钢包喷粉脱硫过程中钢液内氮行为的研究

对８０吨钢包喷粉脱硫试验数据的统计分析，研究了该过程中钢液内氮含量与钢液化学成分、炉渣性质、钢液温度、喷粉参数等因素的关系。     

氮在CaO—SiO2—AL2O3渣中行为的研究

本文借助于一系列气相——熔渣平衡试验的数据,对 CaO-SiO_2-Al_2O_3渣中氮的行为进行了研究。研究表明、氮在渣中的溶解并不是与自由氧离子作用、而是与渣中 SiO_2、Al_2O_3网络结构作用,形成新的 Si-N 或 Al-N 网络而进入渣中。本文获得了渣中 Si_(0.75)N、AIN 的活度系数经验计算公式和熔渣氮容量的经验计算公式,为选择适宜的合成渣组成进行炉渣脱氮提供了依据。     

冶金炉渣磷酸盐容量指数与碱度的关系

本文总结了磷在炉渣中的存在形式和磷酸盐容量的概念，评价了几种表示炉渣碱度的方法，引入类似于磷酸盐容量的磷酸盐容量指数。在此基础上研究了１３００－１６５０℃时２０３组平衡条件下各种渣系炉渣磷酸盐容量指数ＣＰＩ与光碱度、氧离子摩尔分数、Ｂｅｌｌ比率之间的关系。结果表明：平衡实验条件下炉渣磷酸盐容量指数与炉渣碱度有较好的对应关系，特别是对光学碱度，当Ｆｅ２Ｏ３、ＦｅＯ的光学碱度选用由电负性得出的０．４８     

冶金炉渣水蒸汽溶解度或羟基容量的研究进展

本文总结了水蒸汽熔解度或羟基容量与炉渣组成的关系，分析了水蒸汽在炉渣中存在形态和水蒸汽与炉渣反应机理，介绍了计算水蒸汽溶解于炉渣的溶解热和表观传质系数的方法。     

利用高氮化能力的熔剂精炼钢除氮

利用试验技术通过调整和精确控制１８７３Ｋ时的氧分压Ｐｏ２测定了Ａｌ２Ｏ３－ＣａＯ－ＴｉＯ２和ＣａＦ２－ＴｉＯ２熔剂中氮的溶解度和氮化能力。据试验发现，熔渣和铁水之间的氮分配比以及金属的脱氮度是Ｐｏ２的函数。文章研究了采用含ＴｉＯ２的熔剂从纯铁和铬合金钢中的除氮工艺，即首先把炉渣与金属粉末混合，然后在１８７３Ｋ坩埚中加热熔化，并将熔融金属从１０ｋｇ感应炉出钢至包中。系统中的氧分压可通过精炼剂中铝或钛含量进行调整。试验结果表明Ａｌ２Ｏ３－ＣａＯ－ＴｉＯ２渣可除去低合金钢中氮，脱氮度可超过６０％。文章讨论了生产过程中采用含ＣａＦ２－ＴｉＯ２熔剂的炉渣进行钢包处理有效去除高合金钢中氮的技术参数。     

钢液脱氮用BaO—TiO2基合成渣

以TiO2高炉渣为基料配制的合成渣对钢液脱氮的效果进行了实验室试验研究，结果表明：在Ar气保护下，对低碳铝脱氧钢液脱氮，其脱氮率达60％以上，最低［N］含量约10×10-6。     

冶金炉渣硫化物容量指数与碱度的关系

采用１３００～１６００Ｃ各种渣系的７６组平衡条件下和１２４组准平衡条件下工业实验数据，研究了本文所引入的硫化物容量指数与光学碱度，Ｂｅｌｌ比率，氧离子摩尔分数的关系。结果表明，硫化物容量指数与炉渣各种表达方式的碱度之间有较好对应关系，但在准平衡的工业实验条件下，上述关系相对较离散，因此可认为，硫化物容量指数作为炉渣碱度的一种表示方法的观点似不能适用于所有条件。     

CaO－Al_2O_3－SiO_2渣系氮的溶解热力学

根据炉渣结构的共存理论，推导了ＣａＯ－Ａｌ_２Ｏ_３－ＳｉＯ_２熔渣的作用浓度计算模型。模型计算得出的各组元的作用浓度值与文献报道的活度值非常一致。在此基础上，进一步采用回归分析法找出了ＣａＯ－Ａｌ_２Ｏ_３－ＳｉＯ２渣系中溶解的氮含量以及与此渣系相平衡的钢中氮含量及氮的分配比随渣中各组元作用浓度之间变化的定量关系，理论计算结果与实验值非常符合。     

氮在Ca-SiO_2-Al_2O_3渣中的热力学研究

本文借助于光学碱度概念,对CaO-SiO_2-Al_2O_3熔渣中氮的稳定性进行了研究。结果表明,气相中氮不是与渣中自由氧离子作用,而是与网络结构作用而进入熔渣。根据氮与网络结构SiO_2或Al_2O_3之间的反应。提出了熔渣氮容量的新定义。根据渣中氮的行为,结合一系列的试验结果,得到了1823 K时CaO-SiO_2-Al_2O_3渣的氮容量计算公式IgC_N=-11.721gA-14.26和三元渣系的等氮容量曲线。     

金属液的脱氮

本文综述了金属液熔渣脱氮、真空脱氮和气泡携带法脱氮方法。熔渣脱氮热力学研究主要涉及脱氮反应和熔渣的氮容量。真空度、氩气搅拌和金属液中氧、硫浓度是影响真空脱氮和气泡携地脱氮的主要因素。     

Solubility of nitrogen in CaO-SiO2-CaF2 slag system

Equilibrium experiments between gas and slag were carried out to understand the thermodynamic behaviour of nitrogen in the CaO-SiO₂-CaF₂ slag system at 1600°C. The solubility of nitrogen in this slag system increased as the oxygen potential decreased and as the reaction temperature increased. The values of the nitride capacity have a minimum at about 2.0 slag basicity, having higher values in both more acidic and basic regions. This may be explained by two mechanisms for nitrogen dissolution; incorporated nitride ion and free nitride ion state. In slag with 2.0 basicity or less, MgO content increased the nitride capacity slightly. At higher slag basicity, however, nitride capacity decreased with MgO content. The effects of BaO to substitute CaO on nitride capacity showed similar behaviour as MgO. This complex relationship between basicity of slag and nitride capacity is explained by using optical basicity. It was found that nitride capacity and optical basicity had a close relationship even in the different basic oxide systems.     

Removal of nitrogen from steel using novel fluxes

The solubility of nitrogen and the nitride capacity of CaO-Al₂O₃-TiO₂ and CaO-BaO-Al₂O₃-TiO₂ slags were measured at 1873 K using a gas-slag-metal equilibration technique with carbon-saturated iron and gas mixtures of CO and N₂. The nitride capacity increased with increasing the TiO₂ and BaO content and is significantly higher than the nitride capacity for normal ladle slags. The activity coefficient of TiO₂ in CaO-Al₂O₃-TiO₂ and CaO-BaO-Al₂O₂-TiO₂ systems were measured. This is necessary to know in order to estimate the possible pickup of titanium in the metal when an aluminum-killed steel is treated with these slags. Also, the activity coefficient of Ti in carbon-saturated iron was measured. The kinetics of the nitrogen reaction between slag and metal is influenced by the oxygen potential in the metal and is primarily controlled by liquid-phase mass transfer of nitrogen in the metal. Formerly with the Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University     

Thermodynamics of nitrogen in CaO-SiO2-AI2O3 slags and its reaction with Fe-Csat. melts

The solubility of nitrogen as the nitride ion in CaO-SiO₂-Al₂O₃ slags in equilibrium with N₂-CO gas mixtures and carbon was measured at 1823 K. The nitride capacity (C _N3-) was calculated to compare the nitrogen contents measured under different nitrogen and oxygen potentials.C _N3- decreased with increasing basicity and by replacing SiO₂ with A1₂O₃. The nitrogen partition ratio between carbon saturated iron and the slag was measured in CO gas at one atmosphere at 1823 K. By comparing the partition ratios with the corresponding nitride capacities measured by the gas-slag experiments, it was concluded that the oxygen partial pressure at the slag-metal interface was controlled by the Fe-FeO reaction. A new definition of nitride capacity was proposed based on the reaction between nitrogen and the network former,i.e., SiO₂ or A1₂O₃. This capacity could consistently explain the experimental results. Empirical equations were derived to estimate the activity coefficients of silicon and aluminum nitrides in the slags. On leave of absence from the Research Institute of Mineral Dressing and Metallurgy, Tohoku University, Sendai, Japan.     

Thermodynamics of nitrogen in CaO-SiO2-AI2O3 slags and its reaction with Fe-Csat. melts

The solubility of nitrogen as the nitride ion in CaO-SiO₂-Al₂O₃ slags in equilibrium with N₂-CO gas mixtures and carbon was measured at 1823 K. The nitride capacity (C _N3-) was calculated to compare the nitrogen contents measured under different nitrogen and oxygen potentials.C _N3- decreased with increasing basicity and by replacing SiO₂ with A1₂O₃. The nitrogen partition ratio between carbon saturated iron and the slag was measured in CO gas at one atmosphere at 1823 K. By comparing the partition ratios with the corresponding nitride capacities measured by the gas-slag experiments, it was concluded that the oxygen partial pressure at the slag-metal interface was controlled by the Fe-FeO reaction. A new definition of nitride capacity was proposed based on the reaction between nitrogen and the network former,i.e., SiO₂ or A1₂O₃. This capacity could consistently explain the experimental results. Empirical equations were derived to estimate the activity coefficients of silicon and aluminum nitrides in the slags. On leave of absence from the Research Institute of Mineral Dressing and Metallurgy, Tohoku University, Sendai, Japan.     

A study of nitrogen solubility in Na2O‐B2O3 slag

The nitrogen solubility and nitride capacity of a Na₂O‐B₂O₃ slag system were investigated in a concentration range of Na₂O mass contents up to 40 % at 1373K. The solubility of nitrogen in Na₂O‐B₂O₃ slag was found to be proportional to the oxygen partial pressure to the power of ?3/4, and it was also found to increase with increasing reaction temperature. The nitride capacity of the slag decreased with increasing Na₂O content. From the experimental results it was concluded that nitrogen dissolution into Na₂O‐B₂O₃ slags (Na₂O mass contents < 40 %) occurs by its reaction with both free oxygen ions and with oxygen ions incorporated with the network.     

Nitrogen solution in BaO-B2O3 and CaO-B2O3 slags

The nitrogen solubility and nitride capacity of the BaO-B₂O₃ and CaO-B₂O₃ systems were measured at 1698 and 1773 K, respectively, using a gas-liquid equilibration technique. These systems were chosen because they have wide liquidus regions at the temperature of interest and were expected to show two types of nitride solution behavior. The nitride capacities of both systems showed minimum values with changing composition. This was explained by considering that nitrogen can dissolve into slag as “free nitride” at high basicities and as “nitride incorporated” with the network for acidic slags. The change of the nitride capacity with optical basicity and the activity of the basic component followed the predicted behavior for the proposed solution mechanism. The nitride capacity of the BaO-B₂O₃ system is considerably greater than for the CaO-B₂O₃ system because BaO is a more basic oxide than CaO. The activity of BaO in the BaO-B₂O₃ system was also measured by equilibration with liquid silver, at known oxygen potentials, and the activities show large negative deviations from ideal behavior.     

Chemical behaviour of nitrogen in metallurgical slags

According to previous experimental work, nitride capacity C_N, in opposition to sulfide capacity C_S, decreases with increasing optical basicity of metallurgical slags. This tendency is also confirmed by the contradictory behaviour of the free energy changes of oxide-nitride and oxide-sulfide transformation reactions as a function of basicity. From the present metal-slag equilibrium studies, denitrogenation potentials P_N = %(N)/{%[N] · %[Al]} were obtained characterizing denitrogenation efficacy of slags at given compositions and temperatures. From these potentials, factors were derived which mark the effects of individual slag components. It was found that these factors feature the same basicity dependence as nitride capacities C_N and denitrogenation potentials P_N. The factors are increased, e.g., as less basic oxides are increasingly present in the slag phase in the order BaO → SrO → CaO → MgO.     

Solubility of nitrogen and carbon in CaO-Al2O3 melts in the presence of graphite

CaO-Al₂O₃ slags were melted in graphite crucibles under N₂-CO-Ar gas mixtures at 1600°C. The contents of total nitrogen, cyanide and total carbon of the slags were determined by chemical analyses of quenched samples taken by suction from the melt. The nitrogen is present in the melt as nitride N^3- ion and cyanide CN^-1 ion, and carbon as cyanide and carbide C_2- ion. The equilibrium constants for the respective reactions were evaluated. It is found that the nitride capacity of the melt decreases whereas the cyanide and carbide capacities increase with increasing CaO/Al₂O₃ ratio.