應用氣體反壓技術改善金屬粉末射出成型充填流動特性與品質之研究

Study on Flow Behavior and Quality Improvement of the Metal Powder Injection Molding by Using Gas Counter Pressure Technology

謝政璋(Cheng-Chang Hsieh)

指導教授 ： 陳夏宗

中原大學/工學院/機械工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400421

摘要

金屬粉末射出成型(Metal Powder Injection Molding, MIM)為結合塑膠射出成型與粉末冶金的近淨形(Near Net-Shape)成型技術。製程包括由粉末與塑膠結合劑之混煉、模具設計、射出成型、至後製程之脫脂、燒結與二次加工，涵蓋多項製程，獲得穩定品質實屬不易，尤其在射出階段產生之內應力與粉膠分離等缺陷，等到脫脂與燒結後產品產生翹曲變形現象時才得知已難補救。因此本研究希望能在射出階段時改善MIM初胚的穩定性，進而提升燒結後的產品良率與機械性質，可以減少材料之浪費。

本研究將建置氣體GCP控制(Gas Counter Pressure, GCP)並開發配合GCP 與 MIM專用的模具與成型技術，於充填初胚階段加入50 bar與100 bar之高壓氮氣後，針對初胚、溶脫後、燒結後之產品進行不同區域之密度與拉伸強度、硬度、收縮率、粉膠分離區域大小的量測，由此希望能預測燒結後產品之缺陷；研究也將對MIM 的計算機輔助工程( Computer Aided Engineering, CAE)分析模擬技術進行開發，藉由材料測試建立MIM配方之剪切黏度資料庫。最後使用電腦化數值控制(Computerized Numerical Control, CNC)切削原316L不鏽鋼的拉伸試棒與傳統MIM以及加入GCP之產品進行機械性質比較。

研究結果顯示，加入100 bar GCP初胚密度均勻性提升了59.96%，粉膠分離區域降低了59.57 %，；在分析方面整體金屬粉末濃度分佈趨勢都與實驗相同；最後是CNC原鋼材與傳統MIM以及MIM加入GCP製程的比較，當金屬射料充填時受到反向壓力的推擠，使得射料在充填時更加緊密，讓燒結過後的平均拉伸強度增加了43.39%，伸長量增加66.6%、密度達到99.1%。

關鍵字

金屬粉末射出 ； 氣體GCP控制技術 ； CAE分析模擬技術

並列摘要

Metal powder injection molding (MIM) is a near net-shape manufacturing method combining plastic injection molding process with powder metallurgy process. Since MIM involves the widespread process characteristic, it often ends with unstable on product quality. Especially, the defect of warpage appears usually after the step of agglutination and de-binding result from the stress occurred in injection molding step.

The purpose of this study is to establish the gas counter pressure(GCP) control, a matched mold, and implement it to the metal powder injection molding process. This study used a gas pressure of 50 bar and 100 bar, Then measure the mechanical properties and product quality. In the present study, the research of CAE is also carried out to help the mold design and understand the flow characteristics and proper mold design. Finally, we bring an original 316L stainless steel tensile bar by CNC process into comparison.

The results show MIM make more uniform density distribution, GCP improve the uniformity of the product 59.96%,and powder-binder separation area reduced by 60%. Been in the other direction when the metal plunger pushed filling, making a more solid material shot during filling, Finally, we compare the original steel and MIM and MIM + GCP, and we found that the average tensile strength after sintering is increased 43.39%, elongation also increased 66.6%; adding GCP product density reached 99.1%.

並列關鍵字

Computer Aided Engineering ； Gas Counter Pressure ； Metal Injection Molding

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