| With progressing of society and developing of science and technology, the contents of harmful elements in steel, such as nitrogen and oxygen, are desired to be lower and lower. Traditional refining methods have not been enabled to meet the demand, it requires metallurgists to propose a new denitrogenization technique and a novel deoxidation method.It is difficult to remove nitrogen from steel in metallurgy. A peculiar phenomenon, which is an evident tendency of nitrogen removal in a non-molecule atmosphere, attracted our notice. When argon gas was blown into liquid steel in an experiment-scale DC Arc Furnace through a hollow electrode, nitrogen content in molten steel could be decreased to a lower level. The result was confirmed by the trial of argon blowing through a hollow electrode in a 15-ton arc furnace. The effectiveness of nitrogen removal is obvious when steel or alloy is remelted in an electronic beam furnace, however the nitrogen content in liquid alloy doesn't change when the alloy is remelted in a vacuum arc furnace. The results obtained from these trials demonstrated that the nitrogen behavior in molten steel under the non-molecular atmosphere was different from that under molecular atmosphere. Unfortunately, the pattern of nitrogen removal hasn't distinctly been known. So, it is necessary to investigate nitrogen removal from liquid steel in plasma, thus starting a new way for denitrogenizaion of liquid steel.Based on the fact, the study on nitrogen removal from steel in DC glow plasma was proposed. In the plasma, nitrogen removal may be removed from steel by vacuum, on the other hand, denitrogenation may be intensified by plasma and the mechanism of nitrogen removal may be understanded because DC electric field was used to generate glow plasma. A series of important results have been reached as follows.According to discharging characteristics of DC glow plasma, a pulse controlled circuit was designed to control the circuit of DC glow plasma with melt as a polar and used it to make experiment in molten tin and liquid steel. The results showed that the pulse controlled circuit was feasible to control DC glow plasma with melt as a polar, thus resolving the difficulty of current fluctuation when melt was a polar and providing a reliable circuit for studying on the field in future.The DC glow plasma was theoretically explained and a basis was provided for the experimental design and theoretical analysis.Desulfurization of molten tin in DC glow plasma was examined. The results indicted that the effectiveness of sulfur removal from molten tin in DC glow plasma was better than that in normal state. A certain amount of sulfur could be removed in non-reactive argon gas DC glow plasma when the sulfur content was high, and the desufurizaion did not take place when the sulfur content was low in molten tin. In the reactive hydrogen gas DC glow plasma it had remarkable desufurization effectiveness. The sulfur removal effectiveness of hydrogen DC glow plasma at a pressure of 4000Pa was better than that at a pressure of 400Pa. The desulfurization power of DC glow plasma of argon and hydrogen was between that of hydrogen DC glow plasma and that of argon DC glow plasma, but, better than that of hydrogen DC glow plasma at a hydrogen pressure of 400Pa. While polarity was changed (the melt was anode), the argon DC glow plasma hadn't desulfurzated and the hydrogen DC glow plasma had desulferization power. Based on the theory on DC glow plasma, the experimental results were discussed and the removal of other elements from melt was considered.Further the dinitrogenization of molten steel was investigated in DC glow plasma on a molybdenum wire furnace under the pressure of 4000Pa. The experiment results showed that the denitrogenization effectiveness in DC glow plasma was better than that in vacuum. The denitrogenization effectiveness of hydrogen DC glow plasma was the best in different kinds of DC glow plasmas and could make the nitrogen content of steel decrease to 10 10-4mass% or so, better for argon and hydro...
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