Performance results and analysis of a new type of permanent layer refractory castable for ladle thermal insulation performance

August 29, 2022
1) Physical properties
 
It can be seen from the table that the properties of different ladle permanent layer castables are different.
Table: Physical Properties of Ladle Permanent Layer Castables
 
Zhengzhou Rongsheng
The bulk density of the lightweight mullite castable is 2.17g·cm⁻³, the unit weight is 24% lower than that of the currently used high-aluminum castable, and the thermal conductivity is reduced by 16%, which can achieve the purpose of lightweight and low thermal conductivity of the ladle . CA6 castables are also 5.6% lighter and 26% lower in thermal conductivity than ordinary high-aluminum castables.
 
2) Corrosion resistance test
 
The original ladle permanent layer castable B, the new CA6 castable C, and the light mullite castable 3# were poured into crucibles respectively. The final slag of the converter was added, and the corrosion resistance test of the crucible under the condition of 1500 ℃ heat preservation for 3h was carried out. Observe the melting loss and penetration of different materials. After the test is completed, the crucible is cut open, and the erosion condition is shown in the following figure:
 
Zhengzhou Rongsheng
 
The CA6 castable has the best resistance to erosion and penetration, and there is a large amount of slag left in the crucible hole; the light mullite castable has the second highest corrosion resistance and penetration resistance; the boundary between the slag and the refractory of the ordinary high-alumina permanent layer castable is not clear, and the crucible refractory When it is melted with slag, the penetration resistance is slightly better than the corrosion resistance, indicating that there are more liquid phases in the high-alumina castable at 1500 °C. Therefore, the material needs to be improved to improve its high temperature resistance, which is very important for the safety of the ladle. . The microporosity of the spherical light mullite is beneficial to the improvement of corrosion resistance and permeability, so the light material can also show better thermal insulation and corrosion resistance.
 
3. Application
 
The above three kinds of castables are applied on the 300t ladle. The light mullite castables and CA6 castables for the permanent layer of the thermal insulation ladle are required to have both good resistance to molten steel erosion and thermal insulation, and at the same time, the structural integrity of the furnace service process is good, and the thermal insulation effect is stable. After 3 furnaces, the surface conditions of different ladle permanent layers are shown in the following photos:
 
 
The permanent layer of the above ladle has various degrees of cracks in the later stage of the furnace service, which is related to the thermal shock resistance, strength and damage status of the material during the unpacking process. The comprehensive technology of how to reduce the cracking of the permanent layer material of the thermal insulation ladle still needs to be further studied.
 
From the average temperature of each slag line in each ladle, the steel shell of the uninsulated ladle slag line is above 320 °C, while the average temperature of the 4 thermally insulated slag lines is below 280 °C. Generally, the temperature of the slag line steel shell decreases. 50~100℃. The temperature drop of the steel shell at the cladding part is between 20 and 50 °C, which is slightly different depending on the configuration of the thermal insulation material and the permanent layer material. The thermal insulation material of the thermal insulation test bag remained in good condition during the furnace service period, and the average temperature of the slag line and the cladding steel shell was lower than that of the ordinary ladle, indicating that the permanent layer played a good protective role. In order to ensure safety, the current situation where the cracks of the new permanent layer material are more obvious after 2 furnaces still needs to be optimized and improved to ensure that it can be applied to 4 furnaces.
 
4 Conclusion
 
The thermal insulation ladle has become an important technical measure for iron and steel enterprises to save energy and protect the environment and improve the quality of steel products. The material of the permanent layer of the ladle is given higher requirements. The physical properties of the developed CA6 castable and light mullite castable meet the application requirements of the permanent layer of the ladle, and at the same time have better thermal insulation and corrosion resistance than the conventional high-alumina castable, which can protect the thermal insulation material. The role of the ladle to maintain good thermal insulation during the furnace service period. Further in-depth research is needed on the comprehensive technology to reduce the cracking of the permanent layer material of the thermal insulation ladle.
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