1 Thermomechanical corrosion loss
The first thing the ladle slide gate plate produces during use is thermomechanical corrosion. The temperature of the slide gate plate before use is very low. During pouring, the inner hole of the slide gate plate suddenly comes into contact with high-temperature molten steel (1600℃) and suffers strong thermal shock (the temperature change is about 1400℃). ), therefore, a tensile stress exceeding the strength of the sliding plate is generated outside the casting hole, resulting in the formation of radial micro-cracks centered on the casting hole.
The appearance of cracks is conducive to the diffusion, accumulation and penetration of foreign impurities, and accelerates chemical attack. At the same time, the chemical corrosion reaction promotes the formation and propagation of cracks, and this cycle will gradually expand and damage the casting holes of the sliding plate. Moreover, the scouring of high-temperature molten steel will damage the refractory materials at the friction part of the steel, and cause spalling and block loss.
2 Thermal chemical attack
Thermal chemical erosion is another major cause of slide gate plate damage. Refractory materials for slide gate plate come into contact with high-temperature molten steel and slag during use, and a series of chemical reactions occur, causing chemical corrosion. According to the different chemical damage mechanisms of different steel grades to the slide gate plate, and then according to different use conditions, choose the slide gate plate of the corresponding material, which can increase the service life of the slide gate plate and reduce the cost of refractory materials.
The chemical mechanism of the damage of Al₂O₃-C and ZrO₂-Al₂O₃-C:
(1) Oxidation of carbon. There are two main ways to oxidize graphite and carbon: one is that the oxygen in molten steel, especially high-oxygen steel, oxidizes carbon to form pores, and then iron penetrates into the pores and makes the surface of the sliding plate adhere to the molten steel; the other is that oxygen in the air oxidizes carbon. After the low-melting material is generated from the plain and molten steel, the low-melting material continues to corrode and penetrate along the pores.
(2) Decomposition of mullite. After use, mullite decomposes to varying degrees, transforming into columnar and crystalline corundum crystals, forming a porous structure, destroying the original dense eutectic structure composed of mullite and clinoperite, making the structure Porosity, deterioration of the organization, greatly reduced strength and corrosion resistance, and accelerated the damage of the slide gate plate.
(3) The erosion of (Mn) and (Fe) on the sliding plate. The SiO₂ in the slide gate plate reacts with FeO and MnO in the steel and slag to form a low-melting mineral phase 2FeO·SiO₂ (1205℃) and MnO·SiO₂ (1291℃).
(4) (Ca) Damage to the slide gate plate. Al₂O3·SiO₂ reacts with CaO in steel and slag to form low melting point 2CaO·Al₂O₃·SiO₂ (1327℃) and 12CaO·7Al₂O₃ (1392℃).
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