RU2742295C1 - Manufacturing method of radiotransparent article - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to aircraft and rocket equipment and can be used in production of high-speed rocket aerodynamic fairings. Technical result is achieved by the fact that in the method of making a radiotransparent article, comprising forming a ceramic shell, drying, calcining, machining with a diamond tool, volumetric impregnation of the coating with the organosilicon polymer, followed by polymerisation, radio adjustment of shell by mechanical treatment of its outer surface to preset dimensions, connection of shell with frame by means of sealant, in contrast to the prototype after polymerisation, an organosilicon polymer is applied on the inner surface of the shell by flooding for 30–60 s and polymerised.

EFFECT: technical result is creation of sealed shell, providing radio technical characteristics of item at required level.

1 cl, 1 tbl

Description

The invention relates to the field of aviation and rocket technology and can mainly be used in the manufacture of antenna radomes for high-speed missiles.

Known rocket antenna radome (RF patent No. 2256262, IPC Н01Q 1/42, 10.07.2005), the manufacturing technology of which is
in the manufacture of a ceramic shell by water slip casting
into plaster molds followed by drying and firing, mechanical processing of the shell on a screw-cutting lathe with a diamond tool to a given wall thickness and product profile, depending on the dielectric constant of the material in the shell, impregnation of the inner and outer surfaces of the shell with acetone solution of the oligomer MFSS-8 with a density of 0.950 -0.960 g / cm3 at a depth of 1.0-2.0 mm
with subsequent polymerization at a temperature of 325 ° С, assembly of the shell
with an Invar frame through a layer of sealant.

The disadvantages of the technology for producing the product described in this source include the fact that impregnation to a depth of 1-2 mm with the oligomer MFSS-8 and the polymerization of the inner and outer surfaces are carried out on a completely mechanically processed shell with the necessary radio technical characteristics (RTX). After impregnation of the inner and outer surfaces, the dielectric constant of the shell material changes and, as a result, the PTX of the shell changes. Variations in the structural factors of the material along the thickness and height of the shell, as well as from shell to shell, do not provide the desired depth of impregnation. All this leads to the need to additionally carry out mechanical processing of the impregnated shells, which leads to the removal of the impregnated ceramic layer and, as a consequence, the product leaks.

The closest technical solution is the method described
in RF patent No. 2474013 IPC H01Q 1/42, published on 01/27/2013, in the manufacture of an antenna radome. Manufacturing technology consists
in the manufacture of a ceramic porous shell by methods of ceramic production, mechanical processing of a fired workpiece with a diamond tool to a given wall thickness and shell profile, bulk impregnation of the shell with a polymer, for example, methylphenylspirosiloxane (MFSS-8 product), followed by polymerization, radio-thinning of the shell by mechanical processing with a diamond tool to a given wall thickness and profile, depending on the radio technical characteristics of a particular shell in the entire operating frequency range, gluing the shell with the frame using a sealant.

The disadvantages of the technology for producing the article described in the known design include the fact that the volumetric impregnation of the shell with the organopolymer does not lead to the complete closure of the pores, which allows air to penetrate through them, that is, the tightness of the shell is not ensured. Most rocket antenna radomes have strict requirements for the tightness of products, since the radome must protect the antenna from the aerodynamic air pressure.

To ensure the tightness of the shell, it is necessary to create a continuous film of silicone polymer on the inner surface of the shell.

The objective of the present invention is to provide a sealed shell that provides the PTX of the product at the required level.

The problem is solved by the fact that a method for manufacturing a radio-transparent product is proposed, including the formation of a ceramic shell, drying, firing, mechanical processing with a diamond tool, volumetric impregnation of the shell with an organosilicon polymer
followed by polymerization, radio-shaping of the shell by mechanical treatment of its outer surface to specified dimensions, joining the shell with the frame using a sealant, characterized in that after polymerization, a silicone polymer is applied to the inner surface of the shell by pouring for 30-60 s and polymerized.

The authors found that the deposition of an organosilicon polymer on the inner surface of a volumetric impregnated shell ensures stable formation of a continuous film, which ensures the tightness of the shell and the product as a whole. Such a technology for obtaining a product makes it possible to obtain products with the necessary RTX, since the determination of the properties of the shell for the subsequent issuance of a task for machining to achieve the required RTX is performed on the shell with an already applied polymer layer.

The manufacturing technology of radio-transparent products according to the proposed technical solution includes the following operations:

- production of a ceramic porous shell by methods of ceramic production, consisting of molding a ceramic blank by slip casting from an aqueous suspension of quartz glass in a plaster mold, drying, firing;

- mechanical processing with a diamond tool of the inner surface of the fired workpiece to a given profile and the outer surface with a technological allowance;

- bulk impregnation of the shell with a polymer, for example, methylphenylspirosiloxane (product MFSS-8) for 4-6 hours,
followed by polymerization at a temperature of 275 ± 25 ° С;

- applying a polymer to the inner surface of the organosilicon polymer by pouring the inner surface for
30-60 s, followed by polymerization at a temperature of 275 ± 25 ° C;

- radio conduction of the shell by mechanical treatment of its outer surface with a diamond tool to a given wall thickness and profile, depending on the radio technical characteristics of a particular shell in the entire operating frequency range;

- connection of the shell with the frame using a sealant.

An example of the method.

Ceramic blanks obtained from broken quartz glass
made of quartz tube with SiO ₂ content not less than 99.8%, molded
in gypsum molds by the bulk method of water slip casting by pouring slip into the cavity between the gypsum matrix and the passive core, followed by holding until a complete set of the workpiece. The dried shells were fired in TSB 71 type rotary hearth furnaces and in furnaces with wire heaters N1650 / H, N1500 / H manufactured by Nabertherm according to temperature and time regimes, ensuring the production of material with a porosity of 8-11%, bending strength of at least 35 MPa ... Mechanical processing of the inner surface of the fired shell was carried out on screw-cutting lathes with copying devices, or on special machines with numerical control (CNC) with a diamond tool to a given profile, and mechanical processing of the outer surface with a technological allowance of about 1 mm.

After mechanical treatment, bulk impregnation of the shell was carried out with a solution of organosilicon polymer, for example, methylphenylsprosiloxane in acetone (MFSS-8 TU 6-02-1352-87 or TU 2229-001-64570284-2011). The operation was carried out using preliminary evacuation of the casing for 30-40 minutes and subsequent impregnation for 4-6 hours. Then the casing was dried and heat-treated according to the MFS-8 polymerization mode at a temperature of 275 ± 25 ° C with a holding time of 4-6 hours.

After volumetric impregnation, an organosilicon polymer was applied to the inner surface of the shell by pouring for 30-60 s,
followed by polymerization at a temperature of 275 ± 25 ° C.

After that, the radio conduction of the shell was carried out by mechanical processing with a diamond tool to a given wall thickness and the profile of the outer surface, depending on the radio technical characteristics of a particular shell in the entire operating frequency range.

The assembly of the shell with the Invar frame was carried out according to the known technology by gluing the frame to the landing zone of the shell
with the help of Viksint U-2-28 sealant.

The authors found that the deposition of an organosilicon polymer by pouring for less than 30 s does not allow obtaining a continuous film, and for more than 60 s leads to the formation of polymer beads, which further deteriorates the quality of the radio finishing of the shell.

The method of manufacturing a radio-transparent product makes it possible to obtain sealed products by obtaining a continuous film
made of silicone polymer on the inner surface.

The table shows comparative data for the prototype and the proposed technical solution.

Table

Method for obtaining a radio-transparent product Number of manufactured products Percentage of products that meet the requirements for tightness Prototype 15 pcs. 60% Proposed technical solution 15 pcs. one hundred %

The invention improves the yield of suitable products in accordance
with the requirement for tightness and the required PTX level.

Claims (1)

A method of manufacturing a radio-transparent product, including molding a ceramic shell, drying, firing, mechanical processing with a diamond tool, volumetric impregnation of the shell with an organosilicon polymer followed by polymerization, radio-thinning of the shell by machining its outer surface to specified dimensions, joining the shell with the frame using a sealant, characterized by that after polymerization
an organosilicon polymer is applied to the inner surface of the shell by pouring for 30-60 s and polymerized.