China's Refractories

Henan refractories industry is a major refractory production base in China, which is also an advantage industry in Henan province. Recently, Henan provincial government has formulated relevant industrial and environmental protection policies, and approved the construction of “Henan Province New Refractory Industry Cluster”. Henan's main refractory enterprises have developed a series of green technologies, processes and products, and carried out automation and intelligent transformation, equipment upgrading, and the deep integration of information technology and refractory manufacturing through interconnection and digital empowerment. To promote the high-quality development of refractory industry, The Association of Henan Refractory Industry has established a series of standards and evaluation systems of refractories including air pollutant emission, energy consumption limits, carbon emission limits, green products, etc. The Association of Henan Refractory Industry also organized exchanges and mutual cooperation between enterprises inside and outside the region, and guided the development of specialization, refinement and innovation. This paper summarized the relevant works of refractories in Henan, and put forward some suggestions for solving the existing problems of refractories in Henan.

In order to improve the service performance of Al₂O₃-SiC-C castables, a novel Si-N-O composite micropowder was synthesized by the chemical combustion method. Using brown corundum, sintered alumina, silicon carbide, active α-Al₂O₃ micropowder, SiO₂ micropowder, calcium aluminate cement, Si powder and spherical asphalt as the raw materials, adding additive of Si-N-O composite micropowder, Al₂O₃-SiC-Si₃N₄/Si₂N₂O-C castables were prepared. The effects of the Si-N-O composite micropowder addition on the mechanical properties and oxidation resistance of the castables were investigated, and the intrinsic mechanism of strengthening and antioxidation caused by this novel additive was discussed. Experimental results show the introduction of Si-N-O composite micropowder leads to significant improvement in the cold strength, oxidation resistance, thermal shock resistance and hot modulus of rupture of the Al₂O₃-SiC-C castables. When the Si-N-O composite micropowder addition is approximately 3 mass%, the castable possesses the best comprehensive performance.

The effects of two types of corundum-spinel micropowders (D and G) on the phase composition, bulk density, apparent porosity, mechanical properties, and slag resistance of corundum-spinel castable matrices were investigated. The results indicated that, with the same addition of corundum-spinel micropowders, in-situ spinel was formed in both groups after firing at 1 100 °C. After firing at 1 600 °C, spinel, corundum, and CA₆ existed in the two groups. Compared to the samples with powder D, those with powder G exhibited higher bulk density and lower apparent porosity after firing at 1 100 °C, but the cold modulus of rupture and compressive strength were lower. After firing at 1 600 °C, the cold modulus of rupture of the samples with powder G was higher, meanwhile there was minimal difference in the apparent porosity between the two groups. Both corundum-spinel micropowders showed good sintering activity, and the matrix samples exhibited excellent slag resistance. The corundum-spinel castable matrix with powder G showed better corrosion resistance compared to that with powder D.

In order to prepare high density magnesium aluminate spinel materials, the light-burned magnesia and alumina powder were used as the main raw materials. Active magnesium aluminate spinel powders were synthesized at different temperatures, and the sintering properties of the synthesized materials were characterized. The results show that the optimal light-burned temperature for synthesizing active magnesium aluminate spinel raw materials with small grain sizes and high sintering activity is 1 400 °C. The active spinel raw materials were sintered at 1 750 °C for 3 h to form a dense spinel material, in which the spinel grains were well developed, exhibited a dense interlocking structure, and were uniformly distributed, with an average grain size of about 7.26 μm. The bulk density and apparent porosity of the dense spinel material were 3.29 g · cm^-3 and 3.5%, respectively.

Silica-based ramming mixes are widely used as lining materials in coreless induction furnaces, which serve as the main equipment for iron and steel in foundry industry. The service life of linings made from silica-based ramming mixes depends on the properties of quartzite raw materials. In this paper, quartzites from three regions were selected as raw materials, with boron oxide and boron phosphate as sintering aids. By comparing and testing performance such as the phase composition, permanent linear change, bulk density, apparent porosity, and slag resistance, the effects of raw material characteristics and sintering aids on the performance of the silica-based ramming mixes were investigated. The results showed that boron oxide-containing ramming mixes prepared from quartzite with a fast phase transition showed lower strength and greater expansion as well as lower slag penetration index. For boron phosphate as a sintering aid, ramming mixes made from quartzites with medium and slow phase transition rates had an approaching slag penetration index comparable to those containing boron oxide, although their strength was lower than the latter. According to the melting requirements of stainless steel, boron phosphate can replace boron oxide as a sintering aid for silica-based ramming mixes. Regarding practical applications for linings of coreless induction furnaces, the selection of quartzite as the raw material for silica-based ramming mixes shall be comprehensively considered from multiple aspects.

Ceramic microspheres not only have excellent properties of ceramic materials (low density, large specific surface area, high strength, high hardness, as well as good chemical stability, high temperature resistance and wear resistance), but also have many advantages of microspheres due to their sphericity, making them widely used in nuclear industry, biology, medicine, chemical industry, military industry, environmental protection and many other fields. This paper mainly introduces several methods for preparing ceramic microspheres, including the methods of forming spheres using crystallographic principles, such as the sol-gel method and polymerization-induced colloidal aggregation method; the methods of forming spheres through extrusion, friction, collision and other mechanical forces, such as the air grinding method and die pressing method; and the methods to form spheres using the principle of surface tension, such as the spray drying method and melting method. In addition, the hydrothermal method, hard template method and emulsion-gel injection molding method were also introduced.

Currently, chemical furnaces play an important role in the chemical industry. It is necessary to ensure their quality and operation performance, so as to guarantee the efficiency of chemical production. Compared with other furnaces, chemical furnaces have strong particularity, which puts forward higher requirements for the thermal shock resistance of the refractories of furnace linings. This paper studied the thermal shock resistance of the refractories for chemical furnace linings, and proposed measures for improvement, providing experience and technical support for the safe production of chemical enterprises.