Abstract
The dimensional change behavior of the system Fe-2wt%Cu-0.8wt%C-0.75wt% zinc stearate was investigated under an atmosphere of dissociated ammonia and the results were compared with those of endothermic gas. The sintering process was divided into three stages ; delubricating, heating and cooling, and the sintering conditions were varied in each stage.
The decrease in the heating or cooling rate and the increase of dew point in an atmosphere caused shrinkage at all the stages. These behaviors in dissociated ammonia were very simple and in numerous cases differed from those in endothermic gas. The shrinkage was mainly caused by the decarburization, which began soon after reaching maximum temperature. "The modified carbon transfer theory " can be also considered to be appliciable to other sintering atmospheres. This theory is that the carburization during temperature rise contributes to the shrinkage but after reaching maximum temperature it contributes to the expansion and that the decarburizing have an opposite action of the carburizing.
