鉄粉圧縮体の焼結現象の研究(III)
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Torajiji Nishijima : 1 Sintering of Iron Powder Compacts. 1. 3. Changes of Pores in Powder Compacts during Sintering. In this paper, pore changes in powder compacts during sintering were studied. Before sintering, voids between powder particles meant to pores, but after sintering, crystal grain growth among particles were progressed, so voids were included inter or inner crystal grains. In old times, it was considered that pores became to be spherical shape, and disappered at last. But in reality, even if sintered for longer time, it was difficult for pore to be disappered. And then its found that pores were settled to some negative crystal shape based upon the crystallographical characteristics of the back ground. (for example, octahedral shape of pores were found in tungsten powder compacts.)<BR>On the other hand, if powder compacts composed of mixtures were sintered at some higher temperature than the melting point of one of components, and if all of the liquid phase did not be alloyed, pores became to be disappered after longer heating [for cxample, such a fact was gained by heating the iron and copper (5-40%) powders mixture at 1100°C.] But if all of them were alloyed into solid solution, small pores used to stay, just like in the case of powder compacts composed of single component. [example ; by heating the copper and tin (10%) metal powders mixture. at 800°C.] Also its revealed that at the first stage of heating above the melting point of one of components, coarse pores used to be prepared by the penetration of liquid phase among solid powder particles. The grades of these pores size were especially depended on the grades of powder size to be molten. Itll be a convenient structure to get good self-oiling ability of the oilless bearing.
- 社団法人 粉体粉末冶金協会の論文