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Title: | 鉻添加對SK85沃斯回火處理之顯微組織及機械性質的影響 Effect of Chromium Content on the Microstructures and Mechanical Properties of JIS SK85 Austempered Steels |
Authors: | Shih-Chuan Cheng 鄭十銓 |
Advisor: | 王文雄 |
Keyword: | 沃斯回火,變韌鐵, Austempering,bainite, |
Publication Year : | 2008 |
Degree: | 碩士 |
Abstract: | 摘 要
本實驗的主要目的在於探討三種不同鉻含量的鋼材,分別為JIS SK85、SK85+0.4wt%Cr及SK85+0.8wt%Cr,藉由適宜的熱處理條件,包括最佳沃斯田鐵化溫度與最佳沃斯回火溫度的配合,來達到HRC48~52的硬度值範圍。並探討鉻含量對機械性質與顯微組織的影響。 實驗結果顯示SK85、SK85+0.4 wt%Cr及SK85+0.8 wt%Cr三種鋼材的最佳沃斯田鐵化溫度分別為820℃、840℃及840℃;沃斯回火溫度分別為310±10℃、330±10℃及330±10℃,持溫時間均為30分鐘。鉻的添加會使硬度、強度及可硬化(硬度達HRC50以上)的厚度增加,然而衝擊值則降低。強度、硬度的增加是因為隨含鉻量的增加,會使變韌肥粒鐵基地固溶較多的鉻而有固溶強化的效果,因此強度、硬度隨之增加。 此外,傳統淬火回火的衝擊值較同硬度之沃斯回火的衝擊值來得低,其原因為傳統淬火回火的衝擊破斷面是以較脆性的沿晶破壞為主。 關鍵字:沃斯回火、變韌鐵。 Abstract The purpose of this research is researched for three kinds of different chromium contents of steels, which are JIS SK85, SK85+0.4Cr wt%, and SK85+0.8Cr wt%, by appropriate heat treatment conditions including the best austenitizing temperature and the best austempering temperature, to reach the hardness range 48~52 of HRC. And it is also researched that different chromium contents influence on the mechanical properties and microstructure of the steels. The experimental results show that the best austenitizing temperature of JIS SK85, SK85+0.4Cr wt%, and SK85+0.8Cr wt% are 820℃, 840℃, and 840℃ respectively, and the best austempering temperature of JIS SK85, SK85+0.4Cr wt%, and SK85+0.8Cr wt% are 310±10℃, 330±10℃, and 330±10℃respectively, and all holding time is 30 minutes. When chromium content in the steel increases, the hardness, the strength and the range of hardened thickness(reaching above HRC50) increase, but the impact value decreases. The increments of the hardness and the strength are because that when chromium content in the steel increases, it can be solved more chromium in the bainitic ferrite matrix, and have more effects of solid-solution strengthening. Therefore, the hardness, the strength increase with increasing chromium content in the steel. Furthermore, the impact value of traditional quenching and tempering is lower than the impact value of austempering with the same hardness. Because that the impact fracture surface of traditional quenching and tempering is major with more brittle intergranular fracture. Key word : Austempering, bainite. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/27360 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 材料科學與工程學系 |
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ntu-97-1.pdf Restricted Access | 10.31 MB | Adobe PDF |
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