Calcium wire injection in steel melt: Modeling of calcium recovery under industrial operating conditions

A mathematical model has been developed to analyze the melting behaviour of cored wire filled with CaSi and CaFe powders when injected into steel melt under industrial operating conditions. Calcium (Ca) recovery obtained from steel samples under industrial operating conditions at an integrated steel plant has been correlated with the model-predicted distance traversed by the cored wire under those conditions for CaSi and CaFe filled cored wire. Calcium recovery was found to increase as the wire approached the ladle bottom and then decreased as the distance travelled by the cored wire exceeded the bottom of the ladle. Under the industrial operating conditions, the model-predicted distance traversed by the CaSi cored wire was found to lie beyond the ladle bottom for the majority of the industrial heats, which are correlated with the actual calcium recovery values that are estimated from steel samples collected before and after wire injection. It was demonstrated that a higher bath superheat would be required to melt the CaSi cored wire near the ladle bottom than the CaFe cored wire. It was found that the Ca recovery from CaSi cored wire could reach as high as 20-30% when the wire melts at the bottom of the ladle, which is substantially higher than the maximum Ca recovery of 6% observed for CaFe cored wire under similar operating conditions, even when the CaFe wire also melts at the ladle bottom.