Possible surface defects in aluminium sheet and strip rolling (4)

Possible surface defects in aluminium sheet and strip rolling (4)

(12) sticky injury

Definition and characteristics: due to inter-plate or strip coil layer adhesion caused by the plate, the surface of the strip is dotted, flaky or strip-shaped scars. Sticky injury is often produced when the upper and lower plate (or volume layer) is symmetrical, sometimes periodic.

The main reasons: hot state aluminum plate, strip under local pressure; cold rolling rolling process tension is too large, by annealing produced; hot rolling tension is too large when rolling.

(13) Oil stain

Definition and characteristics: plate, aluminium strip surface oily stains.

The main reasons: aluminium plate, strip surface residual rolling oil and dust, aluminium powder or debris mixed formation; rolling oil mixed with high viscosity lubricants.

(14) Corrosion

Definition and characteristics: aluminum plate, strip surface and the surrounding media contact, chemical or electrochemical reaction occurs in the plate, strip surface produced local damage phenomenon. Corrosion plate, strip surface loss of metallic lustre, serious when the surface of the corrosion products produced gray-white.

The main reasons: plate, aluminum strip production, packaging, storage, transport improper, due to climate moisture or water droplets infiltration surface; process lubricants contain water or alkaline; compressed air and thickness gauge contains water.

(15) Oil spot

Definition and characteristics: residual in the aluminum plate, with the oil, after annealing the formation of light yellow, brown, yellow-brown spots.

The main reasons: rolling oil physical and chemical indicators are not suitable; cold rolling blowing bad, too much residual oil, annealing process, the residual oil of oil can not be completely volatile; mechanical lubricants and other high-viscosity oil drops in the surface of the plate, strip, not removed clean.