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鋁合金薄壁鑄件上的匯流熔接缺陷

Confluence-Welded Defects in Thin Wall Aluminum Castings

作者:楊堯名
畢業學校:國立聯合大學
出版單位:國立聯合大學
核准日期:2010-09-13
類型:Electronic Thesis or Dissertation
權限:Copyright information available at source archive--National United University....

中文摘要

鋁合金的重力鑄造,在薄壁鑄件上方常會發現表面有匯流熔接不完全所造成的缺陷,如汽車引擎汽缸頭,或其他箱型鑄件,此缺陷常為鑄件之強度弱點,縮短其鑄件的使用壽命。
為了解匯流熔接缺陷的發生原因,本實驗設計了三種流道系統。而兩邊鋁液充填前端的匯流速度差,即決定了其匯流熔接的情況。當兩鋁液充填前端之速度差越大時,其最終的匯流位置越是遠離上方平面處之中心線。鑄造實驗的鋁液充填前端速度之量測方法是使用電壓記錄器與LED亮燈的方式錄影記錄,也同時利用電腦模擬軟體作速度與匯流位置的預測。
發現鑄件上方平面之匯流處,會有兩種不同型態的匯流形式。如果使用單邊進模口的流道系統,會使得兩匯流之鋁液充填前端的速度差會越大,造成其匯流熔接缺陷越是明顯;當使用兩邊進模口的流道系統,其缺陷的發生就會改善。
本實驗對所有流道系統之鑄件,觀察其上方平面之表面狀況與使用電腦模擬之預測,得到鑄件的最後匯流位置,並且利用四點抗折測試量測其鋁液匯流熔接強度。

英文摘要

In aluminum gravity castings, a confluence weld defect could be found on the top flat surface of a thin-wall casting, such as a car engine cylinder head housing or a box shape casting. Such defect became a weakest point of mechanical property of the casting and it would shorten the service life of the casting.
In present study, three types of runner systems were designed in order to understand the cause of confluence weld defect. In the result, the formation of a confluence weld is determined by the velocity difference between two metal filling-fronts. As the difference is greater, the position of confluence weld where two fronts met is distance further away from center line of the casting geometry. During casting experiments, the velocities for two metal filling-fronts were measured by means of voltage data recorder and high speed videoing with the help of LED lights. They were also predicted by computational modeling. Two types of confluence weld above the top surface were discovered. In single-gating system, the difference is greater and the defect is more notable. In double-gating system, the different become less.
In all of runner systems, the position of a confluence weld was observed from the surface of top plate region of the casting experiment and it also was predicted by computational modeling. Furthermore, the strength of the confluence weld was evaluated by four-point bending method.


委員 - 林惠娟

召集委員 - 汪俊延

委員 - 陳俊沐

委員 - 吳鉉忠

指導教授 - 許富淵


 

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