摘要
随着社会的进步和科技的发展，人们对钢铁材料中的有害元素氮、氧含量的要求越来越高，而传统的钢液精炼方法已不能满足这一要求，这就需要冶金科技工作者在原有的精炼基础上提出新的钢液脱氮、脱氧方法。
钢液脱氮一直是冶金界的一大难点。一个奇特的冶金现象引起了我们的注意；暴露在非分子态(离子态或原子态)气氛下的钢液具有明显的超常规脱氮倾向。在实验室规模的直流电弧炉内通过中空电极向钢液吹氩，钢液中的氮可以脱到较低的水平。这个实验结果也被钢厂15吨电炉中空电极吹氩的工业试验所证实。用电子束炉重熔钢和合金时脱氮效果非常明显，而在普通真空电弧炉内熔炼的合金中氮含量则变化不大。这些试验结果说明钢液中的氮在非分子态气氛下的反应和平衡具有与分子态气氛条件下完全不同的规律，这些规律至今尚未被人们认识清楚。因此，有必要研究在等离子体下钢液脱氮的行为，从而为钢液脱氮开辟一条新的途径。
本研究针对这一现象，提出在直流辉光等离子体下进行钢液脱氮的研究。这样一方面真空本身可以把氮脱除，另一方面利用辉光等离子体可强化脱氮，而直流辉光等离子体有利于研究辉光等离子体脱氮的机理。为此，我们研究了如下关键性问题。
根据直流辉光等离子体的放电特性，设计了脉冲电路控制熔体作为一极的直流辉光等离子体，并在低温熔体锡液和高温熔体钢液上进行了实验。实验证明利用脉冲控制电路可以克服熔体作为直流辉光等离子体一极易引起电流波动这一难点，为以后进行这一领域的研究提供了可靠的电路保证。
从理论上对直流辉光等离子体进行了解析，为实验装置的设计和实验结果的分析提供理论依据。
在低温条件下研究了直流辉光等离子体脱除熔体锡中硫的效果，结果表明：直流辉光等离子体对锡液中硫的脱除效果要比在常态下的好；非反应性气体氩直流辉光等离子体在高硫条件下对锡液中的硫有一定的脱除效果，而在低硫条件下没有去除作用；反应性气体氢直流辉光等离子体对锡液的脱硫效果是非常明显的，而4000Pa的氢直流辉光等离子体脱硫的效果明显好于400Pa的；氩氢混合气体直流辉光等离子体的脱硫效果介于这二者之间，但其脱硫效果优于对应的氢分压为400Pa的氢直流辉光等离子体；在极性相反(锡液为正极)时，氩直流辉光等离子体没有脱硫效果，而氢直流辉光等离子体有一定的脱除能力。根据直流
辉光等离子体的理论对实验结果进行了机理分析和解释。
在此基础上，在铝丝炉上进行了直流辉光等离子体钢液脱氮的实验，结果表
明:在压力为400OPa条件下，直流辉光等离子体对钢液脱氮效果要比真空脱氮
的好。氢直流辉光等离子体脱氮的效果最明显，可把钢液中的氮降到loppm左
右，氢氢混合直流辉光等离子体次之，氢直流辉光等离子体最差。而在真空下钢
液中的氮仅脱到25ppm左右。利用等离子体的理论对直流辉光等离子体脱氮的
原理进行了阐述，并从热力学上对氢直流辉光等离子体钢液脱氮和脱氧的原理进
行了理论上的分析和讨论。
在真空感应炉上进行了钢液脱氮的放大实验。先对由炉衬材料产生的氧而影
响真空钢液脱氮的实验现象进行了研究，结果表明炉衬材料产生的氧降低了真空
钢液脱氮的速度。在这种条件下，钢液脱氮处于一级反应和二级反应的边缘区域。
在与真空钢液脱氮的压力和温度相同的条件下进行的非反应性氨和反应性氢直
流辉光等离子体钢液脱氮的实验结果表明:在这种条件下氢等离子体脱氮和氢等
离子体脱氮效果显著，都可把钢液中的氮脱到gppm，基本处在同一水平级。通
过对它们的脱氮过程进行动力学分析得出:氢等离子体钢液脱氮是界面化学反应
控制，而氢等离子体钢液脱氮既不是一级反应控制，也不是典型的二级反应控制，
但限制环节倾向于界面化学反应为主。
在实验的基础上，对直流辉光等离子体脱除熔体杂质的机理进行了分析并建
立了动力学模型。
对于钢液脱氧，近年来在浓差电池短路脱氧的基础上发展了脱氧体法，尽管
该方法存在无污染、脱氧速度快等优点，但存在成本高、固体电解质大型化等缺
点。为了避免这些缺点，提出了用熔渣代替固体电解质，在渣金间外加电场来强
化脱氧，这样就解决了上述问题，同时具有无需还原剂、无氧化错管炸裂、熔渣
可起到防止熔体二次氧化的作用，设备简单、成本低、可连续作业等优点。因此，
这是一种很有希望的无污染脱氧方法。为此，进行了下面的实验研究。
选择氟铝酸钠十氧化铝渣外加电场进行了铜液脱氧的研究，实验结果表明铜
液脱氧的速度随着外加电压的增加而明显加快，但是终氧含量没有明显的差别。
当使用氧化钠+氧化硅渣进行实验时，终氧含量随电压的增加没有明显的变化。
在铜液脱氧实验的基础上选择CaO十A12咙十510:熔渣外加电场进行了钢液脱
氧的实验，结果表明钢液中氧含量到达soppm左右后再很难进一步脱除。这可
能和渣中氧离子的迁移数小以及熔渣的电化学性质等因素有关。
根据渣金间外加电场熔体脱氧的机理建立了模型并利用模型计算的数据和
实验的结果进行了对比，两者基本上相吻合。
研究表明，在直流辉光等离子体下强化钢液脱氮，可?
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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