GB1451106A - Metallurgical process - Google Patents

Abstract

1451106 Recovery of chromium from slags UDDEHOLMS AB 23 May 1974 [25 May 1973] 25050/73 Heading C7D Oxidized chromium in the slag from the refining of a Cr-containing melt may be recovered by separating the slag from the refined melt and reducing the Cr oxides with silicon, into the next charge of Crcontaining material. The preferred process involves the steps of (a) refining by blowing a Cr-containing melt in a converter (b) removing the metal (c) adding a fresh charge, containing sufficient silicon to reduce the Cr oxides, to the slag remaining in the converter (d) removing the depleted slag after reaction, (e) refine the new charge by blowing and forming a new slag (f) removing the metal, leaving a Cr-oxide rich slag which is treated as in (c). A modification which separately removes both slag and metal after blowing as in (a) above, is described wherein the slag is treated with a part of the new charge which contains the bulk of the Si required for reduction, the depleted slag being removed prior to returning the metal to the converter where the remainder of the charge is added and the whole melt refined. The process requires slags with a minimum of 10 wt. per cent of Cr oxide, and since other elements present in the oxide form i.e. Ni, Mn, Mo etc, will be reduced back by the silicon addition, the process is suitable for making alloy steels as well as stainless steels containing chromium. The silicon content required is calculated, and in the case of Cr should preferably be at least one-half the Cr content of the slag, with more if other oxides are to be reduced, extra silicon being added as ferrosilicon if necessary.