联邦德国曼内斯曼5inG105钻杆接头失效分析

Failure Analysis of Mannesman G105 Tool Joints

联邦德国曼内斯曼5inG105钻杆接头,在使用过程中因螺纹表面摩擦发热形成脆性的二次淬火马氏体层。裂纹首先在该层产生。这些钻杆接头因热处理工艺不当而具有回火脆性,以致接头材料抗裂纹扩展能力降低,二次淬火层产生的裂纹乃迅速扩展,最终引致钻杆接头的刺穿。

While the 5 in.G105 tool joints made by Manuesman are in the course of operation brittle martensitic layer of secondary hardening occurs on the thread flanks due to frictional heat. And incipient crack occurs on the martensitic layer. As there is temper brittleness present in these tool joints due to improper heat-treatment, the material possesses less resistance to crack extension. So the incipient crack extends rapidly and results in piercing through the tool joint at last.