Diversified development of refractory materials to adapt to the new normal of the steel industry

　　Refractory materials are fundamental materials in the steel industry. The refractory materials industry and the steel industry promote each other and develop together. As China's economy enters a new normal, the steel industry has shown a series of new characteristics: overcapacity, declining profitability, increasing environmental and resource constraints, and more challenges in transformation and upgrading. The new normal of the steel industry has put forward new requirements and new thinking for the refractory materials industry, which is at the upstream of the industrial chain, and has led to new changes. In recent years, the performance and application of refractory materials have shown characteristics of specialization, diversification, refinement, high efficiency, and low consumption. The development of refractory raw materials must adapt to this, and will also evolve towards new trends such as diversification, enrichment, and specialization.

　　1. Diverse manifestations of new requirements for refractory raw materials

　　1.1 New requirements for green environmental protection

　　1.1.1 Meeting the requirements of clean steelmaking

　　Clean steelmaking has put forward new requirements for reducing and avoiding pollution of molten iron and steel in related auxiliary materials and refractory materials used in ironmaking and steelmaking. Research and practice have found that aluminum-silicon refractory materials will pollute molten steel, magnesia materials do not pollute, while materials containing free CaO not only do not pollute, but also have the effect of cleaning molten steel. Therefore, sintered and electrically melted magnesium-calcium raw materials containing free CaO with good water resistance are favored.

　　In order to reduce the carbon pollution of molten steel by carbon-containing refractory materials, it is necessary to reduce the carbon content of carbon composite refractory materials. In order to eliminate the side effects of decarburization on the performance of thermal shock resistance and erosion resistance, it is necessary to introduce a dispersed carbon source. This has promoted the research and development and production of various nano-carbon sources suitable for refractory materials, such as carbon black, nano-carbon tubes, and graphene.

　　In order to reduce the "return phosphorus" effect of intermediate vessel linings on refined molten steel, low-phosphorus or phosphorus-free bonding systems have been developed. 2.1.2 Meeting the requirements of "green" steel industry

　　Given the carcinogenic effect of Cr6+, chromium-containing refractory materials have been listed by the state as restricted products, and it is imperative to replace chromium-containing materials with new low-chromium and chromium-free materials. For example, high-performance magnesia-carbon bricks, magnesia-aluminum spinel bricks, and magnesia-zirconium bricks can be used in RH refining furnaces to replace traditional magnesia-chromium bricks.

　　Gunpowder used for tapping in blast furnaces generally uses tar as a binder. In order to reduce environmental pollution during production and use, people are promoting the development of new environmentally friendly binders.

　　In order to reduce the harm to the environment and human body during the production, processing, use, installation, and post-treatment of traditional alumina-silica refractory fibers, biodegradable calcium-magnesium-silicate refractory fibers have been developed and used.

　　1.1.3 Meeting the requirements of energy saving and emission reduction in the steel industry

　　As industrial furnace lining materials, the use of energy-saving refractory materials is imperative. In recent years, new raw materials that are conducive to energy saving have been developed and applied, including: microporous lightweight mullite-based raw materials, mullite hollow spheres, lightweight microporous sintered alumina, CA6-MA composite lightweight aggregates, olivine lightweight materials, spinel lightweight materials, nano-porous silica powder and its polymers, etc.