Interface behaviour and corrosion behaviour of magnesia refractory by alkaline slag in an alkali recovery furnace

The adhesion of Na₂CO₃ slag to the surface of refractories in an alkali recovery furnace can cause corrosion and spall. Magnesia refractories can be used as linings in alkali recovery furnaces owing to their strong corrosion resistance to alkali slag. However, the permeability resistance of magnesia refractories is relatively poor. Hence, the interface and corrosion behaviours of slag cladding on magnesia refractories were studied using sessile drop and static crucible tests. The experimental results showed that an increase in the heating rate positively affected the cladding of the molten column on the refractory surface. The microstructure, element changes, and chemical composition changes of the corroded refractories were analysed using SEM-EDS and XRD. Thermodynamic simulation of the reaction between the slag and refractory was performed using Factsage 7.3. The results indicate that the generated forsterite filled the pores of the magnesia refractories. The microstructure of dense slag-refractory interface layer was formed, which prevented the infiltration of slag phases and alleviated the corrosion of refractories by the slag.     

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…     

Methods of determining the corrosion resistance of glass-tank refractories

Conclusions When laboratory investigations are being carried out to find resistant refractories for glass tank furnaces it is desirable to make simultaneous use of indirect and direct methods of assessing corrosion resistance.The use of indirect methods for determining corrosion resistance in refractories permits us to explain the nature of the interaction between the refractory and glass, to study the nature and properties of the reaction products, and also to select refractories that form with the glass the most infusible or viscous reaction products for subsequent investigation in molten glass.The direct methods permit direct determination of the rate of corrosion of refractories by glass at working temperatures and allow us to recommend the most corrosion resistant refractories for tests in service conditions.In laboratory conditions we established that the most corrosion resistant refractories in regard to original glass used for obtaining slag sitalls are bakor-33 and dense zirconium refractory. This may be explained by the formation of viscous reaction products in the contact layer which have a protective action on the refractory.Translated from Ogneupory, No. 5, pp. 56–60, May, 1967.     

Formation of liquid-phase isolation layer on the corroded interface of MgO/Al2O3-SiC-C refractory and molten steel: Role of SiC

Formation of a dense layer on corroded interface to suppress corrosion is always desired, but it is controlled by numerous environmental conditions. In this work, corroded microstructures of MgO/Al₂O₃-SiC-C refractories in metal bath area of ladle furnace were investigated after industrial trails. A liquid-phase isolation layer in which MgO islands and liquid phases was established on the corroded interface of refractories with 6 wt% coarse/fine SiC-additive. The formed isolation layer against steel/slag attacks led to an approximate 30% improvement in corrosion resistance than that of refractory with 3 wt% fine SiC-additive. More importantly, the liquid-phase isolation layer blocked the direct mass transfer between molten steel and refractories while it decreased exogenous pollution from refractories. SiC-additive affected the formation process of isolation layer by controlling the generation/migration of Mg(g) on refractory' surface. A further formation mechanism of liquid-phase isolation layer was discussed in detail and role of SiC was elucidated.     

不同气相组成下高炉喷补料的抗CO侵蚀能力

研究了高炉用高铝喷补料在纯CO和混合气相95%CO 5%H2(以体积分数计,下同)两种气相组成条件下的抗CO侵蚀能力,并分析探讨了采用混合气相作为侵蚀介质检测耐火材料抗CO侵蚀能力的可行性。结果表明:添加H2促进了CO对喷补料的侵蚀;在两种气相条件下,侵蚀反应生成的沉积碳的结构是相同的,而试样的气孔率和质量随侵蚀时间的延长变化微弱,耐压强度降低明显;同一试样在95%CO 5%H2气相中反应24h与在纯CO中反应200h取得相似的结果。因此,可以用95%CO 5%H2代替纯CO进行耐火材料抗CO侵蚀能力检测,以缩短检测时间。     

Corrosion of refractory materials in fluidised bed gasification of alkali rich fuels

Gasification of renewable fuels is not common practice due to the high costs of technologies and the absence of reliably working refractories. Refractory degradation is of such high significance that improved refractory durability was ranked first by industry experts in a list of 20 research and development areas related to the economic viability of gasification. Therefore, for improvement of the reliability and durability of refractory linings, this work is dealing with the corrosion resistance of nine commercial refractories to a variety of emissions from potential fuels. The refractories were exposed to a gasifier-like, water vapour and alkali rich atmosphere. Exposures with a duration of 250 h produced corrosion effects that were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Furthermore, thermodynamic calculations were included to further explain the equilibrium chemistry. The results show that extremely low silica refractories are promising candidates for gasifier utilisation.     

Evaluation of Corrosion Resistance of Refractory Materials in Furnaces for Melting Frit Glazes

The corrosion resistance of refractories to frit melts applied at the Velor Nompany (city of Orel) are investigated. Based on the results of the study, it is proposed to replace the refractory MKS, which is currently used in furnaces for melting frit glazes, by the refractory material KMTs that is more resistant to frit melts.     

Refractory materials for the melters of plants used in vitrification of radioactive wastes

Results of corrosion resistance tests of different types of refractory materials (fusion cast baddeleyite-corundum, high-zirconium, corundum, and chromium-containing materials) in melts of borosilicate and phosphate glass used for vitrification of radioactive wastes are presented. It is shown that the fusion cast high-chromium refractory materials KhPL-85 and KhMG-5, both of which contain more than 80.0% Cr₂O₃ , possess more than twice the corrosion resistance of the chromium-aluminum-zirconium refractory KhATs-30 (an analog of the refractory material ER 2161) and more than triple that of the baddeleyite-corundum refractories ER 1681 and ER 1711. High-chromium refractory materials may be considered promising candidates for use as the material of melters in plants for vitrification of radioactive wastes.     

含碳耐火材料的电化学侵蚀

为了说明碳或含碳耐火材料在熔渣-金属熔体交界处局部侵蚀的原因,测定了不同熔渣与碳及纯铁构成的高温电池:C|熔渣|Fe的电动势,其值在250至450mV。在这些高温电池中,碳电极皆为阳极(负极),Fe电极皆为阴极(正极)。发现当对此高温原电池外加一反电动势时,碳电极的侵蚀即被抑制。根据这些实验结果,认为含碳耐火材料在熔渣-金属交界处局部侵蚀的主要原因是由于电化学侵蚀机理造成的。文中还拟出了可能发生的电化学反应,并提出了抑制和减轻含碳耐火材料局部侵蚀的措施。     

Isothermal corrosion testing of frit furnace refractories

In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al₂O₃ precipitation observed along the frit–refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al₂O₃ precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite.     

无碱玻璃对含锆耐火材料侵蚀作用研究

介绍了旋转抗渣试验方法,研究了无碱玻璃对3种含锆耐火材料（熔铸AZS砖、致密锆英石砖和颗粒氧化锆砖）的侵蚀作用,采用该方法对试验后的试样利用SEM和EDAX对其物相组成和显微结构进行了分析。结果表明：无碱玻璃熔体的渗入及含锆耐火材料中的ZrO2的熔蚀是材料蚀损的主要原因;致密锆英石砖由于组成和结构的优化,抗无碱玻璃侵蚀性要优于另外两种砖。     

Interaction of magnesium-containing refractories and melts of optical glass

The interaction of magnesium-containing refractory materials and optical glasses is considered. It is shown that in most cases such materials cannot be used in glass melting because their corrosion resistance is lower than in conventional refractories owing to the formation of stones and crystalline inclusions in the glass. It is possible to use magnesium-containing refractories for melting high-lead glass.     

Slag Corrosion Resistance of MgO-ZrO2 Refractories

Slag corrosion resistance of MgO ZrO2 refractories was investigated in this work. The results indicate that in a non-oriented electric steel slag system with a high ratio of calcia to silica,the slag resistance of MgO ZrO2 refractories can be described as follows: ZrO2 reacts with CaO forming calcium zirconate compound which strengthens the material and blocks the channel of the slag infiltration; however,in an oriented electric steel slag system with a high concentration of silica and the low ratio of calcia to silica,the slag corrosion resistance of MgO ZrO2 refractories is different; ZrO2 reacts with CaO forming the calcium zirconate and simultaneously one more product C2S as well; C2S can improve corrosion resistance by blinding pore and enhancing slag viscosity; therefore,it is expected to be the major reason for the enhanced corrosion resistance observed for MgO ZrO2 refractories.     

Improving Lining Resistance Using High-Magnesia Fluxes in the Converter Steelmaking Process

Tests carried out at the Severstal Joint-Stock Co. and Magnitogorskii Iron-and-Steel Works JSC showed that a lime-magnesia flux containing 30 – 35% MgO used in the converter steelmaking process produced a favorable effect on the refractory lining resistance. Compositions for high-magnesia granules (50 – 65% MgO) were developed, their properties characterized, and the rate of solution in the slag melt was determined. Using these granules in the converter process makes it possible to increase the service life of periclase-carbon refractories for converter linings.     

Corrosion Resistance and Microstructure of High-Alumina Refractories, Based on the Rotary Slag Test

The corrosion resistance and microstructure of four highalumina and two chromia-containing high-alumina refractories were evaluated. Analysis of the refractories after exposure in the rotary slag test showed that the chromia-containing products had better slag resistance than the chromia-free products. Three factors contributed to this conclusion, including formation of a Cr-spinel layer at the slag/refractory interface, formation of an impermeable mullite layer just below the interface, and improved matrix bonding from chromia-alumina solid-solution formation.     

Corrosion-erosion behavior of MgAl2O4 spinel refractory in contact with high MnO slag

The corrosion and erosion behavior of spinel refractory of different compressive strength has been investigated for refractories in contact with a high MnO slag for producing manganese ferroalloys. The finger rotating test (FRT) was adopted to evaluate the degradation behavior at 1550 °C under a rotating condition of 150 rpm. The sample with higher compressive strength (Sample C1) showed higher corrosion resistance than Sample C2. In Sample C1, the refractory progressively corroded from the surface to the inner region by chemical corrosion, while mechanical erosion of the refractory suddenly occurred in Sample C2 as a result of the penetration of the slag within the refractory and the rotating energy.     

Effect of coal slag on the wear rate and microstructure of the ZrO2-bearing chromia refractories

The typical properties of slag and refractories for slagging coal gasifier were investigated. In the range of 0–25% CaO/ash, the characteristic ash-fusion temperatures (AFTs) and viscosity of a coal-ash slag decreased with an increase of CaO additive. When the CaO/ash ratio was greater than 25% in the mixture of the coal and limestone, AFTs no longer reduced. The slag viscosity for limestone addition with CaO/ash = 25% was very low and in a narrow range (4–13 Pa.s) at coal gasification temperatures between 1300 °C and 1500 °C. However, corrosion resistance of the ZrO₂-bearing chromia refractories reduced with increasing CaO content in coal slag, especially for a slag with more than 30% CaO content. Increased chromia in three kinds of the ZrO₂-bearing chromia refractories resulted in increased corrosion resistance. The higher the Cr₂O₃ content and the lower the SiO₂ content, the less the deterioration of microstructures in the materials. Thermochemical spalling of the ZrO₂-bearing 80% Cr₂O₃ refractory after 807 operating hours of a coal gasifier was considered as the primary attack mechanism.     

Development and Application of Refractory Materials for Molten Aluminum Applications

Two new refractory materials have been developed for use in molten aluminum contact applications that exhibit improved corrosion and wear resistance leading to improved thermal management through reduced heat losses caused by refractory thinning and wastage. The development of these materials was based on an understanding of the corrosion and wear mechanisms associated with currently used aluminum contact refractories through physical, chemical, and mechanical characterization and analysis performed by Oak Ridge National Laboratory (ORNL) and the University of Missouri, Rolla Rolla (UMR), along with their industrial partners, under the ITP Materials project "Multifunctional Metallic and Refractory Materials for Energy Efficient Handling of Molten Metals." Spent castable refractories obtained from a natural gas-fired reverberatory aluminum alloy melting furnace were analyzed, leading to identification of several refractory degradation mechanisms and strategies to produce improved materials. The newly developed materials have been validated through an R&D industrial trial.     

含硼添加剂对白云石炭耐火材料抗氧化与抗侵蚀性的影响

石墨和结合碳的氧化是白云石炭耐火材料在使用中损坏的重要原因之一。本工作研究了４种含硼材料（ＣａＢ６,ＺｒＢ２,Ｂｃ和Ｃｏｌｅｍａｎｉｔｅ）在白云石炭耐火材料中的行为以及作为抗氧化剂的作用,并与ＡｌＭｇ合金的抗氧化效果进行了对比。在白云石炭耐火材料中,含硼添加剂的防氧化效果优于ＡｌＭｇ合金。在高温下形成的硼酸盐熔体（Ｃａ３Ｂ２Ｏ６,Ｍｇ３Ｂ２Ｏ６）延缓或阻止了碳的氧化,从而提高了含炭材料的抗氧化性。同时,也初步研究了这些含硼添加剂与ＡｌＭｇ合金对白云石炭耐火材料抗侵蚀性的影响。结果表明：两种类型添加剂同时使用可显著提高材料的抗渣性。     

Key features of alumina/magnesia/graphite refractories for steel ladle lining

The corrosion resistance of resin bonded alumina/magnesia/graphite refractories containing different kinds of aggregates were investigated when submitted to the action of slags of several CaO/SiO₂ ratios. The laboratory testing was performed by means of the rotary slag attack test. Specifically evaluated was the influence of alumina/carbon ratio and magnesia and silica contents on the refractories corrosion resistance. It was found that this property could be improved by increasing the refractory Al₂O₃/SiO₂ ratio as well as by choosing the appropriate Al₂O₃/C ratio.