2. Die casting dimension: the geometry and size of the die castings should conform to the requirements of the casting pattern. Aluminum alloy die casting dimensional tolerance shall be in accordance with the provisions of GB6414, if there are special provisions and requirements, must be marked on the drawing. Dimensional tolerances of die castings do not include casting inclination. When machining die castings, the allowance for machining should be carried out according to GB/T11350 regulations.
3. Surface quality, high dimensional accuracy of castings, low surface roughness: Castings surface roughness should comply with GB6060.1. Castings are not allowed to have cracks, undercastings, porosity, bubbles and any penetrating defects, as well as scratches, depressions, lack of meat and mesh burrs and other defects.
Aluminum alloy die-casting products are mainly used in traffic lights, handles, fishing wheel accessories, outdoor locks, electrical products, communications equipment, kitchenware accessories, motorcycle radiators and horn cover, LED lamp shell, camera materials, radiators, automotive accessories, electronic communications equipment, electronic game machine shell and other industries, some high High-quality aluminum alloy products with high performance, high precision and high toughness are also used in large aircraft, ships and other industries with high requirements.
The technology of aluminum alloy die casting for lower cylinder block is complex.
First, the castings need to be inserted into five cast iron inlays, cast iron inlays to be perfectly embedded in the aluminum alloy castings above, can not occur separation phenomenon.
Second, the thickness of the bottom cylinder body is thinner to 2mm, the thickest part is 24mm, and the distribution is uneven.
Thirdly, due to the difference of wall thickness between the two sides of the mosaic, it is very difficult to fill the liquid aluminum alloy, and it also tests its feeding capacity.
Fourth, aluminum alloy castings are prone to porosity, shrinkage, cracks, shrinkage and other defects, quality control is difficult.
According to the test and analysis, we think that the main points of aluminum alloy die casting technology for the lower cylinder are as follows:
First, a scientific design of the casting system for aluminum alloy die casting parts of the cylinder block, inserts placed in the middle of the lower cylinder block is thin-walled, the upper and lower parts are thick parts, so we choose one-sided casting, so that aluminum liquid can be fed from the bottom side, flow through the middle of the insert to the top.
Secondly, we have used the toothed chilled exhaust block vacuum aluminum alloy die casting technology, toothed chilled exhaust block and vacuum machine can be used together to improve the flow caused by the thin wall on both sides of the problem, to ensure that the casting quality is good.
Thirdly, in order to improve the wettability of liquid aluminum alloy and cast iron inlays, we preheated the inlays, which not only ensured that the cast iron and aluminum alloy were not separated, but also improved the fluidity of liquid aluminum.
After test, the inner structure of the lower cylinder block is compact and has good appearance. In the die casting process of aluminum alloy for lower cylinder block, scientific and reasonable technological parameters are the guarantee to obtain high quality lower cylinder block. We believe that the following process parameters are the key factors affecting casting molding:
First, the temperature of aluminum alloy die casting technology. In the process of aluminum alloy die casting technology, the temperature of molten aluminum should be well controlled, because the temperature is too high or too low can not achieve good casting effect, too high is easy to lead to shrinkage and porosity, too low is easy to lead to poor filling. Generally speaking, the reasonable temperature of molten aluminum should be between 650 and 665 degrees centigrade, and the temperature after spraying should be between 150 and 200 degrees centigrade.
Second, mosaic temperature. When the insert reaches 120 - 140 degrees, the side of the overflow side of the aluminum liquid can improve the internal quality.
Third, aluminum alloy die casting technology is fast, slow injection speed and pressure. The injection speed of fast and slow pressure should be controlled at about 4m/s and 0.22m/s respectively, and the pressure should be controlled at about 70MPa.
Fourth, the quality of aluminum liquid. As the basic material of casting, the quality of molten aluminum determines the quality of casting. Therefore, to ensure the quality of molten aluminum, every package of molten aluminum must be refined degassing treatment to avoid pollution.
Defects of aluminum alloy die casting technology for 3 aluminum alloy lower cylinder block and Countermeasures