Abstract: In order to improve the comprehensive mechanical properties of the twin-roller cast-rolling strip, the concept of vibratory cast-rolling is proposed to refine the grain size of the strip. For the purpose of verifying the grain refinement effect of the vibratory cast-rolling technology and exploring its mechanism, twin-roller strip cast-rolling comparative experiments of 20CrMn steel under the condition of vibratory and non-vibration are carried out at two casting temperatures of 1 570℃ and 1 530℃respectively. Then the microstructure and mechanical properties of the strips obtained from the experiments are tested and analyzed. The microstructure observation result shows that the mechanical vibration can effectively refine the grain of the cast-rolling strip. The mechanism of grain refinement is that the vibration can promote the rupture of dendrite in the vibratory side so as to increase the nucleation rate in the molten pool in the solidification stage and can promote the dynamic recrystallization of the plastic deformation zone in the rolling stage. Tensile test result shows that mechanical vibration effectively improves the mechanical properties of the cast-rolling strip.At the casting temperature of 1 570℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively 12.11%, 14.57%, 38.9% higher in the rolling direction and 7.72%, 13.23%, 34.8% higher in the vertical-rolling direction than that of the conventional cast-rolling strip.At the casting temperature of 1 530℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively 9.22%, 14.95%, 31.25% higher in the rolling direction and 21.36%, 27.35%, 42.86% higher in the vertical-rolling direction than that of the conventional cast-rolling strip. The results show that vibration casting-rolling can not only increase nucleation rate and refine grain size in solidification stage, but also enhance dynamic recrystallization effect by vibration in rolling section, improve microstructure of material and enhance mechanical properties.

Key words: cast-rolling, grain refinement, mechanical property, recrystallization, vibration