With the improvement of energy conservation and environmental protection requirements,the lightweight of kiln has become and inevitable trend of development.the development of low thermal conductivity and energy-saving refractories is mainly reflected in the following aspects:
- Design of material structure using lightweight aggregate:light weight is achieved under the premise of ensuring the necessary corrosion resistance and strength of the material.
- Microporous technology:adding burnt-out materials to control pore refinement and homogenization
- Multi-layer gradient composite technology:study the thermal matching stability control technology of structural refractory composite interface,and prepare gradient lightweight refractory materials.
A refractory company in China has developed low-density fired magnesia bricks with a bulk density of 2.75-2.80g.cm³ and a porosity of 23%.it is mainly used ofr permanent lining of industrial furnaces such as electric furnaces.the function of heat insulation is a good energy-saving product,the main composition(W) is:MgO91.0%,CaO2.5%,normal temperature compressive strength≥40Mpa,0.2Mpa load softening temperature≥1500℃
- Unshaped development
Due to the increase in the types of scrap steel used in electric steelmaking,especially the application of low-grade scrap resources,the electric furnace conditions are more demanding,and the refractory materials are accelerated.in order to improve the service life of the electric furnace,the refractory materials used in various parts of the electric furnace are raised higher.requirements,the development of new unshaped refractory materials and the application of repair technology have been greatly developed,and the overall service life of the lining can be greatly improved without affecting normal production.Magnesium ramming material is mostly used for the working lining of the bottom layer of the electric furnace,and the part is damaged quickly due to direct contact with the molten steel,Dolomite ramming material has excellent anti-flaking and wear resistance as an alternative material,and the application effect is very good,the domestic refractory company uses high-quality magnesia and special synthetic magnesia-calcium sand as the main ram materials,and controls the suitable particle grading to develop a magnesia-calcium ramming material with excellent bulk density ,it is easy to be sintered and can form ceramic bond and stratify,the characteristics of transitional sintering have good anti-scour and anti-corrosion properties,the spray material is mainly magnesium material which can be sued for ultra high power electric furnace slag line and hot spot,highly erosive dolomite ramming materials developed by Japanese researchers and dolomite and magnesium siliceous spray materials that can be thermally sprayed at temperatures above 1100℃，these spray materials are easy to apply and have good adhesion.
For the electrode sheath brick of the DC arc furnace,it is subjected to extremely high temperature when passing current,and is also eroded by molten steel and refining slag,and often needs to be repaired.the repair of the electrode cover brick is also achieved by thermal spray,and the spray compensation temperature is ≥800℃
In order to meet the technical development needs of electric steelmaking,a series of high-performance refractory materials have been developed at home and abroad,and promoted and applied.there refractory materials not only have the characteristics of high temperature structure stability,anti-flaking,abrasion resistance and slag resistance,but also reflect the development concept of energy saving,green environmental protection in the new era.with the rise of electric furnace steelmaking,refractory materials for electric furnaces will surely be better developed.the development trend of refractories for steelmaking electric furnaces in the future is:
- Develop and promote low-carbon(or carbon-free) and long-life refractories;
- Research and development of refractory materials that are lightweight and have good high temperature performance;
- Development of new non-chromic refractories;
- Promote and apply new unshaped refractory materials and high temperature repair technology.