On a Mechanism of Wear of the Periclase-Carbon Lining for Oxygen Converters

Effects associated with the capillary impregnation of the refractory materials with melted slag, the chemical interaction of graphite carbon with slag, and the dissolution of periclase in slag are considered. The time needed for melted slag to penetrate to the hot-layer depth of the refractory lining is a matter of several seconds. The carbon component on its contact with melted slag is reduced with FeO to yield CO. The partial pressure of carbon monoxide p _CO is calculated as a function of temperature (1500 – 1700°C) and FeO activity (0.1 – 0.5) in melted slag. The pressure p _CO is shown to exceed the capillary pressure of melted slag in pores, which prevents the easy penetration (because of the CO bubbles formed) of the slag into the periclase-carbon lining. The lining-wear effects due to the MgO concentration in the slag and to the size of periclase crystals are considered.     

Quality enhancement of refractories the bosh and lower stack of blast furnaces

Conclusions Impregnation of blast-furnace aluminosilicate refractories with carbon-containing substance makes their structure more compact and greatly enhances the quality. The open porosity of the impregnated specimens decreases by 42–47 rel.%, the gas permeability is reduced, the compressive stress (in the cold) is increased by a factor of 1.5–2, the onset temperature of deformation under a load of 2 kgf/cm² is raised by 50–100°C, the slag resistance is increased by a factor of 2–4 (depending on the amount of coke residue), the alkali resistance is enhanced owing to the presence of coke residue, which, by blocking off the chamotte grains from the active reagents (K₂O, Na₂O), promotes formation of more refractory mineral compositions in the form of large crystals of mullite and-alumina, cemented by refractory glass of presumably nepheline composition.This enhancement of the refractory properties as a result of impregnation with carbon-containing substance will increase the resistance of the lining of the lower stack and the bosh of blast furnaces.Translated from Ogneupory, No. 3, pp, 34–39.     

Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement

Four calcium aluminate cement mixes were manufactured from aluminum sludge as a source of calcium oxide and Al₂O₃ and aluminum slag (dross) as a source of aluminum oxide with some additions of pure alumina. The mixes were composed of 35–50% aluminum sludge, 37.50–48.75% aluminum slag (dross) and 12.50–16.25% aluminum oxide. The mixed were processed then sintered at different firing temperatures up to 1500 °C or 1550 °C. The mineralogical compositions of the fired mixes investigated using X-ray diffraction indicated that the fired mixes composed of variable contents of calcium aluminate (CA), calciumdialuminate (CA₂), calciumhexaaluminate (CA₆) in addition to some content of magnesium aluminate spinel (MA). Sintering parameters (bulk density, apparent porosity and linear change) and mechanical properties (cold crushing strength) of the fired briquettes were tested at different firing temperature. Refractoriness of the cement samples manufactured at the optimum firing temperature was detected. Cementing properties (water of consistency, setting time and compressive strength as a function of curing time up to 28 days of hydration) of pasted prepared from the manufactured cement mixes at the selected optimum firing temperatures (1400 °C or 1500 °C) were also tested. Cement mixes manufactured from 45 to 50% aluminum sludge, 37.50–41.25% aluminum slag (dross) with 12.50–13.75% alumina were selected as the optimum mixes for manufacturing calcium aluminate cement since they satisfy the requirements of the international standard specifications regarding cementing and refractory properties as a result of their content of CA (the main hydraulic phase in calcium aluminate cement) and CA₂(the less hydraulic but more refractory phase). Although the recognized high refractoriness of CA₆, its formation affect badly the cementing properties of the other non-optimum mixes.     

Resistance of blast furnace refractories to the action of aggressive reactants under conditions of an oxidizing gaseous atmosphere

Conclusions Investigations have been made of the resistance of ShPD-41, ShPD-39, and ShUD-37 chamotte refractories to the action of K₂CO₃, Fe₂O₃, blast furnace dust, and initial and final blast furnace slags under conditions of an oxidizing atmosphere. The investigation results showed that iron oxides and slag break down these refractories at 1400–1500°C. Dense ShPD-41 refractory is more resistant to the action of the reactants.The most resistant to the action of slags and iron oxides at 1400–1500°C are silicon carbide refractories with binders of silicon nitride and oxynitride.Translated from Ogneupory, No. 7/8, pp. 24–27, July–August, 1992.     

Influence of the aluminum oxide content of chamotte gunite masses on their slag resistance

Conclusions The authors investigate the influence of the aluminum oxide content of chamotte gunite masses on their slag resistance in contact with converter and synthetic slags. The refractory undergoes wear by dissolution of its surface in the fused slag; the slag does not penetrate very deeply into the refractory.A significant increase in slag resistance is observed only when the aluminum oxide content of the slag is 40% or more. An increase in the aluminum oxide content from 34–35 to 37–39% is not accompanied by a marked increase in the slag resistance. Linear regression equations with high correlation coefficients (0.70–0.98 in absolute value) have been constructed for different aluminum oxide content ranges.A more significant decrease in slag corrosion can be attained by introducing special additives into the chamotte mass composition.Translated from Ogneupory, No. 6, pp. 30–32, June, 1980.     

Resistance of corundum refractories to basic electric steel slags

Conclusions Upon reaction with slag corundum specimens exhibit a substitution of corundum by calcium hexa and di-aluminates. This process occurs most intensely in the bond part of the refractory and over the periphery of the fragment of fused corundum.The temperature of the eutectic between CaO·2Al₂O₃ and CaO·6Al₂O₃ is 1730 ± 10°C, and corresponds to the operating temperature of refractories in the slag belt of electric furnaces.The formation of calcium aluminates around the fragments of corundum and in the bonding part tends to reduce the refractories of the altered zones of material and the wear by fusion. Therefore corundum refractories are not reccomended for lining the slag belt of electric steel smelting furnaces.Translated from Ogneupory, No.5, pp. 41–44, May, 1970     

Preparation and properties of glass–ceramics derived from blast-furnace slag by a ceramic-sintering process

Glass–ceramics were synthesized using ground blast-furnace slag and potash feldspar additives by a conventional ceramic-sintering route. The results show 5 wt% potash feldspar can enhance the sintering properties of blast-furnace slag glass and the results glass–ceramics have desirable mechanical properties. The main crystalline phase of the obtained glass–ceramic is gehlenite (2CaO·Al₂O₃·SiO₂). A high microhardness of 5.2 GPa and a bending strength higher than 85 MPa as well as a water absorption lower than 0.14% were obtained.     

Refractory materials from aluminothermal reduction of niobium slag

Conclusions Slag from aluminothermal reduction of niobium meets the requirements imposed on the raw material for corundum refractory materials. Stabilization of the phase composition and the structure of the slag powder occurs in firing up to 1100°C. The low strength of 5-0.315 mm fraction grains is caused by oxidation of Nb localized in the volume and is eliminated by impregnation with orthophosphoric acid and subsequent heat treatment. A feature of the Al₂O₃-Nb₂O₅-H₃PO₄ refractory mixture is the low degree of crystallization and the formation of monosubstituted aluminum bihydrophosphate characteristic of aluminophosphate and aluminochromephosphate binders with increased adhesion. An optimum slag-base composition of refractory material with an 0.155 ratio of the weight shares of Nb and Nb₂O₅ was selected.Translated from Ogneupory, No. 1, pp. 24–27, January, 1993.     

Effect of molten basic open-hearth slag on the composition of the MgO-MgAl2O4-MgCr2O4 system

Conclusions We employed x-ray diffraction and petrographic analysis to study the reactions of molten basic open-hearth slag with compositions in the MgO-MgAl₂O₄-MgCr₂O₄ system.The phase transformations that occur during this interaction consist in solid solution of the iron and manganese oxides in the spinelides and periclase and a subsequent slight reaction between these solutions and the lime-silicate components of the melt.When combined with periclase, high-chromium spinelides absorb larger amounts of iron and manganese oxides than do high-alumina spinelides.Spinelides rich in magnesiochromite have the lowest slag resistance in the MgAl₂O₄-MgCr₂O₄ system.Addition of periclase to spinelides has a favorable effect on their chemical stability with respect to molten slag. However, combinations in which the spinel component consists of high-chromium spinelides are less stable.The degree of refractory breakdown produced by exposure to molten basic open-hearth slags is governed principally by the depth to which the melt penetrates. The chemical processes involved merely facilitate such breakdown.Translated from Ogneupory, No. 4, pp.48–52, April, 1969.     

A comparative study on the slag resistance of dense corundum-spinel refractory and lightweight corundum-spinel refractory with density gradient

Lightweight corundum-spinel refractory with a density gradient structure from exterior to interior was fabricated. Slag resistance of lightweight and dense corundum-spinel refractory is investigated by X-ray diffraction, scanning electron microscopy, energy dispersive analysis, mercury intrusion porosimetry and Factsage. The results show that lightweight corundum-spinel refractory with high apparent porosity exhibits comparable slag resistance to dense corundum-spinel refractory, especially with superior slag penetration resistance. The dense exterior with small pore size in the lightweight corundum-spinel refractory can effectively hinder slag penetration. Corrosion product phases (C₂S, CA₂, CA₆, and C₂M₂A₁₄) with high melting point and inconsistent melting temperature, most of Fe and Mn elements in steel slag solubilizing in spinel, especially strip CA₆ around corundum aggregate, prevent the refractory from further slag penetration and corrosion.     

Phase changes in zirconia refractories used in carbon black manufacturing

Conclusions The serviceability of zirconia blocks in carbon-black production chamber linings working with gaseous fuels is some 2 1/2–3 times better than that of magnesia-chrome refractories.During use, the exposed surface of the zirconia refractory is subject to slow decomposition of zircon with formation of ZrO₂ and SiO₂.Translated from Ogneupory, No. 5, pp. 24–28, May, 1969.     

Effects of La2O3 on the viscosity of copper smelting slag and corrosion resistance of magnesia refractory bricks

The rotating method is carried out to investigate the effects of La₂O₃ content (0–4 wt%) on the viscosity of copper smelting slag at high temperatures, the apparent activation energy is evaluated according to the Arrhenius equation and the structural characterization of this quenched slag is characterized by Raman spectroscopy. Meanwhile, the corrosion resistance of copper smelting slag with different content of La₂O₃ on magnesia refractory bricks is researched by employing a static crucible method. The experimental results show that the viscosity of copper smelting slag decreased with the La₂O₃ ratio increases from 0 to 3 wt% in a certain temperature range, which is because La₂O₃ simplifies the structural units of [SiO₄] tetrahedral groups. However, the melt viscosity increases after add 4 wt% La₂O₃, the reason is that more La₂O₃ addition improves the structural compactness of [SiO₄] tetrahedral groups in the molten slag due to the strong accumulation effect of La³⁺. Observation of the corroded samples found that the corroded magnesia refractory brick has a lower penetration index when the copper smelting slag with the content of 4 wt% La₂O₃. Therefore, the copper smelting slag containing 4 wt% La₂O₃ has a higher viscosity, and thus impeded the penetration behavior of copper smelting slag on magnesia refractory bricks.     

A Study of Refractories from Baddeleyite Stabilized with Magnesium Oxide

It is shown that refractory articles can be produced from ZrO₂ on a forsterite binder based on natural baddeleyite with native grain composition. The articles have a high density (4.71 – 4.72 g/cm³), ultimate compressive strength (257.6 MPa), heat resistance (6 – 8 water heat cycles from 1300°C), and a low porosity (12.2%).     

Slag-resistant products made from stabilized ZrO2

Conclusions The resistance of zirconia refractories to the action of acid slags is determined by the interaction between the added stabilizer and the silica component of the slag and by the rate of formation of the corresponding silicates. Of those materials studied, the most resistant of the action of the more acid slags is ZrO₂ stabilized by Y₂O₃.The rate of wear of the articles made from stabilized zirconia under the action of the more basic of the melts we studied is determined by the diffusion of Ca²⁺ into the structure of ZrO₂ forming CaZrO₃ which leads to the articles becoming less dense. The interaction between the stabilized ZrO₂ and the basic industrial slag, moreover, is accompanied by the intense dissolution of the refractory in the slag as a result of the formation of low-melting melts at the slag-refractory interface.Thus, zirconia refractories have an excellent resistance to the action of an acid multicomponent slag and are intensively damaged by basic slags.Translated from Ogneupory, No. 3, pp. 54–57, March, 1979.     

Gunited concrete linings of conveyer sintering machines

Conclusions The construction of unique heating equipment requires the development of composite programs with a single center of control, coordination, and financing of all work: scientific research, planning and design, construction and assembly, and start-up and adjustment. Further introduction of gunited concrete linings requires standard production by the refractory industry of guniting mixtures, for which successful use may be made of VTs-75 cement of ferroalloy production clinker, using additional working with the addition of special inspection on the basis of petrographic or x-ray diffraction analyses or on the basis of the criterion M (limits of variation 3.2–4.1). In mineral composition the clinker must meet the following requirements: 73–78.2% CaO·2Al₂O₃; 5% max·CaO·6Al₂O₃; 3% max· MgO·Al₂O₃; 6–9% CaO·Al₂O₃; up to 4% chromium regulus.As the result of the work conducted, a method was developed for guniting linings of various degrees of complexity with a refractory layer thickness up to 200 mm operating at a temperature up to 1450°C in an oxidizing, iron, gas, and dust atmosphere.The method may find wide use for lining of thermal equipment both in the steel industry and in other branches of industry.Translated from Ogneupory, No. 4, pp. 51–57, April, 1988.     

The action of slags of varied basicity on spinel - Periclase refractories

Conclusions In the action of slags of the Fe₂O₂-CaO-SiO₂ system on spinel-periclase refractories consisting of a filler and a binder the mechanism of erosion depends on the composition of the slag and the degree of erosion on the composition of the spinel party of the binder of the refractory.The essence of the chemical interaction of the refractory with the penetrating melt consists in the formation of solid solutions of periclase and spinels with the ferric component of the slag, and in the interaction of the periclase and silica in the presence of acid slags which results in the formation of forsterite; in the presence of basic slags it is primarily the spinel which is eroded and interacts with the calcium oxide, the result being the formation of calcium monoaluminate and chromite, and periclase.The erosion of the refractory depends largely on the stability of its bond; the periclase grains are affected only superficially by the processes of the interaction.When slags of different basicity act by turns on spinel-periclase refractories, the nature of the processes developing in the refractory as a result of the penetration of the melt is quite different. The chemical compounds formed in the interaction with the previous slag are dissolved in the melt penetrating into the refractory, i.e., the forsterite in the subsequent interaction with basic slag and the alumino- and chromocalcium compounds in the subsequent interaction with acid slag. The result is that the ratio CaOSiO₂ in the melt approaches two so that the chemical activity and solution capacity of the melt decrease. In this case the principal product of the crystallization of the melt is represented by monticellite.This investigation showed that in contact with melts in the Fe₂O₃-CaO-SiO₂ system a marked advantage lies with compositions which contain high-alumina spinels, the reason being the volumetric stability of these spinels to iron oxides.Translated from Ogneupory, No. 2, pp. 39–47, February, 1977.     

Some properties of sintered ceria ceramics

Conclusions Sintering of finely dispersed ceria occurs intensely in the 1300–1500°C range.In an atmosphere of inert gas and in vacuum the sintered CeO₂ is reduced with changes in crystal structure, which is accompanied by a reduction in the refractory and thermomechanical properties of the material.Unreduced CeO₂ is a highly refractory material which in oxidizing conditions can be used at temperature above 1900°C.     

Corrosion mechanism of magnesia-chrome refractory bricks with FetO-SiO2-Cr2O3 copper converter slag

The paper investigates the effect of Cr₂O₃ on the resistance of magnesia-chrome refractory bricks to copper converter slag. The static crucible method was employed to carry out the slag resistance experiment. The corrosion of magnesia-chrome refractory bricks under the action of Fe_tO-SiO₂-xCr₂O₃ (x = 0–5 wt%) slag at 1300 °C was discussed. The microstructure of the corroded sample was analyzed by XRD and SEM-EDS to elucidate the corrosion mechanisms of magnesia-chrome refractory bricks with Fe_tO-SiO₂-Cr₂O₃ slag. The results indicated that the permeability index of the slag-resistant samples gradually decreased with increasing Cr₂O₃ content in the Fe_tO-SiO₂-Cr₂O₃ slag. Combined with SEM and XRD characterization, the MgO in the refractory reacted with FeO and SiO₂ in the molten slag, leading to dissolution and reaction corrosion of the refractories. Meanwhile, forming a (Mg, Fe)O solid solution layer in corroded samples can prevent further chemical reactions and high-temperature dissolution between the Fe_tO-SiO₂-Cr₂O₃ slag and refractories. With the addition of Cr₂O₃ in the Fe_tO-SiO₂-Cr₂O₃ slag, the corrosion effect of slag on refractories was weakened, and the (Mg, Fe)O solid solution layer became thinner. The magnesia-chrome refractory bricks showed excellent slag resistance when the Cr₂O₃ content in the copper converter slag was 5 wt%.     

Electrophysical properties of fused baddeleyite-corundum refractories over the temperature range 1300–2300°C

Conclusions The temperature dependence of the resistivity of fused baddeleyite-corundum refractory materials over the temperature range 1300–2300°C lies between the resistivities of Al₂O₃ and ZrO₂ and is characterized by inflections which correspond to the phase transition from the solid to the liquid state.Translated from Ogneupory, No. 5, pp. 54–56, May, 1977.     

Dissolution behavior of a novel Al2O3-SiC-SiO2-C composite refractory in blast furnace slag

Al₂O₃-SiC-SiO₂-C composite refractories are interesting potential blast furnace hearth lining materials that feature several advantageous properties. In this study, the corrosion resistance of a novel Al₂O₃-SiC-SiO₂-C composite refractory to blast furnace slag was investigated by adopting a rotating immersion method (25 r/min) at 1450–1550 °C and comparing it against a conventional corundum-based refractory at 1550 °C as a benchmark. The results showed that the apparent activation energy of Al₂O₃-SiC-SiO₂-C composite refractory over the dissolution process in the slag is 150.4 kJ/mol. Dissolution of the Al₂O₃ and 3Al₂O₃·2SiO₂ phases appeared to be the main cause of Al₂O₃-SiC-SiO₂-C composite refractory corrosion. High-melting-point compounds in the slag layer formed a protective layer which mitigated the corrosion. The novel Al₂O₃-SiC-SiO₂-C composite refractory is better suited to blast furnace hearth lining than the conventional corundum-based refractory, because the carbon phase and SiC phase in the material are not readily wetted by the blast furnace slag and therefore are more resistant to slag penetration. Higher melting point phases also may crystallize on the hot face of the hearth lining due to the high thermal conductivity of the Al₂O₃-SiC-SiO₂-C composite refractory, promoting a more stable protective layer.