钢液中废钢熔化行为的热模拟试验

 废钢熔化过程是控制转炉炼钢过程温度轨迹和废钢比以及电弧炉炼钢能耗和生产率的限制因素。为研究废钢在钢液中的熔化机理,考虑了废钢熔化过程中的传热传质过程,并基于废钢熔化理论分析模型,在实验室中进行了废钢熔化的热模拟试验。研究结果表明,当钢棒浸泡在熔池中较短时间时,钢棒外层形成凝固层。由于激冷效应,在凝固层与钢棒之间形成气隙;在钢棒浸泡过程中,钢棒的组织发生变化,由珠光体和铁素体转变为奥氏体。水淬后,渗碳层中生成针状马氏体,钢棒内层形成板条马氏体。当钢棒在熔池中浸泡时间过长时,钢棒外层形成高温铁素体和液相。     

电弧炉炉底吹气搅拌冷模拟研究

针对25t电弧炉底吹气搅拌工艺，通过冷模拟分别研究了搅拌功率对缩短钢液混匀时间，加快废钢熔化和增强渣一钢界面传质的影响，并得出了相应的规律。研究结果为实际工业性生产提供了理论依据。     

保护气氛下电渣重熔过程中界面脱硫传质动力学

电渣重熔过程中渣金反应温度高,接触面积大,具有良好的脱硫传质条件.然而,渣金界面处存在着传质边界层,边界层的厚度会影响界面脱硫传质速率,这对研究界面脱硫传质具有重要的意义.本文基于菲克第二定律、渗透理论和薄膜理论,建立保护气氛条件下电渣重熔过程渣-金界面脱硫传质方程,研究温度对渣-金间脱硫传质速率的影响规律.研究结果表明:随着温度的升高,渣-金界面处硫的浓度减小,界面脱硫传质速率增大;渣-金界面硫扩散的传质边界层厚度不随温度发生变化.     

帘线钢中钛夹杂形成的热力学分析

对帘线钢中TiN夹杂的形成热力学进行了计算,通过理论计算表明,在帘线钢凝固过程后期,固液界面的TiN平衡浓度积较低,易形成钛夹杂.相对碳含量较低的帘线钢而言,碳含量较高的帘线钢在凝固后期由于固液界面的温度较低,导致TiN平衡浓度积也较低,更易于形成钛夹杂.根据理论分析结果,采取了相应的技术措施,使与钛夹杂相关的帘线钢合格率得到明显提高.     

铁液中Al2O3纳米颗粒溶解和熔化的热力学研究

与块体材料相比,纳米材料尺寸小、界面能大,导致其溶解和熔化过程的热力学不同于块体材料.从理论上推导了Al2O3纳米颗粒在铁液中的元素平衡溶度积以及熔化温度与颗粒尺寸之间的关系,结果表明,随颗粒尺寸减小,平衡溶度积逐渐增加,熔化温度逐渐下降,而且粒径越小,平衡溶度积和熔化温度的变化率越大.经计算,1873K铁液中Al2O...     

废钢比对转炉钢液过氧化的影响及配料调优

转炉终点钢液过氧化不仅会造成合金收得率降低，冶炼成本增加，还会导致脱氧产物增多，钢液洁净度变差。因此，避免转炉终点钢液过氧化一直是工艺控制的重点。针对国内某特钢厂100 t转炉终点钢液过氧化严重的问题，本文通过数据统计发现，该厂平均废钢比高达26%，平均终点C含量仅有0.055%，平均终点温度为1 605℃。在未考虑炉内热平衡的前提下，采取高废钢配料导致了炉内热量不足，从而被迫采取补吹升温，引发终点碳、温度命中率低以及钢液过氧化现象。因此，本文基于该厂的原料条件，从优化炉料结构的维度出发，建立了最大废钢比计算模型，综合考虑原料条件来配加废钢，减少了需要补吹升温的炉次。模型应用后，转炉终点温度平均提高10℃，终点碳含量平均提高0.036%，钢液自由氧含量平均下降206.3×10^-6，降本提质效果显著。     

铁液中Al_2O_3纳米颗粒溶解和熔化的热力学研究

与块体材料相比,纳米材料尺寸小、界面能大,导致其溶解和熔化过程的热力学不同于块体材料.从理论上推导了Al2O3纳米颗粒在铁液中的元素平衡溶度积以及熔化温度与颗粒尺寸之间的关系,结果表明,随颗粒尺寸减小,平衡溶度积逐渐增加,熔化温度逐渐下降,而且粒径越小,平衡溶度积和熔化温度的变化率越大.经计算,1873K铁液中Al2O3的质量分数为0.01%时,半径为0.1nm的Al2O3颗粒比块体Al2O3的平衡溶度积增加了11.71%;半径为1nm的Al2O3颗粒在空气和铁液中的熔化温度分别为1849K和1267K,比块体Al2O3的熔化温度分别下降了454K和1036K.     

连铸结晶器内钢液流动、凝固和夹杂物的分布

 建立并求解动量、热量和质量传输耦合模型,研究了连铸结晶器内钢液流动、传热、凝固、溶质输送和夹杂碰撞长大行为。数值结果表明,受钢液流动的影响,在连铸机内钢液温度、碳浓度和夹杂物的空间分布与钢水流动特征相似,也可分为上下两个循环区。但是其分布具有各自的特点。在涡心处,钢液温度较低,碳浓度较高,夹杂物体积浓度和数量密度较低。在弯月面处,钢液温度较低,碳浓度较高,夹杂物的体积浓度和数量密度较低。在结晶器出口处的凝固坯壳内,夹杂物的浓度和数量密度分布极不均匀,存在阶跃现象,这与冲击点处凝固坯壳的重熔有关。     

大型电弧炉炼钢用氧的模拟实验及其工业应用

根据相似原理，利用1：10比例的有机玻璃模型研究了不同吹氧参数时的熔池混匀时间、传质系数、渣－钢液乳化时间和废钢熔化时间等问题。此外，还测定了氧枪的射流流场。根据实验结果制定的电弧炉提高用氧量工艺制度，在生产中取得了良好效果。     

钢液真空处理挥发脱砷

钢液真空处理时可以实现挥发脱砷，脱砷过程可分为砷在钢液内部传质、砷在钢液表面蒸发、砷在气相中传质三个环节。加强钢液内部砷的传质、增大钢液－气相接触界面及提高钢液真空处理温度都可提高挥发脱砷的速度。     

Steel scrap melting behavior based on linear dissipative thermodynamics

In order to reveal the mechanism of heat and mass transfer in the melting process of steel scrap, linear dissipative thermodynamics was applied to investigate the heat transfer between liquid steel and steel scrap, and the diffusion and mass transfer of carbon and the coupling relationship between them. Combined with the moving boundary layer theory model, the mass conservation equation of carbon at the interface was obtained when the liquid steel temperature is 1773K, the carbon mass fraction of liquid steel is 1.0 mass%, the scrap radius is 0.03m and the initial temperature of scrap is 300K, that is, the scrap melting model based on the theory of linear heat dissipation mechanics. The accuracy of the model is verified by previous experimental results. The scrap melting model based on linear heat dissipation mechanics established can predict the changes of carbon content, carbon activity and interface temperature with time in the scrap melting process, and provide theoretical guidance for practical industrial production.     

铁碳熔池中废钢熔化行为的研究进展

在钢铁冶金过程中,逐步减少铁矿石比例、增加废钢比例,实现钢铁循环,已成为世界钢铁行业追求的目标.废钢的熔化行为是控制转炉炼钢过程温度轨迹和废钢比以及电弧炉炼钢能耗和产能的关键因素;同时,铁水包中废钢的熔化行为可能影响铁水预处理工艺的顺利进行.研究废钢的熔化行为对提高废钢在转炉、电弧炉和铁水包等设备中的利用率以及对保证钢...     

Study on the melting characteristics of steel scrap in molten steel

Steel scrap is of great benefit for environmental protection. In converter steelmaking, bottom carbon injection was applied to enhance the scrap ratio and in EAF steelmaking, submerged carbon powder injection was used to accelerate the smelting of scrap. In these two cases, carbon powder is directly injected into molten metal to improve the scrap melting with effective carburization capacity and intense stirring effect. In this study, the induction furnace experiments were carried out to study the melting characteristics of steel scrap with different carbon contents and bottom-blowing gas flow rates. The results show that larger carbon content and faster fluid flow can promote scrap melting because the carburizing reaction can be accelerated by larger carbon concentration gradient and the heat transfer can be enhanced by larger stirring intensity. Finally, the convective mass transfer coefficient and heat transfer coefficient between steel bar and molten metal were also calculated.     

废钢熔化的热模试验

 为了解废钢的熔化速度和熔化机理,在250 kg感应炉中进行了热模拟试验。测量熔化速度采用直径为[?20～?50 mm]的Q235圆钢,熔池温度为1 300、1 400和1 600 ℃。根据试棒直径不同确定在熔池中浸泡时间。根据钢棒浸泡前后的质量和尺寸差别,计算出熔池为1 300、1 400和1 600 ℃时,其质量熔化速度分别为1.8～4.0、3.5～6.5和12.6 g/s;径向熔化速度为0.012～0.026、0.035～0.045和0.060 mm/s。熔池液体与试棒之间的对流换热系数在1 400 ℃时为32 931 W/（m2·℃）,1 600 ℃时为32 884 W/（m2·℃）。在温度为1 300 ℃时,碳在液体与试棒之间的对流传质系数为6.3×10－5 m/s,温度为1 400 ℃时为6.4×10－5 m/s。热模拟试验所测得的钢棒熔化速度、液-固相之间的对流换热系数、碳的对流传质系数都与国外冶金工作者的试验结果相近,可以作为炼钢生产中计算废钢熔化的基础数据。     

Cold Model Investigations of Melting of Ice in a Gas-Stirred Vessel

The melting of steel scrap in high temperature liquid iron melt is investigated by conducting cold model experiments of the melting of ice sample of different geometries and sizes in an argon-stirred vessel containing water. The melting process of ice samples is observed using a high-speed camera. Design of experiments is based on similarity criteria. The relationships between non-dimensional groups related to heat transfer (Nu, Re, Pr, and Gr) are derived for different experimental conditions. The results are compared with those reported in the literature. The heat transfer coefficient is estimated as a function of mixing power and is found to be in good agreement with the calculated values obtained by using reported relationships in literature.     

Kinetics of steel melting in carbon-steel alloys

For the melting of scrap metal in baths with a high carbon content, in which the melting temperature lies below the bath temperature, a model is being developed which is based on the coupling of mass and heat transfer. It will be shown that the mass transport determines the melting rate only for very low bath temperatures. Furthermore, it will be discussed how the melting efficiency is influenced by the supplied energy flow and mass transfer in the bath.     

The melting and dissolution of low-carbon steels in iron-carbon melts

Direct experimental proof is presented in the paper for the role played by the mass transfer of carbon in accelerating or facilitating the melting and dissolution of pure iron specimens in iron-carbon melts. It is shown that pure iron may readily melt in iron-carbon melts even under conditions where the temperature of the molten phase is considerably below the melting point of the pure iron or low-carbon specimen. A mathematical interpretation is developed for these experimental results that includes the mass transfer of carbon and the unsteady state heat transfer within a moving boundary system. The results of the analysis were found to agree with the experimental data thus providing a basis for further calculations aimed at predicting the melting of scrap in the basic oxygen furnace. These calculations show that scrap melting, facilitated by carbon diffusion from the melt to the scrap surface, begins very early during the process and that melting is retarded and even terminated during the blow when the bath has insufficient superheat to provide the necessary sensible and latent heat required for melting. It follows therefore that the rate of scrap melting in steelmaking processes is accelerated if the removal of carbon in the bath is retarded or if the temperature of the bath is increased rapidly in order to maintain a high level of superheat during the refining process.     

Kinetics of scrap melting in liquid steel

The melting rate of steel bars with various sizes, shapes, and initial temperatures in a 70 kg liquid steel bath (1650 °C) was measured to investigate the kinetics involved in steel scrap melting. Our measurements revealed that a solidified shell was formed around the original bar immediately after it was immersed into the liquid steel. This shell and an associated interfacial gap generated between it and the original bar were found to be critical to the melting kinetics. We also found that the total melting time decreased linearly with increasing initial bar temperature. The melting process was simulated using a two-dimensional phase-field model that considered heat convection with a constant heat-transfer coefficient. Our simulations were in good agreement with our experiments and showed that the heat conduction associated with the interfacial gap was one of the most important physical aspects controlling the melting of steel scrap.     

超高功率电弧炉炼钢工艺模型

本文以物料平衡、热量平衡和化学平衡为基础，采用理论与经验相结合的模化方法，建立了超高功率电弧炉炼钢工艺模型，即冶金模型和热模型。冶金模型包括：优化配料模型、石灰加入量模型、钢水熔清成分模型、吹氧量模型、钢水终点成分模型和最优补加合金模型。热模型包括：废钢预热温度模型、能量消耗模型、能量损耗计算模型、能量供应计算模型和钢水温度预报模型。冶金模型中，加入了造渣料的计算。热模型中，考虑了废钢预热、氧燃烧