Discussion on Gravity Casting of Aluminum Alloy Mould

Time : 2019-02-16 Author : Advanced Share :  
      Advanced equipment is an indispensable factor to ensure product quality, but the role of die in casting is also very important. Especially for aluminium alloy automotive parts manufacturers, the accuracy and durability of the die have a significant impact on the quality of the product.

  In ferrous metal casting, the mould is mostly for the formation of mould cavity. Generally, the mould itself does not directly contact with liquid metal, especially for the complex shape of non-metallic mould casting parts. The contact with hot metal liquid is the moulding material, mainly the moulding sand, which makes the moulding material become the main factor affecting the quality of castings. Aluminum alloy gravity casting is different, because of its low melting point and good casting performance. In mass production, the shape of the castings is usually directly formed by the die, such as the engine's aluminium alloy cylinder block, cylinder head, etc. This is not only conducive to improving labor productivity, but also more importantly, by adjusting the temperature distribution at different parts of the die, the structure and crystal of the castings can be controlled. Particle size improves the quality of castings, avoids the environmental pollution caused by the large use of moulding materials, and improves the working conditions of the workshop.

  The gravity casting die of aluminium alloy varies with the complexity of casting shape. Even for the same part, different casting processes often lead to different die forms, but in any case, gravity casting die for aluminium alloy still has its commonalities.

  Firstly, proper casting process must be selected. The quality of casting process is directly related to the quality of castings and the yield of the process. Some domestic mould factories have begun to use solidification simulation to assist casting process design. Through computer simulation of filling and solidification process, the hot-solidification parts which are prone to casting defects are found and overcome. This is very important and effective for improving the reliability of casting process design and preventing unnecessary rework of mould in debugging process.

  Secondly, the mould should have good heat capacity. Thicker dies and modules that meet the requirements are not only the effective guarantee of die life, but also play a very important role in regulating the temperature field during the continuous working process of dies. In order to reduce costs, save materials and blindly reduce the effective thickness of dies in order to reduce the weight, some die factories do not know that this not only greatly reduces the service life of dies, but also makes castings easy to deform, affecting the dimensional accuracy of castings. Seriously, it will lead to mass scrap of castings, causing losses to foundries, and even more seriously, it will damage the sound of the die factories themselves. Reputation.

  Thirdly, the mould should have a more reliable cooling system and air extraction system. Cooling not only can effectively improve labor productivity, but also can adjust the temperature field of castings and control the cooling rate of castings, thus affecting the internal structure and grain size of castings and achieving the purpose of effectively controlling the mechanical properties of castings. As the name implies, air extraction is to artificially drain the gas inside the cavity to the outside of the cavity to reduce the possibility of porosity defects in castings. At the same time, the die temperature of a small area can be adjusted by adding exhaust plug, which plays an important role in preventing and overcoming cracking and shrinkage of aluminium alloy.

  Fourthly, it is necessary to have a die positioning device matching the casting machine and a convenient die installation system. The positioning device is not only the key to ensure the size of castings, reduce the slit and burr, but also the key to ensure the normal operation of the casting machine. It can be said that if there is no good positioning device for the mould, there will be no good qualified castings. Mould must be easy to install and disassemble, because aluminium alloy gravity casting, every certain time must be dismantled to re-spray paint and repair the mould, if disassembly is not convenient, it will inevitably increase the labor intensity of workers, occupy more labor time, reduce production and efficiency.

  For foundries, high quality die means high quality castings, which means lower cost, higher output value and profit.

  At present, the domestic mould industry is developing very fast. There are no more than hundreds of aluminum alloy gravity casting mould manufacturers. With the development of automobile manufacturing industry and the influx of foreign capital, both the scale and technical strength of mould manufacturers are increasing day by day. With the popularization and application of NC processing equipment, there is no big gap between the processing level of mould industry and that of foreign countries. Many moulds The factory also has more advanced testing equipment, but our management level, design concept and management concept are far behind those of foreign counterparts. Mold materials and heat treatment strengthening methods are far behind those of developed countries. At present, for the foundry mould factory, there is a lack of practical experience, engineers and technicians who know both the mould manufacturing and the foundry technology, and the debugging and process verification of the mould is a necessary step in the process of the production of the mould, because the successful mould and mature technology are the hope of many foundry factories with weak technical force today.

  The standardization of dies and the application of standard parts of dies are the inevitable trend of the development of die industry in the future. This is especially true for gravity casting of aluminium alloys, which started late. Only when the standardization of dies is carried out can the behavior of die manufacturers be standardized and it is possible for die manufacturers to provide high quality, low cost and standard dies. At the same time, the standardization of the mould and the application of the standard parts of the mould will make it easier for foundry to monitor the quality of the mould and make the maintenance and maintenance of the mould more convenient. The use of standard die parts and the effect of production scale will help to change the current situation of low production efficiency in the die industry with many varieties and small batches, and help to reduce costs and improve productivity.

  In short, precise size, high production efficiency, easy to use and maintain is the eternal pursuit of the die and casting industry.

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