Study on Low Temperature Brittle Fracture Mechanism and Alloying Toughness of Polished Rod
Aiming at the low-temperature fracture of polished rods in the effective oil wells of Dongsheng company of Shengli oilfield,using EDM element analysis,metallographic analysis,Charpy impact test and other methods.The brittle fracture mechanism of polished rods has been studied.The effects of alloy composition and microstructure on the impact toughness of polished rods were analyzed.The results show that the ductile-brittle transition temperature of ordinary smooth sucker rods is between-40℃and-20℃,which is just in the temperature sensitive range under liquid CO2 injection and production conditions,leading to brittle fracture.Through deformation strengthening,adding Ni,Ti,N and other alloy elements to toughen polished rods,the micro morphology of improved polished rods are changed significantly,the ductile-brittle transition temperature is dropped to about-60℃,and the low-temperature impact toughness is significantly improved,which can meet the demand for low-temperature liquid CO2 enhanced oil recovery production.
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