The purposes of mechanical pretreatment
The common used approaches of mechanical pretreatment
To provide favorable expressional conditions and raise the quality of surface finish;
To level up the products;
To reduce the impact of welding;
To create the ornamental effect;
To acquire a clean surface.
The common used approaches of mechanical pretreatment include polishing、sandblasting、brushing、rolling, etc. What kind of specific approach to be used is according to the types、production methods、initial status on surface、final finishing level s of the products.
The principles and functions of chemical polishing
High—speed glaze—wheel rubs with the workpiece to produce high temperature, which means that plastic deformation occurs on the metal surface where will be smoothed its convex—concave points. In the meantime, the paper—thin oxide film produced immediately on the metal surface around the atmosphere by oxidation is to become increasingly polished through repeated ablation. Its main functions is to remove the surface defects such as burrs、scratches、corrosion spots、sand holes、porosities. At the same time, trying a further attempt at cleaning the slight uneven workpiece surface to make it have higher glossiness , until getting the mirror effect.
The principles and functions of sand—blasting
Using purgative compressed air to spray to the surface of aluminum products with dry sand flow and other abrasive particles aims to remove the surface defects to have an even unglazed sand surface. Its main functions are that it removes burrs、slag of casting the other defects as well as dirt on the workpiece surface; it can improve the mechanical properties of alloys and obtain the even matting effect on the surface.
The principles and functions of brushing
Brushing is to use the revolving brush of brush wheel to wipe off the flaws such as burrs and dirt on the product surface. To aluminum alloy, it is in wiredrawing processing, whose fundamental purpose is for ornament.
The principles and functions of rolling finish
Rolling finish tells that puts workpiece into a roller which contains abrasive material and chemical solution, and to have the aid of its pinning to make workpiece and abrasive material as well as workpiece and workpiece rub with each other to gain the polishing effects.