Study On Strength And Toughness Of Wire-line Coring Drilling Pipes

Along with the extensive application of diamond wire-line coring drilling technology in many industry department such as geology, oil & natural gas and etc, the maximum drilling depth gets deeper, and the old drill stems or drill stem joints, which measure up to geology standard DZ60 and material is 45MnMoB, could not to meet the needs. The 42CrMo steel, which is used as deep-well drill stem joints of oil drilling in depth of 1200~2000m, could increase the maximum drilling depth of wire-line coring geological drilling technology. Thus, it is the main purpose to achieve the drill stems and drill stem joints which satisfy wire-line coring drilling. Failure analysis on the early cracked drill stems and drill stem joints of which material is 45MnMoB, find the reasons. As the materials of drill stem joints, 42CrMo in place of 45MnMoB, have been modified treatment, mechanical property test, metallographic analysis, electronic scanning analysis and fracture analysis. Summarizing the optimum modified treatment technology of 42CrMo, and contrasting to 45MnMoB, there are several conclusions as follow:It found the cracked areas of drill stem joints are in the threaded portions after failure analysis on fracture drill stem joints. With metallographic analysis, electronic scanning analysis and fracture analysis, the main reason is found that the bad modified treatment cause early fracture of the drill stem joints.Through survey, the heat treatment facility is out-of-use for drill stem joints is found, so design a practical heat treatment furnace for drill stem joints. It could be used for heat treatment and other parts'treatment, such as sintering of expanded pipes.Through analyses components of 45MnMoB and 42CrMo, it is advisable to use 42CrMo as the material of drill stem joints. study on the modified treatment of 42CrMo, and finally worked out the heat treatment technology: quenching is oil, quenching temperature is 850℃(30min), tempering temperature is 550℃(45min). The joints have tempered sorbite under this heat treatment technology, with better synthetically mechanical property, can meet the desire of DZ90, and is used for wire-line coring drilling in depth of 1500~2000m, possessing the practical application value.