Ladle is one of the equipment required for steelmaking process. With the improvement of converter life, the increase of continuous casting ratio and the progress of refining technology outside the furnace, the ladle is in increasingly harsh conditions of use such as large capacity, multiple steel types, high temperature and long time, and the requirements for refractory bricks for ladles are also increasing.
Problems and countermeasures encountered in the development of refractory materials for domestic ladles at present
1. The proportion of brick-built ladles is relatively high
At present, a considerable number of ladles still use high-alumina bricks. Under the condition of equivalent cost, the refractory material consumption of brick-built ladles per ton of steel is about 1kg higher than that of integral ladles. It is unwise to continue to use high-alumina bricks. Compared with integral casting ladles, brick-built ladles have the following shortcomings: first, the melting loss is fast and the pollution to molten steel is large; second, the masonry workload is large and maintenance is difficult; third, the safety is poor. Therefore, integral casting ladles should be used as soon as possible on ladles with conditions. The cladding of some 300t ladles has been severely deformed due to long service life and cannot be put into the mold core for casting. Prefabricated bricks have also been tested for this part of the cladding. The cost and consumption are comparable to or even better than the overall cladding. It is currently in use. After gaining experience, it is necessary to further promote it.
2. Low life of the cladding bottom
At present, many cladding bottom bricks are wax stone-silicon carbide refractory bricks, with a service life of only 25 times. This is the worst link in the refractory materials of the ladle and the main reason for the high consumption of refractory materials. The main reason why some ladles use the overall casting of the cladding bottom and cannot use it in large quantities is the difficulty in maintenance. Since the minor repair cycle is only 25 times, there are many cold steel interlayers after multiple repairs, and the life cannot reach more than 125 times reported abroad. At the same time, the cost per ton of steel is 2 to 3 times that of wax stone-silicon carbide bricks. Currently being tested is the use of aluminum-magnesium spinel prefabricated bricks in the impact zone and high-aluminum unburned bricks around, with a target life of up to 50 times.
3. Too short minor repair cycle
At present, the minor repair cycle of the ladle is 25 times, while the international advanced steel mills are generally around 50 times. The short minor repair cycle leads to high consumption of refractory materials and low heat turnover rate of the ladle. The main obstacle to improving the ladle minor repair cycle is the low life of the water inlet and air bricks. Various materials of water inlets have been tested, and the life is difficult to be greatly improved. A repair ring has been developed that can extend the life to more than 25 times. The structure of the water inlet and the base brick is currently being studied to enable it to be replaced in a hot state, and it is estimated that it will be successful soon.
4. High consumption of refractory materials for special steels
Some steel grades (such as steel cord steel and electrical steel) have particularly large melting losses on refractory materials, especially steel cord steel, which has special requirements for refractory materials. General refractory materials cannot be used. When smelting this kind of steel, the slag line life sometimes does not even reach 10 times, the number of ladle repairs is high, and the consumption of refractory brick is extremely high. Although the output of this kind of steel is not large, it has a great impact on the consumption of refractory materials in the ladle. Refractory materials that meet the smelting requirements of these steel grades must be developed.
5. Backward maintenance judgment technology and standards
To reduce the consumption of refractory materials in the ladle, there must be scientific and reasonable residual thickness management standards. Since the residual thickness of the ladle is basically determined manually, which is arbitrary and risky, operators often consider the importance of ladle safety production more and ignore the cost. To reduce the consumption of ladle refractory materials, advanced judgment and maintenance technology must be used, such as: using laser thickness measurement to ensure the safe use of the ladle; using wet spraying technology to maintain the ladle lining; air brick hot replacement safety system. By improving the reliability of the safe use of refractory materials, the waste of refractory materials can be reduced.
Development trend of refractory materials for ladle
Looking at the development and current situation of refractory bricks,it can be considered that the development trend of refractory materials for ladle in the future is:
(1) Pay attention to the development and utilization of local resources, especially make full use of waste resources. Develop neutral and alkaline refractory materials.
(2) The life of domestic ladles is relatively low, so alkaline linings, spinel linings, high-alumina linings and their corresponding composite lining structures will appear in large quantities.
(3) The proportion of domestic amorphous refractory materials used in ladles will continue to increase, which is of great benefit to small die casting manufacturers. However, for manufacturers using continuous casting technology, high-quality composite brick ladles will account for a considerable proportion.
(4) The application scope of carbon-containing products continues to expand.
(5) Reduce consumption and clean ladles. Reducing consumption can not only reduce costs, but more importantly, it can reduce pollution to molten steel; cleaning ladles requires the use of carbon-free refractory materials with low melting loss on the one hand, and reducing slag sticking to the ladles on the other hand.
