Aluminum Alloy Vacuum Die Casting Housing Paint Process

Vacuum Die Casting Process: An advanced die casting process that eliminates or significantly reduces the porosity and dissolved gas in the die casting by adding vacuum equipment during the die casting process and removing the gas in the die casting cavity, thereby improving the mechanical properties and surface quality of the die casting.

Workpiece advantages:

1. Eliminate or reduce the porosity inside the die casting, improve the mechanical properties, mechanical properties, surface quality of the die casting, improve the product surface appearance finish;

 

2. Reduce the back pressure of the cavity, can use lower specific pressure and poor casting performance of the alloy, the same tonnage of the die-casting machine can achieve larger castings;

 

3. Improved filling conditions, can die casting thinner castings.

General workpiece painting process:

(1) Oil removal → water washing → rust removal → water washing → table conditioning → water washing → phosphating → water washing → drying → spraying → baking;

(2) Purpose and importance of pre-treatment:

The purpose of pre-treatment is to make the casting get a good coating, because the production of die casting in the manufacturing, processing, handling, preservation period will have grease, oxide rust, dust rust and corrosion on the surface, if not pre-treatment will directly affect the performance of the spray, appearance, so the pre-treatment in the coating process occupies a very important position. The most important of these; The two key processes are:

1. surface adjustment is short for surface adjustment: acid (or alkali) solution to remove excess alkali (or acid) on the surface of the rust removal process, adjust the PH as far as possible to neutral, that is, pH =7; Function: speed up the phosphating speed, refine the phosphating crystallization, increase the crystallization point of phosphating;

2. Phosphating: Phosphating is the central link of pre-coating treatment. The metal workpiece is treated with orthophosphate solution of manganese phosphate, zinc and cadmium to form an insoluble phosphate protective film on the surface of the die-casting workpiece. The resulting phosphating film has a dense structure with small holes, which increases the surface area of the die-casting workpiece and can increase the contact area of the coating. The favorable mutual penetration between the phosphating film and the coating can greatly improve the adhesion of the organic coating to the workpiece. The phosphating film formed by phosphating is a stable non-conductive isolation layer, which changes the metal surface from a good conductor to a bad conductor, inhibits the formation of microbatteries, and effectively prevents coating corrosion. The common methods of phosphating are divided into high temperature phosphating (70~90℃), medium temperature phosphating (50~70℃) and normal temperature phosphating (20~30℃) according to the treatment temperature.

3.Spraying points: Through the treatment of the die-casting workpiece, spray the good paint to bake into a film (generally including the primers, topcoats and varnishes three parts to ensure the appearance of the film effect and 100 cells salt spray test)