JP3215526B2 - Manufacturing method of aluminum flat tube for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for transporting Zn in a flat tube.
It is possible to prevent loss of the layer (referred to as partial chipping or peeling) and to prevent a decrease in wall thickness due to corrosion of the Al layer of the flat tube after heat treatment, thereby lowering the strength of the flat tube and cracking. The present invention relates to a method for manufacturing an aluminum flat tube for a heat exchanger that can prevent generation of cracks.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing this type of aluminum flat tube for a heat exchanger, Zn is sprayed onto a surface of an aluminum flat tube extruded hot or warm by a Zn wire spraying method. A method is known in which a Zn diffusion-penetrated layer (Zn diffusion layer) is formed on the surface of a flat tube by naturally cooling it, and the Zn layer is adhered to the outer surface of the aluminum flat tube.

[0003] However, when manufacturing an aluminum flat tube for a heat exchanger by this method, when the flat tube after spraying Zn is transported by a roller, the flat Zn tube is still at a high temperature, so that a soft Zn layer is formed. There has been a problem that the flat tube surface is scraped off from the surface of the flat tube due to contact with the roller, thereby causing a product defect. Further, in the aluminum flat tube for a heat exchanger manufactured by this method, a Zn diffusion layer having a sufficient thickness is formed at the time of manufacturing the flat tube, and thereafter, a heat treatment such as brazing a fin material to the flat tube is performed. When this heat treatment is generally performed, the formation of the Zn diffusion layer further proceeds by the heat, and the thickness of the Zn diffusion layer serving as a sacrificial anode becomes unnecessarily thick. For this reason, the thickness of the Al layer of the flat tube becomes thin, and the Zn diffusion-penetrated layer is easily eroded by corrosion, so that the strength of the flat tube itself is reduced, and the problem of causing local cracks is caused. there were.

The present invention has been made in view of the above-mentioned circumstances, and it is intended to prevent the Zn layer from being lost during the transport of a flat tube and to reduce the Al content of the flat tube during use of the heat-treated product.
An object of the present invention is to provide a method of manufacturing an aluminum flat tube for a heat exchanger, which can prevent a decrease in the thickness of a layer and prevent a decrease in the strength of the flat tube and the occurrence of cracks.

[0005]

As a result of conducting various studies to solve the above problems, the inventors found that after the Zn layer was deposited, the aluminum flat tube before the heat treatment was rapidly cooled to solidify the Zn layer and lower the temperature. While preventing the Zn layer from being lost when the aluminum flat tube is transported by the roller,
It can suppress the formation of the diffusion layer at this stage, further, by heat treatment such as brazing the fin material to an aluminum flat tube produced in this way, aluminum
It has been found that the thickness of the Zn diffusion layer formed on the surface of the flat tube is prevented from becoming unnecessarily large, and the thickness of the flat aluminum tube can be prevented from decreasing during use of the product after the heat treatment.

[0006] The present invention has been made based on the above findings, and will be described in detail below with reference to the accompanying drawings.
FIG. 1 is a front view showing an embodiment for carrying out the method of the present invention.
In the figure, reference numeral 2 denotes an unwinding roll around which an aluminum (including an aluminum alloy) wire 4 is wound.
Reference numeral 6 denotes a shaping machine, reference numeral 8 denotes a conform extruder (hereinafter, referred to as “extruder”), and reference numeral 10 denotes a spray gun 12.
, A reference numeral 14 denotes a water tank, reference numeral 16 denotes a tension applying mechanism, and reference numeral 18 denotes a winding roller for winding the cooled aluminum flat tube 15c.

When manufacturing an aluminum flat tube for a heat exchanger, first, the aluminum wire 4 unwound from the unwinding roll 2 is shaped into a predetermined cross-sectional size by a shaper 6, and then the shaped aluminum wire is used. 4a is formed into a flat tube having a sectional shape shown in FIG. Extruder 8
Is basically a rotating wheel 2 with endless grooves.
0 and a fixed shoe 22.
A die 24 is provided at one end and the groove is closed. The aluminum wire 4a is formed into a predetermined cross-sectional shape from the die 24 by utilizing the pressure and frictional heat generated by the rotating wheel 20. It is designed to be extruded while being molded.

Next, a Zn spraying machine 10 is placed on the surface of the aluminum flat tube 15a extruded from the extruder 8.
Sprays Zn from the spray gun 12 to deposit a Zn layer. At this time, the temperature of the aluminum wire 4 fed from the unwinding roll 2 is normal temperature, and the exit temperature of the die 24 is 350
It is preferable that the temperature is from 400C to 400C.

The spraying gun 12 melts a Zn wire in a liquid state and sprays it in a mist form by air spray. The arrangement of the flattening tube 15a is, as shown in FIG. Are arranged one by one.

In place of spraying Zn wire by the above-mentioned spray gun 12, for example, an oxygen-acetylene flame
The powder may be sprayed on the outer surface of the flat tube 15a to adhere the Zn layer.

Next, the aluminum flat tube 15b immediately after the Zn layer is attached is inserted into a water tank 14 filled with cooling water, and is forcibly cooled. At this time, the flat tube 15b is rapidly cooled while being tensioned by the tension applying mechanism 16. The tension applying mechanism 16 includes free rollers 26 and 28
And a flat tube 1 provided between the rollers 26 and 28.
5c, and a tension roller 30 for applying tension by its own weight to 5c. By cooling the flat tube 15b while applying tension by the tension applying mechanism 16, deformation of the aluminum flat tube caused by uneven cooling can be effectively prevented.

After the flat tube 15b is cooled without applying tension,
In the case where the flat tube 15b is conveyed by passing over a free roller (a rotatably supported roller), the flat tube 15b is cooled to 320 ° C. or lower in the water tank 14. When cooled to 320 ° C. or lower, the Zn layer on the surface of the flat tube 15c is sufficiently solidified, so that the Zn layer does not drop when the flat tube 15c passes over the free roller. When the roller is fixed so as not to rotate, the flat tube 15b is
By cooling to 0 ° C. or less, the Zn layer can be prevented from being lost.

The flat tube 15c cooled as described above.
Heat treatment such as brazing a fin material to the outer surface of the aluminum flat tube to form a Zn diffusion layer on the surface of the aluminum flat tube. Aluminum flat tubes are manufactured. Since the Zn diffusion layer between the surface of the aluminum flat tube and the Zn layer is formed to a required thickness during the final heat treatment, the Zn diffusion layer is not formed to an excessive thickness, The later reduction in wall thickness of the aluminum flat tube surface portion is reliably prevented, and a reduction in the strength of the aluminum flat tube and generation of cracks are prevented.

[0014]

EXAMPLES Next, the effects will be demonstrated with reference to examples of the present invention. An aluminum wire rod (diameter: 15 mm) having the composition shown in Table 1 was warm-extruded by an extrusion molding apparatus at an extrusion speed of about 50 m / min using the same apparatus configuration as that shown in FIG. Under the following conditions, the extruded aluminum flat tube is continuously sprayed with Zn wire at a rate of 10 g / m ² , and 5 to 10 kgf is applied to the flat tube.
/ Cm ² , and rapidly cooled to 250 ° C. in a water bath. The cross-sectional shape of the obtained flat tube is as shown in FIG. 2, and the width is 22 mm, the height is 5 mm, the tube thickness is 0.6 mm, and the partition wall thickness is 0.4.
mm. After the cooled flat tube passed through the tension applying mechanism, it was wound up by a winding roller, but peeling of the Zn layer on the flat tube surface did not occur. Under the same conditions,
When cooling was performed without applying tension to the flat tube (changing only these conditions), a slight distortion due to cooling unevenness was confirmed in the cross-sectional shape of the flat tube, but this was not a problem for the product. It was.

[0015]

[Table 1]

On the outer surface of the flat tube thus obtained, fins formed of a brazing sheet having both surfaces coated with a brazing material were brazed under the conditions shown in Table 2, and as shown in FIG. A heat exchanger in which substantially fin-shaped fin materials 5 were fixed to the upper and lower surfaces of 15c was manufactured. The thickness of the Zn diffusion layer in the flat tube portion of the obtained heat exchanger is 50 μm to 70 μm.
μm, and it was confirmed that the aluminum flat tube after the formation of the Zn diffusion layer had sufficient thickness and strength.

[0017]

[Table 2]

[0018]

As described above, according to the method for manufacturing an aluminum flat tube for a heat exchanger according to the present invention, the Zn layer is missing even if the aluminum flat tube after forced cooling is conveyed through rollers or the like. Therefore, the handling cost and the workability can be improved, and the manufacturing cost can be reduced. Furthermore, there is no necessity of the thickness of the Zn diffusion layer formed on the surface portion of the aluminum flake pipe becomes excessively large, to prevent wall thickness reduction of the aluminum flake pipe after the thermal Aluminum
It is possible to prevent the occurrence of reduced strength and crack um flattened pipe. Further, by cooling the flat tube while applying tension, it is possible to effectively prevent deformation caused by uneven cooling.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment for carrying out the method of the present invention.

FIG. 2 is a view showing a cross-sectional shape of an aluminum flat tube.

FIG. 3 is a diagram showing an example of an arrangement of a Zn spraying gun with respect to a flat tube.

FIG. 4 is a partial front view of the heat exchanger.

[Explanation of symbols]

 2 Unwinding roller 6 Shaping machine 8 Conform extrusion molding machine 10 Thermal spraying machine 14 Water tank 16 Tension applying mechanism 18 Winding roller

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 4/00 C23C 10/00

Claims (4)

(57) [Claims] 1. A Zn layer is deposited on the outer surface of an aluminum flat tube immediately after warm extrusion by a spraying method of Zn wire or a spraying method of Zn powder, and thereafter, the aluminum flat tube to which the Zn layer is deposited is removed. forced cooling by rapidly cooled 320 ° C. or less, heat-treated aluminum flat tube the deposited the Zn layer after this, aluminum flake tube surface portion to form a Zn diffusion layer of the required thickness aluminum flake tube surface portion
A method for producing an aluminum flat tube for a heat exchanger, comprising: adhering a Zn layer to the aluminum tube. 2. The method for producing an aluminum flat tube for a heat exchanger according to claim 1, wherein the temperature of the aluminum flat tube immediately after the warm extrusion molding is 350 ° C. to 400 ° C. 3. The aluminum for a heat exchanger according to claim 1, wherein the heat treatment is performed by brazing a fin material to an outer surface of the aluminum flat tube to which the Zn layer is adhered. Manufacturing method of flat tube. 4. The forced cooling is performed while tension is applied to the aluminum flat tube.
Or the manufacturing method of the aluminum flat tube for heat exchangers of 3.