パック法による鉄焼結体の硫化処理

Abstract

Sulfiding treatment of sintered iron has recently been practised in the technical field. Various methods of treatment have their merits and demerits, but most of them cause the public pollution. The packing method was selected for our experiments, because it causes little pollution in practical use. The study was made for the specimens treated by this method on their mechanical properties (mainly wear resistance) and the properties of the treated layers.The results of the experiments were as follows:(1) When NH4Cl and K4Fe(CN)6 were added to the sulfiding agent, the wieght of specimen increased with the increases in the amount of additives and heating time and the rise in heating temperature.(2) When KCNS was added, the weight of specimen increased with the increases in the amount of the additive and heating time; but the increase in the weight of specimen was maximum at the heating temperature of 500-600°C.(3) As the results of X-ray diffraction analysis of the treated layers, α-Fe and FeO were identified when NH4Cl was added; Fe4N, Fe3N, Fe2N, α-Fe, and Fe3C were identified when K4Fe(CN)6 was added; and Fe4N, Fe3N, Fe2N, Fe1-xS, and Fe3C were identified when KCNS was added.(4) The highest wear resistance within the range of these experiments was obtained by the addition of KCNS. The wear resistance after treating the specimen under the optimum condition (with 5% of KCNS at 550°C for 3hrs.) was as high as that of the specimen treated by the salt bath method.(5) After treatment of specimen with the addition of KCNS, the hardness and tensile strength increased; but surface roughness, impact value, and elongation decreased; and the dimensional change was about 0.2%.