| As one of the important refining equipments between steelmaking and continuous casting, RH can improve steel quality largely and meet the demand of mass production of high additional value. To ensure operation of RH regularly, conduct the single-link process smoothly, realize the high quality and low consumption and bring investment benefit into full play, researching and developing on RH and related process are important the technical innovation project of Liansteel.By taking the single-link process of RH in Liansteel as the research object, combining with the relevant theoretical analysis, investigation researching on RH related process and using the methods of mathematical statistics, decarburization, denitrogenation, temperature control, alloying and steel cleanliness were researched systematically in RH-MFB process. And yet, the influence of the related processing parameters to these factors were analyzed and the suitable technical parameters of RH-MFB process production in Liansteel were obtained to guide the on-spot work. Finally, the anticipated effect was achieved. Therefore, the main conclusion were as follows:(1)In order to meet the requirements of the production of RH, the tapping-carbon in converter was controlled in the range of 0.04~0.07%, the free oxygen was controlled below 0.08% and the tapping temperature was about 1680~1700℃. Thus, it was should be improved the operational level of BOF converter and the direct hit rate;(2)To maximize decarburization, eliminating pressure drop platform as possible, controlling reasonable argon flow and choosing suitable oxygen blowing parameters during treatment made the outlet carbon content was steady below 0.003%;(3)The nitrogen content in steel was 35.9×10-6 when entering into RH and 24.6×10-6 in the out station, and yet the nitrogen removal efficiency was 31.5% by taking some measures such as improving vacuum degree, carbon oxygen reaction under vacuum and increasing argon flow;(4)The temperature drop was obvious in 5~10min at the beginning of refining. The feeding amount of aluminum of most heats in practical production process was basically identical with the calculated values, but the values of Al addition for heating and the practical temperature rising made a great difference in that the influence of factors such as the temperature measurement time, thermal hysteresis and so on. The proper tapping temperature of RH should be controlled in the level of 1580~1590℃;(5)The yielding rate of Mn had a larger fluctuation and the average yield was 96.06%. It was could further improve the yielding rate through adjusting the addition opportunity namely adding ferromanganese in the after of 2~3min when added aluminum block, disposing the bunker promptly and so on;(6)After RH-MFB vacuum treatment, the total oxygen removal rate is 90.23%(reference value) and the denitrogenation rate is 31.5%. To reduce T[O] in steel furtherly and alleviate nitrogen absorption phenomenon of steel, the measures such as controlling tapping slag amount of converter strictly, improving absorbing inclusion capability of ladle slag, improving argen sealing effect of long nozzle were implemented;(7)The micro inclusion amount of the larger than 10μm in liquid steel was decreased significantly and the size in comparison with before refining became smaller after RH-MFB refining. And in consequence, the quality of molten steel was improved;(8)Matrix was aluminum oxide inclusion as the main micro inclusions in liquid steel during RH-MFB refining process, which had dissimilar characteristics of the shape and appearance. Especially, the micro morphology of aluminum oxide inclusion existed mainly as spherical and clumpy in late process. The quantity of large inclusions was 14.32mg/10kg in the steel when leaves RH and the large inclusions was mainly by SiO2, silicate and TiO2.
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