鐵-磷-碳系低溫燒結合金之製程及機械性質

Processing and Mechanical Properties of Low-Temperature Sintered Fe-P-C Alloy

顏福成(Fu-Cheng Yen)

指導教授 ： 黃坤祥

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00859

摘要

金屬射出成形(Metal Injection Molding, MIM)可以製造出形狀複雜、表面粗糙度佳且ㄧ次淨形之零件，但利用MIM製程所得之生胚密度僅為50-60%，因此必須藉由燒結來達到堪用的密度，故一般初始粉末通常都採用10μm以下的細粉，配合著1200-1300℃的高溫，持溫至少2小時，以達到94%以上之密度。而高溫燒結所伴隨著即是高設備成本與高能源消耗，此大大降低MIM產品的競爭力，故本研究主要是設計出一個能適用於低溫燒結的合金組成，使之能在一般設備成本較不昂貴且國內技術也較為成熟的低溫網帶爐下進行燒結，就可得到至少90%以上的燒結密度，及不錯的機械性質。
而本實驗也証實了利用Fe-0.7P-0.6C合金在1080℃持溫30分鐘後，即能得到密度7.4g/cm3、強度800MPa、硬度HRB98與伸長率12%的機械性質，此已超出美國粉末冶金協會(MPIF)中具有最佳機械性質之MIM-4605合金，且利用EPMA與SEM觀察破斷後的組織發現，即使在低溫短時間下燒結，亦可得到元素分佈非常均勻的組織與酒窩狀延性破裂結構。
另外，本實驗亦嘗試找出P可能產生偏析的含量與其發生的原因，而由實驗結果得知，當Fe-C系合金中P含量超過0.7wt%時，破斷面會從原本具有延性特性的酒窩狀組織變成具脆性的沿晶破裂組織。
而在添加過多種合金元素後，仍以Fe-0.7P-C系合金在低溫短時間燒結過後具有不錯的機械性質。

關鍵字

金屬粉末射出成形 ； 低溫燒結 ； 網帶爐 ； α相燒結 ； Fe-0.7P-C系合金

並列摘要

Alloyed parts with complicated shape, smooth surface toughness and near net shape can be fabricated in metal injection molding (MIM) process. But green parts made by MIM process just have only 50-60% relative density, it is necessary to use lower than 10μm ultra fine powder as starting powder and sinter at 1200-1300℃ high temperature for 2 horses then 94% relative density can be ontained.
Higher equipment cost and energy consumption followed by high temperature sintering result in lower competition for MIM process. So design alloy composition for low temperature sintering to make allying parts sinter at belt furnace with lower cost then have sintered density above 90% and good mechanical properties.
It is showed that Fe-0.7P-C sintered at 1080℃ for 30mins can get the value of 7.4g/cm3 in sintered density, 800MPa in ultimate tensile strength, HRB98 in hardness, 12% in elongation in this study, that is superior to standard MIM-4605 counterpart which has better mechanical properties in MPIF. The uniform elemental distribution and ductile dimple structure can be observed by EPMA and SEM equipment even sintered at low temperature
Additionally, the possibility of P content causing segregation and its mechanism were also studied in this experiment. According to the experimental results, when P content in Fe-C alloy is more than 0.7wt%, the original ductile dimple structure turning into brittle intergranular structure on fracture surface was observed.
Fe-0.7-C alloy sintered at low temperature for short time has optimal mechanical properties as compared to other counterparts in this study.

並列關鍵字

Metal Injection Molding ； Low Temperature Sintering ； Belt Furnace ； α-Phase Sintering ； Fe-0.7P-C Alloy

參考文獻

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