AOD精炼不锈钢工艺发展

论述了国外AOD精炼不锈钢技术的发展。总结了太钢AOD精炼不锈钢在品种、质量、工艺研究方面的成果。对AOD炉材质进行了分析。     

宝钢不锈钢AOD炉长寿技术

从炉壳型式、渣系组成、侧吹风枪选用等方面对宝钢AOD炉的长寿技术进步进行了介绍与分析,通过相关的研究与改进,宝钢AOD炉炉龄由投产初期的45炉/炉役提高至目前的185炉/炉役。     

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。     

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.     

太钢新改造的3座AOD转炉投产及其先进的工艺控制技术

太钢3座40tAOD转炉改造后扩容到45t并于2004年4月成功投产,主要采用两步法生产铁素体和奥氏体不锈钢。介绍了该项目的主要特点以及奥钢联AOD技术特点。     

提高15t AOD生产节奏的措施分析

AOD炉的生产节奏直接决定了不锈钢生产企业的产能。通过对生产304不锈钢企业的分析，提出改善电炉初钢水质量、优化供气制度、控制冷料的加入量和提高工人操作熟练性的措施，这些措施的实施使15tAOD炉生产节奏得到明显的提高，生产效率提高了14．3％。     

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.     

不锈钢AOD转炉炉渣控制的试验研究

通过理论分析和现场试验,考察了氧化温度、还原碱度和还原时间对炉渣中Cr2O3含量的影响。结果表明:在AOD氧化阶段,通过调整物料加入方式,减小炉温的波动可减少铬的氧化;还原阶段提高还原碱度可促进还原反应的进行,还原时间应大于4 min,保证还原反应有充足的时间。通过以上控制措施,AOD转炉还原炉渣中Cr2O3含量从1.2%降至0.4%,达到国内领先水平。     

AOD炉采用双渣工艺冶炼1Cr13钢的实践

为了降低1Cr13不锈钢的冶炼成本,邢钢将AOD炉单渣操作改为双渣操作,以降低脱碳期石灰加入量;并采用一次还原后补加石灰,来保证终渣质量。实践表明:AOD炉单渣变双渣操作后,对于碳含量要求较高的1Cr13钢,后续炉渣碱度变化对增碳等产生的影响较小,并且前期渣量明显减少,石灰、萤石及硅铁每炉分别少用1 100~1 300,320~419及174~190 kg。     

不锈钢AOD渣粉尘控制及其工程性能

 不锈钢AOD渣在冷却过程中由于晶格转变体积膨胀导致粉化,易造成粉尘污染。研究表明,出渣时喷入含硼改质剂能有效抑制AOD渣从β-C2S相向γ-C2S相的晶格转变,从而使粉化扬尘率降低90.1%。对无害化处理后的不锈钢AOD渣进行资源化利用探讨,结果显示,由于钢渣具有水硬胶凝活性,可作为水泥砂浆掺合料取代部分水泥,掺量范围应在0～30%之间。同时,对AOD渣及其水泥试块进行毒性浸出检测,结果表明,其中总铬、六价铬等浸出值均低于标准限值,不存在重金属浸出的问题,可进行后续资源化利用。     

AOD冶炼脱碳反应模型与计算机模拟

AOD冶炼中,终点碳和终点温度的命中率是提高生产率和产品质量的关键。由初始温度,初始成分及补加合金量等原始数据,通过本模型可预报要达到目标终点碳所需要的脱碳时间以及相应的终点温度。本模型计算得到的终点碳与实际终点碳,在同等条件下,两者极为接近,可作为一般AOD冶炼中预报终点碳与脱碳时间关系之用。通过分级调整O2、Ar、N2气比例得到最佳脱碳效果,终点碳命中率可提高到98％以上,最高温度可以控制不超过1750℃,延长炉衬寿命。     

Overview:Development of Clean Steel Production at Baosteel

The development of clean steel technology at Baosteel can be dated back to the first production of IF steels and pipeline steels in the early 1990s.Now the technology has gradually covered nearly the whole range of products.This progressive development is introduced in the overview including the levels of cleanliness for some steel grades at Baosteel.The technologies at different processes for the production of clean steel and the removal of some impurity elements in molten steel are also discussed.Suggestions are given on the future research and development of clean steel technology at Baosteel in the aim to keep a sustainable development,which should focus on the basic research,inclusion control and making efficient use of inclusions,as well as stable and reliable low-cost manufacturing technology,removal of harmful residual elements,and the expanding of the technology to stainless steels and special steels.     

Study on Mass Transfer Characteristics in an AOD Converter Bath under Conditions of Combined Side and Top Blowing

The mass transfer characteristics in a steel bath during the AOD refining process with the conditions of combined side and top blowing were investigated. The experiments were conducted on a water model unit of 1/4 linear scale for a 120‐t combined side and top blowing AOD converter. Sodium chloride powder of analytical purity was employed as the flux for blowing, and the mass transfer coefficient of solute (NaCI) in the bath was determined under the conditions of the AOD process. The effects of the gas flow rates of side and top blowing processes, the position arrangement and number of side tuyeres, the powdered flux particle (bubble) size and others on the characteristics were examined. The results indicated that, under the conditions of the present work, the mass transfer coefficient of solute in the bath liquid is in the range of (7.31×10^?5‐3.84×10^?4) m/s. The coefficient increases non‐linearly with increasing angle between each tuyere, for the simple side blowing process at a given side tuyere number and gas side blowing rate. The gas flow rate of the main tuyere has a governing influence on the characteristics, and the gas jet from the top lance decreases the mass transfer rate, the relevant coefficient being smaller than that for a simple side blowing. Also, in the range of particle (bubble) size used in the present work and with all other factors being constant, raising particle (bubble) size increases the coefficient. Excessively fine powder particle (bubble) sizes are not advantageous to strengthening the mass transfer. With the oxygen top blowing rate practiced in the industrial technology, the side tuyere arrangements of 7 and 6 tuyeres with an angular separation of 22.5° and 27° between each tuyere, as well as 5 tuyeres with an angle of 22.5° between each tuyere can provide a larger mass transfer rate in the bath. Considering the relative velocity of the particles to the liquid, the energy dissipation caused by the fluctuation in the velocity of the liquid in turbulent flow and regarding the mass transfer as that between a rigid bubble and molten steel, the related dimensionless relationships for the coefficient were obtained.     

钢包和中间包内衬耐火材料与碳钢的化学反应

在有些情况下,对钢产品内部质量的影响并不取决于生产过程中的误操作,而是低估了液态钢水与不同工序中接触到的材料间的化学反应。尤其是在铸锭生产中,这一点尤为明显。讨论了钢包与中间包内衬耐材与普碳钢间发生的化学反应。这些试验涉及高铝质、铝硅质、铝镁尖晶石质耐火材料,研究了它们在液态钢水中形成夹杂物的倾向性。试验结果表明,在钢水—耐材接触面上会产生一个富含MnO的新相,这一新相的量与二氧化硅在耐材中的活性及锰在钢液里的活性成正比。试验还表明,由液态钢水与耐火材料相互反应产生的接触面可产生新的外来夹杂物进入钢液中。试验结束后,对钢样中新的夹杂物成分做的分析表明,成分取决于耐材—钢水接触面的组成。因此,不同钢厂应该结合自身生产的钢种产品化学组成来选用耐火材料的化学成分设计。     

不锈钢AOD渣固化效果影响因素及其机理

 不锈钢氩氧脱碳（AOD）渣在冷却过程中易发生体积膨胀导致粉化扬尘,这不仅会对环境造成严重污染,给人体带来很大危害,还会造成资源的浪费,因此急需解决不锈钢渣的粉化扬尘问题,提高不锈钢渣的利用率。对不同改性剂对渣的粉化抑制效果进行研究,结果表明,随着B2O3和P2O5掺量的增加,对AOD渣有明显的固化效果,随着CuO的增加,AOD渣没有明显固化。分析原因表明,通过向不锈钢渣中添加半径比Si4+小的离子如B3+、P5+,可以使其在2CaO·SiO2的晶界或位错上富集,降低缺陷的自由能,降低[γ-2CaO·SiO2]成核的驱动力,抑制[γ-2CaO·SiO2]晶核的形成及长大,使2CaO·SiO2可以更好地稳定在[β]相,从而抑制了不锈钢渣的粉化扬尘。     

提高LF精炼钢包寿命的措施

精炼温度高造成渣线侵蚀严重以及炉渣对耐火材料的侵蚀，是影响精炼钢包寿命的主要原因。石横特钢厂采取稳定精炼初始温度；加强中间包烘烤；采用埋弧渣技术，制定合理的分钢种精炼温度等措施，使精炼钢包的平均使用寿命比４８炉次提高到５３炉次，耐火砖消耗降低了０．７９ｋｇ／ｔ钢。     

Mechanism and Prevention of Disintegration of AOD Stainless Steel Slag

 During the cooling process of AOD (argon-oxygen decarburization) stainless steel slag, the serious disintegrating problem happened, which will cause serious environmental pollution. The disintegrating mechanism of the AOD slag was analyzed in detail, and experimental research on prevention of disintegrating of AOD stainless steel slag was developed by adjusting the basicity of the slag and adding the quartz sand and borax. The disintegrating problem during the cooling process of AOD stainless steel slag is caused by the 2CaO·SiO2 phase transformation from α＇-C2S to γ-C2S. By means of adjusting the basicity of the AOD stainless steel slag from 2 to 1. 5 by adding quartz sand, disintegrating of slag was prevented. But the adding amount must arrive at 15% which increases the difficulty of industrialization. Disintegration of AOD stainless steel slag can be effectively controlled by adding borax, and the adding amount is only 0. 5%-0. 8%. This method can be easily industrialized.     

高炉耐火炉衬设计原则及“陶瓷杯”的应用

随着新型耐火材料的发展，“耐火材料法”在高炉内衬的设计中也得到了越来越广泛的应用，采用该法的主要好处是热损失小、炉缸状况稳定。以“耐火材料法“为基础，将导热性不同的材料进行合理安排后设计出了用于高炉炉缸的“陶瓷杯”。从１９８４年到１９９３年已有２３套“陶瓷杯”得到了安装或订购。     

炼钢工艺制度对180t钢包内衬寿命的影响

分析了出钢温度、钢包渣特性、精炼率与精炼时间、造渣材料和生产组织等炼钢工艺制度对天津天铁冶金集团热轧板有限公司180 t钢包内衬寿命的影响,对提高钢包内衬寿命、降低耐火材料消耗具有指导性意义。