Synopsis:Decarburization of molten Fe-C-Cr steels by oxygen top blowing under reduced pressure has been studied in a 100kg capacity vacuum induction furnace. The results are summarized as follows:

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The /JalJer is a technical note for the continuous castillg of higlt alloy steels, esllecially of tlte stainless steel. Charactpristics of steels, facilities, operatiolls, defects alld their remedies, propertips ~f tlle /Jroducts, yield and cost of tlte products com/Jared with ingot making process are rlescribed respectively based on mallY research and invesiigatioll papers. Tlte outline of j alHUlese casters is surveyed through answers to tlte questionnaire sellt to domestic stainless steel makers.

D ecarburiz ation of molten Fe-C-Cr steels by oxy gen top blowing under reduced p ressure has been studied in a 100 kg capacity vacuum induction furnace. T he results are summariz ed as follows: (1) D ecarburiz ation process could be divided into three stages ; the fi rst stage in which decarburiz ation proceeds by the preforelltial oxidatioll of carbon, the second stage in which carbon and chromium in the bath are oxidized simultaneously, and the third stage in which the reaction p roceeds with the priferential oxida tion of chromium. The relationship between carbon and chro mium contents during the last stage was app roximately expressed by the fo llowing equation. log ([% Cr] /[% C]) =-12 500 l T + 9.04 (2) The oxygell ifficiency for the decarburiz ation during the first stage was found between 74 % and 78% for the F e-C melts and between 37~o and 64% for the Fe-CC .. melts. The ifficiellcy for Fe-C melts was hardly affected b), the bath temperature and blowing cOlldition, but that for the Fe-CC r melts illcreased with increasing in bath temperature and in the oxy gell-lance diameter and with decreasing in oxygen flow rate. (3) EX/Jerimental results on the oxygen balance and the apparent activatioll ellergy of decarburiz ation suggested that the reactioll JJroceeds with the reduction of iron and chromium oxides by carbon w hich were formed at the surface of molten metal cavity made by oxygen jet. It could be stated that the rate of decarburiz ation was affected not only by the oxygen flow rate but also by physical and chemical p roperties of splashes of the oxide alld metal p roduced by CO boiling. * R eceived August 2 1, 1974. ** Shuna n Works, N isshin Stee l Co. , Ltd. , Shin-Nan-yo 746. *** Nisshin Stee l Co. , Ltd ., M a runo uchi , Chi yoda-ku T okyo 100. CD ® Flow meter @ Low ra nge oxygen gas Pressure Ga uge a na lyzer Fig. I. Schem a tic diagram of experi menta l a ppa ratu s Research Article (353) (354) Transactions ISIJ, Vol. 15, 1975 * Bl owing cond itions: alumina la nce having 10 mm I.D., lance heig ht : 10 mm for all heats

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