In the process of steel coil manufacturing, common defects mainly include scratches, bruises, transverse scratches on the edges, folding (folding edges, corners), etc. These defects not only affect the appearance quality of the steel coil, but may also have an adverse effect on its performance. The following will introduce these defects and their preventive measures in detail.
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Scratches
Producing mechanism:
- Equipment wear: After long-term use, the rolling mill equipment may be worn and fatigued, causing the equipment to deform, and then scratch the surface of the steel coil.
- Inappropriate rolling parameters: If the rolling speed, tension, pressure and other parameters are not properly controlled, the surface of the steel coil may also be scratched.
Preventive measures:
- Regularly inspect and maintain equipment to prevent wear and fatigue.
- Reasonably control rolling parameters and set appropriate parameters according to the characteristics of different materials.
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Bruise
Producing mechanism:
- During production or transportation, the steel coil surface is subjected to external forces such as extrusion and collision, resulting in uneven force on the surface of the steel coil, and depressions or bulges.
- Failure to replace or repair the rollers in time will result in defects on the roller surface, which will be transferred to the surface of the steel coil.
- Improper operation, such as improper forklift handling.
Preventive measures:
- Optimize the rolling process to reduce roller surface defects.
- Surface cleaning, apply a passivation film on the surface of the steel coil to reduce surface corrosion.
- Standardize the operation, and operate in a standardized manner during transportation.
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Transverse scratches on the edge
Producing mechanism:
- During the production process, if the steel coil is not properly controlled during the rolling process, there will be defects and oxidation on the surface after hot rolling, which will have a great impact on the quality of the product when it is cold rolled.
- During the processing, if the machine adjustment test procedure of the cold rolling mill is not enough, and the cold rolling process parameters are not mastered enough, it will also cause the appearance of transverse scratches on the edge.
- During transportation, the steel coil is affected by vibration, friction, etc. If the steel coil is not tightly wrapped or the transport vehicle is traveling too fast, it will cause transverse scratches on the edge.
Preventive measures:
- Strengthen equipment adjustment, master the basic skills of cold rolling processing, and improve the quality of work.
- Strengthen the packaging and fixing of steel coils during transportation, adopt scientific transportation methods, and control the transportation speed.
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Folding (folding edge, folding angle)
Generation mechanism:
- The difference between folding and folding and wrinkling mainly lies in the shape and degree of defects. Folding edge and folding angle are distinguished according to the size of the angle.
- It often appears in the head and bottom edge of the rail, and is straight or serrated.
Preventive measures:
- For soft steel with a carbon content of less than 0.08, the leveling machine should be equipped with tension rollers to reduce wrinkles.
- Strengthen the simultaneous control of the longitudinal and transverse parts of the steel plate to reduce the phenomenon of buckling.
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Comprehensive preventive measures
1. Raw material testing: Strictly screen the raw materials to ensure that there are no obvious defects on their surface.
2. Production process control: Regularly clean and inspect production equipment, and control the hot processing temperature and cooling method of the material.
3. Equipment maintenance: Regularly inspect and maintain the rolling mill equipment to prevent wear and fatigue.
4. Process optimization: Rationally control rolling parameters and set appropriate parameters according to the characteristics of different materials.
5. Surface treatment: Clean and protect the surface of the steel coil to reduce the occurrence of surface defects.
6. Operation specifications: Strengthen employee training, standardize operation procedures, and reduce defects caused by human factors.
Through the above measures, common defects in the steel coil manufacturing process can be effectively prevented, and product quality and service life can be improved.