RU2041744C1 - Method and device for applying two-layer coatings to cylindric articles - Google Patents

Abstract

FIELD: coating articles. SUBSTANCE: article is heated before coating up to 100-200°C and is then sprayed with metal and polymer, walls of supersonic nozzle being cooled. The device is provided with chamber for heating the article, nozzle unit mounted for permitting rotation, multi-channel supersonic nozzle, spraying chamber, and rotor batcher consisting of feeder and receiving tank mounted at the outlet of the feeder interconnected through a pipe line. The spraying chamber is rigidly secured to the nozzle and constructed as a metallic box provided with a curved port arranged perpendicular to the nozzle axis. The rotor is mounted at the inlet of the receiving tank. The rotor has cellular surface. The receiving tank is provided with hollow cylinder mounted inside the tank for permitting rotation, staggeringly mounted ladle scoops, and chute whose top part is a conical cap. EFFECT: simplified method and improved design. 3 cl, 4 dwg

Description

 The invention relates to coating in a high-speed way and can be used in pipe engineering and mechanical engineering to create protective anti-corrosion wear-resistant coatings on the outer surface of the product.

 A known method of cold welding of metal, which consists in the fact that one of the metals being welded in the form of a powder is supplied from a metal-jet gun using an inert gas, while the particle velocity reaches speeds of several hundred meters ("bullet flight speed").

 Known methods of thermal spray coating, the essence of which is the impact on the sprayed polymer material of high temperature and kinetic energy of the gas stream. When heated, the sprayed polymer powder melts, and the gas stream sprays it and directs it to the substrate at a certain speed.

 There is also a known method of producing a coating that is closest to the one proposed, which consists in accelerating particles of metal powder with a size of 1-200 μm to 650-1200 m / s and applying the powder to the product with a heated gas stream. However, such wide ranges of parameters of spraying conditions make it difficult to use the invention in specific industrial conditions.

 The disadvantages of this method are: increased requirements for the dispersion of the polymer powder, since the fine fraction burns out, and the coarse is only melted: the difficulty of obtaining a high-quality coating resulting from the physics of the process of a variable particle is in a high-gradient temperature stream.

 A device for coating using a high-speed particle stream, a drum type dispenser, gas heating, a supersonic rectangular nozzle is known.

 The main disadvantages of this device are the short duration of work due to the adherence of particles to the nozzle walls, the absence of a spraying chamber for selecting unreacted powder, and the absence of flexible connecting elements.

 Closest to the invention is a metallization line for cylindrical products, comprising sequentially installed loading, cleaning, metallizing and unloading devices, live rolls located in the loading and unloading zones, a working rotation speed task mechanism and a drive roller pressing mechanism to the product.

 The disadvantage is the uneven rotation of the product due to runout, this affects the coating process.

 The aim of the invention is to improve the quality of the coating, saving material, increasing productivity.

This is achieved in that the method of applying the two-layer coatings on cylindrical articles by spraying a high-speed powder, comprising feeding powder into the supersonic flow of preheated to 200-220 ^{° C} working gas, characterized in that the product before the coating is heated to 100-200 ^{° C,} then metal and polymer coatings are successively applied to its surface, while the walls of the supersonic nozzles are cooled. Heating the product is necessary to increase the adhesive properties of the coating and increase the coefficient of deposition of the powder. The temperature of the heating depends on the type of sprayed material and is selected empirically. The polymer coating is applied immediately after obtaining a metallized coating, which eliminates the need to clean the surface of the product before polymerization and its heating, which improves productivity. Particles of polymer as an insulating material fill the pores of the metal coating and protect the product from chemical and electrochemical corrosion. The nozzle walls are cooled in order to exclude the sticking of powder particles on the nozzle walls, and therefore increase the overhaul life.

 To implement the proposed method, a line was used that consistently installed devices for loading, cleaning the product, metallization, consisting of a nozzle assembly, in which an electric heater, a prechamber and a supersonic nozzle, a spraying chamber and a batcher, unloading, live rolls, a working rotation speed task mechanism, and a mechanism were installed pressing the derivative rollers to the product, a heating chamber is located at the output of the product cleaning device, in series with the metallization device similar polymerization device. The nozzle assembly of each device is pivotally mounted with the possibility of rotation, the supersonic nozzle is made in the form of a multi-channel block of Laval nozzles with a rectangular section. The channels are formed by side plates and internal profiled inserts, the axis of symmetry of which intersect behind the nozzle exit section at an acute angle. The walls of the nozzle have cavities for cooling. The nozzle is rigidly connected to the spraying chamber, which is a closed metal box having a curvilinear window located perpendicular to the axis of the nozzle. The dispenser consists of a feeder and a receiving tank installed at its outlet, interconnected by a gas pipeline, a rotor is installed at the inlet of the receiving tank, which has cylindrical recesses on the cell surface, a hollow cylinder is mounted inside the receiving tank, mounted on the motor shaft, on the inner wall of which screw captures are attached. Next, scoops are installed, made in the form of buckets and arranged in a checkerboard pattern, and a chute, the upper part of which is made in the form of a cone-shaped bowl.

 The nozzle assembly is rotatable to provide removal of the spraying chamber in order to prevent breakage when loading the product and replacing the nozzle, which takes less time compared to a horizontal moving device of a similar purpose.

 The window of the curved shape of the spraying chamber allows to increase the utilization rate of the sprayed powder, due to the large radius of curvature, the spraying chamber can be used for products with a wide range of diameters. This design allows the use of a small volume spraying chamber and provides local suction of unused particles, which reduces the risk of explosion during operation.

 The rectangular cross-sectional shape of the supersonic nozzle channel is dictated by considerations of ease of manufacture. Such a nozzle consists of 2 side profiled walls and lower and upper plates connected by bolts. The length and width of the channel is selected from those considerations in order to ensure a sufficient distance of the acceleration section for particles and to guarantee non-closure of the boundary layers on the nozzle walls. The presence of profiled inserts, located at an angle to the axis of the nozzle, provides the necessary section for the acceleration of particles and a sufficient uniformity of their distribution over the nozzle section. Using a multi-channel block allows you to increase the width of the sprayed area.

 Cavities in the walls of the nozzle are provided for cooling it. The nozzle is collapsible, which reduces the operating costs of the nozzle assembly. The use of a rotary dispenser makes it possible to achieve a uniform supply of powder into the prechamber, eliminating the possibility of clumping of powder, mashing of the powder and jamming of the rotating parts of the device, in contrast to the known drum dispensers.

The calculation of the flow rate of powder from the feeder to the prechamber is carried out according to the formula
q K π˙ d ² ˙hmrn γ / 4, where K is the coefficient of cell filling with powder;
d, h cell diameter and height, respectively;
m is the number of cells in one row;
r number of rows on the rotor;
γ powder density;
n rotor speed;
π 3.14
The dimensions of the dispenser, the number of revolutions of the rotating drums are selected based on the provision of powder during spraying.

PRI me R. For spraying a pipe with a diameter equal to 219 mm, at a flow rate of 5-7 g / s of aluminum powder, the cell sizes, rotor and its rotation speed are: rotor diameter 50 mm; rotor length 70 mm; K08; d 5 mm; h 5 mm, m 12, r 24, γ 1.3 g / cm ³ , n 0.2 rpm.

 In FIG. 1 shows a general diagram of a device for applying two-layer coatings on cylindrical products; in FIG. 2 nozzle; in FIG. 3 dispenser; in FIG. 4 nozzle assembly.

 The proposed device contains a product 1, a chamber 2 for rust cleaning, an acupuncture 3, recuperators 4, 19, 29, fans 5, 20, 30; a heating chamber 6 with a fire heater, a diffusion heater and an extractor, a compressor 7, a receiver 8, an oil separator 9, a distributor of working gas 10, pressure reducers 11.21, flexible pipelines 11.22, electric heaters 13, 23, dispensers 14, 24, feeders 15 , 25, pre-chambers 16, 26, nozzles 17, 27, spraying chambers 18, 28, tank 31, pipeline 32, water pump 33, gas pipelines 34, 35, 36, 37. The nozzle device contains a nozzle cavity 38, channels 39, side walls 40, profiled inserts 41, cavity 42 of the acceleration section, fitting 43, cavity 44 for cooling, fitting 45.

 The dispenser device comprises a feeder 15, a cover 46, a stop screw 47, a rotor 48, a cell 49, a receiving tank 50, a hollow cylinder 51, screw captures 52, scoops 53, a cone-shaped bowl 54, a groove 55, a choke 56, a level sensor 57.

 The nozzle assembly comprises a curved-shaped window 58, a flexible conduit 59, and a hinge 60.

 The device operates as follows. The product 1 moves along the roller tables, enters the cleaning chamber 2, where it is cleaned of rust and scale with a needle mill 3, the cleaning products are removed using a recuperator 4 and fan 5. Then the product enters the heating chamber 6, which is equipped with a diffusion burner and exhaust, where it is heated and further enters the spraying chamber 18.

 The working gas (compressed air) from the compressor 7 enters through the receiver 8 and the oil separator 9 into the distributor 10 of the working gas, from where it is supplied through the reducer 11 and the flexible hose 12 to the electric heater 13. Then, the heated working gas enters the dispenser 14, which is simultaneously supplied from the feeder 15 metal powder is fed, which is pre-dried before loading into the feeder. In the prechamber 16, the powder is mixed with the heated working gas, and the resulting mixture is fed through the multichannel supersonic nozzle 17 into the spraying chamber 18 and onto the surface of the product.

 Unused metal powder residues are collected from the spraying chamber 18 through flexible pipelines 59 using a recuperator 19 and a fan 20. Next, the metallized product 1 enters the polymerization section, where a similarly compressed working gas from the distributor 10 through the reducer 21 enters through the flexible hose 22 into the electric heater 23, it is heated and fed into the dispenser 24, into which polymer powder enters from the feeder 25. In the prechamber 26, they are mixed, and the resulting mixture is fed through the multichannel supersonic nozzle to the spraying chamber 28 and applied to the metallized surface of the product. Unused polymer powder is captured from the spraying chamber 18 and 28 (Fig. 1) through flexible pipelines 59 (Fig. 4) using a recuperator 29 and a fan 30. Nozzles 17 and 27 are cooled using a single hydraulic device consisting of a tank 31, a pipe 32 and a water pump 33.

 The nozzle operates as follows.

 The mixture of compressed working gas with particles of the sprayed material from the pre-chamber 16, 26 (Fig. 1) enters the nozzle cavity 38 (Fig. 2), from where it passes through the channels 39 formed by the side walls 40 and shaped inserts 41 into the cavity 42, where the flows are closed ( in this case, three) are blown onto the surface of the product. The nozzle walls are cooled by a circulating liquid, which is pumped by the pump 33 from the tank 31 through the pipe 32 (Fig. 1) through the nozzle 43 into the cavity 44 and back through the nozzle 45 (Fig. 2) into the tank 31 (Fig. 1).

 Rotary dispenser operates as follows.

 The powder is poured into the feeder 15 (Fig. 3), which is sealed by a cap 46 and a stop screw 47. The powder is supplied from the feeder 15 to the receiving tank 50 by rotating the rotor 48, on the surface of which there are cells 49, due to which the powder is captured and transferred to the receiving tank 50. The rotor is rotated by an electric motor. Screw captures 52, mounted on the inner wall of the hollow rotating cylinder 51 installed in the receiving tank 50, transfer the powder into the cylinder, from where it scoops up and falls out into the cone-shaped bowl 54, from which it enters the choke 56 and then into the prechamber through the chute 55.

 To equalize the pressure in the feeder 15 and the receiving tank 50, compressed working gas is supplied to their cavity through gas pipelines 34 and 35, 36 and 37 connected to a flexible pipe 12, 22 (Fig. 1).

 The dispenser can be operated while rotating the rotor 49 and cylinder 51, having previously agreed on the expense of the powder due to their rotation speed, or by periodically turning the rotor 49 on by the signal from the level sensor 57. When loading products or replacing the nozzle, the nozzle assembly is rotated using hinge 60.

 In specific conditions, for spraying a two-layer coating, a device was used containing known loading, unloading devices, live rolls located in loading and unloading zones, a mechanism for the task of working rotation speed and a mechanism for pressing drive rollers to the product, a known device for cleaning products by needle milling.

 The heating of the pipe in the heating chamber was carried out using a burner device based on the diffusion principle of combustion, with worked out heating modes. Diffusion combustion compared to homogeneous is safer and allows you to have a shortened torch.

 Acetylene, propane-butane, hydrogen, natural gas, etc. can be used as combustible gas. Preliminary drying of the metal powder was carried out using standard dryers. The suction of the used powder was carried out by standard recuperators and fans.

 In metallization and polymerization devices for heating compressed air, electric heaters were used with blowing heating elements with compressed air, powered by a direct current source, connected directly to the prechamber, which makes it possible to eliminate a section with a flexible gas pipeline operating at high temperatures, which makes installation more expensive and does not provide greater durability in operation, at the same time makes it possible to use rubber hoses in the moving part in front of electric heaters high pressure, operating at ambient temperature.

For high-speed sputtering was used supersonic nozzle having three channels, formed by two profiled inserts, the axis of symmetry of channels intersect at an angle of ^about 2-7. The inclination of the axes of the nozzle channels in this case contributes to uniform coverage over the entire area of the nozzle section and significantly increases the coefficient of powder utilization. The three-channel nozzle made it possible to obtain a width of the sprayed cavity of 36 mm. The parameters of the obtained two-layer coating: the thickness of the aluminum coating is 150-200 microns, the polymer 100-150 microns, the adhesion of the aluminum coating is 0.5-0.6 MPa, the polymer is 0.3-0.4 MPa.

Claims (2)

1. The method of applying two-layer coatings on cylindrical products, comprising feeding the powder into a supersonic stream of a heated working gas and applying it to the surface of the product, characterized in that the product is heated to 100 200 ^o C before applying the powder, metal powder and powder are successively fed into the supersonic stream polymer, and the walls of the supersonic nozzles are cooled.  2. A device for applying two-layer coatings on cylindrical products containing a sequentially installed loading mechanism, a product cleaning chamber, a metallization mechanism containing a nozzle assembly with a working gas electric heater, a prechamber, a supersonic nozzle, a spraying chamber and a batcher, an unloading mechanism, live rolls, a mechanism tasks of the working speed of rotation and the mechanism of pressing the drive rollers to the product, characterized in that it further comprises a heating chamber, installed after the cleaning chamber, and the polymerization mechanism installed after the metallization mechanism, the nozzle units of the metallization and polymerization mechanisms are pivotally mounted on hinged bases, the supersonic nozzle is made in the form of a multi-channel block of Laval nozzles with a rectangular cross-section with walls having cavities, and is rigidly connected to spraying chamber, channel channels are formed by side plates and internal profiled inserts with axes of symmetry intersecting behind the exit section of the nozzles, the chamber is sprayed It is made in the form of a metal box with a curvilinear window located perpendicular to the longitudinal axis of the nozzles, the dispenser contains a feeder and a receiving tank installed at the output of the feeder and connected to it by a gas pipe, and a rotor is installed at the output of the receiving tank having cylindrical recesses on the cell surface , the receiving tank contains a hollow cylinder mounted on the shaft of the electric motor, and the trough with the upper part, made in the form of a cone-shaped bowl, the hollow cylinder has screw captures attached to its inside renney wall and screw cherpalki made in the form of buckets and installed in a staggered manner.

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