L. D. Bocharov

Fused periclase−chromite-base parts for steel ladle degassers

ConclusionsThe possibility of production of PKhP parts to TU 14-8-368-81 from a mixture of combined ground fused Periclase-chromite with the crust has been shown.These parts may on an equivalent basis replace standard PKhP parts produced from scarce fused periclase-chromite in the wall lining of a circulation degasser of Novolipetsk Metallurgical Combine. It is desirable to continue production of experimental lots of PKhP parts of a combined ground mixture of fused periclase-chromite with the crust and to test them in the zones of a circulation degasser lining with more severe service conditions (bottom, snorkel) and also to test them in batch and circulation type degassers for the purpose of studying the possibility of use of these refractories in place of standard PKhP parts.The introduction of PKhP parts of a combined ground mixture of fused periclase-chromite with the crust makes it possible to eliminate the costs of manual labor for separation of the crust from the fused periclase-chromite and for sorting of the block and to increase the yield of acceptable periclase-chromite for the production of PKhP parts by not less than 20%. To provide stable quality of such parts careful control of the chemical composition of the raw material of fused Periclase-chromite with the crust used for production of parts is necessary.

Periclase-spinel products based on sintered materials for vacuum treatment of steel outside the furnace

ConclusionsA technology was developed for periclass-spinel, low-silica chrome-concentrate (SiO2 <1.5%) and sintered periclase (MgO 91–92%, SiO2 < 3%). As regards the resistance in the walls of the metal zone of circulation vacuum equipment, these refractories are not inferior to PKhP periclase-chromite goods made from fused materials.In the production of PShKh articles it is recommended that titanium additives be used to ensure sintering of the chrome-concentrate to a low porosity, and to stabilize the properties of goods made with it.It is desirable to make wider tests of these refractories in vacuum units of different types. The introduction of PShKh articles based on sintered materials in the walls instead of PKhP articles should reduce the consumption of scarce fused materials for vacuum treatment and cut the costs of the linings.

Scrap of magnesia parts, the reasons for it, and means of reducing it

ConclusionsThe most common and characteristic forms of scrap of magnesia parts differing in form, dimensions, and composition are shown. These include deviations of the dimensions from the nominal, breaking off of the corners and edges, nonuniformity, welding together, spots, voids, fire cracks, spalls, and cracks of different origin.The reasons for formation of scrap were determined. The primary of them are the reduced quality of the raw material (chromite, magnesite) with a larger quantity of impurities containing limited silicon and calcium oxides, sometimes insufficient density, grain size, and completeness of hydration of the magnesite powders, nonconformity of the bunker, proportioning, mixing, and pressing equipment to the requirements of modern production of progressive high-quality refractories, the insufficiently high binding capacity of lignosulfonates, deviations in the quality of assembly and finishing of press equipment and automatic ejectors, of the car floor lining, and in firing conditions, a high variation in density of the green parts, and nonuniform heating and cooling in the volume of the parts and of the whole charge during firing. More than 50% of the total scrap of all forms is due to firing scrap of parts.The primary means of reducing or eliminating scrap of parts and simultaneously increasing their quality based on the reasons for formation of different forms of it were noted. These above all else, are increasing the volumes and improving and introduction of new methods of concentration of magnesite and chromite, a successive increase in the share of chrome concentrates, chromium-containing broken parts, and powders by firing of magnesite and caustic dust in the production of magnesia refractory parts as the result of a decrease in the share of commercial natural chromite and magnesite, the use in the production of parts of high-quality type PMSP-93 powder produced in shaft kilns and used as the charge for production of fused materials, the use of the prospect of processes for production of dense periclase powders uniform in chemical analysis from recovered caustic dust, replacement of obsolete mixing and press equipment by more modern, increasing the strength of green parts by above all else improving the binding properties of LST and increasing pressing pressure, forming of the taper of parts by the side plates of the die, improving the quality of assembly and increasing the reliability of functioning of press equipment and automatic ejectors, improving car floor linings, introduction of new methods and increasing the volumes of production of progressive unfired refractories in place of certain forms of fired parts, observation of all production parameters, and a relationship of the wages of labor to the quantity of scrap and the quality of refractories.Introduction of the new management system and the active work of the quality groups created will open up and lead to the action of unutilized reserves for reduction of scrap.

Fusion-cast periclase-spinel materials for granular structured refractories

On etudie la fusion au four electrique et le moulage par coulee de refractaires de periclase-spinelle, ainsi que la composition chimique et mineralogique et la microstructure des produits obtenus

Microstructure and chemical composition of the phases of the fused low-silica chromite-periclase materials

In order to produce chromite (chrome)-periclase bearing refractories having a low silica content, one makes use of beneficiated concentrates of chromium ores or synthetic chromiumbearing materials [i, 2] Which require presintering or prior melting because of the fine dispersion of the products of benefieiation and synthesis. It was previously shown [3, 4] that fused materials can exhibit significant differences in the structure and that ferrochromium has a negative effect on the service properties of the products.

Mineral composition, structure, and properties of high-temperature strength high-purity periclase-spinelide refractories

ConclusionsA dense synthetic high-chrome spinelide with a low silica content was obtained.Based on this spinelide and high-purity materials, a method was developed for periclasespinelide refractories with a dense structure and high indices of heat resistance, strength, and volumetric stability at service temperatures. The refractories are intended for lining the slag belt of the vacuum ladle of a unit for vacuum treatment and refining of steel.

Influence of the size of voids, impregnation with bakelite, and heat treatment of periclase plates on their properties and life in steel pouring ladle valves

ConclusionsThe relationship of the properties, the quality of the ground surface, and the wear resistance in service of the refractory plates in the gates of steel teeming ladles to the size and form of the voids, impregnation, and heat treatment of periclase plates was established.

Wear of magnesia spinel refractories in portion vacuum-processing steel plant

ConclusionsThe processes of wear in the lining of vacuum chambers of outdoor-furnace vacuum-treatment plants (UPVS) are due to the simultaneous action of high temperatures, deep vacuum, gaseous medium, molten metal, and slag. The corrosion and erosion of aggressive melts of slag and metal are the decisive forms of wear.Laboratory investigations established the relationship between slag resistance in vacuum and the ratio of corrosive and erosive constituents in the wear of different magnesia-spinel refractories and their phase composition, structure, and properties.Refractories obtained from fused periclase-chromite material with a low content of fusible silicates showed that in laboratory vacuum equipment and during service in the linings of the vaccum chamber of industrial plant they have higher slag resistance and lower wear than refractories based on sintered magnesite, spinel, and chromite ores.

Change in the structure and properties of magnesia goods fired in industrial kilns

The p r o p e r t i e s of r e f r a c t o r i e s and the i r behavior in s e rv i ce a r e se r ious ly affected by the p r o c e s s e s that occur in f ir ing [1]. To d i scover means of improving the qual i t ies of magnes ia r e f r a c t o r i e s it i s impor tan t to know how the s t ruc tu re and p r o p e r t i e s a l t e r during heat t r ea tmen t in the va r ious zones of the industr ia l ki lns used to f i re them.

Refractory wear in sliding gates of steel-teeming ladles

ConclusionsAs a result of chemical and petrographic investigations of periclase and corundum plates and collectors, tested in sliding gates of steel-teeming ladles, the authors have established the disintegration mechanism of refractories and given a comparative estimate of their wear.The different zone-formation characters, chemical-mineralogical, and structural changes of the working zones of the refractories indicate that periclase plates are more durable than corundum ones during teeming of metal with a high temperature (more than 1600°C) from large ladles, and also when the gate is in the closed position for the least possible time.Corundum plates exhibit negligibly small wear during teeming of metal with a lower temperature (1580–1590°C) from ladles holding no more than 140 tons.