RU2505622C2 - Device for gas-dynamic application of coatings onto external cylindrical surfaces of products - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: device includes a batcher, a supply system of working gas and powder to antechamber (1), a spraying assembly and a longitudinal product movement device. The spraying assembly is made in the form of N_s>1 multichannel circular sections installed along the axis of the sprayed-film product at some distance from each other and fixed relative to each other to the specified angle. Channels formed with flat replaceable inserts (4) are located uniformly along the perimetre of the circular section and form flat supersonic nozzles with the size of the channel in critical section h_cr. and opening angle α_n, which provide an impingement angle of sprayed particles with the product surface of 60-90° and Mach number at the nozzle section M_ex=1-3. Length and width of the supersonic part of the channels provides optimum acceleration of sputtered particles. Selection of the number of channels provides optimum shutoff of supersonic jets immediately at the sprayed-film surface.

EFFECT: enlarging technological and functional capabilities of an application process of coatings onto external cylindrical surfaces of products of different sizes an improving quality of coatings.

2 dwg

Description

The invention relates to equipment for coating by the method of cold gas-dynamic spraying on the outer cylindrical surface of products and can be used in mechanical engineering, aerospace engineering, in the automotive industry, energy, construction, oil and gas industry and other fields of economy.

Known equipment for applying anti-corrosion coatings on the outer surface of long pipes with cold gas-dynamic spraying (Alkhimov A.P., Klinkov S.V., Kosarev V.F., Fomin V.M. Cold gas-dynamic spraying. Theory and Practice / Ed. Ed. V.M. Fomina. - M.: Fizmatlit, 2010.S. 339-341). The installation works as follows - a rotational and simultaneous translational motion is communicated to the pipe and it is fed sequentially through the cleaning and spraying chambers. In the cleaning chamber, the surface of the pipe is cleaned with needle cutters. After the cleaning chamber, the pipe enters the spraying chamber, where by this time the spraying parameters are set (pressure p ₀ and gas deceleration temperature T ₀ ). When the pipe approaches the nozzle assembly, the dispenser drive is switched on and the process of spraying onto the pipe surface occurs. When passing the end of the pipe under the nozzle assembly, the metering drive is turned off. Powder particles not sprayed onto the surface of the pipe are disposed of by a dust suction unit and then returned to the hopper of the dispenser.

The disadvantage of this device is that to obtain a continuous coating layer on the surface of the pipe, it must be rotated. In this case, a spiral-shaped spraying path is obtained, and in order to obtain a continuous coating, overlapping of the spraying paths is necessary. This leads to the fact that it is difficult to obtain a uniform coating thickness along the axis of the pipe.

A device for coating the low-temperature gas-dynamic method (RF patent No. 2193454, publ. 11/27/2002; RF patent No. 2222640, publ. 01/27/2004), which contains a hopper for loading the powder mixture with a metering feeder, a mixing chamber, a working feed system gas into the mixing chamber and a feeder-dispenser, a spray head, in the housing of which there is a collector with an annular supersonic nozzle. At the same time, a rotary device is located in the housing of the spray head, which ensures rotation of the flow at an angle of 90 ° towards the longitudinal axis of symmetry of the head, and in patent No. 2222640 by 90 ± 5 °. The rotary device is communicated and associated with the output of a supersonic annular nozzle. It has the shape of a ring and is made axisymmetric with respect to the central longitudinal axis of the head.

The disadvantage of this device is that the sprayed particles acquire the necessary speed and temperature in the annular supersonic nozzle, and then in the annular rotary device rotate 90 ± 5 °. In this case, the particles inevitably collide with the surface of the rotary device, which leads to a loss of their speed. In addition, the surface of the rotary device in the area of collision with particles will wear out erosively and, accordingly, the shape of the channel will change, which will lead to a change in the flow parameters and, as a consequence, the spraying conditions. The reverse erosion process can also lead to the same consequences - deposition of sprayed particles on the surface of a rotary device.

Closest to the proposed device is a coating device containing a hopper for a powder mixture with a metering feeder, a mixing chamber, a spray head associated with the mixing chamber, and a system for supplying working gas to the spray head, equipped with a gas supply system to the metering feeder, which made in the form of a supersonic ejector-feeder, and its spray head is made in the form of an annular collector with an annular supersonic nozzle (RF patent No. 2089665, publ. 09/10/1997).

A mixture of gas and powder is formed in the pneumatic systems of the device and with the necessary thermodynamic parameters enters the annular manifold of the saw head. The two-phase mixture, entering the annular collector, is accelerated along the profile of the annular nozzle, and the particles, having acquired a design speed at the section of the annular nozzle, reach the rolled surface and form a coating. The estimated particle velocity at the nozzle exit and their concentration in the two-phase flow is calculated based on the rolling speed, the area of the side surface of the product and the required coating thickness.

The formation of a supersonic two-phase jet and its parameters is achieved in a supersonic annular nozzle of the spray head. The mass flow rate of the powder consumed uniquely determines the mass flow rate of the working gas. The temperature of the two-phase gas, which determines the speed of the working gas and particles at the nozzle exit, is set by the kind of coating and much lower than the melting temperature of the particle material is chosen. The mass flow rate of the powder passing through the sonic feeder-ejector is determined by the parameters of the compressed gas at the inlet to the feeder-ejector, which is continuously regulated by the gas supply system. The two-phase mixture formed in the feeder-ejector enters the mixing chamber for mixing with the working gas (carrier gas) and further transportation to the annular collector.

The proposed device creates a two-phase gas mixture (particles + carrier gas) with the necessary gas and thermodynamic parameters, ensuring the manufacturability of coatings and the quality of coatings. The device allows to obtain a uniform predetermined thickness of the coating over the entire surface of the product without its rotation around its axis.

The disadvantage of this device is that this design of a supersonic annular nozzle has significant limitations on the size of the sprayed product. In this case, in order for the nozzle to be supersonic, the following condition must be met:

where r _ex is the radius of the exit section of the nozzle, S _ex is the area of the exit section of the nozzle, S _cr is the area of the critical section of the nozzle, and L _n is the length of the supersonic part of the nozzle.

, получим, что диаметр напыляемого проката (d_t≈2r_ex) должен быть более 250 мм. Чтобы наносить покрытия на прокат, например, диаметром 25 мм, необходимо сопло с длиной сверхзвуковой части около 10 мм. Это, в свою очередь, потребует использование частиц размером примерно в 10 раз меньшим (1-3 мкм), чтобы они успели разогнаться до необходимой скорости на таком коротком расстоянии. Дозирование таких частиц представляет значительные сложности. Стоимость таких порошков также значительно возрастает. Отмеченные недостатки накладывают существенные ограничения на использование такой конструкции. Сложная газодинамика сужающейся сверхзвуковой струи на промежутке между срезом сопла и напыляемой поверхностью приведет к появлению скачков уплотнения, что также затруднит процесс напыления.Otherwise, the area of the supersonic part of the nozzle will first increase, and then decrease to the output section. In a supersonic flow this is not possible. Given that the length of the supersonic part of the nozzles commonly used for CGN (optimized for using particles of 10-30 microns in size) is about 100 mm and the area ratio

, we obtain that the diameter of the sprayed steel (d _t ≈ 2r _ex ) should be more than 250 mm. In order to coat the rolled products, for example, with a diameter of 25 mm, a nozzle with a supersonic part length of about 10 mm is necessary. This, in turn, will require the use of particles about 10 times smaller (1-3 microns) in size so that they can accelerate to the required speed at such a short distance. Dosing of such particles is a significant challenge. The cost of such powders also increases significantly. The noted disadvantages impose significant restrictions on the use of such a design. The complex gas dynamics of a narrowing supersonic jet in the gap between the nozzle exit and the sprayed surface will lead to the appearance of shock waves, which will also complicate the spraying process.

The present invention solves the problem of expanding the technological and functional capabilities of the coating process on the outer cylindrical surfaces of products of various sizes without rotating them around its axis and improving the quality of coatings.

To achieve the named technical result in the proposed device for gas-dynamic coating on the outer cylindrical surfaces of the products, containing a feeder-dispenser, a system for supplying working gas and powder to the prechamber, a spraying unit and means for longitudinal movement of the product, it is new that the spraying unit is made in the form N _s annular sections, wherein the number of sections satisfies condition N _s ≥1, arranged along the axis of the sprayed product at a distance from each other and fixed relative Dru other at a predetermined angle, which provides a uniform coating. Moreover, each section of the spraying unit is multichannel, where the channels are formed by flat removable inserts located uniformly around the perimeter of the annular section, forming flat supersonic nozzles with a channel size in the critical section h _cr and an opening angle α _n that provide an angle of impact of the sprayed particles with the surface of the product 60 ÷ 90 ° and the Mach number at the nozzle _exit M _ex = 1 ÷ 3, while the length (L _n ) and width (δ _n ) of the supersonic part of the channels are determined from the relations:

Where

L _n - the length of the supersonic part of the channels, m;

δ _n is the width of the supersonic part of the channels, m;

ρ _p - the density of the material of the sprayed powder, kg / m ³ ;

d _p - the diameter of the sprayed particles, m,

, гдеthe number of channels is determined from the expression:

where

h _cr is the channel size in the critical section, m;

α _n is the opening angle of plane supersonic nozzles, rad;

and the powder is supplied through channels located coaxially to the nozzles.

The implementation of the spraying unit in the form of N _s annular sections installed at the required distance from each other along the axis of the sprayed product and rotated relative to each other at a given angle, provides, firstly, uniform coating due to the application of the sprayed layers from different sections.

или кратный ему. Во-вторых, изменением числа секций мы можем достичь требуемую толщину покрытия.For example, if we have N _s sections, each of which has N _n channels, we must rotate each subsequent section relative to the previous one around the axis of the sprayed product by an angle

or a multiple to him. Secondly, by changing the number of sections we can achieve the required coating thickness.

. Из условия задания числа Маха на срезе сопла 1≤M_ex≤3 можно получить условие на угол раскрытия плоского сверхзвукового сопла

, полученному из условия

.The fact that the channels are arranged uniformly around the perimeter of the annular section also ensures uniformity of the coating thickness, and the fact that they are made in the form of flat supersonic nozzles with an opening angle α _n , which ensures the impact of the sprayed particles with the surface at an angle of 60 ÷ 90 °, in turn provides a high coefficient of spraying. In order for particles to collide with the sprayed surface at an angle of 60 ÷ 90 °, it is necessary that the condition

. From the condition for specifying the Mach number on the nozzle exit 1≤M _ex ≤3, we can obtain the condition on the opening angle of a planar supersonic nozzle

obtained from the condition

.

The choice of the length and width of the supersonic part of the channels according to the ratios L _n = 4.35ρ _p d _p ± 50%, δ _n = 0.065ρ _p d _p ± 50%, provides optimal acceleration of the sprayed particles and, accordingly, high quality coating.

The interchangeability of the inserts allows changing, within certain limits, the length and width of the supersonic part of the channels with the other dimensions of the section unchanged and, thereby, optimizing them when changing the sprayed powder.

, обеспечивает оптимальное перекрытие сверхзвуковых струй непосредственно у напыляемой поверхности, что исключает возникновение скачков уплотнения, ухудшающих процесс напыления.The choice of the number of channels from the ratio:

, provides optimal overlap of supersonic jets directly at the sprayed surface, which eliminates the occurrence of shock waves, worsening the spraying process.

The invention is illustrated by drawings, which depict:

figure 1 - diagram of the spraying unit, made in the form of interconnected two annular sections;

figure 2 is a diagram of a multi-channel section of the spraying unit, a side view along aa of figure 1.

The device for gas-dynamic coating on the outer cylindrical surface of the product contains a means of longitudinal movement of the product, a feeder-dispenser, a system for supplying working gas and powder (not shown in the drawing) to the pre-chambers 1, ring multichannel sections 2 of the deposition unit, installed at a distance from each other along the axis of the sprayed product and fixed relative to each other at a given angle; channels 3 formed by flat interchangeable inserts 4 located uniformly around the perimeter of the annular section; channels 5 for supplying the working gas and channels 6 for supplying the gas-powder mixture located coaxially with the nozzles.

The proposed device for coating the outer cylindrical surface of the product operates as follows.

Compressed gas, such as air, is supplied through an air line to an electric heater (not shown in the drawing), where the flow of this gas is heated to the required temperature. Further, the working gas having a predetermined temperature and pressure is supplied from the gas heater through the channels 5 to the prechambers 1 of the multi-channel annular sections 2. The gas-powder mixture from the powder dispenser through the channels 6 located coaxially to the nozzles also enters the prechambers. Next, the gas-powder mixture is accelerated in the supersonic parts of the nozzles, acquires the parameters necessary for spraying, and when high-speed leakage forms a coating 7 on the outer surface of the product 8, moving relative to the annular sections of the spraying unit (Fig. 1) with a given speed ν _s .

To change, within certain limits, the length and width of the supersonic part of the channels with the other dimensions of the section unchanged and, thereby, to optimize them when changing the sprayed powder, it is necessary to change the flat inserts 4 (Fig. 2) by unscrewing the fixing bolts 9, removing the inserts, placing new ones and again tightening the bolts.

и

выбирается из точности поперечного позиционирования движущегося напыляемого изделия при напылении.The factor before δ _n in the relations

and

selected from the accuracy of the transverse positioning of the moving sprayed product during spraying.

Example 1

Application of an anti-corrosion aluminum coating with a thickness of about 150 microns on the surface of the rolled metal during its production (in the stream).

(эквивалентно тому, что частицы сталкиваются с напыляемой поверхностью под углом не менее 60°) и

(эквивалентно тому, что число Маха на срезе сопла лежит в диапазоне 1≤М_ex≤3) выбираем размер канала в критическом сечении и угол раскрытия сверхзвуковой части сопла. Например, для α_n=60° и М_ex=2.5 получаем h_cr=5,3 мм α_n=4,93°. Из уравнения

выбираем максимальное число каналов N_n=15. Расход газа через рассчитанную секцию можно найти из выражения

, где p₀ и Т₀ - давление и температура торможения воздуха в форкамере. Для p₀=2,0 МПа и Т₀=500 K получаем G₀=0,495 кг/с. Максимальный расход порошка, который можно использовать без существенного падения параметров рабочего газа должен быть менее половины расхода газа, выбираем G_p=0,20 кг/с. С учетом коэффициента напыления порошка 0,75, получаем среднюю толщину покрытия, напыляемого одной секцией узла напыления δ_c1≈55 мкм. В итоге, если узел напыления будет состоять из трех секций, повернутых каждая относительно предыдущей вокруг оси напыляемого изделия на угол

мы получим требуемую толщину покрытия δ_с≈150 мкм. Если выбрать число каналов в каждой секции, например, N_n=3, то в этом случае, средняя толщина напыленного одной секцией слоя будет примерно равна 15 мкм. Для получения требуемой толщины покрытия (δ_с≈150 мкм) нам необходимо применить сопловой узел, состоящий из десяти секций (N_s=10), повернутых каждая относительно предыдущей вокруг оси напыляемого изделия на угол

.We calculate the spraying unit for a circle with a diameter of 32 mm, moving at a speed of 10 m / s. As the sprayed powder, we choose aluminum powder with an average particle size of 10 μm. According to the conditions L _n = 4.35ρ _p d _p ± 50%, δ _n = 0.065ρ _p d _p ± 50%, we obtain L _n ≈ 100 mm and δ _n = 1.75 mm. The factor in front of δ _{n is} chosen equal to 10 due to the high amplitude of the transverse vibrations of the rolling stock during its movement. Further from the conditions

(equivalent to particles colliding with the sprayed surface at an angle of at least 60 °) and

(equivalent to the fact that the Mach number on the nozzle exit is in the range 1≤M _ex ≤3) we select the channel size in the critical section and the opening angle of the supersonic part of the nozzle. For example, for α _n = 60 ° and M _ex = 2.5 we get h _cr = 5.3 mm α _n = 4.93 °. From the equation

select the maximum number of channels N _n = 15. The gas flow through the calculated section can be found from the expression

where p ₀ and T ₀ - pressure and temperature of braking air in the prechamber. For p ₀ = 2.0 MPa and T ₀ = 500 K, we obtain G ₀ = 0.495 kg / s. The maximum powder flow rate that can be used without a significant drop in the working gas parameters should be less than half the gas flow rate, choose G _p = 0.20 kg / s. Taking into account the powder spraying coefficient of 0.75, we obtain the average thickness of the coating sprayed by one section of the spraying unit δ _c1 ≈55 μm. As a result, if the spraying unit will consist of three sections, each rotated relative to the previous one around the axis of the sprayed product by an angle

we obtain the required coating thickness δ _with ≈150 μm. If you select the number of channels in each section, for example, N _n = 3, then in this case, the average thickness of the layer sprayed by one section will be approximately equal to 15 μm. To obtain the required coating thickness (δ _with ≈150 μm), we need to use a nozzle assembly consisting of ten sections (N _s = 10), each rotated relative to the previous one around the axis of the sprayed product by an angle

.

Thus, the presented design features of the device of the present invention, as well as examples of its implementation, provide the expansion of technological and functional capabilities of the coating process on the outer cylindrical surface of products of various sizes without rotating them around its axis, and also improve the quality of coatings.

Claims (1)

A device for gas-dynamic coating on the outer cylindrical surfaces of products containing a feeder-dispenser, a system for supplying working gas and powder to the prechamber, a spraying unit and means for longitudinal movement of the product, characterized in that the spraying unit is made in the form of N _s ring sections, the number sections satisfies the condition N _s > 1, installed along the axis of the sprayed product at a distance from each other and fixed relative to each other at a predetermined angle, providing uniform coating I, each section of the spraying unit is multichannel, and the channels formed by flat interchangeable inserts are located uniformly around the perimeter of the annular section with the formation of flat supersonic nozzles with a channel size in the critical section h _cr and an opening angle α _n providing an angle of impact of the sprayed particles with the surface of the product is 60 ÷ 90 ° and the Mach number at the nozzle exit M _ex = 1 ÷ 3, and the channels located coaxially with the nozzles are designed to supply powder, while the length (L _n ) and width (δ _n ) of the supersonic part of the channels are selected and h ratios:
L _n = 4.35ρ _p d _p ± 50%, δ _n = 0.065ρ _p d _p ± 50%,
where L _n is the length of the supersonic part of the channels, m;
δ _n is the width of the supersonic part of the channels, m;
ρ _p - the density of the material of the sprayed powder, kg / m ³ ;
d _p - the diameter of the sprayed particles, m,
and the number of channels is from the ratio:

where h _cr is the channel size in the critical section, m;
α _n is the opening angle of plane supersonic nozzles, rad.

Images