Summarization of the control method of the large dent defect of the slab
In the production of continuous casting, slab depressions occur from time to time, which not only affects the qualification rate of the slab, but also causes production accidents in severe 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 fan-shaped section. The situation of the big depression is:
The large depressions of the slab are generated in the sector, the width generally runs through the entire surface, the depth is 5-50mm (or even deeper), and is continuously distributed along the casting direction of the slab. If the length is not processed in time, several shifts can be continued.
The main reason for the large depression of the cast slab is the accumulation of slag in the fan-shaped section. The center of the large depression of the cast slab changes with the slag accumulation in the fan-shaped section and the change of the center position, and the depth of the large depression is deeper closer to the lower mouth of the mold. The key to solving the large depression is to solve the problem of slag accumulation in the fan-shaped section. 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 nozzle clogging, and the poor surface quality of the roller.
1) Strictly implement the online standards for sector segments. Ensure that the opening degree and radian of each segment on the line does not exceed 20, the surface of the roller is smooth and flat, and the roller is free to rotate. In the arc alignment process, multi-point arc alignment is used. After the roller alignment reaches the standard, the arc is rotated on the surface with an included angle of 90 degrees to ensure that the four points of each roller meet the standard requirements. The deformation degree and surface flatness of the offline rollers were inspected, and the rollers that exceeded the standard were immediately scrapped.
2) The fan-shaped section prevents nozzle clogging during use.
3) Reform the rollers, change all the original rollers to water-cooled, reduce the probability of thermal expansion and deformation of the rollers, while ensuring the strength, change the rollers to five-segment grooved rollers to reduce the area of slag accumulation on the rollers and increase The heat dissipation speed of the rollers, while ensuring that the oil path of each roller lubrication point is unblocked and the amount of lubricating oil consumed, and the roller surface is smooth and flat.