Development And Application Of Decarburization Model Of Molten Steel For RH Process

With the analysis on the ultra-low carbon steel production process in a steel corporation and investigation on thermodynamics and Kinetics of RH vacuum decarburization, a RH decarburization online model describing the decarburization theory was established. On-site production process was optimized to improve the decarburization accuracy and reduce production costs, which enhanced the competitiveness of high value-added steel products in the world and bring significant economic and social benefits.The main contents and conclusions are as follows:(1) With the investigation of the thermodynamics and kinetics of RH vacuum and research on decarburization mechanism of molten steel, the RH decarburization mechanism model was built. This model was divided into three stages and liquid steel in the device was subdivided into five parts. The decarburization location for the contribution of total decarburization amount was set by the parameters.(2) An on-line predictive model based on the mechanism model and the production process was developed. By verification in the production site, the model hit rates were as follows:In the20validation furnaces, there were18furnaces whose hit rate was in±8×10-6,10furnaces whose hit rate was in±5×10-6,3furnaces hit the±2×10-6and one which was invalid. The hit rate had basically reached the requirements, and it would be better after optimization.(3) Production process was optimized by the on-line predictive model. At the early stage, the pressure in the vacuum chamber reached the ultimate vacuum in3minutes by increasing the pressure drop rate, which would improve the rate of decarburization and reduce the time. When the gas flow was improved from1500NL/min to1700NL/min, the liquid steel circulation flow rate increased from80.1t/min to83.8t/min, which would improve the decarburization rate. The initial carbon content and the average oxygen content after decarburization should be controlled in300-450×10-6and300×10-6respectively, which would effectively reduce the oxide inclusions. By optimizing the decarburization process, decarburization time was reduced about2minutes and the efficiency was obvious.