JP2005254320A - Manufacturing method of heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a heat exchanger which has an excellent strength and can improve production efficiency significantly. <P>SOLUTION: The manufacturing method of the heat exchanger 1 comprises in order: a preheating step to heat an assembly of a core part 4 and tank parts 5, 6 in advance after assembling the core part 4 and the tank parts 5, 6; a brazing step to braze these core part 4 and tank parts 5, 6; a slow cooling step to gradually remove the heat of the brazed core part 4 and tank parts 5, 6; and a cooling step to cool the core part 4 and tank parts 5, 6 to ambient temperature after the slow cooling step. An oxygen content in the slow cooling step is set to a higher content than the oxygen content in the steps prior to the slow cooling step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a heat exchanger such as an evaporator or a condenser, and more particularly to a technique for improving a brazing method between a core portion and a tank portion in an aluminum heat exchanger.

  In general, an aluminum heat exchanger includes an evaporator, a condenser, a radiator, and the like, and these are generally manufactured by a brazing method. This manufacturing method is performed by assembling various parts of a heat exchanger such as a core part made of tubes, fins, etc., a tank part made of a header plate, a tank cover member, etc. It brazes integrally through the brazing material previously provided in the junction part between various components.

  Various parts of such an aluminum heat exchanger are materials (hereinafter referred to as a core material) based on an aluminum alloy mainly containing pure aluminum and an element such as Mn. Therefore, in order to join the parts to each other, a material obtained by clad a brazing material of an Al-Si alloy having a melting point lower than that of the core material containing Si or the like in aluminum is used on the surface of the core material at the joining portion. . Then, instead of assembling these parts or clad the brazing material, put the brazing material foil at the joint with the core part and assemble these parts, and then apply the flux to the brazed joint Then, brazing is performed in a predetermined furnace, or brazing is performed in a vacuum furnace without applying a flux.

  Specifically, such a brazing operation includes a preheating process in which the assembled core part and the tank part are heated in advance, a brazing process in which the core part and the tank part are brazed, and a brazed core. It consists of a gradual cooling process that gently removes heat from the tank part and the tank part, and a cooling process that cools the core part and tank part that have undergone the gradual cooling process to room temperature. These preheating process, brazing process, gradual cooling process and cooling By sequentially performing the steps, the core part and the tank part are joined to form a heat exchanger.

  At this time, the oxygen concentration in the furnace atmosphere is kept at a low level until the solidification of the brazing material in the tank portion is completed, that is, throughout the entire heat treatment, and the solidification of the brazing material in the tank portion is completed. After that, it is increased (that is, raised to a high level) in the cooling process.

  However, in such a heat exchanger, since the thickness of the tank portion is larger than the thickness of the core portion, the heat capacity of the tank portion increases. As can be seen from FIG. 5, when the temperature rises, it takes time for the tank portion to reach the brazing step from the preheating step with respect to the core portion. It takes time to reach the temperature (indicated by a bold line in the figure).

  For this reason, in some cases, during cooling, the brazing material flows from the tank portion to the core portion in the slow cooling process, and the core portion (specifically, the joint portion between the fin and the tube or the tube has a B-shaped cross section). In the case of a so-called B-type tube, there is a risk that erosion may occur at the mating portion inside the tube).

  Here, erosion means that Si in the brazing material diffuses into the core material, and if the amount of diffusion is excessive, the original melting point of the core material (in this case, 640 [° C.] to 650 [° C.]). This is a phenomenon that lowers and melts in the vicinity of the brazing temperature (in this case, about 590 [° C.]). When the core material is melted due to the occurrence of erosion, there is a possibility that a through hole is generated in the core portion (in this case, a tube).

As one of the techniques for solving such a problem, as shown in FIG. 6, by spraying a high-temperature nitrogen gas into the tank part which is a large heat capacity part in the preheating step and actively heating the tank part, A technique has been proposed in which the temperature of the tank part is increased before the core part, which is a small heat capacity part (indicated by a thick line in the figure), and the preheating process is shortened (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 2003-80366 (pages 3 and 4; FIGS. 1 and 3)

  However, in the manufacturing method of the heat exchanger described in Patent Document 1, it is possible to improve the production efficiency by spraying high-temperature nitrogen gas to the tank portion in the preheating step and shortening the heating time in the preheating step. However, since the temperature of the tank part increases faster than that of the core part, there is a risk of occurrence of problems such as the flow of brazing material from the tank part to the core part and the erosion associated therewith. Furthermore, in the slow cooling process, it takes time until the tank part reaches the solid phase temperature as compared with the core part (indicated by a thick line in FIG. 6). There are still inadequate problems that can cause problems such as erosion.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a heat exchanger that is excellent in durability and can significantly improve production efficiency.

  The invention according to claim 1 is a preheating step in which the core portion and the tank portion are preheated after the core portion and the tank portion are assembled, and a brazing step in which the core portion and the tank portion are brazed. And a slow cooling process for gently removing the heat of the brazed core part and the tank part, and a cooling process for cooling the core part and the tank part that have undergone the slow cooling process to room temperature in order. In the manufacturing method for manufacturing the above, the annealing step is characterized in that the oxygen concentration is set higher than the oxygen concentration before the annealing step.

  Invention of Claim 2 is a manufacturing method of the heat exchanger of Claim 1, Comprising: Solidification of the brazing material in the said core part is what sets the said oxygen concentration high in the said slow cooling process. It is after being completed.

  Invention of Claim 3 is a manufacturing method of the heat exchanger of Claim 1 or Claim 2, Comprising: The oxygen concentration set in the said slow cooling process is 1000 [ppm] or more. Features.

  According to the first aspect of the present invention, in the slow cooling step, the brazing heat exchanger is gradually cooled in a state where the oxygen concentration is set higher than the oxygen concentration before the slow cooling step. Compared with the above, it can oxidize the brazing filler metal in the tank part with a larger heat capacity and reduce the wettability in this tank part, so that the brazing filler metal flow from the tank part to the core part can be suppressed. It is possible to prevent the occurrence of erosion due to the flow of the material. Thus, strength resistance and production efficiency can be significantly improved.

  According to the second aspect of the present invention, the brazing material from the tank portion to the core portion can be easily and surely set by setting the oxygen concentration high after solidification of the brazing material in the core portion is completed in the slow cooling process. Can be prevented from flowing.

  According to the third aspect of the present invention, when the oxygen concentration set in the slow cooling step is 1000 ppm or more, the brazing material flows from the tank portion having a larger heat capacity than the core portion. Can be easily and reliably prevented.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In addition, this Embodiment is an example which applied the heat exchanger of this invention to the radiator for motor vehicles.

"Configuration of Radiator"
FIG. 1 is an external view showing a schematic configuration of a radiator according to the present invention, FIG. 2 is a perspective view for explaining a main part (core part) of the radiator, FIG. 3 is a temperature change during the brazing process, a time associated therewith, FIG. 4 is a schematic configuration diagram showing a brazing state in the radiator manufactured by the brazing process of FIG. 3.

  As shown in FIG. 1, a radiator 1 that is a heat exchanger of the present embodiment includes a core composed of a plurality of stacked tubes 2 and a plurality of corrugated fins 3 disposed between the adjacent tubes 2 and 2. Connected to the upper header tank portion 5 and the upper header tank portion 5 and the lower header tank portion 6 as tank portions to which the upper end portions and lower end portions of the plurality of tubes 2 in the core portion 4 are respectively connected. An inlet pipe 7 and an outlet pipe 8 are provided.

  The upper and lower header tank portions 5 and 6 are each composed of a header plate 9 and a tank cover member 10 joined to the header plate 9, and a tank chamber 11 is formed therein as shown in FIG. Yes.

  At this time, the radiator 1 is manufactured by the following brazing method. That is, in this manufacturing method, after assembling various parts of the radiator 1 such as the core portion 4 including the tube 2 and the fin 3 and the upper and lower header tank portions 5 and 6 including the header plate 9 and the tank cover member 10, By heating in a furnace not shown in the figure, brazing is integrally performed via a brazing material (not shown) provided in advance at the joint between these various parts.

[Experimental considerations]
Here, the brazing method when actually manufacturing the radiator 1 was examined.

  In the case of the present embodiment, the radiator 1 is formed using aluminum parts, and these various parts mainly have an aluminum alloy containing pure aluminum and an element such as Mn as a core material.

  Therefore, in order to join components together, a brazing material of an Al—Si alloy having a melting point lower than that of the core material containing Si or the like in aluminum is clad on the surface of the core material at the joining portion.

  Then, various parts clad with the brazing material (core part 4, upper and lower header tank parts 5, 6) are assembled, or instead of clad the brazing material, various parts in the core material state (core part 4, After the brazing material foil is placed at the joints of the upper and lower header tank parts 5, 6) and these parts are assembled, flux is applied to the brazed joints and brazed in a predetermined furnace. It is made to braze in a vacuum furnace without coating.

  Specifically, such a brazing operation includes a preheating process in which the assembled core portion 4 and the upper and lower header tank portions 5 and 6 are heated in advance, and the core portion 4 and the upper and lower header tank portions 5 and 6. 6, brazing core part 4 and upper and lower header tank parts 5, 6 are gradually cooled to remove heat, core part 4 that has undergone the slow cooling process and upper part and It consists of a cooling process for cooling the lower header tank parts 5 and 6 to room temperature. By sequentially performing these preheating process, brazing process, slow cooling process and cooling process, the core part 4 and the upper and lower header tank parts 5 , 6 are joined together to form the radiator 1.

  The preheating process melts the flux, the brazing process melts the brazing material, the slow cooling process solidifies the brazing material, and the cooling process cools the heat exchanger to room temperature.

  And in this Embodiment, it sets to the oxygen concentration higher than the oxygen concentration in the atmosphere in the furnace at the time of the pre-heating process before the said slow cooling process, and a brazing process.

  At this time, the oxygen concentration is preferably set to 1000 ppm or more. This is because when the oxygen concentration is less than 1000 [ppm], it is difficult to sufficiently oxidize the brazing filler metal of the upper and lower header tank parts 5 and 6 having a large heat capacity as compared with the core part 4 in the radiator 1. This is because it is difficult to reduce wettability in the upper and lower header tank portions 5 and 6 and local erosion may occur.

  Incidentally, the thicknesses of the tube 2, the fin 3 and the header plate 9 at this time are 0.15 [mm] to 0.30 [mm], 0.06 [mm] to 0.10 [mm], 0. It set in the range of 8 [mm]-1.5 [mm].

And in this Embodiment, the heat exchanger was manufactured using each structural member shown in Table 1. FIG.

  That is, the fin 3 is made of 0.08 [mm] aluminum alloy (JIS standard A3003), the tube 2 is a core material of 0.23 [mm] aluminum alloy (JIS standard A3003), and the sacrificial material is 0.03. [Mm] aluminum alloy (JIS standard A7072), 0.03 [mm] aluminum alloy (JIS standard A4343) as brazing material, and 1.04 [mm] aluminum with header plate 9 as core material Assembling the heat exchanger using an alloy (JIS standard A3003), 0.13 [mm] aluminum alloy (JIS standard A7072) as a sacrificial material, and 0.13 [mm] aluminum alloy (JIS standard A4343) as a brazing material It was.

Next, a preheating process, a brazing process, a slow cooling process, and a cooling process were performed under the conditions shown in Table 2.

  That is, in the preheating step and the brazing step, the oxygen concentration in the furnace was set to 80 [ppm]. In the slow cooling process, when the brazing material of the tube 2 in the core portion 4 is in a molten state, the oxygen concentration in the furnace is set to 80 [ppm], and then the brazing material of the tube 2 is in a solidified state. At this time (at this time, the brazing filler metal of the header plate 9 in the upper and lower header tank portions 5 and 6 is in a molten state and a solidified state), the oxygen concentration in the furnace was set to 1100 [ppm]. In the cooling step, the oxygen concentration increased in the slow cooling step, that is, the oxygen concentration set to 1100 [ppm] was not changed.

  The relationship between the temperature change of the core part 4 and the header plate 9 at this time, and the time accompanying it is shown in FIG. In FIG. 3, the header plate 9 is abbreviated as a tank portion for convenience.

  As shown in FIG. 3, compared to the oxygen concentration (80 [ppm]) in the furnace atmosphere of the preheating step and brazing step during temperature rising, the slow cooling step during cooling (more specifically, the core The oxygen concentration (1100 [ppm]) in the furnace atmosphere at the time when the brazing material of the tube 2 in the section 4 is in a solidified state) is set high, and the brazed heat exchanger is gradually cooled in this state. Therefore, it is possible to oxidize the brazing material of the header plate 9 in the upper and lower header tank portions 5 and 6 having a larger heat capacity than the core portion 4 and reduce the wettability in the header plate 9. That is, the flow of the brazing material from the upper and lower header tank portions 5 and 6 to the core portion 4 (particularly, the tube 2) can be suppressed, and an error caused by the flow of the brazing material The occurrence of John can be prevented in advance.

  As a result, as shown in FIG. 4, no erosion was observed in any of the brazed tube 2 and the joined portion between the tube 2 and the fin 3, and the brazed portion was healthy. In this case, one tube 2 is formed by bending both sides of a flat aluminum plate 2A clad with a brazing material on the surface to approximately 90 ° in the same direction by a method such as a roll homing method. A so-called B-type tube was used, which was bent into a flat tube shape and a middle column formed by abutting the both side portions was erected inside.

  Therefore, in the case of the radiator 1 manufactured using this brazing heat treatment, problems such as the flow of the brazing material to the core portion 4 and the erosion associated therewith in the brazing heat treatment can be avoided. Therefore, the strength resistance can be improved and the production efficiency can be remarkably improved.

  Further, in this case, there is an advantage that the components of the core portion 4 (that is, the tubes 2 and the fins 3) can be thinned as much as erosion can be avoided.

  Furthermore, in the case of this brazing heat treatment, erosion can be prevented by an easy operation that requires only a partial change in the brazing heat treatment conditions, so there is no need for new capital investment and an increase in production costs can be prevented. it can.

  Thus, according to the method for manufacturing a radiator of the present embodiment, the inside of the slow cooling step during cooling is compared with the oxygen concentration in the furnace atmosphere during the preheating step and brazing step during temperature rising. The oxygen concentration in the atmosphere is set high, and the brazed heat exchanger is gradually cooled in this state, so that the header plates 9 in the upper and lower header tank portions 5 and 6 having a larger heat capacity than the core portion 4 are obtained. The brazing filler metal can be oxidized to reduce the wettability of the header plate 9.

  Therefore, in the slow cooling process, it is possible to suppress the flow of the brazing material from the upper and lower header tank portions 5 and 6 to the core portion 4, so that the occurrence of erosion in the core portion due to the flow of the brazing material is prevented. It can be prevented in advance. Thereby, thickness reduction of the tube 2 and the fin 3 which are the components of the core part 4 can be achieved.

  In addition to this, as described above, the quality can be reliably improved by the amount that can prevent the occurrence of problems due to erosion. And the radiator 1 excellent in strength resistance can be manufactured by improving quality in this way.

  Also, by setting the oxygen concentration in the furnace atmosphere high when the brazing material of the tube 2 is in a solidified state, the header plate 9 having a larger heat capacity than the core portion 4 (ie, the upper and lower portions). It is possible to easily and reliably prevent the brazing material from flowing from the header tank portions 5 and 6) to the tube 2 (that is, the core portion 4).

  Furthermore, since the oxygen concentration set at the time of cooling is 1100 [ppm] or more, the brazing filler metal of the header plate 9 is easily and reliably oxidized, so that the flow of the brazing filler metal can be prevented easily and reliably. it can.

"Other embodiments"
Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the above-described embodiment, the case where a so-called B-type tube is used as the tube 2 has been described. However, the present invention is not limited to this, and the tube 2 may be a general flat type, an internal Various shapes of tubes such as those having fins can be widely applied, and even in this case, the same effects as those of the above-described embodiment can be obtained.

It is an external view which shows schematic structure of the radiator which concerns on this invention. It is a perspective view with which it uses for description of the principal part (core part) of a radiator. It is a graph which shows the relationship between the temperature change in the brazing process, the accompanying time, and oxygen concentration. It is a schematic block diagram which shows the brazing state in the radiator manufactured by the manufacturing method to which this invention is applied. It is a graph which shows the relationship between the temperature change at the time of the brazing process in the conventional heat exchanger, and time and oxygen concentration accompanying it. It is a graph which shows the relationship of the temperature change in the time of the brazing process in the other conventional heat exchanger, and accompanying time, and oxygen concentration.

Explanation of symbols

1. Radiator (heat exchanger)
2 ... Tube 3 ... Fin 4 ... Core part 5 ... Upper header tank part (tank part)
6 ... Lower header tank (tank)
9 ... Header plate 10 ... Tank cover member 11 ... Tank chamber

Claims (3)

After assembling the core part (4) and the tank part (5, 6), a preheating step of heating the assembled core part (4) and the tank part (5, 6) in advance, and the core part (4) A brazing step for brazing the tank portions (5, 6), a slow cooling step for gently removing heat from the brazed core portion (4) and the tank portions (5, 6), and this slow cooling step In the manufacturing method for manufacturing the heat exchanger (1) by sequentially performing the cooling step of cooling the core portion (4) and the tank portions (5, 6) to normal temperature through
In the said slow cooling process, it sets to oxygen concentration higher than the oxygen concentration before the said slow cooling process. The manufacturing method of the heat exchanger characterized by the above-mentioned. It is a manufacturing method of the heat exchanger (1) of Claim 1, Comprising:
The method for manufacturing a heat exchanger is characterized in that the oxygen concentration is set high in the slow cooling step after the solidification of the brazing filler metal in the core part (4) is completed. It is a manufacturing method of the heat exchanger (1) of Claim 1 or Claim 2, Comprising:
The method for producing a heat exchanger, wherein the oxygen concentration set in the slow cooling step is 1000 ppm or more.

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