【作者】 幸伟；

【导师】 倪红卫；

【作者基本信息】 武汉科技大学 ， 钢铁冶金， 2009， 博士

【摘要】 在炼钢生产中,氧及其在钢中的存在形式对钢的性能有很大的影响。随着社会的进步和科技的发展,对钢的性能要求日益提高,现代炼钢对脱氧工艺提出了新的要求。如何降低钢中的氧含量,提高钢的洁净度,越来越为冶金工作者关注。因此,长期以来人们在不断地改进脱氧方法,探索新的脱氧工艺。传统的脱氧方法主要还是使用脱氧剂直接脱氧。这种脱氧法的缺点是,脱氧产物残留在钢液中造成了对钢液的污染。而钢液中的夹杂物,尤其是脱氧生成的氧化物夹杂直接影响到钢材的质量。尽管采取了多种工艺手段去除夹杂物,仍无法彻底避免脱氧产物对钢液的污染。因此,如何减少脱氧对钢液污染的脱氧方法成为炼钢脱氧工艺的发展方向之一。氢气具有较强的脱氧能力。而且生成的脱氧产物为H2O,不会残留在钢中形成氧化物夹杂。将氢气用于钢液的脱氧,可以避免脱氧产物对钢材质量的不利影响。因此,开发用氢气的脱氧工艺,对提高钢的洁净度具有重要意义。然而,在氢气用于钢液脱氧的脱氧效果,脱氧机理及动力学规律等方面还需要系统的研究。本文首先对氢气和天然气的脱氧能力进行热力学计算。同时,对其脱氧机理及影响脱氧效果的因素进行了探讨。在本计算条件下,氢脱氧反应以氢气泡中的氢分子与钢液中的氧之间的反应为主。天然气脱氧过程中,CH4发生分解产生C和H2,C和H2均会与钢中的氧反应使氧含量降低,同时C会溶解于钢液中使碳含量增大。在热力学计算的基础上,进行了钢液吹H2、CH4的脱氧效果及动力学规律的实验研究。考察了吹气量、气相组成及吹气管孔径对脱氧速率的影响。实验结果表明,钢液用H2脱氧可以得到较低氧含量。同时,H2可以减小了钢中表面活性元素[O]对钢液脱氮的阻碍,在高氧含量条件下,仍会使得钢中[N]含量降低。本实验中,在常压下吹H2脱氧基本满足一级反应规律,反应由[O]在钢液侧边界层的传质控制,脱氧反应总的速率常数约在0.0363～0.0494s^-1之间。通过理论和实验研究,提出了在转炉吹炼结束后,通过透气砖向转炉中通入氢气,对不同碳含量的钢液脱氧生产低碳、高纯净度钢的脱氧工艺。钢液吹CH4脱氧过程中,碳脱氧为脱氧的主要反应,在15min的吹气过程中,脱氧量约为总量的60%以上,氧含量可以降低到较低水平。而且,脱氧以及增碳速度随气相中CH4含量的增大而增大。[%O]=0.01%～0.02%为脱氧和增碳平均速度的转折点,钢中氧含量降低至此值时,往钢液中吹CH4生成的碳主要溶解于钢液中使碳含量增加。综合对CH4脱氧的研究,提出了在UHP电弧炉吹氧助熔后,通过喷枪或透气砖向钢液中通入天然气,生产中高碳、高纯净度、低氮钢的脱氧工艺。为将氢脱氧工艺应用于实际生产,针对吹氢脱氧后钢液氢含量增加的问题。在实验室条件下进行吹氩脱氢的动力学实验研究。结果表明,脱氢的反应由氢原子[H]穿过钢液侧液相边界层向液-气表面的传质所控制。总的反应速度常数约在0.0022～0.0052s^-1之间。加强搅拌,增大液-气反应面积可提高吹氩脱氢速度。进行了不同初始氧含量的氢脱氧后钢液加铝脱氧的实验,探讨氢脱氧对钢液洁净度的影响。通过光学显微镜观察金相试样上的夹杂物,进行不同初始氧含量加铝脱氧后钢中氧化物夹杂数量和尺寸关系的研究。结果表明,钢中夹杂物颗粒大小、数量受钢中氧含量与脱氧合金的浓度支配。将氢气用于钢液的初脱氧来降低钢中的氧含量,可以减小脱氧合金加入量降低过饱和度而减小生成氧化物夹杂的数量和尺寸,提高钢的洁净度。最后,提出在RH精炼过程中进行吹氢脱氧,并对其进行可行性及精炼效果分析。RH吹氢精炼过程的数学模型研究表明,吹氢可以有效脱除钢中溶解的氧,随着吹氢精炼时间的延长,氧含量可以降低到接近产品最终要求。RH吹氢精炼过程,脱碳速度要快于常规的吹Ar真空精炼。同时,可以将氮含量降低到较低水平。可以用于高纯净度、超低碳,低氮钢的冶炼。更多还原

【Abstract】 In steel-making process, the properties of steel products are greatly effected by the oxygen and it’s form in the steel. With the progressing of society and developing of science and technology, demands for the quality of steel have been increased. New requirements are put forward on deoxidation process. How to decreased the oxygen content and improve the degree of cleanness of steel have attracted more and more attention. For these reasons, deoxidation process was constantly improved and explored for a long time.Generally, the main deoxidation method of steel melts is performed by adding deoxidizers such as Al and ferrosilicon. In this process, deoxidation product remained in steel melt and effected the properties of steel directly. It is well known that many efforts have been made to remove the deoxidation products from molten steel. But the pollution could not be avoided yet. Therefore, reducing the pollution of deoxidation has become a development tendency of deoxidation process.Hydrogen has strong deoxidizing capability. The deoxidation product （H2O） is easily removed from the melt and no non-metallic inclusions are generated. The bad effect of remained inclusions in liquid steels on the properties of steel should be avoided by deoxidation using hydrogen. Therefore, it is great significant to develop the deoxidation by hydrogen for cleanness improvement of steel. However, the deoxidation effect, mechanism and kinetics law by hydrogen need to be studied more systematically.In this subject, the thermodynamic calculations of deoxidizing capabilities of hydrogen and nature gas were carried out respectively. The mechanism and influence factors of deoxidation were discussed. On the conditions of calculations in this subject, the oxygen in the molten steel mainly reacted with hydrogen molecule in the hydrogen bubble in the deoxidation process. During the deoxidation by nature gas, carbon and hydrogen were decomposed from natural gas. Oxygen content was decrease by reaction with carbon and hydrogen. At the same time, the carbon content was increased for carbon solution.Based on the thermodynamic calculation, the experiment of deoxidation effects and kinetics law by hydrogen and methane were studied by measuring the influence of gas flow rate, orifice diameter of submerged lance and gas compound in laboratory scale experiment. Lower oxygen content can be obtained by hydrogen deoxidation. In addition, the retarding for nitrogen desorption by surface-active elements such as oxygen was minished by hydrogen blowing. The nitrogen content was still decreased at high oxygen content. Hydrogen deoxidation obeyed first-order kinetics and reaction is mainly controlled by the mass transfer of oxygen in the liquid boundary layers. The value of total reaction rate constant was between 0.0363～0.0494s^-1 under the present condition. Based on theoretical analysis and experiments, deoxidation by hydrogen in the end of converter blowing for various carbon content steel was presented, which can be used in low carbon, high cleanness steel production.In the deoxidation process by methane, oxygen removed by carbon was the main deoxidation reaction. It is about 60 percent of whole removal amount of oxygen during gas blowing for 15min. Lower oxygen content can be obtained. Furthermore, the rate deoxidation and carburization increased by increasing the content of methane in the gas phase. The value of critical oxygen content below which the carbon decomposed from methane was mainly dissolved in the melt for carburization is between 0.01～0.02%. According to the character of deoxidation by methane. deoxidation by nature gas after oxygen blowing in UHP electric arc furnace melting was presented, which can be used in medium and high carbon, high cleanness, low nitrogen steel production.In order to apply deoxidation by hydrogen in the practical production, the kinetics of hydrogen desorption from steel melt by blowing argon gas has been studied in laboratory experiment for hydrogen content increasing after hydrogen blowing. The result showed that the rate of hydrogen desorption was controlled by mass transfer of hydrogen atoms in liquid phase. The value of total reaction rate constant was between 0.0022～0.0052s^-1 under the present condition. It was deduced that the rate of hydrogen desorption could be increased by strengthening stirring and increasing the area of the reaction surface.Relationship between the size distribution and number of inclusions with varying initial oxygen content as a function of added aluminum was studied for the improvement in cleanness of the steel by hydrogen deoxidation, the inclusions in steel samples were observed by optical microscope in this subject. The result showed that the size distribution and number of inclusion after deoxidation with alumina were dominated by the content of oxygen and deoxidizing alloy , and decreased by decreasing deoxidizing alloy amount and supersaturation degree for hydrogen deoxidation.Lastly, hydrogen gas injection method in the RH degasser was developed. Refining effect and feasibility were analyzed for the process. The mathematical model for hydrogen deoxidation in the RH degasser was developed. The analysis of the process by the model clarified that the dissolved oxygen could be removed efficiently by hydrogen gas injection in RH degasser. The oxygen content in steel could be decreased to final demand by increasing the process time. During the hydrogen injection, the rate of decarburization and nitrogen removal from liquid steel were increased efficiently. Hydrogen gas injection method in the RH degasser can be used for high cleanness, ultra low carbon nitrogen steel production.更多还原