臺灣博碩士論文加值系統

本實驗旨在利用改變沃斯回火溫度(300℃∼400℃)，以及合金鉻的含量(0.2~1.5wt%)等實驗條件，將片狀石墨鑄鐵於900℃恆溫2小時後，急冷至沃斯回火溫度持溫2小時，進行沃斯回火熱處理，以期探討沃斯回火溫度、鉻含量對於沃斯回火片狀石墨鑄鐵的顯微組織以及機械性質等影響。
實驗結果顯示，沃斯回火熱處理後，基地組織由肥粒鐵以及塊狀和少量之條狀沃斯田鐵所組成，沃斯回火溫度較低時，肥粒鐵組織為細密之針狀，當沃斯回火溫度較高時，肥粒鐵組織會有粗大化的現象，殘留沃斯田鐵所佔之比例會也會有所增加；在相同的熱處理條件下，當鉻含量較低時，沃斯回火熱處理後之組織中所含之殘留沃斯田鐵則是有所下降，而當鉻含量較高時，由於鉻會與碳形成碳化物析出於基地相中，使得沃斯田鐵量增加，析出物和基地組織中的鉻含量比例，會隨著沃斯回火溫度改變而有所增減。
當沃斯回火溫度增加時，則鑄件之機械性質，硬度以及抗拉強度會隨之下降，抗拉強度最大值則出現於添加1.5wt%Cr之鑄鐵試片，沃斯回火溫度為300℃時，達到1448 MPa。

The study was carried out to change austempering temperature (300℃~400℃), and the content of chromium (0.3~1.5wt%). The flake graphite cast iron were austenitized at 900℃ for 2 hours, and then quenched to the austempering temperature and holded the temperature for 2 hours. The study was to examine the influence of the austempering temperature and the percent of chromium on the mechanical properties and the microstructure of the austempered flake graphite cast iron.
The result of the study showed that the matrix were composed of ferrite and block and a few of string-type of austenite. When the austempering temperature were low temperature, the structure of ferrite were to grow and coarse, and the retained austenite content and the value of retained austenite content multiplied by the carbon content of austenite rises with rising austmpering temperature. The Heat treatment in the same conditions, when the chromium content was lower, the retained austenite volume fraction was decrease; when the chromium content was higher, there was formation of carbide precipitation in the matrix, caused to increased austenitic volume fraction, the ratio of chromium content of carbide and the matrix, it will decrease as the temperature increases.
When the tempering temperature increased, the mechanical properties of the casting iron, the hardness and tensile strength will be drop, and the ultimate tensile strength occurs in the 1.5wt% Cr, and austempering temperature at 300 ℃ to 1448 MPa.

摘要 I
ABSTRACT II
誌謝 IV
目錄 VI
表目錄 IX
圖目錄 X
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 1
第二章 文獻回顧與理論基礎 3
2.1 鐵-碳平衡相圖 3
2.2 石墨型態 5
2.2.1 片狀石墨 5
2.2.2 球狀石墨 8
2.2.3 蠕蟲狀石墨 9
2.3 基地組織相 10
2.3.1 沃斯田鐵(Austenite)相 10
2.3.2 肥粒鐵(Ferrite)相 10
2.3.3 雪明碳鐵(Cementite)相 10
2.3.4 波來鐵(Pearlite)相 10
2.3.5 沃斯肥粒鐵 11
2.4 沃斯回火熱處理 13
2.4.1 沃斯田鐵化 14
2.4.2 急冷至沃斯回火溫度 16
2.4.3 在沃斯回火溫度持溫 17
2.4.4 自沃斯回火溫度空冷至室溫 18
2.5 合金元素的影響 19
2.5.1 碳 20
2.5.2 矽 20
2.5.3 錳 22
2.5.4 磷 23
2.5.5 硫 23
2.5.6 鉻 23
第三章 研究方法 25
3.1 使用材料 27
3.2 試片製作及取樣 27
3.3 沃斯回火熱處理 29
3.3.1 沃斯田鐵化熱處理 29
3.3.2 沃斯回火溫度持溫 29
3.4 金相顯微組織觀察 30
3.5 殘留沃斯田鐵分率計算 31
3.6 殘留沃斯田鐵中碳含量計算 34
3.7 機械性質量測 35
3.7.1 硬度試驗 35
3.7.2 拉伸試驗 35
第四章 結果與討論 37
4.1 不同的鉻含量對於片狀石墨鑄鐵之影響 37
4.1.1 顯微組織 37
4.1.2 機械性質 40
4.2 不同鉻含量對顯微組織之影響 41
4.2.1 沃斯回火溫度為300℃ 41
4.2.2 沃斯回火溫度為350℃ 45
4.2.3 沃斯回火溫度為400℃ 48
4.3 不同沃斯回火溫度對於顯微組織之影響 54
4.3.1 顯微組織 55
4.3.2 機械性質 67
第五章 結論 72
參考文獻 73

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