Cold Simulation of Oxygen Transfer Rate in BOF

 By measuring the mass transfer coefficient of between water and oil, the oxygen transfer rate of bath in the BOF smelting process is researched, and the influence of top and bottom blowing gas flow rate on the mechanism of mass transfer between metal and slag is discussed. The results show that when the bottom blowing gas flow rate increases on the conditions of top blowing, the mass transfer rate evidently increases, and the influence ratio of top blowing on the mass transfer is 10 percent of bottom blowing; The relation among top gas flow rate, bottom gas flow rate and lance height are established by the stirring power density. The equation between the mass transfer coefficient between metal and slag is formed, which furnishes reference for optimizing process parameters of BOF. The relation between the emulsification ratio between water and oil and the bottom blowing gas flow rate on the condition of top and bottom blowing is obtained. The result shows that with the increase of the bottom blowing gas flow rate the emulsification ratio increases in linearity, which increases the mass transfer rate of benzoic acid between water and oil.     

大型转炉优化造渣工艺提高脱磷的效果

 针对转炉冶炼存在的转炉前期化渣速度慢,冶炼终点钢水、炉渣氧化性高,终点磷含量控制不稳定等问题,利用炉渣熔化性测定、热力学平衡计算、炉渣矿相分析的方法研究了260 t转炉造渣、供氧工艺。结果表明,转炉初期渣熔化温度为1 330 ℃,不利于转炉前期化渣;终渣熔化温度为1 200 ℃,不利于转炉后期的炉衬维护;终点钢水磷含量与渣钢间磷平衡值差距较大,说明转炉吹炼终点动力学条件不足;炉渣中游离氧化钙含量较高,有部分未熔化的石灰。通过优化转炉渣料加入顺序和数量,强化转炉终点氧枪枪位控制、底吹搅拌等技术措施,可获得较高的转炉终点脱磷率和渣-钢间磷分配比,使终点渣-钢间磷含量更接近平衡;终点炉渣发育良好,游离氧化钙含量适中。     

Research on Top and Bottom Mixed Blowing CO2 in Converter Steelmaking Process

Based on the analysis of reaction mechanism between CO₂ and molten pool elements at the steelmaking temperature, and on the calculation of materials and heat balance during converter steelmaking process with blowing CO₂, a new technology which uses CO₂‐O₂ as top gas and CO₂ as bottom gas in a converter was proposed and experimented in a 30 t converter. It is found that the new technology is feasible absolutely, the amounts of smoke dust and T‐Fe are reduced by 11.15% and 12.98% on average, the contents of nitrogen and phosphorus are decreased by 50% and 23.33% respectively, iron loss of slag is lowered by 3.10% and oxygen consumption is reduced remarkably. This research will provide a new blowing method for BOF steelmaking process, which can save steelmaking energy consumption and reduce smelting cost.     

转炉冶炼轴承钢GCr15的生产工艺研究

分析了转炉冶炼轴承钢的优势,对转炉轴承钢氧含量、钛含量偏高和精炼工艺存在的问题进行了讨论,认为精确控制转炉吹炼终点,实现高碳低氧出钢、控制出钢下渣量成为转炉冶炼轴承钢的重要环节;在精炼方面,应加强钢包顶渣脱氧、保证一定的钢水[ALs]含量和提高氩气搅拌效果.     

Cold model studies of mixing and mass transfer in steelmaking vessels

Abstract

Room temperature model studies using water to simulate 'metal' and paraffin oil (when required) as 'slag' were conducted to study the extent of mixing and the rate of mass transfer between metal and slag in the 130 t basic oxygen furnaces (BOFs) in operation in Tata Steel. Several systems of gas injection including top blowing, combined blowing and exclusive bottom purging were investigated. Similar work was undertaken in a room temperature model of an 80 t energy optimising furnace (EOF), in operation for a brief period earlier in Tata Steel. Details of the optimum blowing conditions, including the number/distribution of bottom tuyeres for the BOFs, are elaborated in the present paper. How mixing/mass transfer in an EOF compares with the BOF case(s) is also highlighted.     

复吹转炉最佳成渣路线的探讨

复吹转炉冶炼过程中不同的成渣路线直接影响着冶炼操作的稳定性、终点的命中率和炉衬的寿命。为此从炉渣碱度和炉渣氧化性两个方面讨论了复吹转炉冶炼低磷铁水和磷含量较高的铁水的成渣路线。结果表明,由于冶炼操作参数的不同,冶炼磷含量较高铁水的炉渣中的∑FeO含量和炉渣碱度比冶炼低磷铁水时高得多,并在此基础上提出了复吹转炉冶炼过程中的最佳成渣路线。     

100t转炉-LF(VD)工艺冶炼轴承钢的氧含量控制

通过铁水预脱硫-100 t顶底复吹转炉-吹Ar-LF(VD)-方坯连铸工艺生产轴承钢的实践,得出冶炼终点钢水碳含量为0.2%~0.6%时,钢水氧含量在50×10^-6到150×10^-6之间;经出钢时脱氧、吹氩、LF(VD)精炼后,中间包钢水中的全氧含量为(14~16)×10^-6,铸坯中的全氧量<12×10^-6。分析表明,加强熔池搅拌,使钢渣充分反应,控制转炉下渣量<5 kg/t钢,加强吹氩搅拌,控制LF顶渣碱度在2.0~2.5之间,(FeO)+(MnO)小于0.5%,可使轴承钢中全氧量进一步降低。     

80t顶底复合吹炼转炉的冶金效果

对比了包头钢铁（集团）公司炼钢厂80t顶底复合吹炼转炉和顶吹氧化转炉的冶金效果,结果表明,底吹气体对钢水的搅拌作远大于顶吹氧化。采用顶底复合吹炼工艺后,不仅钢水成分和温度更均匀,吹炼更平稳,而且钢水终点残余锰点含量提高。由于吹炼时间、氧化消耗量及炉渣中的FeO含量都有所降低,因此金属收得率提高,另外,通过适当提高炉渣碱度,该工艺还可取得较好的脱磷效果。     

RH脱碳过程中极低氧钢水的碳氧反应机理

BOF+LF+RH+CC工艺路线生产IF钢,在RH脱碳前,钢水经脱氧和LF精炼后,钢中自由氧达到极低水平.根据表观脱碳速率常数的不同,这种极低氧钢水的RH脱碳可以划分为四个阶段.与传统三个阶段的RH脱碳不同的是在低速脱碳阶段和快速脱碳阶段存在一个脱碳速率介于两者之间的过渡阶段.在正规溶液模型的基础上,建立了能够准确预报钢液氧含量及顶渣FeO含量的RH脱碳模型.结果表明:在RH吹氧前,极低氧含量的钢液与顶渣之间基本不传氧;吹氧之后,钢液氧含量呈线性增加,当钢液氧势大于顶渣氧势后,钢液向顶渣传氧,渣中FeO含量上升;RH处理结束FeO含量较处理初始有所回升,但是仍处于极低水平,能够有效降低顶渣对钢液的二次氧化.     

氧气顶吹转炉留渣操作研究

介绍了川威集团炼钢厂80t顶底复吹转炉的留渣操作工艺,对留渣操作的条件进行了研究,结合半钢操作的工艺条件,分析了应用转炉项底复吹和溅渣护炉工艺解决留渣操作安全问题的机理。实践证明实施留渣操作对转炉冶炼时的初期化渣和脱磷十分有利,留渣操作可以降低石灰消耗、降低钢铁料消耗、提高炉龄,显著提高经济效益。     

Preliminary Investigation of Mathematical Modeling of Stainless Steelmaking in an AOD Converter: Mathematical Model of the Process

Mathematical modeling of stainless steelmaking in an AOD (argon‐oxygen decarburisation) converter with side and top combined blowing has been preliminarily investigated. The actual situations of the side and top combined blowing AOD process were analysed. A mathematical model for the whole refining process of stainless steel has been proposed and developed. The model is based on the assumption that one part of the oxygen blown through a top lance reacts with CO escaping from the bath, another part of the oxygen oxidizes the elements in the molten steel droplets splashed by the oxygen jet, and the remaining oxygen penetrates and dissolves into the molten steel through the pit stroked by the jet. All the oxygen entering into the bath oxidizes C, Cr, Si, and Mn dissolved in the steel and also the Fe of the steel melt, but the FeO generated is also an oxidant of C, Cr, Si, and Mn in the steel. During the process, all possible oxidation‐reduction reactions occur simultaneously and reach their equilibria, respectively their combined equilibrium, in competition at the liquid/bubble and liquid/slag interfaces. In the simple side blowing after the top blowing operation is finished, the possible reactions take place simultaneously and reach a combined equilibrium in competition at the liquid/bubble interfaces. The overall decarburization rate in the refining process is the sum of the contributions of both the top and side blowing processes. It is also assumed that at high carbon concentrations, the oxidation rates of elements are mainly dependent upon the supplied oxygen rate, and at low carbon contents, the rate of decarburisation is primarily related to the mass transfer of carbon from the molten steel bulk to the interface. It is further assumed that the non‐reacting oxygen blown into the bath does not accumulate in the steel and will escape from the bath and react with CO in the atmosphere above the bath. The study presents calculations of the refining rate and the mass and heat balances of the system for the whole process. Additionally, the influences of the operating factors, including addition of slag materials, scrap, and alloy agents, the non‐isothermal conditions, the changes in the amounts of metal and slag during the whole refining process, and others have all been considered.     

Equilibrium kinetics of manganese-ore carbon-reduction between molten steel and slag

The equilibrium condition between molten steel and slag during manganese-ore carbon-reduction was studied using both resistance furnaces and induction furnaces. The resistance furnace experiment shows that it is difficult to further increase the yield of manganese (maintained at around 37%) without stirring. The bottom blowing and top slag stirring were strengthened in the induction furnace test, where white slag was continuously produced to promote the carbon reduction of manganese dioxide in slag between molten steel and slag. Under these conditions, the yield of manganese between molten steel and slag can reach greater than 90%. The main factors affecting the manganate capacity are the carbon and silicon content in molten steel. The limiting process of manganese mass transfer is mainly the mass transfer of manganese in molten steel. Under carbon reduction in molten steel the limiting factor affecting the mass transfer of manganese is the mass transfer of manganese in slag.     

差流量吹氩模式对150 t钢包混匀与顶渣行为的影响

 针对钢包传统的双孔等流量底吹氩模式在流量较大时造成的流股相互碰撞、搅拌能耗散大、钢包卷渣和钢水二次氧化倾向大的问题,提出一种双孔差流量搅拌模式,并以150 t工业钢包为原型,采用1∶3物理模型研究了两个吹氩孔分布、吹氩流量和渣层厚度对新底吹模式下钢水混匀时间与顶部渣眼面积的影响。结果表明,与传统等流量吹氩模式相比,双孔差流量搅拌钢包混匀时间和渣眼面积普遍有所减小。其中,两个底吹透气砖在包底0.6R(钢包底部半径)处、夹角为180°时,可获得较短的混匀时间和较小的渣眼,且两个渣眼出现在钢包液面两侧,避免了常见的渣层偏聚不均匀现象。研究结果为工业实践中采用新型双孔差流量搅拌模式改善钢包冶金效果、更好地抑制钢水二次氧化提供了依据。     

Simulation of Steel Refining Process in Converter

Steel refining is a complex phenomenon which depends on numerous variables, so, a kinetic approach is necessary for precise understanding of the refining process. In this study, based on a previously proposed model for hot metal dephosphorization, a new simulation model for the steel refining process in BOF is presented. In most cases, steelmaking slag is saturated with dicalcium‐silicate (C₂S) and it is well known that C₂S forms solid solution with tricalcium‐phosphate (C₃P) in a wide composition range and the partition ratio of phosphorus between C₂S and liquid slag is large. On the other hand, C₂S formed around the lime surface is known as a barrier to lime dissolution into liquid slag. In this simulation model not only the effect of solid phase in slag is considered but also the effects of temperature dependence of variables as well as top and bottom blowing and scrap melting are taken into account. The calculation results are compared with industrial data and the good agreement between experimental and simulation results evidence the validity of this kinetic approach to steel refining process in BOF. Moreover, by using this model the influence of various parameters on the reaction efficiency is discussed.     

马钢超低硫钢的生产工艺研究

在马钢生产X70、X80管线钢为平台的超低硫钢生产工艺的基础上,分别对转炉、LF精炼过程钢水硫含量控制进行了分析研究,研究结果表明转炉吹炼过程增硫主要来自于铁水脱硫渣和废钢中带入的硫,LF炉深脱硫主要取决于钢包顶渣的控制和强搅脱硫的搅拌功。通过工艺调整,使生产X70、X80管线钢时LF炉终点w[S]可稳定控制在0.005 0%以下,平均w[S]为0.001 1%。     

超纯轴承钢的精炼工艺

通过控制电炉(供氧强度、渣中氧化铁比例、出钢挡渣率、出钢钢液的氧活度)、钢包炉(精炼渣系、脱氧剂、钢液温度、精炼时间、底吹氩压力、精炼钢包耐火材料的选择、铁合金种类的选择)、真空脱气(真空度、真空时间、底吹氩压力)的工艺参数以及真空后的软吹氩搅拌、并采用IPAS系统和控制钢液浇铸速度,使超纯轴承钢(SFGCr15)的w(S)、w(Ti)、w(O)分别达到0.003%、0.001 2%和0.000 7%以下,钢中非金属夹杂物也处于较好水平,满足了国际顶尖轴承厂家对轴承钢的超纯要求.     

120t BOF-LF-VD-CC流程生产磨球钢B2的工艺实践

磨球钢B2（/%:0.75~0.85C,0.70~0.90Mn,≤0.030P,≤0.030S,0.40~0.60Cr,≤0.20Ni,≤0.20Cu,0.010~0.060Al）的生产工艺流程为120t BOF-LF-VD-180mm×220mm/260mm×300mm坯CC。通过转炉枪位及供氧强度控制、转炉留渣量及底吹流量的优化、转炉全铝一次脱氧;LF精炼渣系精炼渣碱度由3.44提高到4.25、控制VD氩气流量,VD后软吹≥15min;连铸使用整体塞棒包、全保护浇注工艺、钢水10~25℃过热度操作、使用磨球钢专用保护渣和结晶器电磁搅拌320A,4Hz末端300A,10Hz,提高了磨球钢铸坯的内部质量,钢材的各项指标满足标准要求。     

Silicon volatilisation in the form of SiO during slagging by limestone in BOF

In this paper, the silicon volatilisation phenomenon during slagging by limestone in basic oxygen furnace (BOF) and its influencing factors were studied by industrial experiment and thermodynamic calculation. In our estimation, the volatilisation ratio of silicon in this industrial experiment is about 13.01–47.82%. Thermodynamic analysis showed that the silicon volatilisation phenomenon happens after charging limestone directly into BOF because CO₂ from limestone decomposition could massively oxidise the silicon in the hot metal into gaseous SiO in the hot spot zone. The mass of produced SiO increases, then decreases with the increase of the limestone addition and the carbon content of hot metal, and SiO mass is proportional to silicon content of hot metal. Compared with lime slagging, the strong stirring effect of CO₂ from limestone decomposition, massive foaming slag formation, great increment of furnace gas are all favourable to silicon volatilisation.     

济钢25t转炉复吹技术的实践

介绍了顶底复吹技术在济钢25t转炉上的应用。在合理设计底吹流量控制方式的条件下，底吹强化了转炉内钢水的搅。拌，减少了钢水和渣的氧化，与顶吹工艺相比，钢水和锰的收得率分别提高了0．24％和2．5％，钢铁料和石灰消耗分别降低了2．4kg／t和2．0kg／t，年综合经济效益达313万元。     

底吹方式对渣-钢界面影响规律的水模型

 利用水模试验方法模拟底吹方式对转炉吹炼过程中渣-钢界面搅拌与传质效果的影响,研究底吹强度、底吹枪个数等因素对渣-钢界面搅拌与传质的影响规律。试验研究结果表明,由于底吹搅拌作用,使渣-钢间传质速率呈规律性变化。不同底吹枪个数与底吹搅拌强度的组合,存在渣-钢界面传质速率的最大值。单支底吹枪的底吹强度为0.020～0.025 m3/（t·min）时,渣-钢间传质速率最大。