A study of the formation of sialon in a charge based on the Ovruchsk quartzite and fine aluminum powder established that the density of the products increases with increasing content of the aluminum fines in the body (from 40 up to 60%). The material fired at 1450°C in nitrogen atmosphere consists ofβ-sialon, corundum, and a small quantity of aluminum nitride and silicon oxynitride as impurities.

We worked out the technology of sialon-containing silicon carbide refractories for lining the shafts of blast furnaces. It was shown that addition of MgO in combination with the waste products of the oxides of the rare-earth elements improves the strength and the other properties of the products fired at 1550°C in nitrogen atmosphere.

It was established that silicon-carbide refractories with bonds of silicon nitride and oxynitride, and also self-bonded silicon carbide articles possess 2–3 times higher elasticity moduli compared with chamotte (firebrick) refractories.

The effect of alkalis, slag, and carbon monoxide on silicon carbide and nitride was studied at elevated temperatures up to 1550°C. It was established that silicon carbide is destructed most rapidly at 1200°C under the action of the investigated factors. The properties of silicon nitride virtually do not change on heating up to 1400°C in the presence of carbon monoxide; one observes a slight decrease in the nitrogen content of the system only at 1550°C and an increase in the silicon content in the 1200–1550°C range due to the dissociation of Si3N4 and the formation of Si2ON2.

The effect of the type of mullite on the sintering process of mullite-zircon specimens was studied. It was shown that using electromelted mullite as chamotte ensures optimum properties. Sintered mullite increases the porosity of the products.

At the Chasov Yar refractories combine we developed and introduced a technology for the production of chamotte kaolin refractories with a porosity of not more than 12% and a mass proportion of not less than 42% Al2O3 on the basis of chamotte from high-grade Polozhe kaolin, and also additions to the batch of finely milled mullite-corundum chamotte.

During service differentiated changes in properties and structure of the refractories across the thickness of the lining occur in the lining of the blast-furnace hearth. The most intense processes under the action of the slag and the gaseous medium occur in the working zone of the lining, which leads to a reduction in open porosity of the refractory to 6–10%, an increase in apparent density to 2.40–2.45 g/cm3 and in the compressive strength to 80–132 MPa, a decrease in the mullite content, and the formation of up to 12% glass, melilite, calcium ferrites, anorthite, and other minerals.

Conclusions Chamotte obtained by calcining Novoselitsk kaolin in a rotary kiln, upon repeat heating to 1550°C and with a soak of 6 h gives an expansion of up to 9.6%, as a result of the expansion of the gaseous phase located in the closed pores and of the action of local reducing conditions during rapid heating of the kaolin.

The physicomechanical properties and phase composition of chamotte depends on the composition of the gas medium, the firing temperature, and the cooling regime. In the briquettes fired at 1500°C in an oxidizing medium with the cooling temperature lowered from 1500 to 1200°C, the apparent density increases and the porosity decreases. In the briquettes fired in a reducing medium with the cooling temperature lowered from 1500 to 1300°C, there is a reduction in the apparent density and an increase in the porosity but with a further reduction of the cooling temperature to 1200°C, these properties change in the opposite direction.

Investigations of the reaction of kaolin refractories with synthetic slag have shown that under isothermal conditions erosion of sintered kaolin refractories with a porosity of 12% by slag increases with a decrease in its basicity from 1.8 to 0.65. The corrosiveness of the slag increases with an increase in temperature from 1300 to 1500°C and with an increase in the FeO content; with an increase in the density of the refractory, its erosion by the slag decreases; the contact zone between the refractory and the synthetic slag has a complex mineral composition and consists of anorthite, pyroxene, magnetite, dicalcium ferrite, corundum, ferriferous spinellide of complex composition, etc; reaction of fused kaolin refractories with the slag is observed only at their contact, with formation of anorthite, magnetite, manganous spinel, and complex spinellides in the slag.

As a result of the study of the sintering kinetics of a refractory made from chamotte from Novoselitsk kaolin and a mixture of this chamotte with a plastic clay, a method of calculation has been established which makes it possible to determine for chamotte and crock with strictly specified properties, the required apparent crock density and the temperature and duration of the firing in order to obtain particles with a specified density.

The Ukrainian Institute of Refractories has developed a technology, and the Chasov-Yar Factory is mastering the manufacturing methods, for dense kaolin refractories with a porosity of not more than 12% for blast furnaces. The bricks are made with high-fired chamotte using Novoselitsk and Polozhe kaolins. Firing is done in tunnel kilns with a setting height of 1.95 m.

A technology was developed for the production of high-density kaolin refractories with a porosity not over 10%. Trial batches of these refractories were produced at the Zaporozhe Refractories Plant.

The magnitude of the wetting angle of molten cast iron on aluminosilicate refractories depends on the structure, phase composition, and physicochemical properties of the solid material and the melt. An increase in the temperature from 1140 to 1500°C causes the wettability of the refractories by molten cast iron to increase as a result of the increase in the content and chemical activity of the liquid phase in the refractory.

The investigation showed that the resistance to the action of blast-furnace slag and cast iron is highest for blocks of fused Bakor, sintered kaolin refractories, and fused kaolin.

The principal production parameters for fused kaolin were determined and the properties and phase composition of the product were determined. Fused kaolin is highly resistant to the reducing effect of synthetic slags of the primary blast furnace type and to alkali valor at 1400°C.

The formation of the black core in large kaolin bricks during the firing process is caused mainly by the reducing medium which develops in the central part of these high-density refractories, graphitizes the carbon, and converts some of the high-valence iron and titanium oxides to low-valence oxides. The principal sources of the reducing medium inside the brick are the spent sulfite liquor and the sulfur- and carbon-containing impurities of the starting material. The likelihood of a black core being formed increases with the density of the green product and the rate at which the kiln temperature is raised.

A comprehensive comparative analysis of the principal properties of the refractories used for the lining of blast furnaces showed that the ShKD-type kaolin refractories produced by the Zaporozhe Refractories Plant possess the highest property indices and can be recommended for use under the heavy-duty service conditions in the lining of blast furnaces.