KR100847131B1 - Method for manufacturing heat exchanger - Google Patents

Abstract

A method for manufacturing a heat exchanger using cold spray coating is provided to reduce the consumption of a filler metal, hardly cause problem due to a flux, and manufacture a heat exchanger without a flux by a brazing process although a vacuum brazing process is not employed. In a method for manufacturing a heat exchanger comprising a header, a tube(20), and fins(30), the method comprises coating a filler metal, an anti-corrosive, and a flux to be added if necessary on a surface of the tube by a cold spray coating process, contacting fins with the tube coated with the filler metal, the anti-corrosive, and the flux to be added if necessary, and brazing the coated tube with the fins, wherein a gas used in the cold spray coating process is nitrogen, helium, or a gas mixture thereof, the gas used in the cold spray coating process is preheated at a temperature of 300 to 600 deg.C before spraying the gas, and the gas used in the cold spray coating process has a pressure of 14 to 30 bars.

Description

Manufacturing method of heat exchanger using low temperature spray coating {METHOD FOR MANUFACTURING HEAT EXCHANGER}

1 is a schematic view showing the form of a heat exchanger,

2 is a schematic view showing the arrangement of each layer in the case of bonding fins in the conventional manner (a) to the tube of the heat exchanger and in the case of bonding the fins in the manner (b) according to the present invention;

3 is a conceptual diagram showing a low-temperature spray coating method applied in the present invention,

4 is a perspective view showing the shape of a tube of a heat exchanger,

Figure 5 is a photograph of the thickness of the coating layer of the tube surface used for brazing in the embodiment of the present invention by scanning electron microscope,

Figure 6 is a photograph observing the shape of the pin and the tube after brazing in the composition 1 of the embodiment of the present invention,

Figure 7 is a photograph observing the shape of the pin and the tube after brazing in the composition 2 of the embodiment of the present invention,

8 is a photograph observing the form of the pin and the tube after brazing in the composition 3 of the embodiment of the present invention,

9 is a photograph observing the form of the pin and the tube after brazing in the composition 4 of the embodiment of the present invention,

10 is a photograph of EPMA observation of a bonded cross section after brazing bonding under the condition of composition 1, and

FIG. 11 is a photograph of EPMA observation of a bonded cross section after brazing bonding under the condition of composition 2. FIG.

The present invention relates to a method for manufacturing a heat exchanger using a low temperature spray coating, and more particularly, it is possible to drastically reduce material consumption compared to a conventional method in which the material was consumed severely and the appearance of the manufactured heat exchanger product was poor. In addition, the present invention relates to a method of manufacturing a heat exchanger capable of manufacturing the heat exchanger in various ways even without using a flux.

Heat exchanger refers to a device that can quickly transfer a large amount of heat to or receive from the surroundings where it is necessary to transfer heat, such as a cooler or a heat pump. The heat exchange is carried out through a refrigerant or a fruit (hereinafter, simply a heat exchange medium). The heat exchange medium exchanges heat with another medium outside the tube while flowing inside the tube that becomes the heat exchange place. Heat exchange is usually achieved through a fluid such as air around the tube, where the contact area between the tube and the fluid is a major factor in determining heat exchange efficiency.

In order to increase the heat exchange area, a large number of small-diameter tubes are placed or the path of the tube is bent to form an S shape. However, even if such a method is used, the amount of heat exchange between the tube and the surrounding medium is greatly increased. Is difficult. Therefore, the method widely used in the heat exchanger is a fin 30 having excellent thermal conductivity on the surface of the tube 20 connected to the header 10 to receive the heat exchange medium as shown in FIG. 1 outside the tube. The heat exchange between the heat exchange medium / tube / fin / surrounding medium occurs. At this time, since the area of the fin is significantly larger than the area of the tube, the contact area between the fin and the surrounding medium is greatly increased, and therefore, the heat exchange efficiency can be improved.

At this time, the pin can not be formed integrally with the tube due to the complexity of the shape, it can only be manufactured by first manufacturing the tube and then bonding it to the tube, usually to bond the pin to the tube I am using the brazing method.

In other words, the method of joining a metal material can be classified into three types, namely, soldering, brazing, and welding. Welding is a method of melting and joining the material (base material) itself to be bonded when joining the two materials, the soldering and brazing is a method of using the filler metal at a lower temperature than the melting temperature of the base material. There is a difference in the method of joining, in which soldering is performed at a relatively low temperature and brazing is performed at a relatively high temperature.

Referring to the conventional method for attaching the fin to the surface of the heat exchanger tube using the brazing method as follows.

First, a process of coating Zn, an anticorrosive agent, on the surface of the tube is necessary. The Zn is to improve the corrosion resistance of the heat exchanger, and is coated on the surface of the tube (particularly, aluminum tube) through a wire-arc thermal spray coating process.

Apart from that, a step of pre-attaching the insert to the pin on the opposite side to be joined is required. In order to increase the adhesive force between the insert and the pin, the insert is placed on both sides of the pin material and then rolled to have a stacked shape in the form of insert / pin material / insert.

Thereafter, the step of applying the flux to the surface of the fin and tube is necessary. When the flux is brazed in the atmosphere, the flux serves to prevent the insert from being oxidized to reduce the wettability with the base material or to reduce the fluidity required for the insert to melt and flow down to the interface between the two base materials. Flux used for joining aluminum tube and fin is composed of NaCl, LiCl, KCl, etc. as a main component and corrosive flux containing LiF or Na ₃ AlF ₆ and KAlF ₄ , K ₃ AlF ₆ · 5H ₂ O, K ₂ Non-corrosive fluxes such as AlF ₆ , AlF ₃ and the like are exemplified. Typically, in a conventional brazing scheme such as nocolock brazing, the flux is usually diluted with water and applied with water. If the brazing bonding is performed in a vacuum, the flux applying step may be omitted.

Thereafter, after the fin and the tube are raised, the temperature is raised to melt the insert, and the insert is allowed to flow down at the interface between the two base materials. At this time, it is common to fix the tube to the header in advance and then perform brazing bonding between the pin and the tube.

Conventional fin and tube joining method as described above has a lot of room to improve in many respects.

In other words, it is pointed out that the clad metal in which the insert is clad in the fin material is used to bond the pin to the tube, but the interface used for the joining is limited to only one side of the pin, and the clad insert in the other part is wasted. have.

In addition, the flux is not only applied to the interface between the fin and the tube, but is also applied to the entire surface of the fin and the tube, so that the flux is excessively consumed, and the appearance is poor due to the flux that is not removed after brazing, When operated, the pieces of flux may be separated from the tube and the fins to cause dust generation. If the heat exchanger is used in an air conditioner or the like, the dust may cause ventilation resistance.

The vacuum brazing method has emerged as a method of not using the flux, but there is a disadvantage that the production speed is slow when the vacuum brazing method is used.

The present invention is to solve the problems of the prior art described above, according to one aspect of the present invention is provided a method of manufacturing a heat exchanger that reduces the amount of use of the insert and less problems caused by flux.

In addition, according to another aspect of the present invention, there is provided a method capable of manufacturing a heat exchanger by a brazing method without flux even without using a vacuum brazing method.

The heat exchanger manufacturing method for achieving the object of the present invention described above, in the manufacturing method of the heat exchanger heat exchange with the surroundings, including the header, tube and fins, when the tube and the fins are joined, inserted into the surface of the tube After the ash, the anticorrosive, and the flux added as needed, are coated by low temperature spraying, the materials are coated with the fins to contact the fins, and the braze joints between the tubes and the fins are applied.

At this time, the insert is preferably made of 3 to 12% by weight of Si, the remaining Al and other inevitable impurities.

In addition, the anticorrosive is preferably Zn.

In addition, the flux is a corrosive flux to which LiF or Na ₃ AlF ₆ is added to at least one of NaCl, LiCl, and KCl, or one selected from KAlF ₄ , K ₃ AlF ₆ · 5H ₂ O, K ₂ AlF ₆ , and AlF ₃ . It is preferable that it is above.

In addition, the low-temperature spray coating powder composed of the insert, the anticorrosive and the flux is effective to have a composition consisting of 10 to 35% by weight, flux: 0 to 7% by weight and the remaining insert.

In the above-described advantageous method for producing a heat exchanger of the present invention, it is more preferable to use nitrogen, helium or a mixture thereof for spraying the coating powder in the low temperature spray coating.

At this time, the gas used for spraying the coating powder in the low-temperature spray coating is preferably preheated at 300 ~ 600 ℃ before spraying.

In addition, the pressure of the gas used for spraying the coating powder in the low temperature spray coating may be 14 to 30 bar.

The heat exchanger manufacturing method of the present invention is characterized in that the coating powder containing the insert on the surface of the tube at a high temperature low-temperature spray bar coating the coating powder is easily attached to the tube having a very thin wall thickness is not deformed or damaged To avoid this, it is necessary to precisely control the pressure and temperature of the gas. In particular, when the gas is nitrogen and no flux is added in the coating powder, the pressure of the gas is more preferably -0.02 x gas preheating temperature (° C) + 30 bar or more.

Further, when the gas is nitrogen and flux is added in the coating powder, the pressure of the gas is more effective at -0.02 x gas preheating temperature (° C) +34 bar or more.

When the gas is helium and no flux is added in the coating powder, the gas pressure is -0.02 × gas preheating temperature (° C.) + 26 bar or more, and −0.02 × gas preheating temperature (° C.) + 34 bar or more. desirable.

Further, when the gas is helium and flux is added in the coating powder, the pressure of the gas is more preferably -0.02 × gas preheat temperature (° C.) + 30 bar or more and −0.02 × gas preheat temperature (° C.) + 36 bar or less. Do.

In addition, it is effective that the injection flow rate of the coating powder during the low temperature spray coating is 4 ~ 32g / min based on the mass flow rate.

In addition, the distance between the coating nozzle and the subject (tube) during the low temperature spray coating is preferably 10 ~ 50mm.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention coated the filler metal and the anticorrosive agent necessary for brazing on the surface of the tube and then, when brazing the fin and the tube, not only reduces the amount of the insert but also uses a strong bond without using a separate flux. The present invention has been made in view of the fact that heat exchanger parts having strength can be manufactured.

That is, as shown in Figure 2, rather than cladding the insert on both sides of the fin material, the amount of the insert attached to the non-contact surface is significantly reduced when attached to only one side of the tube. This is due to the fact that the surface area of the tube is very small compared to the surface area of the fin material and adheres only to one side of the tube. However, unlike the fin material, it is preferable to coat the tube because it cannot be clad in a manner of rolling after attaching the insert. In this case, since the insert to be coated is a metal material, it is difficult to obtain a coating layer having a strong bonding force on the surface of the tube by a conventional method, and cold spray coating of the metal powder is preferable.

It is advantageous to simplify the process by coating by spraying the insert powder and the anticorrosive at the time of the coating. That is, in the past, the anticorrosive was coated on the surface of the tube by a wire arc spray coating method and then used for brazing bonding of the fin and the tube. However, in the present invention, the heat exchanger is manufactured in a much simpler process by spraying the insert and the anticorrosive together. It can manufacture.

The insert may be a low melting point metal that can be easily bonded to the base material according to the type of the base material, and in the case of using aluminum or an alloy thereof, which is commonly used as a heat exchanger material, as a material for tubes and fins, Al-Si It is preferable to use an alloy as an insert. The Al-Si alloy is not particularly limited as long as it is an alloy for inserts that are commonly used, but the representative composition may include 3-12 wt% of Si, the remaining Al and other inevitable impurities. In addition to the above composition, it may have a composition in which a small amount of Mg, Bi or the like is contained.

It is preferable to coat the anticorrosive together with the insert to improve the corrosion resistance of the bonding surface. The anticorrosive agent is used to prevent oxidation of the insert by first oxidizing itself, and it is preferable to use Zn having a strong ionization tendency.

In addition, in a conventional brazing method such as the Nocolok brazing method performed in the air, when the pin with the insert cladding and the tube coated with the anticorrosive are conventionally bonded, the molten insert can sufficiently flow into the joint portion. While it is necessary to use flux to prevent the oxidation of the molten insert, in order to secure the fluidity of the insert, it is not necessary to use the flux in particular when using the method of the present invention. That is, in the case of using the conventional method, since the clad insert has to sufficiently flow down to the joint interface between the tube and the pin to secure the bonding strength, there is a possibility that the insert is oxidized in contact with the atmosphere while the insert is flowing. According to the tube, since the insert is already coated on the surface of the tube, it is not necessary to ensure fluidity because it is only required to join the fin to the tube after melting the pin in contact with the fin after contacting the fin. This is because some degree of confidentiality can be secured in itself.

Therefore, in the present invention, even if only the insert and the anticorrosive coating on the surface of the tube by the low-temperature injection method can achieve a sufficient effect. However, it is not necessary to ensure the fluidity of the insert at all, and if the oxidation degree of the insert is severe, the brazing strength may decrease, so that the flux may be sprayed together if necessary.

Flux also does not limit the kind as long as it is a conventional brazing flux. Typical brazing fluxes include corrosive fluxes containing LiF or Na ₃ AlF ₆ in at least one of NaCl, LiCl, and KCl, as described above, and KAlF ₄ , K ₃ AlF ₆ · 5H ₂ O, K ₂ AlF ₆ And non-corrosive fluxes such as AlF ₃ and the like.

Therefore, in the method of manufacturing the heat exchanger of the present invention, after coating the insert, the anticorrosive agent, and the flux added as needed on the surface of the tube by cold spraying, the fins are brought into contact with the surface of the tubule coated with the above materials to braze the tube and the fin. It is characterized by bonding.

At this time, the addition ratio of the insert, the anticorrosive agent, and the flux added as necessary, and the low temperature spraying conditions are more preferable to follow the unique conditions of the present invention will be described below.

Cold spray coating as used in the present invention means one of the spraying methods commonly used in the art as a low temperature that does not melt the coating material in the powder form through the spray device of the type shown in FIG. Means spraying on. Looking at the low-temperature spraying process through Figure 3 as follows. As shown in FIG. 3, the low temperature spray coating machine includes a gas supply device, a control panel, a gas heating device, a powder supply device, and a de Laval nozzle. The gas supplied from the gas supply device is controlled by the amount of gas in the control panel, and divided into a gas heating device and a powder supply device. The gas heating device heats the gas to a high temperature to induce a speed increase due to the expansion of the gas, and the powder feeding device supplies the powder to the gas supplied from the control panel so that the powder is moved toward the nozzle (de Laval nozzle) by the gas. It serves to be supplied. Immediately after the powder feeding device, a powder heating device for heating the powder may be provided. The powder heating device is a device for heating the powder by mounting a heating element on the outside of the tube through which the powder passes, and serves to increase the temperature of the powder to increase the deformation and toughness of the powder when the powder collides with the subject. Immediately before the de Laval nozzle, a mixture of the powder and gas supplied from the powder feeder and the heated high-speed gas supplied from the gas heater meet to form a high-speed gas / powder mixture to form a high-speed gas through the DeLaval nozzle. Sprayed by powder jets. DeLaval nozzle is a nozzle that is used to increase the speed of the gas to the supersonic speed above the speed of sound as it has a form that the inner diameter of the nozzle is reduced (converge) and then diverged again when viewed in the nozzle length direction. The powder transported by the gas injected at supersonic speed through the de Laval nozzle collides with the subject at a high speed close to the velocity of the gas, and the kinetic energy of the powder is converted into the energy required for the coupling between the subject / powder. Thus, a powder-coated subject can be obtained.

In addition, the method of coating the powder using the low temperature spraying method is not particularly limited, but spraying using the following spraying conditions may yield better results.

Particle size of powder used

The particle size of the insert, the anticorrosive agent and the flux (hereinafter, referred to as the coating powder) is not particularly limited as long as it can be accelerated at a sufficient rate, but most preferably 1 to 45 μm. The particle size range is a range necessary to obtain an acceleration effect while having sufficient kinetic energy during low temperature spraying.

Composition of coating powder

The coating powder may be composed of an insert and an anticorrosive or an insert, an anticorrosive and a flux as described above. The composition of the coating powder is preferably a composition consisting of anticorrosive: 10 to 35% by weight, flux: 0 to 7% by weight and the remaining inserts. When the content of the anticorrosive is excessively high, it is not preferable because the relative specific gravity of the insert is reduced, and on the contrary, when too little is added, it is difficult to achieve the effect of improving corrosion resistance. In addition, the flux can be added up to 7% in order to prevent oxidation and ensure fluidity, and can be used without any flux at all.

Type of gas

At this time, the gas used is not particularly limited, but helium, nitrogen or a mixed gas thereof is more preferably used.

Gas pressure

The gas pressure just before the nozzle at the time of injection is preferably 14-30 bar. When the pressure of the gas is low, the speed of the powder particles to be coated is sufficient, so that a coating layer is hardly formed on the object. The higher the gas pressure, the higher the particle velocity, but there is a limit there, and if the pressure is further increased, the device may be loaded, so the upper limit of the gas pressure is set in the above range.

Flow rate of coating powder (inserts, anticorrosive and flux as required)

The flow rate of the coating powder is preferably in the range of 4 to 32 g / min based on the mass flow rate. If the coating powder mass flow rate is less than 4 g / min, it is difficult to control the coating powder flow rate when feeding the powder. On the contrary, when the coating powder mass flow rate exceeds 32 g / min, the coating powder flow rate is excessively increased compared to the gas to speed up each particle. Is reduced and is not appropriate because the device is overloaded to match the particle velocity.

Distance between nozzle and subject (tube)

The spacing between the nozzle and the subject (tube) is a major factor that allows the particles to be smoothly coated. When coating the coating powder consisting of a brazing insert, an anticorrosive agent, and a flux added as necessary in the present invention, the nozzle tip is applied. It is desirable to make the distance between the object and the subject 10-50 mm. If the distance exceeds 50 mm, the distance from the nozzle to the powder to reach the subject is too far to increase the speed reduction of the coated particles, resulting in a failure to reach the subject at a sufficient speed, resulting in a reduction in the lamination rate. do. On the contrary, when less than 10 mm, nozzle clogging may occur due to the backflow of gas.

Gas heating temperature

It is preferable that the temperature of the gas heated by the gas heating apparatus at the said low temperature spraying is 300-600 degreeC. When the gas is injected from the DeLaval nozzle, the gas is adiabatic and expands due to the shape of the dividing portion of the nozzle diameter, which is changed into a gas jet having a high velocity. By this, a sufficient gas velocity can be secured. In order to ensure a sufficient gas velocity, the higher the temperature of the gas is, the better, and therefore, there is no need to specifically set the upper temperature limit of the gas in this respect. However, when the temperature of the gas is high, the load on the device is high, so in the apparatus currently used in general, it is preferable to set the temperature to about 600 ° C as the upper limit.

Relationship between gas pressure and heating temperature

In the low temperature spray coating process, even when spraying under the same pressure and temperature conditions, it is common to use helium rather than nitrogen as a carrier gas, and the flying speed of the sprayed particles is higher. This is because the specific gravity of helium is smaller than that of nitrogen. As a result, when the object to be coated is impacted, the particle efficiency accelerated by helium collides with a higher collision energy (kinetic energy) than the particle accelerated by nitrogen, so the lamination efficiency when using helium is used when nitrogen is used. Higher than However, aluminum tubes, which are widely used as materials for heat exchangers, have a shape as shown in FIG. 4, and the thickness of the walls is only about 350 μm, so that the shape of the tubes may be deformed when the particles are accelerated at too high a speed. Can be. Therefore, it may be problematic to accelerate the particles at too fast speeds, so it is desirable to separately define the acceleration capacity of the particles for helium gas and nitrogen gas for which the particle acceleration ability is relatively high. In addition, since the acceleration capacity of the particles depends on the gas pressure and the preheating temperature of the gas just before the nozzle, the acceleration of the particles and the preheating temperature must be limited together to control the acceleration capacity of the particles to an appropriate range.

When using nitrogen gas, the aluminum tube is not deformed due to the accelerated particles within the above gas pressure and preheating temperature range. However, if the pressure or preheating temperature of the gas is too low, the lamination efficiency of the particles is reduced, so if the gas pressure is low, it is necessary to preheat the gas to a sufficient temperature to increase the adiabatic expansion effect. Therefore, the pressure of the gas and the preheating temperature preferably have the relationship of the following Equation 1.

Gas pressure (bar) ≥ -0.02 × gas preheating temperature (℃) + 30 (without flux added to the coating powder)

That is, Equation 1 means that the gas pressure should be increased as the gas preheating temperature is lowered. In addition, Equation 1 shows a gas pressure when no flux is added, and when the flux is added, the gas pressure should be further increased. In other words, the flux has a low density compared to the metallic insert and the anticorrosive agent to have a low acceleration effect, and the coating needs to be accelerated at a relatively high speed because the coating efficiency is lower than that of the metal. The relationship between pressure and temperature when the flux is added and coated in a nitrogen environment may be expressed by the following Equation 2.

Gas pressure (bar) ≥ -0.02 × gas preheating temperature (℃) + 34 (if flux is added to the coating powder)

Unlike nitrogen gas, helium needs to limit not only the lower limit but also the upper limit, because the gas has a high acceleration capacity. The helium gas pressure when no flux is added is defined by the following equation.

-0.02 × gas preheating temperature (℃) + 26 ≤ gas pressure (bar) ≤ -0.02 × gas preheating temperature (℃) + 34

In addition, the helium gas pressure at the time of adding a flux needs to be limited to following formula (4).

-0.02 × gas preheating temperature (℃) + 30 ≤ gas pressure (bar) ≤ -0.02 × gas preheating temperature (℃) + 36

Thickness of coating layer

Coating layer thickness for brazing is preferably 30 ~ 150㎛. In other words, if the thickness is not sufficient, the insert, anticorrosive and flux for brazing cannot be sufficiently included to obtain the brazing effect. On the contrary, if the thickness is too thick, the powder consumption is increased and the anticorrosive such as Zn of the coating layer is formed. The coating layer thickness for brazing is limited to the above range because the amount of diffusion to the fins increases, causing a reduction in the thickness of the fins and erosion, and eventually the fins can be melted by compositional liquefaction.

Brazing is performed after the low temperature spray coating step described above, and the brazing method is not particularly limited. It is because those skilled in the art can appropriately select the types and conditions of ordinary brazing and apply them to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, it is necessary to note that the following examples are not intended to limit the scope of the present invention, but are merely illustrative of the present invention described in order to help the understanding of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and the matters reasonably inferred therefrom.

(Example)

Preparation of Coating Powder

It was prepared by mixing the coating powder in the mixing ratio (meaning the weight ratio) shown in Table 1 below. The insert described in Table 1 had an Al-12 wt% Si alloy component, Zn was used as the anticorrosive, and KAlF ₄ was used as the flux. In addition, the insert had a particle size in the range of 10 to 45 μm, the Zn anticorrosive powder was 1 to 10 μm, and the KAlF ₄ flux was 6 to 12 μm.

division Insert Anticorrosive Flux Composition 1 70 30 0 Composition 2 80 13 7 Composition 3 70 25 5 Composition 4 60 34 6

Low temperature spray coating

The coating powder of each composition shown in Table 1 was subjected to low temperature spray coating using nitrogen gas as a carrier gas. The distance between the nozzle and the substrate was maintained at 30 mm during coating, and the coating was performed while moving the nozzle at a speed of 10 mm / s. In addition, while applying the pressure of nitrogen gas to 21, 25, 29 bar was confirmed the results in each case. Table 2 shows the lamination efficiency of the coating powder when coated under the respective conditions.

division Gas preheating temperature (℃) Lamination Efficiency (%) 21 bar 25 bar 29 bar Composition 1 400 15 28 39 500 27 41 55 Composition 2 400 9 13 18 500 18 20 26 Composition 3 400 11 15 22 500 15 19 30 Composition 4 400 10 14 20 500 16 22 32

As can be seen from Table 1, the composition 1 shows the case where the flux is not added, and the composition 2 to the composition 4 show the case where the flux is added. When the flux is not used, the equation 1 representing the lower pressure limit for nitrogen gas is applied to calculate 22 bar at 400 ° C and 20 bar at 500 ° C. In addition, in the case of using the flux, applying equation (2), which represents the lower pressure limit for nitrogen gas, 26 bar at 400 ° C and 24 bar at 500 ° C are calculated.

As can be seen from the results of Table 2, in the case of the composition 1 without using the flux, the lamination efficiency is not preferable as it is only 15% when the coating is performed at 21 bar lower than the pressure lower limit of 400 ° C. defined by Equation 1. . However, when the pressure was higher than the lower limit, excellent lamination efficiency of more than 20% was obtained at both 400 ° C and 500 ° C.

In addition, when flux is used (composition 2, composition 3, composition 4) of 21 bar lower than the lower pressure limit of 400 ℃ and 21 bar lower than the lower pressure limit of 500 ℃ and when the desired conditions of the present invention is not satisfied All showed unsatisfactory values of lamination efficiency of less than 20%. However, when low-temperature spray coating was carried out at a pressure higher than the lower pressure limit according to Equation 2, all showed excellent lamination efficiency of 20% or more.

Therefore, the effect of the low temperature spraying conditions used in the heat exchanger manufacturing method of the present invention was confirmed.

Perform brazing joint

After assembling the aluminum tube coated with Example 2 to the header, the pin was contacted with the insert is not attached to the surface of the tube was subjected to a rock collocated brazing to prepare a heat exchanger. The thickness of the coating layer on the surface of the tube used for brazing before brazing was slightly different depending on the position, but it could be confirmed from the scanning electron microscope (SEM) observation result of FIG. In Figure 5 (a) is a composition 1 coated at a gas preheating temperature of 500 ℃, (b) is a composition 3 coated at a gas preheating temperature of 500 ℃, (c) is a composition 3 at a gas preheating temperature of 500 ℃ In the case of coating, and (d) shows the case in which composition 4 was coated at a gas preheating temperature of 500 ° C.

Thereafter, the brazing was completed by maintaining the temperature in the brazing furnace at 620 ° C. for 20 minutes in a nitrogen atmosphere. After brazing, the photographs observing the pin and the tube bonded form are shown in FIGS. 6 (composition 1), 7 (composition 2), FIG. 8 (composition 3) and FIG. 9 (composition 4). 6, 7, 8 and 9 also show the results when the gas preheating temperature at 500 ℃ coating.

After the brazing, the joints were examined for histological examination, observing the joint surface, observing the insertion material and the corrosion inhibitor distribution. Scanning histology and splicing observation were performed by scanning electron microscopy, and the insertion and corrosion distribution were analyzed by Electron Probe X-ray Micro Analyzer (EPMA).

10 and 11 show the results. In each figure, the upper left is a photograph of the analysis plane, the upper right is a surface analysis of the Zn distribution, the lower left is a surface analysis of the aluminum distribution, and the lower right is a surface analysis of the silicon distribution. As shown in FIG. 10 which shows the result for the composition 1 (gas preheating temperature 500 degreeC) which is the condition which does not add the flux, and FIG. While Zn, which is an anticorrosive agent, has a form diffused inward from the surface of the tube coating layer, it can be seen that silicon is clustered all over the tube, and since Zn is concentrated in the joint surface, it is effective for improving corrosion resistance. In addition, it was judged that the conventional Zn layer was able to exhibit the same corrosion resistance as the case of coating separately.

In addition, as can be seen from the bonding surface observation results, it can be seen that the aluminum tube and the fin form a wide bead width on both sides of the bonding surface. Therefore, it is judged to exhibit excellent characteristics in terms of heat dissipation performance, corrosion resistance, and bonding strength, and according to the present invention, it was confirmed that the composition 1 without the flux was also able to show excellent results.

Therefore, the effect of the present invention was confirmed, and in particular, even when a coating powder having a composition of composition 1 without using any flux was coated on the tube surface, it was confirmed that a heat exchanger having a good joint could be manufactured.

According to the present invention, it is possible not only to provide a method for manufacturing a heat exchanger which reduces the amount of inserts and causes less trouble due to flux, and also manufactures a heat exchanger by brazing without using a flux even without using a vacuum brazing method. It can provide a way to do it.

Claims (14)

In the method of manufacturing a heat exchanger, including a header, tube and fin to heat exchange with the surroundings, When joining the tube and the fin, the surface of the tube is coated with the insert, the anticorrosive and the flux, if necessary, by cold spraying, and then the insert, the anticorrosive and the flux, if necessary, are coated. A manufacturing method of brazing a tube and a pin by contacting the pin with the tube, The gas used for injection in the low temperature spray coating is nitrogen, helium or a mixture of these, The gas used for injection in the low temperature spray coating is preheated at 300 ~ 600 ℃ before injection, The pressure of the gas used for injection in the low temperature spray coating is a method of producing a heat exchanger, characterized in that 14 ~ 30 bar. The method of claim 1, wherein the insert is made of Si: 3 to 12% by weight, the remaining Al, and other inevitable impurities. The method of claim 1, wherein the anticorrosive is Zn. The method of claim 1, wherein the flux is corrosive flux in which LiF or Na ₃ AlF ₆ is added to at least one of NaCl, LiCl, and KCl, or KAlF ₄ , K ₃ AlF ₆ .5H ₂ O, K ₂ AlF ₆ , AlF ₃ Method for producing a heat exchanger, characterized in that at least one selected from. According to claim 1, wherein the low-temperature spray coating powder comprising the insert, anticorrosive and flux has a composition consisting of 10 to 35% by weight, flux: 0 to 7% by weight and the remaining inserts. Method of manufacturing heat exchanger. delete delete delete The method of manufacturing a heat exchanger according to claim 1, wherein when the gas is nitrogen and no flux is added in the coating powder, the pressure of the gas is -0.02 x gas preheating temperature (° C) +30 bar or more. The method of manufacturing a heat exchanger according to claim 1, wherein when the gas is nitrogen and flux is added in the coating powder, the pressure of the gas is -0.02 x gas preheating temperature (° C) +34 bar or more. The gas preheating temperature according to claim 1, wherein when the gas is helium and no flux is added in the coating powder, the pressure of the gas is -0.02 × gas preheating temperature (° C.) + 26 bar or more, −0.02 × gas preheating temperature (° C.) + 34 A method for producing a heat exchanger, characterized in that the bar or less. The gas pressure is -0.02 x gas preheating temperature (° C) +30 bar or more, -0.02 x gas preheating temperature (° C) +36 bar when the gas is helium and flux is added in the coating powder. The manufacturing method of the heat exchanger characterized by the following. The method of manufacturing a heat exchanger according to any one of claims 1 to 5, wherein the injection flow rate of the coating powder during the low temperature spray coating is 4 to 32 g / min based on the mass flow rate. The method according to any one of claims 1 to 5, wherein the distance between the coating nozzle and the subject (tube) during the low temperature spray coating is 10 to 50 mm.

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