金屬粉末射出成形溶劑脫脂製程中缺陷產生原因及解決方法

The causes of defects during MIM solvent debinding process and methods of improvement.

蘇少欽(Shao-Chin Su)

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.2006.00921

摘要

粉末射出成形對於複雜形狀零件具有極佳的成形能力，但若其溶劑脫脂過程中，參數控制不當會造成試片產生裂縫、裂痕、魚鱗紋等缺陷，於試片燒結後會影響成品外觀，需多加上研磨拋光等製程，增加成本，甚至於降低成品機械性質。為了有效改善溶劑脫脂產生之缺陷，本研究首先以一般的溶劑脫脂條件製造出試片缺陷，觀察試片缺陷的型態，再來針對溶劑脫脂參數，例如溶劑脫脂溫度、試片厚度、溶劑種類作比較，歸納缺陷形成起因及改善方法。
由雷射膨脹儀(in-situ dimension change)結果顯示，溶劑脫脂時膨脹量越大，試片越容易產生裂縫，且溶劑脫脂溫度一旦超過試片中石蠟之熔點，膨脹量將大幅提高，導致魚鱗紋產生；此魚鱗紋之成因是試片膨脹而造成鐵粉與黏結劑間附著能力變差，而316L不?袗?粉表面與黏結劑附著能力不良，更容易產生魚鱗紋。此外，不同厚度之試片，其膨脹量隨著厚度增加而上升，因此工件尺寸複雜之零件，需注意其不同厚度相接處造成的缺陷。添加異丙醇於正庚烷溶劑中可有效降低試片膨脹量，而生胚經過烘烤後再施以溶劑脫脂的話，試片產生缺陷的機率亦大幅降低。

關鍵字

粉末射出成形 ； 尺寸變化 ； 膨脹儀 ； 溶劑脫脂 ； 脫脂 ； 缺陷

並列摘要

Powder injection molding (PIM) has become a popular process in producing complex-shaped parts. However, defects are still frequently found , particular during solvent debinding. These defects will decrease the mechanical properties of the products. In order to improve that, the effect of solvent debinding temperature, specimen thickness, and different solvents were examined.
The laser dilatometer analyses indicate that large amount of length changes usually occur when the solvent debinding temperature is higher than the melting point of the paraffin wax and fish scales are found on the surfaces. The fish scale is caused by the poor bonding between powder surfaces and binders, especially for 316L stainless steels. The length change also increases as specimen thickness increases. Thus, defects are found easily in complex-shaped parts. Moreover, it was found that adding IPA to heptane can decrease the specimen length changes. The specimens with baking process will also have higher yield after solvent debiding.

並列關鍵字

powder injection molding ； in-situ dimensional change ； laser dilatometer ； solvent ； solvent debinding ； defects ； cracks

參考文獻

[2] K. S. Hwang, ”Fundamentals of Debinding Processes in Powder Injection Molding”, Reviews in Particulate Materials, 1996, Vol. 4, pp. 71-103.

[3] C. W. Finn, “Vacuum Binder Removal and Collection”, International Journal of Powder Metallurgy, 1991, Vol. 27, No. 2, pp. 127-132.

[4] K. S. Hwang, H. K. Lin, and S. C. Lee, “Thermal, Solvent and Vacuum Debinding Mechanisms of PIM Compacts”, Materials and Manufacturing Processes, 1997, Vol. 12, No. 4, pp. 593-608.

[6] B. Zhu, X. Qu, and Y. Tao, “Mathematical Model for Condensed-Solvent Debinding Process of PIM”, Journal of Materials Processing Technology, 2003,Vol. 142, No. 2, pp. 487-492.

[7] M. A. Omar, R. Ibrahim, M. I. Sidik, M. Mustapha, and M. Mohamad, “Rapid Debinding of 316L Stainless Steel Injection Moulded Component”, Journal of Materials Processing Technology, 2003, Vol. 140, pp. 397-400.