[Alloy] Characteristics of commonly used die-casting materials

Die-cast alloys are divided into two categories: cast steel alloy materials and non-ferrous metal alloys. Cast steel alloys are not commonly produced in China due to problems such as high melting points, easy oxidation, molds, and low service life. Non-ferrous alloys include low melting point lead alloys, Tin alloy, zinc alloy, high melting point aluminum alloy, magnesium alloy, copper alloy, etc. Among them, aluminum alloys are relatively more widely used, and magnesium alloys have been increasingly used this year.
01 Zinc alloy
In the history of die-casting development, die-cast zinc alloy once occupied a very important position. Its advantages include low melting point, low pouring temperature, convenient melting and heat preservation, and long service life of the mold. It has good die-casting performance and good flow performance. It can die-cast die-casting parts with thin wall thickness, which makes up for the problems caused by high density. Quality impact; the crystallization temperature range is small, easy to form, not easy to stick to the mold, and easy to demould; the shrinkage rate is small, it is easy to ensure the dimensional accuracy of die castings; the comprehensive mechanical properties are high, especially the pressure resistance and wear resistance. Good; the surface of zinc alloy die-casting parts can be subjected to various anti-corrosion and decorative treatments, such as chemical treatment, anodizing, electroplating, electrostatic spraying, vacuum chromium plating, etc.; within the pouring temperature range, zinc alloy has no effect on the pressure chamber and die-casting mold parts. corrosive effect.
Die-cast zinc alloy also has problems, and its aging phenomenon is serious. Over time, zinc alloy die castings will cause deformation or changes in dimensional accuracy, and significantly reduce strength and plasticity. At the same time, when the operating temperature changes, its mechanical properties also change. If the working temperature is lower than -10°C, its impact toughness will drop sharply; if it is above 100°C, its strength will also drop significantly and creep will easily occur. Therefore, the ambient temperature range when zinc alloy die castings are used is narrow.
02 aluminum alloy
The performance and process performance of aluminum alloys are superior to other alloys. And it is rich in sources, so it occupies an extremely important position in die-casting production. Its advantages are low density, high specific strength and specific stiffness; it has good mechanical properties at both high and normal temperatures, especially impact toughness, good electrical conductivity and thermal conductivity; and its mechanical cutting performance is also very good. ; There is a layer of chemically stable and densely organized aluminum oxide film on the surface, which has good corrosion resistance. It has a large specific heat capacity and latent heat of solidification. Most cast aluminum alloys have a small crystallization temperature range. The structure often contains a considerable amount of eutectic. Its linear shrinkage is small, so it has good filling performance and small size. Thermal cracking tendency. However, cast aluminum alloys still have a considerable volume shrinkage and are prone to generate large concentrated shrinkage cavities at the final solidification point. In addition, aluminum alloy has a strong affinity with iron and is easy to stick to the mold, so it should be die-cast on a cold chamber die-casting machine.
03 magnesium alloy
The biggest advantage of magnesium alloy is that its density is small, which is only equivalent to 1/4 of iron and about 2/3 of aluminum. However, its strength is close to that of aluminum alloy, its specific strength is higher than that of aluminum alloy and steel, and its specific stiffness is higher than that of aluminum alloy and iron. Quite frankly, for some lightweight devices that are easy to carry, using magnesium alloy can greatly reduce the mass of the parts. Therefore, using magnesium alloy to die-cast these parts is almost the only option.
The low melting point of magnesium alloy results in small low-temperature deformation and high dimensional accuracy, which is conducive to one-time mold opening and forming; it has low affinity with iron and small adhesion to the mold, which is conducive to improving productivity and mold life; and magnesium alloy has good flow The performance is conducive to the production of complex and small parts; magnesium alloy has good sound and vibration reduction properties, which is beneficial to improving the stability of automobile driving, and is widely used in the automobile industry. With the booming development of the automobile industry, especially the rapid increase in demand for light-duty vehicles, a broad market has been provided for magnesium alloy die-casting production.
Magnesium is a flammable substance. Magnesium dust will burn on its own, and magnesium liquid will react violently and cause an explosion when it comes into contact with water. Therefore, necessary safety protection measures need to be taken when performing magnesium alloy die casting. For example, the crucible is sealed and filled with protective gas to melt the magnesium alloy in a closed and protected state.
The above is a brief introduction to the three more common die-casting alloys.