微細不均質組織を呈する射出成形4600鋼(熱処理材)の機械的諸特性 Mechanical Properties of Injection Molded 4600 Steels(As Heat Treated) with Fine Heterogeneous Microstructure
In our previous studies on the 4600 steels produced by Metal Injection Molding (MIM) process using mixed elemental powder, the fine heterogeneous microstructure caused by the agglomeration of spiky Ni powders was reported to be significantly effective for the static and dynamic fracture properties. In this study, the effects of heat treatment condition and different type of Ni powder on the mechanical properties of injection molded 4600 steels using prealloyed and mixed elemental powders were investigated to secure the efficacy of the fine heterogeneous microstructure. The obtained results are as follows:<BR>1) The heat treated steels using the prealloyed powder showed the homogeneous tempered martensitic microstructure, while the steels using mixed elemental powder showed the fine heterogeneous microstructure consisted of tempered martensitic matrix and martensite or retained austenite phases, which were caused by the segregation of Ni powders.<BR>2) For the tempered steels at 473K, the fine heterogeneous microstructure contained Ni rich phases was effective for the tensile and fatigue strengths. On the other hand, there was not clearly seen the efficacy of the heterogeneous microstructure in the tempered steels at 823K because of the homogenization.<BR>3) The agglomeration of Ni powders with spherical shape investigated with the debound steels was fewer than that of Ni powders with spiky shape, which lead the decrease of Ni rich phases even in the heat treated steels, resulted in poor tensile strength.
粉体および粉末冶金 44(11), 1014-1018, 1997-11-15
Japan Society of Powder and Powder Metallurgy