What are Damage Factors of Refined Ladle Slag Line?
Zhengzhou Kiln Refractory factory has done a lot of research on refractory materials for refined ladle slag lines, mainly in the area of oxides and carbonaceous products. The currently successful and widely used slag line material is
magnesia carbon brick. In the past, MgO-Cr203 refractories have been used, and the amount of chromium is reduced due to environmental pollution.
Magnesia carbon brick used for the slag line has a carbon content of 10%-20%, and the working surface is oxidized to form a surface decarburization layer during use. Due to the oxidative removal of carbon, the loose and brittle of the brick structure is washed away by the steel and the slag. At the same time, due to the removal of carbon and the looseness of the brick body, the slag penetrates into the decarburization layer and reacts with the magnesia to cause the disappearance of the periclase and the disintegration of the magnesia particles. After oxidation, decarburization, erosion, and then a slag corrosion, and repeated, causing damage to the magnesia carbon brick. The formation speed of the decarburization layer on the working face of the magnesia carbon brick dominates the damage rate of the brick, especially the preheating of the new refined ladle leads to serious damage of the magnesia carbon brick. In order to improve the service life of magnesia carbon bricks, it is necessary to improve the oxidation resistance of the products. Therefore, it is an important subject for researchers to protect the carbon in the Mg0-C brick and to withstand the oxidizing atmosphere without loss.
Conditions for Use of Refined Ladle
The specific conditions for the use of refined ladle are:
LF refining temperature 1550~1610 °C, refining time: 35-45mins;
VD furnace vacuum degassing, processing temperature 1550~1610 °C, time greater than 20min;
whitening during refining Slag, using refined synthetic slag, submerged arc slag, high alkalinity (mass ratio of CaO to SiO2 is greater than 3.5);
Argon agitation at the bottom of the whole process;
5) average tapping temperature above 1650 °C, average residence time of ladle in ladle Above 130mins.
In the process of using ladle, there are mainly the following problems:
1) the slag line erosion speed is faster;
2) the slag line brick breaks in the middle, and sometimes the block phenomenon occurs.
Analysis of the Causes of Damage of Ladle Clinker Magnesia Carbon Bricks
In order to meet the needs of smelting new steel grades, the electrode heating temperature is high during refining, the argon gas agitation time is long, the refining slag has low viscosity, and the corrosion is strong, and sometimes VD vacuum tow gas treatment is required, and thus the magnesia carbon brick of the slag line is damaged. There are many reasons for this. From the point of view of the damage mechanism, there are mainly the following points.
Erosion of slag. The components of refining slag are mainly CaO, SiO2 and AL2O3. The high temperature treatment time is long, the slag alkalinity is high, the composition fluctuation range is large, sometimes the CaF2 amount is large, the slag viscosity is very low, and the slag line is highly aggressive.
The effect of high temperature. During the heating of the LF, the temperature in the electrode zone is quite high. Due to the deviation of the positioning of the ladle into the station or the influence of the electrode operation, the slag line part forms a hot spot area, and the combined action of the slag seriously damages the slag line.
The effect of decarburization of slag bricks. During the turnover process, the refined ladle has a long baking time and a slow turnover. The surface layer of the slag line brick is easy to be oxidized and decarburized, causing looseness of the structure, decreasing strength and being incapable of scouring. At the same time, the decarburized layer is prone to slag penetration, erosion and thick formation. The metamorphic layer causes the structure to peel off.
