Treatment of porosity and Impurities in Aluminum Alloy Die Castings
Aluminum alloy die castings after welding porosity are more difficult to deal with, mainly impurities too much, precision die-casting company is how to deal with aluminum alloy die casting porosity and impurities? Take a look at the following.
First, the aluminum alloy die casting porosity, sand hole treatment, the most effective way to use the new ceramic filter material, do not use the secondary scrap material, reduce impurities.
Second, the reasons for the analysis: 1. The main reason for the hole is caused by shrinkage and contraction, porosity are mostly round, while the majority of shrinkage is irregular shape. 2. The porosity root cause: metal liquid in the red type, solidification process, due to gas intrusion, resulting in the casting surface or inside the round hole; paint volatile gas generated by the round hole; alloy liquid gas content is too high, solidification Precipitation will also produce round holes; shrinkage of the reasons: a, alloy liquid solidification process, due to the size of the final solidification site can not get the metal liquid shrinkage, and the resulting shrinkage. B, uneven thickness of the casting or casting overheating, resulting in a part of the solidification slow, the volume shrinkage when the surface of the formation of concave. Due to the presence of pores and shrinkage, the die casting is very troublesome in the surface treatment, the hole may enter the water, when the paint and plating after baking, the hole heat expansion of the gas, or hole water will change the steam, volume Expansion, which led to the casting surface blistering, so in the production of appropriate methods to solve these causes of the bad.
Third, how to solve the aluminum alloy die casting stomata and impurities? 1. Aluminum die casting on the stomata: the key is to reduce the amount of gas mixed into the casting, the ideal alloy flow should be accelerated from the nozzle through the diversion cone and runner into the cavity, forming a smooth and consistent direction of the metal flow , The use of tapered flow channel design, that is, the flow should be continuously accelerated by the nozzle inward gate gradually reduced, can achieve this goal. In the filling system, the mixed gas is due to turbulence mixed with the metal liquid to form pores, from the molten metal into the cavity by the casting system simulation of the process of casting, it is clear that the sharp transition in the runner and the incremental pouring Road cross-sectional area, will make the metal liquid flow turbulence and rolling gas, smooth metal solution is conducive to gas from the runner and cavity into the overflow tank and exhaust slot, out of the mold outside. Use a new ceramic filter material, do not use the scrap material, reduce impurities. 2. on the shrinkage: to die during the solidification process as much as possible at the same time evenly heat, while solidification. Through a reasonable nozzle design, gate thickness and location, mold design, mold temperature control and cooling, to avoid shrinkage generation. For intergranular corrosion phenomenon: the main control of alloy raw materials harmful impurities, especially lead <0.002%. Pay attention to the impurity elements brought by the waste.
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