45MnCrMo钻铤管内壁裂纹成因分析

在生产45MnCrMo钻铤管时,钢管内壁常出现较多裂纹,影响了钢管质量及成材率。通过采用光学显微镜、扫描电镜和能谱仪、热模拟试验机、低倍热酸浸分析测试手段,分析研究了钻铤管内壁缺陷特征和形成原因。结果表明:45MnCrMo钻铤管的内壁缺陷,是由于管坯穿孔过程中,内壁金属与顶头在摩擦和扭转变形等复杂应力作用下产生了较高的温升,从而导致毛管局部区域过热失塑、晶界弱化所形成,与管坯的冶金质量无关。提出了改进钻铤管内壁质量的有效措施。

Genetic Analysis of Inner Surface Cracks of 45MnCrMo Drill Collar Pipe

As a common case that is encountered with when manufacturing the 45MnCrMo drill collar pipe,lots of cracks are developed on the inner surface of the pipe,which negatively affect the pipe quality and the yield. Accordingly,relevant analysis and study are conducted to the pipe to identify the characteristics and formation causes of the said inner surface defect by means of such methods as LM,SEM,EDS,thermal simulator and macroscopic hot acid etching process etc. The results of such tests reveal the true story about formation of the defect. It says that the inner surface cracks of the 45MnCrMo drill collar pipe are developed due to the overheat-caused plasticity reduction and grain boundary weakening in local areas of the pierced shell as induced by higher temperature rise of the metal of the pipe inner surface and the piercing plug,which is jointly caused by such complex stresses as the friction,and the torsional deformation,etc. in the piercing process,and that the crack formation has nothing to do with the metallurgical quality of the blank. As a result,countermeasures are put forward to improve the inner surface quality of the drill collar pipe.