Aluminum Melt Refining And Optimization Of The Die Casting Process Parameters Of An Aluminum Alloy Cylinder Body For Motorcycle

As the core component of engine, cylinder body for motorcycle required high quality. Currently, the cylinder body for motorcycle usually made of aluminum alloy cylinder body and cast iron cylinder sleeve. Compared with the cast iron cylinder body, it had a lower weight, a larger thrust weight ratio, a fewer fuel consumption and a stronger heat dissipation. Aluminum alloy cylinder body had a significant high productivity due to the use of die casting. However, science the gas and inclusions in molten melt, the high speed flows in the mold filling and the fast solidification rate during die casting, it was easily lead to many defects such as pore, shrinkage, slag inclusion and so on in case of unreasonable refining process and die casting process parameters. These defects often lead to leakage and the surface porosity of the cylinder body, seriously affect product quality or lead to waste product. By analyzed the causes of leakage and the surface porosity of the cylinder body, the effect of refining process and die casting process parameters on the porosity defects of aluminum alloy cylinder body was investigated.In this paper, based on the original refining process (innocuous refining flux+fusing agent), in order to improve the effect of purification of molten metal, refining device made an improvement which was changed from bell jar device(pore size12~13mm) to the porous nozzle blowing device (pore size4.2mm). And designed two kinds of new refining process programs: nitrogen+fusing agent and powder injection refining process. By the analyzing of surface finish and pinhole grade of the sample, researched the influence of different refining process on the pinhole of the cylinder body, and explored the different mechanisms of molten melt refining process. Research results shows that the powder injection refining process is the best, which decreases the pinhole grade from fourth degree to first degree; the nitrogen+fusing agent process is the better, which decreases the pinhole grade from fourth degree to second degree; the innocuous refining flux+fusing agent refining process is the last, which decreases the pinhole grade from fourth degree to third degree. By adopting the powder injection refining process, the pinhole grade of castings decreased form third degree to first degree, and the scrap rate for leakage of castings decreased from28%to4%.Based on orthogonal experiment, adopted the method of combination of numerical simulation and actual test, the mold filling and solidification procedure were studied and predicted the defects of casting by AnyCasting numerical simulation software. The porosity area (shrinkage cavity, shrinkage porosity and air hole) of aluminum alloy cylinder body casting for motorcycle were investigated by ImageJ statistics software. The reliability of the numerical simulation results were verified by the method of measuring the density and the change rate of density of casting and heat treated casting. The effects of fast shot velocity, fast shot set point, mold temperature and casting pressure on the porosity defects of aluminum alloy cylinder body casting for motorcycle were investigated. Research results shows that the porosity defects of the casting increases with the increasing of the fast shot velocity and decreases with the increasing of fast shot set point, mold temperature and casting pressure. The optimum process parameters are: fast shot velocity-2.0m/s, fast shot set point-280mm, mold temperature-240℃and casting pressure75Mpa. By adopting the optimization parameters, the casting density was increased, the percentages of porosity area on the top surface and bottom surface of the casting were respectively decreased about21%and68%, and the casting scrap rate was reduced from14%to5%.