The edge cracks found on the SS400 steel plate are unilaterally distributed on the steel plate after cutting the edge, mainly appearing between 10 mm and 100 mm from the edge of the steel plate, and generally extending along the longitudinal direction of the steel plate. In the whole batch of steel plates, 16 The products with thickness specifications of mm and 25 mm have the largest number of cracks. From the crack shape, the shape of the edge cracks of SS400 steel plate is not very regular, the length is different, and there are many longitudinal cracks, and some of them are also distributed horizontally.
The distribution of cracks on the surface of the SS400 steel plate is basically the same as that of the cracks on the surface of the continuous casting slab, especially the distribution of longitudinal cracks. The cracks on the surface of the continuous casting slab are all generated when the molten steel solidifies in the continuous casting mold After reaching the secondary cooling zone, the previously formed cracks will be extended and expanded again. During the heating process of SS400 steel plate, oxidation and decarburization are carried out at the same time. If there are surface cracks in the continuous casting slab during the heating process, it is easy to produce oxides and decarburization around the cracks. If the crack is generated during the rolling of SS400 steel plate, the crack can only be slightly oxidized, and it is impossible to produce decarburization and oxide inclusions.
From the perspective of crack macroscopic appearance, the crack shape of SS400 steel plate is mainly distributed in the longitudinal direction, but there are also some small transverse cracks. It can be seen that it is not caused by rolling. When scratch cracks are generated during rolling, the cracks usually follow the rolling direction. The distribution and directionality are very obvious, and the existence of cracks in the transverse direction can further explain that the cracks in the SS400 steel plate are caused by the slab.
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