Argon–Oxygen Decarburization of High‐Manganese Steels: Effect of Alloy Composition

The kinetics of simultaneous decarburization and demanganization of Fe–Mn–C alloys with 5–25% Mn and 0.05–0.42%C are investigated by bubbling a mixture of Ar–O 2 through the melt at 1823 K. There are three distinct stages during the process. In stage 1, the rate of decarburization is slow, it is faster in stage 2, and slows to an intermediate rate during stage 3. In stage 1, manganese concentration decreases at a constant rate. In stage 2, manganese concentration remains essentially constant or exhibits minor reversion in some cases. In stage 3, manganese concentration decreases again. The overall rate of manganese loss in stage 1 increases with decreasing initial carbon concentration of the alloy, whereas in stage 3, the rate of manganese loss is independent of carbon concentration. The rate of overall manganese loss is partly controlled by the transport of manganese in the liquid phase. Assuming the products of reaction are CO and MnO, the combination of loss as vapor and oxide is insufficient to justify the total Manganese loss. The mechanism for the extra manganese loss is proposed to be due to evaporation–condensation of manganese in the bubble, is supported both thermodynamically and kinetically.