Diversification of refractory materials to meet the new requirements of the steel industry
Refractories are the basic materials for the steel industry. The refractory industry and the steel industry promote each other and develop together. As China's economy enters a new normal, the iron and steel industry presents a series of new features: excess capacity, declining profitability, increased environmental and resource constraints, and increased challenges of transformation and upgrading. The new normal in the steel industry has put forward new requirements and new thinking on refractories, driving new changes in the refractory industry upstream of the industry chain. In recent years, the performance and application of refractories have been characterized by specialization, diversification, refinement, and high efficiency and low consumption. The development of refractories must adapt to this and will also be diversified, enriched and characterized. The situation is evolving.
1 Refractory material new requirements of multiple performance
1.1 Green new requirements
1.1.1 Meet the requirements of clean steelmaking
Clean steelmaking puts forward new requirements for ironmaking and steelmaking-related auxiliary materials and refractory materials to reduce and avoid pollution of the iron and steel. Research and practice found that aluminum and silicon refractory materials will pollute the steel, magnesium materials do not pollute, containing free CaO material not only does not pollute, but also clean steel. Therefore, it is preferred to contain free CaO, good resistance to hydration of sintered fused calcium magnesium raw materials.
In order to reduce carbon contamination of the steel by carbon containing refractories, the carbon content of carbon composite refractories needs to be reduced. In order to eliminate the side effects of thermal shock and erosion resistance, a dispersed carbon source needs to be introduced. The development and production of various carbon nano sources suitable for refractory materials such as carbon black, carbon nanotubes and graphene are promoted.
In order to reduce the intermediate ladle working lining on the refining steel "dephosphorization" effect, the development of low or no phosphorus combination system.
1.1.2 Meet the "green" requirements of the steel industry
In view of the carcinogenic effect of Cr6+, refractory materials containing chromium have been restricted by the state. It is imperative to replace chromium-containing materials with new low-chromium, non-chromium materials. Such as RH and other refining furnace using high-performance magnesium carbon bricks, magnesium aluminum spinel bricks, magnesium zirconium bricks, etc., can replace the traditional magnesium chrome bricks.
The gun clay used for blast furnace outlet generally uses tar as the binding agent. In order to reduce the pollution of the environment during the production and use, people are encouraged to develop new environmentally friendly binders.
In order to reduce the harm to the environment and human body during the production, processing, use, installation and post-processing of traditional aluminosilicate refractory fibers, biodegradable calcium magnesium silicate refractory fibers were developed and used.
1.1.3 Meet the requirements of energy saving and emission reduction in the steel industry
As an industrial furnace lining material, the use of energy-saving refractory materials is imperative. In recent years, the development and application of new raw materials conducive to energy saving include: lightweight mullite based materials with microporous structure, mullite hollow spheres, lightweight microporous sintered alumina, CA6-MA composite lightweight aggregate, olivine lightweight materials, spinel lightweight materials, nano porous silica powder and its polymers, etc.
1.2 Development of economic refractory materials
At present, the refractory industry and the steel industry related to the refractory raw material industry chain are in a downturn, and the low price winning bid becomes the direction of the supply chain relationship. On the other hand, some high-grade natural mineral raw materials such as high bauxite gradually depleted, ore grade decline, quality fluctuations increased, relying on high-grade raw materials to improve performance, cheap raw material technology configuration route to reduce costs has gradually come to an end. Guided by this direction, cheap, economical refractory raw materials and products will become a major trend.
Low consumption is the main development direction of economic refractory materials. The main direction to achieve low consumption of raw materials is to expand the use of natural raw materials, lightly burned materials and recycled materials. In order to ensure the high-temperature volumetric stability of refractories, natural raw materials must be sintered or fused at high temperatures to make them barren and as close as possible to a thermodynamic equilibrium state. This leads to high energy consumption and a certain degree of overcapacity, in a sense resulting in an invisible waste of resources and energy. It is possible to develop and apply non-equilibrium raw materials with lower sintering temperatures than conventional ones.
Studies have shown that adding a certain amount of natural raw material castables has good results. The gases escaping from the decomposition of the raw material after heating form channels that help to improve the anti-burst performance. Adding raw gangue or lightly burned gangue to aluminum-silica castables, which generate in-situ mullite after heating, can improve its thermal flexural strength, load softening temperature and thermal shock resistance, and also help to realize heavy and light weight quality materials.
Facing the current situation that high-grade mines are gradually depleted and low-grade mines are increasingly becoming the main source of raw materials, people must reconsider the scientific and reasonable, adaptable raw materials and product indicators, and optimize the configuration of raw materials. materials to make them more excellent and useful. Competitive cost performance. Consider appropriately lowering the AL2O3 content and capacity of high-alumina refractories used in certain non-melt erosion and erosion parts, and relaxing the impurity content requirements of aluminosilicate refractories for media.
