Fundição sob pressão de liga de alumínio: 6 técnicas especializadas de polimento

Aluminum Alloy Die Casting: 6 Expert Polishing Techniques

1. Mechanical Polishing

Mechanical polishing is a method of smoothing a surface by removing the protrusions left after polishing through cutting and plastic deformation of the material surface.

This method is normally carried out with tools such as oil stones, wool wheels, sandpaper, etc., with manual operation being the main means of polishing. For surfaces that require high quality, ultra-precision grinding and polishing method can be used.

Ultra-precision grinding and polishing involves the use of specially designed sanding tools that are firmly pressed into the surface of the aluminum alloy casting and rotated at high speed in a polishing liquid containing abrasive particles.

This technology can achieve a surface roughness of Ra0.008um, which is the highest among various polishing methods. This method is often used for optical lens molds.

2. Chemical Polishing

Chemical polishing is a method of obtaining a smooth surface by dissolving the microscopically raised parts of an aluminum alloy pressure casting in a chemical medium.

The main advantage of this method is that it does not require complex equipment, and can be used to polish aluminum alloy pressure castings with complex shapes and polish many parts simultaneously with high efficiency.

The central issue in chemical polishing is the formulation of the polishing solution. The surface roughness obtained by chemical polishing is generally several tens of microns.

3. Electrolytic Polishing

The basic principle of electrolytic polishing is similar to that of chemical polishing, which relies on selectively dissolving the small bumps on the surface of the material to make it smooth.

Compared with chemical polishing, it can eliminate the influence of cathodic reaction and achieve better results. The electrochemical polishing process can be divided into two stages:

(1) The macroscopic leveling dissolution product diffuses into the electrolyte, and the geometric surface roughness of the aluminum alloy casting decreases, Ra > 1 μm.

(2) Microleveling anodic polarization improves surface brightness, Ra<1um.

4. Ultrasonic polishing

The aluminum alloy casting is placed in an abrasive suspension and placed in an ultrasonic field. With the oscillation of ultrasonic waves, the abrasive is used to polish the surface of the aluminum alloy casting.

Ultrasonic processing has small macroscopic forces, which will not cause deformation of the aluminum alloy casting, but the production and installation of tools are more difficult.

Ultrasonic processing can be combined with chemical or electrochemical methods. Based on the corrosion and electrolysis of the solution, ultrasonic vibration can be applied to stir the solution to make the dissolution product of the aluminum alloy pressure casting part detach from the surface, and the corrosion or electrolyte close to the surface be uniform; The cavitation effect of ultrasonic waves in the liquid can also suppress the corrosion process and facilitate surface polishing.

5. Fluid Polishing

Fluid polishing relies on the high-speed flow of liquid and its transported abrasives to brush the surface of the aluminum alloy casting to achieve polishing. Common methods include abrasive jet machining, liquid jet machining, and fluid dynamic grinding.

Fluid dynamic grinding is driven by hydraulic pressure, causing the liquid medium carrying the abrasives to flow back and forth over the surface of the aluminum alloy casting at high speed.

The medium mainly uses special compounds (polymeric substances) with good fluidity at low pressure and mixed with abrasives. Abrasives can be made from silicon carbide powder.

6. Magnetic grinding and polishing

Magnetic grinding and polishing is a method of using magnetic abrasives to form an abrasive brush under the action of a magnetic field to grind and process aluminum alloy castings. This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions.

With the use of suitable abrasives, the surface roughness can reach Ra0.1μm.

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