Method and device for deceasing transverse corner cracks of casting blanks

Abstract

The invention relates to a method and device for decreasing transverse corner cracks of castling blanks. The method includes the steps of S1, disposing a smoke hood above a conveying roller way for cut casting blanks to collect high-temperature air; S2, delivering the collected high-temperature air under pressure; S3, delivering the high-temperature air to air nozzles disposed in a second casting blank cooling area and at corners of the casting blanks; and S4, allowing the high-temperature air to pass through the air nozzles to cover the corners of the casting blanks. The device comprises the smoke cover (3), a first heat-resistant pipe (4), a booster fan (5), a second heat-resistant pipe (6), heat-resistant branch pipes (7) and the air nozzles (8). The high-temperature compressed air can be blown to the corners of the casting blanks to prevent excessively fast cooling of the corners of the casting blanks, so that the corners of the casting blanks can be kept at the temperature higher than the upper limit of a low-temperature brittleness area before entering a straightening area, precipitation of various carbo-nitrides from the corners of the casting blanks is avoided, corner plasticity of the casting blanks is improved and transverse cracking of the corners of the casting blanks is effectively prevented during straightening.

Description

Technical field [0001] The invention relates to the technical field of continuous casting of steel, and more specifically, to a method and a device for reducing transverse cracks at the corners of a cast slab. Background technique [0002] The continuous casting process of steel is a process in which molten steel continuously transfers and releases heat in a continuous state, and gradually solidifies into a certain shape cast slab. In this process, the cast slab passes through a mold (also called a cold zone). ), two cooling zone and air cooling zone three cooling zones, among them, the second cooling zone is composed of multiple cooling sections with different spraying amounts, the surface of the cast slab is directly cooled by water spray or aerosol, there will be in the shell Because of the large temperature gradient, and the bending and straightening of the slab in the second cold zone, it will cause mechanical stress and deformation of the slab. Therefore, once the temperatu...

AI Technical Summary

Problems solved by technology

The existence of transverse cracks at the corners will not only increase the degradation and scrapping of the slab, but more seriously, it will lead to abnormal structure at the edge of the steel plate, poor compactness, and reduced impact toughness and strength.

[0004] Under the existing technology, there are two main ideas to solve the transverse cracks at the corner of the slab: one method is to increase the surface temperature of the slab in the bending or straightening area to make it higher than the upper limit of 700-900°C in the brittle trough area , to avoid the precipitation of carbonitrides and improve the plasticity of the slab. However, because the corners are in a supercooled state, the lowest temperature is more than 200°C lower than the center temperature of the slab. Therefore, under the existing secondary cooling conditions, it is almost impossible to use The temperature at the corner of the slab in the straightening zone is higher than 900°C. Therefore, even if the above method is used to weakly cool the slab in the secondary cooling zone, it is difficult to greatly improve the transverse cracks at the corner of the slab. Corner cracking of steel is a common problem, and if the cooling of the slab is too weak, in order to ensure that the slab is completely solidified before cutting, the casting speed of the slab will be limited, which is not conducive to the improvement of continuous casting productivity; the second method It is to reduce the surface temperature of the slab so that it is lower than the lower limit of the brittle trough temperature of 700-900°C in the bending or straightening area, which can also improve the plasticity of the slab, but this will increase the cooling intensity and make the cracks more severe. Sensitive steel grades have crack defects due to rapid cooling shrinkage stress, so they are not suitable for crack-sensitive steel grades such as micro-alloyed steel. The hot charging and hot delivery of the slab, therefore, this process route is rarely used in the actual process

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