Dephosphorization and Decarburization of High Carbon Iron Melts by Sodium Carbonate

Abstract

In order to get a basic knowledge concerning dephosphorization of hot metal by soda ash, the behavior of phosphorus and carbon in metal and gases evolved during the reaction was examined.
Sodium carbonate explosively reacted with liquid iron containing 3 5% carbon. Gaseous material evolved by the reaction was only carbon monoxide.
When sodium carbonate was added to liquid 4%carbon-0.2%phosphorus-iron, dephosphorizing reaction rapidly occurred within the first few minutes. While, decarburizing reaction began at around the period when dephosphorization was almost completed. Only a small amount of carbon dioxide gas evolved early in the experiment, gaseous material evolved over a run was mainly carbon monoxide.
It was presumed from the relation between the amounts of carbon monoxide gas evolved and phosphrus removed that the dephosphorizing reaction of high carbon iron melt can be expressed as follows ;
5Na₂CO₃ + 2P = 5Na₂O + P₂O₅ + 5CO
The reactions ofdephosphorization and decarburization were retarded by the addition of sodium disilicate together with sodium carbonate.
It was found that the phosphate capacity of high sodium carbonate flux was very low compared with those of Na₂O- SiO₂ fluxes.