Process Metallurgy Slag Properties
The slag properties describe the capability of a slag to take up sulfur from the metal melt. The Process Metallurgy Module defines so-called phase groups. These contain all phases of a certain kind, for example all solid slag or all slag phases. The component composition of such a phase group is calculated by weighting the component composition of each phase with their fraction in the group.
This allows to calculate slag properties for the phase groups, for example for the overall slag.
Various predefined slag properties such as different definitions of slag basicity, sulfur capacity and so forth are available for plotting or tabulating. On the Process Metallurgy Calculator when selecting axis variables on the Plot Renderer or choosing the properties to list with the Table Renderer, there is an option to include these slag properties.
The associated quantity selected from the next drop-down list has these options: All, B2, B3, B4, Bas2, Bells ratio, Ls, or Log10(Sulphur capacity). Also choose In liquid slag only, In solid slag only, or In all slag. Depending on this setting, the composition averaged over liquid, solid, or all slag is applied as a basis for the slag property calculation. Example PMET_01c is used for the figures below, where a table was added to one of the calculators.
Slag properties for a Table Renderer.
Slag properties for a Plot Renderer.
Equations and References
The equations and references for the slag properties are defined below. Composition can be given in mass (% or fraction).
The formulas are given in Thermo‑Calc console-like syntax (B: mass, W: weight fraction, AC: activity). A slag property is available if all of its components are present in the phase group. Steel and slag are the actual phase groups chosen depending on the user request, i.e. the slag property can be calculated for the liquid slag only or for the overall slag (liquid and solid).
Basicity is defined as:
Sulfur capacity is defined as:
References
Basicity and MgO Saturation: For definitions of the basicity and MgO saturation properties B2, B3, B4, and Bells ratio see [2015Kes]. Also see the Slag Atlas [1995Ver].
Sulfur Distribution and Capacity: For definitions of the sulfur distribution properties Ls see [1999And]. For the sulfur capacity, see Slag Atlas [1995Ver].
[1995Ver] Verein Deutscher Eisenhuttenleute (VDEh), ed. 1995. Slag Atlas 2nd Edition. Dusseldorf, Germany: Verlag Stahleisen GmbH.
[1999And] Andersson, Margareta A. T., Par G. Jönsson, and Mselly M. Nzotta. 1999. “Application Ladle Slags of the Used Sulphide Capacity Concept on High-Basicity in Bearing-Steel Production.” ISIJ International 39 (11): 1140–49.
[2015Kes] Keskitalo, Björn. 2015. “Model Studies on the Effects of Composition Differences of Direct Reduction Pellets and an Adaptive Addition of Slag Formers for the EAF Process.” Master's thesis, KTH Royal Institute of Technology, http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168296.