Effect of B_2O_3 on Melting Temperature of CaO-Based Ladle Refining Slag

B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency.The effects of B2O3 on the melting temperature of two series of refining slags including the low basicity slags(the mass ratio of CaO/SiO2 is 3-4)and the high basicity slags(the mass ratio of CaO/SiO2 is 5-8.75)were investigated.The slag melting temperature was measured using the hemisphere method.The results indicate that the fluxing action of B2O3 is better than that of CaF2 and Al2O3.For the CaO-based refining slag with low basicity,the melting temperature is decreased effectively when B2O3 is used to substitute for equal mass of CaF2,Al2O3 and SiO2,respectively.For the CaO-based refining slag with high basicity,when CaF2 is substituted by B2O3,the melting temperature can be decreased remarkably.Especially,when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in the range of 1.1-4.0 and 5.25-8.0,respectively,the slag melting temperature is lower than 1300 ℃.Therefore,the B2O3-containing refining slags with high ratios of CaO/Al2O3 and CaO/SiO2 have ultra low melting temperature.     

Characteristics and Metallurgical Effects of Medium Basicity Refining Slag on Low Melting Temperature Inclusions

Recently,large sized CaO-Al2O3 inclusions with low melting temperature have been the main reason for lowering mechanical properties of high strength low alloy(HSLA)steel plates.New philosophy,i.e.refining by top slag with relatively low basicity and Al2O3 content,was proposed to control such kind of inclusions.Firstly,the characteristics of refining slag,such as component activities and sulphide capacity(CS)of CaO-Al2O3-SiO2-MgO slag,were studied through thermodynamic calculation.Then,slag-metal equilibrium experiments were carried out in laboratory to investigate the exact chemical composition of refining slag together with thermodynamic analysis.Finally,industrial trials were done to verify the desulphurization ability and inclusions control in steel refined by the new slag.Thermodynamic calculations indicated that the slags with basicity of 3.5and Al2O3 content of 20%and basicity of 5.0and Al2O3 content of 20% or 25% have high values of CaO activity,sulphide capacity and ratio of MgO activity to Al2O3 activity.Laboratory equilibrium experiments showed that the slag with basicity of about 4.5and Al2O3 content of about 20%is helpful for increasing the melting temperature of inclusions in steel.After introducing such kind of refining slag in industrial trials,the sulphur content in eight heats of steel is below 20×10-6,which meets the requirement of HSLA steel,and most inclusions distribute in relatively high melting zone(≥1 773K)of CaOAl2O3-MgO(-SiO2)quasi-ternary diagram.New philosophy of top refining slag is feasible to control low melting point inclusions of CaO-Al2O3 system in HSLA steel.     

Properties of High Basicity Mold Fluxes for Peritectic Steel Slab Casting

 In high speed continuous casting of peritectic steel slabs, mold fluxes with high basicity are required for less surface defect product. However, the basicity of remaining liquid slag film tends to decrease in casting process because of the crystallization of 3CaO·2SiO2·CaF2. Thus, a way is put forward to improve mold fluxes′ properties by raising the original basicity. In order to confirm the possibility of this method, the effect of rising original basicity on the properties of mold fluxes is discussed. Properties of high fluorine based mold fluxes with different basicities and contents of CaF2, Na2O, and MgO were measured, respectively. Then, properties of higher basicity mold fluxes were discussed and compared with traditional ones. The results show that increasing the basicity index can improve the melting and flow property of mold fluxes. With the increasing basicity, crystallization rate of mold fluxes increases obviously and crystallization temperature tends to decrease when the basicity exceeds 1.35. The method presented before is proved as a potential way to resolve the contradiction between horizontal heat transfer controlling and solidified shell lubricating for peritectic steel slab casting. But further study on improving the flow property of liquid slag is needed. This work can be used to guide mold fluxes design for high speed continuous casting of peritectic steel slabs.     

Effect of lanthanum content on microstructure and magnetic properties of non-oriented electrical steels

The effect of lanthanum content in the range of 0-0.011 wt.%,on the inclusion size distribution,microstructure,texture and magnetic properties of three non-oriented electrical steels was studied.After final annealing,lanthanum effectively inhibited the precipitation of MnS precipitates in steel,the formations of La2O2S and LaS inclusions not only acted as nuclei of AlN precipitates,but also combined with Al2O3 and formed composite inclusions with larger size.Grain size firstly increased and then decreased with lanthanum content increasing.Steel containing 0.0066 wt.% lanthanum obtained the largest grain size,the strongest {110}<110> texture and the weakest {112}<110> texture among all the tested steels.Magnetic flux density firstly increased and then decreased,core loss firstly dramatically decreased and then slightly decreased with lanthanum content increasing.Among the three tested steels,steel with 0.0066 wt.% lanthanum demonstrated the best comprehensive magnetic properties mainly through the development of favorable texture and appropriate final grain size.     

Titanium Content Control for Bearing Steel

On the basis of the thermodynamic analysis and fundamental study in the laboratory, the equilibrium of the Ti A10 system was investigated. The results showed that the equilibrium titanium content in the steel increased with the increase in the soluble aluminum content in the steel and the TiO2 content in the slag. Although the slag basicity decreased and Al2O3 content in the slag increased, the titanium content increased. Based on these results, the BOF smelting process of low titanium bearing steel was put forward.     

Viscosities Behavior of CaO-SiO2-MgO-Al2O3 Slag With Low Mass Ratio of CaO to SiO2 and Wide Range of Al2O3 Content

 The present paper is aimed at recycling of coal ash and blast furnace slag to produce mineral wool. Considering the mineralogical constitutions of coal ash and blast furnace slag, the primary quaternary slag compositions of CaO-SiO2-MgO-Al2O3 with basicity (mass ratio of CaO to SiO2) ranging from 05 to 09 and alumina ranging from 5% to 20% were investigated through a rotating cylinder method. The experimental results indicated that the viscosities decreased with increasing basicity above the liquidus temperature, and increased with increasing alumina content, and the maximum values were reached and as the alumina content was 20%, followed by the decrease with further increasing alumina content due to its amphoteric behavior. The amphoteric behavior of Al2O3 also performed in the relationship between viscosity and non-bridging oxygen per tetrahedrally-coordinated atom (NBO/T), and the viscosities decreased with increasing the NBO/T except the slag with a basicity 05 and Al2O3 20% which have a low NBO/T value and a low viscosity than others.-     

Influence of La2O3 on crystallization behavior of free-fluoride mould flux and heat transfer of slag films

In order to research the influence of La2O3 on crystallization behavior of free-fluoride mould flux and the heat transfer of slag film,free-fluoride mould flux with various La2O3 content were investigated by using self-made mould simulator,comprehensive thermal analyzer and SEM-EDS.With the increase of La2O3 content from 0% to 20%,the crystallization ratios of mould flux films were improved from 2% to 90% and the thicknesses of films were also enhanced over two times.Moreover,crystallization temperature was greatly raised and its increasing extent reached 100 oC.It could also decrease the melting temperature of casting powder about 50 oC.However,the undissolved La2O3 particles appeared in slag film if the ratio of La2O3 in free-fluoride mould flux was much too high.     

Behavior of Mold Slag Used for 20Mn23Al Nonmagnetic Steel During Casting

 Because of the addition of signi&#64257;cant quantities of Al and Mn, the great challenge of casting 20Mn23Al non-magnetic steel is to design a mold slag that is chemically compatible with this steel chemistry. In this paper, a new mold slag with low melting point, low basicity was proposed. The initial slag (the base mold slag) and two corresponding spent mold slag (8min slag and 15min slag), which was sampled from the caster after 8 minutes and 15minutes of casting, were investigated, the changes of mold slag composition and properties of molten slag were discussed. The results showed that:(i) The slag quickly changed in chemistry to a slag that contained a low quantity of silica and a higher quantity of alumina, and the basicity increased obviously; (ii) Heat flux density through the slag film decreased appreciably with the time increase; (iii) Mold slag used for non-magnetic steel precipitated CaF2 crystals; (iv) The slab has good surface quality with not occurrences of longitudinal face cracks and slag inclusions; (v) The Al2O3 content in the molten slag pool increased with time, and Al2O3 concentration of the pool can be regarded as being in a practically equilibrium state after about 600sec.     

Structural and superconducting properties in Y0.6Gd0.4Ba2（Nb）Cu3O7-y cuprates doped with niobium

Polycrystalline YBa2Cu3O7-y (YBCO) and Y0.6Gd0.4Ba2-xNbxCu3O7-y (YGBNCO) compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference (XRD) and scanning electron microscopy (SEM). The transport properties were measured by the (FPP) method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature Tconset increased slowly with x≤0.125, and then it remained unchanged or slowly decreased with 0.125≤x≤0.225. It could be found that there was a slow decrease of zero-resistance temperature, Tcoffset, with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.     

Characterization of SPEEK/Y2O3 proton exchange membrane treated with high magnetic field

The membranes of sulfonated poly(etheretherketone) of 48.3% sulfonation degree doped with Y2O3 were prepared, and then treated with parallel high magnetic field of 6 and 12 T at 120 oC for 4 h, respectively. The small-angle X-ray scattering revealed that the struc- ture of the composite membranes would be changed by high magnetic field treatment. The cross-section morphology of the composite membranes by a scanning electron microscope showed that the Y2O3 could be dispersed evenly in the composite membranes which were relatively smooth and compact but formed small conglomeration with increasing Y2O3 content and treating high magnetic field. The water uptake of membranes would be reduced with Y2O3 content increasing, but not be modified by the treatment of high magnetic field. The proton conductivity of membranes would be increased with temperature rising from 20 to 60 oC, and improved under high magnetic field, which could all exceed 10-2 S/cm at 75% relative humidity, but decrease with doping content of Y2O3 from 2 wt.% to 8 wt.%. The methanol permeability of the composite membranes would be decreased with Y2O3 content increasing and slightly reduced after high magnetic field treatment.     

中性气氛下高铝中钛型高炉渣黏度的试验研究

采用RTW熔体物性测定仪研究了中性气氛条件下高铝中钛型高炉渣的黏度和熔化性温度,得到了碱度和化学成分等因素对其黏度和熔化性温度的影响规律。结果表明:在中性气氛条件下,当炉渣碱度从0.92提高到1.12时,炉渣的黏度降低、熔化性温度升高;随着渣中MgO含量的升高,炉渣的黏度先降低再升高;增加渣中Al2O3含量,炉渣的黏度显著提高。当Al2O3的质量分数大于14.75%后对炉渣黏度的影响不明显;当TiO2的质量分数在10.57%～14.57%范围内增加时,高铝中钛渣的黏度随之降低,即在理想条件下,TiO2含量和温度的增加对炉渣黏度影响均不大。但当高炉冶炼钒钛磁铁矿时,炉渣中的Ti(C,N)等高熔点物质随原料中TiO2含量的增加和炉温的上升而增加,将对炉渣黏度产生很大的影响,故冶炼时应控制高炉内TiO2的还原以少生成高熔点钛化合物,并且严格控制铁水温度以使高炉接受矿石钛含量。     

钒钛高炉渣的流动性

依据承德建龙特殊钢有限公司当前的高炉冶炼情况,以钢厂渣为基准,利用黏度测试装置,分析了钒钛高炉渣的碱度、w(TiO_2)、w(MgO)对高炉渣黏度与熔化性温度的影响。研究结果表明:随高炉渣碱度提高,黏度和熔化性温度先降低,碱度继续提高到1.25时,炉渣黏度与熔化性温度迅速提高;随着高炉渣中w(TiO2)提高,黏度和熔化性温度呈先降低后升高的趋势;w(MgO)提高利于降低炉渣熔化性温度,不同w(MgO)情况下,炉渣熔化性温度最高为1297℃。碱度为1.15~1.20,w(TiO_2)小于10%,w(MgO)在12%~14%时,钒钛炉渣流动性较优。     

高钛型高炉渣熔化性温度影响因素

针对增加钒钛磁铁矿使用比例渣中TiO2质量分数提高后,对二元碱度以及MgO、TiO2和Al2O3质量分数等对高钛型高炉渣熔化性温度的影响进行了分析。结果表明,在二元碱度为0.9~1.3、MgO质量分数为7.00%~13.00%、TiO2质量分数为21.00%~25.00%、Al2O3质量分数为13.00%~16.00%、其他组? 槐涞奶跫拢孀哦疃取gO质量分数升高,熔化性温度升高;随着TiO2质量分数升高,熔化性温度先升高后降低;随着Al2O3质量分数升高,炉渣熔化性温度降低。二元碱度可以在较大范围内变化,对炉渣熔化性温度的调控作用最明显;MgO、TiO2和Al2O3的质量分数只能在较小的范围内变化,对炉渣熔化性影响不显著。在渣中TiO2质量分数为21.00%~25.00%的条件下,炉渣二元碱度不宜超过1.15,三元碱度不宜超过1.60,否则炉渣熔化性温度将显著升高。     

京唐高炉渣性能评价及低镁渣性能分析

结合京唐高炉的生产实际,通过对京唐现场炉渣的取样和实验室分析,对京唐高炉渣的冶金性能进行评价,其炉渣的热稳定性及流动性均符合高炉冶炼要求。通过黏度试验研究,考察Al2O3以及二元碱度对低镁条件下炉渣黏度和熔化性温度的影响。试验结果表明,炉渣黏度随渣中Al2O3质量分数的增加而升高,随二元碱度的增加呈先降低后增加的趋势;炉渣的熔化性温度随渣中Al2O3质量分数和二元碱度的增加而升高;为保证低镁炉渣具有良好的流动性,当炉渣中MgO的质量分数保持为4.0%时,二元碱度可控制为1.19左右,Al2O3的质量分数控制为16%以下。     

邯 钢 高 炉 渣 的 熔 化 性 能

 根据邯钢目前高炉的冶炼条件,以现场渣为基准,研究了炉渣碱度、MgO、Al2O3和TiO2含量对炉渣熔化性能的影响。结果表明,随碱度增加,炉渣粘度和熔化性温度先下降后提高。较高的MgO含量可降低炉渣粘度和熔化性温度,提高炉渣流动性。随渣中Al2O3含量增加,炉渣流动性变差。渣中TiO2含量对炉渣粘度和熔化性温度影响不明显。本试验条件下,合理的炉渣组成为：二元碱度为110~115,MgO含量为1119%左右,Al2O3含量为1439%左右,TiO2含量可根据现场原料变化情况而定。     

高炉高铝低钛渣的熔化性

在Al2O3的质量分数为15.14%~18.14%,TiO2的质量分数为2%~5%的范围内研究了普通高炉渣的熔化特性。应用正交试验方法,以水钢现场高炉渣为主要原料,适当配加分析纯的Ca(OH)2、MgO、SiO2、Al2O3和TiO2化学试剂调整炉渣的组成成分,采用炉渣熔化特性测试仪半球点法测定炉渣的熔化温度。试验结果表明:渣中碱度和Al2O3含量增加,炉渣熔化性温度升高;TiO2含量增加,炉渣的熔化性温度明显下降;适当提高渣中TiO2和MgO含量可避免因Al2O3含量升高而引起的熔化性温度上升;炉渣的熔化性温度在1 320~1 400℃之间,熔化性良好。     

鞍钢高炉炉渣粘度的研究与优化

在试验室对鞍钢高炉炉渣粘度进行了系统的研究与优化，选取高炉生产中的实际渣样作为实验基础渣样，以CaO、SiO2、Al2O3、MgO含量和二元碱度(R2)为因素，采用只改变某一因素，固定其他因素的交叉因素法，配制出不同碱度、不同MgO含量和不同Al2O3含量的渣样，分别进行粘度和熔化性温度的测定。结果表明：鞍钢高炉炉渣的最佳碱度R2应该在1.05～1.10，MgO含量在8％～10％，Al2O3含量小于14％。     

高炉炉缸区钒氧化物的还原试验

炉缸区钒氧化物的还原对钒的收得率具有重要影响。通过研究炉渣成分和温度对钒氧化物还原的影响,结果表明:二元碱度对钒氧化物还原影响显著,钒氧化物的还原率随着二元碱度的增加而增加;MgO、Al_2O_3含量增加,钒氧化物的还原率先升高后降低;TiO_2含量增加,钒氧化物的还原率降低,且TiO_2含量超过11%时钒氧化物的还原率大幅降低;钒氧化物的还原率随着温度的增加而升高。当承钢高炉渣的二元碱度1.2、Al_2O_3含量14%、MgO含量10%、TiO_2含量9%、炉渣温度控制1 500℃时,钒氧化物的还原达到最佳,还原率达到90%左右。     

高炉渣微观结构对其冶金性能的影响

高炉渣属于多元硅酸盐体系,在高温状态下处于熔融状态,在一定状态下物质的微观结构决定了其宏观性质。综述了高炉渣微观结构的研究现状,并分析了其对炉渣流动性和脱硫能力的影响。高炉渣化学组分主要分为网络形成子与修饰子,网络结构主要由硅氧四面体构成。CaO和MgO为网络修饰子,增加其含量,可使炉渣中自由氧离子浓度提高,降低炉渣中复杂阴离子的聚合度,破坏硅酸盐网络结构,从而炉渣黏度降低;但是碱度或MgO含量过高,也会导致炉渣中高熔点矿物增加,炉渣黏度增大。Al_2O_3、TiO_2根据其含量不同在炉渣中起的作用不同。在一定的含量范围内,Al_2O_3和TiO_2为网络修饰子,起到降低炉渣黏度的作用;随着Al_2O_3和TiO_2含量的增加,两者均会成为网络形成子,使炉渣的黏度增大,流动性变差。随着炉渣碱度或MgO含量的增加,炉渣中复杂离子团受到破坏,炉渣脱硫反应得到提高;但其含量过高时,高熔点物质增多,炉渣流动性变差,脱硫能力降低。通过深入研究高炉渣微观结构,可以更好地理解炉渣化学成分和冶金性能之间的关系,为确定合理的造渣制度提供理论依据。     

高铝钢包渣粘度的计算研究

利用Factsage软件和修正后的Einstein-Roscoe公式计算了高铝钢包渣CaO-SiO2-MgO-Al2O3体系的粘度及相图。计算研究了碱度(R=CaO/SiO2)、MgO含量和Al2O3含量对钢包渣粘度的影响,结合炉渣结构理论对其进行了解释。研究结果表明,在高铝钢包渣中,提高碱度可以降低钢包渣的粘度;在R=1.9时MgO含量增加会增大钢包渣的粘度,R=3时MgO含量增加对粘度影响较小;在碱度大于2时,粘度随Al2O3含量的增加呈现先降低后升高的趋势。要使钢包渣获得良好的流动性,需要控制渣的成分:当Al2O3含量在20 wt%~30 wt%范围,碱度R可控制在3~4之间;当Al2O3含量大于30 wt%、碱度R应大于4。