Aluminum Alloy Die Casting Production Process

Aluminum alloy production process is simple, convenient operation, high efficiency, easy to realize automatic production. Aluminum alloy die casting machine of molten metal directly from the pressure chamber into the cavity, metal consumption is less, temperature fluctuation range is small, die casting process is stable. Die casting metal liquid with closed channel into the cavity, impurities are not easy to carry, die casting quality is good. At the same time, due to the low specific pressure of die casting, the pressure chamber, punch, water spout, etc. Long-term immersion in molten metal, easy to corrode, affecting the service life, easy to corrode. Increase the iron content in the alloy. For magnesium alloy and other flammable low melting point alloy die casting, can be sealed pot, through the inert gas to protect the alloy liquid, to prevent its oxidation or combustion. At present, hot chamber die casting machine is mostly used for zinc alloy and other low melting point alloy casting die casting, but also used for small aluminum and magnesium alloy die casting.

The basic structural elements of die casting include wall thickness, reinforcement, casting holes, casting rounded corners, pulling mold slope, threads, gears, grooves, rivet head, relief, mesh, text, logo, pattern, embedded castings and so on. Die casting reasonable wall thickness depends on the specific structure of the casting, alloy properties and die casting process and many other factors. Practice has proved that, under normal circumstances, the mechanical properties of die casting with the wall thickness increases and decreases. Thin wall castings have higher tensile strength and density than thick wall castings, while thin wall die castings have better wear resistance. As the wall thickness of the die casting increases, defects such as air holes and porosity shown in b) also increase. Therefore, under the premise of ensuring that the die casting has sufficient strength and stiffness, a reasonable wall thickness should be designed to be thin and uniform. Otherwise, the internal structure of the die casting will be uneven, will also increase the difficulty of the implementation of the die casting process. Under normal process conditions, die casting wall thickness not more than 4.5mm, large wall thickness and small wall thickness ratio) is not more than 3 * 1. For thick-walled die casting, in order to avoid loosening and other defects, should be thinner wall thickness and add patch.

Dimensional accuracy of die casting: dimensional accuracy is one of the key features of the manufacturability of die casting structure, it affects the die casting mold design and die casting process. Die casting can achieve the dimensional accuracy is relatively high, its stability is also very good, which mainly depends on the manufacturing accuracy of die casting mold. There are many reasons for the dimensional deviation of die casting, including the deviation of chemical composition of alloy itself, temperature of working environment, fluctuation of shrinkage rate of alloy metal, stability of motion state and so on. The opening of the mold to extract the core and push out the mechanism, as well as the use of the process of the mold. Errors caused by wear and tear, the deviation of die-casting process parameters, die-casting machine precision and rigidity caused by the error, the number of times and service life of the mold repair, etc. These reasons are intertwined and affect each other, such as alloy shrinkage, depending on the shape of the die casting, die-casting process parameters, alloy type, the wall thickness of the die casting. Therefore, it is necessary to study the relationship between the above conditions and the shrinkage rate in order to determine the actual shrinkage rate.

The selection of linear dimensional tolerance grades for die castings is shown in Table 4-7 and Table 4-8. The tolerance band should be symmetrically distributed, i.e., one half of the tolerance is positive and the other half is negative. If asymmetric setting is used, it should be indicated on the drawing. For dimensions that are generally not machined, the hole takes a positive value and the shaft takes a negative value; for dimensions that are to be machined, the hole takes a negative value and the shaft takes a positive value.