Effect of the charge of "Komori" iron sand on the properties of "Tamahagane" steel produced by "Tatara" operation

The Tatara furnace, so called Nittoho Tatara, was reconstructed in 1977 based on ''Yasukuni Tatara" which had been worked before the end of the World War II. Mr. Yoshizo Abe as a leader "Murage" developed the new techniques of direct steelmaking, "Kera-oshi" for Tatara operation only using "Masa" iron sand for the 3 stages of "Komori", "Nobori" and "Kudari". Until the age of "Yasukuni Tatara", the operation had been carried out in 4 stages with "Komoritsugi" following "Komori", and in the first two stages: the "Komori" and "Komoritsugi" iron sands with higher (Fe2O3)/(FeO) ratio had been used, respectively. In the present work, 7 Tatara operations with 3 stages were carried out using "Komori" iron sand or "Masa" iron sand for the "Komori" stage followed by the last two stages using "Masa" iron sand. The operation using "Komori" iron sand produced more amount and higher carbon content of "Tamahagane" than that only using "Masa" iron sand, because "Komori" iron sand was reduced easier than "Masa" iron sand.