Common quality defects and causes of aluminum plate and coil

Non-metallic stamping
Definition: non-metallic debris pressed into the surface of plates and belts. The surface shows obvious spots or long strips of yellow and black defects.

Main reasons: rolling process equipment conditions are not clean; rolling process lubricant is not quiet; process lubricant injection pressure is not enough; the surface of the slab has scratches.

  • Scratch Definition: A bunch (or a group) of scars distributed on the surface of the plate or belt due to the relative sliding or misalignment of the edges and surfaces between objects, or due to the contact between surfaces. Main reasons: Wear caused by contact and relative friction between plates and belts and guides and equipment during processing and production; misalignment of the end surfaces of cold rolled coils during annealing and turning in a vertical furnace, resulting in misalignment and wear between layers. Improper cold rolling tension, open roll interlayer misalignment and wear; sliding between plates due to improper surface treatment acceptance or packaging operations.
  • Abrasion Definition: Scratches on the surface or end face of an aluminum plate or coil after collision with another object, most of which have metal extrusion at the edge of the depression. Main reasons: The plate or roll collides with other objects during handling or storage; the plate or roll is produced by colliding with other protruding objects on the annealing material shelf or chassis.
  • Variable warpage Definition: When rolling or shearing, the edge of the strip warps. Main reasons: excessive rolling pressure; uneven distribution of lubricating oil during rolling; improper adjustment of the knife edge during shearing.
  • aluminum plate
    • 5、Wounders
      Definition: Deformable crease produced when the sheet is bent.
      Main causes: Multi-roller straightening machine feeding error; unbalanced plate in turning or handling force; unbalanced load on the stack.
    • 6. and volume collapse
      Definition: Severe deformation of the coil core and out-of-round coil shape.
      Main causes: Improper tension during crimping; external pressure; low core strength; coreless coils produced by annealing.
    • 7. and Layer Error
      Definition: The end face of the strip is irregular between layers, resulting in an uneven end face.
      Main reasons: Uneven billets; improper control of mill uncoiling and coiling tension; uneven pressure and movement of casing column; improper adjustment of flattening rolls; abnormal alignment system during coiling. Poor parallelism of the roll system.
    • 8, Tower
      Definition: The conveyor belt rolls the layer and the layer to one side, forming a tower shift.
      Main reasons: bad shape of incoming sheet, improper tension control; abnormal roll alignment adjustment control system; poor bonding during wire winding.
    • 9、Loose volume
      Definition: roll-up, open roll layer and loose layer, serious layer and the whole roll-up.
      Main reasons: Uneven or too small tension in the winding process; pressure roller pressure is too small when unrolling; steel strip or clip is not strong and produced during the lifting process.
    • 10、Bird’s nest Definition.
      Strip end face of the local “V” shaped defects. This defect occurs in the rewinding process or after rewinding, some of which occur after a period of time.
      Main causes.
      Strip winding process before and after the use of improper tension; remove the expansion ring, expansion ring is not round or liner is not round, which is due to uneven distribution of stress after unwinding. Poor quality of coil core.


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