Influence of nitrogen and oxygen contents on the microstructure and performance of HCM2S steel

The influence of nitrogen and oxygen contents on the microstructure and performance of HCM2S steel was studied by the room temperature tensile test of 4-furnace HCM2S steel tubes after being normalized and tempered, microstructure observation, and energy dispersive spectrum analysis. The results show that when the mass fraction of nitrogen is larger than 71 × 10^-6, the depletion of useful boron and the reduction of harden ability will take place, which would affect the microstructure and performance of the steel. The fluctuation of the mass fraction of oxygen in the range of 16 × 10^-6 to 49 × 10^-6 has no influence on the microstructure and performance of HCM2S steel, when the nitrogen content is no more than 71 × 10^-6. Addition of a little titanium will cause the reaction with nitrogen, save the content of useful boron, and obtain the bainite structure and excellent mechanical properties even with higher nitrogen content.