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    模擬及驗證球墨鑄鐵之暗冒口設計

    發佈:2020/08/31 09:26:04

    摘  要

    本研究是應用凝固模擬模組模擬多種暗冒口方案設計在球墨鑄鐵的鑄造,並且實際鑄造實驗來驗證凝固模擬模組的準確性。發現只有所謂的第一原則收縮模組(First Principles shrinkage model),可以用來模擬複雜的球墨鑄鐵液體的凝固過程、凝固收縮時殘留熔液的流動現象、以及球狀石墨的體積膨脹等現象;並且可以在凝固過程中,準確地追蹤液-固界面的最低位置,以及收縮負壓的位置所在。

    實際鑄造七種冒口方案的球墨鑄件,在分別的鑄件中心剖面上,每間隔5mm處進行二維的硬度分佈的測量,找尋在中心剖面的實際縮孔的外形及位置。證實了模擬所追蹤的縮孔位置即是凝固過程中殘留熔液在當時凝固鑄件的最低處。並提出凝固模擬與實際鑄件之縮孔外形上的差異原因。
    關鍵詞:球墨鑄鐵凝固、石墨體積膨脹、熱點區域、斷面硬度分佈、暗冒口設計

    ABSTRACT

    In this study, two solidification modeling models were validated by ductile-iron casting experiments on various blind feeder designs. It is found that only the so-called first principles shrinking model could be used for predicting the flow phenomenon and volumetric expansion of spheroidal graphite during the solidification process of spheroidal graphite cast iron. It also could accurately track the lowest liquid level in the solid-liquid interface and predict the location of the negative pressure developed by the liquid-solid transformation during the solidification process.

    After casting the seven blind-feeder designs of ductile iron castings, the hardness in every 5 mm distances within the central cross-sectional plane of these castings were measured.

    The actual shrinkage contour and locations on the central plane of the castings were discovered. Itshows that the shrinkage profiles and locations predicted by the FP model are the regions where the residual liquid at the lowest liquid level within isolated regions during solidification. For shrinkage profiles, the differences in between the real castings and the modeling results were explained.

    Keyword: solidification of ductile cast iron, graphite volumetric expansion, hot-spot region, hardness contour test, blind feeder design

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