Abstract: In light of the problem of too long time in RH refining IF steel, the process status were investigated and analysised in Shougang Jingtang United Iron & Steel Co.,Ltd. It was concluded that low decarburization rate during early and last stage of decarburization was the controlling step. Therefore, some factors influencing decarburizationrate, such as vacuum pressure drop pattern, flow rate of blowing gas, scarp amount, initial carbon content in RH were optimazed. The results showed that prevacuum operation could eliminate the platform of pressure drop curve and enhance the early stage decarburization. Furthermore, gas flow rate was adjusted from 3 000 L/min to 3 666 L/min in the last stage of decarburization to increase the circulating steel flow rate as well as decarburization rate. It also showed that ending carbon content was sensitive to scarp addition. So the amount of scarp should be strictly controlled and added as late as possible. After taking these measures, the early and last stage of decarburization rate increase from 0.05 min-1 and 0.03 min-1 to 0.226 min-1 and 0.07 min-1, respectively. And the average ending carbon content and decarburization time decrease from 15.5×10-6 and 17.5 min to 10.2×10-6 and 14.4 min, respectively.

Key words: RH refining, decarburization, IF steel, decarburization rate