The relationship between the selection of release agent and the quality of die-casting
The composition and content of water-based release agents vary, and the initial temperature at which their active ingredients start to adhere to the surface of the mold, also known as the wetting temperature, is different. This means that the initial temperature at which the effective film is truly formed is different. Practice has shown that the type, concentration, mold temperature, spraying method, and quantity of release agent directly affect the quality of die-casting, as shown below.
1. If the atomization is not good or the dispersion is uneven, the vaporization time will be prolonged, and high vapor pressure will be formed after filling, causing membrane looseness.
2. The film is too thick, the film formation is slow, and there are flow marks in the solution, leading to the deposition of gas and surface wrinkles.
3. The film is too thin and the oil film is partially broken, resulting in poor demolding, biting, and marks.
4. The temperature of the mold and the adhesion temperature of the release agent to the mold are not coordinated. Release agents with high adhesion temperatures are less likely to adhere when the mold temperature is low, resulting in slow film formation.
5. The effective adhesion amount of water-soluble release agent is only a fraction. If the mold temperature is too high, most of the effective components will be scattered by the vapor film phenomenon (vapor film phenomenon refers to the phenomenon where the release agent particles that start spraying reach the surface of the mold and form a vapor layer, causing subsequent particles to rebound).
6. Choosing products mainly made of paraffin wax, although inexpensive, may deposit into the mold and potentially clog the nozzle.
7. Choosing products with high blending rates of natural oils and fats can result in poor oxidation stability and mold sticking.
8. Choosing cheap release agents can easily generate bubbles, which can corrode molds and workbenches due to the influence of surfactants and fatty acid additives.
9. Choosing a release agent containing silicone oil is suitable for medium to thick walled parts, but due to different types and formulations of silicone oil, problems often arise during post-processing (such as surface coating).
Based on the summary of the experience of using water-based release agents in some specialized die-casting factories, the appropriate methods for selecting and using release agents are:
1. Try to find out the optimized dilution ratio and spray amount.
2. To protect the mold, a good and less sprayed release agent should be selected.
3. To reduce the deposition residue on the mold, do not use products with excessive paraffin wax.
4. Different types of release agents should be selected based on the size, wall thickness, complexity, and process of the castings.
5. Pay attention to the blowing and chip removal process to ensure the removal of residual release agent every time.
6. Mold temperature control: It is recommended to open the mold at 300-450 ℃; Pick up items at 280-430 ℃; Start spraying release agent at 200-280 ℃; Film formation at 180-350 ℃; Blow air to remove debris at 150-300 ℃.
