AOD炉冶炼含氮不锈钢氮成分控制的研究

对氮在不锈钢熔体中溶解的热力学和动力学行为进行了理论分析,指出氮在不锈钢熔体中溶解度随钢水温度降低和铬、锰、钼含量增加而升高,而随着镍和碳含量的增加而降低;对AOD炉冶炼不锈钢吹氮合金化工艺控制模型进行了理论研究和实际应用,指出在AOD炉中氮含量随着钢水碳含量、温度、供氧强度、吹氩强度的变化而变化,该工艺适合冶炼钢种的氮含量小于该钢种在常压下理论氮溶解度的90%,为保证氮成分精度,以小于80 %为宜.     

酒泉钢铁（集团）有限责任公司

AOD转炉,是整个不锈钢冶炼的关键环节。AOD的中心任务是“脱碳保铬”,即在吹氧脱碳的过程中尽量减少铬的氧化烧损。AOD转炉与碳钢转炉冶炼相比,最大的差异在于过程控制的不同。酒钢不锈钢转炉采用阀站控制技术以及转炉自动控制技术,可以满足控制要求。     

宝钢AOD炉冶炼不锈钢顶枪吹炼工艺分析

针对宝钢不锈钢分公司侧顶复吹AOD炉在实际使用过程中表现出来的脱碳速度偏慢、钢水中铬元素氧化量偏大、吹炼过程升温偏慢的情况,以实验室模拟研究结果为基础,通过将其顶部单孔氧枪改为三孔氧枪的方法,对比分析了AOD炉单孔顶枪、11°三孔顶枪和15°三孔顶枪在脱碳速度、钢水中铬氧化情况以及升温速度3个方面的各自表现.结果表明,当AOD炉以电炉提供的高碳母液为主原料时,在枪位设定合理的条件下,11°三孔顶枪的使用有利于进一步提高AOD炉脱碳速度、降低AOD炉钢中铬氧化并加快熔池升温速度;单孔氧枪由于孔数不足,其在AOD炉中的不锈钢冶炼效果不佳;15°三孔顶枪由于孔间夹角设定不合理,与宝钢不锈钢分公司AOD炉侧吹复合使用时效果不佳.     

AOD炉的高效化冶炼模型

 以往的AOD炉高效化冶炼研究往往通过提高供氧强度,优化转炉的炉容比,提高终点命中率等技术缩短冶炼周期,需要充分利用现有的设备,优化炉料结构和供氧制度,对生产工艺参数进行优化,充分利用这些物理热和化学热,实现AOD炉的高效化冶炼。开发了AOD炉高效化冶炼模型,在AOD炉物料平衡和能量平衡的基础上,结合AOD炉冶炼的工艺特征,建立AOD炉耗氧量和冶炼周期模型,分析了AOD炉冶炼周期随着铁水比和废钢比的变化趋势,得出冶炼周期最短时的炉料结构。结果表明：电炉不锈钢母液加铁水冶炼时,冶炼周期随着铁水比的增加而增加。电炉不锈钢母液加废钢冶炼时,冶炼周期随着废钢比的增加而增加。铁水加废钢冶炼时,冶炼周期随着废钢比的增加而延长。以硅铁为发热剂比以碳粉为发热剂冶炼周期短。     

宝钢不锈钢AOD炉侧吹工艺优化

通过对AOD炉冶炼不锈钢冶金过程进行动力学分析和数学模拟,阐述了AOD炉脱碳保铬过程的基本特征。根据AOD炉脱碳保铬时的临界碳含量,调整了宝钢不锈钢AOD炉的侧吹工艺,结果表明,AOD炉氧气利用率和铬元素收得率均有较为显著的改善。     

304不锈钢AOD冶炼过程脱碳保铬和铬烧损的研究

针对AOD+LF二步法冶炼304不锈钢冶炼过程,通过分析AOD炉精炼不锈钢脱碳保铬机理,结合75t AOD工业生产数据,建立了冶炼过程中钢液成分、温度和一氧化碳分压三者之间的定量关系,同时分析冶炼过程各阶段的渣成分,研究不同温度和吹气模式下钢液铬烧损情况,提出了优化304不锈钢AOD生产的措施,最终实现钢水窄成分与高效...     

GOR冶炼321不锈钢的工业试验

为研究GOR脱碳和脱氮及硅铁、铝锭复合脱氧对冶炼321不锈钢的影响,分析了GOR冶炼321不锈钢的工业试验,主要就利用GOR冶炼美标321不锈钢的工艺过程和相关消耗指标进行了讨论,重点研究了GOR冶炼321不锈钢的基本冶金原理,并根据冶炼实绩分析了脱碳保铬、脱氧脱硫及脱气效果。结果表明GOR具备冶炼低碳、低氮300系不锈钢品种的条件,通过氩氧比的调节可将钢水中的碳、氮质量分数均控制在0.015%以内,通过合适的脱氧操作可将钢水中的全氧和硫质量分数控制在0.003%以内,可为后续LF钛线处理创造良好条件。     

缩短RH脱碳处理周期的研究

为缩短首钢京唐RH冶炼IF钢的脱碳处理周期,对现行工艺进行了取样研究。结果表明:RH脱碳阶段表观脱碳速率常数K_c受真空度、供氧模式等条件的制约;纯循环阶段初期钢水全氧含量较高,且大型夹杂较多,随着纯循环时间的延长,全氧含量逐渐降低并趋于稳定。通过增设预抽真空操作、采用合适的供氧模式、优化定氧时间、调整最佳脱碳时间及纯循环时间等措施,RH冶炼IF钢时间平均缩短了8.3 min,且钢水具有良好的纯净度。     

45 t AOD精炼304不锈钢的造渣工艺实践

为降低AOD精炼的渣料和还原剂硅铁用量,对高铬钢液脱碳及还原过程渣碱度控制进行热力学分析,并进行45 t AOD冶炼304不锈钢造渣工艺试验。试生产结果表明,降低AOD精炼304不锈钢脱碳期炉渣碱度可减少钢水铬的氧化,同时有效减少AOD精炼渣料和还原剂消耗;AOD精炼过程石灰加入量平均从104.2 kg/t降至84.2~93.1 kg/t时,脱碳期炉渣碱度由平均13.44降低到10.64,AOD冶炼过程石灰、萤石、硅铁单耗分别平均降低14.7、5.4、4.4 kg/t,钢中Cr收得率、Ni收得率和硫含量分别为99.0%、98.3%和0.0025%。     

HRB400cE耐腐蚀钢的转炉冶炼工艺研究

文章研究了一种HRB400cE耐腐蚀钢的转炉冶炼工艺,包括检查转炉;向转炉内投入冶炼原料,加热以使转炉内冶炼原料液化成钢水;将氧枪插入至转炉内并在钢水上方通氧以对钢水脱碳;根据火焰亮度判定钢水脱碳进度并根据氧枪轮廓清晰度判定脱碳是否完成;向转炉内添加增碳剂以初步去除钢水内氧气;将钢水输送至钢包,添加硅锰合金以对钢水进行二次除氧;选取对应种类的金属以对钢水进行合金化处理。通过使用中控处理器建立预设的矩阵,根据钢水中的含碳量确定氧枪的通氧时长,使氧枪通入的氧气刚好与钢水内的碳元素反应从而保证使用指定量的氧气完成对钢水的脱碳,有效提高了工艺针对钢水的脱碳效率,从而提高了冶炼效率。     

Mathematical Modeling of Fluid Flow in Bath during Combined Side and Top Blowing AOD Refining Process of Stainless Steel: Application of the Model and Results

The mathematical model developed for the molten steel flow in the combined side and top blowing AOD refining process of stainless steel has been used to compute and analyze the flow fields of the liquid phases in the baths of the 120 t AOD converter and its water model unit with a 1/4 linear scale. The influence of the side tuyere number and the angle between each tuyere on the flows has been examined. The results demonstrate that the mathematical model can quite reliably and well model and predict the fluid flow in an AOD bath with the combined blowing. The liquid flow in an AOD converter bath with the combined blowing is resulted from the gas side blowing streams under the influence of a gas top blowing jet. The streams play a governing role on it; and the liquid in the whole bath is in active agitation and circulatory motion during the gas blowing process. The gas jet from the top lance does not change the essential features of the gas stirring and liquid flow in the bath, but can make the local flow pattern of the bath liquid obviously vary and its turbulent kinetic energy enhance. The changes in the tuyere position and number have similarly not altered the basic characteristics and patterns of the gas agitation and liquid flow and turbulent kinetic energy distribution in the bath. At a given tuyere number and gas side blowing rate or a given angular separation between each tuyere and gas side blowing rate, however, the variation of the angle between each tuyere or the tuyere number can locally change them. Using 6 tuyeres with 27° can reach the more uniform flow field and turbulent energy distribution of the liquid in the bath than taking 7 tuyeres with 18° or 22.5° and 6 tuyeres with 22.5°.     

Effect of Ar/O2 gas mixtures on heat‐transfer and fluid‐flow characteristics in AOD nozzles

A model of fluid flow and heat transfer in a nozzle used for injection of argon and oxygen in AOD converters was developed earlier. In this study the model was used to determine the effect of changes in the ratio of argon to oxygen in argon‐oxygen gas mixtures injected through the nozzle on fluid flow and heat transfer. It was found, for the studied conditions, that the temperature and laminar kinematic viscosity at the nozzle outlet were not dependent on the gas composition. However, the velocity, density, turbulent kinetic energy and dissipation of kinetic energy varied with a change in the fraction of oxygen injected. It is therefore concluded that for use as boundary‐condition input data for an AOD converter model (under development), it is important to be able to calculate reliable velocity and turbulence parameter data for gas mixtures of different argon/oxygen ratios.     

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.     

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.     

热风炉自动优化燃烧系统在承钢的应用

主要介绍了自动优化燃烧系统在承钢炼铁厂热风炉的应用情况。该系统在热风炉整个燃烧期可根据风温指标及顶温、烟气温度上升速率自动调整煤气使用量;同时根据烟气残氧量控制顶温在规定的上限值内,有效增加热风炉中下部蓄热室的蓄热量。实现了自动调整风煤比值,使煤气燃烧充分,有效提高了热风炉的热效率。     

On Increasing Mn Recovery During Production of Mn-Based Stainless Steel

Recovery of Mn in steel making process depends on various processing parameters such as temperature, flow rate ratio of oxygen and argon gas in AOD process, carbon content, slag basicity, and V-ratio, Si content etc. The effect of these process parameters on Mn recovery in Mn-based stainless steel production is studied and optimized to maximize Mn recovery. It is observed that highest Mn recovery is achieved when slag basicity is maintained in the range of 1.7–1.8 and V-ratio is kept at 1.5. Further, it is noted that at high temperature, recovery of Mn is less because loss of Mn due to oxidation increases exponentially with the increase in temperature. Maximum Mn recovery is observed at 1585 °C bath temperature. Reduction of MnO with coke forms CO₂ gas and free Mn in the melt. To maximize recovery of Mn in stainless steel, it is of paramount importance that oxidation of Mn is reduced and reduction of MnO is accelerated. Oxidation of Mn is minimized by reducing the flow rate of oxygen and reduction of MnO is accelerated by adding adequate amount of coke to the molten charge.     

基于案例推理的AOD炉能耗诊断系统

采用基于案例诊断技术对AOD炉能耗进行诊断,以AOD炉物料平衡和能量平衡为基础,引入载能体的概念,建立AOD炉的能值模型,对铁水比、废钢比、AOD炉处理时间和两炉间隙时间对AOD炉能值的影响进行模拟,确定其对AOD炉能值影响的权重,结合层次分析法确定各个影响因素的权重,采用案例推理技术对AOD炉能值进行诊断。将AOD炉能耗诊断系统应用到某不锈钢公司AOD炉上,诊断AOD炉能耗上升的因素,为降低AOD炉能耗提供了决策依据。     

Mathematical modeling of the argon-oxygen decarburization refining process of stainless steel: Part II. Application of the model to industrial practice

The mathematical model proposed and presented in Part I of the present work has been used to deal with and analyze the austenitic stainless steel making (including ultralow-carbon steel) and has been tested on data of 32 heats obtained in producing 18Cr9Ni-grade steel in an 18-t argon-oxygen decarburization (AOD) vessel. The results indicated that the carbon concentrations and bath temperatures at the endpoints of blowing periods, calculated by the model, are in excellent agreement with the determined data, and the Cr content after the predeoxidization, obtained from the model predictions, also agrees very well with the observed value. The Gibbs free energies of the oxidation reactions of elements can be used to characterize fully the competitive oxidation among the elements during the refining process and to determine reasonably the corresponding distribution ratios of oxygen. The critical carbon concentration of decarburization (after which the decarburization changes to become controlled by the mass transfer of carbon in molten steel) for the AOD refining process of austenitic stainless steel in an 18-t AOD vessel is in the range of 0.25 to 0.40 mass pct. The model can provide some very useful information and a reliable basis for optimization of the technology of the AOD refining process of stainless steel and control of the process in real time and online.     

Preliminary Investigation of Mathematical Modeling of Stainless Steelmaking in an AOD Converter: Application of the Model and Results

The changes in the contents of C, Cr, Si, and Mn in molten steel and the bath temperature during the refining of 304‐grade stainless steel, including both the oxidation (decarburization) and reduction processes, in a side and top combined blowing AOD converter of 120 t capacity have been predicted. The calculations were performed using the mathematical model proposed and presented in Part I of the present work [1] and were based on the designed operational mode of the AOD converter. The model predictions were compared to the referenced values given by the technological design. The results demonstrate that the predictions by the model are in good agreement with the reference values. Not only the competition of oxidation among the elements dissolved in the steel during the oxidative refining process and the corresponding distribution ratios of oxygen, but also the competition of reduction among the oxides during the argon stirring and reductive refining process and the relevant supplied oxygen ratios of the oxides, can all be characterized more comprehensively and determined more reasonably by using the Gibbs free energies of the oxidation and reduction reactions. Corresponding to the top, side, and side and top combined (overall) refining processes of 304‐grade stainless steel in a 120 t AOD converter, the carbon concentrations at the critical rates, i.e. the critical carbon concentrations, after which the decarburization changes to be controlled by the mass transfer of carbon in molten steel, are 1.20, 0.37 and 0.53 mass%, respectively, under the given designed operational mode. The model can offer some useful information for determining the technology of the side and top combined blowing AOD refining process of stainless steel.