Inspection items and polishing methods for die-casting parts

The inspection of die-casting parts is generally determined by both the supply and demand parties, and the routine inspection items are:
1) The appearance quality of die castings should be smooth and free from cracks, porosity, bubbles, and any penetrating defects.
2) The chemical composition and mechanical properties of the die-casting specimen should comply with the provisions of GB/T15115.
3) The geometric shape and dimensions of die castings should comply with the casting drawings, and the dimensional tolerances should comply with the provisions of GB/T6414.
4) Items that other users need to verify.
The commonly used polishing methods currently include the following
1) Electrolytic polishing
The basic principle of electrolytic polishing is the same as that of chemical polishing. But compared to chemical polishing, electrolytic polishing can have a negative reaction effect and achieve good results.
2) Acoustic polishing
Acoustic polishing is the use of special waves to vibrate zinc alloy products and mold suspensions placed in the acoustic field, allowing the abrasive to mold the surface of the product and achieve a polishing effect. And special wave polishing will not cause product deformation due to polishing, resulting in scrapping. However, the equipment for acoustic polishing requires more investment and installation, making it difficult and not suitable for single use. Combined with chemical polishing and spot polishing, it can enhance the product’s capabilities.
3) Mechanical polishing
Mechanical polishing is a polishing method that involves removing micro protrusions from the surface of a product by cutting, resulting in a smooth surface. Mechanical polishing generally uses polishing wheels, vibration grinders, or other grinding equipment. The polishing wheel is generally made by stacking multiple layers of canvas, felt, or leather, with metal circular plates clamped on both sides. The rim of the wheel is coated with a polishing agent composed of a uniform mixture of micro abrasive and grease.
Polishing is a manually operated polishing wheel that rotates the pressure of die-casting products, causing the abrasive to roll and micro cut the surface of the workpiece, resulting in a smooth surface. When using non greasy matte polishing agents, it can dull the appearance of bright surfaces. Nowadays, most factories have adopted vibration grinding machines to replace polishing wheels for zinc alloy die-casting products, which can be polished in batches. The surface smoothness of the polished products is high, saving manpower, material resources, and financial resources.
4) Chemical polishing
Chemical polishing is the use of chemical media to dissolve the micro protrusions on the surface of die castings, resulting in a smooth product surface. The main advantage of this method is that it does not require complex equipment and requires less investment in polishing equipment; Easy to operate; Can polish workpieces with complex shapes; And it can be batch polished to improve polishing speed. Zinc alloy products that use chemical polishing can have a bright exterior and good performance, and are easy to perform electroplating, spraying, and other processes.
5) Magnetic abrasive polishing
Magnetic abrasive polishing is the use of magnetic abrasives under the action of a magnetic field to form abrasive brushes for grinding the surface of die castings. The magnetic grinding and polishing processing speed is relatively good, and the zinc alloy die-casting products have good quality, and the working environment is good.
How to Maintain Die Casting Crafts
1) If distilled water needs to be used for washing, distilled water can also be heated, and neutral soap can be used. Ammonium hydroxide, acids, white powder, gauze, etc. cannot be used. If there is a large cleaning, it can be cleaned by personnel.
2) The room for storing aluminum handicrafts should be kept dry, free from dust and air pollution, and the relative humidity should be below 50%.
3) The original method for aluminum crafts that have been cleaned is to apply a layer of chemical protective agent or apply a layer of paraffin after heating. The modern method is to apply a layer of silicon seal to prevent the influence of gas and moisture.
4) Dust on die-casting handicrafts should be removed with a soft cloth, brush, or duster.
5) The utensils were contaminated with dirt before being stored, and it is good that they have been chemically protected. Do not apply thick fats or oils to handicrafts, wear gloves when touching handicrafts, do not touch them with sweaty hands, or use oily paper or boxes for packaging.
6) Regularly observe changes in aluminum handicrafts, and promptly deal with any symptoms of aluminum disease that occur. The method can be cleaned with sodium bicarbonate (5% sodium carbonate+sodium bicarbonate) until it contains no chloride ions.
7) Aluminum cannot be placed together with zinc, please remember when storing it.
8) To prevent mechanical damage to objects, do not overlap them. Each handicraft should be placed in a brocade box.
Because metal aluminum and aluminum alloys have good flowability and plasticity, as well as casting and processing machines, die-casting and aluminum castings can achieve various complex shapes, high precision and smoothness, thereby reducing the mechanical processing ability of castings and the adhesion of metal aluminum or aluminum alloy castings.

Post time: Aug-16-2023