JPH01208697A - Surface treated aluminum thin sheet for plate fin of heat exchanger - Google Patents

Abstract

PURPOSE:To provide the title sheet with hydrophilic nature without any abrasion by a tool upon drawless forming, by a method wherein an all organic hydrophilic film is applied on one side of the aluminum thin sheet for plate fins while another hydrophilic film, containing either one kind of colloidal silica and silicate, is applied on the other side of the same sheet. CONSTITUTION:A hydrophilic film, containing colloidal silica or silicate, is more prominent in hydrophilic nature than the hydrophilic film of all organic type and reduces the production of bridges 5 due to dew water in the core of a heat exchanger consisting of thin sheets 1 and copper tubes 6, however, abrasion is generated by a tool. The hydrophilic film 4 of all organic type is arranged on one side of the sheet as a countermeasure therefor, whereby lubrication on a surface, contacting with an ironing punch 3, may become favorable. The all organic type hydrophilic film, such as acrylic resin, polyvinyl alcohol resin coating or the like is preferable to have the thickness of the film of 0.05-2.5mum and the dynamic frictional coefficient of 0.6 or less.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an aluminum plate fin used in a heat exchanger, and more specifically, to a plate fin material formed by a draw or drawless method. , concerning aluminum surface-treated thin sheets used in air conditioner evaporators and condensers.

(Prior art, problem to be solved) Aluminum plates 1 to fin materials used in heat exchangers such as room air conditioners have traditionally been surface-treated to prevent corrosion. Add hydrophilicity to the film to reduce ventilation resistance.

There is an increasing demand for functions such as reducing noise and improving defrosting efficiency in the outdoor units of Bee 1 pumps.

Conventional hydrophilic surface treatment techniques include: ■ Play 1 - Applying a chemical mixture of acrylic resin and surfactant to both sides of the fin, ■ Applying a chemical mixture of acrylic resin and colloidal silica, and l ■ Silicic acid. Salt-based treatment methods, boehmite treatment methods, etc. have been announced, but each has advantages and disadvantages.

That is, the method (2) in which a surfactant is mixed with the acrylic resin does not cause the problem of tool wear when applied to a fin material for draw or drawless molding, but does not have sufficient hydrophilicity. On the other hand, other treatment methods containing inorganic substances have relatively good hydrophilicity, but have drawbacks such as tool wear, especially in drawless molding, and special consideration is required in selecting the tool material.

In this way, surface-treated plate fin materials treated using conventional methods cannot necessarily be said to be satisfactory in terms of both hydrophilicity and tool wear, and further improvements are desired for the same applications. It has been done.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a surface-treated aluminum thin plate that has excellent hydrophilicity and is free from the problem of tool wear for use as a heat exchanger plate fin material.

(Means for Solving the Problems) In order to achieve the above object, the present inventors developed a conventional method in view of the fact that the forming method used for this type of application has different effects on both sides of an aluminum plate fin thin plate. It has been found that the hydrophilic surface treatment method cannot sufficiently impart the above characteristics to both surfaces. Therefore, as a result of intensive research into a method of applying a different method to each side, the present invention has been made.

That is, the aluminum surface-treated thin plate for heat exchanger plate fins according to the present invention has an all-organic type hydrophilic coating applied to one side and a hydrophilic coating containing one of colloidal silica and silicate applied to the other side. This is a summary of what was done.

The present invention will be explained in more detail below.

(effect) Drawless molding of heat exchanger plate fins.

As shown in Fig. 1, a thin aluminum plate 1 is first set in a forming machine (A), then pierced and burred (B), then ironed (C), and then flared (D). ). In this case, the ironing process (C) may be performed in two or more times, but the ironing punch 3
However, it is easily damaged during continuous processing of drawless molding.

This tendency is also the same in draw molding.

The present inventor believes that although it is necessary for both the surface of the thin aluminum plate 1 in contact with the ironing punch 3 and other surfaces to have hydrophilic properties, tool wear only occurs on the surface in contact with the ironing punch 3 in drawless or draw forming. This method focuses on the fact that it is sufficient to take measures, and as a countermeasure, by disposing an all-organic hydrophilic film 4 on one side (see Figure 2), the surface in contact with the ironing punch 3 is lubricated. This made it possible to gain an advantage.

For the all-organic type hydrophilic film, there are no particular restrictions on the organic material or film formation method. Examples include those coated with an acrylic resin paint containing a surfactant, those coated with a polyvinyl alcohol resin (PVA) paint, or two coated with an acrylic resin paint and a polyvinyl alcohol resin (PVA) paint. It is also possible to apply it in two or more layers like a layered film.

Note that this all-organic hydrophilic film has a film thickness of 0,
05 to 2.5 μm and a dynamic friction coefficient of 0.6 or less. It is preferable that the motion friction coefficient is 0.6 or less because it will further prevent the effect on tool wear, but if the film thickness exceeds 2.5 μm, not only will the effect be saturated, but it will also cause damage to the tool. Since there is a risk of build-up, the film thickness is preferably 2.5 μm or less.
．． If it is less than 0.05 μm, it is not preferable because it tends to become non-uniform and both hydrophilicity and lubricity are likely to decrease.

Further, the other surface of the thin aluminum plate 1 is coated with a film having excellent hydrophilic properties, that is, a film containing one of colloidal silica and silicate.
The reason is as follows.

A hydrophilic film containing colloidal silica or a silicate has better hydrophilicity than an all-organic type hydrophilic film, and as shown in Fig. 3, the formation of bliner 5 due to dew condensation in the heat exchanger core. can be reduced.

When a hydrophilic film containing colloidal silica or silicate is applied to both surfaces, both surfaces have excellent hydrophilicity, but the problem of tool wear occurs on the surface in contact with the tool.

In addition, the hydrophilicity obtained by applying an all-organic type hydrophilic film on both sides becomes insufficient, resulting in the problem of the formation of blister as described above. Even if a coating is not applied to both sides, the formation of bridges can be effectively reduced when only one side is treated.

The thickness of the hydrophilic coating containing colloidal silica or silicate is not particularly limited, and may be the same as the thickness of conventional coatings of this type.

Next, examples of the present invention will be shown.

(Example) Aluminum thin plate strip (JISIloo, H2S, 0.1
After degreasing with alkali and washing with water, surface treatments were carried out under various conditions shown in Table 1.

Next, each surface treated material was formed into a drawless mold (fin pitch: 1.4 mm) L, and as shown in FIG. 3, copper tubes 6 were inserted to assemble a heat exchanger core.

The evaluation results for hydrophilicity and tool wear resistance are also listed in Table 1.

Note that tool wear resistance was evaluated by comparing and investigating the degree of damage to tool steel ironing punches. Hydrophilicity was determined by degreasing the core using trichlorethylene, installing it in an atmosphere with a relative humidity of 40°C and 90%, and flowing water at 20'C through the copper tube 6 (see Figure 3). Evaluation was made by observing the wA of dew condensation water generated on the plate fin surface.

From Table 1, it can be seen that all of the invention examples Nu 3 to Nα6 have good hydrophilicity and have no effect on tool wear. On the other hand, Comparative Examples Nα1 and Nα2 particularly have a problem with tool wear, and Comparative Example 7 has a problem with hydrophilicity.

[Blank below] (Effects of the invention) As detailed above, the aluminum surface-treated thin plate for heat exchanger plate fins according to the present invention has hydrophilic coatings with different properties on both sides, so it has both hydrophilic and hydrophilic properties. Both effects on tool wear are good.

It is particularly useful as a plate fin for air conditioners such as room air conditioners.

[Brief explanation of the drawing]

Figures 1 (A) to (D) are explanatory diagrams showing the drawless forming process of plate fins, Figure 2 is a diagram explaining the ironing process for an aluminum surface-treated thin plate according to the present invention, and Figure 3 is a diagram showing the heat exchanger. FIG. 2 is an explanatory diagram showing how blister occurs in the core due to dew condensation water. 1... Aluminum thin plate, 2... Support tool, 3... Ironing punch, 4... All-organic type hydrophilic film. 5...Bridge, 6...Copper tube. Patent applicant Takashi Nakamura, Patent attorney representing Kobe Steel, Ltd. Figure 1 (B), n Figure 2 Figure 3

Claims (2)

[Claims] (1) An aluminum plate-fin thin plate used in a heat exchanger has an all-organic hydrophilic coating on one side and a hydrophilic coating containing colloidal silica and one type of silicate on the other side. An aluminum surface-treated thin plate for heat exchanger plate fins. (2) The all-organic hydrophilic film applied to one side has a thickness of 0.05 to 2.5 μm and a coefficient of dynamic friction of 0.
．． 2. The aluminum surface-treated thin sheet for heat exchanger plate fins according to claim 1, which has a surface-treated aluminum sheet of 6 or less.