提高转炉生铁比问题分析及控制措施

对因铁水供应不足,提高生铁比后在冶炼控制中出现前期熔池温度低、废钢和石灰不易熔化、炉口溢渣、金属消耗增加、脱硫困难、终点命中率低等问题进行分析,介绍了相应的预防措施和处理方法。     

单渣脱磷石灰消耗量预报模型的应用与分析

以物料平衡和热力学平衡等为理论基础,通过钢厂数据对理论结果进行修正,应用Visual Basic软件设计单渣脱磷过程石灰消耗量预报模型。预报的石灰消耗量与钢厂数据进行对比,误差范围在20%以内的占到93.4%,10%以内的占到82.7%。通过该模型分析铁水硅、磷质量分数和终点磷质量分数对石灰消耗量的影响。结果表明,随着铁水硅、磷质量分数提高及钢水终点磷质量分数降低,石灰料消耗量变大。铁水磷质量分数超过临界值时,石灰消耗量显著增加,在铁水硅质量分数分别为0.2%、0.4%、0.6%和0.8%的条件下,铁水临界磷质量分数分别为0.15%、0.14%、0.13%和0.12%;终点磷质量分数小于0.01%时,石灰消耗量显著增加,经济条件变差,小于0.007%时,随着石灰消耗量增加,终点磷几乎不变,单渣法不适合生产磷质量分数低于0.007%的超低磷钢。     

生铁块加入量对转炉吹炼过程的影响

中小转炉钢厂为了增加钢产量,往转炉内过量加入生铁块.在生产中出现熔池温度低、废钢和石灰不易熔化、炉口溢渣、金属消耗增加、脱磷困难、终点命中率低等问题.中小型转炉内生铁块的加入量不应超过10%,使转炉吹炼过程中保持正常的熔池升温和成渣状况.     

不锈钢喷粉吹氧法铁水脱磷工艺

为了满足生产超低磷钢的预脱磷要求,对不锈钢铁水脱磷工艺进行介绍。在45 t钢包中进行石灰喷粉+吹氧的工业试验,结果表明,在铁水脱硅期达到预期效果(铁水w([Si])≤0.1%)后,铁水脱磷期可实现平均脱磷率大于88%。根据试验数据,分别回归出脱硅期和脱磷期的脱磷率、磷分配比的计算公式。通过添加萤石能够获得较好的铁水脱磷效果,随着铁水硅含量变化,铁水温度、吨钢耗氧量、石灰消耗量、炉渣碱度的增加,铁水的脱磷率明显增加。炉渣w((TFe))的增加对铁水脱磷率的影响不显著。研究认为,目前采用的石灰喷粉+吹氧冶炼进行铁水脱磷处理是行之有效的不锈钢铁水脱磷方法。     

经济性冶炼含磷耐候钢的工艺开发

结合耐候钢的钢种特点,采用不加白灰的少渣冶炼方法,成功地开发出经济性冶炼含磷耐候钢的生产工艺,并分析了含磷耐候钢的经济性冶炼工艺对冶炼周期、终点磷含量、耗氧量、熔剂消耗、吹损的影响。实践表明,采用经济性冶炼含磷耐候钢工艺后,吹氧时间缩短1.14 min/炉,生产能力提高,成本明显降低,具有显著的经济效益。     

梅钢转炉低成本冶炼耐候钢SPA-H

为发挥梅钢中磷铁水的优势,充分利用磷资源,降低成本,利用梅钢现有转炉模型计算了石灰加入量,分析了梅钢转炉冶炼过程中熔池磷含量与吹氧量的关系及脱磷反应的热力学条件,并据此采取了减少石灰加入量和低氧枪枪位操作等措施,降低了转炉终点磷的分配比,生产出低碳和高吹炼终点磷含量的钢水,降低了冶炼物料消耗和合金消耗,使转炉冶炼含磷耐候钢SPA-H等钢种成本低于其他钢种.     

大型转炉优化造渣工艺提高脱磷的效果

 针对转炉冶炼存在的转炉前期化渣速度慢,冶炼终点钢水、炉渣氧化性高,终点磷含量控制不稳定等问题,利用炉渣熔化性测定、热力学平衡计算、炉渣矿相分析的方法研究了260 t转炉造渣、供氧工艺。结果表明,转炉初期渣熔化温度为1 330 ℃,不利于转炉前期化渣;终渣熔化温度为1 200 ℃,不利于转炉后期的炉衬维护;终点钢水磷含量与渣钢间磷平衡值差距较大,说明转炉吹炼终点动力学条件不足;炉渣中游离氧化钙含量较高,有部分未熔化的石灰。通过优化转炉渣料加入顺序和数量,强化转炉终点氧枪枪位控制、底吹搅拌等技术措施,可获得较高的转炉终点脱磷率和渣-钢间磷分配比,使终点渣-钢间磷含量更接近平衡;终点炉渣发育良好,游离氧化钙含量适中。     

基于多功能转炉炼钢法的连续循环冶炼过程

为了研究脱碳渣在脱磷期的重新利用,基于多功能转炉炼钢法进行连续循环冶炼实验.实验发现:脱磷阶段渣中较低的Fe O含量、吹炼5 min左右,[C]≥2.8%的条件下,可实现转炉熔池内铁液[P]≤0.025%的脱磷效果,并对低（Fe O）含量炉渣的脱磷可行性进行热力学计算;随着循环的进行,石灰加入量逐渐降低,由65 kg·t-1降低至31 kg·t-1,转炉冶炼终点钢水[P]量由0.018%降低至0.005%,2~4炉后达到平衡状态;在循环过程中,脱磷阶段结束倒出炉渣60~80 kg·t-1,整个循环结束一次性倒出剩余全部炉渣120~130 kg·t-1,平均渣量为83 kg·t-1左右,较普通工艺的120 kg·t-1渣量有大幅度减少.      

100t转炉用含钛铁水冶炼高碳钢的留渣+单渣操作实践

针对100t转炉用含钛铁水冶炼高碳钢的前期成渣难于熔化、脱磷率低的问题,分析了含钛铁水转炉炼钢的成渣过程和炉渣的物理特性,开发了留渣+单渣工艺技术。循环利用终点炉渣,充分发挥渣中10%～13%FeO高（FeO）含量的特点,快速把含钛铁水冶炼前期的CaO-TiO₂-SiO₂三元渣系转变为CaO-TiO₂-SiO₂-FeO四元渣系,脱除钢中大部分磷。控制终渣碱度大于3.2、（TiO₂）含量小于5%,使转炉出钢[C]≥0.20%、[P]≤0.014%,转炉炼钢脱磷率达到88%～92%,石灰消耗下降到28 kg/t钢。     

120t转炉高磷铁水冶炼高碳低磷钢生产实践

针对莱钢用高磷铁水冶炼高碳低磷钢容易出现终点碳过低和终点磷超标的问题,通过将脱磷渣碱度控制在1.5左右,实行双渣留渣工艺,提高前期底吹强度改善动力学条件,使用无氟化渣剂和增上滑板挡渣优化挡渣效果等措施,实现了高磷铁水冶炼低磷钢的高效生产。其中,终点磷质量分数可稳定控制在0.010%以下,脱磷率由89.80%提高到94.67%,终点碳质量分数控制在0.15%以上,钢水氧化性降低,钢包渣厚降低了40mm,精炼成白渣时间减少,满足了高碳低磷钢洁净度的要求,取得了良好的经济效益。     

Thermomechanical Modelling for Refractory Lining of a Steel Ladle Lifted by Crane

Numerical methods can be applied on metallurgical processes like engineering design of a steel ladle. In this study, the thermomechanical behaviour of refractory lining of a steel ladle which is lifted by a crane was investigated. To simulate this behaviour coupled heat transfer – structural analysis was made by using FEM (Finite‐Elements‐Method). For these calculations a two‐dimensional, an axially symmetrical geometric model and a FE‐model of a steel ladle with wear lining consisting of MgO‐C brick in the slag zone and castable MgO‐Al₂O₃–spinel in the working zone were created. Thermal stresses, hydrostatic pressure, gravity of molten steel and slag and refractory lining were used as boundary conditions. The results gained from the calculations showed that the maximum total displacements were observed at the bottom lining of the ladle.     

Model of Desulphurization of Steel Melts in Ladles – Deoxidation and Slag Formers Calculation

The authors present their own model applicable for effective desulphurization of steel by ladle treatment. The model is based on a thermodynamic approach (equilibrium data) and technological data (correction factors). It consists of two parts. In the first part the authors present the formulae derived for estimation of the additions of deoxidation agents which ensure sufficiently low oxygen level prior to the desulphurization process, while the other part gives a qualitative and quantitative selection of slag formers to achieve low final levels of sulphur in steel. For the deoxidation process two variants were considered: (i) with Al only (for low silicon steels) or (ii) Al‐Si (for silicon steels) as deoxidizers. For the desulphurization process three variants were assumed as to ladle slag composition: (i) slag consisting of a fraction of furnace slag, lime addition and deoxidation products, (ii) slag made of synthetic CaO–Al₂O₃ and (iii) slag based on lime and fluorspar. The model formulae for desulphurization were derived using the sulphide capacity concept which relies on the optical basicity. In addition, rough estimates of the slag liquidus temperatures are given. A numeric example of the model application and the model algorithm (appendix) are enclosed.     

100t转炉低成本冶炼65Mn钢实践

通过优化100 t转炉冶炼65Mn钢工艺参数,包括装入制度的确定、加料方式的改进、供氧强度及变压变枪位操作方式的优化等,解决了65Mn钢留碳去磷的难题,提高了冶炼65Mn钢的一拉率,减少了跑渣的发生机率,提高了白灰的熔化效率,降低了白灰单耗,65Mn 钢冶炼成本降低了9.07元/t.     

转炉脱磷工艺的最新进展

转炉脱磷工艺利用了转炉容积大的特点,可以实现转炉前期快速高效低碱度脱磷.脱碳渣的循环利用降低了石灰等辅料消耗和渣量.在低温低碱度转炉脱磷的条件下,低温在热力学上有利于脱磷,但温度过低会使渣过于粘稠而影响动力学条件并使倒渣困难;适当提高碱度,脱磷效果较好.随着渣中氧化铁含量的上升,脱磷效果先上升后下降.转炉脱磷渣中固液两...     

Optimization of Intensified Silicon Deoxidation

For demanding wire applications steel cleanliness should be very high and the inclusions inevitably found in steel should be harmless. This means strict control of inclusions' size, quantity, and composition, pursuing deformable inclusions in rolling conditions. Primary inclusions are formed during steel treatment in the ladle. Most of these are removed to the ladle slag or on the lining. However, the rest of the inclusions still remain through the successive process stages, and some new inclusions are formed during casting and solidification. Conventionally, deformable inclusions are produced by Si–Mn deoxidation resulting in MnO–SiO₂–Al₂O₃ inclusions. This leaves, however, the oxygen content too high for demanding applications. In order to get really clean steel, the Si deoxidation needs to be strengthened by lowering the activity of SiO₂ forming in steel. This can be done by bringing the steel in intimate contact with a slag containing SiO₂–MnO–Al₂O₃ and additionally CaO and some MgO. With this kind of intensified Si deoxidation it is possible to produce steels with low oxygen content having inclusions that will elongate at rolling. In this paper thermodynamic examination of potential slag systems and compositions to equilibrate with steels having medium carbon and high silicon were scrutinized. The optimal slag composition for producing low‐O steels with deformable inclusions was evaluated by using FactSage thermodynamic calculation program. The lowest SiO₂ activities at the region in which slag is still liquid at 1400°C, can be found when slag composition is approximately 36–40 wt% SiO_2, 6–18 wt% Al₂O_3, 30–40 wt% CaO, 6–8 wt% MgO, and 2–4 wt% MnO. Industrial heats using intensified Si deoxidation and slag based inclusion engineering were produced in a steel mill with 60 tons heat size. Inclusions and slag compositions were in satisfactory accordance with the theoretical examinations, though some scattering was discovered.     

转炉溅渣护炉对钢水质量的影响

转炉采用溅渣护炉时溅渣层在下一炉冶炼过程熔入炉渣、能够促进石灰溶解、加速成渣过程。吹炼终点时溅渣怀未溅渣次钢中氧、磷、硫、氮平均含量基本相同,溅渣护炉对钢的质量没有影响。     

Slag formation in the tundish of a continuous-casting machine

Slag formation in the tundish of a continuous-casting machine is investigated during the casting of 360-t low-carbon and low-alloy steel melts. In casting 5–10 steel melts, the slag mass increases significantly, and its composition changes. That is largely associated with the supply of nonmetallic inclusions to the slag from the steel. In casting low-carbon steel, the mass of such inclusions is around 30% of the total mass of the final slag; in casting low-alloy steel, the figure is around 50%. A smaller factor responsible for the change in slag composition is solution of the refractory lining: 4–5% of the mass of the final slag for a fireclay lining and 14–15% for a magnesia lining. The change in slag composition increases its melting point to 80–140°C.     

基于单渣法的转炉适宜渣料冶炼

 为了进一步降低炼钢成本,南京钢铁股份有限公司100 t复吹转炉,基于单渣法操作,依托现有造渣料,通过转炉磷收支平衡和脱磷热力学计算,得出转炉脱磷所需的最小渣量,在单渣法终渣热态返回利用的基础上,探索出成本最低的适宜渣料冶炼技术,实现了石灰吨钢消耗降低42.4%,白云石吨钢消耗降低12%,石灰石吨钢消耗增加34.3%,吨钢成本降低4.64元/t。     

Simulation of Steel Refining Process in Converter

Steel refining is a complex phenomenon which depends on numerous variables, so, a kinetic approach is necessary for precise understanding of the refining process. In this study, based on a previously proposed model for hot metal dephosphorization, a new simulation model for the steel refining process in BOF is presented. In most cases, steelmaking slag is saturated with dicalcium‐silicate (C₂S) and it is well known that C₂S forms solid solution with tricalcium‐phosphate (C₃P) in a wide composition range and the partition ratio of phosphorus between C₂S and liquid slag is large. On the other hand, C₂S formed around the lime surface is known as a barrier to lime dissolution into liquid slag. In this simulation model not only the effect of solid phase in slag is considered but also the effects of temperature dependence of variables as well as top and bottom blowing and scrap melting are taken into account. The calculation results are compared with industrial data and the good agreement between experimental and simulation results evidence the validity of this kinetic approach to steel refining process in BOF. Moreover, by using this model the influence of various parameters on the reaction efficiency is discussed.     

炉渣的岩相研究在转炉炼钢中的应用

 岩相检验方法可以确定炉渣的矿相组成和分布。把岩相检验与炉渣化学成分、流动温度数据结合起来,可以更全面地了解炉渣的性质。介绍了不同成分铁水炼钢的炉渣岩相检验结果和特点。炉渣岩相研究结果为改进转炉造渣工艺、降低石灰消耗和延长炉衬寿命提供了科学依据。在转炉高效吹氧、低硅铁水炼钢和溅渣护炉技术开发中都起到了重要作用。