There are two modes of vibration in modern continuous casting moulds: sinusoidal vibration and non-sinusoidal vibration. The velocity versus time relationship of sinusoidal vibration is sinusoidal. The up and down vibration time of the sinusoidal vibration mode is equal, and the maximum speed of the up and down vibration is equal. During the vibration cycle, there is always relative motion between the strand and the mold. During the descending process of the mold, there is a small section of the descending speed that is greater than the pulling speed, the so-called negative slip motion, which can prevent and eliminate the bond between the shell and the inner wall of the mold, and can play a role in the cracked shell. healing effect. The acceleration of the sine vibration mode changes according to the cosine law, which is more stable and has less influence. The sinusoidal vibration mode is widely used in continuous casting production. The increase in the drawing speed of continuous casting leads to an increase in the relative movement speed between the mold and the slab when it vibrates upward, especially after high frequency vibration. Due to the increase of the drawing speed, the amount of mold powder is relatively reduced. Since the drawing resistance is proportional to the drawing speed, the bond between the billet shell and the mold wall increases the possibility of steel breakout.
To solve this problem, a non-sinusoidal vibration method is used. The non-sinusoidal vibration mode has the following characteristics:
1. During the positive sliding time, the difference between the vibration speed and the stretching speed of the mold decreases. Therefore, the tensile stress of the green shell acting under the curved meniscus is reduced.
2. During the negative sliding time, the difference between the vibration speed of the mold and the stretching speed becomes larger. Therefore, the pressure acting to increase the green body is beneficial to the demoulding of the green body.
3. The negative sliding time is short, and the vibration marks on the surface of the casting are shallow