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Selection of mold release agent for die casting

2020-04-07 16:18:42

The relationship between the selection of mold release agent and the quality of die casting

For the difference of composition and content of water-based release agent, the initial temperature at which the effective component begins to adhere to the mold surface, that is to say, the initial temperature at which the effective film is formed, is different. The practice shows that the type, concentration, temperature, spraying method and quantity of mold release agent directly affect the quality of die casting.

① If the atomization is not good or the dispersion is not uniform, the vaporization time will be prolonged, and a high vapor pressure will be formed after filling, which will cause the film to be loose.

② The film is too thick, the film formation is slow, and the solution has flow marks, resulting in air entrainment and surface wrinkle deposition.

③ The skin film is too thin, and the oil film is partially broken, resulting in bad demoulding, biting and traces.

④ Mold temperature and mold release agent adhesion temperature of mold is not harmonious, mold release agent with high adhesion temperature is not easy to adhere when mold temperature is low, and the formation of skin film is slow.

⑤ The effective adhesion of water-soluble release agent is only a fraction. If the mold temperature is too high, most of the effective components will be dispersed by the vapor film phenomenon (vapor film phenomenon refers to the phenomenon that the particles of release agent that start to spray reach the vapor layer formed on the mold surface will rebound the subsequent particles).

⑥ Choose paraffin as the main product, although cheap, it will deposit into the mold and may block the nozzle.

⑦ The products with high blending rate of natural oil are selected to make the oxidation stability poor and the mould easy to be sticky.

⑧ It is easy to produce bubbles by using cheap film remover, which is influenced by activator and fatty acid additives and has corrosive effect on mould and worktable.

⑨ The demoulding agent containing silicone oil is suitable for medium and large thick wall parts. However, due to different types and formulations of silicone oil, problems often occur in post-processing (such as surface coating, etc.).

According to the summary of the experience of using water-based release agent in some specialized die-casting plants, the proper way to select and use release agent is:

First, we should explore the optimized dilution rate and spray volume.

② In order to protect the mold, the mold release agent with good quality and less spraying quantity should be selected.

③ In order to reduce the deposition residue on the mould, it is not necessary to use the product with too much paraffin.

④ Different mold release agents should be selected according to casting size, wall thickness, complexity and process.

⑤ Attention should be paid to the process of blowing and chip removal to ensure that the residual release agent is removed every time.

⑥ Mold temperature control: it is recommended to open the mold at 300-450 ℃; take the part at 280-430 ℃; start spraying the mold release agent at 200-280 ℃; form the skin film at 180-350 ℃; blow and discharge the chips at 150-300 ℃.