In order to meet the needs of multi-furnace continuous casting and energy saving and consumption reduction in the iron and steel industry, and to adapt to the increasingly stringent conditions of use in out-of-furnace refining, researchers at home and abroad have been devoting themselves to research and development of high-quality, new and efficient refractory materials to increase the service life of ladles. And then promote the development of refractory materials for ladle lining. The reason why the development of iron and steel smelting technology promotes the continuous improvement and innovation of refractory materials for ladles can be summarized as the following two aspects: On the one hand, with the gradual increase in the mechanization requirements for lining masonry, the lining refractory materials tend to be amorphous; On the other hand, due to the popularity of secondary refining and continuous casting, the use conditions of ladles are more severe, which promotes the transformation of lining refractory materials to high purity, high performance and high grade.
The changes of refractory materials used in ladle lining can be divided into three important periods:
(1) Before the 1970s:
Before World War II, European and American countries mainly used the micro-expansion of pyrophyllite refractory bricks at high temperatures to prevent selective melting at the joints of ladle lining bricks. In the 1950s and 1960s, clay and graphite-clay refractory bricks were widely used in Europe and America. In 1960, Japan tried out stable dolomite and tar dolomite refractory bricks in the 50t ladle of Yawata Company. Although the service life reached 70~100 furnaces, the sticking problem was not popularized, so silicic acid more resistant to alkaline slag erosion was developed. Zirconium refractories. At the same time, the wave of mechanization of lining construction followed. In the second half of the 1960s, with the rise of the European throwing process, refractory materials adapted to this new construction method were developed one after another, which was the beginning of the development of refractory materials without shape.
Before the 1970s, clay bricks, ordinary high-alumina bricks and semi-siliceous bricks were mainly used to build ladles in China. less than 50%. The low service life of the lining material not only causes the consumption of a large amount of refractory materials, but also frequently removes the lining and builds the lining, which also greatly increases the labor intensity of the workers. At the same time, due to the large amount of impurities produced by the melting loss of the lining material, the non-metallic phase inclusions in the molten steel are increased, resulting in a decline in the yield and quality of the steel.
(2) In the 1970s and 1980s:
Refining technology outside the furnace has gradually become popular, and the application environment of ladles has become more and more severe. Traditional high-alumina bricks and high-alumina castables have begun to fail to meet the use requirements. In order to meet the needs of high-purity and alkaline (neutral) linings for refining outside the furnace, researchers from European and American countries have made many beneficial attempts, among which the more representative ones are magnesia-silicon, magnesia-chrome and magnesia-mullite. Castable. Finally in the 1980s, researchers explored the best point of refractory corrosion resistance and amorphous, and developed aluminum-magnesium castables. At the same time, Japanese researchers tried to add zircon as raw material to pyrophyllite shaped products, researched and developed a series of ZrO2-Al2O3-SiO2 series refractory materials such as zirconium silicate bricks, which effectively improved the slag resistance of the material Erosion ability.
(3) Since the 1990s:
Since the 1990s, direct bonded magnesia-chrome bricks and magnesia-carbon bricks have been applied to ladle linings due to their better thermal shock stability and low reaction rate with molten steel. At the same time, corundum-spinel castables have been widely used in the working lining of the ladle and the impact area of the bottom of the ladle, etc., and achieved good results. Europe and Japan adopt in-situ synthesis technology to replace pre-synthesized spinel with alumina and magnesia added to the castable in situ to generate magnesia-alumina spinel phase, and the fine spinel particles generated in situ are dispersed in the castable matrix Among them, the anti-slag invasion performance of the castable is effectively improved.
In the 1990s, high-efficiency continuous casting technology became the focus of the development of my country’s steelmaking industry. In order to meet the needs of the development of steelmaking technology, my country put the research and development of aluminum-magnesium-carbon bricks into practical applications, which greatly improved the corrosion resistance of the lining. performance, thereby increasing the service life of the ladle. At the same time, in 1994, Baosteel introduced high-purity aluminum-magnesium castables produced in Japan (spinel was introduced in situ) and corundum-spinel castables produced in Europe (spinel was introduced in situ). Introduced in a pre-synthesized way). In the process of comparing and testing two imported castables, a complete set of ladle construction, use and maintenance technology was successfully explored. In the middle and late 1990s, on the basis of the existing castables, from the perspective of cost reduction, my country independently improved and developed high-grade aluminum-magnesium castables and put them into use. In practical application, it is found that high-grade aluminum-magnesium castables have reached the world’s leading level in terms of construction performance, service life and cost per ton of steel.
Nowadays, the research and application of refractory materials for ladle lining are mainly concentrated on Al2O33-MgO-CaO series, which are different from shaped bricks in various types, complicated masonry, and difficult to repair. They are made by adding ultrafine powder or using high-purity raw materials. The Al2O3-MgO-CaO system castable has more excellent and more balanced performance in all aspects, which greatly improves the service life of the ladle.