钢液中的氮在非分子态气氛下的行为

An interesting unreported phenomenon has been observed in this investigation: the refining effect of cold plasma on liquid metal. The impurity elements in metal may be removed by distillation and gas evolution process. The purification of metal can be enhanced if ionic gas exists in a reaction chamber of the process. In the above case nitrogen, sulfur and phosphorus as impurities in liquid metal are converted into volatile compounds and distilled off. This refining process could not be done under normal atmosphere. The refining effect of cold plasma has made it possible to develop a new technology, which can be used to produce very clean metal.Cold plasma (non-equilibrium plasma) used in our investigation is obtained by exerting a DC electric field on the space between liquid metal treated and a plate of metal as two electrodes. It is simple and nexpensive for its equipments and controllable for operation.The results of experiments illustrate that after the treatment of the plasma, the contents of nitrogen, sulfur and phosphorus in liquid metal decrease to 8ppm, 1ppm and 10ppm, respectively. While under the same thermodynamic conditions and the normal atmosphere of molecular gas, the removal of the impurities is only slightly conducted.The refining mechanism of the cold plasma may be of two types:The refining ability of chemical reactive elements will be enhanced in the process. For example, the molecules of hydrogen in the gas are ionized when applied a DC pulsed electric field. Thus the different radicals are produced. While the radicals reach the surface of the melt, they react with the impurities to form some volatile compounds, such as NH3, H2S and PH3. Because the compounds are insoluble into the liquid metal, they will be carried off by fluent gas. Finally the impurity elements are removed from metal.The other mechanism is the conversion of the kinetic energy of inert gas ions into the work, which is needed for atoms dissolved in melt escaping from the surface of metal. The cations of inert elements will be accelerated in the sheath near the surface of metal and the collision occurs. The transformation of energy helps the escape of elements in metal from liquid phase to gas phase..The effects of two refining mechanisms are quite different on various metal systems, impurities and their concentrations. Also the efficiency of each refining mechanism is a function of the condition of process, such as temperature and pressure.A new experiment study is planed to carried out under ambient pressure as applying a DC pulsed source with higher voltage and higher frequency. Quantitative analysis of the fluent gas will help us to recognize the products in the process and understand real reaction mechanism. The possibility of removal of other elements will be tested..

实验结果表明气相中的氮在离子或原子状态下与钢液的作用机理和分子氮完全不同。本项目通过施加物理场的方法制造非分子态气氛环境，进行氮的行为规律、氮在金/气二相中的热ρ胶庖约巴训淼难芯浚芯砍晒赏⑿碌母忠和训都际跆峁├砺垡谰莺图际醪问