表面脱碳对S135钻杆服役性能的影响

Effect of surface decarburization on S135 drill pipe's service property

针对表面脱碳对S135钻杆的显微组织、拉伸性能及疲劳寿命的影响进行了研究。结果表明,表面脱碳层会导致钻杆材料硬度大幅度下降,但对钻杆整体拉伸性能的影响不明显。随着脱碳层深度的增加,疲劳裂纹萌生时间逐渐缩短,当脱碳层深度达到一定深度后,疲劳裂纹萌生时间将大幅度缩短。表面脱碳层的存在会促进钻杆表面腐蚀坑的形成,加速服役过程中疲劳裂纹的萌生,降低钻杆服役寿命。为了控制表面脱碳对钻杆服役寿命的不利影响,建议严格控制表面脱碳层的深度。

Effect of surface decarburization on S135 drill pipe＇s microstructure,tensile property and fatigue life was investigated. The results show that surface decarburized layer leads to great decrease of the material hardness,while its effect on tensile performance is not significant.With the increase of decarburized layer＇s depth,fatigue crack＇s initiation duration gradually decreases. When the decarburized layer＇s depth is up to certain depth,fatigue crack＇s initiation life will decrease greatly. Surface decarburized layer promotes corrosion pit＇s formation on drill pipe＇s surface,accelerates fatigue crack＇s initiation,and reduces drill pipe＇s service life. In order to control the adverse effect of surface decarburization,decarburized layer＇s depth should be strictly controlled.