RU2223237C2 - Method of production of multi-layer porous glass ceramic block and articles made from such block - Google Patents

Abstract

FIELD: production of glass ceramic materials; manufacture of building structures. SUBSTANCE: proposed method includes loading the charge in heating zone in form of several discrete layers formed beyond heating zone and melting them together by means of thermal shock. Forming the subsequent layer is performed at stage of viscous glass phase in previous layer. Loam and/or clay is used for at least one layer. Rate of heating is selected within 415-1450 C/min. For dividing the block into members of required shape, grooves are made on its surface at depth of 0.1-1.0 of its thickness and are filled with initial charge or refractory loose material. Articles thus obtained may be covered with decorative or protective layer. EFFECT: enhanced strength characteristics at retained heat-insulating properties. 2 ck, 1 tbl, 2 ex

Description

The invention relates to the production of glass-ceramic materials with desired properties and products from them and can be used in the manufacture of heat-insulating building structures.

A known method of producing foam glass, including the cooking of glass in a controlled atmosphere at a temperature of 1350-1510 ° C (1-2 hours), grinding it together with a blowing agent, secondary heat treatment at a temperature of 700-800 ° C and annealing [a.s. USSR No. 1158511, MKI S 03 S 11/00, 1985].

The production of foam glass blocks requires increased energy consumption for grinding, secondary heat treatment and molding operations, and the resulting structures have relatively low strength properties.

A known method of obtaining a porous vitrified block, according to which a silicate-containing material without adding glass and foaming ingredients is continuously loaded into the heating zone with a temperature of 1060-1300 ° C and foamed at the same time as the feed, providing heating at a speed of 180-400 ° C / min [RF patent No. 1787965, publ. January 15, 1993].

The disadvantage of this method is the inability to obtain porous blocks with the required strength characteristics. This is due to the uneven flow of the charge into the heating zone, especially when molding large items. The thickness of the molded block cannot be increased by increasing the heat treatment temperature, because a thick layer of porous glass melt begins to play the role of an effective heat insulator. The temperature increase in the deeper zones of the charge slows down, which prevents the sintering process. An increase in the thickness of the molded product under the mentioned conditions leads to the formation of zones with a low content of glass phase up to the lack of connectivity. Cracking of products is possible both at the cooling stage and during operation, which limits their use as load-bearing structures.

Known close in technical essence, "A method of manufacturing foam glass and a device for its implementation" (AS USSR No. 753795, publ. 07.08.1980), which allows to obtain a laminated foam glass with a thickness of 80-120 mm In the method, a foaming mixture is used as the mixture, which is preheated, layer by layer loaded into the heating zone and foamed, and before the formation of the next layer, the surface of each previous layer is melted, which ensures their sintering (selected for the prototype).

The disadvantages of the method include the increased energy costs for preheating the charge in the loader and for melting the layer, the inability to get a block with the specified strength and thermal conductivity parameters at the output. In the prototype method according to A.S. No. 753795, as in the method according to the patent of the Russian Federation No. 1787965, a "hot" load is used, in which the upper layers under the action of gravity compress the plastic lower ones, which increases its bulk mass and reduces porosity. In addition, the traditional technology for producing foam glass at a temperature of 700-800 ° C does not allow to achieve an intense supply of thermal energy. When heat is slowly supplied, a large amount of gases is necessary for foaming, since part of the gases formed breaks through the pore walls, leaves the glass phase, and is irretrievably lost. Therefore, the mixture used in the prototype method contains foaming ingredients.

These disadvantages of the prototype method should be eliminated.

The objective of the invention is to increase the strength characteristics of the block while maintaining its heat-insulating properties and the ability to obtain multilayer products of any thickness. To this end, it is necessary to organize the foaming procedure of some layers in such a way as to ensure the advanced formation of the glass phase relative to the crystallization process.

The problem is solved in that the charge is loaded into the heating zone in a batch manner, forming layers of a given thickness outside the heating zone and fusing them onto each other, and the formation of the next layer is carried out at the stage of viscous glass phase in the previous layer, ensuring reliable adhesion of the layers, the layer heating speed is selected in the range of 415-1450 ° C / min, providing it with a choice of temperature and setting the heating rate. After reaching the required thickness, the block is stabilized at a glass transition temperature for a time sufficient to equalize the thermomechanical stresses, and is cooled in a predetermined mode.

Comparison with the prototype shows that the inventive method contains distinctive features, the combination of which with a number of features of the prototype is sufficient to solve the problem. Firstly, the layer is formed from a cold charge and outside the heating zone. Secondly, they use the heating rate of the layer in the range 415-1450 ° C / min, which changes the balance of energy consumption and the foaming pattern itself. With this method of forming a block, the following positive results are achieved:

- due to the rapid cooling of the surface of the previous layer, an increase in viscosity and stabilization of the porous structure of the lower layer occurs. This is facilitated by both heat transfer to the atmosphere (outside the heating zone) and heat transfer to the cold charge layer. This cannot be achieved with continuous "hot" loading, when the upper layer under the action of gravity compacts the plastic lower layer, reducing its porosity, which does not allow to obtain the estimated thermal conductivity of the insulating layer;

- an increase in the rate of supply of thermal energy to the charge mass changes the foaming pattern, namely, the growth rate of the layer volume is higher than the sedimentation rate of the porous glass phase (gas escaping);

- the selected mode of heat treatment of the layer allows you to do without adding foaming (gas-forming) ingredients to the mixture and obtain foamed glass ceramics directly from natural loam and / or clay;

- the ability to control the process of pore formation in the claimed range of heating rates allows you to obtain the specified strength characteristics of the block while maintaining its heat-insulating properties. This effect is achieved by combining high-strength layers in the block, which act as stiffeners, with porous layers.

In addition, it becomes possible to mechanically align the foamed surface and remove inhomogeneities (expanded sections) characteristic of heat treatment at high heating rates. In the prototype, this is possible only by compacting the surface of the previous layer with a roller, while outside the heating zone, the processed products (waste) are easily removed.

The lower limit of the range of heating rates (415 ° C / min) is due to the fact that lower heating rates are accompanied by the formation of a significant amount of crystalline phase, worsening the sintering of the material, up to a break in connectivity, and the melting of newly formed crystals requires much higher temperatures than the initial charge . The upper value of the rate of supply of thermal energy to the charge mass (1450 ° C / min.), Limited only by the fact that the sedimentation rate of the porous glass phase begins to exceed the growth rate of the volume of the layer (the latter circumstance is due to the breakthrough of the pore walls by the gases formed).

The resulting material is a porous glass-ceramic, i.e. porous glass with uniformly distributed inclusions of crystals both contained in the feedstock and newly formed.

Based on the proposed method, a particular technical problem is solved. At the stabilization stage, the block, if necessary, is cut into products of specified sizes. Cutting can be done by sawing with carbide or abrasive saws or by splitting. In the latter case, it is advisable to artificially create local inhomogeneities of internal stresses in the thickness of the material. For this purpose, depressions of the required direction with a depth of 0.1-1.0 of its thickness are made on the surface of the layer and filled with their initial charge or refractory bulk material, for example quartz sand. This operation, in addition, helps prevent uncontrolled cracking during the cooling stage. Production waste is crushed and used as a heat insulating filler of building compositions. The resulting products can be given additional consumer properties. So, when surfacing a protective or decorative layer, fusible materials, mainly capable of crystallization, such as ground glass, are used as a charge. An inorganic dye in an effective amount is added to the decorative layer, if necessary. The possibility of implementing the method is illustrated by the following examples.

Example 1. On a rigid heat-resistant base, a layer of loam and / or clay with a thickness of 20 ± 5 mm is formed, it is moved horizontally and fed to a thermally insulated heating zone, where it foams. The foaming process of the charge is accompanied by intense absorption of thermal energy. The optimum temperature of the heating zone is maintained based on the balance of thermal energy and providing a temperature above the sintering temperature. The selected intensity of thermal shock is achieved by the ratio of the temperature of the heating zone (1050-1450 ° C), the thickness of the layer (15-30 mm) and its feed rate (0.01-0.1 m / s). The output is a porous material of a homogeneous structure, which is in a viscoplastic state. A second layer of cold charge is poured onto its surface, the height of which is not necessarily equal to the height of the first. The workpiece is moved to the initial position for the first layer, or the base is turned 180 ° in the horizontal plane for reverse feed, after which the process is repeated. Obviously, for different layers, the heat treatment mode can be different. A block up to several meters long can be molded in a heating zone of a passage type, while not all of the layer is exposed to heat treatment, but some part of it, equal in area to the heating zone. However, with the selected heat treatment mode, all sections of the layer receive the same amount of thermal energy. In the particular case of a three-layer block, the outer (bearing) layers were obtained at a heating rate of 415 ± 5 ° C / min, and the inner (heat-shielding) layer at 1450 ± 10 ° C / min. It is essential that all the steps described in the example are carried out until the stage of stabilization and cooling of the lower layer, while the glass transition process has not yet been completed to ensure reliable sintering of the material when heated and the layers are bonded into a single block. The resulting workpiece (cake) size of 0.6 x 1.6 m and a thickness of 65 to 108 mm is stabilized and cooled in a given mode. The finished product is a porous three-layer glass-ceramic plate that can withstand a vertical compressive load of up to 7.5 MPa (75 kg / cm ² ) and is suitable for supporting structures.

Example 2. A loam layer is formed, it is leveled using a transverse scraper to a thickness of 25 mm and fed to a thermally insulated heating zone at a speed of 0.1 m / s. Under the influence of a powerful flow of thermal energy, the mixture melts with simultaneous foaming. At the exit from the heating zone, a porous material of a homogeneous structure, which is in a viscoplastic state, is obtained. The workpiece is kept for some time in atmospheric conditions so that the surface acquires sufficient viscosity. After that, irregularities of the front and end surfaces are removed, and one longitudinal and several transverse grooves are made on the front surface with a selected step, for example, 0.5 m (future separation zones), which are filled with the initial charge. Without changing the heat treatment mode, the described process is repeated. The resulting workpiece is easily divided by crushing into blocks of specified dimensions, which stabilize and cool. As a result, light multilayer blocks of uniform porosity with dimensions of 0.065x0.5x0.5 m are obtained, suitable for use as a heat-insulating building material.

To connect the layers into a single block, the formation of the subsequent layer is carried out at the stage of a viscous glass phase in the previous layer. The quality of the sintering of the layers depends on the heating rate. The adhesion strength of the layers was determined by the results of shear deformation of the samples cut from the block. It was found that at heating rates of 415 ° C / min and higher, fracture always occurs in the bulk of the layer with increased porosity, which has lower strength, while at lower heating rates, regardless of the duration of the heat treatment, fracture occurs along the layer interface, which speaks of insufficient caking. This was the basis for choosing the value of 415 ° C / min as the lower limit of the claimed range of heating rates. The upper boundary, as explained above, is limited by the fact that the sedimentation rate of the porous glass phase begins to exceed the growth rate of the layer volume. An increase in the heating rate above 1450 ° C / min is impractical, since it is accompanied by a decrease in the heat-insulating properties of the block.

The effectiveness of the method is illustrated in the table, which shows the results of the application of the method on loams and clays of the Rodionovskoye field. Layered organization of the block structure allows you to combine load-bearing and heat-shielding properties in the product through the use of various speed and limit modes. In addition to the raw materials of the Rodionovsky deposit, similar results were obtained on loams of the Mikhailovskaya suite (Tomsk) and clays of the Zyryansk brick factory (Tomsk region).

Column 4 shows the parameters of the heat treatment modes. An increase in the heating rate above 1450 ° C / min with a simultaneous increase in temperature is accompanied by an increase in the density of the material, a decrease in the heat-insulating properties of the unit, and increased wear of the equipment. Lower limits of the heating rate range are achieved if it is necessary to obtain a layer close in structure to the monolith, or when using specific loam. In this case, although the process time increases, the total energy consumption is reduced by 2-3 times while reducing the requirements for thermal stability of the equipment.

The results of applying the method on loams of the Rodionovskoye field

Table

As a result of applying the method, a porous glass-ceramic block with a thickness of 108 mm was obtained, which corresponds to the thickness of a standard "double" building stone with a thermal conductivity of 0.14 W / (m · K). The unit can withstand a load of up to 2.5 MPa with transverse compression and up to 7.7 MPa with longitudinal compression.

Literature

1. USSR author's certificate No. 1158511, MKI S 03 S 11/00, 1985.

2. RF patent No. 1787965, MKI C 03 C 11/00. Publ. 01/15/93, BI No. 2, 1993.

3. Copyright certificate of the USSR No. 753795, publ. 08/07/1980 (prototype).

Claims (2)

1. A method of obtaining a multilayer porous glass-ceramic block, comprising forming a charge layer of a given thickness and foaming it by heating, forming a subsequent layer at the stage of a viscous glass phase in the previous layer, stabilizing and cooling the foamed mass in a given mode, characterized in that for at least one loam and / or clay are used as a charge for the layer, the layers are formed outside the heating zone, and the layer heating rate is selected in the range 415 - 1450 ° C / min, providing it with a temperature choice and time setting no heating. 2. The method according to claim 1, characterized in that before the formation of the next layer on the surface of the previous layer, grooves with a depth of 0.1-1.0 thickness are made corresponding to the directions of the future division of the block into parts, and fill them with the original charge, or refractory bulk material.