焼結鉄の寸法変化,密度および疲労強さに及ぼす粉末潤滑剤の添加量と脱ロウ時の加熱速度の影響

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Effects of the lubricant content and the heating rate during dewaxing on the dimensional change, the density and the fatigue strength of sintered irons containing Zn-and Mg-stearates were investigated. The results obtained were as follows: (1) Irrespective of heating rates during dewaxing, all as-dewaxed specimens showed a shrinkage in the longitudinal direction except those of 1.5wt% Mg-stearate. Density of as-dewaxed specimens was lower than that of green compacts, but density of as-sintered specimens after dewaxing was nearly same as that of green compacts. (2) The fatigue strength of specimens decreased with increasing lubricant content and heating rate during dewaxing. The drop in strength was attributed to phenomena such as nonuniform distribution of porosity in Fe compacts and poor sintering caused by the decomposition of segregated lubricants at rapid heating rate during dewaxing. (3) In specimens dewaxed at high heaitng rate, there were a few void and larger interparticle spaces remaining after dewaxing. In contrast, smooth facet and ductile fracture mode were observed in specimens dewaxed at low heating rate.
社団法人粉体粉末冶金協会の論文