Mathematical Model for Decarburization of Ultra-low Carbon Steel in Single Snorkel Refining Furnace

Abstract

A dynamic model is developed to investigate decarburization behavior of a new type of refining equipment named Single Snorkel Refining Furnace (SSRF) in treating ultra-low carbon steel. Decarburization reactions in SSRF are considered to take place at three sites: Ar bubble surface, the bulk steel, and the bath surface. With the eccentricity of the porous plug (r e/R S) and the ratio of the snorkel diameter to the ladle diameter (D S/D L) of SSRF confirmed, circulation flow rate of molten steel is obtained through combined effects of vacuum pressure and gas flow rate. Besides, variation of the steel temperature is simulated associated with generated reaction heat and heat losses. The variation of C concentration with treatment time is divided into three stages in accordance with decarburization rates and the simulated C concentration is in reasonable agreement with actual production data. In the present study, both decarburization rates at three sites and their contributions to the overall decarburization at each stage are estimated for the first time. Through the present investigation, it is clear that vacuum pressure significantly influences decarburization efficiency of SSRF primarily by affecting the depth of CO nucleation in the bulk steel. Besides, effects of gas flow rate on decarburization rate of different stages are obtained and the opportunity of increasing gas flow rate during the treatment period has been clarified. The present model provides an efficient tool to comprehend the decarburization process in SSRF.