Thermal state and properties of steel ingot under conditions of endogenous vibration treatment of the melt during crystallization

Abstract

In connection with the need to reduce the negative impact of the main defects of the forging ingots, the changes in their thermal state due to endogenous vibrational processing of the melt during crystallization are studied. Vibration processing of an ingot of steel 40XH weighing 7.6 tons was carried out in the upper part for 13 min after the completion of casting of steel at a frequency of 50 Hz and an amplitude of 1.5 mm. Based on the results of temperature measurements of the side surfaces in the upper, middle and bottom parts of the vibrated and control ingots, the regression equations were obtained for the change in their thermal state during crystallization for 200 minutes. A regular increase in temperature was established under conditions of endogenous vibration processing up to 30 °С in the upper part of the ingot with its gradual decrease over 100 minutes, and in the middle part by 10-15 °С over 50 minutes. In the bottom part, no temperature differences were noted during the first 25 minutes. In the next time interval, the temperature of the research ingot steadily decreases by 35-50 °C compared with the control. The obtained results indicate an increase in temperature in the upper part of the experimental ingot due to endogenous vibration treatment of the solidifying melt and a regular redistribution of temperature fields along the height of the ingot. An increase in the temperature gradient in the indicated volumes of the ingot as a result of endogenous vibration processing leads to an increase in convection and mixing of the melt, advancement of the crystallization front mainly in the direction of the upper part, the formation of a fine-crystalline structure and a greater length of the bottom cone without contamination with non-metallic inclusions, a decrease in the manifestation of axial segregation and an increase in mechanical properties metal ingot. The use of endogenous vibration treatment of steel ingots during their crystallization is a promising technological solution that opens new opportunities for controlling the processes of crystallization and structure formation, improves the quality of metal properties of large forged ingots.

Keywords

• ingot
• steel
• vibration treatment
• crystallization
• temperature