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What are the main causes of damage to sliding plates&nozzles (2)

[2019-12-13]

2.1 Chemical Erosion of Ca-treated Steel
In the process of producing aluminum-killed steel and silicon-killed steel, in order to improve the pourability of molten steel, Ca-Al wire and Ca-Si wire are fed into the molten steel during the refining process for Ca treatment. When producing this type of steel, the erosion part of the skateboard shows a clear "horse-shoe" shape. The main reason is that Ca and CaO in molten steel react with Al2O3 and SiO2 in the skateboard to form a low melting point compound, especially when the skateboard is in the pouring state. The molten steel flowing in the slide hole is easy to form a negative pressure band. Under the effect of the negative pressure band, the Ca vapor and the inhaled oxygen directly react to form CaO, which is concentrated in this area, resulting in a "horse-hoof" -shaped erosion.

2.2 Chemical erosion of high Mn steel
When pouring high manganese steels such as pipeline steel, the reaming of the slide plate is serious, and the maximum reaming amount can reach 5mm / furnace. In addition, the erosion of the contact surface of the slide plate is also serious, accompanied by spalling and cracks on the surface contact surface. The phenomenon. This is due to the following chemical reaction between MnO in high manganese molten steel and Al2O3 and SiO2 in the slide MnO + SiO2 = MnO.SiO2, MnO + Al2O3-MnO.Al2O3 Corrosion and zircon mullite, the main materials that are resistant to erosion and thermal shock in skateboards, are decomposed, which intensifies the erosion of molten steel and causes an abnormal expansion of the pore diameter.

2.3 Chemical attack of slag
In the late stage of ladle pouring, due to the suction effect of molten steel flow, a part of the steel slag will be drawn into the water outlet, which will cause slag erosion on the slide. Its main characteristics are reaming and erosion of the plate surface. In addition, there are also cracks intensifying. The composition of steel slag is relatively complicated, mainly including CaO, SiO2, Al2O3, MgO, MnO, FeO, Cr2O3, CaF2, etc., most of the oxides can form low melting compounds with Al2O3 and SiO2 in the skateboard. It may also react with the original carbon in the slide, causing decarburization, loosening the surface structure of the slide and causing damage.

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