The vibration parameters of the copper mould tube mainly include amplitude, frequency, vibration waveform, etc. These parameters have an important influence on the quality of the ingot, as follows:
Amplitude
A larger amplitude can make the periodic change of the friction between the copper mould tube wall and the ingot shell more obvious, which helps to prevent the ingot from sticking to the crystallizer wall and reduce the possibility of the shell cracking. At the same time, it is also conducive to the uniform penetration of the protective slag between the copper mould tube wall and the ingot shell, and improves the lubrication conditions.
However, too large an amplitude may cause the vibration marks on the surface of the ingot to deepen, affecting the surface quality of the ingot. Moreover, too large an amplitude will increase the wear of the crystallizer equipment and shorten the service life of the equipment.
If the amplitude is too small, the air gap between the ingot shell and the crystallizer wall cannot be effectively broken, which is not conducive to the penetration of protective slag, and may increase the friction between the ingot and the copper mould tube wall, and easily cause problems such as bonding and steel leakage.
Frequency
A higher vibration frequency can make the vibration of the copper mould tube more stable, which is conducive to forming uniform and fine vibration marks on the surface of the ingot and improving the surface quality of the ingot. At the same time, high-frequency vibration can bring the protective slag into the space between the mold wall and the billet shell multiple times in a short period of time, improve the lubrication effect, and reduce the friction between the ingot and the mold wall.
However, too high a frequency will increase the load of the crystallizer vibration equipment, require higher performance and stability of the equipment, and also increase energy consumption.
When the frequency is too low, the vibration marks on the surface of the ingot are large and uneven, affecting the appearance quality of the ingot. In addition, the amount of protective slag brought in is relatively small, the lubrication effect is poor, and defects may appear on the surface of the ingot.
Vibration waveform
Common vibration waveforms include sine wave and non-sinusoidal wave. Sine wave vibration is a more traditional method, which is characterized by simple vibration law and easy control. However, under high pulling speed conditions, sine wave vibration may cause the relative movement speed between the copper mould tube and the billet to be larger at certain moments, affecting the uniform penetration of the protective slag and the surface quality of the billet.
Non-sinusoidal vibration can flexibly adjust the vibration parameters according to the process requirements. At high pulling speeds, it can better control the relative movement speed between the copper mould tube and the billet, making the consumption of protective slag more uniform, which helps to improve the surface quality of the billet and the lubrication effect of the copper mould tube. For example, the use of non-sinusoidal vibration with a longer negative slip time can allow the billet to have more time to contact the copper mould tube wall during the descent of the copper mould tube, promote the penetration of protective slag, and reduce the depth of vibration marks on the billet surface.
The vibration parameters of the copper mould tube need to be reasonably adjusted and optimized according to the process conditions such as steel type, billet cross-sectional size, and pulling speed to obtain good billet quality.
