Now, die casting with die-casting alloy materials is very mature widely used. However, there are few large-scale promotion mass production in 6 series pure aluminum die-casting. This process is only carried out in companies with advanced technology perfect personnel. Pure aluminum die-casting is difficult to do. Now it is applied in various heat sinks specific needs, you will think that pressing It is easy to stick the mold in the casting process. In order to carry out pure aluminum die casting, we must first distinguish the difference between the properties of pure aluminum die-casting aluminum materials: density: aluminum is a very light metal, the density is 2.72g/cm3, about 1 / 3 of pure copper. Conductivity thermal conductivity: aluminum has good thermal conductivity conductivity. When the section length of aluminum are the same as that of copper, the conductivity of aluminum is about 61% of that of copper. If the weight of aluminum copper is the same but the section is different (the length is the same), the conductivity of aluminum is 200% of that of copper. Chemical properties: it has good resistance to atmospheric corrosion, because its surface is easy to form a dense alumina film, which can prevent further oxidation of internal metals. Aluminum does react with concentrated nitric acid, organic acid food.
Aluminum has a face centered cubic structure, industrial pure aluminum has a very high plasticity (ψ = 80%), which is easy to bear various molding processes, but its strength is too low, σ B is about 69mpa, Therefore, pure aluminum can only be used as structural material after its strength is improved by cold deformation strengthening alloying; aluminum is non-magnetic, non sparking material with good reflection performance, which can reflect both visible light ultraviolet light; the impurities in aluminum are silicon iron, the higher the content of impurities, the lower the conductivity, corrosion resistance plasticity;
If some alloy elements are added into aluminum alloy, then cold processing heat treatment is carried out, some properties can be greatly improved. The commonly used alloy elements in aluminum are copper, magnesium, silicon, manganese zinc. Sometimes, these elements are added separately, sometimes in combination. In addition to the above elements, sometimes trace titanium, boron chromium are added. According to the composition production process characteristics of aluminum alloy, it can be divided into two categories: cast aluminum alloy deformed aluminum alloy.
Deformed aluminum alloy: this kind of aluminum alloy is usually processed by hot cold pressure, that is, after rolling, extrusion other processes, it is made into plates, pipes, bars various profiles for use. This kind of alloy requires high plasticity, so the alloy content is less. Casting aluminum alloy is to pour liquid metal directly into sand mold to make various parts with complex shapes. Good castability is required for this kind of alloy, i.e. good fluidity. When the alloy content is small, it is suitable to make deformation aluminum alloy. When the alloy content is large, it is suitable to make casting aluminum alloy. The elastic modulus of aluminum alloy is only 1 / 3 of that of steel, that is to say, under the same section the same load, the elastic deformation of aluminum alloy is 3 times of that of steel, the bearing force is strong, but the seismic performance is good. The hardness range of aluminum alloy (including annealing age hardening state) is 20 ~ 120hb. Hard aluminum alloy is softer than steel. The ultimate tensile strength of aluminum alloy is 90Mpa (pure aluminum) to 600MPa (super hard aluminum), which is far that of steel.
The melting point of aluminum alloy is relatively low (generally around 600 ℃, steel around 1450 ℃). Aluminum alloy has excellent plasticity at room temperature high temperature. It can be extruded into structural parts with very complex cross-section, thin wall high dimensional accuracy. In addition to the appropriate mechanical properties, aluminum alloy also has excellent corrosion resistance, heat conduction, electric conductivity optical properties. It can be seen the comparison that pure aluminum has poor fluidity, good thermal conductivity, high melting point good oxidation resistance. Die casting aluminum: strong fluidity, high plasticity, low melting point, easy surface treatment.
Therefore, in view of these characteristics, the mold must be improved. The mold flow channel is wide the feeding material is gentle. The front back mold of the flow channel are changed to be the same. The feeding inlet is thickened to be no less than 3mm. Depending on the product situation, the feeding channel must be smooth smooth. The exhaust inlet also needs to be thickened to avoid blocking the exhaust. The inlets of the feeding material the exhaust gas the product reduce the direct feeding (the sticking material is easy to block), The core is treated with special anti sticking treatment.