α-Al_2O_3微粉对低碳MgO-C材料性能的影响

以电熔镁砂及鳞片石墨为主要原料,热塑性酚醛树脂为结合剂,研究了α-Al_2O_3微粉对低碳MgO-C材料性能的影响.结果表明:(1)Al_2O_3微粉的加入提高了低碳MgO-C材料的体积密度,降低了显气孔率,提高了强度,显著改善了MgO-C砖的抗氧化性;(2)高温下Al_2O_3微粉与MgO原位反应生成连续的尖晶石相,改善了材料基质的显微结构,增强了陶瓷结合,将MgO颗粒与鳞片石墨紧密地结合起来,提高了组织结构的整体性,从而提高了材料的致密度和强度;(3)高温下原位反应生成连续的尖晶石相堵塞脱碳层中的部分气孔,降低了氧的扩散速度,同时提高了MgO的沉积速度,使加入Al_2O_3微粉的低碳MgO-C材料抗氧化性能得以提高.     

几种钢包用含碳耐火材料对IF钢增碳的比较

通过感应炉试验分析了钢包渣线用3种碳含量不同的镁碳砖(C的质量分数分别为8.3%、15.5%和17.9%),钢包底用蜡石-碳化硅砖(C的质量分数为3.71%)以及实验室开发的MgO-Al2O3-SiC质钢包渣线浇注料(C的质量分数为4.07%)对IF钢增碳的影响,并对其增碳的机理进行了初步分析讨论。试验结果表明:渣线镁碳砖的碳含量越高,对IF钢造成的增碳量越大;包底蜡石-碳化硅砖对IF钢水的增碳量达到渣线镁碳砖的7.73倍;MgO-Al2O3-SiC质浇注料也对IF钢产生明显的增碳效果,不宜用作冶炼超低碳钢的钢包渣线材料。     

Corrosion Resistance of High-Alumina Graphite Based Refractories to the Smelting Reduction Melts

1 Introduction The corrosion resistance of the refractories is one of the imperative problems for the development of smel- ting reduction with iron bath[1 ~4]. The Al2O3-C based refractories have been widely and successfully used in the metallurgy industr…     

A Review on Some Applications of Magnesia in Current China Refractories Industry

Being rich in the magnesite resource,China hasbecome the biggest magnesia-based products manufac-turer.With nearly300magnesite mines including somenewly built magnesite processing plants,China has to-tal output of over14million tons magnesite ore peryear,…     

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-     

Al2O3-SiC-C耐火材料抗CaO-SiO2-K2O渣侵蚀性能研究

研究了Al2O3-SiC-C耐火材料的抗CaO-SiO2-K2O渣侵蚀性能,以及添加Cr2O3对Al2O3-SiC-C材料抗渣侵蚀性能的影响.研究结果表明CaO-SiO2-K2O熔渣对Al2O3-SiC-C材料具有明显的侵蚀作用;在Al2O3-SiC-C材料中添加适量的Cr2O3可以有效地抑制CaO-SiO2-K2O熔渣向耐火材料内部的渗透,降低耐火材料的侵蚀速度.     

Properties,Performance and Quality Control of Recycled MgO-C Bricks

Properties, section structure and service results of recycled MgO-C bricks and new MgO-C bricks for ladle slag line of Baosteel were analyzed and compared, and the measures of improving stability and quality of recycled MgO-C bricks were summarized. The results show that: (1) High quality recycled MgO-C materials can be produced by scientific, meticulous and strict management for every process such as dismantling furnace, selection, removing impurity and slag, stacking and homogenization; (2) Using high qua...     

新一代矾土基耐火材料

可以期望在新世纪我国根据丰富的高铝矾土资源特点,新一代矾土基耐火材料将会兴起--优质合成原料和高效耐火新产品.优质合成原料包括:(1)Al2O3含量为50%～90%的均质矾土熟料(均质类);(2)矾土基烧结和电熔锆刚玉莫来石和锆刚玉尖晶石系合成料(改性类);(3)矾土基Sialon和Alon(转型类).利用这些合成料开发的矾土基高效新产品为:(1)高温性能优良的高品位高铝砖和浇注料,(2)矾土基刚玉系材料,(3)矾土基Al2O3-Sialon(Alon)复合材料.     

AOD炉渣对MgO-C砖的侵蚀机理研究

不锈钢生产主要采用氩氧精炼(AOD)炉冶炼工艺,本文探究AOD炉渣对钢包内衬用MgO-C砖的侵蚀机理,为提高钢包内衬用MgO-C砖的使用性能和服役寿命提供理论支撑。结合FactSage6.2软件、X射线衍射(XRD)、场发射扫描电子显微镜(SEM)和能量色散光谱(EDS)等测试手段分析炉渣侵蚀后MgO-C砖的物相变化、显微结构和化学成分变化。结果表明,随着侵蚀反应的进行,方镁石逐渐被熔蚀,且逐步出现Ca₃MgSi₂O₈等低熔点物相,以及MgAl₂O₄等高熔点物相。AOD炉渣通过基质部分侵蚀渗透MgO-C砖,并与方镁石反应生成Ca₃MgSi₂O₈等低熔点物相,熔蚀方镁石;同时,方镁石边界处生成MgAl₂O₄,阻碍AOD炉渣对MgO-C砖的侵蚀渗透。     

TiO2 在Al2 O3 -SiO2 系耐火材料中的作用

阐述了TiO2在Al2O3-SiO2系耐火材料,特别是高铝矾土中的分布和存在方式,并通过分析Al2O3-SiO2系耐火原料的煅烧过程和Al2O3-SiO2系制品的使用过程中TiO2、Al2O3和SiO2三者之间的化学反应,介绍了TiO2对Al2O3-SiO2系耐火材料结构和性能的影响。     

两种不同铁水熔蚀炭砖微观结构分析

为提高高炉炭砖的抗铁水熔蚀性,对两种不同铁水熔蚀性炭砖进行了岩相和电子显微镜分析.炭砖的微观结果分析表明,无烟煤基质的炭砖抗铁水熔蚀性优于在原料中添加石墨的炭砖;往基质中加入Al_2O_3可大为改善炭砖的扰铁水熔蚀性;工艺上使Al_2O_3均匀分布是提高炭砖抗铁水熔蚀性的重要措施.     

Innovative Lining of Unburnt Al_2O_3-MgO Brick for 300t Steel Ladle in Baosteel

The manufacture of clean steel needs high performance carbon-free bricks for ladle lining.Based on long term application experiences of the prefab Al₂O₃-MgO blocks,unburnt Al₂O₃-MgO brick has been developed by pressing a mix of alumina,spinel and magnesia as major raw materials and Al₂O₃-MgO gel powder as binder.In addition to low open porosity and high strength,the unburnt Al₂O₃-MgO brick shows superior corrosion resistance and thermal shock resistance to the prefab block.Field trials in a 300t steel ladle have indicated the residual lining of unburnt Al₂O₃-MgO bricks showed smooth surface without large spalling and seldom steel infiltration,consequently longer service life than the prefab blocks.The reliable,unburnt Al₂O₃-MgO bricks have more advantages of high efficiency,energy-saving and eco-friendly production.It will be one of the best options for ladle lining in the manufacture of high-purity steel.     

Role of Calcium Magnesium Aluminate in Carbon-containing Bricks for Steel Ladle

Calcium magnesium aluminate,with the commercial name of MagArmour,is a synthetic material consisting of 70 mass%Al₂O₃,20 mass%MgO and 10 mass%CaO,approximately.It is characterized by porous microstructure,intergranular aluminates phases and micro-crystalline spinel.Since globally launched in 2017,MagArmour has been successfully applied to various carbon-containing refractories serving for steel refining process.Lots of cases have demonstrated the role of MagArmour in enhancing the service life of carbon containing bricks for ladle lining.The benefits embody in formation of protective coating on hot surface,relief of drilling corrosion in joint positions,and elimination of grooves or cracks caused by mechanical stress concentration.In addition,MagArmour is effective in protecting graphite from deep oxidization so as to be capable of replacing the metallic or carbide anti-oxidants in carbon-containing bricks entirely.By means of chemical analysis and microstructural dissection,postmortem investigations on the used MgO-C bricks from both metal and slag zones of 120t steel refining ladle were conducted to clarify the working mechanism of MagArmour.The formation of protective coating on hot face is attributed to the dissolution of micro-crystalline spinel into contacting slag,which changes the slag chemistry so as to enhance viscosity.The improvement in corrosion/erosion resistance is highly related to the porous microstructure and dispersive aluminates.As well known,evaporation of Mg,Al and SiO,and/or internal migration,occurs in MgO-C bricks at elevated temperatures.The gaseous phases are absorbed by MagArmour particles due to the high surface area of porous microstructure and condense as corresponding oxides.These oxides react with the intergranular calcium aluminates forming liquid phase.With increasing temperature,the liquid phase seeps into the matrix under capillary force.The increased liquid amount improves the flexibility of the matrix and thus releases the internal stresses concentration resulting from mechanical stress and temperature gradient.Meanwhile,densification of the matrix microstructure occurs under the static pressure generated by liquid steel and molten slag,which blocks the channels of oxygen infiltration.     

Method of raw materials selection for production of the MgO-C bricks of comparable properties using PCA and K-medoids

MgO-C refractories are zonally installed in most of the key heat devices of steel and iron metallurgy with the exposure to various corrosive factors. One of the most significant factors is low-temperature decarburization resulting in the oxidation of carbon in MgO-C refractories and loss of its properties. Moreover MgO-C materials are exposed for direct attack of liquid slag or steel melt which easily infiltrate the porous, decarburized hot face of the bricks. Cost of MgO-C materials of high quality is important for refractories user. For this reason researches try to develop materials of high quality but with lower cost by substituting fused raw materials with sintered ones or with recycled MgO-C. In this article, method of selecting the raw materials for production of MgO-C bricks with comparable properties is shown. Twenty different variants of MgO-C materials were prepared with the use of various quality raw materials. Basic properties of the industrially produced MgO-C bricks were measured. To select recipes with similar quality principal components analysis method and K-medoids algorithm were applied. To verify the results corrosion resistance of selected MgO-C materials were tested with the use of induction furnace of medium frequency.     

A Retrospective Review of Alumina-magnesia-carbon Refractories

The residual expansion of in-situ spinel formation in using of alumina-magnesia-carbon(AMC)bricks monolizes the lining of steel-making ladles with the closure of their joints,which has been an effective solution avoiding washing out of the joints in ladle lining by the reduction of the penetration of liquid slag and molten steel.Alumina-magnesiacarbon refractories are overall reviewed,in terms of major raw materials,thermal evolution,corrosion and oxidation,and thermomechanical behavior,as well as type,addition and fraction of magnesia used.General commercial products contain 5%-10%MgO and 5%-10%C with a certain amount of metallic aluminum powder,which is believed to facilitate spinel formation at early stage of heating-up,although high magnesia containing AMC bricks are studied and used sometimes.With low ratio of Al₂O₃/C=12.9 and the carbon content of 6.4%C,AMC brick exhibits the highest corrosion resistance.It is important to determine the type,addition and fraction of magnesia used in AMC refractories for demonstrating high corrosion resistance and superior thermomechanical behavior.     

再生镁碳砖和铝镁碳砖在精炼钢包上的应用

介绍了采用64%～88%质量分数的用后钢包再生料制造的再生镁碳砖和再生铝镁碳砖的性能以及在精炼钢包上的应用情况。使用结果表明,根据使用条件和再生料的特点,把镁碳砖的制造技术和使用条件结合起来设计制造的再生镁碳砖,其使用效果显著好于原镁碳砖:在300 t精炼钢包渣线上的使用寿命提高15%,在50 t LF-VD炉渣线上的使用寿命提高50%以上。     

气化炉用后高铬砖的渣蚀机理

采用扫描电镜和XRD等分析方法,对石油焦气化炉和水煤浆气化炉用后高铬砖及渣蚀试验砖的显微结构进行了观察与分析。根据高铬砖显微结构变化,研究了在不同气化炉内高铬砖受熔渣侵蚀损毁的机理。结果表明:石油焦气化炉用高铬砖中的Cr2O3与熔渣中的V2O5接触反应,在低温下形成液相而被熔蚀,是其蚀损的主要原因;水煤浆气化炉用高铬砖蚀损的主要原因是Cr2O3在熔渣里的溶解和ZrO2的熔蚀;LIRR-HK95砖由于成分和结构的优化,抗石油焦渣侵蚀性能好。     

Corrosion mechanism of MgO-C bricks used as linings in a vanadium extraction converter

To extend the service life of MgO-C bricks used as linings in vanadium extraction converters, their corrosion mechanism was investigated using stationary immersion and rotary crucible methods at 1673 K. The effects of oxides in vanadium slag were studied using the slag invasion method. The results showed that a decarburization layer was formed but was not effectively sintered under vanadium extraction conditions, resulting in it having a loose structure and poor binding strength. When slag-splashing technology was applied to protect the converter, the decarburization layer and slag-splashing layer easily fell off due to scouring by the molten pool. Consequently, the poor strength of the decarburization layer was the main reason for the poor anti-erosion performance of the MgO-C bricks and the weak effect of slag-splashing technology. In addition, higher contents of SiO₂ and TiO₂ in vanadium slag could form low melting point compounds and increase the thickness of the decarburization layer, thereby accelerating the MgO-C brick corrosion rate. Higher contents of FeO in the vanadium slag not only formed low melting point compounds but also caused a decarburization reaction with the MgO-C bricks. However, with increases of V₂O₃ in the slag, the formation of high melting point compounds decreased the corrosion rate and corrosion depths.     

Performance of a ceramic frit anti-oxidation coating on a MgO-C refractory brick

In steel production, ladles must be preheated to minimize the heat loss of the steel melt, prevent thermal shock of refractory bricks (MgO-C), and to maximize the lining life of ladle. Partial oxidation of MgO-C bricks begins in the graphite bond during the preheating. Oxidation of graphite bond also causes a decrease in performance of the bricks because of an increase in the brick porosity. In this article, coating on a MgO-C brick surface by a ceramic film to protect against carbon oxidation was studied. Coated and un-coated bricks were heated at 1200 °C, cooled to room temperature, then the brick properties investigated. The oxidization resistance properties of brick with coating were much better than those without coating, which should lead to longer refractory service life.     

Effect of Ti （C,N） on Properties of Low-carbon MgO- C Bricks

The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.