尖晶石粒度对高纯刚玉-尖晶石浇注料性能的影响

研究了尖晶石粒度对高纯刚玉 -尖晶石浇注料的抗折强度、抗热震性、抗侵蚀性等性能的影响。实验表明 :(1)随着配料中尖晶石颗粒含量的增加 ,试样的烧后强度呈先升高后降低趋势 (烘后强度变化不明显 ) ,烧后收缩减少 ,然后变为膨胀 ;(2 )尖晶石细粉与颗粒为 1:3的试样抗热震性较好 ;(3)对于高碱度渣 ,尖晶石颗粒加入量较多的试样抗侵蚀性较好 ;(4)对于低碱度渣 ,尖晶石细粉加入量较多的试样抗侵蚀性和抗渗透性均较好。     

烧结刚玉骨料致密度对刚玉-尖晶石浇注料性能的影响

为了研究烧结刚玉骨料致密度对刚玉-尖晶石浇注料性能的影响,首先以工业Al₂O₃粉为原料制备不同致密度的烧结刚玉;然后以不同致密度的烧结刚玉为骨料制备刚玉-尖晶石浇注料,并研究了刚玉-尖晶石浇注料的致密度、强度、抗热震性和抗渣性等性能。结果发现：1)随着工业氧化铝粉成球坯体致密度的增大,制成的烧结刚玉的致密度和晶粒尺寸逐渐增大。2)随着烧结刚玉骨料致密度的增大,刚玉-尖晶石浇注料的需水性减小;烧后浇注料的致密度和常温强度增大,抗热震性变差。抗渣侵蚀性除采用体积密度为3.45 g·cm^-3的烧结刚玉骨料的浇注料明显较差外,其他浇注料的差别不大。3)综合考虑,烧结刚玉骨料的体积密度以3.51～3.55 g·cm^-3为佳。因此,不能片面地认为烧结刚玉的体积密度越大越好;过高的体积密度会导致耐火材料抗热震性能变差,并增加耐火材料单重。     

钒铁炉渣对矾土基自流浇注料性能的影响

以矾土、钒铁炉渣、硅灰为主要原料,铝酸盐水泥为结合剂,制备了矾土基自流浇注料.测试了试样的常温抗折强度、耐压强度、烧后线变化率,利用X射线衍射(XRD)分析了烧后试样的物相组成,采用扫描电子显微镜(SEM)观察和分析了烧后试样的显微结构.结果表明:随着矾铁炉渣加入量的增加,1 10℃烘后试样强度逐渐降低,1350℃烧后试样强度先增大后减小,试样的体积密度略有降低,形成的镁铝尖晶石相逐渐增多,试样烧后线变化率由收缩转为膨胀;引入适量的矾铁炉渣,有益于矾土基浇注料烧结强度的提高,同时能够有效保持材料的体积稳定性,其最佳加入量为40％.     

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。     

铝酸钙水泥对刚玉基浇注料性能的影响

以电熔白刚玉颗粒及细粉为主要原料,α-Al2O3微粉、铝酸钙水泥以及Alphabond300为结合系统,研究了铝酸钙水泥加入量(质量分数分别为0、0.75%、2.25%和3.75%)对刚玉基浇注料性能的影响。结果表明:1)水泥的加入使浇注料基质的粘度增大,浇注料的流动性降低。2)随着水泥加入量的增加,110℃以及800℃处理后的冷、热态抗折强度均逐渐提高;1 100℃、1 400℃和1 600℃烧后的冷、热态强度均先降低后升高,其中水泥加入量(质量分数,下同)为0.75%时值最小。3)随着水泥含量的增加,浇注料抗热震性提高。4)少量水泥的加入使浇注料的抗渣性能降低,进一步增加水泥加入量,浇注料的抗渣性能逐步改善;在本试验范围内,水泥加入量为3.75%的浇注料和不含水泥的浇注料抗渣性能基本相当。     

水泥和水合氧化铝对铝镁浇注料性能的影响

固定电熔白刚玉、电熔镁砂粉、αAl2O3微粉、SiO2微粉等原料的含量不变,分别加入不同量的水合氧化铝和纯铝酸钙水泥作结合剂(ρAl2O3加入量为2%、3%和4%,水泥加入量为3%、5%和7%),对比研究了水泥结合和水合氧化铝结合铝镁浇注料的显气孔率、体积密度、耐压强度、抗折强度、抗热震性和抗渣性能。结果表明:与水泥结合铝镁浇注料相比较,水合氧化铝结合浇注料具有更好的抗热震性、抗渣侵蚀和渗透性能;水合氧化铝在浇注料中的合适加入量为3%;水泥结合铝镁浇注料具有较高的常温强度,但其抗渣侵蚀和渗透性能随着水泥含量的增加而逐渐降低。     

HiPerCem水泥对刚玉-尖晶石浇注料抗渣性的影响

以板状刚玉、尖晶石细粉和活性α-Al2O3微粉为主要原料,使用HiPerCem水泥作为结合剂制备刚玉-尖晶石浇注料,对比研究了HiPerCem水泥与Secar71及CMA72水泥在浇注料中的凝结行为及其对浇注料常温物理性能、抗渣性能的影响.结果 表明,在保持引入浇注料中一铝酸钙含量为1.8％,尖晶石含量为10％的情况下,HiPerCem水泥结合浇注料的凝结速度居中,脱模及烘干强度较另外2种水泥结合浇注料的低.抗渣侵蚀实验表明,以HiPerCem水泥为结合剂的浇注料因引入的CaO含量较CMA72和Secar71水泥结合浇注料低,大尺寸气孔少,具有较好的抗渣性;而CMA72水泥结合浇注料因试样中大尺寸气孔比例较高,熔渣渗透严重,未能发挥出其水泥中微晶尖晶石相改善抗渣性的优势.     

电熔镁锆砂加入量对RH精炼炉用刚玉-尖晶石浇注料性能的影响

采用粒度为5～3 mm的电熔致密刚玉,3～1、≤1、≤0.074 mm的电熔白刚玉,1～0.044 mm的电熔富铝尖晶石等为主要原料,纯铝酸钙水泥、活性α-Al2O3微粉为结合剂,同时添加适量的微粉和高效复合减水剂,研究了电熔镁锆砂加入量(w)分别为0、2%、4%、6%、8%时对RH精炼炉用刚玉-尖晶石浇注料110、1 100和1 500℃处理后的抗折强度、耐压强度、线变化率,以及1 500℃处理后的耐磨性和1 600℃处理后的抗渣性能的影响。结果表明:1)加入2%(w)的电熔镁锆砂能明显提高浇注料的强度和耐磨性;2)随着镁锆砂含量的增加,线膨胀率明显增大,但电熔镁锆砂加入量为2%～4%(w)的浇注料体积稳定较好;3)加入电熔镁锆砂可以明显提高浇注料的抗渣渗透性,电熔镁锆砂加入量为2%(w)时,试样的抗渣渗透性最好。     

活性MgO和铝酸钙水泥结合刚玉-尖晶石浇注料性能对比

为改善刚玉-尖晶石浇注料的性能，以板状刚玉、活性氧化铝、烧结镁砂细粉为主要原料，分别以活性MgO和铝酸钙水泥(CAC)为结合剂制备了刚玉-尖晶石浇注料，对比了二者对1 600℃煅烧3 h后试样的显气孔率、烧后线变化率、常温抗折强度、常温耐压强度和抗CaO-Al₂O₃-Fe₂O₃-SiO₂(CAFS)渣侵蚀性能的影响。结果表明：经1 600℃热处理后，与CAC结合的刚玉-尖晶石浇注料相比，活性MgO结合的刚玉-尖晶石浇注料的常温抗折强度和常温耐压强度较低，但其体积稳定性、对CAFS渣的抗侵蚀性和抗渗透性显著提高。     

水泥加入量对氧化铝-尖晶石质自流浇注料强度的影响

研究了氧化铝－尖晶石质自流浇注料的力争性能和显微结构。结果表明：当水泥加入量＜10％时,浇注料的强度随水泥加入量的增加而增大;当水泥加入量＞10％时,浇注料的强度无明显增加。此外,水泥加入量过大会影响浇注料的流动性。     

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.     

Effect of spinel content on slag attack resistance of high alumina refractory castables

High alumina refractory castables based on the Al₂O₃-MgO-CaO diagram ternary system were prepared using tabular alumina, white electrofused corundum, calcined alumina, synthetic spinel, dead-burned magnesia, dolomite, and calcium aluminate cement as starting raw materials. Two kinds of slags with 9.02 and 4.14 CaO/SiO₂ ratios were studied for slag resistance by means of crucible tests. The corrosion thickness increases with increase in magnesia content in all the designed compositions. The slag penetration decreases with increases in spinel content. Taking into account these results a refractory castable composition for its positioning into a steelmaking ladle was chosen.

Microstructural studies by SEM of samples taken from the slag line and wall in a steelmaking ladle were carried out. The correct amount of spinel required for practical applications was determined by the Al₂O₃-MgO-CaO-SiO₂ diagram quaternary system. A detailed model of the attack mechanisms is proposed.     

The physical and mechanical properties of alumina-based ultralow cement castable refractories

In this study, the effects of the type of alumina on the physical, chemical and mechanical properties of the ultralow cement castable (ULCC) refractories were investigated. Brown fused alumina, tabular alumina and rotary bauxite-based ULCC refractories were prepared by mixing each type of alumina with silicon carbide, carbon, cement, metallic silicon and microsilica. The density, porosity and cold crushing strength (CCS) of the refractory castables were measured after drying at 110 °C for 24 h and firing at 1450 °C for 5 h. The slag penetration resistance of the refractory castables was determined using slag corrosion tests. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD) were used to characterize the castables. It was found that all three refractory castables had strong slag penetration resistance and that the tabular alumina-based refractory castable had the largest specific cold crushing strength with an acceptable percent of porosity among the refractory castables.     

基质组成对MgO-尖晶石浇注料抗渣性能的影响

采用静态坩埚法研究了添加不同组成尖晶石的ＭｇＯ－ 尖晶石浇注料基质组成与抗渣性能的关系。实验结果表明：随着基质中Ａｌ２Ｏ３ 含量增加,浇注料抗渣侵蚀能力减弱,而抗渣渗透能力增强。在基质中ＳｉＯ２ 含量固定在１０ ％ 的情况下,基质中Ａｌ２Ｏ３ 含量在３０ ％ ～５０ ％ 时浇注料抗渣侵蚀性能较好;Ａｌ２Ｏ３ 含量超过５０ ％ 时,侵蚀速率急剧增加两倍以上。不同组成尖晶石对浇注料抗渣侵蚀性能没有明显影响,但含富铝尖晶石的浇注料具有较好的抗渣渗透性能。     

Effect of micro-spinel powders addition on the microstructure and properties of alumina refractory castables

The microstructural evolution and comprehensive properties of alumina refractory bonded with calcium aluminate cement and silica sol have been studied. Results have been correlated with the microstructural and phase evolutions using X-ray diffraction and scanning electron microscopy, as function of the pre-formed spinel powders. Matrix samples were obtained for phase and microstructural characterization in details, and the results were compared with those corresponding to the refractory castables. The room temperature and high temperature properties, including permanent of linear change, mechanical properties, hot modulus of rupture (HMOR) and slag resistance were measured. The castables exhibited a microstructural optimization and properties enhancement due to the addition of pre-formed spinel. A lot of secondary spinel and CA₆ (CaO·6Al₂O₃) with small size were produced in the castables, and the contents of micro pores were greatly increased. As a result, the permanent of linear change of castables was decreased by 61%, while cold modulus of rupture (CMOR) and HMOR were increased more than 45% and 100%, respectively. The penetration indexes in the static slag resistance were decreased from 28.8% to 12.2%.     

Improved spinel-containing refractory castables for slagging gasifiers

In gasifiers the reaction of a carbon feedstock with oxygen and water takes place to produce synthetic gas. The decrease of the operation temperature at the refractory lining by an innovative gasification technology permits the development of new chrome oxide free materials fulfilling economical as well as ecological aspects. Considering this aspect, spinel-containing refractory castables with increasing spinel content have been investigated according to their thermomechanical properties, phase formation as well as their resistance against corrosion attack by molten coal slag under gasification-similar conditions. In order to determine the influence of spinel and cement in the alumina-spinel castables, increasing spinel amounts and cement types has been added to alumina. In particular, MA-spinel cement has been applied. It has been shown, that the addition of MA-spinel cement to spinel-rich alumina improves the corrosion resistance against molten slag remarkably.     

The impact of bonite aggregate on the properties of lightweight cement-bonded bonite–alumina–spinel refractory castables

The lightweight bonite–alumina–spinel (CA₆–Al₂O₃–MA) refractory castables with bonite aggregate and different spinel sources (pre-formed and in situ formation) were prepared in this study. The phase composition, microstructural features, and mechanical and thermo-mechanical properties of CA₆–Al₂O₃–MA castables treated at various temperatures were investigated by techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending method, and thermal shock test. The results indicated that the incorporation of bonite aggregate had a positive influence on the strength, thermal shock resistance and slag corrosion resistance. It especially decreased the thermal conductivity and had a slightly negative influence on the refractory under load and slag penetration resistance of the castables. For the in situ spinel-containing castable, the formation of in situ spinel with finer particle sizes and acicular CA₆ grains led to higher overall volume expansion, resulting in higher thermal expansion (∆L/L₀), linear change and the apparent porosity of castables. Also, the heat insulation, thermal shock and slag penetration resistance of castables with in situ spinel improved, while the strength, displacement, refractory under load and slag corrosion resistance decreased sharply.     

Improvement of corrosion resistance of spinel-bonded castables to converter slag

Limited chemisorbed hydroxyl groups around the crystalline entity of gel-route spinel powder helped to create nanopores in castable to resist slag penetration. The retained nanodimensional spinel in fired castable firmly connected hibonite and corundum grains, developed several interfaces after initial stage of densification, and arrested the detrimental ions of slag. XRD, scanning electron microscope (SEM) with atomic force microscope (AFM) studies of the nanostructured spinel-bonded castables corroborated their better properties than similar kind bonded with preformed spinel. The performance of spinel with 90% alumina and the conventional in situ spinel-bonded castables were satisfactory whereas the coprecipitated spinel was not commendable.     

锆英石和氧化铝加入量对镁质浇注料性能的影响

研究了锆荚石和氧化铝的加入量对镁质浇注料常温物理性能、热震稳定性、高温抗折强度（１４５℃,１ｈ）及抗渣性能的影响。结果表明：锆英石和氧化铝的加入均降低了镁质浇注料的常温强度,提高了其热震稳定性,但对高温抗折强度影响不大;适量锆英石和氧化铝的加入均能改善镁质浇注料的抗渣渗透性。     

Basic slag attack of spinel-containing refractory castables

The better performance of spinel-containing refractory castables when in contact with basic slag is mainly associated with their higher corrosion resistance. Although the literature has shown various studies related to this subject, only few of them evaluated the overall microstructural effect on the corrosion resistance. Considering this aspect, four different compositions were produced, in order to evaluate the binder source influence (calcium aluminate cement or hydratable alumina), the silica fume addition and spinel incorporation method (in situ or pre-formed) effects. Based on the physical properties (apparent porosity, linear thermal expansion and pore size diameter distribution) and also on the phases generated (detected by SEM, before and after corrosion), a basic slag corrosion mechanism, for the set conditions, is proposed. The results pointed out that lower penetration can be attained by reducing the pore size diameters, whereas chemical corrosion resistance is a consequence of higher content of fine alumina, lower amount of calcium aluminates and the lack of liquid phase in the castable matrix. This study stresses that the castable formulation design and the proper raw material selection are of utmost importance to understand and master the performance of this class of refractory castables.