Aluminum is a common material in our life. Their density is small, so aluminum with the same volume will be lighter than steel, but their strength is large. There is a layer of oxide film on the surface of aluminum as protection, which can well reduce the possibility of corrosion and rust. There are many kinds of aluminum materials, such as patterned aluminum plate, aluminum plate or aluminum coil. Sometimes we find defects on aluminum coil. How is this caused?
1、 Non metallic press in
Definition: non metallic sundries are pressed into the plate and strip surface. The surface shows obvious spot or strip yellow black defects.
Main reasons: the equipment conditions of rolling process are not clean; Rolling process lubricant is not quiet; Insufficient injection pressure of process lubricant; There are scratches on the slab surface.
Definition: bunches (or groups) of scars on the surface of plates and strips caused by relative sliding or dislocation between edges and surfaces or after surface to surface contact.
Main causes: when the plate and belt are in contact with the guide and equipment during processing and production, they produce relative friction and cause scratch; The end face of cold rolled coil is not aligned, resulting in dislocation and scratch between layers during annealing turnover in vertical furnace; Improper tension during cold rolling and scratch caused by interlaminar dislocation during uncoiling; Scratches caused by sliding between plates due to improper finishing acceptance or packaging operation.
Definition: scratches on the surface or end face of aluminum plate and strip after collision between aluminum plate and coil and other objects, and most of them have extruded metal at the edge of the depression.
Main causes: the plate and coil collide with other objects during handling or storage; The plate and coil are caused by the collision of other protrusions on the annealing rack or chassis.
4、 Edge warping
Definition: after rolling or shearing, the edge of the strip is warped.
Main reasons: excessive reduction during rolling; Uneven distribution of lubricating oil during rolling; Improper adjustment of cutting edge during cutting.