Micro non-metallic inclusion removal from molten steel with gas bubbles generated by the nitrogen absorbing and releasing method

The effects of vacuum processing time, nitrogen pressure and gas types on the total oxygen and micro non-metallic inclusions in molten steel were investigated to further improve the technology of micro non-metallic inclusion removal from molten steel with gas bubbles generated by the nitrogen absorbing and releasing method. It is found that in the vacuum treatment process, non-metallic inclusions can act as heterogeneous nucleation sites for the evolution of supersaturated nitrogen from molten steel to form bubbles on their surface, the total oxygen decreases, and these micro non-metallic inclusions are effectively removed by the nitrogen absorbing and releasing technology. The longer the vacuum processing time, the lower the content of total oxygen and amount of micro non-metallic inclusions in steel will be, and the removal rate of total oxygen reaches to 81.6% after the steel is vacuum treated 30 min, with the lowest total oxygen content about 7 ×10^-6 in steel.