鉄粉圧縮体の燒結現象の研究(II)
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概要
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1. 2. Study on the sintering process with the reducing reaction of oxide or slightly preoxidized powder compacts. Recent years, it was pointed out that the sintering process of powder compacts were promoted through some chemical reaction i. e. evaporation and condensation, oxidation and reduction among powder particles. Generally speaking, while the decomposion of metal oxide to metal and oxygen is the endothermic reaction, the combustion of hydrogen gas or that of carbon monoxide gas is the exothermic reaction. Then as the case may be, the reducing reaction of some metal oxide by hydrogen or by carbon monoxide is endothermic or exothermic. Above estimations were given to be sure experimentally by the anther as the temperature difference between metal and preoxidized powder compacts.<BR>In the last parts of this paper, studies were carried on the relation between the microstructure and heating conditions of oxide or slightly preoxidized powder compacts. Whether heating up rapidly or slowly under reducing atmosphere, corresponded to whether higher or lower in the sintering temperature and longer or shorter in the sintering time. Then it was revealed that conditions of the flow rate, gas pressure, the sort of furnace atmosphere and the content of CO<SUB>2</SUB> in CO, or H<SUB>2</SUB>O in H<SUB>2</SUB> influenced on microstructures as the factors of reaction rate, reaction heat and repetition of reversible reaction among capillaries of powder particles. Also suspension of vapour produced by reaction, accumulation of reaction heats in some parts of capillaries and heterogeneous crystal grain growth were influenced by the factors above mentioned. Then the chemical reaction among powder particles did not always mean to promote the densification of sintered compacts.
- 社団法人 粉体粉末冶金協会の論文