Optimization Of Aluminum Ingots And Analysis Of Casting Defects In Automobile Wheel Hubs

As the continuous improvement of living standard,the luxury cars have become a very popular means of transport.However,with the intensification of environmental pollution and energy crisis,demands of energy-saving and emission-reduction have been raised for automotive industry.Therefore,aluminum alloy wheel hubs have been developed rapidly in the past decades.As for the production process,pressure die-casting is the most popullar technology with the lowest production cost.Against this backup,differnet aluminum ingot materials have been compared to optimize the most suitable one to produce aluminum alloy wheel hubs.Meanwhile,surface defects of the wheel hubs were observed.The reasons that caused the surface defects were analyzed and reasonable suggestons were put forward to improve defects.The original microstructures of 101 aluminum ingot,833 aluminum ingot,and 607 aluminum ingot were observed for comparision.The mechanical properties and microstructures at different positions of the trial products and end products during the bath production were also made.Results showed that Yunnan aluminum ingots contained the least content of harmful alloying elements and the most content of favorable alloying elements.The grains of Yunnan aluminum ingots were relatively small,arranged regularly and the shape of eutectic silicon particles was round.Stable mechanical propertiea were obtianed in aluminum alloying wheel hubs produced from Yunnan aluminum ingots.After the same heat treatment,aluminum alloying wheel hubs made from Yunnan aluminum ingots obtained the best plasticity.From the view of performance loss ratio from trial products to end products,performance pass ratio after heat treatment,and the whole product pass ratio during mass production,Yunnan aluminum ingots were regarded as the most suitable materials to produce wheel hubs.Surface defects in aluminum alloying wheel hubs at two different production lines were observed and analyzed.The macroscopic morphologies of defects in wheel hubs at the No.2 production line were more complicated than that at the No.1 production line.Holes with circular boundaries and inclusions containing carbon and oxygen inside them dominated the defects in the wheel hubs at No.1 production lines.While at No.2 production lines,long and narrow holes caused by acicular ?-Fe were the main defects.In addition,a few holes were filled with fibrous inclusions.Defects with inclusions containing carbon and oxygen were caused by gases nucleating at small ones.That was the reason why the boundaries were circular.The phase of ?-Fe impeded the feeding process of the aluminum liquid and promoted the formation of holes,which finally resulted in the complicated morphologies of defects.The fibrous inclusions in some holes were caused by the fiber dropped off from filter screens.Suggestions to improve the defects were raised according to the analysis.That improving the quality of aluminum liquid and the casting systems,and optimizing the casting process parameters would be helpful.