酒钢SPCC钢的LF精炼脱硫

 通过热力学分析,建立了硫分配比与硫容量的关系,用热力学软件FactSage计算渣中Al2O3活度,用KTH模型计算渣的硫容量,对SPCC(一般用冷轧碳素钢薄板坯钢带)两个浇次10炉钢水在LF进站和出站时取钢、渣样以及测氧和温度,通过分析钢样和渣样成分以及生产检测数据,分析了温度、炉渣成分和钢水成分对LF精炼脱硫的影响规律。定义了硫分配比对钢液中溶解氧活度的急剧变化区(a［O］＜4×10-6),在该区内硫分配比对钢液中溶解氧活度十分敏感,钢液中氧活度的增大导致硫分配比的迅速减小,温度升高,a［O］升高,不仅抵消了升温对脱硫反应轻微的促进作用,反而使硫分配比随温度升高而减小。LF精炼过程Al-O反应未达渣-钢平衡,实际［O］活度介于平衡计算值与Al2O3活度为1的计算值之间,故渣钢硫分配比也介于二者之间。精炼渣二元碱度升高则硫分配比增加,wCaO/wAl2O3在1.6~2.0时脱硫效果较好,硫分配比并不随［Al］s含量的增加而增大,所以用增加w［Al］s来脱硫效果并不明显。钢中夹杂铝(w［Al］t-w［Al］s)降低到10×10-6以下,硫分配比明显升高。     

Characteristics of Deoxidation and Desulfurization during LF Refining Al-killed Steel by Highly Basic and Low Oxidizing Slag简

Steel and slag samples were taken at the start and the end of LF refining for steel plate cold common （SPCC）, in the compact strip production （CSP） process, and at the same time, the temperature and oxygen activity a[o] were measured by using an oxygen sensor. Furthermore, inclusions in steel samples were monitored by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It was confirmed that a [o] in liq- uid steel was in equilibrium with inclusion rather than with top slag during LF refining. Desulfurization was related to deoxidation since a[o] at slag-steel interface was clarified to be very close to that in liquid steel under the specific con- dition in LF with intense stirring by argon blowing and refined by highly basic low oxidizing slag for Al-killed steel. Sulfur partition ratio （Ls） was very sensitive to a[o]. Since a[o] increased rapidly with temperature rise, it not only offset promotion to desulfurization reaction with temperature rise but decreased Ls. For Al-killed steel, the.modifica- tion of Al2O3 for lowering the activity of Al2O3 in inclusion was believed to be favorable for both deoxidation and desulfurization during LF refining.     

酒钢CSP流程SPCC钢LF精炼渣-钢平衡及渣成分优化

 利用热力学计算软件FactSage确定了精炼渣中MgO质量分数合理范围为4%~8%,以6%最佳。由工业取样结果结合FactSage分析了1873K时SiO2-CaO-Al2O3-6%MgO准三元系液相区及CaO饱和的固液两相区渣-钢平衡。结果表明:高碱度高w(CaO)/w(Al2O3)(C/A)精炼渣有利于钢液的低氧低硫和低硅控制,但并非造得越“白”越好,相反过高的CaO对脱氧和硅含量控制不利。通过钢渣平衡分析得到了酒钢SPCC精炼渣优化成分范围(质量分数)为：CaO为50%~55%,Al2O3为30%~36%,SiO2为1%~6%,MgO为4%~8%,6%为最佳,碱度为9.0~14.0,w(CaO)/w(Al2O3)为1.5~1.8,实验室渣-钢平衡试验和工业生产结果均验证了优化的渣系较原渣系精炼效果更加优越,能够同时降低钢中总氧、硫和硅含量,也能有效控制钢中夹杂物的成分。     

KR脱硫渣的综合利用现状及其氧化去硫研究进展

KR脱硫的渣资源化利用有利于促进钢铁企业的绿色化发展.KR脱硫渣中主要成分为CaO,且含有质量分数为1.0％～2.5％的硫,直接将K R脱硫渣回用于冶炼工艺会导致钢液增硫.若能将渣中的硫脱出,可有效促进KR脱硫渣在钢铁冶炼工艺的资源化利用.因此,针对当前KR脱硫渣综合利用存在的问题,总结分析有关CaS氧化过程的热力学和...     

GCr15轴承钢LF精炼过程脱硫能力的热力学评价

通过现场取样分析和热力学计算,评价了工业化生产GCr15轴承钢LF精炼工序的脱硫能力.分析了精炼温度、钢中酸溶铝含量、精炼渣的光学碱度对LF精炼过程硫分配比的影响.由于实际精炼过程中脱硫反应未达到平衡,实际测得的硫分配比低于理论计算值.得到了精炼温度为1 830～1 855 K,钢中酸溶铝的质量分数为0.020％～o.050％,精炼渣光学碱度在0.760～0.795范围内,精炼温度、钢中酸溶铝、渣的光学碱度及渣中Al2O3、SiO2含量对硫分配比影响的回归方程,该方程可作为实际生产条件下LF精炼工序脱硫能力的评价依据.根据回归方程,设计了改变精炼渣组成的3因素4水平正交实验,分析了精炼渣二元碱度R2及Al2O3和SiO2含量对硫分配比的影响,得出渣-钢间最优硫分配比的精炼渣组成(质量分数)为:CaO 55.11％,Al2O3 30％,SiO26.89％,MgO 8％,光学碱度为0.777.     

CSP工艺含铝无取向电工钢中夹杂物的演变和控制

 为了更好地控制CSP工艺下电工钢中的夹杂物,研究了涟钢CSP工艺含铝电工钢夹杂物在精炼连铸热轧过程中的演变机理。RH合金化后钢中夹杂物有Al2O3,Al2O3 SiO2和Al2O3 CaO CaS 主要3种,RH出站和中包钢液中的夹杂物主要是Al2O3 CaO CaS和少量单独的Al2O3和CaS夹杂。减少钢液中夹杂物的主要措施是降低RH出站前的顶渣氧化性。热轧卷材样中夹杂物与钢液中夹杂物不同,主要是AlN和MnS,夹杂物总量与氮、硫质量分数呈正相关,氮元素的影响最显著。     

Dissolution of multicomponents during hydrothermal leaching of LF desulfurization slag

In light of the multicomponent dissolution equilibrium during the hydrothermal leaching of LF desulfurization slag, thermodynamic calculations were made and the dissolution equilibrium curves of calcium, aluminum and sulfur were plotted to analyze the interactions between these components and their influence on sulfur leaching. Furthermore, slag leaching experiments were conducted to investigate variation of pH and concentration of major components in the leaching solution. The results show that CaS(s) is easily soluble in water, and when pH>11. 4, CaS(s) dissolves to form Ca(OH)2(s). Use of hydrothermal leaching for sulfur removal from LF desulfurization slag is theoretically feasible. CaSO4(s) is difficult to dissolve and its solubility is always lower than that of CaS(s); therefore, slag oxidation affects negatively sulfur leaching. However, when the pH of the leaching environment is controlled to be above 12. 3, CaSO4(s) is gradually transformed into Ca(OH)2(s). Al2(SO4)3(s) is easily soluble, and it is unlikely that Al will react with sulfur in the solution to form a precipitate. The pH of the leaching solution rises with time and remains at about 12. Calcium concentration in the leaching solution is high, while Al concentration is low. Sulfur concentration in the solution increases with time, and Al in the slag has little effect on sulfur leaching. It is thus concluded that hydrothermal leaching is effective in removing sulfur from LF desulfurization slag.     

水钢LF精炼渣及造渣制度规划

精炼渣具有脱硫和净化钢液的作用,在炉外精炼渣中采用精炼渣精炼钢水已成为洁净铜生产重要的技术手段。论文根据钢种的质量要求,以脱硫和铜中夹杂物控制为目标,结合水铜主要生产品种,对LF精炼渣终渣成分和造渣制度进行了规划。在水钢目前生产工艺条件下,焊条焊丝钢精炼终渣成分控制CaO／SiO2=2．0～2．5,Al2O3=10％～15％;含铝冷镦钢CaO／Al2O3=1．6—1．8,SiO2〈8％;高碳硬线铜CaO／SiO2=2．5～3．5,Al2O3〈15％。精炼渣造渣制度均可采用转炉出钢渣洗,并在LF精炼炉补加渣料的方式进行。     

KR脱硫渣高温矿物组成及含硫相的析出行为

 KR脱硫渣是KR铁水预处理脱硫工艺的副产品,其磁选后尾渣中CaO质量分数大于50%。可将其用作优质造渣原料返回到转炉炼钢工艺中,降低转炉炼钢的原料消耗。但KR脱硫渣中的硫(w((S))=1.0%～2.5%)成为转炉冶炼循环利用的障碍,直接将其用于转炉冶炼会使钢中的硫含量增加。因此,根据工业KR脱硫渣的化学成分,以合成渣的形式对KR脱硫渣中矿物组成及含硫相的析出行为进行研究,旨在明确KR脱硫渣中各矿物相组成及炉渣中硫的析出行为和赋存状态,为后续通过氧化性气氛有效脱除KR脱硫渣中的硫提供理论参考。采用热力学数据库FactSage 8.0的Equilib模块对CaO-SiO₂-CaS-CaF₂基熔渣的凝固过程进行模拟,利用XRD、SEM-EDS对合成渣样品的矿物组成及微观形貌进行分析、检测。热力学计算结果表明,CaS的析晶温度为1 320 ℃,低于MeO#1相、MeO#2相及2CaO·SiO₂相的析晶温度。炉渣样品的面扫描分析结果表明,在实际凝固过程中,受残余液相黏度增大的影响炉渣中少量硫未能析出形成CaS晶体,则以非晶态的形式赋存在基质相中。KR脱硫渣主要由C₃S相、MeO#1相(CaO固溶体)、MeO#2相(MgO固溶体)、基质相和CaS相等矿物组成。炉渣中的硫主要以游离态CaS晶体形式赋存,少量以非晶态硫的形式赋存。炉渣中CaS晶粒主要沿着先析出的高熔点硅酸盐(C₃S)相边界析出。     

高端抗硫管线钢非金属夹杂物研究

采用扫描电镜和大样电解等检验方法对抗硫管线钢的冶炼过程试样和连铸坯中夹杂物的数量、尺寸、成分、形貌进行系统分析。结果表明:钢液经过LF精炼后,显微夹杂物的面积比降低了34.7%;中间包钢液的夹杂物面积比较VD出站增加了6.1%。LF进站钢液中的夹杂物主要为Al_2O_3夹杂物,在LF精炼和VD真空处理过程中由于钢渣间的相互作用,形成以CaO、MgO、Al_2O_3为主要组成的复合型夹杂物。钙处理后夹杂物中的CaO和Al_2O_3的物质的量比接近12∶7,并与钢液发生了脱硫反应,形成了含CaS的复合夹杂物。中间包开浇阶段铸坯中的显微夹杂物和大型夹杂物都明显高于稳定浇铸状态;在稳定浇铸状态下,铸坯中的w(T[O])小于15×10~(-6),大型夹杂物的含量小于0.2 mg/kg;大型夹杂物的主要来源是钢包引流砂、结晶器保护渣。     

IMCT模型和KTH模型在S50C钢脱硫实践中的应用

摘要：脱硫是LF精炼的主要任务之一，基于酒钢S50C中高碳钢的开发，对S50C钢LF精炼过程硫容量、硫分配比的计算方法进行了研究。主要利用IMCT模型和KTH模型对LF精炼渣的渣 钢硫分配比进行计算，并通过工业试验对计算结果进行验证。结果表明，IMCT模型和KTH模型的计算值均能表现从LF到站到LF出站的过程中脱硫反应向着平衡的方向发展，但是KTH模型的计算结果更为准确。因此，对IMCT模型进行了修正，修正后的模型也能较为准确地计算出LF精炼末期硫分配比。最后计算了CaF2含量对硫容量的影响，结果显示CaF2含量对平衡硫容量的影响较小。     

Desulfurization Behavior and Mechanism of CaO-saturated Slag

To develop a high-efficiency desulfurizer for the production of pipeline steel with the LD-RH-CC process, the desulfurization efficiency and mechanism of CaO-saturated slag were studied using a vacuum-induction furnace and Si-Mo electric resistance furnace.The results show that the desulfurization ability for slag with a small amount of solid CaO was highly enhanced under conditions of satisfied kinetics.The desulfurization reaction of CaO-saturated slag depended on the liquid slag rather than the solid CaO,as sulfur was not detected inside the solid CaO.The des-ulfurization efficiency of CaO-saturated slag was also influenced by the amount of residual liquid slag and its sulfur absorption ability.The sulfur absorption ability of CaO-CaF2 slag was analyzed to be much higher than that of CaO-Al2 O3-CaF2-(SiO2 )slag.Moreover,the effect of solid CaO on the desulfurization kinetics was evaluated and the ap-plication conditions of CaO-saturated slag were discussed.     

Experimental Study on Deep Desulfurizer in LF Process

 Abstract： CaO-Al2O3-SiO2-CaF2-MgO was selected as the slag system for desulfurization in LF process. The reaction between steel and slag during desulfurization has been simulated by using Factsage software to study the influence of component on the sulfur distribution ratio. In order to research the influence of CaO content, aluminum powder content and its granularity on desulfurization, laboratory experiments have been carried out in a 200 kg inductive furnace. Results showed that the optimal composition of deep desulfurizer is wCaO=64% and aluminium powder 10% with a granularity of 30 μm. Industrial trials showed that the main composition range of final slag in LF process is wCaO=530%-570%, wAl2O3=234%-251%, wSiO2=81%-100%, and wCaF2=32%-47%. The sulfur mass percent in steel is lower than 00008% with a desulfurization rate above 89%. According to the result of industrial production, this desulfurizer could meet the production requirement for ultra-low sulfur steel, of which sulfur mass percent is under 00015%.     

A Thermodynamic Model of Sulfur Distribution Ratio between CaO–SiO<Subscript>2</Subscript>–MgO–FeO–MnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Slags and Molten Steel during LF Refining Process Based on the Ion and Molecule Coexistence Theory

A thermodynamic model for calculating the sulfur distribution ratio between ladle furnace (LF) refining slags and molten steel has been developed by coupling with a developed thermodynamic model for calculating the mass action concentrations of structural units in LF refining slags, i.e., CaO–SiO₂–MgO–FeO–MnO–Al₂O₃ hexabasic slags, based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of structural units in CaO–SiO₂–MgO–FeO–Al₂O₃–MnO slags equilibrated or reacted with molten steel show that the calculated equilibrium mole numbers or mass action concentrations of structural units or ion couples, rather than mass percentage of components, in the slags can represent their reaction abilities. The calculated total sulfur distribution ratio shows a reliable agreement with the measured or the calculated sulfur distribution ratio between the slags and molten steel by other models under the condition of choosing oxygen activity based on (FeO)–[O] equilibrium. Meanwhile, the developed thermodynamic model for calculating sulfur distribution ratio can quantitatively determine the respective contribution of free CaO, MgO, FeO, and MnO in the LF refining slags. A significant difference of desulfurization ability among free component as CaO, MgO, FeO, and MnO has been found with approximately 87–93 pct, 11.43–5.85 pct, 0.81–0.60 pct and 0.30–0.27 pct at both middle and final stages during LF refining process, respectively. A large difference of oxygen activity is found in molten steel at the slag–metal interface and in bulk molten steel. The oxygen activity in molten steel at the slag–metal interface is controlled by (FeO)–[O] equilibrium, whereas the oxygen activity in bulk molten steel is controlled by [Al]–[O] equilibrium. Decreasing the high-oxygen-activity boundary layer beneath the slag–metal interface can promote the desulfurization reaction rate effectively or shorten the refining period during the LF refining process.     

冷却速率对KR脱硫渣中硫析出行为的影响

KR脱硫渣中主要成分(CaO)为转炉冶炼的优质造渣原料,通过氧化性气氛将渣中硫脱除后可将其用于转炉冶炼.但由于炉渣冷却制度不同,渣中硫的析出行为和赋存状态会发生变化,对炉渣氧化脱硫效果产生影响.基于此,以合成渣的形式探究冷速对KR脱硫渣中硫析出行为的影响,旨在明确KR脱硫渣中硫赋存状态及析出行为与冷却速率的关系,为后续...     

GCr15钢LF精炼渣系脱硫优化的研究

基于某钢厂现阶段LF精炼渣系脱硫效果差等问题,结合精炼渣脱硫机理进行实验研究。通过拟出10种精炼渣配方并对炉渣性能及钢中脱硫进行分析。研究发现,当精炼渣成分w(CaO)为45%~50%,w(SiO2)为18%~20%,w(Al2O3)为17%~21%,w(MgO)为9%~13%时脱硫效果较好,满足GCr15钢中脱硫要求。工业试验初步取得良好效果,为LF精炼渣系深脱硫提供依据。     

Numerical Investigation of Desulfurization Kinetics in Gas-Stirred Ladles by a Quick Modeling Analysis Approach

A quick modeling analysis approach for predicting the slag-steel reaction and desulfurization kinetics in argon gas-stirred ladles has been developed in this study. The model consists of two uncoupled components: (i) a computational fluid dynamics (CFD) model for predicting the fluid flow and the characteristics of slag-steel interface, and (ii) a multicomponent reaction kinetics model for calculating the desulfurization evolution. The steel-slag interfacial area and mass transfer coefficients predicted by the CFD simulation are used as the processing data for the reaction model. Since the desulfurization predictions are uncoupled from the CFD simulation, the computational time of this uncoupled predictive approach is decreased by at least 100 times for each case study when compared with the CFD-reaction kinetics fully coupled model. The uncoupled modeling approach was validated by comparing the evolution of steel and slag compositions with the experimentally measured data during ladle metallurgical furnace (LMF) processing at Nucor Steel Tuscaloosa, Inc. Then, the validated approach was applied to investigate the effects of the initial steel and slag compositions, as well as different types of additions during the refining process on the desulfurization efficiency. The results revealed that the sulfur distribution ratio and the desulfurization reaction can be promoted by making Al and CaO additions during the refining process. It was also shown that by increasing the initial Al content in liquid steel, both Al oxidation and desulfurization rates rapidly increase. In addition, it was found that the variation of the initial Si content in steel has no significant influence on the desulfurization rate. Lastly, if the initial CaO content in slag is increased or the initial Al₂O₃ content is decreased in the fluid-slag compositional range, the desulfurization rate can be improved significantly during the LMF process.     

Investigation on Non-Metallic Inclusions in LCAK Steel Produced by BOF-LF-FTSC Production Route

 The behavior of non-metallic inclusions in LCAK (low carbon aluminum killed) steel produced by BOF (basic oxygen furnace)-LF (ladle furnace) refining-FTSC (flexible thin slab continuous caster) production route was investigated. The results showed that, LF refining for LCAK steel could decrease the wT[O] significantly, and the inclusions were modified by Ca treatment, which prevented nozzle clogging efficiently. However, owing to the unstable casting condition in the earlier stage of casting, a severe reoxidation occurred, accompanied with mold slag entrapment. The transformation of non-metallic inclusions during the steelmaking process was Al2O3→MgO-Al2O3 type inclusion→MgO-Al2O3-CaO type inclusion with a CaS ring, and the mechanism of the transformation was proposed and discussed via thermodynamic and kinetic analysis. Besides, to avoid CaS precipitation, the product of w2[Al]×w3[S] in steel should be less than 2.0×10-10 at 1873 K, which remands higher desulfurization ratio during LF refining.     

LF-VD高效脱硫工艺

 为了研究LF-VD精炼工艺的脱硫效果,进行了9炉工业试验。通过对BOF-LF-VD和KR-BOF-LF-VD工艺冶炼中厚板钢中硫含量和炉渣成分的分析,研究了炉渣成分和工艺参数对脱硫的影响。结果表明,采用适宜的精炼渣系,通过LF-VD精炼能把钢中硫质量分数从转炉终点200×10-6左右脱至20×10-6以下;炉渣成分[w((MgO))]=4%～7%、[w((SiO2))]=7%～11%、[w((CaO))/[w((Al2O3))+w((SiO2))]]=1.62时,实现最高硫分配比接近500;VD精炼比LF精炼钢液搅拌强烈,能进一步脱硫。研究结果对优化中厚板炉外精炼脱硫工艺具有指导意义。     

电渣重熔工艺对高氮钢脱硫的影响

对电渣重熔制备高氮钢的脱硫过程进行了研究,分别采用不同渣系和熔炼速率对高氮钢进行制备。对电渣重熔前后夹杂物进行电镜及成分分析,分析结果表明:硫化物夹杂的平均直径和单位面积数量大大减少,夹杂物的主要类型为MnS+Al2O3复合型夹杂物;适度提高渣中CaO含量可提高硫分配比,是提高脱硫效率的有效手段。同时,实验结果表明重熔速率对电渣重熔中的脱硫率具有重要影响。通过脱硫动力学推导,发现重熔速率越低,脱硫效果越明显,但实验发现脱硫率随重熔速率的降低有时呈现先降低后升高的趋势,其原因在于渣池中发生硫化物富集,导致"回硫"现象发生,降低了脱硫率。