JP2006212624A - Thermal spraying nozzle device and thermal spraying equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal spraying nozzle device and thermal spraying equipment which can supply a thermal spraying material constantly and can control filming or deposition state. <P>SOLUTION: The thermal spraying nozzle device is provided for forming an ultra-high speed gas stream by introducing a carrier gas to the inlet side of a nozzle and then atomizing a thermal spraying material by that gas stream and discharging the atomized thermal spraying material, wherein the nozzle 2 has: a throat portion 2a for accelerating an introduced carrier gas to supersonic velocity; a diameter-expanded channel portion 2b formed on the downstream side of the throat portion 2a to keep the accelerated gas stream to the supersonic velocity; and a storage section 4 which stores molten metal as a thermal spraying material and is connected to the inlet side end of the nozzle 2 through a communication passage 4a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal spray nozzle apparatus and a thermal spray apparatus that form a coating film or a deposited layer by atomizing a thermal spray material using a gas and causing it to collide with a substrate.

  Conventionally, thermal spraying is known as a technique for forming a film by heating a coating material and causing fine particles in a molten or semi-molten state to collide with a substrate surface at a high speed.

  In this thermal spraying process, since the base material and the coating are physically bonded, it is possible to form a coating on any material that melts, and the formed coating is resistant to wear, corrosion, and heat insulation. It is widely used in various fields because it can satisfy various conditions required for surface treatment such as property.

  Above all, cold spray is a material by heat unlike other thermal spraying methods because it forms a coating by colliding with a base material in a solid state in supersonic flow with an inert gas without melting or gasifying the thermal spray material. There is an advantage that there is no change in the characteristics, and oxidation in the film can be suppressed.

  FIG. 32 shows a schematic configuration of the cold spray apparatus.

  In the figure, the high-pressure gas supplied from the gas source 30 is branched into two pipes 31 and 32, the mainstream gas flowing through the pipe 31 is heated by the gas heater 33, and the remaining gas flowing through the pipe 32 Is introduced into the powder feeder 34.

  The gas heated by the gas heater 33 is introduced into the chamber 36 through the pipe line 35, and the powder supplier 34 supplies the powder particles to the chamber 36 through the pipe line 37.

  The mixture of gas and powder particles mixed in the chamber 36 is accelerated by passing through the converging portion 38a and the diffusing portion 38b of the supersonic nozzle 38, and collides with the base material 39 as a supersonic jet flow. (For example, refer to Patent Document 1).

On the other hand, molten metal is used as the thermal spray material, and it is flowed in a thin film state from a container having a slit-like outlet, and atomized by a sonic gas flow passing through a nozzle having a slit-like orifice provided in the vicinity of the nozzle outlet in a laminar state. There has also been proposed a method (see, for example, Patent Document 2).
JP 2004-76157 A Special table 2002-508441 gazette

  However, in the former cold spray device, powder particles at room temperature are collided and heat generated at the time of plastic deformation is locally heated above the melting point to adhere to the substrate, so that, for example, a particle speed of 600 m / s or more is obtained. In addition, a gas pressure of 1.0 to 3.0 MPa is necessary, and there is a problem that handling is difficult because the gas needs to be preheated to 600 ° C. Moreover, it is not easy to supply the powder particles uniformly.

  In addition, the latter thermal spraying apparatus atomizes at supersonic speed, but does not design a nozzle to accelerate particles, so a high-density coating that can eliminate HIP (Hot Isostatic Pressing) It is impossible to obtain high density deposition.

  The present invention has been made in consideration of the problems in the conventional thermal spraying apparatus as described above. The thermal spraying nozzle apparatus and thermal spraying capable of supplying a thermal spraying material at a constant level and controlling the coating or deposition state. A device is provided.

  The thermal spray nozzle apparatus of the present invention is a thermal spray nozzle apparatus that introduces a carrier gas from the inlet side of the nozzle to form an ultra-high-speed gas flow, atomizes the thermal spray material by the gas flow, and discharges it. A storage part for storing molten metal as a thermal spray material is connected to the part through a communication path, and the nozzle is a throat part for forming a supersonic gas flow and a diameter-enlarged flow formed downstream thereof toward the outlet This enlarged diameter flow passage portion cools the metal particles atomized by the supersonic gas flow to a solidified or semi-solidified state and discharges them in a predetermined direction from the outlet side of the nozzle. It is summarized as follows.

  In the thermal spray nozzle device, a molten metal lead-out pipe extends from the storage portion toward the center of the throat or the downstream side of the throat as the communication path, and the accelerated carrier gas flows through the outer periphery of the molten metal lead-out pipe. It is preferable to configure.

  Moreover, the nozzle of this invention makes it a summary that the opening angle of the diameter expansion flow path part in the throat part downstream is a half apex angle of 15 degrees or less.

  The length of the diameter expansion channel is determined based on the flight distance of the atomized metal particles and the temperature of the metal particles, and is determined based on the flight distance until the metal particles are solidified or semi-solidified. Is obtained by calculating the flight time until the atomized metal particles change into a solidified or semi-solid state, substituting the flight time into the following formula, and determining the flight distance of the particles, The gist is that it is longer than the flight distance.

However, the flight distance l _f is the particle flight time to t _f particles reach the solidification or semi-solidification, u _g is the gas flow rate, the density of [rho _g is the gas density of the [rho _s is the particle, d _s is Particle diameter, _ag is the speed of sound of gas,
Further, when the carrier gas inlet pressure is p _o and the nozzle outlet pressure is P _B , the inlet pressure p _o is preferably introduced into the nozzle in a state satisfying the following formula.

  Here, κ: specific heat ratio of compressed gas, M: Mach number in the nozzle enlarged portion downstream of the throat portion

  The thermal spraying device of the present invention includes a thermal spray nozzle device having the above-described configuration, a carrier gas supply device that is connected to the nozzle via a conduit and introduces carrier gas under pressure, and a base material that collides the nozzle and emitted particles. The gist of the invention is that it comprises a sealed container for storing the container and a decompression means for decompressing the inside of the sealed container.

  The thermal spraying device of the present invention includes a thermal spray nozzle device having the above-described configuration, a molten metal supply device that is connected to the reservoir through a connecting pipe and continuously pressurizes molten metal against the molten metal in the reservoir. And a base material supply device that continuously supplies the base material.

  According to the present invention, the thermal spray material can be supplied constantly, and the coating or deposition state can be controlled.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 shows a basic configuration of a thermal spray nozzle device according to the present invention.

1. Principle of Thermal Spray Nozzle Device A thermal spray nozzle device 1 shown in FIG. 1 supplies molten metal M directly into a supersonic nozzle (hereinafter abbreviated as a nozzle) 2.

  While a supersonic airflow flows in the nozzle 2, the molten metal supplied into the nozzle 2 is a low-speed flow. A shearing force acts between the two and the surface tension of the molten metal acts to Atomization (atomization) of the molten metal is performed downstream of the throat portion 2a.

  Atomized metal particles (hereinafter abbreviated as particles) are accelerated in the nozzle 2 and rapidly cooled to solidify. That is, the thermal spray nozzle device 1 of the present invention is integrally provided with a throat portion 2a where the atomizing process is performed and a diameter-enlarged flow path portion 2b where the flight cooling process is performed continuously with the atomizing process.

  The particles discharged from the nozzle 2 immediately after solidification collide with the base material 3 at a speed of about 450 m / s. Due to the deformation at the time of the collision, the particles generate heat, and a part of the particles rises to the melting point or higher, so that the particles adhere to the substrate 3 (see the impact attachment step in the figure).

  In the figure, reference numeral 4 denotes a storage portion for storing the molten metal M, and has a communication passage 4 a communicating with the nozzle 2.

  The leading end of the communication passage 4a extends as a molten metal outlet tube 4b toward the center of the cylindrical hole of the throat portion 2a, and the accelerated carrier gas flows through the outer periphery of the molten metal outlet tube 4b. It has become.

  The principle that the solidified particles collide with the base material 3 is the same as that of the conventional cold spray. The collided particles are remarkably plastically deformed and dented into a crater, and a dense structure without voids is formed in the film (or deposited layer). Will be obtained. Therefore, it is not necessary to perform a HIP (Hot isostatic pressing) process as a post-treatment, that is, to remove residual voids by applying pressure to the molding material on which the film is formed.

  Further, when nitrogen gas is used as a carrier gas (hereinafter abbreviated as “gas”) for generating a supersonic airflow, a low oxygen content molding material can be obtained because oxidation does not proceed after particle collision. Furthermore, since the particles are solidified within only 1 ms when the particles fly through the nozzle 2, the progress of nitriding can be prevented.

  Moreover, since the molten metal is used as the thermal spray material and the particles collide with the base material 3 at a temperature slightly lower than the freezing point, the collision with a lower Mach number (for example, about Mach number 2) compared to the cold spray. Even so, the surface temperature of the substrate 3 is equal to or higher than the melting point, so that the particles can be reliably attached to the substrate 3. The Mach number means the gas velocity / sound velocity.

The nozzle 2 is configured such that the nozzle length of the enlarged portion is set to 100 mm or more, and operates in a state where the carrier gas total pressure p ₀ satisfies the following formula (1).

Here, p _{0 is the} carrier gas total pressure (inlet pressure on the throat upstream side), p _{B is the} nozzle outlet back pressure, M is the Mach number in the sprayed material melting part, and κ is the specific heat ratio of the carrier gas.

Further, the Mach number M is related to the cross-sectional area A ^* of the throat portion 6 and the enlarged intra-nozzle cross-sectional area A by the equation (2).

As shown in FIG. 2 (a), the enlarged cross-sectional area is a conical enlarged portion whose diameter gradually increases from the narrowest portion A ^* as the throat portion toward the downstream side, and FIG. 2 (b). As described above, an expanded portion whose diameter suddenly expands from the narrowest portion A ^* toward the downstream side and becomes substantially constant thereafter is included.

  It is also known that when a compressed gas having a pressure expressed by the equations (1) and (2) is supplied to a tapered nozzle, a supersonic flow is achieved up to the enlarged portion of the nozzle. In the narrowest part, the high-speed airflow is Mach 1 (about 340 m / s). Molten metal exposed to the high-speed air stream is atomized into fine particles. Experimentally, it is clear that Hinze (Honze, JO, Fundamentals of the Hydrodynamic Mechanism of Splitting in Dispersion Processes, AIChEJ., Vol, No. 3, 1955, pp. 289-295) is expressed by equation (3). Has been.

Here, ρ _G : gas density, V _G : gas velocity at the nozzle inlet, V _L : liquid velocity, D _L : droplet diameter after splitting, and σ: liquid surface tension.

  When an aluminum alloy is taken as an example of the molten metal and nitrogen gas is supplied to the nozzle at a pressure of 0.8 MPa, the diameter of the aluminum alloy particle after atomization obtained from Equation (3) is about 20 μm.

  The atomized particles are accelerated and cooled by the supersonic airflow, and finally ejected from the nozzle 2 at a supersonic speed.

  The acceleration and cooling during this time can be estimated by numerical analysis. Specifically, the mass conservation, momentum conservation, and energy conservation equations of the quasi-one-dimensional compressible fluid conservation type display are solved by simultaneous equations (4) and particle motion equations (6).

2. Numerical analysis method
(1) First, the symbols used in the numerical analysis method described later are shown.
A: Nozzle sectional area C _D : Drag coefficient of particle Cp: Specific heat D: Nozzle diameter d: Particle diameter f: Wall friction coefficient g: Gravitational acceleration h: Specific enthalpy m dot: Mass flow rate Nu: Nusert number p: Gas pressure Pr : Prandtl number Q: Energy per unit time required for nozzle heating R: Gas constant Re: Reynolds number T: Temperature u: Flow velocity x: Distance in nozzle flow direction α: Stefan-Boltzmann constant ε: Emissivity κ: Specific heat ratio λ: Thermal conductivity μ: Viscosity coefficient ρ: Density The meanings of the subscripts are as follows.
g: Gas s: Second phase (droplet, particle, powder)
x: Distance from nozzle throat W: Nozzle wall

(2) Governing equation of gas phase The quasi-one-dimensional compressible fluid conservation type mass conservation, momentum conservation, and energy conservation equations are shown in (4) below.

ただし、ノズル壁の乱流熱伝達にはJohnson-Rubeshinの式(5)を用いる。

However, Johnson-Rubeshin equation (5) is used for turbulent heat transfer on the nozzle wall.

  Further, s and e represent a momentum generation term and an energy generation term representing the interaction between the gas phase and the second phase, respectively.

  The actual equation (1) can be solved by discretizing the advection term using Roe's Flux difference Splitting method, which is a MUSCL (Mooneone Upstream-centred Schemes for Conservation laws), and using the 4-stage Runge-Kutta method. Integration is performed.

(3) Governing equation of the second phase (droplet, particle, powder) The velocity of the particle can be obtained by solving the particle equation of motion (6).

ただし、

However,

ここで抗力係数にはKurtenの式(8)を用いている。

Here, Kurten's formula (8) is used as the drag coefficient.

粒子の温度は、粒子のエネルギ方程式(9)を解くことにより得ることができる。

The temperature of the particles can be obtained by solving the particle energy equation (9).

ただし、ノズル壁温度がガス温度と等しくなる断熱壁の場合、

However, in the case of a heat insulating wall where the nozzle wall temperature is equal to the gas temperature,

また、ノズル壁１ｂを加熱した等温壁の場合、

In the case of an isothermal wall that heats the nozzle wall 1b,

ここでヌセルト数にはRanz-Marshallの式(12)を用いている。

Here, the Ranz-Marshall equation (12) is used as the Nusselt number.

For the actual solution of Equation (6) and Equation (9), the QUICK method is used for discretization of the advection term.
Time integration is performed using the four-stage Runge-Kutta method.

(4) Amount of heat required for nozzle heating The amount of heat required to maintain isothermal conditions can be estimated by equation (13).

(5) Nozzle length In the operation using the thermal spray nozzle device of the present invention, since the velocity of the atomized particles is configured to collide with the deposit before decelerating, the distance from the nozzle outlet to the deposit Is a very short setting. Therefore, it can be considered that the particle velocity and enthalpy at the nozzle outlet are substantially maintained and deposited.

  In addition, the state of the deposit greatly depends on the state of the particles at the time of deposition. However, in the case where particles are collided and deposited at a subsonic speed like a conventional thermal spray nozzle device, if the particles are in a solidified state, It cannot be attached to the deposit.

  On the other hand, the thermal spray nozzle apparatus of the present invention has an operating condition of colliding and depositing particles in a semi-solid state or a solid state in a supersonic speed, which has not been utilized in the past, which has a higher solid phase ratio. . Therefore, assuming that the molten metal is atomized and changes to a semi-solid state while flying, the minimum flight distance required so far is obtained, and this flight distance is required for the device. The minimum nozzle length is specified.

  First, the equation of motion representing particle acceleration is as shown in equation (6),

である。

It is.

  Since this equation (6) is described from the Euler coordinate system stationary with the nozzle, it is convenient for numerical calculation using a fixed calculation grid.

However, it is inconvenient to follow the state of each particle and confirm the particle velocity and particle enthalpy, so it can be expressed by the equation described from the Lagrange coordinate system that moves with the flying particles. The following formula (14) is obtained. However, for the sake of simplicity, the gravitational term that has little effect is ignored. In the section where the flight distance is still short, it is assumed that the gas flow velocity u _g > the particle velocity u _s always holds, assuming that the particles are in the acceleration process that is pushed like a tailwind from behind by the gas flow.

Here, taking the relative speed between the speed u _s flow rate u _g and particle gas, as U = u _g -u _s, the approximately gas flow rate is supersonic is assumed to be constant in the nozzle Equation (14) can be transformed into Equation (15).

In the formula (15), as the drag coefficient C _D is shown in equation (12), but when the relative velocity U is subsonic can be expressed by a function of the Reynolds number, the relative velocity U is the case immediately after the atomization ultrasonic Since the ratio of speed of sound is high, in the graph shown in FIG. 3 (sphere obtained from bullet path measurement, and drag coefficient of cone-cylindrical body, explanatory diagram of Mach number dependence), the relationship between Mach number and spherical object is shown here. Approximation is made by the equation (16) from the experimental result of the drag coefficient (see the approximate straight line E in the figure).

  3 is quoted from the 2nd edition McGrae-Hill Series in Aeronautical and Aerospace Engineering, Modern Compressible Flow with historical Perspective.

ただし、ａ_ｇはガスの音速、Ｍはマッハ数。

Where _ag is the speed of sound of gas and M is the Mach number.

  From Expression (16) and Expression (15), Expression (17) expressing the relationship between the particle flight time t and the relative velocity U is obtained.

ここで、ｔ＝０では粒子速度ｕ_ｓ＝０としている。

Here, at t = 0, the particle velocity u _s = 0.

The relationship between the flight time t _f flight distance l _f is determined from the equation (18).

However, _{u g} is the gas flow rate, the density of [rho _g is the gas density of the [rho _s is the particle, _{d s} is the particle diameter

Knowing the flight time t _f until the particles reach the semi-solidified, is calculated flight distance l _f it to the particle, the flight distance l _f is equal to the minimum nozzle length that is required. Therefore, the flight time t _f until the particles reach semi-solidification is determined. The cooling of the particles is given by equation (9) shown above.

式(14)と同様に、ラグランジュ座標系で記述すると、式(19)のようになる。

Similar to equation (14), when described in the Lagrange coordinate system, equation (19) is obtained.

Here, approximately the initial molten metal temperature, liquidus temperature, approximately equal the solidus temperature and thereby representative of the values at the melting point T _m of a material, definitive and T s ₌ T _m. The gas temperature T _s and the nozzle wall surface temperature T _w are also approximately constant.

  The Nusselt number Nu representing the degree of heat transfer is expressed by equation (12), but when rewritten using the relative speed U, equation (20) is obtained.

  Further, when the solidification latent heat of the sprayed metal is L, Equation (21) is established in order to enter a semi-solid state where the solid phase ratio is larger.

  In the formula, L / 2 is set since a substantially intermediate state where the liquid phase changes to the solid phase is in a semi-solid state.

Obtaining the minimum nozzle length means obtaining the shortest flight time t _f until the particles reach semi-solidification, and in this case, the equal sign is established in Expression (21).

If the Nussel number Nu is eliminated from Equation (19) and Equation (20), the relative velocity U is also eliminated using Equation (17), and the equation of Equation (21) is used, the particles are semi-solidified. The relational expression (22) of the shortest flight time t _f until reaching the state is obtained.

Where Pr is the Prandtl number of the gas, λ is the thermal conductivity of the gas, T _m is the melting point of the material, T _g is the temperature of the gas, μ _g is the viscosity coefficient of the gas, and the above equation (22) is solved for t _f Although not possible, it can be solved numerically using Newton's method.

From the above, determine the shortest flight time t _f from equation (22) by substituting the equation (18), the shortest flight distance, i.e. the minimum nozzle length l _f obtained.

The thermal spray nozzle device according to the present invention is a device using a nozzle having a nozzle length _lf or more, and adheres to a substrate or deposit even in a solidified state by accelerating particles to supersonic speed. Therefore, theoretically, there is no upper limit to the nozzle length.

  FIG. 4 is a graph in which the minimum nozzle length is specifically obtained using aluminum and copper. Necessary when particles having various particle sizes are in a semi-solid state exceeding a solid phase ratio of 0.5. This shows the nozzle length. In the graph, the horizontal axis indicates the particle diameter, and the vertical axis indicates the nozzle length. The carrier gas conditions are the same as in Table 1 described later.

  As a result of atomization, for example, when the average diameter in terms of volume occupancy is 50 μm, a nozzle length of 0.17 m for aluminum and 0.12 m for copper is required.

  By the way, conventionally, when flowing molten metal to a supersonic nozzle for the purpose of atomization, in order to avoid particles from adhering to the inner wall surface of the nozzle, as shown in FIG. A large nozzle with a half apex angle of θ> 15 ° is used. The half apex angle means an angle formed by the nozzle central axis and the nozzle inner wall.

In this case, the cross-sectional area ratio A / A ^* rapidly increases and the Mach number M also increases rapidly (see equation (2)). However, the isentropic change equation (23) and the vertical shock wave relationship equation (24 ) appears shockwave surface upon reaching the Mach number M ₁ obtained from which the downstream side becomes a subsonic as a boundary, by the opening angle of the inner wall of the nozzle is large, the gas flow in the vicinity of the inner wall from the inner wall surface It will peel off.

The Mach number M _{1 at} this time is obtained from the equation (25), and the cross-sectional area ratio A / A ^* at the portion where the shock wave front appears is obtained from the equation (26).

  Such a nozzle is conventionally suitable for atomization, but the gas flow in the nozzle immediately becomes subsonic, and there is no concept of accelerating particles. On the other hand, the nozzle of the present invention has a nozzle opening angle of 15 ° or less at a half apex angle to prevent separation of the flow, and adheres particles to the substrate or deposit even in a semi-solid state. It is configured to accelerate the atomized particles to supersonic speeds. In other words, the nozzle of the present invention has a configuration in which the distance from the nozzle narrowest portion to the site where the shock wave front is generated is extended until the particles reach a solidified or semi-solidified state.

  From the above description, the conditions of the supersonic nozzle of the present invention can be defined by the following (a) to (c).

(A) The nozzle opening angle is a half apex angle and θ ≦ 15 °.
(B) The shock wave upstream Mach number M ₁ obtained by the equation (25) based on the carrier gas total pressure p ₀ and the nozzle outlet back pressure p _B when the nozzle opening angle is a half apex angle θ ≦ 15 °, Substituting into (26), the nozzle cross-sectional area A ₁ is obtained, and the nozzle length l _f up to the position where the nozzle cross-sectional area A ₁ is obtained is the shortest flight until the particle reaches the semi-solid state according to equation (18). it is the minimum nozzle over a length l _f which is obtained from the relational expression defining the time (22). FIG. 6 shows a case where a shock wave is generated in the nozzle.
(C) nozzle opening angle a theta ≦ 15 ° semi-vertical angle, and nozzle length l _f is the formula (18), the relational expression that the particles defining the shortest flight time to reach a semi-solid (22 ) because it is the shortest nozzle than the length l _f which is obtained, substituting a carrier gas total pressure p _0, formula based on the nozzle outlet back pressure p _B of the shock wave upstream Mach number M ₁ which is obtained by (25), further (26) nozzle cross-sectional area a ₁ found by is a larger nozzle than the nozzle outlet cross-sectional area a _e.

  In this case, as shown in FIG. 7, since the entire nozzle area is supersonic, the shock wave front is generated downstream of the nozzle outlet.

3. Actual nozzle design
3-1) Material property values and constraint conditions Table 1 shows the material property values and constraint conditions used in the actual nozzle calculation.

  However, the maximum half apex angle in the table means the maximum angle formed by the nozzle central axis and the nozzle inner wall.

3-2) Study conditions Molten metal (particle) mass flow rate [kg / s] 4 conditions: 0.025, 0.050, 0.075, 0.100
Particle size [μm] 3 conditions: 20, 50, 100
Nozzle throat diameter [mm] 2 conditions: φ25, φ35
However, the gas mass flow rates correspond to 0.9 [kg / s] (throat diameter φ25) and 1.8 [kg / s] (throat diameter φ35), respectively.

  Under the above conditions, the nozzle shape was obtained when appropriate expansion (nozzle outlet static pressure = back pressure = atmospheric pressure) was obtained, and the relationship between the particle temperature and the particle velocity was examined. Also, since the supersonic flow does not affect the downstream side to the upstream side, for example, the calculation result at the 300 mm position in the 500 mm long nozzle can be regarded as the state at the outlet of the 300 mm long nozzle as it is. . This is different from the subsonic nozzle.

3-3) Configuration of actual nozzle
3-3-1) General A typical example of the nozzle shape designed for spray acceleration is shown in the graph of Fig. 8.
Here, the maximum half apex angle of the nozzle is 5 ° (see Table 1).

  This nozzle has (a) that the dispersed droplets after atomization are rapidly expanded to the maximum diameter so that they do not adhere to the nozzle wall, and (b) the direct diameter at the maximum diameter at which the speed is maximized to accelerate the particles. It is configured for the purpose of taking a long tube portion.

  However, the nozzle according to the present embodiment occupies most of the nozzle when the pressure ratio is lower than the design value or when many cold particles are supplied, compared to the conical nozzle generally used in cold spray. There is an inconvenience that all the pipe parts become subsonic. Therefore, it is unsuitable for operation in a state outside the design value, and is suitable for production equipment that repeats operation under the same conditions. Therefore, the graph of FIG. 9 shows the nozzle outlet diameter that achieves appropriate expansion when the operation is performed under the same conditions.

  In the graph, whether the nozzle throat diameter is φ25 mm or φ35 mm, the nozzle outlet diameter increases as the molten metal flow rate increases, because the gas receives the heat brought in by the molten metal and can expand. is there.

  The interesting point is that if the nozzle is designed under a condition where the molten metal mass flow rate is low, even if a flow rate exceeding the design is supplied to the nozzle, the expansion efficiency becomes lower and the acceleration efficiency decreases, but the momentum delivered to the particles It is possible to drive up to the limit by. Conversely, it can be seen that acceleration to supersonic speed is not possible with a molten metal mass flow rate smaller than the design value.

  Next, Table 2 shows the relationship between the nozzle throat diameter and the gas mass flow rate obtained as a result of the design calculation with the actual nozzle in the case of no heating.

3-3-2) In the case of particle diameter φ20 μm after atomization FIGS. 10 to 12 show the Mach number distribution in the nozzle, gas temperature / velocity distribution, particle temperature / velocity when the particle diameter φ20 μm after atomization and the nozzle throat diameter φ25 mm, respectively. Show the distribution. In each graph described below, Distance on the horizontal axis indicates the nozzle length, Mach number on the vertical axis indicates the Mach number, Gas temp indicates the gas temperature, Gas Velc indicates the gas flow rate, and Solid temp indicates The particle temperature and Solid Velc indicate the particle velocity, respectively.

  FIGS. 13 to 15 show the Mach number distribution in the nozzle, the gas temperature / velocity distribution, and the particle temperature / velocity distribution when the particle diameter after atomization is 20 μm and the nozzle throat diameter is 35 mm, respectively.

  Because of the heated Rayleigh flow that receives heat from the molten metal, the Mach number decreases, the gas temperature increases, and the gas velocity decreases.

  In this embodiment, since the nozzle outlet diameter is determined so as to achieve proper expansion after heating, the gas static pressure is almost equal to the atmospheric pressure, and the gas velocity is about 510 m / s.

  An interesting point is that if the nozzle outlet diameter is determined so as to achieve an appropriate expansion after heating for each of these conditions, the particle side state no longer results in almost the same particle velocity and particle temperature.

  This is because the gas velocity distribution in the nozzle is almost equal and the gas temperature difference is smaller than the temperature difference with the molten metal.

  Further, the difference between the throat diameters φ25 mm and φ35 mm appears in the gas temperature as shown in FIGS. 11 and 14, but hardly appears in the gas velocity. Thus, particles affected by gas temperature will show a difference in particle temperature but not in particle velocity.

  When the particle diameter is 20 μm, solidification is completed with a nozzle length of about 160 mm, but the particle velocity is only about 400 m / s. In this case, if the nozzle length is extended to 500 mm, the particle velocity can be accelerated to 480 m / s, but the particle temperature at this time is cooled to 400K.

  Thus, when the particle diameter is φ20 μm, the particles tend to be cooled too much compared to acceleration, and therefore the length of the nozzle needs to be determined carefully.

3-3-3) In the case of particle diameter after atomization φ50 μm FIGS. 16 to 18 show the Mach number distribution in nozzle, gas temperature / velocity distribution, particle temperature / velocity when the particle diameter after atomization is φ50 μm and nozzle throat diameter φ25 mm, respectively. Show the distribution.

  19 to 21 show the Mach number distribution in the nozzle, the gas temperature / velocity distribution, and the particle temperature / velocity distribution when the particle diameter after atomization is 50 μm and the nozzle throat diameter is 35 mm, respectively.

  The tendency of the Mach number, gas temperature, and particle velocity is not significantly different from that in the case of the particle diameter φ20 μm, but the critical difference is the particle temperature cooling rate seen in FIGS.

  When the particle diameter is 50 μm, a flight distance of about 1.2 m is required in the nozzle until solidification is completed. Correspondingly, if the nozzle length is extended by 1.2 m, the particle acceleration will be much closer to the asymptotic line of acceleration.

  Under these conditions, the particles are discharged from the nozzle at a particle temperature of 750 K and a particle speed of 470 m / s, and therefore the most preferable collision adhesion condition for the substrate.

3-3-4) In the case of particle size after atomization φ100 μm FIGS. 22 to 24 show the Mach number distribution in the nozzle, gas temperature / velocity distribution, and particle temperature / velocity distribution in the case of particle size φ100 μm after atomization.

  From this calculation result, in the case of a particle diameter of φ100 μm, the nozzle length is required to be 5 m until the cooling rate further decreases and solidification occurs. The acceleration of the particles has already been completed when the nozzle length is 3 m, and since the speed reaches about 450 m / s, the cooling is delayed. This situation occurs when atomization is poor and sufficient atomization is not possible.

  FIG. 25 shows a configuration when the thermal spraying apparatus according to the present invention is applied to batch processing.

  In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  As the carrier gas, helium gas having a small molecular weight, which is preferable in terms of increasing the speed of sound when accelerating the particles, is used instead of nitrogen gas.

  The carrier gas supplied from the helium gas cylinder 10 is branched into two pipelines 11 and 12, and the carrier gas flowing through the pipeline 11 applies a head pressure to the molten metal stored in the reservoir 4, and the pipeline The carrier gas flowing through 12 is introduced into the nozzle 2 and is accelerated to supersonic speed by passing through the throat portion 2a. The helium cylinder 10 and the pipelines 11 and 12 function as a carrier gas supply device that introduces carrier gas under pressure.

  The molten metal flowing down from the reservoir 4 is atomized by the supersonic gas flow in the nozzle 2, further cooled in the nozzle 2, and discharged from the tip of the nozzle 2.

  The discharged particles collide with and adhere to the surface of the substrate 3. The nozzle 2 and the substrate 3 are accommodated in a chamber 13 as a sealed container, and this chamber 13 is connected to an air storage tank 16 via a cyclone device 14 as an exhaust device and an exhaust vacuum pump (decompression means) 15. ing. The cyclone device 14 collects particles floating in the exhaust and supplies only the gas to the exhaust vacuum pump 15.

  The exhaust device is provided to increase the particle velocity by increasing the Mach number of the carrier gas, and the helium gas recovered in the storage tank 16 is compressed by the compressor 17 and reused. Yes.

  FIG. 26 shows a basic configuration when the thermal spraying apparatus according to the present invention is applied to a continuous molding process.

  In the continuous molding process shown in the figure, a continuous melting furnace 20 is connected to the storage section 4, and the storage section 4 and the continuous melting furnace 20 are communicated with each other via a connecting pipe 21. Moreover, the height of the continuous melting furnace 20 is set so that the internal pressure of the reservoir 4 becomes 0.8 MPa by the head pressure. The continuous melting furnace 20 arranged at the predetermined height functions as a molten metal supply device that continuously supplies pressurized molten metal under pressure.

  In this way, the molten metal can be continuously supplied from the reservoir 4 to the nozzle 2.

  Further, the base material 22 is pulled in the direction of the arrow B by the rotation of the take-up rollers (base material supply devices) 23a and 23b while rotating in the direction of the arrow A. Thereby, the particles can be continuously sprayed and formed on the substrate 22.

  27 to 31 show another embodiment of the nozzle 2 of the present invention. The nozzle itself is made of a non-metal such as ceramic or carbon, so that the affinity of the surface is deteriorated and the inner wall of the nozzle is made. The metal particles adhering to can be easily blown off by the supersonic gas flow. In these drawings, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

A nozzle 40 shown in FIG. 27 is manufactured by using zirconia to spray an aluminum alloy, and the outside of the nozzle 41 is covered with a ceramic cylinder 42, and the temperature rises up to 900 ° C. around the cylinder 42. The nozzle heater 43 that can be warmed is wound a plurality of times. As the nozzle 41, for example, a material called partially stabilized zirconia having high strength, high wear resistance, and high corrosion resistance to which yttria (Y ₂ O ₃ ) is added as a stabilizer may be used. preferable.

  The nozzle 44 shown in FIG. 28 is constituted by a ceramic fiber heater 45, and more specifically, a heating element is embedded in a high-temperature insulating ceramic fiber obtained by fiberizing a material mainly composed of alumina and silica. Are integrally formed. In addition, 46a and 46b in the figure have shown the electrode connection part of the heater.

  The nozzle 47 shown in FIG. 29 is configured such that a carbon heater 49 is provided around the outer wall of the body of the ceramic nozzle 48 and heated by radiation.

  The carbon heater 49 is divided into a plurality of portions by slits 51d, 51e alternately formed with a fixed length from the upper and lower sides of the cylindrical nozzle 48, and 49a and 49b are electrode connections of the carbon heater 49. Part. Reference numeral 50 denotes a cylindrical reflection case whose inner wall is finished to be a mirror surface, and is provided to increase radiation efficiency.

  In the nozzle 47 having the above configuration, when electric power is supplied from a power source (not shown) to the carbon heater 49 through the electrode connection portions 49a and 49b, the carbon heater 49 generates heat from the inside due to Joule heat generation by energization. The nozzle 48 is heated by radiant heat transfer from the carbon heater 49, and the metal adhering to the inner wall of the nozzle 37 is melted.

  A nozzle 51 shown in FIG. 30 is manufactured by a carbon heater 52, and 52a and 52b indicate electrode connection portions thereof. If the ceramic nozzle is replaced with a carbon or carbon composite nozzle, the emissivity of the nozzle surface is further increased, and the heating efficiency of the nozzle 51 can be further increased.

  In FIGS. 29 and 30, since the carbon itself undergoes an oxidation reaction in the presence of oxygen, the entire apparatus is covered with a chamber to prevent this, and a gas such as argon or nitrogen is used as a high-pressure gas, and the inside of the chamber is inert. The atmosphere is replaced.

  Also, the nozzle is made of a metal material having a good thermal conductivity, such as copper, and a ceramic coating is formed on the inner wall of the nozzle by applying ceramic spraying. It can also worsen sex.

  In the nozzle 53 shown in FIG. 31, a zirconia film (portion indicated by a thick broken line in the figure) 55 is formed on the inner surface of the copper nozzle 54, and the nozzle heater 43 is wound around the outer peripheral surface a plurality of times.

It is a perspective view which shows the structure of the thermal spray nozzle apparatus which concerns on this invention. (a) And (b) is explanatory drawing which shows the definition of a nozzle expansion part. It is a graph explaining the relationship between a Mach number and a drag coefficient. It is a graph which shows the nozzle length according to a particle size. It is explanatory drawing which shows the conventional nozzle opening angle. It is explanatory drawing which shows the case where a shock wave generate | occur | produces in a nozzle. It is explanatory drawing which shows the case where the nozzle whole area becomes a supersonic flow. It is a graph which shows the typical example of a nozzle shape. It is a graph which shows the nozzle exit diameter used as appropriate expansion. It is a graph which shows the relationship between the nozzle length and Mach number in a particle diameter of 20 μm and a throat diameter of 25 mm. It is a graph which similarly shows nozzle length and gas temperature / velocity distribution. It is a graph which similarly shows nozzle length and particle temperature / velocity distribution. It is a graph which shows the relationship between the nozzle length and Mach number in a particle diameter of 20 μm and a throat diameter of 35 mm. It is a graph which similarly shows nozzle length and gas temperature / velocity distribution. It is a graph which similarly shows nozzle length and particle temperature / velocity distribution. It is a graph which shows the relationship between the nozzle length and Mach number in a particle diameter of 50 μm and a throat diameter of 25 mm. It is a graph which similarly shows nozzle length and gas temperature / velocity distribution. It is a graph which similarly shows nozzle length and particle temperature / velocity distribution. It is a graph which shows the relationship between the nozzle length and Mach number in a particle diameter of 50 μm and a throat diameter of 35 mm. It is a graph which similarly shows nozzle length and gas temperature / velocity distribution. It is a graph which similarly shows nozzle length and particle temperature / velocity distribution. It is a graph which shows the relationship between the nozzle length in a particle diameter of 100 micrometers, and Mach number. It is a graph which similarly shows nozzle length and gas temperature / velocity distribution. It is a graph which similarly shows nozzle length and particle temperature / velocity distribution. It is explanatory drawing which shows the structure of the thermal spraying apparatus applied to a batch process. It is explanatory drawing which shows the structure of the thermal spraying apparatus applied to a continuous shaping | molding process. It is the FIG. 1 equivalent view which showed the 2nd form of the nozzle which concerns on this invention. It is the FIG. 1 equivalent view which showed the 3rd form of the nozzle which concerns on this invention. It is the FIG. 1 equivalent view which showed the 4th form of the nozzle which concerns on this invention. FIG. 9 is a view corresponding to FIG. 1 showing a fifth embodiment of the nozzle according to the present invention. FIG. 9 is a view corresponding to FIG. 1 showing a sixth embodiment of the nozzle according to the present invention. It is explanatory drawing which shows the structure of the conventional cold spray apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal spray nozzle apparatus 2 Nozzle 2a Throat part 3 Base material 4 Storage part 4a Communication path 4b Molten metal outlet pipe 10 Helium gas cylinder 11, 12 Pipe line 13 Chamber 14 Cyclone apparatus 15 Exhaust vacuum pump 16 Gas storage tank 17 Compressor 20 Continuous melting Furnace 21 Connection tube 22 Base material 23a, 23b Take-up roller

Claims (8)

In a thermal spray nozzle device that introduces a carrier gas from the inlet side of the nozzle to form a super-high-speed gas flow, atomizes the thermal spray material by the gas flow, and discharges it,
A reservoir for storing molten metal as the spray material is connected to an inlet side end of the nozzle via a communication path, and the nozzle has a throat portion for forming a supersonic gas flow and an outlet direction downstream thereof. A diameter-enlarged flow path portion formed toward the nozzle, and the diameter-enlarged flow path portion cools the metal particles atomized by the supersonic gas flow to a solidified or semi-solidified state in the flow path. The thermal spray nozzle device is configured to discharge in a predetermined direction from the outlet side of the nozzle.   As the communication path, a molten metal outlet pipe extends from the storage portion toward the center of the throat or downstream of the throat, and the accelerated carrier gas flows through the outer periphery of the molten metal outlet pipe. The thermal spray nozzle device according to claim 1.   The thermal spray nozzle device according to claim 1 or 2, wherein an opening angle of the enlarged diameter flow path portion on the downstream side of the throat portion is a half apex angle of 15 ° or less.   The length of the diameter-enlarged flow path portion is determined based on a flight distance until the metal particles are solidified or semi-solidified by modeling the flight distance of the atomized metal particles and the metal particle temperature. Spray nozzle equipment. Obtain the flight time until the atomized metal particles change to a solidified or semi-solidified state, substitute the flight time into the following equation to obtain the flight distance of the particles, and set the length of the expanded channel section to the flight length. The thermal spray nozzle device according to claim 4, wherein the thermal spray nozzle device has a length equal to or longer than the distance.

However, the flight distance l _f is the particle flight time to t _f particles reach the solidification or semi-solidification, u _g is the gas flow rate, the density of [rho _g is the gas density of the [rho _s is the particle, d _s is Particle diameter, _ag is the speed of sound of gas The thermal spray nozzle device according to claim 1 or 2, wherein when the carrier gas inlet pressure is p _o and the nozzle outlet pressure is P _B , the inlet pressure p _o is introduced into the nozzle in a state satisfying the following formula.

Here, κ: specific heat ratio of compressed gas, M: Mach number in the nozzle enlarged portion downstream of the throat portion The thermal spray nozzle device according to any one of claims 1 to 6,
A carrier gas supply device that is connected to the nozzle via a conduit and introduces a carrier gas under pressure;
A sealed container containing a base material that collides the nozzle and emitted particles;
A thermal spraying apparatus comprising: a decompression means for decompressing the inside of the sealed container. The thermal spray nozzle device according to any one of claims 1 to 6,
A molten metal supply device that is connected to the reservoir through a connecting pipe and continuously pressurizes and supplies the molten metal to the molten metal in the reservoir;
A thermal spraying apparatus, comprising: a base material supply device that continuously supplies the base material.

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