Mathematical modeling of the argon-oxygen decarburization refining process of stainless steel: Part II. Application of t
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A new mathematical model for the argon-oxygen decarburization (AOD) refining process of stainless steel was proposed and presented in Part I of the present work.[1] This model has been applied to the industrial practice of the austenitic stainless steel making (including ultralow-carbon steel) and tested on data of 32 heats obtained in producing 18Cr9Ni-grade steel in an 18-t AOD vessel, to examine its reasonability and reliability. The results are reported in this article. I. APPLICATION OF THE MODEL TO INDUSTRIAL PRACTICE AND RESULTS
SOME of the related data of 32 heats obtained in producing 18Cr9Ni-grade austenitic stainless steel (including one heat of the ultralow-carbon steel) in an 18-t AOD vessel and the corresponding operations are given in Table I. The relevant total average absolute pressure in the bath for an 18-t AOD vessel ( pt) was 1.32 atm. When the model is applied to a practical refining process, the remaining two parameters will be concerned. One is the utilization ratio of oxygen in the blowing process. It is fairly difficult to determine this parameter. This problem has been investigated by Gorges et al.[2] Referring to their results, the oxygen utilization ratios in the first, second, and third blowing periods for the refining process of austenitic stainless steel were, respectively, taken to be 0.90 to 0.95, 0.75 to 0.85, and 0.30 to 0.40 in the present work. Another parameter is the melting time of the added crop ends and scrap or alloy JI-HE WEI, Professor, is with the Department of Metallic Materials, Shanghai University, Shanghai, 200072, People’s Republic of China. DE-PING ZHU, formerly Graduate Student, Department of Metallic Materials, Shanghai University, is Engineer, Shanghai Wensi Sorftware Limited Company. Manuscript submitted January 9, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS B
agents, i.e., the time lapse of their cooling effect. It is just a research subject and has been reviewed by Oeters.[3] For simplicity, in the present work, based on the available theoretical and experimental studies and considering the flow and mixing characteristics in the AOD bath,[4] the melting time was taken to be 300 to 1200 seconds, according to their added amounts and the bath temperature at the time of addition. The concentrations of carbon and chromium and the temperatures at the endpoints of blowing periods predicted by the model, with the relevantly observed values of carbon content and bath temperature, are shown in Table II. II. ANALYSIS AND DISCUSSION OF RESULTS A. Deviations of Results Predicted by the Model from Determined Values It can be seen from the data given in Table II that, so far, as the carbon concentrations and bath temperatures at the ends of blowing periods are concerned, the predicted results are in excellent agreement with the determined values. For period I of blowing, the maximum absolute deviations are 0.0083 mass pct and 15.84 K, and the relative mean deviations are 1.81 and 0.42 pct, respectively; for periods II and III of blowing, the maximum absolute deviatio
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