JPH0942891A - Method for manufacturing radiator core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an anti-corrosion characteristic of a radiator core by a method wherein a plurality of fins of either copper or brass and a plurality of tubes of brass are assembled to each other, thereafter a soldering material containing Pb and Sn coated is melted at these tubes and Sn contained in the soldering material is dispersed into the tube when they are melted. SOLUTION: A radiator 10 is constructed such that an upper tank 12 and a lower tank 13 are arranged at an upper part and a lower part of a radiator core 11 constituting many tubes 14 made of brass having a plurality of fins 6 of copper or brass fixed to its outer circumferential surface. Then, in the case that a soldering material containing Pb and Sn coated is melted at each of the tubes 14 so as to solder the fins 16 and the tubes 14 together, Sn contained in the soldering material is dispersed in each of the tubes 14. With such an arrangement as above, it is possible to improve an anti-corrosion characteristic of the radiator core 11 without increasing its manufacturing cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a radiator core for preventing corrosion of a water-cooled radiator for cooling an engine. More specifically, the present invention relates to a method of manufacturing a radiator core that prevents dezincification corrosion of the radiator core.

[0002]

2. Description of the Related Art As shown in FIG. 1, a radiator 10 of this type is provided with an upper tank 12 and a lower tank 13 at an upper portion and a lower portion of a radiator core 11 which is composed of a large number of tubes having fins fixed to the outer peripheral surface thereof. ing. The radiator core 11 is composed of a tube 14 made of brass having a hollow oval cross section through which cooling water flows, and a fin 16 formed by a thin copper strip or a brass strip by a gear type roll of a fin machine. These tubes 14 and fins 16
Are fixed to each other, and the upper tank 12 provided at the top
A high temperature cooling water warmed by the engine flows from the inside to the tube 14, and the fins 16 take heat to cool the cooling water, and then flow to the lower tank 13 below. The transfer of heat in the radiator core 11 is the transfer of heat between the tube 14 and the cooling air in contact with the surface of the metal wall of the fin 16. By allowing cooling air to flow between the fins 16, heat of the rotating engine is released from the radiator core 11 so that the engine can be cooled. Since the cooling water flows through the tubes 14 of the radiator core 11 as described above, safety against water leakage of the radiator core 11 is required.

However, as a cause of water leakage, which is a malfunction of the radiator core 11, perforation due to corrosion has been conventionally known, and it is particularly pointed out that the cause thereof is due to dezincification corrosion. Dezincification corrosion is a corrosion phenomenon that often occurs in brass due to dealloying. It is a corrosion phenomenon of a type in which elements that make up the alloy, that is, Zn out of Cu and Zn are selectively eluted and Cu remains. That is. The cause of this is not yet fully clarified at present, but it is said that the contaminated air comes into contact with the radiator core 11 when the water-cooled radiator is used in an air-polluted environment. In order to solve these problems, it is conceivable to use tin-containing brass as a material in which the tendency of dezincification corrosion is relatively suppressed. This tin-containing brass is suitable for parts that require seawater resistance, and Admiralty metal or Neval brass are prominent.

[0004]

However, tin-containing brass has increased hardness and strength due to the addition of tin. Particularly, when tin is contained in excess of the solid solubility limit, it exhibits hardness and brittleness.
It is not a suitable material to use for the radiator core 11. In particular, in order to use this tin-containing brass for the fins 16, it is difficult to process because it is formed by the gear type roll of the fin machine, and there is a problem that the unit price is pushed up due to the difficulty of processing. An object of the present invention is to provide a method for manufacturing a radiator core, which manufactures a radiator core excellent in corrosion resistance without using a special material.

[0005]

The invention according to claim 1 is
As shown in FIGS. 1 to 3, after assembling a plurality of fins 16 made of copper or brass and a tube 14 made of a plurality of brass, Pb and Sn coated on the tube 14 are assembled.
It is an improvement of the method for manufacturing a radiator core in which the fin 16 and the tube 14 are soldered by melting the solder containing the. The characteristic structure is that Sn contained in the solder is diffused into the tube 14 when the solder is melted. The invention according to claim 2 is the invention according to claim 1, wherein the melting of the solder is at least 9 at 300 ° C to 330 ° C.
This is a method for manufacturing a radiator core, which is performed for a minute.

The present invention will be described in detail below. (a) Tube and fin The tube 14 is formed from a hoop of brass strip having a thickness of 0.13 mm to 0.15 mm by a tube rolling device. As shown in FIG. 2 and FIG. 3, the cross-sectional shape of the tube 14 is formed into an oval shape, and as shown in FIG.
The fins 16 are later fixed to the outer peripheral portion of the plate 4 over substantially the entire length. There are many kinds of brass used depending on the ratio of Cu and Zn, but any brass can be used as long as it can be processed into the tube 14. 70Cu-30, which is generally well known for deep drawing because it is easy to cold work.
Zn is common.

The fin 16 is made of copper or brass having a thickness of 50 μm to 60 μm and may be either a plate fin or a corrugated fin. Although not shown, the plate fin is a plate-shaped fin that is superposed at a predetermined interval and has a tube penetrating therethrough. The corrugated fins are formed in a corrugated shape from a copper or brass hoop by a gear-shaped roll as shown in FIG. 3, and a plurality of louvers 16a are simultaneously formed if necessary. The tubes 14 and the fins 16 are arranged alternately, and the tubes 14 and the fins 16 are arranged.
The radiator core 11 shown in FIG. 1 is formed by joining and to each other.

(B) Assembling of radiator core and solder coating The fin 16 and the tube 14 are assembled by a core assembling device (not shown). In this device, tube 14
It is possible to arrange a large number of them in the vertical direction and mechanically push the fins 16 from above, or to arrange the fins 16 in the upper and lower groove plates and insert the tubes 14 into the fins 16 in the horizontal direction. The coating of the tube 14 may be performed by coating the tube 14 with solder in advance, and after the tube 14 and the fin 16 are assembled, as shown in FIG.
The solder may be melted with a soldering iron or a gas burner and poured into the joint between the tube 14 and the fin 16 as indicated by the arrow A. The solder is an alloy of Pb and Sn, and any solder can be used as long as it contains Sn. However, a solder having a high Sn content or a low Sn content has a high melting point, and it is difficult to control the melting temperature. Therefore, a solder having a relatively low melting point of 35% is preferable.

(C) Diffusion of tin (Sn) into the tube Sn is preferably diffused into the tube 14 by heating the assembled radiator core 11 with a hot air oven. This is because the solder coated on the tube 14 is melted, is adapted to the surface thereof, and Sn of the solder is diffused into the brass of the tube 14. In the invention according to claim 2, the melting of the solder is limited to 300 ° C to 330 ° C because the solder flows out at a temperature higher than this temperature and activates zinc chloride (ZnCl ₂ ) at a temperature lower than this temperature. This is because the oxide film cannot be removed, and sufficient joining with solder cannot be expected. A preferable melting temperature is 300 ° C to 320 ° C.
° C. Further, the melting time is set to at least 9 minutes because if the time is shorter than this, sufficient diffusion of Sn cannot be expected. In addition, this time is preferably 9 minutes to 15 minutes, most preferably 9 minutes to 11 minutes, and sufficient penetration of Sn can be expected by melting for 9 minutes. I can not expect penetration,
This is because waste of work time can be prevented. When Sn sufficiently penetrates into brass, the strength of the tubes 14 and the fins 16 forming the radiator core 11 against dezincification corrosion is improved.

[0010]

【Example】

<Embodiment 1> As shown in FIG. 3, a tube 14 is formed by forming a brass strip having a thickness of 0.15 mm into an elliptical cross section having a major axis direction of 13 mm and a minor axis direction of 1.65 mm by a tube rolling device. Tube 14 was obtained by cutting into 650 mm. The fin 16 has a thickness of 50 μm and a width of 49 m
brass strips of m with a gear type roll, a pitch of 3.0 mm,
Fins 16 were obtained by forming a corrugation having a height of 10.0 mm.
The brass used for these fins and tubes is 65Cu-35Zn brass, respectively. These tubes 14
The fins 16 and the fins 16 are alternately arranged by the assembling device, and the fins are fixed over substantially the entire length of the tube 14. A contact portion between the fixed fin and the tube, that is, all the portions indicated by an arrow A in the drawing was coated with a solder containing a solder containing 35% Sn. After this solder coating,
Fins 16 and tubes 14 in a 300 ° C hot air oven
Was heated and the heating was continued for 9 minutes after the solder was melted again. Then, it was taken out of the furnace and air-cooled to solidify the solder, and the tube 14 and the fins 16 were joined to obtain a radiator core 11.

COMPARATIVE EXAMPLE 1 Although not shown, a radiator core having the same structure as that of Example 1 was used, except that the radiator core was heated for 2 minutes in a hot air oven having a solder melting temperature of 320 ° C. And That is, after tubes and fins are alternately arranged and fixed by an assembling device, a soldering iron is used to coat the solder containing 35% Sn, and the solder is melted in a hot air oven at 320 ° C. for 2 minutes to form the tubes. A radiator core was obtained by soldering with fins.

<Comparison Test and Evaluation> The radiator cores of Example 1 and Comparative Example 1 were cut into a predetermined size, respectively.
The surface D of FIG. 3 was fixed so as to be the polishing surface described below and embedded in a conductive resin. After the conductive resin was sufficiently cured, the cut surface of each cut sample was polished. Polishing was performed until the polished surface finally became a mirror surface.
The mirror-finished cross section was subjected to line analysis by an electron probe microanalyzer (EPMA) to examine the formation state of each tube. The results are shown in FIG. 4 for the results of Example 1 and FIG. 5 for the results of Comparative Example 1. 4 and 5, the horizontal axis represents the scanning distance from the surface of each sample to the inner surface of each tube, and the vertical axis represents the intensity. The solid lines in FIGS. 4 and 5 show the Sn concentration distribution, and the broken lines show the Zn concentration distribution.

As is clear from FIGS. 4 and 5, in both Example 1 and Comparative Example 1, Sn has a strong strength on the surface of the tube. This is considered to indicate Sn of the solder coating applied to the surface of the tube. Next, in the plate material of the radiator core tube 14 in Example 1, although Sn was detected in the entire range from the outer surface to the inner surface of the plate of the radiator core tube 14 in the plate material of the radiator core tube in Comparative Example 1. Although Sn was detected in the vicinity of its front side, its strength decreased toward the inside of the tube, and it was revealed that Sn did not diffuse in all ranges. This is considered to be due to the difference in solder melting time and melting temperature. Further, both Sn and Zn have a sharp decrease in strength from the inner surface of the tube, that is, the inner surface of the tube through which the cooling water passes. It is considered that this is because the inner surface is not coated with solder.

[0014]

As described above, according to the present invention, the fin and the tube made of brass are assembled, and the fin and the tube are soldered by melting the solder containing Sn, and the fin is contained in the solder. Since Sn is diffused in the tube, it is possible to form a solid solution with Sn in brass with the radiator core assembled. As a result, the strength of the tubes and fins forming the radiator core against dezincification corrosion can be improved without using a special material such as brass containing tin. Further, if the melting of the solder for diffusing Sn into the tube is performed at 300 ° C. to 330 ° C. for at least 9 minutes, the number of manufacturing steps does not increase as compared with the conventional radiator core manufacturing method. Therefore, the corrosion resistance of the radiator core can be improved without increasing the manufacturing cost.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a radiator including a radiator core of the present invention.

FIG. 2 is a sectional view taken along line BB of FIG. 1;

FIG. 3 is a sectional view taken along the line CC of FIG.

FIG. 4 is a line analysis diagram of a cross section of the tube of Example 1 by an electron probe microanalyzer.

5 is a line analysis diagram of a cross section of the tube of Comparative Example 1 by an electron probe microanalyzer. FIG.

[Explanation of symbols]

 11 radiator core 14 tube 16 fin

Claims (2)

[Claims] 1. After assembling a plurality of fins (16) made of copper or brass and a tube (14) made of a plurality of brass, the solder containing Pb and Sn coated on the tube (14) is melted. In the method of manufacturing a radiator core by soldering the fin (16) and the tube (14), the Sn contained in the solder when the solder is melted is diffused into the tube (14). Core manufacturing method. 2. The method of manufacturing a radiator core according to claim 1, wherein the melting of the solder is performed at 300 ° C. to 330 ° C. for at least 9 minutes.