What are the common quality defects and causes of aluminium sheet rolls?

In the production process, the aluminum sheet and strip go from ingot to hot-rolled coil and then to the cold-rolled coil. Accordingly, it will be rolled and processed by different equipment, such as hot rolling mill, cold rolling mill, rewinding, annealing, shearing and bending, and straightening. The manufacturer needs to have strict production implementation guidelines in each step so as not to cause different degrees of product quality defects during the production and flow of the product.

Below we have listed some of the standard quality defects and analyzed the causes.

Non-metallic press-in


Non-metallic debris pressed into the surface of a plate or strip. The surface is apparent dotted or extended yellow-black defects.


Main causes:

  • Rolling process equipment conditions are not clean.
  • The rolling process lubricant is not clean.
  • Process lubricant injection pressure is not sufficient. The surface of the slab has scratches.



Due to objects between the prism and face, or face and face contact occurs after the relative sliding or misalignment and in the plate, strip surface caused by the distribution of bunches (or groups) of scars.


Main causes:

plate, strip in the process of production and guide road, equipment contact, relative friction and caused by abrasions;
cold rolled volume end face is not flush, in the vertical furnace annealing flip when the wrong movement, layer and layer between the abrasions;
cold rolling tension is not appropriate, uncoiling between the layers of the wrong movement and abrasions;
finishing acceptance or packaging operations improperly produced between the plate sliding and caused by abrasions.

If you would like to know how we avoid such problems in the production of Aluminium Sheets you can get in touch with our product specialists.



Aluminium plate, aluminum coil and other objects collision in the plate, strip surface, or end surface generated by the scratch, and most in the depression edge has been extruded metal presence.


Main causes:

Aluminium plate, coils in the handling or storage process and other objects collision produced; plates, coils in the annealing material frame or chassis with other protruding objects top bump and produced.

Warped edge


Aluminium coil after rolling or shearing, the edge of the strip warps.


Main causes:

rolling with too much pressure; rolling with uneven distribution of lubricating oil; improper adjustment of shearing edge when shearing.

Fold injury


Deformation creases arising from bending of the plates or sheets.


Main causes:

Improper feeding when loading the multi-roller straightening machine, unbalanced forces in turning or handling of thin plates, unbalanced forces when loading stacked plates.

Collapsed roll


Aluminium coil core seriously deformed, roll shape not round.


Main causes:

Improper tension in the curling process, external compression, low strength of the roll core, no roll core coil produced by annealing.

If you would like to know how we avoid such problems in the production of Aluminium coils , you can get in touch with our product specialists.



Irregular misalignment between layers of strip end face and layers, resulting in uneven end face.


Main causes:

Uneven billet. Improper control of mill unrolling and winding tension. Uneven amount of press down, sleeve crosstalk. Improper adjustment of flattening roller. Abnormal alignment system during winding. Bad parallelism of roll system.

Tower Shape


Aluminium coils between layers and layers to one side to form a tower deflection.


Main causes:

Bad incoming Aluminium hot plate shape and improper tension control. Coiling alignment adjustment control system abnormal. The tape head is not firmly bonded when coiling.

Aluminum coil loosening


Aluminum coiling, uncoiling between layers and layers produce loose, serious when the wave and the whole volume.


Main causes:

Uneven or too small tension in the winding process; pressure roller pressure is too small when uncoiling; steel strip or card is not strong, produced when lifting.

“V” type defects on the end surface


Aluminum coil with a local “V” type defects on the end surface. This defect is produced in the process of winding or after uncoiling, some to be placed after a period of time to produce.

"V" type defects on the end surface

Main causes:

The tape coiling process before and after the use of improper tension; expansion circle is not round or rolled when the bottom is not round, after unloading due to uneven distribution of stress; poor quality of the core.

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