Abstract
In the stationary basic open hearth furnace used heretofore, which has a difficulty in substituting slags, the slag usually contains more than 10% of SiO2, so that there is a limit around 0·01% P and 0·02% S in the usual refining. However, the author made success in practising a Hoesch-system refining two times using a Merz-type open hearth furnace and managed to obtain a steel melt with 0·003-0·010% P and 0·006-0·012% S. The following are the conclusions from viewpoint of the actual operation:(1) It is recommended to keep the CaO/SiO2, in the slag to the second order in the first melting, to tap as soon as possible before the failure of the furnace bed, and, in the second melting, to make the highly basic slag with the CaO/Si02 of the fourth order as soon as possible.(2) Therefore, a considerable quantity of fluorite should be used to retain a suitable quantity of CaF2 in the slag.(3) The Mn in the steel melt should be retained at least up to 0·2% in the case of the second melting, to make the desulphurization effective.
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