Effecting Factors Study On Strength And Toughness Of N80HFW Casing

In recent years, with the exploration and development of the western and offshore oilfield and the implementation of the stimulation measures, and bad service environment of casing gradually, oil casing demand structure changes obviously, not only the increase in quantity of using greatly, also the improve in the properties required gradually, such as high strength and high toughness oil casing, resistance to high temperature and sulfur casing, etc. The High-frequency resistance welding (HFW) casing has developed rapidly with the advantage of high production efficiency, low cost, high precision in size and shape.This paper mainly study factors on strength and toughness of N80grade high frequency welding casing. First sums up the problems in the process of casing service based on the research situation of the domestic and the abroad, and points out that the weld seam of high frequency welding casing is the weak link of HFW casing. Secondly conduct material performance test and the full scale test with different manufacturer N80HFW casing aimed at HFW casing strength and toughness, and analysis the test data.By comparing and analysis of the results of the test, it can be conclude that the properties of the strip, the base metal of HFW casing, is crucial to the strength and toughness of HFW casing. The chemical composition of the strip used for welding determines the HFW casing, and the casing microstructure combined with the chemical composition of the strip effect of the mechanical properties of casing HFW. Knowing from the results of the test that the HFW casing made of the strip by cold forming and heat treatment on HFW seam, which is the heat mechanical rolled steel with the carbon steel manganese or low alloy high strength steel, and with the fined and Tempered Sorbite, possesses outstanding properties. Compared with seamless casing, that HFW casing not only in the mechanical properties of materials, including tensile strength, yield strength and impact toughness is better, also in the full scale test properties, including the anti-galling, anti-hydrostatic pressure bursting, the anti-collapse strength, and anti-tensile failure.