稀土氧化物对连铸保护渣理化性能的影响

稀土钢浇铸过程中,稀土氧化物进入到保护渣熔融层中,影响和限制了保护渣冶金性能的正常发挥,针对这一问题,文章系统分析了稀土氧化物对结晶器保护渣不同碱度熔化温度、粘度和结晶温度的影响。结果表明,少量的稀土氧化物对保护渣有助熔作用,随稀土氧化物含量的增加,不同碱度保护渣的熔化温度、粘度和结晶温度变化显著。     

连铸保护渣的结晶性能及其模型预测

 利用差热分析仪,研究连铸保护渣的结晶温度与碱度、Na2CO3含量、CaF2含量、Al2O3含量和MgO含量之间的关系,进而通过建立非线性规划模型,对连铸保护渣的结晶性能进行优化设计和模型预测。在本实验渣系条件下,连铸保护渣的结晶温度随着碱度、综合碱度、Na2CO3含量、CaF2含量和MgO含量的增加而升高,随着Al2O3含量的增加而降低。     

Li2O对CaO-Al2O3基保护渣结晶性能的影响

摘要：高铝钢用新型CaO-Al2O3基连铸结晶器保护渣结晶性能较强，在连续浇铸过程中易出现润滑与传热功能协调不均的问题。基于此，针对新型CaO-Al2O3基保护渣，考察了典型助熔剂Li2O对保护渣析晶温度、析晶物相等性能的影响，并进行了相关结晶动力学分析。结果表明，提高Li2O含量可使保护渣的临界冷却速率和初始结晶温度呈现先降低后升高的趋势，当Li2O质量分数为4%时，保护渣结晶倾向最弱。随Li2O质量分数从0增至6%，保护渣的结晶孕育时间先延长后缩短。析晶物相由CaAl4O7+CaF2转变为CaAl4O7+CaF2+LiAlO2，Li2O的加入及其含量的提高促进了LiAlO2的析出。此外，随Li2O质量分数从0增至6%，保护渣结晶活化能先增大后减小，析晶过程受到的阻力先增强后减弱，与结晶性能的变化规律相吻合。     

BaO 含量对结晶器保护渣润滑和传热行为的影响

研究了0-6％BaO含量对包钢CSP流程浇铸Q235B、SS400等中碳钢、主要成分(％)为31．60CaO、27．20SiO2、10．48C、4．85Al₂O₃、碱度为1．16的结晶器保护渣熔化温度、析晶温度和析晶率的影响。试验结果表明,在实验渣中加入≤2％BaO,可有效地改善保护渣的润滑性能,抑制晶体析出,改善熔渣的玻璃性能;BaO含量≥4％时,完全抑制晶体析出,得到良好的玻璃态渣膜。     

B2O3在稀土钢连铸保护渣中作用机制的研究

采用正交实验设计原理设计保护渣的组成，研究B2O3对稀土钢连铸保护渣的粘度、熔化温度和组织结构的影响，提出了B2O3在稀土钢连铸保护渣中的合适含量。结果表明，B2O3可抑制熔渣中高熔晶体铈钙硅石的生成，增强保护渣吸收稀土氧化物的能力，保证保护渣吸收稀土氧化物后理化性能的稳定。B2O3含量为6％的保护渣吸收15％的RExOy后仍能保证稳定的理化性能。     

CaO-SiO2-Al2O3-Na2O-CaF2固态渣系的再结晶性能

 含铝钢连铸时,钢水中的铝与保护渣中SiO2反应导致保护渣中Al2O3含量增加而SiO2含量减少,导致保护渣的热物理性能发生变化,从而影响了铸坯的质量。在以前的研究基础上使用X射线衍射仪(XRD)和差热分析仪(DTA)以及扫描电镜(SEM)研究了高铝保护渣固态渣膜的结晶行为与晶体显微结构的变化规律。结果表明,高铝保护渣中CaF2的析出主要是因为SiO2含量的减少和Al2O3含量的增加导致大量的Ca2+的功能由电荷补偿变为网络修饰体,温度降低时CaF2首先析出;随着保护渣中Al2O3含量的增加,在同一加热速率下析晶温度升高;当保护渣中Al2O3含量较少时,析出晶体为枪晶石(Ca4Si2O7F2)和少量的CaF2,当Al2O3含量大于5%(质量分数,下同)时,霞石(NaAlSiO4)进一步析出,且随着Al2O3含量的增加,析出晶体的尺寸减小。     

Fe- Ni- Cr 系合金连铸保护渣冷却过程矿相析出热力学分析

采用 Factsage 热力学软件计算和实验室研究相结合的方法，探究碱度 ( 0. 8 ～ 1. 2 ) 、BaO 含量 ( 5% ～ 15% ) 、B₂ O₃ 含量(5% ～15% ) 对 Fe-Ni-Cr 系耐蚀合金连铸保护渣 CaO-SiO₂ -Al₂ O₃ -CaF₂ -Na₂ O-MgO 系冷却过程矿 相析出的影响 。 结果表明，当熔渣碱度由 0. 8 升高到 1. 2 时，析晶温度由1 201．7 ℃ 升高到1 256．4 ℃，硅酸盐含量 从 83. 1% 降低到 79. 6% ; 熔渣中 BaO≤10% 时，随着 BaO 含量的升高，熔渣中晶体析出会受到抑制 。当熔渣中添加 10% BaO 时，晶体析出总量降低到 61. 1 % ; 当熔渣中添加 10% B₂ O₃  时，晶体析出温度降低到1 086．7 ℃，晶体析出 量降低为 66. 3% ; B₂ O₃  含量≤10% 时，可以促进熔渣玻璃化 。 最佳碱度为 1．0，BaO 或 B₂ O₃  加入量为 10% 。     

高铝钢连铸保护渣结晶矿相的研究

 针对高铝钢浇铸过程中保护渣Al2O3含量大幅增加而导致保护渣玻璃形态恶化的问题,采用SEM和XRD分析方法对高铝钢浇铸前后保护渣的显微组织和结晶矿相进行分析,研究了不同组分对保护渣结晶性能的影响。结果表明：高铝钢连铸保护渣初始SiO2含量较高,保护渣玻璃形态较好。浇铸过程中随着保护渣Al2O3含量的增加和SiO2含量的减少,保护渣的结晶率增加,玻璃性能变差;渣中Li2O容易与F-生成LiF晶相;渣中CaF2含量较高时,容易析出CaF2晶体。     

La2O3对含B2O3无氟连铸保护渣物理性能的影响

针对含B2O3无氟保护渣抑制晶体析出的问题,研究了当保护渣碱度(CaO/SiO2)等于0.9,成分为wCaO27％～36.47％、wSiO230％ ～ 40.5％、wAl2O34％、wMgO5％、wNa2O0.8％、wLi2O％、wB2O34％时,wLa2O3从0增加到20％对无氟结晶器保护渣结晶性能及渣膜传热的影响.试验表明La2O3能够提高保护渣的渣膜厚度,提高其结晶率和结晶温度,降低熔渣的熔化温度,从而有效提高控制结晶器传热的能力.     

新型LF精炼渣深脱硫研究进展

综述了BaO,Li2O,B2O3等替代剂替代精炼渣中CaO,CaF2对脱硫性能的影响,展望了脱硫精炼渣替代剂的前景,为今后对深脱硫精炼渣的研究和应用提供依据和参考。研究结果表明:1)BaO,Li2O不仅有较好的脱硫能力,二者还能降低渣系熔点,增强精炼渣的流动性,并且使用Li2O比BaO效果要好;2)BaO加入量在5%～25%范围内较合适,Li2O在渣中的添加量小于15%较合适;3)B2O3在渣中的加入量在10%以内时可以替代CaF2,减少CaF2对炉衬的侵蚀和对环境的污染(以上为质量分数)。     

高速连铸用保护渣

论述与高速连铸密切相关的保护渣技术,指出高速连铸与常速连铸用保护渣在其物性上有较大差异。高速连铸保护渣应具有较低的粘度,较低的结晶温度,较低的软化及熔融温度、合适的碱度和较快的熔化速度。配制高速连铸保护渣时应限制CaF_2、Na_2O的加入量,适当添加BaO、B_2O_3、Li_2O、K_2O、MgO等的助熔剂是有益的。     

薄板坯连铸用保护渣

薄板坯连铸用保护渣与厚板坯连铸用保护渣在其物理性能上有较大差异。薄板坯连铸保护渣应具有较低的粘度，较低的结晶、软化及熔融温度，合适的碱度以及较快的熔化速度。配制薄板坯连铸保护渣时应限制ＣａＦ２、Ｎａ２Ｏ的加入量，适量添加ＢａＯ、Ｂ２Ｏ３、Ｌｉ２Ｏ、Ｋ２Ｏ和ＭｇＯ等助熔剂是有益的。     

Crystallization Temperature and Crystallization Ratio of Mold Flux

Moldfluxformsaliquidphaseinfiltratinginto thegapbetweenthemoldandstrand.Thelayerof fluxfilmonthemoldplateisasolidglassylayer,whilethelayerclosesttothestrandremainsliquid andacrystallizationlayerliesbetweenthistwolay ers[1-3].Thecrystallizationtemperatureo…     

无氟连铸结晶器保护渣的结晶性能

 结晶器与连铸坯间的保护渣膜直接影响着连铸坯的润滑及传热,而保护渣的结晶性能是影响润滑和传热的重要因素。通过测定保护渣的结晶温度、结晶率和结晶体几何尺寸,研究了碱度和TiO2含量对含钛无氟保护渣结晶性能的影响规律。结果表明：加大碱度和增加TiO2含量都能明显提高保护渣的结晶倾向性。     

Effects of Rare Earth Oxide on Viscosity of Mold Fluxes for Continuous Casting

The effects of RE (rare earth) oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that : (1) The viscositv of mold fluxes is remarkably inereased by RE oxide addition, especially when the mass fraction of RE oxide is more than 10%. (2) By addition of RE oxide, precipitation of the insohlble particles with high melting point from the molten slag with the decreasing of the temperature leads to the inerease of viscosity. Viscosity curve shows that RE oxide is soluble in some extent in mold fluxes. When RE oxide is in a state of supersaturation, the existence of insoluble particles also makes the viscosity of mold fluxes increase. (3) Not only the viscositv of nlold fluxes can be reduced, but also the capacity to dissolve and absorb RE oxide can be increased by Li2O, B2O3 and BaO. However, the contents of Li2O, B2O3, and BaO should be controlled to suitable levels. (4) The solidification temperature of mold fluxes can be increased by the addition of RE oxide, which is unfavorable to heat transfer and luhrication of mold fluxes between steel shell and mold.     

X-射线荧光光谱法测定炉渣中13种组分

采用Li2B4O7和LiNO3为熔剂,LiBr作脱膜剂,熔融法制备样品;运用干扰曲线法通过迭次校正Ba,Ti,V,Cr,Mn各元素谱线重叠干扰,理论α系数法校正基体效应,X-射线荧光光谱法(XRF)分析了复杂体系炉渣中Na2O,MgO,Al2O3,SiO2,P2O5,K2O,CaO,TiO2,V2O5,Cr2O3,MnO,TFe,BaO 13种组分。该方法与化学法测定结果符合较好,10次制样测量各组分,相对标准偏差在0.15%~3.79%范围内。     

Crystallization Behaviors of CaO-SiO2-Al2O3-Na2O-CaF2-(Li2O-B2O3) Mold Fluxes

The effects of basicity (CaO/SiO₂), B₂O₃, and Li₂O addition on the crystallization behaviors of lime-silica-based mold fluxes have been investigated by non-isothermal differential scanning calorimetry (DSC), field emission scanning electron microscopy, X-ray diffraction (XRD), and single hot thermocouple technique. It was found that the crystallization temperature of cuspidine increased with increasing the basicity of mold fluxes. The crystallization of wollastonite was suppressed with increasing the mold flux basicity due to the enhancement of cuspidine crystallization. The addition of B₂O₃ suppresses the crystallization of mold flux. The crystallization temperature of mold flux decreases with Li₂O addition. The size of cuspidine increases, while the number of cuspidine decreases with increasing mold flux basicity. The morphology of cuspidine in mold fluxes with lower basicity is largely dendritic. The dendritic cuspidine in mold fluxes is composed of many fine cuspidine crystals. On the contrary, in mold fluxes with higher basicity, the cuspidine crystals are larger in size with mainly faceted morphology. The crystalline phase evolution was also calculated using a thermodynamic database, and compared with the experimental results determined by DSC and XRD. The results of thermodynamic calculation of crystalline phase formation are in accordance with the results determined by DSC and XRD.     

Effect of rare earth oxides on the properties of bio-soluble alkaline earth silicate fibers

Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides(La_2O_3, Nd_2O_3 and Y_2O_3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten materials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing temperature range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.     

Viscous properties of new mould flux based on aluminate system with CeO_2 for continuous casting of RE alloyed heat resistant steel

The conventional mould fluxes can not be applied to the continuous casting of RE alloyed heat resistant steel, because severe slag-metal interface reactions occur generally in the mold. To restrain the interface reaction and improve conditions for continuous casting, a new mould flux based on aluminate system was devised. The viscous properties were investigated. Scanning electron microscopy and X-ray diffraction were applied to detect and characterize the crystalline phases in the continuous cooling process. The results showed that appropriate addition of CeO_2 could avoid the precipitation of CaO and decrease the viscosity of the mould flux. Increasing the mass ratio of CaO /Al_2O_3, especially to a value exceeding 1, could worsen the stability of the mould flux. With a content of less than 14 wt.%, Li_2O could reduce the viscosity and breaking temperature, but its effect could be weakened for the promoted precipitation of LiAlO_2. To obtain a mould flux with stable viscous properties, such as viscosity and breaking temperature, appropriate contents of CeO_2 and Li_2O should be controlled to around 10 wt.% and 14 wt.%, while the mass ratio of CaO /Al_2O_3 should not be more than 1.