300 t复吹转炉冶炼X80管线钢磷含量控制

 通过对首钢京唐公司生产的X80管线钢复吹转炉炼钢过程磷质量分数的控制研究,从热力学上分析了炼钢终点渣钢间磷分配比较低的原因,同时给出了转炉终渣成分的调节方向,以及要得到相应脱磷率和终点磷分配比时转炉渣加入量的最佳值。研究结果表明,在现有工艺条件下,转炉炉渣中MgO质量分数偏高,导致终渣熔点较高,而转炉终点渣熔点较高又是转炉磷分配比实际值与理论值差距较大的主要原因。通过计算,在现有工艺水平下,转炉渣的加入量应控制在43~60 kg/t(钢)较为合适。     

转炉生产低磷钢的脱磷反应热力学

 为实现磷质量分数小于0.010%的低磷钢批量生产,系统研究了转炉脱磷反应热力学。分析了影响转炉渣-金间磷分配比LP的主要因素,研究了P2O5活度系数和脱磷反应氧分压的定量确定方式,以及碳、磷选择性氧化问题。研究结果表明：LP主要受氧分压、P2O5活度系数和温度的影响;P2O5活度系数采用修正的柯热乌罗夫规则离子溶液模型计算较为准确;脱磷反应氧分压受炉渣氧分压控制,炉渣氧分压主要取决于钢中碳含量、炉渣碱度和温度。对传统复吹转炉生产磷质量分数小于0.010%低磷钢的工艺条件是：终渣碱度w(CaO)/w(SiO2)≥3.0,终渣w(MgO)≤9.0%,终点碳w(［C］)≤0.065%,终点温度控制在1873～1923K范围。     

基于共存理论的转炉脱磷热力学分析

为了定量研究温度、炉渣成分、钢液成分对转炉磷分配比和平衡磷含量的影响,基于共存理论建立转炉炼钢六元渣系的组元活度计算模型和磷分配比L_P计算模型,将磷分配比模型计算结果与转炉炼钢实测磷分配比进行对比,发现两者吻合较好。定量计算结果表明,当炉渣碱度为3.8时,钢液温度从1 640升到1 680 ℃,平衡磷质量分数从0.011 5%增加至0.019 8%。同时定量计算了炉渣碱度及氧化铁含量变化对平衡磷含量的影响,但实际炉渣控制需要考虑炉渣黏度、铁损及炉衬侵蚀。转炉吹炼终点钢中元素含量数量级较小,计算表明终点成分变化对磷活度系数的影响不大,各元素对脱磷的影响主要体现在冶炼初期和过程。     

Development of Refractory Material from Water Quenched Granulated Ferrochromium Slag

High temperature refractory materials of refractoriness above 1665°C having refractory phases such as forsterite (Mg₂SiO₄), periclase (MgO) and spinel can be developed from the water granulated spongy ferrochromium slag granules (90% particle) of size below 3100 micron by MgO enrichment. MgO enrichment in ferrochrome slag can be achieved by a method comprises of grinding of granulated ferrochrome slag in presence of magnesite raw material followed by compaction and sintering. The ratio of MgO/SiO₂ > 2.2 and MgO/(Al₂O₃ + Cr₂O₃) > 1.71 in the final composition ensures the refractoriness above 1665°C.     

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。     

复吹转炉冶炼低磷钢试验研究

研究了复吹转炉铁水脱磷预处理,半钢倒渣后在同一转炉内进行少渣精炼冶炼超低磷钢的工艺。结果表明:在铁水磷含量0.13%条件下,半钢和终点渣碱度(CaO/SiO2)控制在2.0和3.6左右,TFe含量控制在18%左右,半钢倒渣量40%～60%,半钢脱磷率最高达65%,平均为50%,终点脱磷率最高98%,平均为94.6%,冶炼终点钢水磷含量控制在0.007%以下,最低0.003%,满足低磷钢生产要求。     

Phosphorus Capacity of CaO-SiO2-Al2O3-MgO-FexO Slag

The CaO-SiO2-Al2O3-MgO-FexO slag occurs in the production process of Corex ironmaking technology.Most of its metallurgical properties,especially the phosphorus property,are different from the slag produced from blast furnace or converter.In order to explore the dephosphorization ability of CaO-SiO2-Al2O3-MgO-FexO slag,its phosphorus capacity was measured at 1 673 Kby gas-slag-metal equilibrium technique.An iron crucible was used as the reaction vessel,Ag alloy with 0.2% P was used as the metal phase which equilibrated with CaO-SiO2-Al2O3-MgO-FexO slag,and a constant flow of CO-CO2-N2 gas was used to provide oxygen partial pressure in the experiment.The effects of MgO,FexO and basicity on slag phosphorus capacity were investigated by single factor test.The results show that the phosphorus capacity rises firstly and then decreases with increasing MgO content under the condition of basicity 1.3,FexO content of 2% and Al2O3 content of 12%.The phosphorus value reaches maximum as the MgO content is 8%.When the basicity of slag is 1.1,MgO content is 10%,and Al2O3 is 12%,the phosphorus capacity increases with the increase of FexO content.The phosphorus capacity rises linearly when the basicity is increased from 1.1to 1.5.     

Effect of ladle slag of previous heat on number of non-metallic inclusions in ladle treatment of tool steel

Abstract

Nine series of industrial trials were carried out using the same ladle in each series to examine the effect of ladle slag on the number of non-metallic inclusions in the next heat. Steel and slag samples were taken after ladle vacuum treatment for chemical composition analysis. Samples of the final steel product were examined to determine the number of non-metallic inclusions. It was found that the number of inclusions increased with SiO₂ content of the ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions.Theoretical analysis based on the experimental results suggested that the formation of 2CaO.SiO₂ followed, but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.     

Adhesive Behaviour of BOF Slag to BOF Lining Refractory in Slag Splashing Process

A slag layer is formed when slag is splashed onto refractory lining in BOF slag splashing process. The melting temperature of the slag layer and the adhesion of the slag layer to the lining refractory have an important effect on slag splashing and BOF lining life. This study investigates the adhesive behaviour of slag with different composition to lining refractories. It is shown that the slag can adhere to MgO particles in MgO‐C bricks well and no reaction is found between the MgO particles and the slag layer, but a gas gap exists at the interface between the slag layer and the MgO‐C matrix and there are iron granules within the slag layer, when the FeO content in the slag is high. The adhesion of the slag layer to the lining refractory can be improved with decreasing FeO content in the slag and lower carbon content in the MgO‐C bricks. BOF refractory lining life can be greatly increased due to better adhesion, high melting temperature, and stronger wear‐resistance of the slag layer.     

转炉大补炉后第一炉钢的脱磷探讨

转炉大补炉后冶炼第一炉钢时钢中磷含量容易偏高,有时甚至超出钢种要求的磷含量上限.结合某厂90t转炉大补炉后冶炼第一炉钢时的生产情况,分析了入炉铁水硅含量、脱磷剂加入量、碱度、渣中FetO、MgO和Al2O3含量对转炉大补炉前后钢水脱磷的影响,对改进脱磷效果提出了建议.     

双联脱碳转炉低硅半钢冶炼渣系的优化

 为减少脱碳炉粘枪和降低终点磷含量,运用化学分析、熔点试验、Factsage热力学模拟的方法对120t双联脱碳转炉的渣系进行了研究,阐述了渣系对冶炼顺行的影响,制定了新渣系控制的基本原则和终渣成分范围。工业应用新渣系后,脱碳炉的粘枪状况得到一定缓解,脱碳转炉渣量降低至34.7kg/t,终点磷的质量分数稳定在0006%~0.012%。     

Study of penetration and corrosion of olivine–periclase and periclase based tundish DVMs by molten slag

Abstract

To enhance the billet caster tundish life, this study examines the relevance of the replacement of regularly used olivine–periclase based mixes by purer MgO containing dry vibe mass (DVM). After service, tundish working lining samples were studied by scanning electron microscopy energy dispersive spectroscopy to understand the influence of MgO saturation of the adhering slag and working lining interaction with the infiltrated slag. The result showed that the tundish working lining was penetrated and corroded by the molten slag for both DVM recipes. However, an increase in MgO content in the DVM exerted a chemical filtration to the molten slag, and the higher concentration of periclase dissolved into the slag, forming a saturated layer at the slag/refractory interface that resulted in the restriction of further slag penetration, probably due to an increase in the slag viscosity.     

除尘灰基脱磷剂的研发

 为实现除尘灰的资源化利用和铁水的有效预脱磷，尝试利用转炉二次除尘灰制备铁水脱磷剂具有现实意义。通过两种转炉二次除尘灰以不同比例替换纯脱磷剂中的有效成分进行脱磷试验，从而找到最佳的除尘灰替换比。试验结果表明，在使用除尘灰基脱磷剂后，两种脱磷剂的最高脱磷率分别达到52%和30%，脱磷终渣中P2O5活度系数明显降低，终渣磷容量显著增加，但磷分配比相对下降。另外，除尘灰基脱磷剂还具有较高的脱硅和脱硫效果，且最大脱除率均超过95%，这说明该脱磷剂能够同时实现铁水的预处理“三脱”作业，从而为除尘灰的二次利用提供了一条新的途径。     

转炉用溅渣镁球造渣技术

针对转炉炉渣MgO含量偏低的现象,对转炉使用溅渣镁球代替轻烧白云石造渣技术,合理控制溅渣镁球的加入量,达到降低终渣FeO、提高渣中MgO来迅速降低炉渣过热度等目的,从而可以缩短溅渣时间,提高溅渣层的抗侵蚀能力,最大限度发挥溅渣护炉效果,延长补炉间隔时间,节约耐火材料,提高生产作业率,并降低炼钢的冶炼成本。     

120 t顶底复吹转炉终点碳含量控制对钢水脱磷的影响

研究了120 t转炉在终点钢水平均温度1630℃,平均终渣碱度4.0时,终点[C]（0.029%~0.176%）对终点[P]和磷分配比的影响。34炉次冶炼结果表明,终点出钢磷含量随着碳含量的减小而降低,当碳含量低于0.06%时,有利于实现磷含量低于0.005%出钢;随着终点碳含量的降低,渣钢间的磷分配比增大,炉渣脱磷能力增强;在同等工艺条件下,终点碳含量越低,供氧时间越长,吹氧和碳氧反应对熔池的搅拌作用有利于进一步脱磷。     

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RH oxygen top- blowing for raising temperature should be avoided to improve the cleaniness of IF steel as far as possible, which made the end point temperature of converter higher and then dephosphorization in converter became difficult. Thermodynamics and dynamics of dephosphorization process in converter were calculated to study the relationship of phosphate partition ratio to compositions of molten steel, slag, temperature in molten steel based on slag- remaining and double slag process. Through changing the first deslagging time and the composition of slag,then serial sampling from molten steel and slag in industrial production experiments, the behavior of phosphorus in molten steel was studied and then the main measures obtaining higher phosphate partition ratio in slag- remaining and double slag process are: small- sized scrap or thin steel sheet should be used to increase FeO content in slag and prevent molten steel temperature increase when oxygen blowing in converter begins. Slag with high phosphorus content should be poured when amount of oxygen blowing reachs 40% of the total; FeO content in slag should be increased to assure the mobility of slag and then reduce rephosphorization from slag to steel when amount of oxygen blowing is greater than 40% and less than 80% of the toal; the end- point slag with 4. 0 basicity and 18 mass%-20 mass% FeO content and molten steel temperature should be controlled.     

CaO-MgO-SiO2-Al2O3类夹杂物塑性化对帘线钢加工断丝率的影响

通过分析70 t转炉流程和180 t转炉流程生产的LX72A帘线钢合股断丝率,得出中心偏析相同的条件下,当钢中脆性夹杂物比例由90.7%降至20.5%,也就是塑性夹杂物的比例由9.3%提高79.5%时,平均盘条断丝率由4.20次/t降至2.56次/t。通过采用碱度1.05不含MgO的LF精炼渣,控制钢中Als含量≤0.001%,氧含量≤22×10^-6,可有效地降低钢中脆性夹杂物含量,降低盘条断丝率。     

100t 转炉留渣双渣法冶炼高硅高磷铁水试验

针对钢厂铁水硅和磷含量较高的特点,采用转炉留渣双渣冶炼工艺以获得稳定的铁水脱磷率。吹炼3 min后加入石灰和污泥球等造渣材料,供氧强度0～3 min时为2.5m³/（t·min）,3～4.5 min时为3.2m³/（t·min）,温度控制在约1320℃。转炉一次倒渣后,继续吹炼,加入后期造渣料,待一氧化碳体积分数稳定时,适当提高氧枪枪位,促进化渣,并进行终点碳控制。试验结果表明:脱磷期铁水平均脱磷率为58.09%,脱碳期钢水平均脱磷率为85.56%;当半钢温度为1320℃炉渣碱度为2.0,炉渣TFe含量为18%时,在脱磷期能获得较好的铁水脱磷效果;当转炉钢水一倒温度为1580℃,终渣碱度为3.5,炉渣TFe含量为20%时,在脱碳期能够获得较好的脱磷效果;转炉终点[P]_e/[P]_r为0.90;试验中得到脱磷期和脱碳期炉渣的岩相组成适合铁水脱磷。     

MgO和MnO对CaO-SiO2-Fe2O3-P2O5渣的物相影响

转炉渣中的磷主要存在于n2CaO·SiO2-3CaO·P2O5（以下简记为nC2S-C3P）固溶体的富磷相中。为了深入理解转炉渣的物相,便于有效富集钢渣中的磷,研究MgO和MnO含量的变化对CaO-SiO2-Fe2O3-P2O5渣中nC2S-C3P固溶体的磷含量及渣结晶物相的影响,并对其进行热力学分析。结果表明：在CaO-SiO2-Fe2O3-P2O5四元渣系中加入少量MgO或MnO,可以在一定程度上提高nC2S-C3P固溶体中的磷含量;继续提高MgO或MnO含量,固溶体中的磷含量不再发生变化。随着MgO或MnO的加入,富铁相增多,有利于钢渣的磁选分离。     

Refractory–Slag–Metal–Inclusion Multiphase Reactions Modeling Using Computational Thermodynamics: Kinetic Model for Prediction of Inclusion Evolution in Molten Steel

The refractory–slag–metal–inclusion multiphase reaction model was developed by integrating the refractory–slag, slag–metal, and metal–inclusion elementary reactions in order to predict the evolution of inclusions during the secondary refining processes. The mass transfer coefficient in the metal and slag phase, and the mass transfer coefficient of MgO in the slag were employed in the present multiphase reactions modeling. The “Effective Equilibrium Reaction Zone (EERZ) Model” was basically employed. In this model, the reaction zone volume per unit step for metal and slag phase, which is dependent on the ‘effective reaction zone depth’ in each phase, should be defined. Thus, we evaluated the effective reaction zone depth from the mass transfer coefficient in metal and slag phase at 1873 K (1600 °C) for the desulfurization reaction which was measured in the present study. Because the dissolution rate of MgO from the refractory to slag phase is one of the key factors affecting the slag composition, the mass transfer coefficient of MgO in the ladle slag was also experimentally determined. The calculated results for the variation of the composition of slag and molten steel as a function of reaction time were in good agreement with the experimental results. The MgAl₂O₄ spinel inclusion was observed at the early to middle stage of the reaction, whereas the liquid oxide inclusion was mainly observed at the final stage of the refining reaction. The content of CaO sharply increased, and the SiO₂ content increased mildly with the increasing reaction time, while the content of Al₂O₃ in the inclusion drastically decreased. Even though there is slight difference between the calculated and measured results, the refractory–slag–metal multiphase reaction model constructed in the present study exhibited a good predictability of the inclusion evolution during ladle refining process.