摘要
一根直径为165.1mm的油田钻铤在使用时发生外螺纹断裂。对断裂螺纹的宏观形貌和金相组织进行了观察,并进行了力学性能实验以及化学成分分析和电子显微分析,对弯曲强度比和临界钻压进行了计算。结果表明,材料的化学成分、金相组织、力学性能全部达到标准要求。断口的宏观及微观分析表明,该钻铤的断裂性质是疲劳断裂。由于钻柱实际钻压大于弯曲的临界压力,使钻铤发生严重的一次弯曲,且钻铤与钻头尺寸不匹配以及钻井转速偏大,加速了疲劳裂纹的产生与扩展,最终导致钻铤断裂。提出通过增大钻铤外径、适当降低钻压和转速,同时注意对钻铤进行下井前的检测,可以预防钻铤疲劳失效。
The external screw fractured while a drill collar with the diameter of 165. lmm was drilling. Macro appearance and metallurgical structure were observed, and chemical composition analysis and electron microanalysis were carried out. Then the bending strength ratio and critical drilling pressure were calculated. The results showed that the chemical composition, metallurgical structure and mechanical properties were all consistent with the criterion. Macro and micro analysis of the fracture surface showed that the fracture of this drill collar was fatigue facture. As the actual drilling pressure is higher than the critical drilling pressure, the drill collar bent seriously. In addition, the size of the drill collar didn＇t match that of the drill head, and the drilling speed was excessively large, which promoted the initiation and expansion of fatigue cracks. As a result, the drill collar cracked. It is proposed that the external diameter of the drill collar should be increased, the drilling pressure as well as the rotational speed should be reduced, and the drill collars should be checked before working. All these measures can prevent fatigue failure.
出处
《失效分析与预防》
2008年第2期53-57,共5页
Failure Analysis and Prevention
关键词
钻铤
弯曲
疲劳断裂
drill collar
bending
fatigue fracture
