyzed. The results show that during drilling, due to the insufficient upper buckle torque of the drill pipe joints, the contact pressure of the main shoulder surface was small, the internal and external threads were loose to produce dynamic load, the stress distribution of the threads bottom changed, the local stress concentration intensified, the fatigue strength decreased, the fatigue crack source formed at the thread bottom, and the crack further expanded and penetrated under the tensile load. The inner wall of the joint thread caused the internal high-pressure mud liquid to flow into the thread channel from the auxiliary shoulder and through cracks, and the main shoulder surface which lost the sealing property rushed out and washed out and corrodes, finally leading to the joint leakage failure.