锰硅铁合金炉外精炼的基础研究
发布时间：2018-11-22 10:32
【摘要】：我国现有的锰硅铁合金产品存在磷、铝、钛和氧杂质含量偏高等质量问题,已不能满足部分品种钢和新钢种开发的技术要求。通过还原脱磷、吹氮脱铝脱钛等工艺对锰硅铁合金进行炉外精炼,可降低其磷、铝和钛等杂质含量。本课题主要针对锰硅铁合金炉外精炼过程中遇到的基础问题进行研究。首先,系统整理了锰基熔体热力学数据,将标准相互作用系数模型(UIPM)应用于Mn-Fe-Si-C-Ca-P熔体。模型能够计算锰基熔体中锰、硅、铁、碳、钙和磷的活度,碳和钙的溶解度,以及钙和磷的平衡等,还有助于理解锰铁合金和锰硅铁合金的生产过程。测定了Mn-Si-Fe三元熔体中氧的溶解度。用小样电解提取夹杂物的检测结果表明,高硅锰硅铁合金的夹杂物多为石英,普硅锰硅铁合金中的夹杂物多为石英和锰铁硅酸盐。根据理论分析,锰硅铁合金产品中的氧几乎全部以氧化物夹杂的形式存在,其总量可占锰硅铁合金质量的0.075-0.253%,主要来源于外来夹杂物。通过适当延长铁水包内镇静时间和向熔体内部吹氩等手段降低氧化夹杂物含量,理论上可将锰硅铁合金中的氧降低至50ppm以下。采用气体—金属熔体平衡法,测定了氮在Mn-Si-Fe-(C饱和)熔体中的溶解度和熔体中氮化铝和氮化钛的浓度积。氮的溶解度与氮分压的关系符合西华特定律,且其值大小随温度的降低和硅含量的增加而降低；在Mn60Si30Fe熔体中,氮化硅是饱和的。浓度积[%AI][%N]和[%Ti][%oN]值,以及三相平衡点处(熔体与氮气和氮化铝或氮化钛三相平衡)的铝或钛含量,均随温度的降低和硅含量的升高而降低。采用吹氮脱铝脱钛工艺,理论上可将Mn60Si30FeC饱和熔体中的铝和钛分别降低至0.002%和0.011%,基本能够满足90级硬线钢的生产工艺要求。无论是氩气还是空气气氛下,均可用CaO-CaF2渣对锰硅铁合金熔体进行界面还原脱磷,由合金熔体中的硅控制渣金界面处的氧势,可以满足还原脱磷的要求。还原脱磷率随合金中硅含量的增加和温度的降低而增加,CaO-CaF2渣对硅含量大于20%的锰硅铁合金才有明显脱磷效果。锰硅铁合金的还原脱磷有回磷现象产生,在生产实践中,选择合适的除渣时间是还原脱磷工艺的关键。渣中含Al_2O_3和Na2O组分不利于锰硅铁合金熔体的还原脱磷,石墨坩埚不宜用于还原脱磷。采用旋转柱体法测量了含SiC和Si_3N_4颗粒的CaO-MgO-Al_2O_3-SiO_2熔体的粘度。无论是否含SiC或Si_3N_4颗粒,熔体粘度与温度的关系总是符合Arrhenius定律。固-液两相混合体系的粘度活化能取决于液相,而相对粘度几乎不受温度的影响。粘度和相对粘度随转速的降低和SiC(或S毛N4)体积分数的升高而升高。固体颗粒的体积分数相同时,熔体相对粘度受液态渣组分的影响。当液态渣CaO与SiO_2含量的比值或MgO与Al_2O_3含量的比值较大时,相对粘度较低。
[Abstract]:The existing Mn-Si-Fe alloy products in China have high quality problems such as high content of phosphorus, aluminum, titanium and oxygen impurity, which can not meet the technical requirements of some kinds of steels and new steels. By reducing and dephosphorizing, blowing nitrogen to dealuminate and detitanium, and so on, Mn-Si-Fe alloy can be refined out of furnace, and the impurity contents such as phosphorus, aluminum and titanium can be reduced. In this paper, the basic problems in the refining process of mn-Si-Fe alloy are studied. Firstly, the thermodynamic data of manganese based melts are systematically processed, and the standard interaction coefficient model (UIPM) is applied to Mn-Fe-Si-C-Ca-P melts. The model can calculate the activities of manganese, silicon, iron, carbon, calcium and phosphorus, the solubility of carbon and calcium, and the balance of calcium and phosphorus in manganese based melts. It is also helpful to understand the production process of ferromanganese and ferromanganese alloys. The oxygen solubility in Mn-Si-Fe ternary melt was determined. The results showed that the inclusions of high silicomanganese ferrosilicon alloy were mostly quartz, and the inclusions in common silicomanganese ferrosilicon alloy were mostly quartz and ferromanganese silicate. According to the theoretical analysis, the oxygen in Mn-Si-Fe alloy almost exists in the form of oxide inclusions, the total amount of which can account for 0.075-0.253% of the Mn-Si-Fe alloy mass, which mainly comes from the foreign inclusions. By properly prolonging the calming time in the ladle and blowing argon into the melt to reduce the content of oxidized inclusions, the oxygen content in the Mn-Si-Fe alloy can be reduced to below 50ppm in theory. The solubility of nitrogen in Mn-Si-Fe- (C saturated) melt and the concentration product of aluminum nitride and titanium nitride in melt were determined by gas-metal melt equilibrium method. The relationship between the solubility of nitrogen and the partial pressure of nitrogen obeys the law of Sivalt, and its value decreases with the decrease of temperature and the increase of silicon content. In the melt of Mn60Si30Fe, silicon nitride is saturated. The concentration product [% AI] [% N] and [% Ti] [% oN], as well as the Al or Ti contents at the three-phase equilibrium point (melt equilibrium with nitrogen and aluminum nitride or titanium nitride) decreased with the decrease of temperature and the increase of silicon content. The aluminum and titanium in the saturated melt of Mn60Si30FeC can be reduced to 0.002% and 0.011% respectively by the technology of denitrification by blowing nitrogen, which can basically meet the requirements of the production process of the 90 grade hard wire steel. CaO-CaF2 slag can be used to dephosphorize Mn-Si-Fe alloy melt interfacial dephosphorization in argon or air atmosphere. The oxygen potential at the interface of slag and gold can be controlled by silicon in alloy melt, which can meet the requirement of reductive dephosphorization. The reduction and dephosphorization rate increased with the increase of silicon content and the decrease of temperature. The dephosphorization effect of CaO-CaF2 slag was obvious only when the silicon content was more than 20%. The dephosphorization of Mn-Si-Fe alloy has the phenomenon of phosphorus recovery. In the production practice, the key to dephosphorization is to select the proper time of slag removal. The composition of Al_2O_3 and Na2O in slag is unfavorable to the reduction and dephosphorization of Mn-Si-Fe alloy melt, and the graphite crucible is not suitable for reductive dephosphorization. The viscosity of CaO-MgO-Al_2O_3-SiO_2 melt containing SiC and Si_3N_4 particles was measured by rotating cylinder method. The relationship between melt viscosity and temperature is always in accordance with Arrhenius's law whether or not it contains SiC or Si_3N_4 particles. The viscosity activation energy of solid-liquid two-phase mixing system depends on the liquid phase, but the relative viscosity is almost unaffected by temperature. The viscosity and relative viscosity increase with the decrease of rotational speed and the increase of volume fraction of SiC (or S wool N _ 4). When the volume fraction of solid particles is the same, the relative viscosity of melt is affected by the composition of liquid slag. When the ratio of CaO to SiO_2 or MgO to Al_2O_3 is high, the relative viscosity is lower.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF64
本文编号：2349052
[Abstract]:The existing Mn-Si-Fe alloy products in China have high quality problems such as high content of phosphorus, aluminum, titanium and oxygen impurity, which can not meet the technical requirements of some kinds of steels and new steels. By reducing and dephosphorizing, blowing nitrogen to dealuminate and detitanium, and so on, Mn-Si-Fe alloy can be refined out of furnace, and the impurity contents such as phosphorus, aluminum and titanium can be reduced. In this paper, the basic problems in the refining process of mn-Si-Fe alloy are studied. Firstly, the thermodynamic data of manganese based melts are systematically processed, and the standard interaction coefficient model (UIPM) is applied to Mn-Fe-Si-C-Ca-P melts. The model can calculate the activities of manganese, silicon, iron, carbon, calcium and phosphorus, the solubility of carbon and calcium, and the balance of calcium and phosphorus in manganese based melts. It is also helpful to understand the production process of ferromanganese and ferromanganese alloys. The oxygen solubility in Mn-Si-Fe ternary melt was determined. The results showed that the inclusions of high silicomanganese ferrosilicon alloy were mostly quartz, and the inclusions in common silicomanganese ferrosilicon alloy were mostly quartz and ferromanganese silicate. According to the theoretical analysis, the oxygen in Mn-Si-Fe alloy almost exists in the form of oxide inclusions, the total amount of which can account for 0.075-0.253% of the Mn-Si-Fe alloy mass, which mainly comes from the foreign inclusions. By properly prolonging the calming time in the ladle and blowing argon into the melt to reduce the content of oxidized inclusions, the oxygen content in the Mn-Si-Fe alloy can be reduced to below 50ppm in theory. The solubility of nitrogen in Mn-Si-Fe- (C saturated) melt and the concentration product of aluminum nitride and titanium nitride in melt were determined by gas-metal melt equilibrium method. The relationship between the solubility of nitrogen and the partial pressure of nitrogen obeys the law of Sivalt, and its value decreases with the decrease of temperature and the increase of silicon content. In the melt of Mn60Si30Fe, silicon nitride is saturated. The concentration product [% AI] [% N] and [% Ti] [% oN], as well as the Al or Ti contents at the three-phase equilibrium point (melt equilibrium with nitrogen and aluminum nitride or titanium nitride) decreased with the decrease of temperature and the increase of silicon content. The aluminum and titanium in the saturated melt of Mn60Si30FeC can be reduced to 0.002% and 0.011% respectively by the technology of denitrification by blowing nitrogen, which can basically meet the requirements of the production process of the 90 grade hard wire steel. CaO-CaF2 slag can be used to dephosphorize Mn-Si-Fe alloy melt interfacial dephosphorization in argon or air atmosphere. The oxygen potential at the interface of slag and gold can be controlled by silicon in alloy melt, which can meet the requirement of reductive dephosphorization. The reduction and dephosphorization rate increased with the increase of silicon content and the decrease of temperature. The dephosphorization effect of CaO-CaF2 slag was obvious only when the silicon content was more than 20%. The dephosphorization of Mn-Si-Fe alloy has the phenomenon of phosphorus recovery. In the production practice, the key to dephosphorization is to select the proper time of slag removal. The composition of Al_2O_3 and Na2O in slag is unfavorable to the reduction and dephosphorization of Mn-Si-Fe alloy melt, and the graphite crucible is not suitable for reductive dephosphorization. The viscosity of CaO-MgO-Al_2O_3-SiO_2 melt containing SiC and Si_3N_4 particles was measured by rotating cylinder method. The relationship between melt viscosity and temperature is always in accordance with Arrhenius's law whether or not it contains SiC or Si_3N_4 particles. The viscosity activation energy of solid-liquid two-phase mixing system depends on the liquid phase, but the relative viscosity is almost unaffected by temperature. The viscosity and relative viscosity increase with the decrease of rotational speed and the increase of volume fraction of SiC (or S wool N _ 4). When the volume fraction of solid particles is the same, the relative viscosity of melt is affected by the composition of liquid slag. When the ratio of CaO to SiO_2 or MgO to Al_2O_3 is high, the relative viscosity is lower.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF64
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