Influence of Sizing and Cooling Process on Properties of N80-1 Seamless Casing Using Steel 40Mn2V and the Process Parameter Control

摘要

Influence of process parameters such as deformation strain and temperature in sizing, and pipe cooling rate on strength, impact toughness and microstructure in steel 40Mn2V was investigated, by hot simulation test, tensile test, impact test and microstructure observation test. The quantitative relationship between strength values and process parameters was analyzed using software Matlab, and the formulas with higher accuracy were established. It is indicated that strength, impact toughness and microstructure are mainly influenced by sizing deformation temperature and pipe cooling rate. Bainite transformation, the main cause of bad impact toughness occurs when pipe cooling rate reaches or exceeds a critical value. To satisfy the property requirements of N80-1 casing when steel 40Mn2V is used, a suitable sizing temperature shall be controlled in the range of 695～870°C when pipe cooling rate is at or below 0.6°C/s, and in the range of 695～820°C when pipe cooling rate is above 0.6°C/s but not exceed 1.1°C/s.