Sliding nozzle plate（SN plate）used for flow rate control of molten steel, the Al2O3-ZrO2-C material is generally applied. Damage on sliding surfaces which determines the durability of the SN plate called “surface abrasion” is appeared as decarburized whitening, metal adhesion / infiltration and weakened structure. Among the results of previous study on microstructure of sliding surface of SN plate used for various conditions, occurring mechanism of the “surface abrasion” observed on the plate surface used for casting low oxygen steel, in particular Al-killed steel, was reviewed and thermodynamically investigated. Also, as a result of Computational fluid dynamics（CFD）analysis while casting, it was indicated that negative pressure exerted on some parts of the SN plate surface and the negative pressure was closely related to the occurrence of the “surface abrasion”.

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