臺灣博碩士論文加值系統

粉末合金鋼已被廣泛應用在機械、汽機車、光電等產業上等相關零組件，然而，粉末原料仰賴國外進口，導致整體發展受到限制，因此，本研究目的是發展可應用於粉末冶金之氫氣還原鐵粉，還原條件必須嚴謹控制，必須同時兼顧還原完全度與粉末壓縮性。首先以次微米級Fe2O3粉作為初始原料，以陶瓷粉末濕式製程配合噴霧造粒，獲得流動性良好且無明顯缺陷之球形造粒粉，並找出適當的還原溫度。
經氫氣還原結果顯示，當還原溫度由600˚C提升至930˚C時，造粒粉內的顆粒逐漸粗化，表面積明顯下降，直接影響到燒結緻密化效果，燒結密度由7.42 g/cm3劣化到6.86 g/cm3。在瞭解還原溫度之影響後，後續將Fe2O3-NiO-Mo-C合金造粒粉以氫氣還原，結果指出600˚C還原後之氧含量為1.18wt%，隨著還原溫度的提升氧含量得以下降，當還原溫度為650˚C～700˚C時，氧含量則可下降至0.58wt%~0.26wt%。
採用此研究之方法實際製作文獻中具有超高強度的Fe-6Ni-0.8Cr-0.8Mo-0.4C，結果在1250˚C真空燒結後其燒結密度可達到7.49 g/cm3，優於一般粉末合金鋼之燒結密度，亦接近金屬射出成形製程之燒結密度。前述合金鋼在經過200˚C回火後其硬度達42HRC，抗拉強度達1628MPa，伸長率為2.0%。

Powder metallurgy (PM) steels have been extensively used in the parts for the mechanical, automobile, and optoelectronic industries. However, raw powders of PM steels highly rely on foreign suppliers, which lead to a disadvantage in the overall development. Therefore, the objective of this study was to develop a hydrogen-reduced spray-dried iron powder for PM steels. To fabricate the spray-dried granules with solid morphology and high flowability, a sub-micron Fe2O3 powder was used as the raw powder to formulate the ceramic slurry for spray drying. The reducing parameters must be precisely controlled to optimize the combinations of reduction completeness and powder compressibility.
The results showed that increasing the hydrogen reduction temperature of spray-dried Fe2O3 granule from 600 ˚C to 930 ˚C decrease the sintered density of Fe from 7.42 g/cm3 to 6.86 g/cm3, due to the particle coarsening in the spray-dried granules and the decrement in the surface area. In the second part, the spray dried Fe2O3-NiO-Mo-C granules were produced and were hydrogen-reduced. After 600 ˚C reducing, the residual oxygen content was as high as 1.18 wt%. The oxygen content could be decreased with increasing the reducing temperature. After reducing at 650˚C and 700˚C, the oxygen content was 0.58 wt% and 0.26 wt%, respectively.

Based on the previous findings, the ultrahigh strength Fe-6Ni-0.8Cr-0.8Mo-0.4C steel fabricated by metal injection molding (MIM), reported in the literature, have been fabricated in this study. The result indicated that the sintered density of Fe-6Ni-0.8Cr-0.8Mo-0.4C steel sintered at 1250˚C in vacuum is 7.49 g/cm3. This high sintered density is superior to those of most PM steels and is close to those of MIM steels. The hardness, tensile strength, and elongation of the Fe-6Ni-0.8Cr-0.8Mo-0.4C steel in this study are 42 HRC, 1628MPa, and 2 %, respectively.

摘 要 i
Abstract ii
誌謝 iv
目 錄 v
表目錄 viii
圖目錄 ix
第一章 緒論 1
第二章 文獻回顧 2
2.1粉末合金鋼簡介 2
2.2 鐵粉的製備 4
2.2.1 水噴霧法 4
2.2.2 氣噴霧法 4
2.2.3 羰基分解法 5
2.2.4 電解法 6
2.2.5 還原法 7
2.3 氫氣還原 8
2.3.1 鐵基粉末之氫氣還原 8
2.3.2 其他金屬粉末之氫氣還原 12
2.4 合金元素之影響 13
2.4.1 碳的效應 14
2.4.2 鎳的效應 15
2.4.3 鉬的效應 21
2.4.4 鉻的效應 24
2.5 顯微組織之影響 26
2.6 含鎳粉末合金鋼的破壞行為與機械性質 29
第三章 實驗方法與步驟 32
3-1 實驗設計 32
3.2 原始粉末 35
3.3 漿料製備 39
3.4 噴霧造粒 39
3.5 氫氣還原 40
3.6 還原造粒粉分析 41
3.6.1 XRD分析 41
3.6.2 SEM分析 41
3.6.3 表面積分析 42
3.6.4 碳/氧/氮/硫分析 42
3.6.5 雷射粒徑 42
3.7 混粉與生胚成形 43
3.8 脫脂與燒結 43
3.9 回火條件 44
3.10 燒結體性質分析 44
3.10.1 密度量測 44
3.10.2 金相觀察 44
3.10.3 合金元素分佈 45
3.10.4 拉伸試驗 45
3.10.5 硬度試驗 45
3.11 測量儀器 46
第四章 結果與討論 47
4.1 漿料與噴霧造粒粉之特性 47
4.2 還原造粒鐵粉之性質 49
4.2.1 結晶結構 49
4.2.2 粉末形貌 50
4.2.3 氧/氮含量分析 52
4.2.4 燒結密度 53
4.3還原Fe2O3-NiO-Mo-316L合金造粒粉之性質 54
4.3.1 結晶結構 55
4.3.2粉末形貌 56
4.3.3 表面積分析 58
4.3.4 碳/氧/氮/硫含量分析 58
4.4還原Fe2O3-NiO-Mo-C合金造粒粉之性質 60
4.4.1 粉末形貌 60
4.4.2 碳/氧/氮/硫含量分析 62
4.4.3 燒結密度 64
4.5 含鎳粉末合金鋼之顯微組織與機械性質 65
4.5.1 顯微組織 65
4.5.2 合金元素分佈 66
4.5.3 機械性質 69
4.5.4 破斷面觀察 70
第五章 結論 72
參考文獻 73

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