Wear mechanism of refractory materials for ladle lining
As is well known, understanding the wear mechanism of refractory materials is the basis for selecting refractory materials and designing lining. However, in practical situations, the specific wear mechanism will vary depending on the function of the working lining position, the material system used in that area, and the actual operating conditions. This only discusses the wear mechanism of the slag line and bottom of the main refractory materials used in two important areas of the ladle. Further focusing on this topic, only two main practices have been introduced here, namely the use of magnesia carbon bricks for slag lines and the use of spinel castables at the bottom.
1. Wear mechanism of main refractory materials for slag line
It can be said that the damage to the slag line is a common reason why the ladle cannot be used and needs to be repaired or re lined. Generally speaking, the usage conditions of steel ladles are somewhat similar to those of converters, but worse, mainly due to the larger range of oxidation and temperature fluctuations. Carbon oxidation and slag erosion are two important reasons for the damage of magnesia carbon brick lining during use. In fact, these two factors interact strongly and sometimes it is difficult to say which one is more harmful than the other. The wear mechanism of magnesia carbon lining includes two aspects: material erosion of magnesia carbon bricks includes two aspects: one is the melting loss of magnesia sand particles by slag, such as SiO2, CaO oxides and MgO forming low melting materials, which are carried away by slag. The second reason is that FeO in the slag oxidizes C in the magnesia carbon brick, causing the brick structure to become loose. In addition, during the refining process of molten steel, chlorine blowing and stirring are carried out, and the mechanical erosion of molten steel and steel slag exacerbates the damage to the slag line. In addition to chemical erosion, physical factors such as vertical cracks and brick joints often cause slag erosion, resulting in early damage to the slag line and limiting its service life.
2. Wear mechanism of the main refractory material at the bottom
The damage to the bottom of the ladle, especially in the impact area, may be the second reason why the ladle cannot be used and needs to be repaired or re lined. The typical feature is that the higher the height of the ladle, the more severe the wear of the refractory material in the bottom area. Other relevant factors may include tapping temperature and furnace height. Fuurtal et al. have provided a detailed introduction to the main wear mechanism of spinel castables used at the bottom, and Vert has provided more detailed information. There are three main stages:
(1) The formation of spider like vertical cracks on the bottom hot surface during the early stage of furnace life was caused by thermal peeling, temperature gradient, and steel tapping;
(2) The infiltration of molten steel and slag into the hot surface at the bottom, especially through vertical cracks formed on the surface;
(3) Structural cracking is caused by subsequent thermal cycling, resulting in the structural cracking of alternating hot surface areas and the formation of a new refractory material surface. Once the surface of the newly formed refractory material is exposed to the molten steel and slag, the second and third stages will be repeated.
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