MgO部分稳定氧化锆陶瓷的抗渣侵蚀性研究

分别以3.5%(质量分数,下同)MgO部分稳定或4?O部分稳定的ZrO2陶瓷材料为试样,以CaO-Fe2O3-SiO2系的3种不同碱度与Fe2O3含量的渣为侵蚀剂,对试样分别进行静态和动态旋转(试样与渣的相对速率分别为0.06和0.5 m.m in-1)侵蚀试验,研究渣的碱度、流速及Fe2O3含量对材料抗侵蚀性的影响。结果发现,MgO部分稳定ZrO2材料抗渣侵蚀性较好,试样在渣线部位较严重的侵蚀归因于Marangoni效应。试样侵蚀情况与渣的碱度、成分有密切关系,高碱度渣侵蚀的方式主要是形成新的化合物而降低试样强度,中碱度或低碱度高Fe2O3渣则先将稳定剂MgO溶出,使材料遭受侵蚀的同时还发生相变化。     

含钒渣对铝碳材料的侵蚀

为了探讨含矾渣对铝碳材料的侵蚀机制,用动态感应抗渣法研究了w(V2O5)=10%、碱度2.8,w(V2O5)=6%、碱度2.8,w(V2O5)=6%、碱度1.44的3种含钒渣对铝碳材料的侵蚀。结果表明:随着V2O5含量(w)由6%增加到10%,铝碳材料的熔损指数增加;随着碱度的增加,铝碳材料的熔损指数也增加;添加电熔镁砂有助于提高铝碳材料的抗侵蚀性能。显微分析表明:V、Ti元素渗透能力强,渗透深,而尖晶石可固溶少量V2O5、MnO及FeO。     

碳含量对MgO-C材料抗氧化性和抗渣侵蚀性的影响

以w(MgO)=98.5%的电熔镁砂和w(C)=99.3%的天然鳞片石墨为原料,酚醛树脂为结合剂,于900℃氩气气氛中炭化处理后制备了碳含量(w)分别为5%、10%、15%、20%、25%、30%的MgO-C材料,并考察碳含量对其抗氧化性(1 000、1 400℃下)和抗渣侵蚀性(1 650~1 700℃)的影响。结果表明:1)随着碳含量的增加,MgO-C试样的抗氧化性能提高;2)渣线部位试样的侵蚀量随着碳含量的增加先减少后增加,在碳含量为20%(w)时最小;钢液部位试样的侵蚀量随着碳含量的增加而增加,但当碳含量为25%(w)时急剧减少。     

ZrO_2含量对镁锆不烧砖性能的影响

以w(MgO)=97%的电熔镁砂和w(ZrO2)=14.33%的预合成电熔镁锆料为原料,以酚醛树脂为结合荆,用400 t摩擦压砖机机压成型制备了w(ZrO2)分别为0、2%、4%、6%和8%的镁锆不烧砖,研究了ZrO2含量对镁锆不烧砖的常温性能、高温强度、抗热震性的影响,同时还重点研究了其抗渣性能(采用回转抗渣法,渣为碱度3.6的精炼炉渣,侵蚀温度1 650℃),并借助SEM和EDAX分析了部分抗渣后试样的显微结构.结果表明:(1)随着引入的ZrO2含量提高,镁锆不烧砖的常温力学性能总体呈上升趋势,w(zrO2)由0增加到8%时,1 600℃3 h处理后镁锆不烧砖的高温抗折强度(1 500℃下)从0.5 MPa提高到2 MPa.(2)引入的ZrO2改善了不烧砖的抗热震性,w(ZrO2)由0增加到8%时,试样经1 000℃风冷1次后的抗折强度保持率由20%提高至70%以上.(3)ZrO2的引入可以改善镁质材料的抗渣渗透性,尤其是电熔钱锆合成料以细粉形式引入时效果更佳;但ZrO2的引入又对抗渣侵蚀性有所不利,尤其是引入w(ZrO2)达6%～8%时,会造成主晶相方镁石和c-ZrO2,的热膨胀不匹配效应加剧,使材料产生较大裂纹甚至剥落,导致抗渣渗透性随之恶化.当引入的w(ZrO2,)≤4%时,材料以侵蚀损毁为主,蚀损深度约12 mm;而w(ZrO2)>4%时,以渗透和剥落损毁为主,最高蚀损深度达到30 mm左右.因此,综合考虑,镁锆不烧砖中ZrO2,含量以4%(质量分数)为宜.     

渣的粘度和润湿性与石墨的关系

为了提高COREX(?)工艺操作中的脱硫量和改进其出渣时的渣流动性,在1400℃～1540℃的温度变化区间,测量了含CaO25%～40%、SiO_235%、MgO10%～25%和Al_2O_312%的渣的粘度,以此作为碱度[B=(%CaO+%MgO)/%SiO_2]和MgO含量的函数。在冷却状态下,由于临界温度的出现,渣粘度因固体颗粒的沉淀而突然增大。与粘度变化相关的临界温度,随MgO含量增加到20％后而降低,但此后,转而增高。在临界温度以上,粘度由于渣碱度和MgO含量(达20％)增高而降低。根据测定的最低的COREX(?)工艺操作温度,讨论了渣组成对粘度的影响。通过实验也推导出粘度、渣组成和温度之间的关系。在1550℃条件下,通过研究渣与石墨之间的润湿性,以了解在出渣期间,碳与熔渣一同排出的原因。随着炉渣碱度和MgO含量的增加,CaO-SiO_2-MgO-Al_2O_3渣系统与石墨之间的接触角略有减小,而且它们的值在非润湿性范围内。然而在同等碱度和MgO含量条件下,在给定的渣系统中添加FeO会引起接触角的显著减小。由于渣与石墨之间的化学反应以及碱度和MgO含量的增加,则会发现润湿性会极大地增强。     

铁浴式熔融还原渣对镁铬材料侵蚀的研究

以市售w(Cr2O3)=26.02%的电熔再结合镁铬砖和自制预合成的不同FeO含量的铁浴式熔融还原渣为研究对象,采用旋转圆柱法,研究了铁浴式熔融还原渣中FeO含量(其质量分数分别为0、5%、10%和15%)和试验温度(1 450、1 500、1 550和1 600℃)对镁铬砖试样侵蚀量、显微结构的影响。结果表明:(1)不含FeO的渣对镁铬试样的侵蚀量大于FeO含量(w)为5%的渣,渣中FeO含量(w)为5%~15%时,随着FeO含量的增加,镁铬试样的侵蚀量增大,侵蚀加剧;(2)温度是影响镁铬材料抗渣性能的重要因素之一,温度提高,熔融还原渣对耐火材料的侵蚀加剧。     

不同碱度渣对铝镁浇注料的侵蚀行为

以板状刚玉颗粒(≤5 mm)、电熔镁砂粉(≤0.088 mm)、电熔尖晶石粉(≤0.044 mm)、α-Al2O3微粉(d50≤0.7μm)为主要原料,经配料、混料、成型、烘干后制备了铝镁质坩埚试样,采用2种不同碱度的钢包渣(碱度分别为3.40和1.03),通过静态坩埚法对铝镁浇注料进行抗渣试验(1 600℃3 h),分析了抗渣试验后试样的渣蚀指数和显微结构,以研究不同碱度渣对铝镁浇注料试样的侵蚀行为。结果表明,低碱度渣对铝镁浇注料的侵蚀和渗透比高碱度渣严重,这主要是因为不同碱度渣与浇注料反应生成的产物不同。低碱度渣对铝镁浇注料侵蚀时,材料内部CA6和钙铝硅系化合物多相共存的组织以及CA6生成时的体积膨胀效应加剧了渣对材料的侵蚀和渗透;在高碱度渣条件下,渣与材料界面生成了CA2致密层和大量的原位MA,有效地降低了渣对材料的蚀损。     

MgO-C材料低压动态条件下抗侵蚀性的研究

采用真空感应炉浸棒法,在真空度为5 kPa,于1 650 ℃保温25 min的试验条件下研究了w(C)约为10%的MgO-C材料的抗熔渣侵蚀性;对试验后的试样进行观察与测量,并用SEM分析了侵蚀后试样显微结构.结果表明:在本试验条件下,熔渣的侵蚀速率大于MgO与C反应的脱碳速率,随着CaO-SiO<,2>渣系碱度的提高,MgO-C材料侵蚀量减少;MgO-C材料对CaO-Al<,2>O<,3>熔渣有较强的抗侵蚀性.     

炉渣组分对CaO-Al2O3-SiO2-TiO2-MgO-Na2O渣系粘度的影响

针对高碱度高氧化铝含氧化钠的CaO-Al2O3-SiO2-TiO2-MgO-Na2O六元渣系,采用有限制的混料均匀设计方法设计实验,在1773 K温度熔融还原条件下测定了该渣系的粘度. 利用偏最小二乘法回归分析,建立了炉渣组分与粘度的回归方程,利用回归方程分析了炉渣碱度[w(CaO)/w(SiO2)], MgO, TiO2, Al2O3及Na2O对炉渣粘度的影响. 结果表明,回归方程拟合的关联系数RC2为0.9945,方程可很好地预测该渣系的粘度. 在实验范围内,炉渣粘度随碱度的增加而增加. 碱度一定时,炉渣粘度随MgO, Al2O3, Na2O含量的增加而逐渐降低,随着TiO2的增加先降低后增加. 当炉渣碱度小于3.1、MgO质量含量大于4%、Al2O3大于20%、TiO2在3.1%~6.1%、Na2O大于0.75%时,1773 K温度下炉渣粘度均小于2 Pa×s,此时渣系粘度完全满足实际冶炼要求.     

渣的粘度和润滑性与石墨的关系

为了提高COREX工艺操作中的掊硫量和改进其出渣时的渣流动性,在1400℃－1540℃的温度变化区间,测量了含CaO25%-40%、SiO235%、MgO10%-25%和Al2O312%的渣的粘度,以此作为碱度[B=(?O %MgO)/%SiO2]和MgO含量的函数,在冷却状态下,由于临界温度的出现,渣粘度因固体颗粒的沉淀而突然增大。与粘度变化相关的临界温度,随MgO含量增加到20％后而降低,但此后,转而增高。在临界温度以上,粘度由于渣碱度和MgO含量（达20％）增高而降低。根据测定的最低的COREX工艺操作温度,讨论了渣组成对粘度的影响。通过实验也推导出粘度、渣组成和温度之间的关系。在1550℃条件下,通过研究渣与石黑之间的润湿性,以了解 在出渣期间,碳与熔渣一同排出的原因。随着炉渣碱度和MgO含量的增加,CaO-SiO2-MgO-Al2O3渣系统与石墨之间的接触角略有减小,而且它们的值在非润湿性范围内。然而在同等碱度和MgO含量条件下,在给定的渣系统中添加FeO会引起接触角的显著减小。由于渣与石墨之间的化学反应以及碱度和MgO含量的增加,则会发现润湿性会极大地增强。     

Wear of MgO-C Refractories in EBT Type Furnaces Experienced at Iranian Mobarakeh Steel Plant

Mobarakeh Steel Company produces 3 million tons ofsteel annually with eight 180 tons EBT furnaces. Differ-ent types of magnesia-carbon refractories have been em-ployed at slagline during last 5 years. In the present studythe wear and corrosion of MgO-C refractories of these fur-naces have been studied via post-mortem analysis of usedbricks and the observation of operational effects. Laborato-ry corrosion tests were also arranged to investigate the effectof slag chemistry and the mechanism of chemical corro-sion. Characterization of different magnesia-carbon bricksclarified that the crystal size, type and chemistry of mag-     

Effect of Metal Additives on Performance of Low-Carbon Magnesia-Carbon Materials

In this paper,both oxidation and corrosion resistance of low-carbon magnesia-carbon materials containing 4.0wt% graphite with metallic Al and Mg-Al alloy powders as antioxidants were investigated.Meanwhile,the microstructures of samples corroded by slag were observed with optical microscope as well.The test results revealed the properties of oxidation and corrosion resistance of low-carbon magnesia-carbon materials could be improved obviously by adding metal Al powder and Mg-Al alloy powder.The rule of improving oxidation resistance was illegibility when metal Al powder and Mg-Al alloy powder were added together.It was harmful to corrosion resistance by mixed adding metal Al powder and Mg-Al alloy powder into the materials,at the same time,the corrosion resistance would decreased with the increasing of Mg-Al alloy content.The corrosion resistance of samples with 0.5wt% or 3.0wt% Mg-Al alloy was better. The oxidation resistance and corrosion resistance of materials with metal Al or Mg-Al alloy respectively were better than that with mixed metal Al and Mg-Al alloy. As a result, Mg-Al alloy was more suitable for low-carbon composite materials than metal Al as additives.     

Microstructures and Corrosion Resistance of Al2O3—C Based Refractories to the Melts Containing Titania

The corrosion resisance of the Al2O3-C based refrac-tories in melts containing titania has been studied by quasi-station immersion and rotary immersionThe corrosion rate is decreased with the addition of graphite carbon and ZrO2 in the refractories.The corrosion mehanism of Al2O3-C refractories is the oxidization of graphite carbon by the oxides of the melts and the formation of deteriorate layer,For the Al2O3-C-ZrO2 refractories,the corrosion behavior is due to the interaction between melts and refrac-tories,The new compounds of FeO.SiO2,SiZrO4,Feo.3CaO,2CaO.SiO2 and CaO.SiO2 are formed in the deteriorate layer.     

Role of graphite on the corrosion resistance improvement of MgO–C bricks to MnO-rich slag

In order to clarify the effect of graphite content on the corrosion behavior of MgO–C refractories immersed in MnO-rich slag, the MgO–C refractory samples bearing 5 wt%, 10 wt% and 15 wt% graphite were prepared, and exposed in the slag composed of 40 wt% CaO, 40 wt% SiO₂ and 20 wt% MnO. The results show that metallic Mn particles and (Mg,Mn)O solid solution are formed at the slag/refractories interface. Whereas, no dense layer is formed by (Mg,Mn)O solid solution at the interface. The decrease in MnO content of slag is mainly attributed to the reaction with graphite to form liquid Mn. The graphite is found in the slag, and dissolved in the form of oxidation. The poor wetting limits the contact area of graphite and slag, reducing graphite oxidation and decarburized area. The graphite does not become the passage for slag to penetrate into the refractories due to the oxidation. On the contrary, the dissolution of MgO in slag is faster than graphite, thus is mainly responsible for the degradation of refractories. As a result, MnO and MgO contents change less in the slag contacted with the refractories bearing higher graphite content.     

电磁场作用下高铁渣对MgO-C耐火材料的侵蚀

电磁场会促使熔渣中的铁、锰离子与MgO-C耐火材料反应形成锰掺杂镁铁尖晶石相,为进一步研究锰掺杂镁铁尖晶石的生成形貌及特征,采用Fe2O3质量分数为53.62%、CaO与SiO2质量比为0.8的高铁渣,分别在有、无电磁场环境下,对碳质量分数为14%的MgO-C耐火材料进行渣蚀试验。结果表明:感应炉存在电磁场,使熔渣中部分Fe2+/Fe3+与镁砂中Mg2+发生置换形成镁铁尖晶石,其含有少量Mn2+离子;镁铁尖晶石中铁含量从渣蚀层到渗透层急剧降低,锰含量几乎维持不变;侵蚀后试样渗透层较明显。电阻炉无电磁场,则侵蚀后试样没有形成镁铁尖晶石,熔渣中Si、Ca渗透到方镁石晶格中,形成钙镁榄橄石低熔相,将镁砂溶解到熔渣中;渣蚀层有明显的MgAl2O4生成。     

Al2O3-ZrN-Sialon-C复相耐火材料抗渣侵性能研究

以板状刚玉、石墨、α-Al2O3、金属铝粉、单质硅粉为主要原料,ZrN-Sialon复相粉体为添加剂,采用酚醛树脂结合制备了Al2O3-ZrN-Sialon-C复相耐火材料.采用静态坩埚法研究了ZrN-Sialon复相粉体加入量对材料抗渣侵蚀性能的影响,借助SEM与EDS面扫描对渣蚀后材料的结构和成份进行分析,并探讨了Al2O3-ZrN-Sialon-C复相耐火材料的抗渣侵蚀机理.结果表明:ZrN-Sialon复相粉体加入量为9wt％时,材料表现突出的抗钢渣侵蚀性能.研究表明材料中Sialon氧化后生成的SiO2能形成致密的氧化保护层,同时ZrN氧化后形成的ZrO2有利于提高抗钢渣的浸润,阻止钢渣的渗透与侵蚀.分析认为Al2O3-ZrN-Sialon-C复相耐火材料的钢渣侵蚀机理为氧化-熔蚀-渗透.     

Improvement in performance of MgO–CaO refractories by addition of nano-sized ZrO2

MgO–CaO refractories added with different sized ZrO₂ powders were sintered at 1600 °C, the effect of the ZrO₂ powders on performance of MgO–CaO refractories was investigated. The results showed that the densification of the MgO–CaO refractories was appreciably promoted when a small amount of ZrO₂ was added owing to the formation of small size CaZrO₃ facilitated to sintering, and the densification was promoted further with increasing the amount of ZrO₂ due to the volume expansion caused by the reaction of the added ZrO₂ and CaO to form CaZrO₃ in the refractories, and the addition of nano-sized ZrO₂ was more effective. The thermal shock resistance of the MgO–CaO refractories was improved by modification of the microstructure due to the formed CaZrO₃ particles that predominately located on the grain boundaries and triple points in the whole microstructure, and the addition of nano-sized ZrO₂ was more effective attributed to its well dispersion and the critical addition amount was effectively decreased to 6%. The slaking resistance of the MgO–CaO refractories was appreciably improved by addition of ZrO₂ due to its effect on decreasing the amount of free CaO in the refractories, promotion of densification as well as modification of microstructure, the nano-sized ZrO₂ addition was more effective due to its higher activity. The slag corrosion resistance of the MgO–CaO refractories was enhanced by addition of ZrO₂ due to the increase of the viscosity of the liquid phase and thus inhibited further penetration of slag at elevated temperatures.     

影响镁碳耐火材料表面MgO致密层形成的因素

研究了镁碳耐火材料中镁砂原料的种类和碳含量 ,渣剂的有无及碱度 ,炉内气氛以及是否加铝脱氧等因素对镁碳耐火材料表面MgO致密层形成的影响。结果表明 :(1)在w(C) =10 %～ 2 0 %范围内 ,随着碳含量的降低 ,形成的MgO致密层越完整 ,且厚度增加 ;(2 )Mg(g)氧化形成MgO致密层的氧是由熔渣通过熔融金属提供的 ,凡是影响熔渣和熔融金属中氧活度的因素 ,都会对MgO致密层的形成产生影响 ;(3)炉内气氛对MgO致密层的形成没有明显的影响 ;(4)与电熔镁砂相比 ,使用烧结镁砂为原料时 ,耐火材料表面更容易形成MgO致密层。