Summary of control methods for large depression defects in slabs

In the production of continuous casting, billet dents occur from time to time, which not only affects the qualification rate of the billet, but also causes production accidents in serious cases. There are two main types of slab depressions: one is the "small depression" generated in the mold; the other is the "large depression" generated in the sector. The large depressions are:
1. Appearance
The large depression of the billet occurs in the sector, the width generally runs through the entire surface, the depth is 5-50mm (or even deeper), and it is continuously distributed along the casting direction of the billet. If the length is not processed in time, it can continue for several shifts.
2. Reason
The main reason for the large depression of the slab is the accumulation of slag in the sector. The center of the large depression of the slab changes with the slag accumulation in the fan-shaped section and the change of the center position. The key to solving the big depression is to solve the problem of slag accumulation in the sector. The reasons for the accumulation of slag in the sector are: the deformation of the roller in the sector, the inappropriate opening of the sector, the deviation of the arc of the sector, the blockage of the nozzle, and the poor surface quality of the roller.
3. Measures
1) Strict on-line standards for sector segments. Ensure that the opening degree and radian of each segment of the upper line are not more than 20, the surface of the roller is smooth and flat, and the roller can rotate freely. In the process of arc alignment, multi-point alignment is adopted. After the roller alignment is up to the standard, the surface with an included angle of 90 degrees is rotated and then aligned to ensure that the four points of each roller meet the standard requirements. The deformation degree and surface flatness of the offline rollers are tested, and the rollers that exceed the standard are found to be scrapped immediately.
2) During the use of the sector, the phenomenon of nozzle blockage is avoided.
3) Transform the rollers, change all the original rollers to water-cooled, reduce the probability of expansion and deformation of the rollers due to heat, and change the rollers to five-stage groove rollers while ensuring the strength, reduce the area of ​​slag accumulation on the rollers and increase the The speed of heat dissipation of the rollers, while ensuring the smooth oil passage of each roller lubrication point and the consumption of lubricating oil, the surface of the rollers is smooth and flat.