Phase Equilibrium of the System CaO‐P2O5‐SiO2 between 1473 K and 1673 K

Phase equilibrium was investigated in the ternary system of CaO‐P₂O₅‐SiO₂ at 1473K, 1573K and 1673K.     

Electrochemical Measurements of Oxygen Potentials in the Slag System CaO‐P2O5‐SiO2‐FexO

The liquidus compositions of the four‐phase assemblages in the quaternary system of CaO‐P₂O₅‐SiO₂‐Fe_xO were determined at 1473 and 1573 K by employing electron probe microanalysis. Measurements were also made on the Fe_xO activities at temperatures between 1373K and 1699K by employing an electrochemical technique involving stabilized zirconia electrolyte.     

固体CaO在3CaO·P_2O_5-2CaO·SiO_2饱和熔渣中的溶解及反应机理

为了深入了解非均相脱磷剂中固体CaO在3CaO·P_2O_5-2CaO·SiO_2(C_2S-C_3P)饱和熔渣中的溶解及反应机理,采用静态浸入法和旋转圆柱法研究固体CaO在C_2S-C_3P饱和CaO-SiO_2-Fe_tO-P_2O_5(10%)渣中的溶解行为,运用FESEM/BSED-EDS对固体CaO和熔渣界面进行了观察,分析了固体CaO与C_2S-C_3P饱和熔渣间的反应机理。结果表明,加强对熔池的搅拌,能够加快固体CaO在熔渣中的侵蚀速度和溶解速度;发现了固体CaO在饱和熔渣中的溶解数量受熔渣中FeO通过边界层向固体内部渗透深度的影响,FeO渗透深度越深,溶解越多;固体CaO先与熔渣中的硅和磷反应生成磷含量低的C_2S-C_3P固溶体,待一段时间后,最终生成磷含量高的Ca_5(PO_4)_2SiO_4。     

CaO-SiO_2-FeO-P_2O_5-Al_2O_3脱磷渣系中组元活度的计算

2CaO·SiO_2-3CaO·P_2O_5含磷固溶体的生成可提高转炉液相渣的脱磷能力,减少渣量.但目前CaO-SiO_2-FeO-P_2O_5-Al_2O_3渣系中各组元活度的变化规律尚不明确,无法为分析含磷固溶体的形成机理提供理论依据.为此,本文依据分子离子共存理论建立了熔渣组元的活度模型,分析了不同条件下组元活度的变化规律.结果表明:随渣中Al_2O_3含量的增加,2CaO·SiO_2、3CaO·P_2O_5、3FeO·P_2O_5的活度逐渐降低;随着碱度的增大,3CaO·P_2O_5的活度升高,2CaO·SiO_2、3FeO·P_2O_5的活度则呈先升高后降低的趋势;随着渣中FeO含量的增加,2CaO·SiO_2、3FeO·P_2O_5及CaO·Al_2O_3的活度逐渐增大,并在w(FeO)为15%时达到最大值,之后逐渐降低;升高温度会导致CaO、3CaO·SiO_2的活度增大,2CaO·SiO_2的活度降低.     

Evaluation and Control of Iron and Steelmaking Slags through Electrochemical FeO Sensor

One of the greatest obstacles to the application of physical chemistry principles to the elucidation of slag‐metal reactions is a lack of knowledge of activities of the reacting species. To a large extent, oxygen potential of the slag phase governs iron and steelmaking practice. Without oxygen control by means of appropriate sensors, the behaviour of the other elements cannot be managed. In this paper, measurements of the FeO activity with various types of electrochemical FeO sensors will be described together with examples of their applications for improved strategies toward better practice for ladle metallurgy and sulphur and manganese distributions between slag and metal phases during steelmaking. Measurements of FeO activity have also been made in order to improve dephosphorization reactions. This type of work has led to significant reduction in volume of slag generated within the steelmaking vessel, which in turn, has important implications for refractory wear, metal yield, alloy recovery and improved productivity. Finally an on‐line sensor is described which permits the oxygen potential to be determined for both the metal phase and the slag phase during steelmaking in the BOF.     

CaO—SiO2—Na2O三元渣系的挥发率

采用失重法对ＣａＯ－ＳｉＯ２－Ｎａ２Ｏ三元渣系在不同温度下的挥发率进行了测量。结果表明，在烧结温度下，低熔点渣的挥发率呈三段式变化，而高熔点渣无此特性；当修正碱度Ｒ′＞１、成分固定时，只有在温度超过其流动温度时才能显著提高挥发率；温度一定时，挥发率随着碱度Ｒ及Ｎａ２ＣＯ３含量的增加而提高；当Ｒ′＜１时，温度、碱度、Ｎａ２ＣＯ３含量对挥发率的影响都不大。     

改变钙系脱磷剂熔渣组成对脱磷的影响

对预处理CaO-Fe2O3-CaF2系脱磷熔剂进行实验研究,变化渣系中CaO、Fe2O3和CaF2之间的比例,并在脱磷剂中分别配加Al2O3和Na2CO3,从而不同程度提高了脱磷率。实验结果表明：熔剂脱磷率随m(CaF2)／m(Fe2O3)(钙氧比)的增大而增大;用Al2O3部分替代CaF2,终点钢中ω(P)可以控制在0．003％-0．006％的水平,脱磷率高达90％以上。     

磷在脱磷渣中2CaO·SiO2固相颗粒内的扩散速率

中国铁矿磷含量偏高,提高脱磷效率、降低渣料的消耗量对钢铁企业至关重要.1 400℃下,将2CaO·SiO2颗粒插入到含P2 O5为14％(质量分数)的渣中,并保温20、30、60和100 s,研究磷在2CaO· SiO2颗粒中的扩散速率.用SEM-EDS对磷在渣和2CaO·SiO颗粒中的分布进行了测量,并用菲克第二定律计算了磷在2CaO·SiO颗粒中的扩散系数.结果显示:磷在2CaO·SiO中的扩散可视为一维半无限扩散.1 400℃时,磷在2CaO· SiO2颗粒中的扩散系数为6.417×10-12 m2/s,如果脱磷时间为15～20 min,则2CaO· SiO2颗粒不宜大于653 μm.     

CaO-SiO_2-FeO-P_2O_5渣系脱磷影响因素的研究

为了提高转炉渣中CaO的利用率,降低转炉渣的碱度,通过试验研究了CaO粒度、粒状CaO的加入比例、温度和保温时间对含磷富集相的影响。结果表明,适当增大CaO的粒度有利于2CaO·SiO2-3CaO·P2O5固溶体的形成;当渣中粒状CaO的含量较低时,增加粒状CaO的加入比例,可促进渣中大颗粒固溶体的形成并减少渣中磷的含量,但当粒状CaO的含量较高时,2CaO·SiO2-3CaO·P2O5固溶体生成量减少;适当提高温度有利于脱磷反应的进行;随反应时间的延长,2CaO·SiO2-3CaO·P2O5固溶体的粒径增大,而且固溶体中磷的含量也不断增加。     

低氧分压条件下CaO-SiO_2-P_2O_5(10%)-FeO体系热力学性质的研究

以促进2CaO·SiO_2-3CaO·P_2O_5固溶体生成的非均相脱磷工艺被视为未来实现转炉少渣冶炼的重要手段,但目前相关渣系热力学性质的研究较少,不能为合理解释非均相渣脱磷的机理提供理论依据.为此,本文利用FactSage热力学软件绘制了低氧分压(1mPa)条件下CaO-SiO_2-P_2O_5(10%)-FeO体系及其子体系的热力学相图,分析了不同温度下相平衡关系及液相线的变化规律.研究结果表明:升高温度可使体系中液相区及Ca_3(PO_4)_2初晶区的范围扩大,但会导致α'-Ca_2SiO_4的初晶区缩小以及Ca_2Fe_2O_5等物相的消失;降低氧分压可使体系的液相区缩小,并向高FeO的方向收缩;CaO-SiO_2-P_2O_5(10%)-FeO体系中存在较大的α'-Ca_2SiO_4与Ca_3(PO_4)_2共存区,尤其是α'-Ca_2SiO_4,Ca_3(PO_4)_2与Ca_2Fe_2O_5的三相共存区可极大地促进2CaO·SiO_2-3CaO·P_2O_5固溶体的生成.     

CaF2和B2O3对中碳钢连铸结晶器保护渣物理性能的影响

用B₂O₃作为含氟渣中CaF2的替代熔剂,在保证两结晶器保护渣具有相近粘度和熔化温度的基础上,研究了成分为(%):31.1～35.5CaO、33.9～38.5SiO₂、12Al₂O₃、3MgO、5Na₂O、6～15CaF₂的含氟结晶器保护渣和(%):33.5～35.5CaO、36.5～39.5SiO₂、4Al₂O₃、5MgO、8～15Na₂O、2Li₂O、2～6B₂O₃的无氟结晶器保护渣的结晶温度、结晶能力以及对结晶器控制传热的影响。结果表明,8Na₂O-6B₂O₃无氟渣与5Na₂O-15CaF₂的含氟渣有相近的粘度和熔化温度,并对结晶器控制传热有相似的作用。      

CaO-SiO2-Al2O3-Fe2O3渣系脱磷行为

利用Factsage软件计算了Al2O3含量对CaO-SiO2-Al2O3-Fe2O3四元渣系熔点和黏度的影响,并通过实验研究了在1 400℃时,CaO-SiO2-Al2O3-Fe2O3四元渣系对高磷铁水脱磷行为的影响.结果表明:渣中Al2O3的质量分数在3％～6％之间时,随着A12O3含量的增加,渣系的熔化温度迅速降低,进一步增加渣中的A12O3含量,渣系的熔化温度逐渐增加;Al2O3对CaO-SiO2-Al2O3-Fe2O3渣系的黏度影响不大;渣中Al2O3的质量分数在3％～6％之间变化时,渣系脱磷能力变化不是很大,脱磷率维持在91％左右,进一步增加渣系中A12O3的量,脱磷率逐渐下降;Al2O3对脱磷率产生影响可能是其改变了炉渣中液相所占比例,进而影响磷从铁水中向液相渣的传质过程.     

含Ce2O3锰铁脱磷渣系熔化性质及黏度

 采用立式管式炉制备得到含Ce2O3锰铁脱磷渣系,分别利用HCT-2综合热分析仪和RTW-10型熔体物性仪对渣系的熔化性质和黏度进行测试分析。研究表明,碱度为1.05时,渣系的开始熔化温度和完全熔化温度随[w(Ce2O3)]的增加而升高,其最大值分别为1 121.6和1 282.1 ℃;碱度为0.97时,渣系的开始熔化温度和完全熔化温度随[w(Ce2O3)]的增加出现先降低后升高的趋势,当[w(Ce2O3)]为3时出现最小值,分别为1 008.8和1 148.5 ℃。渣系的黏度值随[w(Ce2O3)]的增加先降低后升高,当[w(Ce2O3)]为3%时,黏度值最小。在碱度为1.05和0.97的脱磷渣系中,黏度最小值分别为0.378和0.308 Pa·s。因此,[w(Ce2O3)]为3%时的锰铁脱磷渣系具有良好的熔化及流动特性。     

12CaO·7Al2O3炉渣与合金钢液的反应

 12CaO·7Al2O3炉渣组成为w(SiO2)=6%,w(Al2O3)=46%,w(CaO)=48%,与合金结构钢钢液进行了实验室试验。结果表明,该渣具有很高的碱度,90 min反应结束后钢中w(TO)=0000 6%~0001 3%,w(S)=0000 4%~0001 0%。同时得出为控制钢中总氧含量应将炉渣碱度控制在9左右,钢中生成的夹杂物大都是低熔点、球状、尺寸很小的钙镁铝硅酸盐类夹杂物,这类夹杂物能够避免钢材产生各向异性,并且在轧制时能够稍许变形,能够提高钢材的抗疲劳性能。     

X-射线荧光光谱法测定磷矿中五氧化二磷、氧化钙、三氧化二铁、氧化铝、氧化镁和二氧化硅

采用四硼酸锂和偏硼酸锂混合熔剂[m(Li2B4O7)∶m(LiBO2)=12∶22]熔融磷矿样品制成玻璃样片,用波长色散X-射线荧光光谱仪测定样片中P2O5,CaO,Fe2O3,Al2O3,MgO和SiO2含量。用磷矿标样经同法测定并对测定结果进行理论α系数校正后绘制工作曲线。用本法对一试样测定11次,得到各组分的相对标准偏差小于1.2%。本法已用于磷矿样品分析,测定结果与化学法一致。     

Vacuum Treatment for Simultaneous Desulphurization and Dephosphorization of Hot Metal and Molten Steel

The vacuum treatment for simultaneous desulphurization and dephosphorization of hot metal and molten steel with pre-melted CaO-based slag was carried out. For pre-treatment of hot metal, both desulphurization and dephosphorization are improved with the increase of CaO in slag, but deteriorated with the increase of CaF2 in slag. The average desulphurization and dephosphorization rate is 68.83% and 78.46 %, respectively. For molten steel, the sub-stitution of BaO for CaO in slag has minor effect on simultaneous desulphurization and dephosphorization. The desulphurization and dephosphorization rate is higher than 90 % and 50% respectively with the lowest final sulfur and phosphorus mass percent being 0. 001 2 % and 0. 010%, respectively. The overall effect of simultaneous desulphurization and dephosphorization of molten steel is better than that of hot metal.