炼钢过程底吹气体的冶炼效果对比

 基于炼钢过程底吹气体热力学及动力学进行分析,研究了底吹氧气、二氧化碳、氩气、氮气的冶炼效果。研究结果发现,氩气或氮气不与熔池元素反应,底吹时熔池温度基本不变,钢中氮质量分数较高;底吹氧气或二氧化碳时,脱碳速率和钢中氮、氢质量分数基本相同,熔池温度升高了162和45 ℃。同时发现,与底吹氧气相比,二氧化碳可减少炼钢烟尘量,炉渣中[w((TFe))]降低2.50%,[w((O))]降低90.2%。     

超低碳钢RH混合喷吹Ar-CO2冶金反应特性

 钢铁生产过程CO₂的资源化利用对中国“碳达峰,碳中和”目标的实现起着重要作用。氩气驱动的RH(ruhrstahl-heraeus)真空装置是超低碳钢精炼的关键设备,利用高真空下钢水循环流动可有效脱碳、脱气和去除夹杂物。由于真空条件下CO₂可直接与钢水中碳反应生成CO,在实现脱碳的同时可促进熔池搅拌。因此,尝试将Ar-CO₂混合气体作为提升气体引入超低碳钢RH脱碳过程。首先,针对CO₂在RH脱碳条件下的冶金反应行为,通过热力学理论分析了不同压力下Fe-C-O熔体与Ar-CO₂的反应特性。其次,搭建了Ar-CO₂混合气体作为RH提升气体的工业试验平台,通过工业性试验研究了超低碳钢RH脱碳过程混合喷吹Ar-CO₂对钢水脱碳、脱氮和温降的影响。Fe-C-O熔体与Ar-CO₂反应热力学表明,在低于100 kPa和超低碳条件下,Ar-CO₂混合气体中的CO₂仍可能与钢水中碳反应,从而促进RH脱碳和脱气。工业性试验表明,喷吹100% CO₂、50% Ar+50% CO₂和100% Ar炉次出站平均碳质量分数分别为0.001 50%、0.001 57%和0.001 19%,因而混合喷吹Ar-CO₂并不会显著影响RH脱碳效率。同时,由于CO₂与钢水中碳反应十分有限,与喷吹100% Ar相比,喷吹100% CO₂和50% Ar+50% CO₂对RH脱氮效率和钢水温降没有明显影响。因此,超低碳钢RH脱碳时,完全可采用CO₂取代部分或全部氩气作为提升气体,尽管无法提高精炼效率,但仍具有显著的经济价值和环保优势。     

不锈钢冶炼底吹CO2对熔池动力学条件影响

 近年来,CO₂在钢铁行业的资源化利用技术被广为开发,研究表明CO₂在不锈钢冶炼中的应用颇具潜力。通过建立底吹CO₂气泡反应动力学模型并结合水力学模拟试验研究,量化研究不锈钢冶炼条件下底吹CO₂对熔池动力学条件的影响。由于CO₂脱碳导致气体体积增加会造成气泡膨胀或分裂的情况不明确,假设两种极端条件,即条件a,CO₂反应气泡体积增大后只膨胀不分裂;条件b,CO₂反应气泡体积增大后只分裂不膨胀,并取某厂70 t不锈钢炉冶炼中期工艺参数对两种条件下CO₂气泡反应动力学进行计算。结果表明在本研究条件下,不锈钢冶炼底吹CO₂反应后气体增加无论是导致气泡膨胀或者分裂,反应平衡时气泡最终体积约为初始体积的1.3倍,并且气泡体积随反应时间的变化呈线性关系。水力学模拟研究发现,相对于对照组试验,条件a和条件b下熔池的混匀时间分别缩短16.5 s和8.4 s,因此得出实际底吹CO₂在反应后会使熔池混匀时间缩短8.4~16.5 s,使熔池的动力学条件得到显著改善。此外,通过墨水示踪剂观察底吹CO₂对熔池流场变化的影响,发现底吹CO₂反应后导致气泡膨胀会促进熔池的溶质向横向扩散,相对抑制溶质在纵向的扩散速度;相反地,CO₂反应后导致气泡分裂会促进熔池的溶质向纵向扩散,相对抑制溶质在横向的扩散速度。     

AOD炉中氧化钼直接合金化冶炼不锈钢的热力学分析

 研究了钼元素的氧化反应以及三氧化钼的还原反应,并分析了氧化钼的加入对AOD冶炼不锈钢过程以及不锈钢液成分的影响;在此基础之上,研究了严重影响钼收得率的氧化钼挥发问题,最后分别探讨了去碳保钼以及去碳保铬的热力学条件。通过上述的计算和分析,认为氧化钼接入AOD炉中直接还原冶炼不锈钢是可行的,但在加入时,需配入一定量的还原剂和固定剂,这样才能降低氧化钼的加入对钢液质量以及钢液温度的影响,同时提高钼元素的利用率并冶炼出优质不锈钢种。     

RH碳酸盐分解CO2脱碳工艺

 提出RH碳酸盐分解CO2脱碳工艺。通过从RH上升管喷吹碳酸钙粉剂实现钢水脱碳和净化钢液的目的。分析RH碳酸盐分解CO2的脱碳机理,并进行工业试验,考察RH碳酸盐分解CO2脱碳工艺对钢水洁净度的影响。结果表明,采用RH碳酸盐分解CO2脱碳工艺缩短RH精炼处理时间3 min,吨钢成本降低3～5元。铸坯的平均[w(T[O])]可达0.001 0%以下,显著提高钢水的洁净度。     

Chromium Recycling from Argon-oxygen Decarburization Dust in Hot Metal Pre-dephosphorization Process

The chromium recycling from the stainless steel dust of an argon-oxygen decarburization (AOD)furnace during a hot metal pretreatment process was investigated.Experiments at different temperatures or with different amounts of AOD dusts were carried out in a laboratory furnace equipped with MoSi2 heating elements and subsequently industri-al experiments were conducted in a stainless steelmaking factory,in order to study the thermodynamic mechanism of C and Si reacted with Cr2 O3 to get Cr from AOD dust.The results showed that the reaction between C and Cr2 O3 occurred below 1 572.18 K.Although its reducing ability was weaker than that of Si,C enabled the Cr in Cr2 O3 in the AOD dust to be recycled using the Si in the slag.By combining the AOD dust added in an earlier stage,the hot metal pretreatment slag added in a later stage could not only recycle Cr from AOD dust but also remove Si,S,and P.Higher hot metal temperatures resulted in higher Cr content and lower remained P concentration in the molten iron.     

Effects of Si and Cr on Complete Decarburization Behavior of High Carbon Steels in Atmosphere of 2 vol.% O2

The effects of chemical compositions,especially silicon and chromium contents,on the complete decarburization behaviors of steels in atmosphere of 2 vol.% O_2 and 98vol.%N_2 were investigated by using a simultaneous thermal analyzer.Complete decarburization was observed at both 750 and 800 ℃ for 60Si2 Mn A steel,while 750 ℃ only for 92 A steel.For GCr15 steel,no decarburization was found at 750 or 800 ℃,and only partial decarburization was observed at 850 ℃.It indicates that silicon promotes while chromium prevents the complete decarburization of steels in atmosphere with 2 vol.%O_2.The main reason is that silicon increases while chromium reduces the equilibrium concentration of ferrite at the interface of ferrite and austenite,which results in the complete decarburization.     

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。     

RH强制脱碳与自然脱碳工艺生产IF钢精炼效果分析

西昌钢钒厂由于转炉热量不足而以转炉—LF精炼—RH精炼—连铸工艺生产IF钢,为探究RH强制脱碳与自然脱碳工艺生产IF钢精炼效果,采用生产数据统计、氧氮分析、夹杂物自动扫描、扫描电镜和能谱分析等手段,对不同脱碳工艺对顶渣氧化性以及钢的洁净度影响进行了详细研究。结果表明:（1）与自然脱碳工艺炉次相比,采用强制脱碳工艺的炉次在转炉结束与RH进站钢中的平均[O]含量更低;（2）两种工艺脱碳结束钢中的[O]含量基本在同一水平;（3）强制脱碳工艺的炉次在RH结束时渣中平均T.Fe的质量分数降低了1.3%。在能满足RH脱碳效果的前提下,尽量提高转炉终点钢液碳含量、降低钢液氧含量,后续在RH精炼时采用强制吹氧脱碳工艺,适当增大吹氧量来弥补钢中氧,可显著降低IF钢顶渣氧化性。自然脱碳工艺与强制脱碳工艺控制热轧板T.O含量均比较理想;与自然脱碳工艺相比,强制脱碳工艺可有效降低IF钢[N]含量,这与强制脱碳工艺真空室内碳氧反应更剧烈所导致的CO气泡更多和气液反应面积更大有关。脱碳工艺对IF钢热轧板中夹杂物类型、尺寸及数量没有明显影响,夹杂物主要由Al₂O₃夹杂、Al₂O₃–TiO_x夹杂与其他类夹杂物组成,以夹杂物的等效圆直径表示夹杂物尺寸,以上三类夹杂物平均尺寸分别为4.5、4.4和6.5 μm,且钢中尺寸在8 μm以下的夹杂物数量占比高于75%。在RH精炼过程中,尽量降低RH脱碳结束钢中[O]含量,有利于提高钢液洁净度。      

转炉应用CO2技术

 通过对转炉顶吹CO2的热力学分析,结合实验室模拟转炉顶吹O2＋CO2混合气体试验结果,确立了CO2在转炉中应用的关键参数。得出在转炉中顶吹纯CO2虽可脱碳,但温降较大,顶吹CO2供气强度为3.0 m3/(t·min)时,钢液温降速率为15.1 ℃/min;通过喷吹O2＋CO2混合气体可实现温度平衡,但CO2配比的最大理论比例为79.1%;随着混合气体中CO2比例增大,吹炼终点钢液碳氧积降低,当[φ(CO2)∶][φ(O2)＝1][∶]1时可控碳氧积为(25～32)×10－8。     

铬矿熔融还原不锈钢直接合金化的热力学分析

 针对铬矿熔融还原法不锈钢直接合金化工艺中的热力学问题,利用热力学参数状态图、化学反应等温方程式等进行了理论分析和计算,为在转炉中用铬矿实现钢的直接合金化的热力学可行性提供了理论依据。结果表明：转炉内用铬矿熔融还原直接合金化是可行的,且必须外加还原剂;增加渣中(Cr2O3)含量,适当提高碱度,可以降低(Cr2O3)开始还原温度;渣中铬氧化物以(CrO)形态存在时,开始还原温度较低;(FeO)含量越低,(Cr2O3)开始还原温度越低。     

转炉多元喷吹提钒的基础研究

转炉提钒是实现钢-钒分离的关键环节,反应动力学条件弱严重影响转炉提钒效果.基于此,提出转炉多元气体喷吹提钒,通过热力学研究了 CO2与C、V反应的选择性氧化转化温度,根据物理热及化学热两方面分析了多元气体的综合冷却效果,并利用熔池搅拌能量密度量化了多元气体的搅拌能力.研究表明:利用多元气体喷吹提钒是可行的,CO2的物理...     

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%。     

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。     

DC06 IF钢精炼渣成分优化及钢 渣中氧的控制

摘要：无间隙原子钢（IF钢）对含铝夹杂物要求极为严格。为冶炼洁净IF钢,采用热力学软件FactSage 7.0对IF钢精炼渣系做了优化计算,并采取6组工业实验做验证,根据结果提出改进措施。实验中采取氧传感器、碳硫分析仪及ICP AES对钢和渣成分进行检测,并通过ASPEX自动扫描电子显微镜检测钢中夹杂物成分与数量。热力学计算及实验研究发现,转炉脱碳结束时钢液中碳质量分数宜控制在0.04%,转炉渣中FeO质量分数控制在149%以内,降低钢中［O］质量分数到470×10-6。精炼时控制补吹氧炉次比在64%以下,补吹量在17m3内,精炼渣中SiO2、MgO及TFe质量分数分别控制在6%~8%、6%和5%~10%,钙铝比控制在1.4~1.6时,钢中［O］质量分数可控制在10×10-6,且该精炼渣系对Al2O3有较好的吸附性。在确保精炼脱氧的同时,降低钢液二次氧化,达到IF钢洁净冶炼目的。     

Thermodynamic Assessment to Chromium Oxidation in the Production of Stainless Steel

A solution model called ε approach is applied to predict the thermodynamic solution behaviour of Cr in steel melts. The calculated results are supported by the available experimental results. Further predictions on chromium scorification are achieved in view of melting and refining processes for Cr‐containing steels. Chromium reduction from slags after meltdown during EAF melting and AOD or VOD refining treatment is important for the production of Cr‐containing steels. It is thermodynamically predicted that chromium is inevitably oxidized during decarburization process which coincides with the industrial and experimental results. Minimum oxidation of chromium can be reached by lowering the partial pressure of CO gas at high temperatures.     

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.     

LF钢包吹氩过程的数值模拟

根据对LF钢包吹氩过程的模拟结果,得出最佳喷吹流量,这样可以提高吹氩气体对钢液的搅拌效率、加快温度的均匀化,同时也有利杂物的去除.通过对气泡脱碳的研究,能准确控制钢中碳含量、提高钢水品质、优化钢的质量.     

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: 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.