Introduction: The manufacture of Ferro Chromium involves the smelting of various ores and fluxes to produce the metallic product.
Slag is inherent in the process. It has a much lower density than the metallic FeCr. Some chrome may be trapped in the slag as either FeCr or Cr2O3.
Previous methods to estimate the slag in the FeCr have revolved around separating the slag and metallic portions by exploiting the differences in density. The downside with that procedure is that material will often contain pieces that are adhered FeCr and slag. The Metallic FeCr may also be completely encapsulated in the slag.
An alternative and more precise method involves calculating the slag content based on chemical analysis of Mg and Al. The Mg and Al will be at relatively low levels ( less than 0.1%) in the Metallic FeCr pieces and considerably higher in the slag (3% or greater). The overall sample will have a proportional amount and is calculated using simultaneous equations with the assumption there is only one kind of slag and one kind of FeCr present. “Pure” slag and “pure” FeCr metal are needed in order to determine the Mg and Al in each. The determination of the Mg and Al in the overall sample would then be used to calculate the amount of slag.
When the particle size is small, it is difficult to sample and get “pure” pieces of the slag and FeCr metal of sufficient quantity to perform a proper analysis. Often, historic data is used but that is dependent on the source of the FeCr and the materials used in its production. Mg and Al levels in slag can vary between 3% and 20% in different FeCr slags depending on their origin.
Authors: Robert Kozicki, George Wrightson, and Eric Graham
Keywords: Slag, Ferrochromium, Induction Furnace