α-Al2O3微粉对刚玉-尖晶石浇注料性能的影响

以优质白刚玉、高纯富铝尖晶石和α-Al2O3微粉(d50为4.596μm和2.148μm)为主要原料制备了刚玉-尖晶石浇注料,研究了α-Al2O3微粉加入量(质量分数分别为8%、12%和16%)对刚玉-尖晶石浇注料性能的影响。结果表明:1)随α-Al2O3微粉加入量增加,浇注料基质的流动性能提高;α-Al2O3微粉粒度较细时基质的流动性较好,而α-Al2O3微粉较粗时基质的流动性变差。2)增加α-Al2O3微粉加入量,刚玉-尖晶石浇注料的密度增加,强度明显提高,抗渣侵蚀性和抗渣渗透性明显改善,但α-Al2O3微粉加入过多时其抗热震性变差。α-Al2O3微粉的合适加入量为12%。3)与钢包渣相比,LF渣对刚玉-尖晶石浇注料的侵蚀性较大。4)采用优质电熔白刚玉、电熔尖晶石和α-Al2O3微粉,能够生产出性能优良的刚玉-尖晶石浇注料。     

鱼雷罐用Al2O3-SiC喷射浇注料的研制和应用

以高纯莫来石、碳化硅、SiO2微粉、Al2O3微粉、纯铝酸钙水泥和白刚玉细粉等为原料,研究了SiO2微粉、Al2O3微粉加入量对喷射浇注料性能的影响,并比较了铝酸钠、氯化钙、聚合氯化铝、聚丙烯酰胺 4 种促凝剂对喷射浇注料的促凝效果,同时还对比了该浇注料的浇注施工体与喷射施工体的性能差异.结果表明:加入8%的SiO2微粉和4%的Al2O3微粉,对提高Al2O3-SiC喷射浇注料的施工性能和使用性能有利;以聚丙烯酰胺为促凝剂对Al2O3-SiC喷射浇注料有较好的促凝效果.通过数次在鱼雷罐上的喷补使用证明,研制的喷射浇注料施工性能好,使用性能优异,大大提高了鱼雷罐的使用寿命.     

不同基质组成的刚玉-尖晶石浇注料性能研究

以板状刚玉、电熔尖晶石和铝酸钙水泥为原料,设计了尖晶石细粉质量分数分别为0、7.5%、15%和22.5%的4组浇注料,每组浇注料又依水泥量的不同设计了m(CaO)/m(Al2O3)分别为0.03、0.06、0.09、0.15、0.18的5个配方,制备了不同基质组成的刚玉-尖晶石浇注料试样,系统研究了试样经1 600℃3 h处理后的性能(尤其是高温抗折强度和抗热震性)及基质显微结构。结果表明:1)高温下尖晶石与基质中的Al2O3发生固溶而影响浇注料的高温强度,加入7.5%~15%质量分数的尖晶石细粉时,基质中的Al2O3与尖晶石固溶程度较大,基质的结合强度较强,高温强度明显较高;而加入尖晶石较多时,Al2O3量相对降低,减弱了固溶产生的结合,形成了"松散"的基质结构,可有效提高浇注料的抗热震性,因此加入22.5%质量分数尖晶石细粉的浇注料抗热震性最优。2)随着铝酸钙水泥的增加,浇注料的体积密度逐渐减小,常温抗折强度和弹性模量逐渐降低;当基质中m(CaO)/m(Al2O3)=0.09时,基质中刚玉细粉和Al2O3微粉与水泥在高温下全部反应,生成了大量交错分布的板状六铝酸钙,浇注料的高温抗折强度最高,抗热震性最好。     

矾土基电熔尖晶石对矾土基浇注料性能的影响

为了开发矾土基电熔尖晶石的应用,在矾土骨料、纯铝酸钙水泥、Al2O3微粉、SiO2微粉等原料加入量不变(分别为65%、4%、4%和1%)的条件下,变化矾土基电熔尖晶石的加入量(分别为0、6%、8%、10%和12%)和电熔白刚玉细粉的加入量,研究了矾土基电熔尖晶石对矾土基浇注料常温物理性能、热态抗折强度、抗热震性以及抗渣性的影响。结果表明,与不加矾土基电熔尖晶石的浇注料相比,尖晶石加入量为6%~12%时,浇注料的常温性能相差不大,但热态抗折强度及抗热震性均有所提高,抗渣性有很大改善。     

Al2O3-MA-SiC-C质浇注料的抗渣性能

以电熔白刚玉、镁铝尖晶石、SiC细粉、活性α-Al2O3微粉、球状沥青、Si粉、ρ-Al2O3、氧化硅微粉和铝酸钙水泥为原料制备了Al2O3-MA-SiC-C质浇注料。振动浇注成型后采用静态坩埚法测定了浇注料抗渣侵蚀性,利用X射线衍射、电子探针仪和能谱等手段分析了1500℃埋炭处理3h后试样的物相、显微结构和微区成分,以研究结合剂种类(ρ-Al2O3 氧化硅微粉和铝酸钙水泥 氧化硅微粉)、尖晶石和SiC的加入量对浇注料抗渣性能的影响。结果表明:采用ρ-Al2O3 氧化硅微粉结合的浇注料的抗渣性能明显高于采用铝酸钙水泥 氧化硅微粉结合的,这主要与其在高温下形成的物相有关;随着镁铝尖晶石加入量的增多,浇注料的抗渣性能总体上呈升高趋势;随着SiC加入量的增多,浇注料的抗渣性能显著提高,当SiC加入量(质量分数,下同)为25%时,浇注料的抗渣性能最好;加入过多的镁铝尖晶石和SiC对浇注料的抗渣性能不利,这主要同高温下材料中MgO-Al2O3-SiO2系低熔物的形成有关。     

垃圾熔融炉用无铬浇注料

Al2 O3 -Cr2 O3 耐火材料由于具有优良的抗渣侵蚀性而被用作垃圾熔融炉内衬材料 ,但Al2 O3 -Cr2 O3 耐火材料对环境的危害却日益突出。由于MgO和ZrO2 比Al2 O3 更难被渣熔融 ,因此选用MgO和ZrO2 做骨料 ,研制了一种新型的MgO -MgO·Al2 O3 -ZrO2 浇注料。MgO和Al2 O3 以两种方式加入 ,一种是直接加入尖晶石 ,另一种是加入一定量的MgO和Al2 O3 代替部分尖晶石 ,利用MgO和Al2 O3 反应形成尖晶石产生的体积膨胀促使材料的致密化 ,从而改进其抗渣渗透性。试验结果表明 ,当尖晶石的加入量达到 30 %～ 4 5 %时 ,材料的抗渣侵蚀性…     

二氧化硅微粉对氧化铝-尖晶石浇注料性能的影响

对富含Al2O320%的MgO-Al2O3尖晶石和CaO1.7%及二氧化硅微粉添加达1.3%的浇注料的物理性能进行了研究。结果表明:加入0.1%的二氧化硅微粉有助于增加浇注料的高温抗折强度,而当加入量>0.1%时则非常有害。观察到二氧化硅微粉加入量为0.3%的浇注料在1500℃烧成3h后,由于CA6的形成,出现了最大的气孔率。当二氧化硅微粉的加入量>0.3%时,其气孔率降低的原因则是因为液相烧结。     

垃圾熔融炉用无铬耐火浇注料的开发

过去主要采用Al2O3-Cr2O3质耐火材料作为垃圾熔融炉内衬,然而此类材料的Cr2O3可转变为有毒的六价铬。从无铬条件出发,本文主要就MgO-MgO·Al2O3-ZrO2浇注料的开发进行了研究。采用旋转侵蚀实验装置和EPMA,重点研究了直接加入尖晶石、反应生成二次尖晶石、加入ZrO2等对MgO-MgO·Al2O3-ZrO2浇注料性能的影响。     

添加NiO对高炉出铁沟浇注料中SiC氧化行为的影响

日本有科研工作者已经研究过尖晶石对高炉出铁沟用Al2 O3 -SiC -C质浇注料中SiC氧化行为的影响,得出的结论是尖晶石的存在会促进SiC的氧化。因此,他们又研究了添加2 %的NiO细粉对低水泥结合Al2 O3 -SiC -C和尖晶石-SiC -C浇注料的影响。各浇注试块于1 1 0℃的恒温箱内烘干2 4h ,然后于5 0 0℃热处理3h,以去除沥青中的挥发分,然后再于焦炭粉中进行1 4 0 0℃2 4h的热处理。热处理后的试样测线变化率、质量变化率(与5 0 0℃处理后的试样的原始质量相比较)、显气孔率、体积密度和抗折强度,同时对5 0 0℃和1 4 0 0℃处理后的试样均进行化…     

尖晶石组成和含量对RH浸渍管用方镁石-尖晶石质耐火材料性能的影响

为了研究不同尖晶石组成和含量对RH浸渍管用方镁石-尖晶石质耐火材料性能的影响,以高纯烧结镁砂、电熔镁砂、三种预合成烧结镁铝尖晶石(Al2O3的质量分数分别为50%、66%和78%)为原料制备了方镁石-尖晶石耐火材料试样。研究表明:1)加入尖晶石会降低试样的力学性能和热膨胀系数,但可显著提高试样的抗热震性;2)由于原位生成尖晶石的影响,当加入富铝尖晶石时试样的力学性能和热膨胀系数下降,抗热震性提高;3)加入的尖晶石种类和含量不同,试样的断裂机制有所不同,随着尖晶石加入量的增加以及由富镁尖晶石转变为富铝尖晶石,试样由穿晶断裂转变为沿晶断裂。综合考虑,选择富镁尖晶石且尖晶石加入量(w)为16%~18%时,试样的综合性能较优。     

Slag Resistance of Refractories for Direct Reduction of Laterite Nickel Ores in Rotary Kilns

Aiming at prolonging the service life of refractories for direct reduction of laterite nickel ores in rotary kilns, the slag resistance of ten materials(corundum bricks, chrome corundum bricks, silicon nitride bonded silicon carbide bricks, high alumina silicon carbide bricks, high alumina bricks, magnesia chrome bricks, magnesium aluminate spinel bricks, spinel chrome corundum bricks, chrome corundum castables and magnesia alumina chrome composite spinel bricks) was evaluated by rotary slag tests, which simulate the service conditions in rotary kilns. The corroded residual bricks were analyzed by SEM and EDS. The results show that the magnesia alumina chrome composite spinel brick possesses the advantages of magnesium aluminate spinel bricks and chrome corundum bricks; MgO-rich spinel can absorb the penetrated ferric oxide, and forms a dense zeylanite layer, which prevents the penetration of the molten laterite nickel ores; therefore, it is an ideal lining of rotary kilns for direct reduction of laterite nickel ores.     

Improvement of Durability of Purging Plugs Using MgO Micropowder for Refining Ladles

To modulate the matrix of purging plugs, MgO micropowder was introduced as a replacement to magnesia powder in alumina–magnesia castables, and the effect of MgO micropowder on the properties of alumina–magnesia castables and the possibility of developing chrome‐free castables were investigated. Experimental results showed that the introduction of MgO micropowder resulted in an improvement in the volume stability, strength, and thermal shock resistance of alumina–magnesia castables due to its high surface energy and small particle size. However, excessive amounts of MgO micropowder led to a lower densification, and there was a slight degradation in the performance of the alumina–magnesia castables. The slag resistance of the prepared alumina–magnesia castables was significantly better than that of the alumina–chrome castables. Microstructure and energy spectrum analysis showed that the formation of a solidified reaction layer, mainly consisting of spinel and CaAl₁₂O₁₉, was the major cause of the observed difference in slag resistance. In addition, the alumina–magnesia castables had a lower linear thermal expansion coefficient than that of the alumina–chrome castables at each experimental temperature, which effectively decreased the thermal stress during its service period, thus exhibiting good thermal shock resistance.     

Properties of silica sol bonded corundum‐spinel castables for steel ladles

In order to overcome the shortcoming of the calcium aluminate cement (CAC) bonded castables, we prepared corundum‐spinel castables using silica sol as binder and tabular corundum, sintered magnesia‐alumina spinel, and reactive alumina as raw materials in this study. The effect of spinel grain size and solid content of silica sol on the flow value, sintering, mechanical strength and microstructure of the specimens treated at varying temperature of 400, 1000, 1500, and 1650°C for 5 hours in an air atmosphere were studied by SEM and EDS analyses. The results indicate that silica sol is suitable as a binder for corundum‐spinel systems. And silica sol with solid content of 25% bonded samples containing ≤90 μm spinel perform quite better than the others. At the same time, silica sol bonded samples had high strength in medium temperature. This is because that the closer proximity of silica sol and alumina powder and the high activity of nanometer SiO₂ in silica sol are beneficial for the reaction of SiO₂ and Al₂O₃ to generate mullite needed for reinforcement of castables matrix.     

不同添加剂对镁质浇注料性能的影响

以电熔镁砂和高纯镁砂为主要原料制备了镁质浇注料,研究了不同添加剂对镁质浇注料性能的影响。研究结果表明,5种添加剂中,加入氧化铝微粉的镁质浇注料经1 100℃和1 500℃烧后的体积密度最大,浇注料基质中形成的方镁石/镁铝尖晶石复相结构有利于提高试样的抗热震性。加入氧化铬、铝铬渣和焦宝石的镁质浇注料,其抗热震性均高于未加入添加剂的镁质浇注料的该项性能。     

Use of alumina dispersant in alumina-spinel castable: Comparison between in situ and preformed spinels

The role of alumina dispersant as a flow modifier, completely replacing fume silica, on the properties of preformed and in situ spinel-containing low cement high alumina castables was investigated with variations in spinel content and granulometry. Both 10 and 20 wt.% spinel-containing compositions were prepared using preformed spinel or magnesia in alumina castable compositions with vibratable and self-flowing consistency. The castables underwent conventional processing methods and accessed for various refractory-related parameters post-heat treatments. No glassy phase was observed in the castables upon firing. The presence of self-flowing consistency led to improved characteristics. Preformed spinel-containing compositions showed improved density, strength, hot strength, and thermal shock resistance properties, whereas slag corrosion and penetration resistances were found to be higher for in situ spinel-containing castable.     

促凝剂对刚玉-尖晶石质喷射浇注料性能的影响

本文研究了促凝剂对添加尖晶石细粉和镁砂细粉的两种刚玉-尖晶石质喷射浇注料性能的影响,结果表明:添加镁砂细粉后,喷射浇注料的流变性能下降;通过四种促凝剂对刚玉-尖晶石质喷射浇注料性能的影响研究,发现加入促凝剂后,含镁砂的喷射浇注料增粘变稠的速度快,施工时附着率高;铝酸钠和氢氧化钠复合的促凝剂与两种有机物复合的促凝剂都能使喷射浇注料快速增粘变稠、凝结硬化,但含Na+促凝剂的引入,提高了材料中Na+的含量,降低了喷射浇注料的高温抗折强度、热震稳定性能、抗渣侵蚀性能和常温物理性能.     

Synthesis and evaluation of Mg-Al hydrotalcite formation and its influence on the microstructural evolution of spinel-forming refractory castables under intermediate temperatures

The mechanical properties of in-situ spinel (MgAl₂O₄)-forming alumina-based castables under intermediate temperatures are of critical importance before the refractory lining system reaches normal operating conditions. The objective of this study is to elucidate the role of the hydrotalcite formed within a fine-grained castables matrix, in which no strength loss of the MgO-bonded alumina-based castables without silica fume was observed. Numerous fundamental studies were conducted to examine the factors influencing hydrotalcite formation within the blended pastes composed of MgO and Al₂O₃ nanopowders; dead burned or fused magnesia and Al₂O₃ nanopowder; dead burned magnesia and water-dispersed sol of fumed alumina by using: XRD and DSC-TG-EGA(MS). The XRD, FTIR and ²⁷Al MAS NMR analysis of the hydrotalcite calcination products revealed that the spinel begins to form at temperatures as low as 700 °C. Finally, the physical properties, phase composition and microstructure of the refractory castables bonded with the hydrotalcite decomposition-routed nanostructured spinel were evaluated.     

Improvement of Mullite and Magnesia‐Based Refractory Castables Through Addition of Nano‐Spinel Powder

Two different commercial refractory castables based on mullite or magnesia aggregates have been improved through addition of 0–25 wt.% nano‐magnesium aluminate spinel (MA) powder. Physico‐mechanical and refractory properties were tested at different firing temperatures. The phase composition, thermal analysis, and microstructure of these refractory castables were detected using X‐ray diffraction (XRD), differential thermal analysis (DTA), as well as scanning electron microscope (SEM) attached with energy dispersive X‐ray unit, respectively. The castable sample mix containing 10 wt.% nano‐MA spinel powder was chosen as an optimum composition according to its good sintering, mechanical as well as refractory properties.     

Spinel-containing alumina-based refractory castables

Due to their high corrosion resistance to basic slags, either pre-formed or in situ spinel (MgAl₂O₄) containing refractory castables are nowadays widely used as steel ladle linings. Nevertheless, whereas the pre-formed spinel castables present high volumetric stability and a well-known processing technology, the in situ spinel castables still require further understanding due to the challenges related to magnesia hydration and their expansive behaviour at high temperatures. Therefore, the objective of this paper is to review the knowledge already available for high-alumina spinel-containing castables (preformed and in situ) in order to provide a support for novel technological developments in the area. The main variables considered are the spinel content and grain size, the effect of calcium aluminate cement and hydratable alumina on the general castables’ properties, the influence of different alumina and magnesia sources and the silica fume content. Nowadays research subjects, including the use of mineralising compounds, the addition of nano-scaled particles and the evaluation of the effect of expansion under constraint will also be addressed, pointing out alternatives for the design of high-performance alumina-magnesia refractory castables.     

A Short Communication on Refractories as Kiln Lining along Various Thermal Zones in Pre-calcining Cement Rotary Kiln

Modern cement rotary kiln is often large in size while rotating in high speed. Thermal condition within a rotary kiln is rather complex,exerting severe thermal and chemical attack on refractory of its kiln lining. In the present paper,the cause that leads to refractory failure was analyzed; requirements for refractory to overcome such failure was discussed. Composites and properties of different refractories most often used as kiln lining were assessed,including magnesia-chrome bricks,magnesia spinel bricks, dolomite bricks, silicon carbide mullite bricks and castables etc. Recommendation was made for refractories with suitable composites and properties to be used as kiln lining in each specific zone to best counteract the severe thermal conditions. A cost-effective configuration was presented to assemble kiln lining for rotary kiln's different zones in line with the regulation at JC/T 2196-2013 "Specifications of refractory for cement rotary kiln". Chromite-free refractories with property of high endurance to thermal attack and corrosion are required to be used in modern Pre-calcining cement rotary kilns.