JP2661976B2 - Manufacturing method of zinc coated aluminum tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for producing a zinc-coated aluminum tube having excellent corrosion resistance used in a heat exchanger or the like by using a cold continuous forming machine.

(Prior art) Conventionally, a flat aluminum tube or a round aluminum tube for a heat exchanger is extruded by a hot extruder,
It was made into a coil by a winding device.

However, in this method, a seam is formed for each extruded buret, and air or oil infiltrates into the seam portion, and many defective portions, so-called blisters, are present. Therefore, it cannot be used for a heat exchanger as described above, which requires not only pressure resistance but also corrosion resistance, and the weight of the billet is increased more than necessary to obtain a coil having no defective portion. That is, there is usually one joint for each coil of 30 to 50 kg, and that portion cannot be used from the viewpoint of pressure resistance reliability and corrosion resistance, and was cut off.

Further, a method of improving the corrosion resistance of this aluminum tube has been proposed. For example, using an aluminum material as a metal extruded material as shown in JP-A-58-204169,
The Zn coating layer is formed by spraying Zn on the surface of the aluminum material near the extrusion port of a hot or cold extrusion molding machine.

However, even if a corrosion-resistant aluminum tube is manufactured by such a method, it is impossible to manufacture a coil using a long and seamless aluminum tube as described above.

In order to improve this, a method of manufacturing an aluminum tube using a recent cold continuous forming machine has been proposed.
For example, as shown in Japanese Patent Application Laid-Open No. 60-1087, a material such as aluminum is supplied into an elongated passage formed by a mandrel groove provided on the periphery of a movable wheel and a fixed cis-block engaged with the groove. The material is forcibly fed into the passage by the contact friction resistance between the inner surface of the groove of the rotating movable wheel and the material to generate an extrusion pressure on the material, and the extruded aluminum tube is manufactured through a die attached to the tip of the material. Is the way.

According to this method, a coil having a weight 10 to 20 times that of the method of manufacturing an aluminum tube by the hot extruder can be manufactured seamlessly.

However, in this method, the aluminum tube extruded from the cold continuous forming machine has a surface temperature of 200 mm.
Since the temperature is as low as about 400 ° C., Zn cannot be sufficiently diffused in spraying Zn on the surface, and the adhesion strength between the aluminum tube and Zn is poor.
It was not possible to achieve a sufficient purpose for providing a coating layer.

(Problems to be Solved by the Invention) In view of the present situation, the present invention has conducted intensive research, and as a result, has produced a seamless aluminum tube by a cold continuous forming machine, and has an anti-corrosion coating of Zn having excellent adhesion strength on the outer periphery thereof. A method for producing a Zn-coated aluminum tube having a layer was developed.

(Means for Solving the Problems) According to the present invention, an extruding die provided with a heating device and an inert gas injection pipe is introduced into a cold continuous molding machine attached to a tip end, and heated by the heating device. After extruding the aluminum wire through the extrusion die maintained at a high temperature and forming a high temperature and non-oxidized aluminum tube, spraying zinc powder on the outer circumference of the aluminum tube, a zinc diffusion layer and A method for producing a zinc-coated aluminum tube characterized by obtaining a zinc-coated aluminum tube sequentially coated with a zinc coating layer.

In the method of the present invention, as a cold continuous molding machine, for example, the one disclosed in JP-A-60-1087 as described above is used.

In the present invention, the aluminum tube is extruded as an aluminum tube from an extrusion die while being heated by a heating device provided at the end of the continuous molding machine, so that the aluminum tube is heated. Therefore, when coating the outer periphery with zinc, the zinc can diffuse into the aluminum tube and permeate. As a result, aluminum and zinc are alloyed, whereby the adhesion strength is improved and an excellent anticorrosion layer can be obtained.

The heating temperature of the die is preferably about 450 ° C to 550 ° C. The reason is that if the temperature is lower than 450 ° C, it is difficult to adhere zinc to the surface of the aluminum tube, and if the temperature exceeds 550 ° C. The reason for this is that the temperature of the material becomes too high, and roughening and seizure (pickup) occur in the material.

In addition, in the present invention, the reason why an inert gas such as nitrogen gas or argon gas is blown into the extrusion die is that the surface of the aluminum tube is easily oxidized because the temperature of the aluminum tube becomes high and the coating of zinc is hindered by the oxide film. Therefore, it is intended to prevent this oxidation.

In the present invention, aluminum includes an aluminum alloy in addition to pure aluminum, and zinc includes a zinc alloy, and the alloy has the same effect.

(Example) Example (1) As shown in FIG. 1, an aluminum wire (aluminum alloy JIS A 1050) 1 is introduced into a cold continuous forming machine 2. That is, the wire is fed into the groove of the wheel 4 via the coining roll 3, and while rotating the wheel, the frictional force causes the wheel to travel to the batch 5, and the wire is attached to the tip of the shoe 7 and the seal segment 8 by the extrusion die 6. The aluminum tube 9 was obtained by extrusion. In addition, 10 is a block.

That is, the extrusion die 6 is a die main body as shown in FIG.
11, the die ring 12 and the backer 13 are combined and a heating device such as a heater 14 is provided between the die body 11 and the die ring 12.
After adjusting the temperature of the die body 11 to 480 ° C. to 510 ° C., the aluminum material 1 was extruded as described above.

A nitrogen gas injection pipe 15 was attached to the die body 11, and nitrogen gas was blown into the die body 11 from the outside of the die at a pressure of 0.5 kg / cm ² .

In the above description, the reason why the die ring and the backer are attached to the die body 11 is to support the die body by providing the die ring, and to prevent the die body from being deformed by pressure by providing the backer. .

Thereafter, zinc powder is sprayed on the outer periphery of the aluminum tube 9 using a spraying device 16 under the spraying conditions shown in Table 1 to form a Zn coating layer 17 having a Zn diffusion layer 18 as shown in FIG.
Thus, a zinc-coated aluminum tube 19 for a heat exchanger of the present invention having a height of 5 mm, a thickness of 0.8 mm, and a width of 22 mm was obtained.

Comparative Example (1) An aluminum tube was prepared in the same manner as in Example (1) except that a die body 11, a die ring 12, and a backer 13 were combined instead of the extrusion die 6 in Example (1). I got it. Thereafter, zinc powder was sprayed on the outer circumference under the spraying conditions shown in Table 1 to obtain a zinc-coated aluminum tube 20 for a heat exchanger of a comparative example having a zinc coating layer 17 as shown in FIG.

The properties of the thus obtained zinc-coated aluminum tube of the present invention and the zinc-coated aluminum tube of the comparative example were measured. The results are as shown in Table 2.

Example (2) A round aluminum alloy tube was formed using a continuous extruder similar to that of Example (1) using JIS A 3003 aluminum alloy strands, and then processed in the same manner as in Example (1). Thus, a zinc-coated aluminum tube of the present invention having an outer diameter of 16 mm and a wall thickness of 1.2 mm was obtained.

Comparative Example (2) A round aluminum alloy tube was formed in the same manner as in Comparative Example (1) using JIS A 3003 aluminum alloy wire, and then coated with zinc in the same manner as in Comparative Example (1). A zinc coated aluminum tube was obtained.

The properties of the zinc-coated aluminum alloy tube of the present invention thus obtained in Example (2) and the zinc-coated aluminum alloy tube of Comparative Example (2) were measured. The results are as shown in Table 3.

As is clear from Tables 2 and 3, the adhesion weight of Zn is almost the same for both the product of the present invention and the comparative product. However, since the temperature of the aluminum tube is low, almost no zinc is deposited under the surface of the aluminum tube. Is not diffused, so that the Zn anticorrosive layer peels off during the U-bent bending. This clearly shows that the pitting corrosion is four times or more as compared with the product of the present invention, as is apparent from the corrosion resistance casting test. That is, in the conventional product, Zn is not diffused into aluminum, so that aluminum is corroded within a short time after Zn is corroded. On the other hand, in the present invention, since Zn is diffused deeply into aluminum, an alloy layer of both is formed, and Zn does not peel off even during bending, and exhibits excellent corrosion resistance.

(Effects of the Invention) As described above in detail, according to the method of the present invention, since the aluminum tube and the Zn anticorrosion layer are alloyed and adhered to each other, they have excellent corrosion resistance and can produce a seamless aluminum tube. Extremely useful.

[Brief description of the drawings]

FIG. 1 is a schematic illustration of a method for producing an aluminum tube by a conventional continuous extruder, FIG. 2 is a schematic illustration of a die mounted on a continuous extruder used in the method of the present invention, and FIG. 3 is a method of the present invention. FIG. 4 is a perspective view of a zinc-coated aluminum tube obtained by the method of Comparative Example. 1 ... aluminum strand, 2 ... cold continuous forming machine, 3 ...
... Coining rolls, 4 ... Wheels, 5 ... Abatchments, 6 ... Extrusion dies, 7 ... Shoes, 8 ...
Seal segment, 9 ... aluminum tube, 10 ...
… Block, 11… Dice body, 12… Die ring, 13
... backer, 14 ... heating device, 15 ... nitrogen gas blowing tube, 16 ... thermal spraying device, 17 ... zinc coating layer, 18 ... zinc diffusion layer, 19 ... zinc coated aluminum tube of the present invention, 20
...... Comparative example zinc coated aluminum tube.

Claims (1)

(57) [Claims] 1. An aluminum wire is introduced into a cold continuous forming machine in which an extruding die provided with a heating device and an inert gas injection pipe is attached to a tip end thereof. The aluminum wire is extruded through the extrusion die maintained at a high temperature to form a non-oxidized aluminum tube at a high temperature, and then a zinc powder is sprayed on an outer periphery of the aluminum tube to form a zinc diffusion layer and a zinc coating. A method for producing a zinc-coated aluminum tube, comprising obtaining a zinc-coated aluminum tube sequentially coated with layers.