Abstract
The effect of sulfur on the dimensional change during sintering was examined by using two different water-atomized iron powder groups with about 0.01 and 0.3mass% sulfur. The compacts of Fe-2mass%Cu-0.8mass%C-0.75 mass% zinc sterate were sintered in endogas and those of the Fe-C system were sintered in Hz and Ar to investigate the mechanism.
In endogas in the case of the high sulfur powder, the suppression of the carburization by the atmosphere occurred in the α-Fe region and that by graphite occurred in γ-Fe, and the copper growth increased leading to more expansion during sintering. The suppression of the carburization also occurred in H2 and Ar in the case of the high sulfur powder, whereas it occurred only in Ar in the case of the low sulfur powder. By sintering Fe-C compacts containing excess graphite in Ar, it was found that the carbon solubility in γ-Fe decreased with increasing sulfur content in iron powder.
The addition of FeS to the low sulfur powder brought about the suppression of the carburization and an extreme expansion in comparison with MnS. The mechanism was discussed from the view of thermodynamics.
