Secondary-cooling water starting method for reducing head-slab scrap rate of extra-thick slab

Abstract

The invention discloses a secondary-cooling water starting method for reducing the head-slab scrap rate of an extra-thick slab and belongs to the technical field of steelmaking and continuous casting. The thickness specification range of the applicable continuous casting slab ranges from 300 to 600mm while the width specification range of the same ranges from 1600 to 3000mm. The secondary-cooling water starting method includes that after continuous casting is started and a slab head enters from a first secondary cooling zone (1) to a fifth secondary cooling zone (5) during secondary cooling, a traditional secondary-cooling water starting mode is adopted, namely starting secondary-cooling water the moment when the slab head enters the starting position of the zone; after the slab head enters a sixth secondary cooling zone (6) and enters the starting position in the zone, water of the zone is not started immediately; when the slab head moves forward for 1 to 5 meters in the zone, the secondary-cooling water in the zone is started; the distance between the starting position of the sixth secondary cooling zone (6) and the upper opening of a crystallizer is from 7 to 10 meters, and a seventh secondary cooling zone (7) to a fourteenth secondary cooling zone (14) and the sixth secondary cooling zone (6) adopt the same mode to start the secondary-cooling water. By the secondary-cooling water starting method, cooling intensity of the head slab can be reduced, straightening temperature and high-temperature thermoplastic can be improved, and the scrap rate of the head slab due to generation of transverse cracks on the surface of the head slab can be reduced. The secondary-cooling water starting method has the advantages that the process is easy to implement.

Description

technical field [0001] The invention belongs to the technical field of steelmaking-continuous casting, and provides a secondary cooling water start-up method for reducing the rejection rate of extra-thick slab heads; the applicable continuous casting slab thickness specification range is 300-600mm, and the width specification range is 1600-600mm. 3000mm. Background technique [0002] For extra-thick slab continuous casting, due to the thicker slab thickness, low casting speed, long residence time in the casting machine and high cooling intensity, the surface temperature of the slab is relatively low when it is straightened. According to previous studies, there is a brittle range of steel between 600-900°C, and the high-temperature thermoplasticity of the slab surface drops sharply. If straightening is carried out in this temperature range, surface transverse crack defects are prone to occur. [0003] The front end of the slab is the billet head, generally about 400-1000mm, ...

AI Technical Summary

Problems solved by technology

The part closely connected to the billet head is called the billet head, and its length is determined by the length of the cast billet, generally about 2000-4000mm. Due to the low casting speed, the temperature of the billet is usually low during straightening, and surface transverse cracks are prone to occur Defects are generally treated by peeling, but for extra-thick slabs, there will still be surface transverse crack defects after 3-4 times of peeling, and they have to be rejected due to insufficient thickness. The quality of the first slab is large, and the rejection of the first slab will cause a large waste for the steel mill. Therefore, the problem of reducing the rejection rate of the first slab for extra-thick slabs needs to be solved urgently

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