Study On Mechanical Properties And Corrosion Resistance Of X52 And X60 Pipeline Steel

The oil and gas development environment is getting worse and worse,and we are increasingly demanding the performance of pipeline steel.There is an urgent need to develop pipeline steels for corrosion-resistant oil and gas transportation.In this paper,the forming process,microstructure and corrosion resistance of X52 and X60 pipeline steels were studied.On this basis,a rolling test was carried out in the laboratory,and the microstructure and mechanical properties of the rolled steel sheet were tested.Subsequently,the corrosion performance of pipeline steel in hydrogen sulfide environment was studied.The main work and research results of the paper are as follows:1.Through the laboratory hot rolling and mechanical properties,the microstructure performance test determines the optimal process parameters of hot rolling;heating temperature 1200°C,two-stage rolling,final rolling temperature 880 ±15 ?,final cooling temperature 580 ± 15 ?.X52,X60 pipeline steel with good comprehensive mechanical properties.The microstructure is mainly ferrite and fine pearlite.2.The formation mechanism and influencing factors of HIC and SCC were studied.On this basis,anti-HIC and SCC experiments were carried out on hydrogen sulfide X52 and X60 pipeline steels in accordance with the requirements of NACE Standard TM0284-2011 and NACE Standard TM0177-2005 standards.Anti-HIC test results: After the sample was immersed and etched in a saturated hydrogen sulfide solution for 96 hours,no hydrogen bubbling was observed,and no crack was observed after inspection under a microscope.The crack sensitivity rate,crack length ratio and crack thickness ratio are both zero.SCC test results: The load applied to the sample was 85% of the yield strength,and the sample did not rupture after 720 hours of testing,and magnified 10 times under the microscope,and no hydrogen induced crack was observed in the working portion..The factors such as the type of structure and inclusions of the experimental steel were studied,and the methods to improve the performance of HIC were proposed.The results show that the acicular ferrite with fine and dense grains and uniform microstructure has high density dislocations and pinning dislocation precipitates,which effectively prevents the crack from expanding and thus obtains better HIC resistance.Reducing the content of S element and controlling the shape of inclusions can improve the HIC resistance of X52 and X60 pipeline steels...