JP2942116B2 - Extruded zinc-coated material for heat exchanger and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-coated extruded member for a heat exchanger in which a zinc-coated layer made of zinc (Zn) or a zinc-based alloy is provided on the surface of an extruded aluminum member and a method for producing the same.

[0002]

2. Description of the Related Art An aluminum heat exchanger core comprises an aluminum flat tube and fins brazed to the flat tube so that a liquid (heat transfer medium) flows through the flat tube. Has become. Since the aluminum heat exchanger core assembled in a vehicle or the like is used in a severe environment, the flat tube is easily corroded, and there is a possibility that liquid leakage may occur. For this reason, a clad tube in which a zinc material is clad on an extruded aluminum material and a zinc coating layer is provided is used for an aluminum heat exchanger core that is assembled in a vehicle or the like and used in a severe environment.

[0003] Although this clad tube has extremely good corrosion resistance against pitting and crevice corrosion, it has a drawback that the brazing operation is hindered by the zinc coating layer on the clad tube surface when brazing the fin material. In particular, when the thickness of the zinc coating layer is large, the zinc may melt and flow down due to heating during brazing, and the brazing operation becomes extremely difficult.

For this reason, instead of forming the zinc coating layer by cladding, the surface of the extruded aluminum material has a Z
A zinc-coated extruded tube in which n or a Zn-based alloy is thermally sprayed and Zn is diffused and permeated into the surface of an aluminum shape has been proposed (Japanese Patent Publication No. 4-45577).

[0005]

However, in the above-described conventional zinc-coated extruded tube, Zn-adhered powder (so-called surface dust) adheres to the surface of the zinc-coated layer. There is a problem that flaws are easily generated on the pipe surface in the core assembling step, the fin brazing step, and the like. For this reason, there is a demand for a zinc-coated extruded member having very little powder adhering to the surface.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a zinc-coated extrusion for a heat exchanger provided with a zinc-coated layer having a very small amount of powder adhering to the surface and causing a flaw on the surface of the tube. An object of the present invention is to provide a shape member and a method for manufacturing the same.

[0007]

According to the present invention, there is provided a zinc-coated extruded shape for a heat exchanger, comprising a zinc-coated layer formed by spraying zinc or a zinc-based alloy on the surface of an extruded aluminum material. In the coated extruded profile, the zinc coating layer has a surface roughness Rmax of 30 μm or less.

The method for producing a zinc-coated extruded member for a heat exchanger according to the present invention comprises a step of forming an extruded aluminum member having a predetermined shape by a hot extrusion method, and a step of forming zinc or aluminum on the surface of the extruded aluminum member. A step of spraying a zinc-based alloy to form a zinc coating layer, and a cooling step of cooling the extruded aluminum material provided with the zinc coating layer at a cooling rate of 10 ° C./sec or more. .

[0009] In the present application, aluminum means an aluminum alloy in addition to pure aluminum.

[0010]

The present inventors conducted various experimental studies in order to improve the surface condition of a zinc-coated extruded member for a heat exchanger. As a result, it has been found that by removing relatively large powder adhering to the surface of the zinc coating layer, it is possible to prevent generation of flaws on the tube surface in the heat exchanger manufacturing process.

That is, in the present invention, the surface roughness Rmax of the zinc coating layer is set to 30 μm or less. When the surface roughness Rmax of the zinc coating layer exceeds 30 μm, relatively large surface-adhered powder adhering to the zinc coating layer tends to separate from the zinc coating layer surface in steps such as core assembly and fin brazing. The surface of the tube is liable to be scratched by the detached surface adhering powder. Therefore, the surface roughness R of the zinc coating layer
max needs to be 30 μm or less.

Next, the present inventors conducted an experimental study on a method for reducing the surface roughness Rmax of the zinc coating layer to 30 μm or less. As a result, after spraying Zn or a Zn-based alloy on the surface of the aluminum extruded tube to form a zinc coating layer, when the zinc coating layer is quenched, the heat shrinkage of the zinc coating layer and the heat shrinkage of the powder adhered to the surface are reduced. It was found that a relatively large surface-adhered powder attached to the surface of the zinc coating layer was dropped due to the difference from the above.

That is, in the method of the present invention, a zinc coating layer is formed by spraying Zn or a Zn alloy on the surface of an extruded aluminum material, and then, at a cooling rate of 10 ° C./sec or more, for example, at a temperature of 200 ° C. or less. Force cooling to This allows
It is possible to remove relatively large surface adhering powder adhering to the surface of the zinc coating layer. In this case, the cooling rate is 1
When the temperature is lower than 0 ° C./second, the effect of removing the powder adhering to the surface cannot be sufficiently obtained. Therefore, the cooling rate is 10 ° C
/ Sec or more.

The cooling may be carried out, for example, by bringing the extruded aluminum material having the zinc coating layer into contact with flowing water or by spraying water onto the extruded aluminum material. Water is applied to the extruded aluminum material on which the zinc coating layer is formed, so that the powder adheres in an unstable state due to the effect of the impact force of water and the above-mentioned effect of the difference in thermal shrinkage due to cooling. (Zn powder) falls off. When cooling with running water, the flow rate of the running water is preferably 1 m / min or more in order to increase the cooling efficiency.

[0015]

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a method for producing a zinc-coated extruded shape for a heat exchanger according to an embodiment of the present invention. The extrusion press 1 is provided with an extrusion die 2, and the extrusion press 1 continuously extrudes and forms an aluminum extrusion 3a. A spraying machine 4 is disposed above and below the extruded profile conveying path near the extrusion press 1, and Zn sprays around the aluminum extruded profile 3 a by the spraying machine 4.
Alternatively, a Zn coating layer is formed by spraying a Zn-based alloy.

The extruded aluminum material (zinc-coated aluminum extruded material 3b) on which the zinc coating layer is formed by these spraying machines 4 then enters the cooling water tank 5. The tank 5 is provided with a pump 6 and an injection nozzle 7, and the pump 6 and the injection nozzle 7 allow the extruded zinc-coated aluminum material 3 b to pass through the cooling water tank 5.
Water is sprayed towards. By this water spray, the zinc-coated aluminum extruded profile 3b, which has become hot immediately after thermal spraying, is rapidly cooled. At this time, the surface-adhered powder adhering to the surface of the zinc coating layer rapidly undergoes heat shrinkage and separates from the zinc coating layer. Further, the pressure of the water further promotes detachment of the powder adhering to the surface.

The extruded zinc-coated aluminum material 3b from which the powder adhering to the surface has been removed in this way is then conveyed by a pinch roll 8 and wound up, for example, on a drum.

In this embodiment, after a zinc coating layer is formed around the aluminum extruded profile 3a by the thermal spraying machine 4 to form a zinc-coated aluminum extruded profile 3b, water is sprayed to the zinc-extruded aluminum extruded profile 3b. 3b is rapidly cooled, so that relatively large powder adhering to the surface of the zinc coating layer can be removed, and the surface roughness R of the zinc coating layer surface can be reduced.
max can be 30 μm or less. This allows
It is possible to prevent the occurrence of flaws on the tube surface in the heat exchanger core assembling step or the like.

Next, an extruded zinc-coated aluminum material was actually manufactured by the method of the above-described embodiment, and the result of examining the surface condition thereof will be described in comparison with a comparative example.

First, as shown in FIG. 1, a spraying machine 4 is installed near the exit of the die 2 of the extruder 1, and immediately after that, a cooling water tank 5 is installed, and an aluminum material A1050 having a composition shown in Table 1 below is prepared. Billet (diameter 200mm, length 5
4), an oval multi-hole tube (width: 22 mm, height: 5 mm, wall thickness: 0.8 mm) whose cross-sectional shape is shown in FIG. 4 was hot-extrusion molded. In this case, the extrusion speed is 50 m / min.

[0022]

[Table 1]

Next, on the peripheral surface of the multi-hole tube, Zn is continuously sprayed by a spraying machine 4 using Zn wire as a spraying material, with a target value of Zn deposition amount of about 25 g / mm ² . A zinc coating layer was formed. Then, the zinc-coated tube immediately after the formation of the zinc-coated layer was forcibly cooled to a temperature of 200 ° C. or lower in the cooling water tank 5. The cooling rate at this time is about 200 ° C./sec. On the other hand, as a comparative example, a zinc-coated tube manufactured in the same manner as in the above-described example except that the zinc-coated layer was formed by thermal spraying and then naturally cooled was prepared.

The sections of the zinc-coated tubes of this example and the comparative example were observed with a microscope. FIGS. 2 and 3 are micrographs (magnification × 300 times) showing the metal structures near the surfaces of the zinc-coated tubes of Examples and Comparative Examples, respectively. As apparent from FIGS. 2 and 3, the surface of the zinc-coated tube of the example had almost no powder adhering to the surface, and the surface was relatively smooth. On the other hand, relatively large surface-adhered powder adhered to the surface of the zinc-coated tube of the comparative example.

For the zinc-coated tubes of this example and the comparative example, the amount of Zn deposited was examined by a nitric acid dissolution method using nitric acid having a concentration of 30% by weight. Further, the surface roughness Rmax of the zinc-coated tubes of this example and the comparative example was also examined. The results are shown in Table 2 below.

[0026]

[Table 2]

As apparent from Table 2, in the zinc-coated tube of the embodiment, the zinc-coated layer is thin and
The surface roughness Rmax was as small as about 26 μm. On the other hand, the zinc-coated tube of the comparative example had a large amount of deposited Zn and a large surface roughness Rmax of 41 μm.

Next, the results of examining the Zn diffusion state of the zinc coated tubes of the examples and comparative examples will be described.

A brazing sheet fin composed of a core material and a brazing material covering the surface of the core material was combined with the zinc-coated tubes of the above-described Examples and Comparative Examples, and brazed under the conditions shown in Table 3 below. A laminated brazing material was manufactured.

[0030]

[Table 3]

Then, using an X-ray analyzer, Zn on the surface of each zinc-coated tube of this example and the comparative example was measured.
The diffusion state was examined. FIGS. 5 and 6 are graphs showing the Zn concentration distribution on the surface of the zinc-coated tube of the example and the comparative example, respectively. As shown in FIGS. 5 and 6, in each of the zinc-coated tubes of the example and the comparative example, the Zn diffusion layer was formed with a thickness of about 160 μm.

Next, the zinc-coated tubes of this example and the comparative example were subjected to the CA specified in JIS8661.
The SS test was performed for 700 hours, and then the state of corrosion was examined. As a result, none of the zinc-coated extruded profiles of the example and the comparative example was observed to have pitting corrosion in the form of surface corrosion, and it was confirmed that the Zn diffusion layer was uniformly adhered even after the CASS test. .

In the above embodiment, the case where the zinc-coated aluminum extruded material immediately after thermal spraying is cooled by spraying water has been described. However, the zinc-coated aluminum extruded material is cooled by passing it through running water. Even in this case, the same effect as in the above embodiment can be obtained.

[0034]

As described above, according to the present invention, the surface roughness Rmax of the zinc coating layer formed by spraying zinc or a zinc-based alloy on the surface of an extruded aluminum material is 30 μm.
As described below, the extruded zinc-coated member for a heat exchanger according to the present invention can prevent generation of flaws due to detachment of powder adhering to a surface in a heat exchanger core assembling step and a fin brazing step.

According to the method of the present invention, zinc or a zinc-based alloy is sprayed on the surface of the aluminum profile to form a zinc coating layer, and then quenched at a predetermined cooling rate. The relatively large powder adhering to the surface can be easily removed. This makes it possible to obtain a zinc-coated extruded shape for a heat exchanger in which the surface state of the zinc-coated layer is good and the corrosion resistance is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for producing a zinc-coated extruded shape for a heat exchanger according to an embodiment of the present invention.

FIG. 2 is a micrograph (magnification: 300 times) showing a metal structure near the surface of a zinc-coated tube of an example.

FIG. 3 is a micrograph (magnification × 300) showing a metal structure near the surface of a zinc-coated tube of a comparative example.

FIG. 4 is a sectional view showing an extruded aluminum material (multi-hole tube).

FIG. 5 shows Zn on the surface of the zinc-coated tube of the embodiment.
It is a graph which shows distribution.

FIG. 6 shows Zn on the surface of a zinc-coated tube of a comparative example.
It is a graph which shows distribution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Extrusion press 2; Extrusion die 3a; Aluminum extruded profile 3b; Zinc-coated aluminum extruded profile 4; Thermal sprayer 5; Cooling water tank 6; Pump 7;

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Seiji Enomoto 14-1, Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Inside of Kobe Steel's Chofu Works (56) References JP 4-45577 (JP, B2) (58) Field surveyed (Int.Cl. ⁶ , DB name) B21C 23/30 C23C 4/00-6/00 F28F 19/06

Claims (5)

(57) [Claims] 1. A zinc-coated extruded shape for a heat exchanger in which zinc or a zinc-based alloy is sprayed on a surface of an extruded aluminum material to form a zinc-coated layer, wherein the surface roughness Rmax of the zinc-coated layer is 30 μm or less. A zinc-coated extruded shape for a heat exchanger, characterized in that: 2. A step of forming an aluminum extruded shape having a predetermined shape by a hot extrusion method, and a step of spraying zinc or a zinc-based alloy on a surface of the aluminum extruded shape to form a zinc coating layer. And a cooling step of cooling the extruded aluminum member provided with the zinc coating layer at a cooling rate of 10 ° C./sec or more. 3. The production of a zinc-coated extruded member for a heat exchanger according to claim 2, wherein the cooling step is performed by bringing the aluminum extruded member provided with the zinc-coated layer into contact with flowing water. Method. 4. The method according to claim 3, wherein the flow rate of the running water is 1 m / min or more. 5. The extruded zinc-coated member for a heat exchanger according to claim 2, wherein the cooling step is performed by spraying water onto the extruded aluminum member provided with the zinc-coated layer. Manufacturing method.