- The iron oxide scale is pressed in
The reason is that in the production process, the iron oxide scale on the surface of the steel coil is not cleaned, and the iron scale fragments are formed by pressing into the surface of the strip steel during the rolling process. Such defects are difficult to remove, leave dents on the surface, and accumulate black particles that affect future production and product quality. Factories should strengthen the inspection of raw materials to prevent raw materials with such defects from entering the production process.
- Pickling bubbles
The volume of the pickling bubbles varies, and it is not formed immediately during pickling, but only after heating.
- Pickling brittleness
It is mainly manifested in the obvious reduction of the plasticity, toughness and crack resistance of the steel. Especially the strip steel with internal stress due to cold working deformation is more prone to this defect.
This defect is mainly due to the presence of foreign objects on the surfaces of various rollers in the unit that are in contact with the strip, or the excessive wave shape of the strip causes the strip to contact the guide plate, causing scratches on the surface. We should always check the equipment to avoid such problems
- In order to prevent defects, the following points should be noted: 1. When the rolling process is in an abnormal state and causes low-speed operation or shutdown, acid should be released in time to prevent over-pickling defects in the strip. 2. Use acid and additives with qualified chemical purity, and the composition of pickling solution should be accurate. 3. Update the acid solution in time to prevent the content of impurities and iron salts from being too high.