Application of Diffraction Pattern Refinement Software for Analyses of Oxide Layers on Refractories
M. Černík, S. Štulrajter, J.Bounziová
U. S. Steel Košice, s.r.o., Útvar GM pre
výskum a vývoj USSE, 044 54 Košice,
mcernik@ sk.uss.com, sstulrajter@ sk.uss.com, jbounziova@ sk.uss.com
Refractories used in the push furnace and casting ladles are not only exposed to high temperatures, but also to the oxide materials, which are present in liquid slag and steel. Knowledge about changes in the structure in that part of the refractories, which come into contact with the liquid slag, has practical importance in operation of these facilities. The numerous refractories are used in real practice, which have a common basis consisting of single oxides such as Al2O3, MgO, CaO, ZrO2, SiO2 etc., because these materials together with the carbon melt at high temperatures.
Oxides forming the slag based on elements as: Fe, Al, Ca, Si, Mg, Na, K etc., in many cases significantly affect on the basic refractory materials. A number of new minerals and phases with real structures form in the affected interactive locations, their heterogeneity and ability to penetrate into the structure of basic refractories is the subject of continuous study, in which X-ray diffraction method is very useful. The refinement of X-ray records by Rietveld method is considered an essential practice of real material structure study. The TOPAS and AutoQuant software, which were employed to clarify the diffraction patterns are very powerful tools and allow solving a very difficult tasks. In normal use of the Search-Match programs, it have been considered as good results when 3 to 5 phase were qualitatively determined from the diffraction record, currently the software combination allows accurate and quantitative determination of more then 10 phases in diffraction records. Experience shows that it is possible and necessary. In the figure 1 is shown an example the diffraction pattern of the refractory material in affected area, which in pure form contained only 75% Al2O3, 18% SiO2 and 5% ZrO2.
Figure 1. X ray record from the affected area of refractory material.
The reality of structure has been shown also with change of lattice parameter, which depends on material type and on the distance from the oxide layer surface. These changes can be observed mainly in the spinel structure. Changes in spinel structure affected by oxide layer are qualitatively and quantitatively presented for selected refractories.
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