基層組織對沃斯回火球墨鑄鐵韌性的影響

Effects of Microstructure on Toughness of Austempered Ductile Iron

溫東成(Dong-Cherng Wen)

《中華技術學院學報》 23期 (2001/09) Pp. 125-134

https://doi.org/10.7095/JCIT.200109.0125

摘要

本研究改變傳統沃斯回火球墨鑄鐵的熱處理程序，於沃斯田鐵化後先爐冷至700-730℃的沃斯田鐵、肥粒鐵與石墨三相共存區析出肥粒鐵後，再淬冷至低溫鹽浴槽進行沃斯回火恆溫變態，藉由不同沃斯回火時間的控制可以使基底成為5-20%體積分率的初析肥粒鐵、0-10%體積分率的麻田散鐵與沃斯肥粒鐵的混合組織。實驗結果顯示隨初析肥粒鐵增加，抗拉強度與降伏強度降低，伸長率與衝擊值則有明顯的增加，相反的，麻田散鐵增加，強度增加而延性與韌性減少。麻田散鐵含量如控制在5%左右且初析肥粒鐵含量不超過10%則可以得到等同傳統處理於ADI製程窗間內的強度與更優異的延性與韌性，此時破斷面特徵也由傳統ADI的脆性準劈裂與延性蜂巢孔的混合斷裂轉變為完全延性的蜂巢孔斷裂。

關鍵字

沃斯回火球墨鑄鐵 ； 肥粒鐵 ； 麻田散鐵 ； 韌性

並列摘要

New austempered ductile cast iron precipitated ferrite around the spheroidal graphite was produced by a modified heat treatment. The process involved austempering at 350°C for 5-30 min after furnace cooling to 700-730°C from an austenitizing temperature of 900°C for 60 min (α/M-ADI). In this process, a mixture structure of 5-20% ferrite around the graphite and 0-10% of martensite with ausferrite was obtained. The results show that the elongation and Charpy impact toughness of α/M-ADI with 5% of martensite and bellow 10% of ferrite were increased remarkably. While the tensile strength and 0.2% yield strength of α/M-ADI were at the same value level of the conventional ADI. The fracture surface also changed from a mixture of quasi-cleavage and ductile dimple to fully ductile dimple.

並列關鍵字

Austempered ductile iron ； ferrite ； mechanical properties