The causes of transverse folding defects in cold rolled coils are briefly described

After pickling, cold rolling, degreasing, recrystallization annealing and leveling, cross folding defects sometimes occur. The transverse folding defect of cold rolled coil generally occurs on two sides of the length direction, the shape is a horizontal stripe of 90 or 45 degrees in the direction of the rolling line (sometimes it will form a nail or petal print), the spacing is between 10 ~ 100㎜, and the length is between 20 ~ 200㎜; The horizontal folding printing is obvious to the naked eye, and serious ones will have a certain feel. Transverse printing defects have adverse effects on the surface, mechanics and process properties of the product, and users may even crack during the stamping process; To further improve product quality; It is necessary to understand the cause of transverse folding of cold rolled coil.

Shanghai cold rolled coil manufacturers to take you to understand what is the main cause of horizontal folding defects?

1. The formation mechanism of the transverse folding is actually that the yield is generated when the cold rolled coil is annealed. First, when the cold rolled coil is flat, due to the uneven distribution of tension, the local tension is too large to cause yield. The second is that the yield strength of the cold-rolled coil decreases after annealing, and transverse folding defects will occur even under normal tension and pressure conditions. The former reason: due to the formation of bonding during annealing of the cold rolled coil, the tension is unstable when the flat uncoiling or the problem of the flat equipment itself, resulting in the uneven distribution of the tension of the cold rolled coil. The latter reason may be that the yield strength of the cold-rolled coil itself does not meet the technical requirements due to technical reasons during annealing.

2, hot rolled coil in cold rolling, because the shape is not well controlled, resulting in edge waves and middle waves, rolling tension is unstable, the tension between layers and layers is different, easy to form interlayer bonding after annealing, cold rolled coil surface will produce transverse folding defects when flat.

3, when the cold rolled coil is annealed in the cover annealing furnace, such as the temperature is too high or the temperature is too fast, the convective plate plane is worn, and the bond between the layers will be generated, and the transverse folding defects will be produced.

4, according to the relevant information and our company's production experience, the temperature before the steel coil formation is greater than 45 degrees, will produce a large number of horizontal folding defects. The main reason is that under this temperature condition, the metal molecules are active, and it is easy to jump from the elastic deformation zone to the plastic deformation zone when subjected to external forces, resulting in a slip line on the strip surface, resulting in transverse folding.