RU2174894C2 - Method of manufacturing porous structures - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: invention relates to methods for manufacturing devices for purification of melts of metals and other liquid and gaseous media, in particular for manufacturing porous filter elements. Method involves manufacturing framework from high-porous material, applying on it ceramic pasty suspension containing solid binder phase, introducing suspension into framework, and drying followed by sintering of blank. According to invention, high-porous material utilized for manufacturing framework is foam-rubber with mutually communicating channels and above-mentioned solid phase is constituted by pasty suspension wherein filler is metallurgical waste (slags and other ceramic materials). Pasty suspension is introduced into framework through volume impregnation technique utilizing forming roll and ensuring uniform distribution of ceramic suspension all over the filter volume, whereas final formation of porous structure is achieved when framework is burned down during sintering operation. EFFECT: enabled manufacture of volumetric filters, reduced cost of porous structures, and expanded possibilities thereof, in particular for filtration of melts at el4evated temperatures. 2 ex _

Description

 The invention relates to methods for manufacturing devices for cleaning molten metals and other liquid and gaseous media, namely, to obtain porous filter elements that are used or can be used in the metallurgical industry and in other sectors of the economy, where metal melts, as well as liquid and gaseous media have special purity requirements.

 A known method for producing composite filter elements, including the manufacture of a support frame of highly porous permeable cellular material (VPYAM), the creation of a layer of uniformly sprinkled fine bronze powder of a given thickness, laying on it a support frame and liquid-phase sintering of the support and filter layers under a load of 200-400 Pa. The supporting frame has a porosity of about 90%, the cell size of the HPLM (0.8 ± 0.1) mm. The average pore size of the filter layer can vary from 15 to 100 microns. Porosity from 40 to 50% (see USSR author's certificate N 500900, B 22 F 3/11, 1976).

 The disadvantage of this method is the inability to obtain filters of complex convex-concave configuration. The baking of a free-flowing powder to the mesh-like material does not provide high strength of the connection between the support and filter layers when using powders in which there are no liquid-phase sintering processes (for example, copper, nickel, stainless steel), which reduces the service life of such filters. In addition, bronze-based powders are expensive.

 A known method of producing filter elements, including the manufacture of a frame of highly porous material, applying a filter layer of powder to its surface and sintering the workpiece. The frame is made of highly porous cellular material, and a paste-like slip with a solids content of 33-50 vol.% Is preliminarily prepared from the powder and, after application, the slip is introduced into the support frame to a depth of 0.3-2.5 mm and dried in air. In the manufacture of filter elements with through holes of constant cross-section, the introduction of the slip into the support frame is carried out on the inner surface of the holes when moving the conical piston along the axis of the hole with a gap of 0.1-2.0 mm between the surfaces of the piston and the hole. (RU 2075370 C1, 20.03.1997, B 22 F 3/11).

 The disadvantages of this method are: the inability to obtain a volumetric filter, that is, the full introduction of the slip into a given volume of HPLM, the consequence of this is the uneconomical consumption of the support frame; the increased complexity of manufacturing the supporting frame of the desired configuration, in some cases, its manufacture includes the same operations as the manufacture of the filter — coating with subsequent sintering, which is very inconvenient; the impossibility of varying the size of the filtering pores by the thickness of the filter elements; the need to create a special environment for sintering the filter; finally, a support frame made of materials based on copper, nickel and steels of the type X18H9 has a high cost.

 These shortcomings are eliminated by the proposed solution.

 The problem to be solved is the improvement of the methods for manufacturing porous structures.

 EFFECT: obtaining volumetric filters, reducing the cost of porous structures through the use of waste products, expanding the technological capabilities of the resulting porous structures by using them to filter various media, in particular melts, at elevated temperatures.

 This technical result is achieved in that in a method for producing porous structures, including the manufacture of a framework of highly porous material, applying a ceramic paste-like suspension of a solid phase and a binder, introducing it into the framework, drying and subsequent sintering of the workpiece, as a highly porous material for the manufacture of the frame use foam rubber with interconnecting channels of variable cross section, as a solid phase - a paste-like suspension, in which the filler is metallurgical waste Slag or other ceramic materials, the introduction of a paste-like suspension into the frame is carried out by volumetric impregnation using a rolling roll, ensuring a uniform distribution of the ceramic suspension throughout the filter volume, and the final formation of the porous structure is achieved when the frame burns out during sintering.

 The use of a paste-like suspension makes it easy to apply it to the surface of the frame of any shape, with open pores of the widest range of sizes, followed by volumetric impregnation under the mechanical influence of the roll. Sintering of the material provides high filter strength, as well as complete burnout of the frame.

 The proposed method for obtaining porous structures is as follows.

A frame of the necessary configuration and size is made of foam rubber. A ceramic suspension is prepared on the basis of slag and liquid glass, the percentage ratio of the components lies in a wide range: slag - 60-80%, liquid glass - 40-20% - by volume. In some cases, clay is added as a binder together with liquid glass in an amount of 10-20% in excess of 100% by volume. Clay is used in the manufacture of filters with a significant height, 1.5-2 times greater than the length or width of the filter element, and in the case of a cylindrical shape of the filter element, respectively 1.5-2 times larger than its diameter. The finished suspension is applied to the frame and rolled with a roll, achieving uniform distribution of the working composition throughout the filter. Next, drying is carried out in air, after which sintering of the product is carried out at a temperature of 950-1020 ^o C.

A hydrolyzed solution of ethyl silicate is also used as a ceramic suspension, and marshalite is used as a filler. This coating allows filtering at a temperature of 900 ^o C, and using other refractory fillers at higher temperatures.

 By varying the compositions and the percentage of suspension components, as well as using foam rubber with different pore sizes, it is possible to change the porosity of the material from 60-85%, the average pore diameter from 1 to 4 mm.

 EXAMPLE 1

Elastic polyurethane foam was made of foam rubber of the PPU-EF type (see G. Bulatov, “The Use of Foam Plastics in the National Economy,” “Foam and Foam Plastics in the National Economy.” M.: Knowledge, 1978), a filter frame was made with dimensions: length 60 mm, 40 mm wide and 25 mm thick. A suspension was prepared by mixing ground cupola slag with clay, and liquid glass with a specific gravity of 1.45 g / cm ^{3 was} used as a binder. The percentage of components: slag - 90%, clay - 10%, water glass - 40% in excess of 100% of the total. The finished suspension was applied to the surface of the foam rubber and rolled by rolling, crushing the foam rubber for volumetric impregnation. The workpiece was dried in air at room temperature. Sintering was carried out at 1020 ^o C. To a temperature of 1020 ^o C - smooth heating for 2 hours. Then holding for 2 minutes at a temperature of 1020 ^o C and cooling.

The resulting filter element had a porosity of 83% with an average pore diameter of 2.5-3 mm. Through this filter, the AK9Ch aluminum alloy was filtered in an amount of 6 kg at a temperature of 730 ± 10 ^o C. The filter did not show any noticeable resistance to metal flow during pouring, and also withstood the pressure of liquid metal. The height of the metallostatic head is H = 300 mm.

 EXAMPLE 2

The frame is made of the same material - PPU-EF. The shape of the filter is a cube with an edge of 40 mm. A hydrolyzed solution of ethyl silicate was used as a suspension, and the filling mass was marshalite. The suspension was applied by dipping the framework into the working solution. The workpiece was dried in air at room temperature for 3 hours. Sintering was carried out at a temperature of 1000 ^o C.

The resulting filter element had a porosity of 80%, with an average pore diameter of 1.5-2 mm. Through this filter, the AK9Ch aluminum alloy was filtered in an amount of 6 kg at a temperature of 730 ± 10 ^o C. The filter did not show any noticeable resistance to metal flow during pouring, and also withstood the pressure of liquid metal. The height of the metallostatic head is H = 125 mm.

 The tests showed the following.

The proposed method of obtaining filter elements allows you to get volumetric filters from waste from various industries, especially waste from metallurgical and chemical industries. Good slag agglomeration increases the strength of filter elements, expands the technological capabilities of the production of these filters. Low gas content and thermal stability of the material allows them to be used for filtering metal melts, as well as liquid and gaseous media at high temperatures of 900 ^o C and above. The low cost of raw materials and the simplicity of the technology allows to establish the production of filter elements on the basis of consumer enterprises, which is very important in the current financial and economic situation in Russia, as well as partially solve the problem of waste disposal of various industries.

Claims (1)

 A method of manufacturing porous structures, including the manufacture of a skeleton of a highly porous material, applying a ceramic paste-like suspension consisting of a solid phase of a binder, introducing it into the skeleton, drying and subsequent sintering of the preform, characterized in that foam rubber is used as a highly porous material for manufacturing the skeleton interconnected channels, as a solid phase - a pasty suspension in which the filler is metallurgical waste - slags and other ceramic materials, the introduction of a paste-like suspension into the frame is carried out by volumetric impregnation using a rolling roll, ensuring uniform distribution of the ceramic suspension throughout the filter, and the final formation of the porous structure is achieved when the frame burns out during sintering.