AN EXPLANATION FOR THE EFFECT ON STEELMAKING OF TITANIUM IN HOT METAL

摘要

The current wave of interest in this topic is the result of increased use of titaniferous ores or ilmenite in blast furnace burdens for the purpose of repairing hearth damage. The titanium compounds that promote deposition of "patching" materials in blast furnaces are the cause of downstream problems in the steelmaking shops.rnSteelmakers historically have objected to significant amounts of titanium in hot metal ( > 0.10 % Ti) for several reasons: 1) accretions caused by the TiC.TiN needles that float out of the iron as it cools in transit and in transfers make the accompanying slag sticky and crusty, causing problems in desulfurization and increasing time and Fe yield loss at the subsequent raking, 2) defensive measures have been taken in treatment, such as use of argon for carrier gas, but without technical rationale for this approach, 3) difficulty in removal of the ladle slag by the raker, with subsequent sulfur addition to the vessel charge, and 4) transfer into the BOF and/or formation of a very corrosive TiO_2 containing acid slag during the early part of the BOF blow which, in addition to causing lining damage, results in loss of sulfur removal capability by the vessel slag.rnBased on a conceptual analysis of the metal-slag-atmosphere interactions during transfer ladle desulfurization treatment, a mechanism is postulated for the apparent effectiveness of the use of argon in reducing the deleterious effect of titanium and an alternate technique, possibly more effective, is proposed. As probably the use of argon causes increased exposure to atmospheric oxidation of the titanium carbonitrides contained in the ladle slag, the same benefit can be obtained by use of either oxygen or an air blast to oxidize the noxious reaction compounds.rnValidity of the concept has been demonstrated in a pilot plant setting. These issues, and related effects on testing the hot metal, are examined in detail with reference to the literature and plant and laboratory experience.