On the Process Evaluation and Quality Control of the Production of A356 Wheel Castings

• Main Authors: Chen, J.S., 陳建興
• Other Authors: E.N. Pan
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/55179280884423431273

碩士 === 國立臺灣大學 === 機械工程學系 === 85 === abstract The production processes of A356 Al-wheels in a specific foundry was evaluated in this study. The process standardization was proposed for that specific foundry based upon the evaluation results. A rotary impeller degasser is currently used for the degassing treatment in the foundry. The degassed melt contained commercially accepted low gas level. However, the gas content of the melt increased gradually with increasing holding time, and the gas content reached an unacceptable level after holding for over 90 minutes. The microstructures of the Al-wheels currently produced in the foundry were thoroughly analyzed with the results indicating that substantial shrinkage porosity was present in the central portion of the rim section of the Al-wheels. Failing to maintain a directional solidification pattern and/or high enough temperature gradients were found to be responsible for the formation of the porosity defect. Modifying the ingate design and employing forced cooling at the central rim section were suggested for the elimination of this porosity defect. Furthermore, the feasibility of reducing the section thickness of the as-cast Al-wheels was evaluated in this study by using tensile and impact properties as the criteria. The results show that the original thickness of rim section of 10- 15㎜ can be reduced to around 9㎜. Also, accompanying with the reduction of section thickness, the T6 solution time at 540℃ can be shortened to 2-4hr from original 6hr and still obtains improved properties.