Abstract
According to the Fe-P phase diagram, the solubility of phosphorus in α-Fe at 1050°C is known to be 2.8 wt%. This value is extremely large compared with the amount of phosphorus found in commercial steel. Therefore, it has been supposed that phosphorus in steel might dissolve in the matrix, and any phosphide phases such as phosphide-inclusions or phosphide-precipitations might not be present at all.
However, it has been confirmed in the present research that the solubility of phosphorus in α and γ-iron is remarkably decreased by the alloying of phosphide forming elements. From this experiment it should be concluded that phosphide phases are present in commercial steels containing the strong phosphide forming elements and in some cases, the phosphide-precipitation takes place, which is expected to play an important role in aging phenomena such as the temper-brittleness of alloy steels.
