Reasons of refractory materials damage in working layer of ladle lining
The ladle lining is divided into working layer and permanent layer, and different material systems and construction methods are adopted according to the difference of erosion mechanism between the bottom and the wall of ladle. For the working layer of ladle lining, deoxidization, desulfurization, decarburization, degassing, fine adjustment of alloy composition, removal of non-metallic inclusions and inclusion denaturation treatment, and temperature control of molten steel are required in the refining treatment. Different refining methods have different degrees of damage to the ladle working layer.
Here are the specific causes of damage:
For the the working layer refractory materials of ladle lining, they are mainly subject to two types of erosion. One is chemical erosion. For example, the chemical reaction between silicon dioxide and refractory lining changes the ladle lining into slag, which leads to the damage of refractory. The other is oxidation. Oxidation is a special form of corrosion of refractories in ladles, in which carbon in refractory bricks reacts with iron oxide or oxygen in the air and is eroded. Corrosion occurs in all parts of refractories, especially in the slag line.
Scouring is the second cause of refractory materials damage in the working layer of ladle lining. Physical damage is caused by physical wear or erosion of molten steel or slag flowing through the refractory surface. For ladles with eccentric bottom tapping, molten steel has great influence on the impact zone of molten steel at the bottom of ladle, nozzle slide plate and permeable brick higher than the bottom of ladle.
Peeling is subject to the stress on the lining caused by the rapid cooling and heat of the refractory materials. When the stress exceeds the strength of the refractory materials, cracks are generated inside the refractory materials. As these cracks expand, intersect, and penetrate, the fragments of the refractory materials will partially or completely peel off. This phenomenon generally occurs on the nozzle block and the permeable block.
Hydration is also a form of refractory damage. The ladle work lining adopts a fire mud wet-laying process in the masonry, and the water or water vapor reacts with the MgO in the magnesia carbon bricks to hydrate before and during baking. The hydrated refractory materials have poor resistance to steel slag and molten steel, and physical and chemical properties are weakened, resulting in accelerated erosion of the ladle lining.
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