Use of magnesian-dolomite mixtures in steel-melting furnace hearths and the mechanism of their wear in service. 1. Study of Ankerharth refractories

Abstract

The results of mineralogical-petrographic analysis of Ankerharth magnesian-dolomite refractory mixtures used in the hearths of steel-melting furnaces are described. The regularities of changes in their phase and chemical compositions are identified and the mechanism of their wear in service at the Omutninskii Metallurgical Works is considered.Refractory materials have a very significant role in ensuring reliable and safe performance of metallurgical plants and influence the quality and production cost of steel. Recently, steel-melting furnaces in the nonferrous sector have tended to grow in sizes and their service temperatures have increased; consequently, requirements imposed on the quality of melting have grown as well. Therefore, the significance of high-grade non-molded refractories has also grown, since they have to satisfy more severe operating conditions. The main properties of a refractory ramming mixture are the constancy of its volume at high temperatures, corrosion resistance, and wear resistance. Correct ramming of a furnace hearth increases the efficiency of the steel-melting furnace and extends the service life of its working chamber. Identification of negative factors affecting the service life of refractories, studying the mechanism of their wear, and selecting refractories with optimal properties remain topical issues. In this context, we have performed a comparative study of the wear mechanism of open-hearth furnace bottoms rammed by magnesian-dolomite mixtures of the Ankerharth and Jehearth grades supplied by foreign producers. The results of these studies are summarized in two papers. The first paper describes the study of the wear mechanism of Ankerharth materials produced by RHI AG (Austria) sampled after their service in furnaces at the Omutninskii Metallurgical Works.The main line of our research was studying chemical corrosion of refractories, which is one of the most significant factors influencing their resistance. The latter depends not only on the chemical and mineral composition of rammed lining and the composition of metallurgical melts, but also on the method and quality of ramming the furnace chamber and the location of refractories in the furnace hearth.The main purpose of this study was to investigate diffusion zonality arising in ramming mixtures when they react with molten metal and slag and to analyze the effect of changes in the chemical and mineralogical compositions of refractory materials in service on their resistance. To solve this problem we analyzed the chemical and phase composition, texture, and structure of samples taken from an openhearth furnace bottom before and after service correlated to different zones formed in the samples in the course of reactions between refractory materials and molten metal and slag. Our study was based on the principles of the metasomatic zonality theory developed by D. S. Korzhinskii [1] for natural processes and on our own studies of reactions between periclase-chromite refractories and nickel converter matte [2] and between mineral r...

Wear mechanism for periclase material in open-hearth furnace bottoms

“…Periclase is stable over the whole column with ferrous coefficients of 0.03 and it increases to 0.2 in zone 4. The presence in all zones, including the original mix, of titanium-containing phases distinguishes this column of refractory reaction with melt from previously studied columns [1,2], where Ti was an impurity element. In the zero zone of the composition the titanium phase is close to the stoichiometry of perovskite; with an increase in the intensity of the process the titanium phase becomes more aluminous.…”

“…In this work the wear mechanism has been studied for the bottoms of open-hearth furnaces during service using magnesia powders grade PPM-85 produced by OAO Kombinat Magnezit for ramming them. Ankerhearth [1] and Jehearth [2] magnesia-dolomite mixes produced overseas have been studied previously.…”

Use of magnesian-dolomite mixtures in steel-melting furnace hearths and the mechanism of their wear in service. 1. Study of Jehearth refractory mixture

“…The present study is the continuation of the preceding paper [1] and focuses on the refractory material Jehearth produced by the Slovakian Magnesite Works and used in the hearths of open-hearth furnaces at the Vyksunskii Metallurgical Works. We have also investigated the initial material, namely magnesian-dolomite mixture of grade Jehearth 30BA.…”

“…We have also investigated the initial material, namely magnesian-dolomite mixture of grade Jehearth 30BA. Materials were studied using the methods of optical and electron microscopy, microprobe, silicate, and x-ray phase analysis described in [1].…”

Technogenic mineral formation in refractory materials in the open-hearth process

“…During performance of this work the hearth wear mechanism was studied during service using for ramming magnesia powder grade PPM-85 (GOST 24862) of domestic production (OAO Kombinat Magnezit). Previously magnesia dolomite mixes grade Ankerhearth [1] and Jehearth grade [2], obtained from overseas enterprises, were studied for this purpose.…”