Refining molten steel to obtain very low manganese content - by vacuum decarburising, then oxidn. of manganese, used e.g. to mfr. silicon electrical steel sheet

摘要

The steel is subjected to (a) refining; (b) vacuum decarburising; and (c) oxidn. of Mn by a refining gas (c1) under a slag contg. lime. Step (a) pref. results in a melt contg. 0.02-0.08% C and 0.1-0.25% Mn. Gas (c1) is pref. technically pure O2, and step (c) is pref. undertaken at reduced pressure. Step (c) is pref. undertaken under an acid slag obtd. by adding Si to the melt before or during step (c), and/or by adding silica to the top surface of the melt or slag before or during step (c). A low cost method of reducing the % Mn avoiding the long refining time, high iron loss, and high converter lining wear involved with conventional methods.