鈷鎳元素與非恆溫沃斯回火對延性鑄鐵微結構及機械性質之影響

Effects of Nickel and Cobalt Elements and Variable Austempering on Microstructure and Mechanical Properties of Ductile Iron

韓濟帆(Chi-Fan Han)

指導教授 ： 許正勳

大同大學/工程學院/材料工程學系所/碩士(2006年)

摘要

延性鑄鐵經過沃斯回火熱處理後形成沃斯回火球墨鑄鐵(ADI)，以往的研究針對恆溫沃斯回火熱處理以及二段式恆溫沃斯回火熱處理進行實驗，探討持溫時間與沃斯回火溫度之間的關係，然而卻很少探討持續升溫或是持續降溫之變溫沃斯回火熱處理，而是否能夠經由變溫沃斯回火熱處理得到更高性能之ADI，正是本實驗的主要目的。
本實驗使用延性鑄鐵及其含4wt%鈷或4wt%鎳進行實驗，探討此二種合金元素對FCD以及ADI的影響，材料先於910℃進行沃斯田鐵化熱處理，持溫時間為1.5hrs，接著在分別進行恆溫(300℃、360℃)和變溫(300→360℃、360→300℃)之沃斯回火熱處理2hrs。探討各條件下試片之抗拉強度、硬度、衝擊韌性、伸長率、破裂韌性以及殘留沃斯田鐵的含量等。
實驗結果顯示，變溫沃斯回火熱處理所得到之ADI組織與其淬火有密切的關係，並且與該溫度之恆溫熱處理的ADI組織相似，另外，在機械性質方面則大致上比恆溫沃斯回火來的好，最佳的破裂韌性出現在無合金元素添加之延性鑄鐵(材料A)搭配降溫沃斯回火所得到的ADI。

關鍵字

沃斯回火 ； 延性鑄鐵

並列摘要

Austempered ductile iron (ADI) is produced via the austempering treatment of ductile iron. The focus the past researches is to study the effects of isothermal austempering heat treatment and two-step austempering heat treatment, but seldom probe into the effects of variable austempering heat treatment. The phase of this research is to study the effects of variable austempering heat treatment on properties of ADIs.
In this study, 4 wt% nickel (Ni) and 4 wt% cobalt (Co) was added to ductile iron as experimental material, and then performed a series of austempering treatment consisting of different temperatures (300, 360, 300→360, 360→300℃) for 2hrs. Microstructures of ADI were observed and both mechanical properties and retained austenite of ADI were also measured, respectively.
The experimental results showed that Microstructures of ADI produced via variable austempering treatment are in relation to quenching temperature and they are similar to the microstructure of ADI treated isothermally in the same quenching temperature. Furthermore, Mechanical properties of ADI produced via variable austempering treatment are generally better then ADI produced via isothermal austempering treatment. The optimum fracture toughness appeared in the non-alloyed ADI produced via decreased austempering treatment

並列關鍵字

austempeting ； ductile iron

參考文獻

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