VOD炉冶炼Cr不锈吹氧脱碳浅析

在采用电弧炉＋VOD＋CC生产Cr不锈连铸坯的生产过程中,VOD精炼的控制对整个生产有着至关重要的作用,而控制Cr不锈VOD精炼过程的关键是吹氧脱碳。在吹氧脱碳过程中,脱碳初期及高碳区、低碳区采用不同的吹氧、吹氩流量及真空度控制,可以提高脱碳速度,同时以氧电势分析仪数据为主,以计算吹氧量、真空度变化、废温变化为辅,能更加准确的控制终点碳,从而提高吹氧脱碳效率。     

Numerical Simulation of Fluid Flow in Bath during Combined Top and Bottom Blowing VOD Refining Process of Stainless Steel

The fluid flow in a bath in combined top and bottom blowing vacuum‐oxygen decarburization (VOD) refining process of stainless steel has numerically been simulated. The three‐dimensional mathematical model used is essentially based on that proposed in our previous work for the flow in combined side and top blowing argon‐oxygen decarburization (AOD) process, but considering the influence of reduced ambient pressure. Applying it to the flow in the bath of a 120 t VOD vessel under the refining conditions, the results present that the model can fairly well simulate and estimate the flow phenomena. The flow pattern of molten steel in the bath with the combined blowing is a composite result under the common action of the jets from a three‐hole Laval top lance and gas bottom blowing streams. The jets have a leading role on it; the molten steel in the whole bath is in vigorous stirring and circulatory motion during the blowing process. The streams do not alter the basic features of the gas agitation and liquid flow, but can evidently change the local flow pattern of the liquid and increase its turbulent kinetic energy to a certain extent. The flow field and turbulent kinetic energy distribution in the combined blowing with three tuyeres are more uniform than those in the blowing with double tuyeres. Increasing properly the tuyere eccentricities is of advantage for improving the velocity and turbulent kinetic energy distributions, the stirring and mixing result in the practical VOD refining process.     

单嘴精炼炉真空处理过程气泡行为及冶金效果研究

根据相似理论,以钢厂80 t单嘴精炼炉1:4的水模型模拟了单嘴精炼炉内气泡行为,分析了吹气流量(2～10 L/min)、吹气塞直径(15～30 mm)对气泡行为、混匀时间的影响。水模拟结果表明,随吹气流量增加,混匀时间减少,但吹气流量≥6 L/min,混匀时间没有显著变化;在相同吹气量下,吹气塞直径增加,混匀时间减少。实验研究基础上,在80 t单嘴精炼炉上进行了超低碳钢的生产试验,结果表明单嘴精炼炉在18 min脱碳时间内,钢中碳含量可降到10×10^-6;脱硫剂消耗4 kg/t的情况下,成品钢中S含量为(20～30)×10^-6,脱硫率平均达49%;吹氩强度平均为4 L/(t·min),是相同吨位RH的25%。     

RH生产超低碳钢的脱碳速率及工艺优化

 通过RH超低碳钢脱碳工业试验,对RH精炼过程工艺参数进行全程跟踪。重点对表观脱碳速率常数Kc进行了测定和评价。结果表明,RH脱碳过程分为3个阶段：抽真空阶段、吹氧脱碳阶段和自然脱碳阶段。稳定生产碳含量小于0.002%(质量分数,下同)的超低碳钢的优化工艺参数为：进站碳含量0.05%~0.06%,氧含量0.04%~0.06%;吹氧期的起始真空度12~15kPa,吹氩强度0.015m3·t-1·min-1;自然脱碳时间大于15min,吹氩强度0.015m3·t-1·min-1,终脱氧前的氧含量＜0.035%。     

Mathematical Modelling of Non‐equilibrium Decarburization Process during Vacuum Circulation Refining of Molten Steel: Application of the Model and Results (I) ‐ Decarburization Process and Influences of Some Technological Factors

A novel three‐dimensional mathematical model proposed and developed for the non‐equilibrium decarburization process during the vacuum circulation (RH) refining of molten steel has been applied to the refining process of molten steel in a 90‐t multifunction RH degasser. The decarburization processes of molten steel in the degasser under the conditions of RH and RH‐KTB operations have been modelled and analysed, respectively, using the model. The results demonstrate that the changes in the carbon and oxygen contents of liquid steel with the treatment time during the RH and RH‐KTB refining processes can be precisely modelled and predicted by use of the model. The distribution patterns of the carbon and oxygen concentrations in the steel are governed by the flow characteristics of molten steel in the whole degasser. When the initial carbon concentration in the steel is higher than 400 · 10⁻⁴ mass%, the top oxygen blowing (KTB) operation can supply the oxygen lacking for the decarburization process, and accelerate the carbon removal, thus reaching a specified carbon level in a shorter time. Moreover, a lower oxygen content is attained at the decarburization endpoint. The average contributions at the up‐snorkel zone, the bath bulk and the free surface with the droplets in the vacuum vessel in the refining process are about 11, 46 and 42% of the overall amount of decarburization, respectively. The decarburization roles at the gas bubble‐molten steel interface in the up‐snorkel and the droplets in the vacuum vessel should not be ignored for the RH and RH‐KTB refining processes. For the refining process in the 90‐t RH degasser, a better efficiency of decarburization can be obtained using an argon blow rate of 417 I(STP)/min, and a further increase in the argon blowing rate cannot obviously improve the effectiveness in the RH refining process of molten steel under the conditions of the present work.     

钢包双孔对称交替底吹气混匀行为的物理模拟

混匀是衡量钢包底吹氩精炼冶金效果的重要指标,优化底吹氩工艺来促进混匀是钢包精炼研究的核心内容。首次提出采用双孔对称交替底吹气的方式来增强搅拌、促进混匀,采用几何相似比为1∶4的水模型,模拟现场吹气量为300L/min,对150t钢包交替吹气位置0.1R~0.5R、交替吹气时间0~15s进行研究。结果表明,随着交替吹气时间的增加,混匀时间先增加后减少;随着底吹气孔与钢包中心距离的增大,混匀时间先减少后增加;底吹气孔与钢包中心的距离为0.3R时,混匀时间最短;交替时间为15s时,混匀时间最短,比不交替吹气缩短5.5%。     

Preliminary Investigation of Fluid Mixing Characteristics during Side and Top Combined Blowing AOD Refining Process of Stainless Steel

The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon‐oxygen decarburization) refining process of stainless steel were preliminarily investigated on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model were more reasonably determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics was examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a high mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from the top lance made the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27 degrees between each tuyere, and five side tuyeres with an angular separation of 22.5 or 27 degrees between each tuyere. The relationships of the mixing time with the gas blowing rates of main‐tuyeres and sub‐tuyeres and top lance, the angle between each tuyere, and the tuyere number were evaluated.     

底吹氧气,天然气复吹转炉冶金特点的热模研究

为了开发氧气,天然气作底吹气源,在国内建立顶、底吹氧炼钢法,作者在60 kg热模上进行了50多炉吹炼低碳钢的试验。结果为:喷嘴熔损速度≤1mm/炉,喷嘴畅通,可实现100％的复吹;吹炼特性好,过程平静、无喷溅。试验还比较了顶吹与复吹的脱碳速度变化,观察到复吹前期脱碳速度较大,中期比顶吹略低,变化平稳,持续时间较长。此工艺适合冶炼低碳钢。还对不同底吹氧比对终点氢含量的影响进行了研究,在试验条件下得到的增氢量为0.54 ppm。     

转炉吹炼中低碳锰铁的应用分析

利用本研究得到的Mn-Fe-C、Mn-Si-C熔体的热力学性质与温度之间的关系式,计算了高碳锰铁转炉法吹炼中、低碳锰铁的脱碳保锰转化温度,并分析了硅对吹氧脱碳热力学行为的影响。     

RH MFB精炼过程脱碳数学模型及工艺研究

 为研究RH MFB精炼工艺对脱碳过程的影响，将脱碳机理确定为钢液本体脱碳与CO克服静压力上浮、氩气泡表面脱碳和飞溅液滴脱碳，根据脱碳反应动力学和质量守恒原理建立了RH MFB脱碳数学模型。计算结果表明：降低初始碳含量、增大初始氧含量可使脱碳终点碳含量降低；提高压降速率和吹氩流量、增大浸渍管内径使得脱碳速率增大；在固定氧气流量下，随着吹氧时间的延长，脱碳终点碳含量降低，但脱碳终点氧含量升高。     

Behavior of carbon,oxygen, and sulfur during hydrogen blowing of liquid steel

The decarburization of liquid steel during hydrogen blowing has been studied. The decarburization is caused by the interaction of carbon with oxygen dissolved in the metal. As the melt is blown with hydrogen, the decarburization is enhanced owing to hydrogen bubbles, which increase the effect of mixing of a metal bath and substantially increase the melt-gas phase interface. As a result, the rate and completeness of decarburization increase significantly. It is experimentally shown that hydrogen blowing of a melt substantially decreases the sulfur concentration in the metal because of the interaction of hydrogen with sulfur.     

超纯铁素体不锈钢VOD脱碳模型研究

摘要：为了实现对超纯铁素体不锈钢VOD精炼脱碳过程的动态即时预测及控制,以酒钢宏兴不锈钢分公司100 t VOD炉冶炼超纯铁素体不锈钢的过程为研究对象,从顶吹氧气的分配行为和C Cr的竞争氧化出发,建立基于炉气分析技术的VOD动态脱碳模型,并在Matlab环境下开发相应的应用软件,得到全过程钢液成分、氧气分配比、温度等参数随时间的变化规律,对不同阶段的临界碳浓度给出估计范围。利用VOD出站成分以及精炼过程中CO/CO2的实际变化规律加以检验,与实际值吻合较好,较好地预测了实际变化趋势。     

100 t单咀真空精炼炉底吹位置的优化

结合钢厂100 t单咀真空精炼炉相关参数,运用数值模拟的方法对脱气时单咀炉内的钢液流场进行了仿真计算,分析单咀炉内钢液流动的基本特征,研究了距底部圆心0.1～0.424 m吹气位置对钢液流场、钢液循环流量和混匀时间的影响。结果表明,原吹氩位置(距底部中心0.424 m),大部分氩气没有进入浸渍管,为避免氩气逸出,吹气孔距圆心应≤0.3 m;随吹气位置至圆心距离增大,钢水混匀时间减小,综合考虑钢液脱气效果和浸渍管寿命,最佳吹气位置应为距底部中心0.25～0.3 m处。     

The Effect of Processing Parameters on Ferromanganese Alloy Carbon Content in Mamatwan Ore Reduction

Industrial production of medium carbon ferromanganese is accomplished by decarburization of high carbon ferromanganese in an oxygen blown converter. In this study, the possible in situ refinement of high carbon ferromanganese was tested in carbon deficient mixtures of pre-reduced Mamatwan ore, coal char, and silica flux reacted at furnace temperatures of 1450°–1550°C. The resultant phase chemistry was analyzed and interpreted with the aid of thermochemical calculations. Production of carbon unsaturated ferromanganese alloy in the AlloyStream process is explained with reference to laboratory experimental results.     

RH喷吹参数对循环流量和均混时间影响的物理模拟

以某厂300tRH真空精炼装置为研究原型,建立1∶6.5的水力模型对RH喷吹精炼工艺进行物理模拟。研究了喷吹位置、喷吹气量及驱动气体流量对循环流量和均混时间的影响。结果表明:不同喷吹气量、驱动气体流量条件下,获得大循环流量和短均混时间的最优喷吹位置不同。较小的喷吹气量(2.98~3.53m3/h)或者较小的驱动气体流量(0.93~1.02m3/h)时,宜采用低顶枪枪位(153.8mm)喷吹;喷吹气量大于3.91m3/h或者驱动气体流量大于1.12m3/h时,宜采用真空槽底部喷吹角度120°的侧喷嘴喷吹。顶枪与侧喷嘴复合喷吹有利于提高RH喷吹工艺的适应性及循环效率。     

110t不锈钢钢包炉底吹氩水模拟

依据相似原理建立钢包的物理模拟体系,采用水模型对110t LF钢包底吹氩过程进行研究,分析了吹气量、吹氩位置、钢包覆盖渣和钢包液面高度对钢包混匀的影响,并进行了相应的试验验证。研究结果表明：水模型试验结果和大工业应用具有较好的一致性,验证了水模型的可行性;钢包液面高度越高,混匀时间越长;吹气量越大,混匀时间越短;相同的液面高度和吹气量下,底吹氩最佳位置为0.33r 附近;钢包覆盖渣较黏时会使钢液流动显著减慢,增大吹气量容易产生卷渣现象。     

太钢VOD冶炼超纯铁素体不锈钢的工艺技术进步

阐述了超纯铁素体不锈钢的超低碳氮的特点及其熔体降碳去氮困难的原因,利用真空降碳去氮的理论结合这方面的研究成果分析和讨论了影响VOD脱碳脱氮的影响因素,并利用VOD现场冶炼的具体数据进行了这些因素的统计分析,在此基础上提出了提高真空度、加强底吹氩搅拌强度、提高入炉钢液温度、提高人炉碳含量和降低人炉氮含量、增加VOD吹氧脱碳时的供氧量、高真空吹氩纯沸腾工艺、选用无碳、或低碳还原料等工艺技术措施,最后介绍了太钢这几年在VOD冶炼超纯铁素体不锈钢采取上述措施后所取得的效果。     

Thermodynamics of carbon in liquid manganese and ferromanganese alloys

The thermodynamics of carbon in manganese and ferromanganese melts were studied to predict the refining limit of carbon during the decarburization of molten ferromanganese. The equilibrium carbon content in a Mn-C melt was determined by the C-CO equilibrium in the presence of pure solid MnO at 1673 to 1773 K. The activities of manganese and carbon in the Mn-C melt were then calculated from the experimental results, the equilibrium constant for the reaction, and the Gibbs-Duhem equation integrated by the Belton-Fruehan treatment. The standard free-energy change of carbon dissolution in the manganese melt was determined to be 41,700 — 59.6 T J/g · atom, with the standard state taken as 1 wt pct carbon in solution. The effect of iron on the activity coefficient of carbon in ferromanganese was determined by measuring the carbon solubility in Mn-Fe melts. The first- and second-order interaction parameters between carbon and iron in ferromanganese melts were determined. The activity coefficient of carbon in the ferromanganese alloy melt can be expressed as

30 t VOD精炼含氮不锈钢底吹氮气合金化的生产实践

依据30 t VOD生产数据,在初始[C]0.50%~0.60%,初始[Si]0.12%~0.20%,初始钢水温度1 640~1 650℃,氩和氮气压分别为0.8×10⁶~1.0×10⁶ Pa和1.5×10⁶~1.6×10⁶Pa的条件下,对比底吹氩气和底吹氮气两种工艺在入VOD初始、吹氧脱碳以及还原脱气后的不锈钢（0.04%~0.06%N）中氮含量。结果表明,VOD底吹氮气精炼后Cr13型和Cr17型两类不锈钢的钢液氮含量为260×10^-6和300×10^-6,其氮合金化效果显著;常压下氮气搅拌Cr13型和Cr17型不锈钢钢液的平均增氮速率为40×10^-6/min和45×10^-6/min;钢液温度升高,增氮速率增加,通过降低VOD精炼不锈钢的钢液氧含量,能够提高底吹氮气的氮合金化效果。