X95鋼級(jí)鉆桿管體外表面裂紋形成原因分析
Investigation on Elements Responsible for Development of External Surface Cracks of Drill Pipe Body in Steel X95
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摘要: 一批鋼級(jí)為X95的鉆桿,在進(jìn)行鉆桿接頭摩擦對(duì)焊和鉆桿管體內(nèi)表面涂層涂覆處理后,探傷時(shí)發(fā)現(xiàn)部分鉆桿管體存在不同程度的縱向裂紋。通過(guò)金相、掃描和能譜分析的手段,對(duì)裂紋的形貌和形成原因進(jìn)行分析,并結(jié)合生產(chǎn)工藝過(guò)程,對(duì)產(chǎn)生裂紋的原因進(jìn)行追溯。結(jié)果表明:鉆桿管端磁粉探傷時(shí)與電極接觸,管體局部粘附了低熔點(diǎn)電極材料,造成了重金屬污染,在后續(xù)的加工過(guò)程中,管體再次受熱,粘附其上的重金屬元素向管體金屬沿著晶界擴(kuò)散,從而導(dǎo)致了裂紋的形成。Abstract: Longitudinal cracks with different severity are found via non-destructive flaw detection in some drill pipe bodies from an X95 lot as having undergone joint friction welding and internal surface coating. The morphology of and causes for the said cracks are analyzed by means of such methods as metallography,SEM and EDS. Furthermore,causes for the cracks are traced based on the manufacturing process. As a result,it is identified that the said cracks are caused due to such facts that some low melting point electrode material sticks to the external surface of the pipe body which results in certain heavy metal pollution,when the pipe body contacts the electrode during the pipe-end magnetic particle examination operation,and that in the processing operations as follow,the pipe is reheated,and consequently,the heavy metal elements spread along the grain boundary,which eventually leads to the development of the cracks.
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