MFG Guide

Internal cracks generated during straightening of continuous casting slab

In continuous casting production, the limiting factor to increase the drawing speed,

One is that the billet may be deformed in the secondary cooling zone and break out of the crystallization zone;

The second is that the length of the liquid core of the cast slab is further extended to the subsequent stretching and straightening roll zone. Since the casting slab is pulled with a liquid core, the solidified layer at the interface of the solid-liquid two-phase zone in the casting slab is prone to cracks, which seriously harms the quality of the casting slab. At present, the use of compression casting in continuous casting machines is a new and effective technology to solve this problem. The basic starting point of compression casting is: when the billet is straightened, the inner arc is under tension and the outer arc is under pressure. The tensile force of the inner arc causes cracks in the solidification front. For this reason, while the cast slab is straightened, a reverse axial force is applied to offset part of the tensile stress generated by the straightening, so that the tensile stress on the inner arc is reduced, and the compressive stress on the outer arc is increased. Therefore, the deformation of the solid-liquid interface of the inner arc is reduced. With liquid core straightening, there is no need to worry about internal cracks. For example, for a 250mm thick slab, the pulling speed is 1.8-2.0m/min, the internal cracking after compression casting is reduced by 90-95% compared to the unused one, and the pulling speed is increased by 30-50%.

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