Release agent, also known as mold release agent, is a solvent used to lubricate molds during alloy casting and plastic product molding, causing the workpiece and mold to detach. However, its performance is affected by the mold temperature, so there is often a blind spot in selecting a suitable mold temperature range release agent during operation among die-casting operators.
However, in the process of die-casting production, release agents are largely used as an important means of mold cooling (in the die-casting production process, it is often heard that workers say, "If the temperature is too high, spray more water", "If the mold is pulled, spray more water", etc.). Many companies use water-based release agents. During spraying, compressed air carrying the release agent is sprayed onto the surface of the mold cavity. At the same time, the high temperature of the mold indirectly heats the release agent, causing the moisture in the release agent to evaporate. However, due to the uneven temperature distribution on the surface of the mold cavity, the degree to which the release agent is heated by the mold varies (the amount of residual moisture is different, and the gasification effect is also different). The degree of cooling of the mold by the release agent also varies, so the thickness of the liquid release and lubricating film formed on the surface of the mold cavity by the release agent also varies.
In the hot zone of the mold, the release lubricant and its moisture are more affected by the mold temperature, resulting in gradient evaporation. If there is a large temperature difference between the hot zone and the surrounding cold zone of the mold cavity, the tension gradient formed on the surface of the mold cavity will be greater. When the release agent is disturbed by external factors such as temperature and concentration, and the liquid film of the release agent becomes thinner, it will flow from the thin part of the liquid film (high temperature zone of the mold) to the relatively thick part of the liquid film (low temperature zone of the mold) under the tension on the surface of the mold cavity (this process is similar to the cooling and solidification process of liquid metal in the mold cavity). If the spraying amount is increased at this time, the hot zone of the mold cavity will be completely covered by the release agent, resulting in the accumulation of too much release agent and moisture in the low-temperature zone of the mold cavity, leading to the formation of pores, cold insulation, or color spots in the die cast part. Therefore, many experienced die-casting operators choose different methods of "spot spraying" to overcome this phenomenon. On the contrary, as the spraying amount is reduced, the hot zone of the mold cavity is not covered by the liquid film of the release agent, which affects lubrication and detachment effects, such as mold pulling and clamping. This shows how much the temperature of the mold affects the effectiveness of the release agent. Maintaining a balanced and generally consistent mold temperature is crucial for the performance of the release agent.
If the surface temperature of the mold is too high or too low, it will affect the adsorption effect of the mold release agent on the mold.
A、 Too low:When the temperature is below 150 degrees, the spraying process causes the mold temperature to drop below the vaporization point of water. The coating only rushes through the surface of the mold cavity and cannot deposit on the surface of the mold cavity. Excessive water and coating accumulation in the mold cavity will cause diffuse porosity in the casting.
B、 Too high:When the temperature exceeds 398 degrees, the coating will be dispersed and washed away by the vapor on the surface of the mold cavity during spraying. Because the temperature has not dropped to the wetting temperature, only when it reaches this temperature will the mist coating come into contact with the surface of the mold cavity and form a demolding liquid film.
For a relatively constant mold temperature, factors affecting film formation include droplet impact, wetting of the mold surface, spreading to form a continuous film, and preventing subsequent spray erosion. In addition, there are many uncertain factors that affect the formation of the film. Including the speed and intensity of spraying, as well as the angle of spraying that has already been formed. The primary purpose of release agent is to form an effective film inside the mold cavity, followed by achieving effective mold cooling and minimal residue.
There are constantly new release agents on the die-casting consumables market, which have solved some old problems. With the continuous innovation of die-casting peripheral technology, we attach more importance to mold temperature control and monitoring, and the tools and equipment used are more advanced, making it more convenient, scientific, and reasonable for us to choose release agents.
