| In this work,several investigations of modeling in RH refining process and optimal design in RH equipments were carried out to achieve the RH efficient production,by which some valuable experiences on the development of refining technology of vacuum equipment was provided.The key factors for double working position treatment are the rapid replacement and connection of vacuum chambe,the design of vacuum pump,and the connection between the vacuum pump and vacuum pump.Compared with 31 RH1 the treat11ment time for 5#RH double working position can be reduced by 6 min.Moreover,the vacuum pumping capacity of 5#RH can reach 1200 kg/h and the vacuum chamber pressure can be reduced to 67 Pa within 3 rmin.The vacuum treatment time can be reduced by 2 min.The flow field of liquid steel during the refining process in the RH degasser can be obtained by using the established gas-liquid two phase flow model,and the results showed that the mixing and mass transfer process can be determined by the large circulation in ladle induced by down flow stream from down snorkel.The lifting gas can hardly reach the center of up snorkel and mainly locate near the side wall of up snorkel.The circulation flow rate can be increased by increasing lifting gas flow rate when the gas flow rate is smaller than certain value.The developed RH vacuum decarburization mathematical model can be used to simulate the variation of carbon and oxygen concentration in liquid steel with time during the vacuum refining process in RH.Top blowing oxygen operation can be used to enhance the decarburization rate,so the carbon concentration could be reduced to the target value in a shorter duration.However,the top blowing oxygen operation hardly increase the decarburization rate when the carbon concentration is lower than 300×10-4 mass%.Based on the mechanism of desulfidation reaction by injection of powder,the mathematical model of desulfidation has been developed and the simulated results agree well with the practical production data.It was also found that the desulfidation rate was elevated by increasing residence time of powder and decreasing powder size and gas flow rate.The industrial results exhibited that the desulfidation efficiency can reach 50%when the initial sulfur concentration in liquid steel is about 32.4t×10-4 mass%and the target sulfur concentration can reach the value of below 20×1014 mass%.For ultra low carbol steel,the target nitrogen can be controlled below 25×10-4 mass%,and the target oxygen can be controlled below 3O×10-4mass%.For pipe line steel,the target oxygern can be controlled below 20×10-4mass%.Furthermore,in 5#RH,the sulfur concentration can be decreased below 2×10-4mass%by high vacuum treatment for 16 min. |
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