金属射出成形におけるコンパウンドの流動性および加熱脱脂時の変形におよぼす粉末特性の影響

Abstract

In MIM (Metal Injection Molding) technology, moldability of feedstock and resistivity of compact to debinding deformation are very important to mold highly complex shapes without defects and to maintain close tolerances of final products, respectively.In this paper, the effects of powder characteristics on the flowability of feedstock and the deformation of compact during thermal debinding were studied using 6 kinds of powders. For specific powders, the effect of binder content was also investigated. The flowability of feedstock was estimated by MFR (Melt Flow Rate) at 170°C, while the debinding deformation was determined in bending mode using rectangular bar specimens supported both ends.As expected, spherical powders exhibited much higher flowability of feedstock than irregular powders, showing flowability in proportion to the tap density. For irregular powders, however, there observed no correlation between the folwability of feedstock and the tap density of powder. The flowability of feedstock increased with increasing binder content for both spherical and irregular powders. On the other hand, spherical powders showed much lower resistance to debinding deformation than irregular powders. For both spherical and irregular powders, the resistance to debinding deformation increased with decreasing mean particle size and decreased with increasing binder content.It was concluded the above results that there exists inverse relationship between the flowability of feedstock and the resistance of compact to debinding deformation because they are inversely affected by the same factors i.e. interparticle friction and/or interparticle separation.