Several methods to improve the thermal shock resistance of low-carbon magnesia-carbon brick

Refractories with poor thermal shock resistance will cause cracks and crevices on the surface and inside of the material due to temperature changes, and will intensify crack expansion after being washed by molten steel. After many times of scouring, the refractory must be stopped for replacement if the refractory is damaged, which affects production. There are two causes of thermal stress in refractories: One is the large temperature gradient between the surface and the inside of the refractory; The other is that the thermal expansion coefficients of the various phases in the refractory are different. 

The method to improve the thermal shock resistance of materials can be to create micro-cracks on the surface and inside of the material, and use micro-cracks to increase the toughness to neutralize thermal stress; or introduce ceramic phases to increase the overall strength of the material and reduce the overall thermal expansion rate; or introduce low-melting glass The glass phase melts at high temperatures to disperse the thermal stress, but the introduction of the glass phase will reduce the strength and compactness of the material, and it is generally rarely used. 

The influence and reinforcement of carbon source 

Magnesium-carbon materials generally use flake graphite as the carbon source, which has the advantages of good thermal conductivity and low thermal expansion rate. Graphite plays a role in sealing pores and preventing corrosion of molten slag in magnesia-carbon materials. In addition, graphite can also lubricate the surface of magnesia particles and reduce the damage of large particles during the pressing process. 

After replacing flake graphite with artificial graphite particles or different nano-carbons, the thermal shock resistance is significantly improved. Graphite particle size also affects thermal shock resistance. When the amount of resin added is 4% (w), and nano graphite accounts for 5% of the resin mass, the high-temperature mechanical properties and thermal shock resistance of the magnesia-carbon material have been improved. Influence of raw materials and research progress.

The raw materials of low-carbon magnesia carbon materials are usually magnesia and flake graphite, of which magnesia is the main part of the magnesia carbon material. Magnesia can be divided into fused magnesia and sintered magnesia according to its treatment methods and equipment. 

Fused magnesia and sintered magnesia are also divided into different grades according to their respective purity. Generally speaking, the higher the grade of magnesia used, the better the performance of the magnesia carbon material. The slag resistance and thermal shock resistance of the same grade fused magnesia are better than those of sintered magnesia, and as the grade of magnesia increases, the compressive strength increases and the linear expansion rate decreases. The compressive strength is related to the bulk density and porosity of the material. 

Influence of additives and research progress

Additives are an important part of magnesia-carbon materials. Although they do not occupy a high proportion in the ingredients, they can often play a decisive role. Al powder is a commonly used antioxidant in magnesia-carbon materials. It can not only improve the oxidation resistance of the material, but also form ceramic structures such as Al3C4 and AlN at high temperatures to increase the high temperature flexural strength of the material. 

Thermal shock resistance is an important performance of low-carbon magnesia-carbon materials, but blindly improving the thermal shock resistance of low-carbon magnesia-carbon materials may affect other properties of the material, such as oxidation resistance and slag erosion resistance. Therefore, while studying the thermal shock resistance of low-carbon magnesia-carbon material, other properties of the materials must be considered. 

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality magnesia carbon bricks are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc. Shall any interests, welcome to contact us. Our team would make best to be your reliable partner!

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