Oxygen Converter/DM (Duo Vortical Mixing) Steelmaking

Abstract

The DM reversible shaking of a vessel is very effective for mixing the melt with slag owing to the active mixing action (duo vortical mixing) compared with the Kaldo and Rotor processes.
An investigation was made on the refining reaction which resulted from the combination of slag-metal reaction by DM operation and gas-metal reaction by LD operation in one vessel.
In the LD/DM combined process, the respective conditions of oxygen blowing and duo vortical mixing can be independently varied. The experiments under various conditions were to find the optimum condition for rapid refining to low phosphorous steel.
The conditions of experiments were as follows:
Using one-slag practice,
i) simultaneous operations of LD and DM,
ii) simultaneous operations of LD and DM, followed by LD operation only, and
iii) LD operation only, followed by the simultaneous operations of LD and DM.
Using two-slag practice,
i) simultaneous operations of LD and DM, followed by LD operation only, and
ii) LD operation only, followed by simultaneous operations of LD and DM.
The experimental results were as follows:
1. The rate of dephosphorization during the LD/DM operation in the first stage of refining was two times as rapid as that during only the LD operation in the same stage.
2. The dephosphorization during the LD/DM operation in the first stage of refining proceeded prior to the decarburization. For example, phosphorous content in bath decreased to 0.003 to 0.004% at 2% carbon in bath.
3. It was proven that the control of refining reactions of the melt could be made by optional combination of the conditions between oxygen blowing and duo vortical mixing in the case of the LD/DM operations.