There are common defects of hot rolling strip steel.
Cracks of slabs aren’t fully cleaned up, thus it forms scars in the rolling; if the slab is overheating, especially chromium stainless steel, easily form scars. There is a large number of non-metallic inclusions on the surface of the billet which is also the cause of scarring.
If the side of the slab has defects to cause the crack side of strip steel.
If the slab stays for a long time under high temperature, that will generate big crack and spalling when rolled. Moreover, there are fine cracks adjacent to the overheated part. Next, these fine cracks in further rolling will become scarring. To prevent slabs from overheating, you should strictly comply with the prescribed heating system, especially soaking time of high temperature.
Debris, indentation, scratches are the most characteristic defects on the surface of hot-rolled stainless steel. Rolled-in debris and indentation are formed due to scar blocks, debris falling on the surface of the strip. Most of the scratches are formed when the lower surface of the moving strip is in contact with the unsmooth guides, rolls with uneven surface and driven rolls. The upper surface scratches are usually caused by the friction between the coil layers. The strip and forming rolls and feed rolls generates friction. The strip surface will produce a lot of short scratches.
Uneven thickness of the strip is related to uniformity of heating along the length of the slab and tension value among stands. The front and back end of the strip is generally thicker than the middle, which is due to the lack of tension at the end of the strip in the continuous finishing mill.
