Study on the Dephosphorization in Alloy Steel

Abstract

The dephosphorization in alloy steel was investigated for Fe-C-Cr-P alloy chiefly with high basic and fluid slags.
At first, the experimental heats were made by induction melting the Fe-Cr-P alloys in lime crucibles under various oxidizing conditions. In this case, the relation between the contents of chromium and phosphorus nearly followed its equilibrium relation calculated under the condition of both a₄CaO·P₂O₅=1 and aFeO·ECr₂O₃=1, and the dephosphorization in a few per cent chromium steel was not improved in this condition.
Then in order to investigate the effects of CaF₂ and FeO concentration in the slag and temperature on the dephosphorization, the Fe-C-Cr-P alloys were melted in MgO crucibles with CaO-CaF₂-FeO slags.
For dephosphorization in alloy steel, less oxidizing condition in slag is desirable to restrict the oxidation loss of alloy constituents. As a result of a series of experiments, it was found that the synthetic slag at CaO: CaF₂=5: 5 could fairly promote the dephosphorization at the least concentration of iron oxide, and in the course of its process, for the medium carbon alloy steel containing several per cent chromium, the oxidation loss of carbon and chromium could be remarkably restricted.