What factors determine the temperature of aluminum die casting die
The temperature of aluminum die casting die shall be determined according to the shape of the casting, the material of the molten metal and other conditions.
As we all know, in continuous casting, the mold temperature rises and falls once every time the injection is made. In such a continuous and repeated lifting cycle, the temperature changes considerably. Therefore, which time temperature is used as the reference point for measuring the mold temperature? The ideal reference point is the surface temperature of the mold cavity before the metal liquid is about to be filled as the control reference of the mold temperature. But it is difficult to measure this temperature. Generally speaking, the surface temperature of the mold cavity after the casting is taken out is taken as the measurement benchmark of the mold temperature, which is called the mold temperature.
For general die-casting dies, it is better to take out the casting in continuous casting and the temperature of the cavity surface is about 40% of the alloy melting point (for example, if the alloy melting point is 600 ℃, the mold temperature is about 240 ℃; if the alloy melting point is 375 ℃, the mold temperature is about 150 ℃). However, the mold temperature of thin-wall castings should be slightly increased; Heavy wall castings should be slightly reduced.
High temperature of molten metal makes it easy to cast. However, if the temperature of molten metal is too high, the gas content will increase, and pinholes and pores will be easily formed; Moreover, the shrinkage cavity increases after filling the mold cavity, and the defects of shrinkage cavity and surface shrinkage pit are easy to occur; What is more serious is that it shortens the service life of the mold and melting batch, increases the melting cost and other adverse factors. In this way, the temperature of molten metal should be low, but it should not be too low, otherwise the fluidity is poor and the casting forming is difficult.
In addition, when the filling process is carried out on a low-power die-casting machine, the temperature of the molten metal should also be higher. For castings where the mold temperature is not easy to rise and inserts such as motor rotors have great resistance to the flow of the molten metal, the temperature of the molten metal should also be higher.
Application technology of release agent for aluminum die casting die
Aluminum alloy die-casting, including aluminum, magnesium and zinc alloy series die-casting products, is widely used in automotive, telecommunications, motorcycles, home appliances and other industries. Mold release agent for aluminum alloy die casting is an auxiliary agent that must be used in the production process. Due to the different volume size, structure complexity and post-processing requirements of products, the requirements for release agent are also different.
The zinc alloy material is heated and melted (aluminum melting point 660.4 ℃), injected into the mold cavity under high pressure in the liquid state, and the top part of the mold is opened for ejection in a short time. In order to ensure the smooth demoulding of products, the mold cavity surface must be sprayed with release agent before injection. The release agent for aluminum alloy die casting must meet the following requirements:
1. Oil. As an effective material for metal to metal isolation, organic silicone oil is an ideal choice. This silicone oil must have the characteristics of high temperature resistance and not affect the post-processing performance (such as aluminum product coating).
2. Water based. Because the mold is in a high temperature state, any solvent based release agent is not suitable. With water as the dispersion medium, the water evaporates rapidly in the high temperature environment, and the effective demoulding material is evenly distributed on the surface of the mold cavity. Uniform film formation, strong adhesion, high temperature erosion resistance, good demoulding performance.
3. Emulsion. Select appropriate emulsifier to emulsify silicone oil to prevent its carbonization at high temperature. To keep the surface of products and mold cavity clean.
4. No corrosion to castings and mold equipment. The wheel Gallery of casting products shall be clear, and the surface shall be smooth without trace, which will not affect the coating. Volatiles are smoke-free, non-toxic, do not pollute the environment and do not damage the health of operators.
What is the performance of aluminum die casting die
1. low density: the density of plastic is small, which is of great significance for reducing the weight of mechanical equipment and saving energy, especially for vehicles, ships, aircraft and spacecraft.
2. high specific strength and stiffness: the good strength of plastic is not as high as that of metal, but the density of plastic is small, so the specific strength（ σ b/ ρ)、 Specific stiffness (e/ ρ) Quite high. In particular, reinforced plastics made of various high-strength fibrous, flaky and powdered metal or non-metal fillers have higher specific strength and stiffness than metals.
3. good chemical stability: most plastics have good resistance to acid, alkali, salt, water and gas. Under normal conditions, they do not react with these substances.
4. good electrical insulation, heat insulation and sound insulation performance.
5. good wear resistance and self lubrication: the plastic has small friction coefficient, good wear resistance, good self lubrication, high specific strength and low transmission noise. It can work effectively in liquid medium, semi dry or even dry friction conditions. It can be made into machine parts such as bearings, gears, cams and pulleys. It is very suitable for occasions with low speed and low load.
6. strong bonding ability.
7. good forming and coloring performance.