沃斯回火球墨鑄鐵深冷處理特性之研究

本研究主要對沃斯回火球墨鑄鐵作深冷處理的機械性質和微結構的關係深入的分析，所採用的材料為濕砂模澆鑄斷面25 mm的Y型球墨鑄鐵鑄件；探討的實驗參數有殘留沃斯田鐵量、肥粒鐵板條型態等因沃斯回火球墨鑄鐵深冷處理溫度不同的影響，並比較一般沃斯回火處理後與深冷處理之機械性質和微結構和差異性。實驗結果顯示比較不同深冷處理溫度，可發現抗拉強度，降伏強度，延伸率皆隨深冷處理溫度愈低則其強度愈高，而延伸率較低主要是因深冷處理溫度愈低，使基地中的殘留沃斯田鐵的量部分變態為變韌鐵或麻田散鐵量愈多導致。而硬度隨著深冷處理溫度愈低而增加，可以判斷出其抗拉強度，降伏強度亦有增加之趨勢，但延伸率則是稍微降低的。綜合原因，在基地內的殘留沃斯田鐵部分變態為麻田散鐵，使衝擊韌性隨深冷溫度愈低則其韌性有降低趨勢，若衝擊韌性吸收能量低，可證明沃斯回火球墨鑄鐵己經是由部分延性轉為脆性。

關鍵字

沃斯回火球墨鑄鐵；深冷處理

並列摘要

The mechanical properties and microstructures of various subzero treatment ductile iron (ADI) were investigated in this study. Y-block castings (25 mm) with inoculation for different austempering heat treatments of ductile irons (ADI and its subzero cooling), were prepared and test the mechanical properties of heat treated ADI. The developed mechanical properties were in relation with subzero temperature, distribution of residual austenite and the types of ausferrite in the martrix of ADI. The specimens were taken from Y-block castings for ductile iron. Then they treated with subzero cooling procedure in different subzero temperatures (ice water, CO_2, N_2). Mechanical properties included UTS, YS, elongation, hardness and impact toughness. Therefore observed microstructures of SEM used to describe the difference of mechanical properties for ADI and its subzero cooling. To improve the mechanical properties and stability of microstructure were fully development in this study and application in the future of industry.