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Several common aluminum sheet deformation, what are the causes of aluminum alloy sheet defects?

Last Updated: 2023-06-04

At present, alloy aluminum sheet is widely used in many industries, such as construction industry, industrial manufacturing, transportation, hardware parts and so on.

But the aluminum sheet in the processing and manufacturing process due to the influence of external forces or welding stress, usually prodsuce a certain degree of deformation, these deformations can usually be corrected, and make it meet the prodsuct quality requirements.

Common deformation of aluminum sheet phenomenon

1. Non-metallic press-in

Definition: Non-metal pressed into the surface of the sheet and strip

Characteristics: The surface is obvious dotted or long yellow-black defects


  • Rolling process equipment conditions are not clean
  • The rolling process lubricant is not clean
  • Process lubricant oil spraying pressure is variable
  • Slab surface scratches

2. Metal pressed into

Definition: metal chips or metal fragments pressed into the surface of the sheet or strip

Features: pressed into the object scraped off the size of the depression, destroy the continuity of the surface of the sheet, strip


  • Hot rolling with fewer rolls, cracked edge of the metal chips, strips fall into the sheet surface after pressing
  • Poor quality of the disc shear edge process, resulting in burrs fall on the strip after rolling pressed into
  • After rolling rolls sticky aluminum, its sticky aluminum and pressed in the slab.
  • Hot-rolled guide ruler clamped too tightly, with down the debris falling on the slab after being pressed into.

3. Scratch

Definition and characteristics: Where the sharp things (such as sheet corners, metal chips or sharp objects on the equipment and sheet contact, in the relative sliding caused by a single distribution of scars called scratches.

Causes: guide sheet or into a flat roll with a projection or sticky aluminum; shear process generated scratches; manual inspection of improper lifting.

4. Scuffing

Definition and characteristics: due to the relative sliding or misalignment between the prism and surface contact between the object and the surface of the sheet and strip caused by the distribution of the bundle (or group) of scars called abrasions.

Causes: Mechanical or artificial to make the aluminum sheet between the layer and the layer of misalignment.

5. Bruise (dent)

Definition and characteristics: aluminum sheet, aluminum coil and other objects after the collision in the sheet, strip surface or end surface generated by the scar. The defect occurs in the aluminum sheet, aluminum coil surface or end face, and most of the metal present in the edge of the depression is extruded.

6. Sticky injury

Definition and characteristics: due to excessive pressure between the sheet or strip volume layer caused by the sheet, strip surface is dotted, flaky or strip-shaped scars. Sticky injury is often prodsuced when the upper and lower sheet (or volume layer) showing symmetry, sometimes periodic.

7. Print marks (roller marks)

Definition and characteristics: the existence of periodic depressions on the surface of the sheet and strip. The depression is relatively smooth.

8. Water marks

Definition and characteristics: light white or light black irregular water line traces presented on the surface of the quenched sheet after calendering.

9. Surface stain marks (flower face)

Definition and characteristics: sheet, with the surface of the occurrence of gloss and color uneven stains.

10. Surface bubble

Definition and characteristics: irregular round or strip-like cavity projections on the surface of the board and strip. The edges of the bumps are rounded and smooth. The sheet is asymmetrical on the top and bottom and irregularly distributed.

11. Corrosion

Definition and characteristics: sheet, strip surface contact with the surrounding media, after a chemical or electrochemical reaction in the sheet, strip surface defects. Corrosion sheet, strip loss of metallic luster. In severe cases, the surface prodsuces gray-white corrosion prodsucts.

12. Salt traces of nitrate

Definition and characteristics: heat treatment nitrate medium residue in the surface of the sheet and the resulting scars. Nitrate marks are irregular white patches, rough surface, no metallic luster.

13. Oil spot

Definition and characteristics: oil residue on the sheet, after quenching the formation of the yellow-brown degree of different spots.

14. Cracks (surface cracks)

Definition and characteristics: Cracks on the surface of the sheet or strip at right angles to the direction of calendering.

15. Cracked edge

Definition and characteristics: sheet, strip edge rupture, serious when jagged.

16. Slip line

Definition and characteristics: Stretching sheet surface, and stretching direction is about 45 ° angle of the regular dark lines.

17. Side bending

Definition and characteristics: the longitudinal side of the sheet, the strip presents to one side of the bending of the non-straight state.

Causes: the mill is not the same amount of pressure at both ends; sheet, strip material thickness on both sides is not the same.

18. Ripple

Definition: sheet, strip due to uneven deformation and the formation of a variety of different unevenness of the sum of the phenomenon.

Characteristics: In the edge is called edge wave, in the middle is called middle wave. Both of them are called compound waves. Neither in the middle nor in the edge is called two-bars wave.

19. Clad aluminum layer misalignment

Definition: hot-rolled clad aluminum sheet offset or lateral swing and the formation of surface defects of the strip sheet.

Characteristics: The defect is a neat dark band along the edge of the sheet. After heat treatment is dark yellow strip traces.

20. Delamination

Definition and characteristics: due to uneven deformation. In the center of the sheet ends and edges prodsuced by the sheet surface parallel to the layer of cracks called delamination.

21. Slag delamination

Definition and characteristics: The cross-section of the sheet prodsuces strip cracks parallel to the surface of the sheet, extending in the direction of calendering, with irregular distribution.

22. Sticky aluminum

Definition and characteristics: Roll and sheet, strip surface due to poor lubrication performance and caused by the sheet, strip surface rough sticky injury.

23. Over-burning

Definition: heat treatment metal temperature reaches or exceeds the low melting point eutectic temperature and prodsuces the unique organization of the phenomenon called overburning.

Features: overburning when the surface shows a significant oxidation color (gray or yellowish), roughness, or dense small bubbles. In the microstructure, there are thickened grain boundaries or intergranular eutectic triangles or eutectic spheres appear in the crystal.

24. Pressed folds

Definition: pressed folds, folds and rolling direction at an angle.

Characteristics: The folds are brightly patterned.

25. Emulsion marks

Definition and Characteristics: A milky white or gray-black dotted or striped mark on the surface of a sheet or strip.

26. Pressed Scratch

Definition and characteristics: The surface damage such as rubbing, scratching, sticking and so on, which is pressed by the rollers.

27. Bending (crease)

Definition and characteristics: sheet bending after the deformation of the crease.

28. Oil sticky

Definition and characteristics: residual process lubricants and other oil in the strip coil, oxidation in the annealing heating process, polymerization to generate a sticky asphalt, affecting the smooth unfolding of the coil.

29. Transverse wave

Definition and characteristics: vertical calendering direction across the surface of the strip sheet ripples.

30. Bright and dark stripes

Definition and characteristics: Uneven organization, or the presence of coarse grains and the presence of the same bright and dark stripes parallel to the direction of calendering.

31. Copper diffusion

Definition and characteristics: Due to the unsuitable heating system, the copper atoms in the base metal of the clad aluminum sheet diffuse to the grain boundary of the clad aluminum layer, forming whisker-like grain boundary, and when diffusing to the surface of the sheet, yellow-brown spots are formed on the surface.

32. Penetrating porosity

Definition and characteristics: The surface of the sheet shows a kind of cavity projection with rounded surface and edges or long strip through the whole thickness of the sheet, with symmetry. The distribution of such bumps is irregular.

33. Rubbing injury

Definition and characteristics: the quenching of adjacent sheets rubbing against each other to prodsuce scars. The rubbing streak is irregular and circular, destroying the natural oxide film and cladding film.

34. Pine twig pattern

Definition and Characteristics: Slip lines prodsuced during rolling

35. Warped edge

Definition and Characteristics: The edge of the strip warps due to rolling or shearing.

The deformation of aluminum sheet during processing, in addition to the above-mentioned reasons, also creates many problems in practical operation, storage, transportation, cutting and processing, so each step of operation is very important.

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