Microstructures and strength of microporous MgO-Mg(Al,Fe)2O4 refractory aggregates

Microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates were prepared using magnesite, Al(OH)₃ and Fe₂O₃ applying an in-situ decomposition synthesis method. At 1400–1600 °C, there was a Mg(Al, Fe)₂O₄ with Fe³⁺, which had two structures. One was a ring structure formed from Al(OH)₃ pseudomorph particle as a template and a low content of Fe³⁺. The other was the dot and strip structures precipitated in magnesite pseudomorph particles with a high content of Fe³⁺. Besides, at 1550–1600 °C, microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates had an excellent compressive strength (75.8–81.5 MPa) and apparent porosity (26.8%?28.2%).     

Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO₂–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.     

Additive manufacturing of SiC-Sialon refractory with excellent properties by direct ink writing

Additive manufacturing of SiC-Sialon refractory with complex geometries was achieved using direct ink writing processes, followed by pressureless sintering under nitrogen. The effects of particle size of SiC powders, solid content of slurries and additives on the rheology, thixotropy and viscoelasticity of ceramic slurries were investigated. The optimal slurry with a high solid content was composed of 81 wt% SiC (3.5 µm+0.65 µm), Al₂O₃ and SiO₂ powders, 0.2 wt% dispersant, and 2.8 wt% binder. Furthermore, the accuracy of the structure of specimens was improved via adjustment of the printing parameters, including nozzle size, extrusion pressure, and layer height. The density and flexural strength of the printed SiC-Sialon refractory sintered at 1600 °C were 2.43 g/cm³ and 85 MPa, respectively. In addition, the printed SiC-Sialon crucible demonstrated excellent corrosion resistance to iron slag. Compared to the printed crucible bottom, the crucible side wall was minimally affected by molten slag.     

Corrosion behavior of Monofrax K-3 refractory in borosilicate-based model low activity waste glass melts

Owing to its good chemical and thermal durabilities at high temperatures, Monofrax K-3 refractory is widely used in nuclear waste vitrification as a lining material in melting vessels. However, the corrosion of K-3 refractory during the vitrification of nuclear waste is a serious problem because it affects the melter's safety, performance, and lifetime. Therefore, in the present study, we have focused on unearthing the impact of glass network formers, such as SiO₂, B₂O₃, and Al₂O₃, in a model nuclear waste glass composition on the corrosion of Monofrax K-3 refractory. The corrosion tests have been performed per ASTM C621 at 1150°C for 5 days. The dimensional measurements on corroded K-3 refractory suggest that Al₂O₃ and SiO₂ tend to reduce the refractory corrosion (neck loss), with the effect of Al₂O₃ being significant. A corroded region on the K-3 refractory at the melt–refractory interface is observed. The corrosion occurs via a coupling of the melt infiltration induced by a capillary effect and the dissolution of Al, Mg, and Fe components from K-3 into the melt through chemical reactions. A Cr-rich layer is retained on the glass contact surface of the corroded K-3 refractory.     

Thermal expansion and Young's modulus evolution of fused silica and crystalline silica-containing materials

Fused silica bricks (FSBs) with exceptional thermal shock resistance are frequently used to repair localized damage in coke ovens and are hold promising candidates for the efficient construction of new coke ovens. To maximize their utilization, the effects of thermal history on the thermal expansion and Young's modulus evolution of FSBs were investigated in comparison to crystalline silica bricks (CSBs). Due to the gradual phase transformation of fused silica into cristobalite, the thermal expansion of FSBs are sensitive to the thermal cycle; both silica materials exhibit an increase in thermal expansion after five cycles at 1200°C, whereas the thermal expansion of CSBs is five times greater than that of FSBs. When the testing temperature is less than 1000°C, Young's modulus of CSBs is more sensitive to the thermal history, which is caused by phase transformation-induced microcracks. This sensitivity reduces when the testing temperature is 1200°C, as microcracks healed by liquid phase as well as the softening of residual glass phase. By contrast, when the testing temperature is 1200°C, Young's modulus of fused silica specimens is sensitive to the thermal history owing to the microcracks caused by the gradual phase transformation of fused silica to cristobalite.     

提高麦尔兹窑寿命的研究与实践

介绍了包钢麦尔兹窑损坏的主要现象,分析了损坏原因,并采取了相应的改进措施。通过优化工艺,严格控制原料质量,控制石灰烧成温度,控制喷枪火焰长度,加强关键部位耐火材料砌筑质量,加强日常管理,取得了较好的使用效果。     

显像管屏玻璃池炉耐火材料侵蚀机理

显像管玻璃池炉耐火材料侵蚀是引发其缺陷的主要原因之一,本文主要论述了彩色显像管屏玻璃池炉耐火材料侵蚀机理,并简要讨论了它们所形成的玻璃缺陷.     

高残碳酚醛树脂粘合剂的合成

合成了高残碳酚醛树脂,研究了醛酚摩尔比、催化剂品种、溶剂对酚醛树脂残碳量的影响。当采用碱金属碳酸盐作催化剂,醛酚摩尔比在1.35-1.37时,树脂具有最高的残碳量。采用最优化工艺合成的液体树脂残碳量达到49%。由此合成的粘合剂应用于含碳耐火材料的生产中,被认为是合适的粘合剂。     

传统块状炭材料的发展概况

传统块状炭材料，如石墨电极、炼铝用阳极和阴极炭块、电炭制品、特种炭和石墨、炭砖等，在国民经济中占据不可替代的举足轻重的地位。本文简要概述了传统块状炭材料的国内外发展现状，在此基础上论述了我国相关领域中存在的问题，以期引起对传统但却十分重要的块状炭材料的进一步重视。     

全氧燃烧玻璃窑炉的寿命浅析

通过对国内外部分全氧燃烧玻璃窑炉的寿命统计,非正常停炉和常见故障等问题分析,找出影响窑炉寿命的因素,提出要以规范化、科学化、系统化的思维,通过新材料、新技术、新工艺的运用有效延长全氧燃烧玻璃窑炉的寿命,对目前全氧燃烧窑炉的建设、推广应用有积极的参考价值。