Brief introduction to the application of mold temperature machine in die casting process:
After the molten alloy is pressed into the mold cavity, it solidifies due to the loss of heat. If the heat transfer rate is too fast, there may be a disadvantage of cold streaks in the casting. On the contrary, if the heat transfer rate is too slow, it will increase the forming cycle of the casting and reduce the productivity. The control of mold surface temperature is very important for producing high-quality die castings. The temperature of the mold can affect the flow of molten metal on the surface of the mold cavity, especially for thin-walled parts with long flow paths.
In order to fill the mold cavity with molten metal before solidification, in addition to selecting a design that shortens the filling time, it is also possible to increase the gate speed (but is prone to turbulence) and increase the mold temperature. In addition, castings with large areas and extremely high surface requirements also require a higher and stable mold surface temperature to reduce cold lines and surface defects.
Uneven or inappropriate mold temperatures can also lead to dimensional instability of castings, resulting in deformation of the ejected castings during production, resulting in defects such as thermal pressure, mold sticking, surface depressions, internal shrinkage cavities, and hot bubbles. When mold temperature differences are large, they have varying degrees of impact on variables in the production cycle, such as filling time, cooling time, and spraying time. In addition, the life of the mold can also lead to thermal cracking of expensive steel due to the impact of supercooling and overheating.
Suitable surface temperature of mold temperature machine
The appropriate mold surface temperature distribution must be determined based on the shape of the product, such as surface requirements such as thickness, changes in cross-sectional thickness, and production cycles. The general appropriate temperature is:
Approximate surface temperature of alloy mold
Aluminum alloy 180-270 ℃
Magnesium alloy 180-300 ℃
Zinc alloy 100-200 ℃
To achieve the required mold temperature, die casting technicians often use petroleum gas guns, followed by radiation heaters, or plug-in electric heating tubes, but the effect is not ideal, and the mold temperature is not uniform. However, the use of radiation heaters is more flexible, causing less damage to the mold, but with lower efficiency; The plug-in electric heating tube is only suitable for long-term heating locations, and its application range is relatively limited. In addition, it is also very common to directly heat the mold with molten metal by using the low speed injection method, which reduces the primary injection speed. However, this method has a negative impact on the life of the mold and is not suitable for expensive precision molds. Due to the instantaneous stage of injection, the temperature of the molten liquid will invade the surface of the mold cavity, with a depth of about twice the casting thickness of the mold thermometer. During periods of intense penetration of high heat, the high temperature condition of the mold cavity surface will cause high stress to occur on the mold cavity surface, doubling the chance of relative microcracking.
The most ideal heating method for mold heaters should be hot oil heating. The hot oil continuously flows through the pipes inside the mold to heat the mold from the inside, so that the mold reaches a state suitable for production. Due to the heat transfer oil's ability to not only heat but also cool like water, it functions like a heat exchanger and can maintain the mold temperature within a certain range, even when production is interrupted.