| The oscillation of mold and properties of mold slag directly affect the surface quality of slab in continuous casting.It is very important to study the forming process and mechanism of the defects of initial solidifying shell in flux channel for improving the quality of slab and steel products.In this paper,the model of meniscus initial solidifying shell is established,the pressure force of flux channel are calculated,the stress of meniscus initial solidifying shell in process of mold oscillation is analyzed,the mechanism of continuous casting slab oscillation mark formation is clarified,and the influence of mold oscillation and mold slag composition on oscillation mark formation process is expounded according to the testing results of physicochemical properties of mold slag.The main conclusions are obtained as follows:(1)Design 17 sets of continuous casting mold slag.The results show that the viscosity decreases with the increase of basicity of slag.With the content of Al2O3 increases in the slag,the viscosity of slag increases gradually.The increase of Na2O and CaF2 can decrease the viscosity of the slag.When the basicity is less than 0.9,the melting temperature begins to increase with the increase of basicity.With the increase of Al2O3 content,the melting temperature of the slag gradually increases.With the increase of CaF2 and Na2O content,the slag melting temperature gradually decreases.(2)A mathematical model was established for the meniscus of the mold to calculate the distribution of the pressure and friction in the flux channel.The pressure in the flux channel reached the maximum value at 5.1 mm,and the friction force in the flux channel increased rapidly near 6 mm.The oscillation mark was formed at the end of the meniscus by the combined action of the pressure and friction force in the flux channel.(3)With the increase of casting speed,the pressure fluctuation of flux channel decreases,which makes the depression formed on the initial solidifying shell shallow.High oscillation frequency and small amplitude should be adopted for mold oscillation.Non-sinusoidal oscillation flux channel pressure fluctuation is small,can ensure the stability of mold oscillation,conducive to reduce the slab surface oscillation marks.Increasing the width of flux channel can decrease the pressure of flux channel,and decreasing the length of flux channel can decrease the pressure.(4)The maximum positive pressure in flux channel is dropped by increasing the basicity of molten slag.Content increase of Al2O3 can increase the maximum positive pressure and then deepen the oscillation marks;Maximum positive pressure is decreased with the contents of CaF2 and Na2O in molten slag.The utilization of low viscosity slag for reducing oscillation marks. |
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