V. N. Boricheva

Zircon-quartzite and zircon-clay refractories

ConclusionsThe authors have investigated the properties of zircon-quartzite and zircon-clay refractories. They have established that the use of both quartzite and zircon in the masses permits the preparation of refractories which expand during heating and have a fairly high refractoriness and softening point under a load of 0.2 MPa; in this connection regeneration of quartz and dissociation of zircon are not intensified. The best quality indices are displayed by specimens containing more than 60% of zircon.Refractories obained from zircon and clay have a high rate of sintering and a higher compressive Strength. There refractoriness and softening point under a load of 0.2 Mpa of specimens with less than 60% Zircon are low,owing to the accelerated decomposition of zircon in the presence of clay and to the resulting high content of the vitreous phase. The thermomechanical indices of the refractories increase with the zircon content.

The durability of acoustically tested SP-11-type mullite-corundum stoppers

ConclusionsAn investigation carried out at the Novolipetsk Metallurgical Plant of the performance of the SP-11-type mullite-corundum stoppers produced by the Semiluk Refractories Plant showed that the durability was highest in the case of stoppers with a resonance frequency of 10,000–12,000 Hz. The stoppers falling into that frequency range account for about 70% of the total output.Culling out the stoppers with resonance frequencies below 10,000 and above 12,000 Hz and the “deaf” stoppers by acoustic testing increases the performance reliability of the stoppers of pony ladles and lengthens their useful life by 0.25 melt.

An automatic instrument for investigating the elastic peoperties and controlling the quality of refractories

ConclusionsThe design of an automatic resonance-frequency gage (ARFG) has been developed and a property has been produced.The instrument can be used for measuring the frequencies and for determining, on the basis of correlations, other parameters of the product concerned. The precision (±1.5%) and reliability of these measurements are higher than can be achieved in nonautomated testing.The speed and simplicity of the frequency-measuring process makes possible the continuous monitoring of the phase conversions in refractories during heating or cooling. The ARFG can be used for flaw and crack detection and for piece-by-piece quality control in automatic production lines for special-purpose refractories.

Zonal change in the properties of magnesite brick after service in the roof of an open-hearth furnace

SummaryThe coefficients of expansion of original magnesite brick and also of all zones formed in it during service in an open-hearth roof are practically equal. These real data constitute further proof of the benefit of examining and clarifying the complex ideas connected with the mechanism of wear of basic refractories with change in coefficients of expansion of the working zone owing to saturation by iron oxide.Destruction (scaling) of magnesite brick in the roof occurs mainly as a result of thermal strains developing as a result of the presence of temperature gradients in the brick. The melt of iron oxide may here play a cementing role, filling the thermal cracks that are formed. This is indicated by the existence of high strength properties of the hot zone of the used magnesite brick compared with the unchanged zone (a three-fold increase in compressive strength and a reduction in porosity from 21 to 6%).

New apparatus and method for testing refractories under tension at high temperatures

ConclusionsAn improved method and apparatus for high-temperature testing of refractories for tensile deformation has been developed and introduced.Some experimental data were obtained characterizing the behavior under tension of firebrick, magnesite, unfired magnesite-chromite and silica refractories at high temperatures.The apparatus can be used for testing refractories under tension both with constant load and increasing temperature and in isothermal conditions.The apparatus and method are recommended for the accumulation of experimental material on different types of refractories, and also for work on the development of goods subjected to tensile strains in service at high temperatures.

Elastic and thermal properties of magnesite-chrome brick which has been used in open-hearth furnace roofs and artificially saturated with iron oxide

ConclusionsThe elastic and thermal properties of roof basic refractories which have been artifically saturated with iron oxide and have served in a roof do not reveal any great changes, compared with the initial brick; hence it should be considered the importance attributed to the differences in the properties of zones of chrome-magnesite refractories, forming through the action of iron oxides as the dominating factor in cracking bricks during temperature variations is an exaggeration.