Use of microwave electromagnetic oscillations for nondestructive testing of refractories

Bernshtein, R. S.; Sloushch, V. G.; Mil'shenko, R. S.; Levchenko, Yu. V.; Red'ko, G. S.

doi:10.1007/bf01290601

Refractories

1970

DOI: 10.1007/bf01290601

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Use of microwave electromagnetic oscillations for nondestructive testing of refractories

R. S. Bernshtein

V. G. Sloushch

R. S. Mil'shenko

et al.

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1978

1986

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Cited by 4 publications

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“…The measurements at % = 3.935 cm were carried out in an INF-2 instrument [5] using horn-type antennae with an aperture of 2.4 x 2.4 cm; the measurements at X = 0.884 cm were carried out in equipment assembled from standard units in accordm~ce with the diagram in Fig. i; horn antennae with an aperture of 2.6 x 1.8 cm were used.…”

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Dependence of the dielectric properties, porosity, and apparent density of quartz ceramic on the phase of composition

et al. 1982

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666.762.2.017:620~!79oi T. I. Litovskaya, and S. P. Shmitt-FogelevichThe formation of cristobalite during the preparation of articles made from quartz ceramic leads to the emergence of cracks in the articles and to a loss of strength [i] as a result of the ~ + B cristobalite transition on cooling.As a result, the properties of the articles are degraded in use.It is therefore necessary to eliminate as far as possible the supply to the customer of products in which a critical amount of cristobalite has been formed.Sometimes the formation of cristobalite leads to cracks which emerge on the surface of the article.In that case defective articles can be revealed by visual inspection.Since the reasons for the formation of cristobalite may vary and be associated with very slight and unrecorded deviations in the production process, the output of articles in which the concentration of cristobalite goes beyond permissible limits is random in character.At the present time there are no inspection methods which make it possible to reveal~ reliably and immediately, those articles which contain cristobalite.Normally under laboratory conditions the concentration of cristobalite is determined using an x-ray method [2] but for several reasons this cannot be used for production control.According to [3,4] as well as from some theoretical considerations, the emergence of cristobalite must produce a change in the dielectric properties of a quartz ceramic. This fact may be used as the basis of a method which makes it possible to organize on-line production control of the concentration of cristobalite in the articles.The aim of the studies described in the present paper was to investigate the dependence of the dielectric properties, porosity, and density, on the phase composition of the ceramic.The studies were carried out on cylindrical specimens made by a slip-casting method. As the starting materials we used vitreous silica with a mass fraction of SiO2 > 99%. The specimens were fired in a furnace with silicon carbide heaters at a heating rate of 200~ with a 3-h dwell.It was possible to produce specimens with different concentrations of cristobalite by changing the firing temperature between I150~and 1300~ The open porosity (Pop) and apparent density (Papp) of the specimens were determined in accordance with GOST 2409-80; the concentration of cristobalite was determined using an x-ray method.Samples were prepared by quartation down to 2-5 g and milling in a chalcedony mortar to particles <0.063 nun. The measurement error in the concentration of crystalline phase depends on the amount and extent of defectiveness in the cristobalite [2].The dielectric properties of the specimens were studied in the UHF range at wavelengths of % = 3.935 and 0.884 cm.The measurements at % = 3.935 cm were carried out in an INF-2 instrument [5] using horn-type antennae with an aperture of 2.4 x 2.4 cm; the measurements at X = 0.884 cm were carried out in equipment assembled from standard units in accordm~ce with the diagram in Fig. i; horn antennae with an ...

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Dependence of the dielectric properties, porosity, and apparent density of quartz ceramic on the phase of composition

et al. 1982

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“…The dielectric method consists in measuring the displacement of the phase of the radio~ wave (8) passing through the specimen. The ratio of the magnitudes of the displacementlof the phase of the wave before (8,) and after (82) the action on the specimen of the molten slag enables us to assess the slag resistance.…”

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“…The countlngof the displacement of the phase 8 is done with the INF-2 apparatus [8,9]. The specimens to be studied are placed between the radlowave radiator and the receiver, which takes the form of speaker systems.…”

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Slag resistance of refractories for evacuators

et al. 1986

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Increasing the number of usages of the refractories in the plants designated by points located to the right and above the line in Fig. 4 requires taking of measures related to correcting the design of the gate or improving the method of production of the slide plates, CONCLUSIONSThe optimum pressure on the contact surface of the slide plates in assembly of a gate is 0.8-1.2 MPa.It is necessary to install elastic compensating elements in the plate-bolts systemfor the purpose of limiting the unavoidable change in the specific pressure in manipulatlon of the gate.Before repeated use of the slide gate without replacement of the refractories the optimum pressure between the plates must be restored.It is necessary to increase the travel of the movable plate in the gate in order to provide a relative neck length of 3-5 mm for each shut-off.

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“…For nondestructive testing of the mechanical properties (open porosity, apparent density, and compressive strength) of refractory artifacts made of dielectric materials, at the All-Union Institute of Refractories (VIO) we have developed a radio-wave phase (uhf) method [3][4][5] based on measurement of the velocity of transmission of radio waves through the test articles.…”

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Radio wave phase method of quality control for refractory slabs for sliding gates

et al. 1979

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In pouring steel from ladles, successful use has recently been made of sliding gate valves in which the crucial elements are refractory slabs [i]o These slabs operate in stringent conditions, and therefore severe technical requirements are imposed on them (TU [2]~ The present quality control of these slabs, which involves testing two specimens from each batch of 400 sets for mechanical strength and open porosity, is inadequate for reliable estimation of the production of crucial components.It is necessary to check each slab separately, as each set has to permit stable pouring of 130-700 tons of steel.In this article we describe the results of investigations on nondestructive quality control of composite (MSP-95) and biceramic (MPB-95) magnesite (peric!ase) slabs .For nondestructive testing of the mechanical properties (open porosity, apparent density, and compressive strength) of refractory artifacts made of dielectric materials, at the All-Union Institute of Refractories (VIO) we have developed a radio-wave phase (uhf) method [3-5] based on measurement of the velocity of transmission of radio waves through the test articles.The method is contactless and permits local monitoring, i.e., measurement of the properties in a limited zone determined by the area of the beam (ray) of electromagnetic radiation.The velocity of transmission of radio waves is measured by means of the phase change of the wave passing through the article relative to that for passage along the same path in air.When radio waves pass through an infinite dielectric medium with low loss (in which the dielectric loss angle tangent is tan ~ < 10-2), the relation between B and the dielectric constant of the medium [6, p. 44] is as follows: 2=where % is the wavelength in free space, in centimeters; c, relative dielectric constant; and d, geometrical path length of the wave in the dielectric medium, in centimeters.We can approximately assume that the radio waves pass through a layer in the articles. Consequently, the relation between B, e, and ~ will take the formwhere r = --4~d ;and ~m is the measured phase lead [7].Since the dimensions of the monitored articles can vary, as the parameter (to be measured by the nondestructive method) by which the properties of an article is to be judged (on the basis of a calibration graph) we choose the corrected phase lead,

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Use of microwave electromagnetic oscillations for nondestructive testing of refractories

Cited by 4 publications

References 0 publications

Dependence of the dielectric properties, porosity, and apparent density of quartz ceramic on the phase of composition

Dependence of the dielectric properties, porosity, and apparent density of quartz ceramic on the phase of composition

Slag resistance of refractories for evacuators

Radio wave phase method of quality control for refractory slabs for sliding gates

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