Dephosphorization of Molten High Chromium Steel with CaC₂-CaF₂Flux

Abstract

The appropriate conditions for dephosphorizing 18% Cr molten steel in a crucible with CaC₂CaF₂ flux and the method to make the slag harmless were investigated in a 100kg induction furnace.
(1) When the initial [C%] is 0.5-1.8%, the degree of dephosphorization is high (50-80%) . The influence of the initial [C%] is explained by consideration of the amount of the remained CaC₂ and the ratio of (CaC₂) / (Ca).
(2) The suitable CaF₂% in the flux is about 10% when the temperature of molten steel is between 1 580°C and 1650°C.
(3) The slag after dephosphorization should be oxidized until (CaC₂%) becomes under 0.1% to prevent the generation of PH₃. For the purpose, two methods were investigated. One is to vapourize phosphorus from the slag by oxygen blowing. The other is to separate the slag from the dephosphorized steel, and subsequently to oxidize the slag in contact with plain carbon steel.