加入ZnO对含Al低碳MgO-C耐火材料抗氧化性的影响

以质量分数为70%的粒度≤3 mm和24%的粒度<0.074 mm的电熔镁砂,3%的粒度<0.15 mm的鳞片石墨,3%的粒度<0.045 mm的金属铝粉为原料,外加4%的酚醛树脂制备了含Al低碳MgO-C耐火材料。加入1%(w)的<0.045 mm的ZnO替代电熔镁砂粉,研究了加入ZnO对含Al低碳MgO-C材料抗氧化性的影响。通过对比这两种材料的显气孔率、常温耐压强度,试样基质的物相变化来探讨原位尖晶石的生成与基质中加入ZnO之间的关系,并通过对比试样中脱碳层与原始层之间出现的致密MgO层来讨论两种低碳MgO-C材料抗氧化性的差异。研究表明:加入ZnO能够在MgO-C材料基质中形成ZnAl2O4,并加速尖晶石的原位生成,使得材料中能够更快更多地形成致密的MgO层,最终提高低碳MgO-C耐火材料的抗氧化性。     

催化剂种类对低碳MgO-C耐火材料常温性能的影响

以电熔镁砂、鳞片石墨和Si粉为原料,以掺入硝酸铁、硝酸钴和硝酸镍的酚醛树脂为结合剂,通过原位催化热解酚醛树脂的方法,在氩气气氛下,分别经800、1 100和1 400℃热处理,制备了低碳MgO-C耐火材料。研究了不同催化剂对低碳MgO-C耐火材料常温性能的影响,结果表明：硝酸铁为最佳的催化剂,硝酸铁的引入促进了碳纳米管(CNTs)和SiC晶须的原位生成,提高了耐火材料的力学性能。含硝酸铁的酚醛树脂加入试样时,经1 100℃热处理后其常温抗折强度和常温耐压强度最高。     

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。     

低炭MgO-C质耐火材料的抗熔渣侵蚀行为

以碱度为 3.0和 1.0的钢渣对石墨含量(w)为 0、2 %、4 %、6 %和 12 %的MgO -C质试样进行了回转抗渣试验 ,并对侵蚀后试样进行了SEM、EDAX和EPMA分析。结果表明 :当石墨含量 (w)≤6 %时 ,试样在两种渣中的侵蚀深度都随石墨含量的增加而减小 ,而当石墨含量达到 12 %时 ,其侵蚀深度又都增加 ;碱度 1.0的渣对石墨含量 (w)≤ 6 %的MgO -C材料的侵蚀严重 ,而碱度 3.0的渣对石墨含量 (w)为 12 %的MgO -C材料的侵蚀严重 ;低碱度渣中Si、Fe对MgO致密层的熔损比高碱度渣中的严重。     

膨胀石墨对MgO-C耐火材料性能的影响

含石墨的MgO-C耐火材料具有优异的抗渣性和抗热震性,是炼钢工业最重要的耐火材料。然而,较高的石墨或碳含量会导致MgO-C耐火材料的高温强度降低,耐火衬的热导率增加。因此,需要减少碳含量且不降低抗热震性。印度的研究人员利用膨胀石墨代替鳞片石墨,并研究了MgO-C材料的性能。试验基础配比(w)为:粗、中颗粒的高纯电熔镁砂65%,镁砂细粉28%,鳞片石墨5%,Al粉1%,B4C粉1%,外加热塑性酚醛树脂4%。以质量分数分别为0.2%、0.5%、0.8%的     

IMEXSA电炉用MgO-C 耐火材料的回收

在DRI熔炼期间进行了电炉和钢包用MgO-C耐火材料的回收利用。进行了冶炼试验,以确定耐火材料回收对能源消耗、熔炼时间、熔剂消耗和耐火材料消耗的影响,制备方法以及喷射方法也包括在内。依据目前的研究结果,推荐对废弃的耐火材料回收利用。目检表明,在开始加热时对渣起泡有益,允许使用全部的功率变压器,反过来导致快速的熔炼率。     

MgO-C耐火材料抗折强度分布规律的研究

以两种不同碳含量的MgO-C耐火材料为研究对象,对试验测得的抗折强度数据采用Weibull函数进行统计分析,并结合试样的断口形貌研究了MgO-C耐火材料的抗折强度分布规律。结果表明:MgO-C耐火材料的抗折强度服从Weibull分布;增大材料的致密度和石墨含量能够降低MgO-C耐火材料抗折强度的离散性,提高强度的可靠性。     

电磁场对MgO-C耐火材料抗熔渣侵蚀性的影响

采用碳含量为14%(质量分数)的MgO-C砖和CaO与SiO2的质量比为0.8的转炉渣,分别在中频感应炉和电阻炉中进行抗渣侵蚀实验.结果表明:感应炉环境中存在的电磁场使抗渣试样中出现明显的渗透层,MgO与渣中氧化铁形成的固溶体在温度降低时以镁铁尖晶石相存在,而低熔相主要为钙镁橄榄石和镁橄榄石.在无电磁场存在的电阻炉中,...     

不同石墨碳源对MgO-C浇注料性能的影响

分别以电熔镁砂和4种石墨碳源——用电熔镁砂和鳞片石墨制成的w(C)≈35％的造粒石墨(PG)、w(C) =98.34％的焦炭石墨(CG)、w(C) =99.08％的电极石墨(EG)、废镁碳砖(MC)为原料,制备了碳含量均为5％(w)左右的MgO-C浇注料,研究了不同石墨碳源对浇注料物理性能、抗氧化性能和抗渣性能的影响.结果表明:加入适量石墨碳源可以显著提高镁质浇注料的抗渣渗透性;含PG、CG和EG的MgO-C浇注料比含MC的显气孔率低,强度更高,抗氧化性更好;与石墨化程度较低的CG、EG相比,含鳞片石墨的PG、MC更有利于MgO-C浇注料抗渣性能的提高,并且石墨以细小鳞片状的形式在基质中均匀分布对抗渣性非常有利.     

β-SiAlON对MgO-C材料性能的影响

以电熔镁砂颗粒(5～3 min、3～1 mm、≤1 mm)、电熔镁砂细粉(≤0.088 mm)、鳞片石墨(≤0.15 mm)、矾土基β-SiAlON细粉(≤0.088 mm,气孔率28%,Z=2)为主要原料,配制成ω(鳞片石墨) ω(矾土基β-SiAlON细粉)分别为12% 0、4% 6%、4% 9%和4% 12%的4组配料,采用酚醛树脂作结合剂,以180 MPa压力成型.经185℃10 h固化后,按相关标准检测了试样的体积密度、显气孔率、常温耐压强度、常温抗折强度、高温抗折强度、抗热震性、抗氧化性和抗渣性.结果表明:随着试样中ω(鳞片石墨) ω(矾土基β-SiAlON细粉)按12% 0、4% 6%、4% 9%、4% 12%的顺序变化,试样的显气孔率有所上升,体积密度略有降低;试样的常温耐压强度、常温抗折强度、1 400℃高温抗折强度、抗热震性和抗氧化性均有不同程度的提高;抗渣侵蚀性以ω(鳞片石墨) ω(矾土基β-SiAlON细粉)为4% 6%的试样略高,其他试样则有所降低.     

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。     

微孔富镁尖晶石对低碳MgO-C材料性能的影响

分别以微孔富镁尖晶石(5~3和3~1 mm)和电熔镁砂(5~3和3~1 mm)为粗骨料,以<1 mm的电熔镁砂为细骨料,以镁砂粉(≤0.088 mm)、鳞片石墨粉(≤0.088 mm)、金属铝粉(≤0.074 mm)为细粉,以酚醛树脂为结合剂,制备了w(C)=6%的两种低碳MgO-C材料,经220和1 500℃(埋焦炭)热处理后,测定其显气孔率、常温耐压强度、常温抗折强度、加热永久线变化率、抗热震性和抗渣性。结果表明:1)用微孔富镁尖晶石骨料取代普通低碳MgO-C材料中的部分镁砂骨料后,经220和1 500℃热处理后试样的显气孔率均比普通低碳MgO-C试样的大,体积密度均比普通低碳MgO-C试样的小;220℃固化后试样的强度比普通低碳MgO-C试样的小,但1 500℃热处理后试样的强度比普通低碳MgO-C试样的大;1 500℃热处理后试样的加热永久线变化率比普通低碳MgO-C试样的小。2)使用微孔富镁尖晶石骨料代替电熔镁砂骨料能有效提高低碳MgO-C材料的抗热震性,但对低碳MgO-C材料的抗侵蚀性不利。     

添加半成品废砖的再生镁碳砖研究

为了回收利用镁碳砖生产过程中产生的半成品废砖,将半成品废砖经拣选、破碎、筛分后制成3～1、≤1和≤0.088 mm三种粒度的再生料,然后在镁碳砖常规配方中添加20%(w)的再生料制成再生镁碳砖试样,研究了试样的颗粒级配(粗颗粒、中颗粒、细粉的质量分数分别为44%～56%、14%～26%、24%～36%),再生料加入方式(分级后分别与相同粒度的其他料混合后加入或不分级直接与电熔镁砂颗粒料混合后加入),树脂添加量(外加质量分数分别为3.8%、4.0%、4.2%、4.4%)对再生镁碳砖试样性能的影响,并与未添加再生料的镁碳砖试样进行了对比。结果表明:1)适当增加中颗粒料的量,减少细粉的量,可以提高再生镁碳砖试样的致密度和抗氧化性能,但对强度影响不大。2)再生镁碳砖试样中树脂的最佳外加量(w)为4.0%。3)与不分级直接加入相比,再生料分级加入可以有效提高再生镁碳砖试样的致密度和强度。4)通过工艺优化,添加20%(w)再生料的再生镁碳砖试样的性能可以达到YB 4074—91中镁碳砖MT14A的技术要求。     

Improvement of low carbon MgO-C refractories by MA-CA2 additives fabricated from metallurgical waste

In the present work, MA-CA₂ material was fabricated by adding industrial alumina into industrial waste residue, and its effect on the physical properties, oxidation resistance, slag resistance, and thermal shock resistance when it was added to the composition of a low carbon MgO-C refractory was discussed in detail. Although the introduction of MA-CA₂ material led to a slight inferior slag corrosion resistance, the volume stability and oxidation resistance of refractories were improved. Moreover, the samples containing MA-CA₂ addition showed significantly lower thermal expansion coefficients and increased thermal shock resistance performance. However, owing to the dissolution of SiO₂ impurity into the MA-CA₂ material, an excessive addition of MA-CA₂ material would increase the liquid phase amount in the sample during the heat treatment and slag attack, resulting in a performance degradation. In this study, the best comprehensive performance of the MgO-C refractory was obtained with 6 wt% MA-CA₂ addition.     

Improvement in fatigue resistance performance of corundum castables with addition of different size calcium hexaluminate particles

Cyclic loading of catalytic gasifier lining refractories is one of the most important factors causing fatigue failure. A three-point bending fatigue experiment was carried out to explore the influence of calcium hexaluminate (CA₆) particle size distribution on the fatigue resistance of corundum castables. Five different castables were damaged by fatigue, the curve of the fatigue strain against the number of cycles has a classical sigmoid shape with three phases: firstly, the strain rate decreases; secondly, it remains unchanged; thirdly, it increases significantly. The maximum strain during fatigue failure is generally greater than in monotonic loading. It has been found that the combination of the grain-matrix plays a critical role in fatigue failure. The fatigue resistance of pure corundum castable decreased significantly at 1100?°C. The surface roughness of CA₆ can be effectively combined with the matrix. The fatigue resistance of the corundum based castable where 3-1?mm tabular alumina particles were replaced by he same size of CA₆ particles is best after treatment at either 110?°C or 1100?°C.     

Improved properties of low-carbon MgO-C refractories with the addition of multilayer graphene/MgAl2O4 composite powders

The paper investigated the effects of different amounts (0%, 3%, 6%, 9%) of in situ multilayer graphene/MgAl₂O₄ composite powders on the slag resistance, thermal shock resistance, and oxidation resistance of low-carbon MgO-C refractories. Comparing with commercial MgAl₂O₄, the MgAl₂O₄ in in situ multilayer graphene/MgAl₂O₄ composite powders has higher lattice strain of crystal, which can trap more Mn and Fe ions, resulting in the better slag resistance. The oxidation decarbonation layer of MgO-C specimen with 3% composite powders is 9.71 mm, which is lower than not only the specimen with other contents but also specimen containing carbon black/MgAl₂O₄ powders. Moreover, the residual strength ratio of the specimen C/MA-3 was 47.47%, which is 28.5% and 8.08% higher than specimens with no additive and with carbon black/MgAl₂O₄ powders, respectively. Both improving thermal shock and oxidation resistance properties are related with the unique nano structure, multilayer graphene in situ formed between MgAl₂O₄ grains, of added composite powders. The former is due to higher strain energy consumed by multi-deflection of cracks inside the multilayer graphene/MgAl₂O₄ composite powders. And the latter is due to the higher energy of oxidation activation of multilayer graphene/MgAl₂O₄ composite powders due to effective protection of multilayer graphene by MgAl₂O₄.     

Gas corrosion behavior of calcium hexaluminate materials for hydrogen metallurgy

Calcium hexaluminate (CA₆) has good chemical stability under H₂ atmosphere, which indicates its application prospect in the hydrogen metallurgy field. However, iron ores usually contain SiO₂ impurities, which can react with H₂ to form Si-containing gases such as SiO (g) and SiO₂ (g). The Si-containing gases might corrode CA₆-based lining refractories during hydrogen metallurgy. The silica and magnetite were heated in a hydrogen furnace to simulate the gaseous environment of hydrogen metallurgy in this paper. At the same time, the corrosion of CA₆ materials at elevated temperature (600 °C–1800 °C) under the hydrogen metallurgy atmosphere were studied. In addition, three SiO₂ based raw materials (silica, fused silica and waste silica brick) with different SiO₂ contents were used to investigate the effect of impurities on the their H₂ corrosion. The result showed that SiO₂ based raw materials had good chemical stability under H₂ atmosphere at the temperature lower than 1200 °C, obvious weight loss appeared at 1400 °C, the impurities including Fe₂O₃ and MgO would accelerate mass loss under H₂ atmosphere. Gases including SiO (g), SiO₂ (g) and H₂O (g) could react with CA₆ to form corundum and yoshiokaite at 1800 °C, which resulted in 3.16% weight gain after heating at 1800 °C for 8 h under the hydrogen metallurgy atmosphere. No significant mass change and mineral phase transformation appeared at the reaction temperature less than 1600 °C.     

电磁场环境下碳含量对MgO-C砖抗高碱度渣侵蚀性能的影响

为了探索Mg O-C砖在电磁搅拌、电弧炉和感应炉等电磁场环境下使用时的抗渣侵蚀性,采用w(C)分别为6%、14%的Mg O-C砖和m(Ca O)/m(Si O2)=3.5的炉渣在中频感应炉中进行抗熔渣侵蚀试验,并对渣蚀后试样进行了XRD和SEM、EDAX分析。结果表明:在电磁场环境下,w(C)=6%的镁碳砖渣蚀后低熔点相为镁黄长石,w(C)=14%的镁碳砖渣蚀后低熔点相为黄长石。镁碳砖渣蚀过程中,w(C)=6%的镁碳砖中镁砂未完全形成镁铁(锰)固溶体或镁铁尖晶石即剥落于熔渣中;而w(C)=14%的镁碳砖中镁砂形成镁铁(锰)固溶体或镁铁尖晶石后剥落于熔渣中;在渣蚀后镁碳砖过渡层中,电磁场促进了Al2O3、Mn O、Fe O、Fe2O3的渗透,生成镁铁(锰)固溶体、镁铁尖晶石、镁铝尖晶石或金属单质,w(C)=14%的镁碳砖渗透较弱,生成的固溶体或尖晶石较少,易剥落于熔渣中。