Influence of Rolling Direction on Performance of New 125KSI High-grade Steel Oil Casing
The tensile test,impact test and fracture toughness test at room temperature were used to test the strength,plasticity,impact toughness and fracture toughness of new 125KSI high-grade oil casing for ultra-deep wells along the tie direction and perpendicular to the tie direction.Using OM,SEM and EDS technology,the microstructure,grain aspect ratio and inclusion distribution were analyzed,and the influence of microstructure characteristics on the different properties of the oil casing was discussed.The results show that the microstructure of the tubing and casing is composed of lath-like tempered martensite and fine Al2O3-MnS mixed inclusions uniformly dispersed,with a grain size of 8.5.After rolling,the grain aspect ratio along the rolling direction increases,which leads to the increase of strength,the decrease of plasticity and the decrease of impact toughness paralleling to the rolling direction.The inclusion distribution along the rolling direction of the pipeline is more concentrated,which can lead to the decrease of the critical distance and the fracture toughness of the crack propagation direction perpendicular to the rolling direction.
rolling directionoil casinginclusionsmechanical propertiesfracture toughness
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