Simulation Study on Compositions and Process Optimization of V-microalloyed N80-class Seamless Tube

The synthesis effects of different nitrogen(N) contents and thermal processes on the microstructure and mechanical properties of 33Mn2V steel for N80-class seamless tube were investigated using Gleeble simulation technique.The results showed that when the N content in the steel increased from 0.005% to 0.014% or 0.021%,for in-line normalizing process,the strength of steel increased,and in the same time toughness of steel increased greatly.The further research showed that while the reheating temperature decreased,the strength of steel became lower slightly and the toughness of it improved.When the cooling-interrupted temperature of steel changed from 450 ℃ to 700 ℃,the process varied from in-line normalizing to non in-line,which made the strength of steel increased significantly and the toughness decreased evidently.This can be attributed to the dissolution and precipitation behavior of V(CN).The optimization of V(CN) precipitation can be achieved by the enhanced N.