JP5619538B2 - Fluxless brazing method of heat exchanger having narrow channel inner fin and aluminum clad material used therefor - Google Patents

Description

  The present invention relates to a method of brazing a heat exchanger having an aluminum narrow channel inner fin that can be brazed without using a flux in a non-oxidizing atmosphere. In particular, a method for brazing an inner fin to be brazed so that the inner fin has a large number of narrow flow paths and the flow path pitch is extremely small, and the flow path is not short-circuited by a braze fillet, and aluminum used therefor It relates to a clad material.

Aluminum heat exchangers and radiators are brazed in a flux furnace using non-corrosive fluoride-based flux, or brazing material added with about 0.5 to 1.5% Mg is used. And brazed in a vacuum furnace.
When using a flux, the flux powder is applied to the surface of a heat exchanger part via a binder, dried, and heat brazed in a non-oxidizing atmosphere such as a nitrogen gas atmosphere. This flux requires a cost in the coating process. Further, a part of the flux evaporates and adheres to and accumulates on the inner wall of the furnace, which requires cost for maintenance of the furnace. For this reason, brazing using flux has a drawback that the strength and strength of the material cannot be increased because of the limitation on the amount and amount of Mg added.

  Vacuum brazing enables brazing by evaporating Mg in the brazing material and destroying the oxide film on the surface of the aluminum material. However, the vacuum furnace is an expensive facility and has a disadvantage that its control is troublesome.

  In order to solve the above problems, various types of fluxless brazing under atmospheric pressure have been proposed. In Patent Document 1 below, flux-less brazing is performed under atmospheric pressure in a non-oxidizing atmosphere by containing Mg in a brazing target member and covering the brazing target. However, this method has a drawback of requiring a covering.

  In Patent Document 2, a brazing target member is covered in a furnace by a windbreak jig (cover) to improve the temperature rising rate. This method has the disadvantage of cost and labor.

  Patent Document 3 proposes fluxless brazing on the inner surface side of the tube in an inert atmosphere and atmospheric pressure by adding Mg to the brazing material of the clad material.

  In Patent Document 4, an antioxidant layer is clad on the surface of a brazing material to enable brazing in an air atmosphere.

  In Patent Document 5, a brazing material made of an Al—Si—Mg-based alloy is clad on the surface of a core material, and the surface of the material is acid-washed before brazing so that the thickness of the oxide film is 20 mm or less. Inside, fluxless brazing.

JP-A-9-85433 JP 2006-175500 A Japanese Patent No. 4037477 Japanese Patent No. 3701847 Japanese Patent Laid-Open No. 10-180489

However, in Patent Document 3 of fluxless, only the inner surface side of the tube is fluxless, and there is a drawback in that flux is used to join the tube outer surface and the fin.
Similarly, Patent Document 4 of fluxless requires a clad material having an anti-oxidation layer on the surface of the brazing material, which increases the material cost.
Further, in Patent Document 5 of fluxless, acid cleaning is complicated and the cost increases.
Further, according to experiments, when the fluxless brazing is applied to a heat exchanger having a narrow flow path having an inner fin flow path width of 1 mm and a flow path depth of 1 mm, the braze fillet is short-circuited in the flow path. As a result, it has been found that cooling water may not be able to flow inside.

  In order to solve such a problem, the present inventors have already applied for a patent on a fluxless brazing method for aluminum material and an aluminum clad material for fluxless brazing as of April 17, 2009 (Japanese Patent Application). 2009-101326, unpublished). The present inventors further experiment and examine whether or not this brazing method can be applied to a heat exchanger having a narrow channel inner fin with a remarkably small channel, and complete the present invention.

  In order to achieve the above object, the present inventors have set the amount of Mg added to the brazing filler metal in an appropriate range and the size of the Si particles in the brazing filler metal within a certain range, so that the inner diameter of the narrow channel can be reduced. The present invention was applicable to a heat exchanger having fins, and found that a good brazing state was obtained in a non-oxidizing atmosphere without depressurization, and that the narrow channel was hardly clogged by a filler fillet.

That is, the fluxless brazing method of the heat exchanger having the narrow channel inner fin according to the first aspect of the present invention is an Al- containing, by mass%, 0.1 to 5.0% Mg and 3 to 13% Si. A brazing method of a heat exchanger having a narrow channel inner fin using an aluminum clad material in which an Si-based brazing material is located on the outermost surface,
Si particles contained in the Al—Si brazing material have an equivalent circle diameter of 0.8 μm or more, and the number of particles having a diameter of 1.75 μm or more is 25% or more, which is accompanied by decompression. In a non-oxidizing atmosphere, the Al-Si brazing material and the brazing target member are brought into close contact with each other,
The aluminum clad material and the brazing target member are joined at a heating temperature of 559 to 620 ° C.

  A fluxless brazing method for a heat exchanger having a narrow channel inner fin according to the second aspect of the present invention is the method according to the first aspect of the present invention, wherein the aluminum clad material and at least the surface of the contact adhesion portion of the brazing target member are used. The surface roughness is Ra 0.3 μm or less.

  A fluxless brazing method for a heat exchanger having a narrow channel inner fin according to the third aspect of the present invention is the above-described first or second aspect, wherein the Al-Si brazing material is 0.01% by mass. It contains 1.0% Bi.

  A fluxless brazing method for a heat exchanger having narrow channel inner fins according to a fourth aspect of the present invention is the core according to any one of the first to third aspects, wherein the Al-Si brazing material is clad. The material is characterized by containing Si: 0.1 to 1.2%, Mg: 0.01 to 2.0% by mass%, and having a composition composed of the balance Al and inevitable impurities.

  According to a fifth aspect of the present invention, there is provided a fluxless brazing method for a heat exchanger having a narrow channel inner fin according to any one of the first to third aspects of the present invention, wherein the Al-Si brazing material is clad. Material is mass%, Mn: 0.2-2.5%, Cu: 0.05-1.0%, Si: 0.1-1.2%, Fe: 0.1-1.0% The fluxless brazing method for an aluminum material according to any one of claims 1 to 4, wherein the aluminum material has a composition comprising the balance Al and inevitable impurities.

  A fluxless brazing method for a heat exchanger having narrow channel inner fins according to a sixth aspect of the present invention is the core according to any one of the first to third aspects, wherein the Al-Si brazing material is clad. The material contains, in mass%, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, Mn: 0.2 to 2.5%, Cu: 0.05 to It contains one or more of 1.0% and Fe: 0.1 to 1.0%, and has a composition comprising the balance Al and inevitable impurities.

  A fluxless brazing method for a heat exchanger having a narrow channel inner fin according to a seventh aspect of the present invention is the core in which the Al-Si brazing material is clad in any of the first to third aspects of the present invention. The material contains, in mass%, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, Fe: contains one or more of 0.1 to 1.0%, Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, It contains one or more of Cr: 0.01 to 0.5% and Bi: 0.01 to 1.0%, and has a composition composed of the balance Al and inevitable impurities.

  The aluminum clad material for fluxless brazing of a heat exchanger having narrow channel inner fins according to the eighth aspect of the present invention is an Al-Si based brazing material according to any one of the first to third aspects of the present invention. And the Al—Si brazing material is located on the outermost surface and is used for fluxless brazing in a non-oxidizing atmosphere without depressurization.

  The aluminum clad material for fluxless brazing of a heat exchanger having narrow channel inner fins according to the ninth aspect of the present invention is the eighth aspect of the present invention, wherein the core material is any one of the fourth to seventh aspects of the present invention. It has the composition described.

  Below, the reason for limitation of the component etc. which are prescribed | regulated by this invention is demonstrated below. In addition, each component amount is shown by mass%.

1. Brazing material In the aluminum clad material used in the present invention, a brazing material based on an Al-Si alloy and added with Mg is used.

  Although content of Si is not specifically limited, About 3 to 13% generally used as a brazing material is suitable, and 6 to 12% is more suitable. If it is less than 6%, the amount of liquid phase at the time of brazing tends to be insufficient, and if it exceeds 12%, it becomes a hypereutectic Si region of an Al—Si based alloy, and the workability at the time of producing an aluminum plate tends to deteriorate. Because.

  The content of Mg is preferably 0.1 to 5.0%. If it is less than 0.1%, the effect of the present invention, which is the effect of the present invention, cannot be obtained by the effect of preventing reoxidation of the joint surface at the time of brazing. Saturates and causes difficulty in workability of the aluminum material. In the present invention, brazing properties can be secured only by the oxide film destruction activity in the above Mg component range, but further, the Mg content is optimized and the effect of lowering the solidus temperature of the Al—Si—Mg brazing material is utilized. If this is the case, excellent brazing properties can be exhibited.

  The optimum Mg content in this case varies depending on the Si content. For example, when the Si content is 6 to 12%, the Mg content is preferably 0.75 to 1.5%. If it is this range, the melting | fusing point fall of a solder | brazing | wax will fully be acquired, and it becomes possible to obtain a more favorable brazing property by the synergistic effect with the getter action by Mg. Specifically, brazing can be performed at the lowest solidus temperature of 559 ° C. or higher with an Al—Si—Mg alloy.

The brazing material can contain Zn as appropriate for the purpose of improving the corrosion resistance of the product. This component can be contained at a content of 0.1 to 5.0, for example. Further, in order to obtain a bond in the present invention, Bi is not essential, but by incorporating Bi, the wettability of the brazing material can be further improved.
The Bi content is preferably 0.01 to 1.0%. If it is less than 0.01%, the effect is not sufficient, and if it exceeds 1.0%, the effect is saturated and the material cost is increased.

Furthermore, in the present invention, relatively coarse Si particles are present on the surface of the brazing material. Usually, a dense oxide film such as Al ₂ O ₃ is present on the surface of the aluminum material, and this further grows to become a thick film in the brazing heat treatment process. The general view is that the greater the thickness of the oxide film, the stronger the tendency to inhibit the destruction of the oxide film. In the present invention, since coarse Si particles are present on the surface of the brazing material, a dense oxide film of aluminum does not grow on the surface of the coarse Si particles, and this site works as an oxide film defect on the surface of the aluminum material. That is, even if the oxide film on the surface of the aluminum material becomes thick during the brazing heat treatment, the brazing material oozes out from the Si particle portion, and the oxide film destruction action proceeds from this site. Conceivable. The term “Si particles” as used herein includes Si particles due to the composition of Si as a single component, and also includes, for example, Fe—Si compounds and Al—Fe—Si intermetallic compounds mainly composed of Fe—Si. Shall be. In the description of the present invention, these are referred to as Si particles for convenience.

Specifically, when the Si particles on the surface of the brazing material are regarded as equivalent circle diameters and the number of Si particles of 0.8 μm or more is counted and 25% or more of those having 1.75 μm or more are present, this effect is sufficiently obtained. It is done. Although the density of the Si particles is not mentioned in the present invention, the number of Si particles of 0.8 μm or more in the 10000 μm ² field of view is several tens depending on the alloy composition used in the present invention, the manufacturing condition range, and the finished plate thickness of the material. In the present invention, if the number of particles having a diameter of 1.75 μm or more is 25% or more, the effect is obtained. After confirming that it was obtained, it was set as the above definition.

Further, it has been clarified that the coarse Si particles on the surface of the brazing material hardly cause clogging of the inner fin of the heat exchanger having the narrow flow path inner fin. This is presumed to be due to the following reason.
As an example, in an inner fin in which a large number of narrow flow channels having a groove width and a groove height of 1 mm are arranged in parallel, if the flowability of the molten brazing material is too high, the brazing material flows into the flow channel, and the flow path is formed by the braze fillet. It will be blocked. In the present invention, the presence of the coarse Si particles in a predetermined amount or more suppresses the flowability of the brazing material, prevents the brazing material from flowing out into a small flow path, and suppresses clogging. This is because the melting temperature of coarse Si particles (1410 ° C) is higher than the melting temperature of aluminum (660 ° C), so some of the coarse Si particles do not melt at the initial stage of melting of the brazing material (semi-molten state) This is because it inhibits the wax flow and lowers its fluidity. Thereby, clogging of the narrow channel hardly occurs.

2. Core material The core material composition of the aluminum clad material used in the present invention is not particularly limited in obtaining a bond, but by realizing fluxless brazing, Mg addition aiming at high strength is actively added. Yes.
As a core component, what contains Si: 0.1-1.2% and Mg: 0.01-2.0% by mass ratio, and the remainder consists of Al and an unavoidable impurity are shown.
Moreover, by mass ratio, Mn: 0.2-2.5%, Cu: 0.05-1.0%, Si: 0.1-1.2%, Fe: 0.1-1.0%, Containing the balance Al and inevitable impurities.
As the core material component, one or more of Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, and Fe: 0.1 to 1.0% are contained. If desired, Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Bi: 0.01 to 1.0% One or two or more types are contained, and the balance is composed of Al and inevitable impurities. The action of each element and the reasons for limitation are as follows.

Si: 0.1-1.2%
In addition to improving the material strength by dissolving Si in a matrix with a simple substance of Si, in the present invention, the material strength is improved by precipitation of Mg ₂ Si obtained by a synergistic effect with the positive addition of Mg. This hardening by Mg ₂ Si precipitation contributes to a dramatic improvement in material strength by aging precipitation after brazing heat treatment. In an alloy design based on the conventional A3003 alloy or the like, it is dispersed as an Al—Mn—Si compound to improve the material strength. If the amount is less than the lower limit, the effect is insufficient. If the upper limit is exceeded, the melting point decreases and the core material melts, so the above range is desirable. In addition, the more preferable range of Si content is 0.3 to 1.0%. When positive inclusion of Si is not required due to inclusion of Mn or the like, it is allowed to contain less than 0.1% of Si as an impurity.

Mg: 0.01-2.0%
When Mg is added simultaneously with Si, it precipitates as a fine intermetallic compound Mg ₂ Si after brazing and has the effect of significantly improving strength by age hardening. Moreover, it reacts with Si diffused from the brazing material during the brazing heat and has the same strength effect. Further, a part of it diffuses into the brazing material and contributes to the oxide film destruction and the oxide film growth suppressing action on the brazing material surface. Below the lower limit, the effect is insufficient, and when the upper limit is exceeded, the melting point decreases and the core material melts. For this reason, the above range is desirable for the Mg content.

Mn: 0.2 to 2.5%
Mn crystallizes or precipitates as an intermetallic compound, and improves the strength after brazing. In addition, the corrosion resistance is improved by making the potential of the core material noble. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, workability such as rolling deteriorates. In addition, further effects cannot be obtained. For these reasons, the Mn content is preferably within the above range. In addition, the more preferable range of Mn content is 0.5 to 1.5%.

Cu: 0.05 to 1.0%
Cu is dissolved to improve the strength after brazing and to improve the corrosion resistance by making the potential of the core material noble. Below the lower limit, the effect is insufficient, and when the upper limit is exceeded, the melting point decreases and the core material melts. For this reason, the above range is desirable for the Cu content. In addition, the more preferable range of Cu content is 0.1 to 0.7%.

Fe: 0.1 to 1.0%
Fe crystallizes or precipitates as an intermetallic compound, and improves the strength after brazing. It also promotes recrystallization during final annealing and brazing. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, the corrosion rate becomes too fast. Further, the crystal grain size after the final annealing becomes too fine, and the erosion of the wax becomes remarkably large at the portion where the processing is not introduced at the time of molding. For these reasons, the above range is desirable for the Fe content. In addition, the more preferable range of Fe content is 0.2 to 0.5%.

Zr, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%
Zr, Ti or Cr is dispersed as a fine intermetallic compound after brazing to improve the strength. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, the workability decreases. Therefore, the content of these components is preferably in the above range.

Bi: 0.01 to 1.0%
Bi suppresses re-oxidation of the material surface and improves the wetting and spreading property of the brazing material. If it is less than the lower limit, the effect is insufficient, and even if the upper limit is exceeded, no further effect can be obtained. For this reason, the above range is desirable for the Bi content.

3. Clad material In the clad material used in the present invention, it is sufficient that the Al-Si brazing material is clad on at least one side, and one side and a double sided clad material can be properly used. In the double-sided clad material, the both sides of the core material may be clad with a brazing material, the brazing material is clad on one side, and other materials such as a sacrificial material are clad on the other side. It may be a thing.

4). Material of brazing target member Any commonly used aluminum alloy can be used as the brazing constituent member other than the brazing material without any problem.

5. Surface roughness of the brazing member In carrying out the present invention, it is difficult to supply oxygen from the outside to the contact adhesion portion which is the junction portion by increasing the contact adhesion state of the junction portion. Increases the ability to suppress oxidation of the material surface. The oxygen supply here does not mean oxygen in the air atmosphere, but indicates that oxygen is slightly contained in the non-oxidizing atmosphere. As a result of investigations by the present inventors, it has been found that if the surface roughness of both joining members in the joint portion is Ra 0.3 μm or less, better joining can be obtained, and more preferably, Ra 0.25 μm or less is stable. It was also found that a good bonding state can be obtained. When the surface roughness exceeds Ra 0.3 μm, brazing performance is deteriorated because sufficient confidentiality cannot be obtained even if the pressure adhesion is increased.

6). Initial oxide film thickness of brazed component In carrying out the present invention, since it is not necessary to produce a material that suppresses the initial oxide film on the surface of the material in particular, it can usually be produced as a mass production coil material of aluminum. An aluminum material having an oxide film thickness of about 20 to 500 mm can be used. If it is less than 20 mm, acid cleaning or the like as shown in the prior art is required, and if it exceeds 500 mm, the oxide film destruction action by Mg cannot be sufficiently obtained, and it becomes difficult to obtain a good bonding state.

7). In-furnace atmosphere In carrying out the present invention, the atmosphere in the furnace is changed to a non-oxidizing gas such as an inert gas or a reducing gas, thereby reducing the oxygen concentration and dew point in the atmosphere and It is necessary to suppress oxidation. The type of replacement gas to be used is not particularly limited in obtaining bonding, but from the viewpoint of cost, nitrogen, argon, and hydrogen, ammonia, and carbon monoxide are used as the inert gas and the reducing gas, respectively. Is preferred. The oxygen concentration management range in the atmosphere is preferably 5 to 500 ppm. If it is less than 5 ppm, there is no problem in the joining, but there is a concern that the manufacturing cost will increase, such as using a large amount of gas for managing the atmosphere. If the content exceeds 500 ppm, the reoxidation of the brazed member is likely to proceed, and in particular, it is not possible to sufficiently obtain a bond between the bare component member having no brazing material on the surface and the brazing material.

8). Brazing temperature In the present invention, brazing can be performed at the lowest solidus temperature of 559 ° C. of the brazing material Al—Si—Mg alloy, and naturally, the brazing temperature range by the conventional Al—Si brazing material is also used. Is possible. Specifically, 559-620 degreeC is good. If it is less than 559 degreeC, the melting | fusing of a brazing cannot be obtained and brazing cannot be obtained. If it exceeds 620 ° C., the wax erosion becomes remarkable, which causes a problem in maintaining the product shape and the like, which is not preferable. However, even in this temperature range, if the solidus temperature is low due to the alloy composition of the brazing, brazing erosion may become prominent. In this case, the brazing temperature suitable for the alloy composition within this temperature range. Is preferably selected.

In the present invention, an appropriate amount of Mg added to the brazing material breaks down the oxide film on the contact surface of the joint portion and suppresses reoxidation, so that good bonding can be obtained. This mechanism itself is the same as the conventional technology that proposes vacuum brazing, fluxless brazing under atmospheric pressure, etc. However, in vacuum brazing, it is essential to maintain a vacuum to prevent reoxidation of members. In addition, in the prior art under atmospheric pressure, an anti-oxidation layer is provided on the surface of the brazing material, or the brazed member is covered and surrounded to prevent re-oxidation of the material and diffusion of Mg vapor. There is a need to do.
On the other hand, in the present invention, the component members to be bonded are reliably brought into contact with each other, then a certain amount or more of Mg is added to the brazing material, and further brazing is performed in a non-oxidizing atmosphere. A condition has been found in which the oxide film destruction activity by Mg exceeds the surface reoxidation power, and even when the brazing material is located on the outermost surface of the brazing component, the bonding is established. At this time, Mg added to the brazing material lowers the melting point of the brazing, and the effect that the getter action of Mg and the melting of the brazing (including local melting) occur in almost the same temperature range can be obtained, thereby improving the brazing property. ing.
Furthermore, the presence of 25% or more of coarse Si particles on the surface of the brazing material causes almost no clogging of the inner fins of the heat exchanger having the narrow channel inner fins.
This is because the presence of a predetermined amount or more of coarse Si particles suppresses the flowability of the brazing material, prevents the brazing material from flowing out into the small flow path, and suppresses clogging.

  As described above, if the brazing method for a heat exchanger having a narrow channel inner fin according to the present invention is used, fluxless brazing under atmospheric pressure is possible without requiring flux or vacuum equipment, and brazing material When Mg is added to other brazed constituent members, it does not become a brazing-inhibiting factor, so that it is possible to develop applications for aluminum high-strength members for heat exchangers in which Mg is added to the structural members. In addition, since heating is performed in an atmosphere without decompression, Mg and Zn evaporation from the aluminum material stops around the product, and there is an advantage that contamination of the furnace inner wall and the like hardly occurs.

The disassembled perspective view of the heat exchanger which has the narrow flow path inner fin which is the object of brazing of this invention. The front view which shows the assembly state. Explanatory drawing which shows the flow state of the cooling fluid 11 which distribute | circulates the inside of the heat exchanger which has the same narrow flow path inner fin.

Hereinafter, an embodiment of the present invention will be described.
An Al—Si brazing material containing 0.1 to 5.0% Mg and 3 to 13% Si and a core material can be manufactured by a conventional method, and both or a sacrificial material. Clad rolling with other materials. The production conditions in the clad rolling are not particularly limited as the present invention. Further, the cladding ratio of each layer is not specified as the present invention.
As described above, the composition of the core material is Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, Si: 0.1 to 1.2%, Fe: 0.1 to 1.0%, or Si: 0.1 to 1.2%, Mg: 0 .01-2.0%, and Mn: 0.2-2.5%, Cu: 0.05-1.0%, Fe: 0.1-1.0% It contains seeds or more, and if desired, Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Bi: 0.01 to 1. It is desirable to contain one or more of 0%.

Further, in the present invention, among the number of Si particles contained in the Al—Si brazing material having an equivalent circle diameter of 0.8 μm or more, the number of particles having a diameter of 1.75 μm or more is 25% or more. And In order to obtain this material, in producing a cast slab of brazing filler metal, the cooling rate is set to a range slower than 10 ° C./sec, and the Si particle size generated by solidification cooling is coarsened. Even if the Si particles are crushed, the above conditions can be satisfied. However, even when this cooling rate is higher than 10 ° C./sec, Si particles can be coarsened by applying a heat treatment for several hours under conditions of 500 ° C. or higher as a homogenization treatment after casting, as described above. In addition, it is possible to obtain the Si particle size of the present invention after rolling.
In the present invention, it is desirable that the surface roughness of at least the contact adhesion portion surface of the aluminum clad material and the brazing target member is Ra 0.3 μm or less. This surface roughness depends on the roll surface roughness at the time of final rolling of the material, and can be obtained by setting the roll surface roughness to Ra of 0.45 μm or less. In addition, when the brazed joint portion is a heat exchanger member processed surface such as a press, the target surface roughness can be obtained by similarly controlling the die surface roughness of the press.

In the aluminum clad material obtained by a conventional method, the Al—Si brazing material is located on the outermost surface, and an oxide film having an initial oxide film thickness of 20 to 500 mm is formed.
The aluminum clad material is assembled with a member to be brazed such as a bare fin or a solid material connector, and preferably constitutes a heat exchanger assembly or the like. Note that aluminum materials having various compositions can be used as the brazing target member, and the present invention is not limited to a specific one.

The assembly is placed in a heating furnace having a non-oxidizing atmosphere without decompression. The non-oxidizing atmosphere can be configured using an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen, ammonia or carbon monoxide, or a mixed gas thereof. The non-oxidizing atmosphere is not at reduced pressure during brazing heating and is usually at atmospheric pressure. In addition, before obtaining a non-oxidizing atmosphere, you may include a pressure reduction process for the purpose of substitution. The heating furnace does not need to have a sealed space, and may have a brazing material carry-in port and a carry-out port. Even in such a heating furnace, the non-oxidizing property is maintained by continuously blowing the inert gas into the furnace. The non-oxidizing atmosphere preferably has an oxygen concentration of 5 to 500 ppm by volume.
It brazes by heating at 560-620 degreeC under the said atmosphere. In brazing, the contact and adhesion portion with the brazing target member is satisfactorily joined without flux.

FIG. 1 is an exploded perspective view of a heat exchanger having narrow channel inner fins, which is an object of brazing of the present invention, and FIG. 2 is a front view showing the assembled state. This heat exchanger is compact and flat, and the coolant flows through a number of narrow channels inside. And the to-be-cooled body 6, such as a power transistor, an inverter, and various high heat-generating semiconductors, is brazed to the outer surface, and the generated heat can be cooled.
In the heat exchanger having the narrow channel inner fins, a plurality of intermediate plates 4 (three in this example) are laminated in the thickness direction, and a pair of end plates 5 are arranged at both upper and lower ends thereof, and the space between them is integrated. It is brazed and fixed without flux.

  The intermediate plate 4 has a frame portion 1 on four sides, and a large number of longitudinal ribs 2 are arranged in parallel at regular intervals in the frame portion 1, and between the ribs 2 and between the rib portion 2 and the frame portion 1, there are horizontal ribs 2 a. Are connected together. And a narrow channel is formed between each vertical rib 2, and a cooling fluid distribute | circulates there. The width and depth of each flow path are about 0.7 mm to 2.0 mm as an example. In this example, the position of the horizontal rib 2a is different for each intermediate plate 4. That is, as shown in FIG. 3, the horizontal rib 2a in the upper intermediate plate 4 and the horizontal rib 2a in the lower intermediate plate 4 are arranged at different positions in the flow direction of the coolant 11. Therefore, the coolant 11 bypasses each lateral rib 2 a and flows between the ribs 2. Further, the ribs 2 in the vertical direction of the respective intermediate plates 4 are arranged at the same position. This is to improve the heat transfer between the end plate 5 and each intermediate plate 4.

  The intermediate plate 4 in which a large number of such narrow channels are arranged in parallel has the same frame portion 1 that forms the four circumferences thereof. The pair of end plates 5 is formed to be slightly larger than the outer periphery of the frame portion 1 of the intermediate plate 4. A brazing material is coated on one side or both sides of each intermediate plate 4. The pair of end plates 4 can be a bare material or one coated with a brazing material.

In the above example, the coolant inlet / outlet port 7 is formed at both ends of the end plate 5 at the lower end, and the pipe 8 is connected thereto. Each intermediate plate 4 is provided with a pair of manifolds 3 without ribs 2 at both ends in the longitudinal direction. Each such plate is laminated as shown in FIG. 2, and the whole is inserted into a high-temperature furnace and brazed and fixed together in a non-oxidizing atmosphere, fluxless, and atmospheric pressure.
In addition, the heat exchanger of the present invention is one in which corrugated fins or offset fins are interposed in a pair of flat drone cup-shaped plates instead of the laminated type, and the flow path is 0.7 mm to The present invention can also be applied to those having a large number of narrow channels of about 2.0 mm.

  As the intermediate plate 4, an Al—Si brazing material having the composition shown in Tables 1 to 3 (remaining Al and inevitable impurities) and a core material having the composition shown in Tables 1 to 3 (remaining Al and inevitable impurities). An aluminum clad material was prepared. The Si particle diameter in the brazing material changes the cooling rate during casting in the range of 0.5 to 10 ° C./sec, and the material surface roughness indicates the roll surface roughness during final rolling by Ra 0.05 to 0. It was changed by changing in the range of 90 μm.

The aluminum clad material was prepared by brazing various composition brazing materials and various composition core materials to a brazing material clad rate of 10% and a tempering equivalent to H14 to a thickness of 0.5 mm.
Further, as the end plate 5, a fin material made of JIS A3003 alloy and H14 aluminum bare material (thickness: 0.1 mm) was prepared.

1 Brazing property Using the aluminum clad material of the present invention, the intermediate plate 4 shown in FIG. 1 is manufactured by press molding, and combined with the end plate 5 of the JIS A3003 bare material to form a heat exchanger having a narrow channel inner fin. .
The assembly was heated to 560 to 600 ° C. in a brazing furnace in a nitrogen atmosphere (oxygen content 15 ppm), and brazing was evaluated in the brazed state. The brazing property was evaluated by determining the joining rate according to the following formula and determining the superiority or inferiority of the joining rate and the clogging rate of the narrow channel.

Fin joint rate = (total brazing length of fin and tube / total contact length of fin and tube) × 100
The brazing performance is determined by the fin joint rate after brazing (◎: 95% or more, ○: 85% or more, Δ: 80% or more, ×: less than 80%), and the results are shown in Tables 1 to 3. Indicated.
The clogging property in the narrow channel was evaluated by visual observation, and judged by the magnitude of the channel clogging rate.
Flow path clogging rate = (Clogging area by brazing filler fillet) / (Total flow path area)
The clogging rate is 30% or more, x is 20-30%, Δ is 10-20%, and ◎ is less than 10%. The results are shown in Tables 1 to 3. ○ and ◎ are good, and x and Δ are bad.
The results are shown in Tables 1 to 3.

Material Strength The manufactured clad material (0.5 mm thickness) was a JIS No. 5 test piece, and subjected to a tensile test after brazing heat treatment and after aging treatment at 90 ° C. for 7 days. The obtained material strength measurement values were evaluated, and the results are shown in Tables 1 to 3.

  About the produced clad material, the outermost surface of the brazing material is ground with # 1000 emery paper and then mirror-finished with 0.1 μm abrasive grains. ) Was used for fully automatic particle analysis. The ratio of particles having a particle size of 1.75 μm or more out of the total number of particles measured of 0.8 μm or more is shown in the table.

While all of the examples showed good brazing properties, the comparative example did not provide sufficient bonding. Further, in the examples, it was possible to achieve both high material strength and brazing, but the conditions were not obtained with the comparative material. Furthermore, in the comparative material, the clogging rate in the narrow channel was large.
Further, in the reference example in which the core component deviated from the preferred range, various problems were observed.

1 Frame 2 Rib
2a Horizontal rib 3 Manifold 4 Intermediate plate 5 End plate
5a Edge 6 Object to be cooled 7 Coolant inlet / outlet 8 Pipe
11 Coolant

Claims (9)

A heat exchanger having a narrow flow path inner fin using an aluminum clad material in which an Al-Si brazing material containing 0.1 to 5.0% Mg and 3 to 13% Si is located on the outermost surface in mass%. A brazing method,
Si particles contained in the Al—Si brazing material have an equivalent circle diameter of 0.8 μm or more, and the number of particles having a diameter of 1.75 μm or more is 25% or more, which is accompanied by decompression. In a non-oxidizing atmosphere, the Al-Si brazing material and the brazing target member are brought into close contact with each other,
A fluxless brazing method for a heat exchanger having a narrow channel inner fin, wherein the aluminum clad material and the brazing target member are joined at a heating temperature of 559 to 620 ° C.   2. The heat exchanger having a narrow channel inner fin according to claim 1, wherein the surface roughness of at least a contact adhesion portion surface of the aluminum clad material and the brazing target member is Ra 0.3 μm or less. Fluxless filtration method.   The heat exchanger having a narrow channel inner fin according to claim 1 or 2, wherein the Al-Si brazing material contains 0.01 to 1.0% Bi by mass. Fluxless brazing method.   The core material in which the Al—Si brazing material is clad contains, by mass%, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, the balance Al and inevitable impurities A fluxless brazing method for a heat exchanger having a narrow channel inner fin according to claim 1, wherein the fluxless brazing method has a composition comprising:   The core material on which the Al—Si brazing material is clad is mass%, Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, Si: 0.1 to 1. The narrow channel inner fin according to any one of claims 1 to 3, comprising 2%, Fe: 0.1 to 1.0%, and having a composition composed of the balance Al and inevitable impurities. A fluxless brazing method for a heat exchanger.   The core material in which the Al—Si brazing material is clad contains, by mass%, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, and Mn: 0.00. 2 to 2.5%, Cu: 0.05 to 1.0%, Fe: One or more of 0.1 to 1.0%, and a composition comprising the balance Al and inevitable impurities A fluxless brazing method for a heat exchanger having a narrow channel inner fin according to any one of claims 1 to 3.   The core material in which the Al—Si brazing material is clad contains, by mass%, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, and Mn: 0.00. 2 to 2.5%, Cu: 0.05 to 1.0%, Fe: 0.1 to 1.0%, or one or more of Zr: 0.01 to 0.3 %, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Bi: 0.01 to 1.0%, or one or more of them, and the balance is inevitable with Al The fluxless brazing method for a heat exchanger having a narrow channel inner fin according to any one of claims 1 to 3, wherein the fluxless brazing method has a composition comprising impurities.   The Al-Si brazing material according to any one of claims 1 to 3 is clad on a core material, and the Al-Si brazing material is located on the outermost surface, and is fluxed in a non-oxidizing atmosphere without depressurization. An aluminum clad material for fluxless brazing of a heat exchanger having narrow channel inner fins, characterized in that the aluminum clad material is used for brazing of loess.   The aluminum clad material for fluxless brazing of a heat exchanger having a narrow channel inner fin according to claim 8, wherein the core material has the composition described in any one of claims 4 to 7.

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