Effects of Isothermal Temperature on Microstructure and Properties for N80 Oil Pipe Steel

Abstract

Some key temperature parameters in the process of controlled rolling and controlled cooling of N80 grade oil casing steel were simulated by heat treatment method, and the effects of different isothermal temperatures on the microstructure and mechanical properties of N80 grade oil casing steel were studied. The results show that when the isothermal temperature increases from 500 °C to 550 °C, the influence of different microstructure volume and grain size is not obvious; when the temperature reaches 600 °C, the ferrite grain coarsens obviously, the volume fraction of ferrite increases obviously, and the volume fraction of pearlite and bainite decreases obviously. In addition, when the isothermal temperature increases from 500 °C to 550 °C, the yield strength and tensile strength of the test steel increase slightly, and the plastic toughness increases obviously; but when the temperature increases to 600 °C, the yield strength and tensile strength of the test steel decrease obviously, and the plastic toughness continues to increase. The optimum isothermal treatment temperature of test steel is 550 °C.

Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration

“…Deeper oil wells mean increased temperature and pressure, leading to a more adverse operating environment for oil well pipes, resulting in the need for steel with higher safety and reliability standards [1][2][3]. The appropriate hot working parameters can benefit steel by achieving a uniform and stable microstructure and good strength, greatly influencing the quality of final products in industrial production [4][5][6][7][8][9]. To simulate the hot deformation process, a thermal simulation experiment can be conducted.…”