JPS58106397A - Production of heat-exchanging medium - Google Patents

Abstract

PURPOSE:To form a heat-exchanging medium without damaging an oxide film, by a method wherein an aluminum blank material is treated with a solution of a hypohalite to produce an oxide film on the surface thereof, is further treated with a solution of a silicate, and is worked. CONSTITUTION:An aluminum blank material is immersed into or sprayed with an aqueous solution containing at least one compound selected from the group consisting of, for example, hypochlorites and hypobromites of potassium, sodium and calcium to produce an oxide film on the surface of the blank material in a film thickness of, for example, about 2-10mg/dm<2>, desirably about 5-8mg/dm<2>. Then, the blank material is immersed into a solution of a silicate, for example, for about 5-60sec or is sprayed with the solution, and the solution is dried.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat exchange medium, in which aluminum or aluminum alloy material is treated with a hypohalite solution to form an oxide film, and then the oxide film is treated with a silicate solution. After that, the surface-treated material is subjected to forming processing such as draw press processing or drawless press processing, and then assembled, thereby producing a heat exchange medium with high production efficiency, that is, good processability and production yield, and at low cost. It is an object of the present invention to provide a method for manufacturing a heat exchange medium that can be easily manufactured and in which the heat exchange medium thus manufactured has excellent characteristics such as corrosion resistance and heat exchange efficiency.

BACKGROUND ART Conventionally, heat exchange media made of aluminum or aluminum alloy (hereinafter simply referred to as aluminum) have been provided with a surface treatment film on the aluminum surface in view of heat exchange efficiency and rust prevention. This surface treatment film is produced after the aluminum material is molded into fins of a predetermined shape and assembled, but this post-coat treatment method requires ■Due to the complex shape, it is difficult to process uniformly, resulting in poor appearance due to the formation of liquid pools, and furthermore, a decrease in heat exchange efficiency.■Do not use the treatment tank while the treatment liquid is still attached to the surface. Since the treatment solution is taken out from the fins, there are disadvantages such as a large amount of the treatment solution being removed and it is uneconomical. Therefore, it is not possible to form a surface treatment film on the aluminum material at a stage before forming and assembling the fins, that is, pre-coating. If so, it is preferable to perform surface treatment in advance.

In other words, the pre-coat treatment method is much easier than the post-coat treatment method, and the film formation is uniform.
For example, the pre-coat film is damaged during various molding processes such as overhang molding, burr molding, punching, or ironing using a press machine, reducing corrosion resistance and heat exchange efficiency, and furthermore, during molding. If the film is treated with, for example, a trichloride solution to remove the adhesion of press oil used during the processing process, there are disadvantages in that the water-repellent properties of the film are reduced and the heat exchange efficiency is also deteriorated. for example,
When pre-coating is performed by painting, molding of this pre-coated material not only results in cracks and damage to the flared parts, resulting in decreased corrosion resistance and thermal efficiency, but also extremely poor workability. Furthermore, there is a drawback that the coating layer may dissolve due to the triclene degreasing treatment performed after processing.Also, when pre-coating is performed by, for example, Pemite treatment, when this pre-coat material is molded, the Cracks occur, corrosion resistance and heat exchange efficiency are reduced, workability is poor, and the water-wet resistance of the boehmite film is significantly reduced due to trichlene degreasing treatment performed after processing.

The present invention eliminates the above-mentioned drawbacks, and examples thereof will be described below.

The method for producing a heat exchange medium according to the present invention is to place aluminum or an aluminum alloy material in an aqueous solution containing at least one compound selected from hypochlorites or hypobromites of potassium, sodium, and calcium. By immersing in or spraying this aqueous solution, the surface of the aluminum or aluminum alloy material can be coated with a film thickness of, for example, about 1 Orr@/dA, preferably about 5 to 5 s mg/dm.
After forming an oxide film, the aluminum or aluminum alloy material is post-treated by dipping or spraying it in a silicate solution for about 5 to 60 seconds, and then dried. A heat exchange medium is made by forming the material using draw press processing or drawless press processing.By doing this, a heat exchange medium with excellent corrosion resistance and heat exchange efficiency can be easily processed.
Moreover, it has become possible to manufacture it at low cost and with good manufacturing yield.

During this manufacturing process, the treatment with an aqueous hypochlorite solution in the pre-coat treatment process of the heat exchange medium material reduces the concentration of hypochlorite ions such as hypochlorite ions or hypobromite ions. If it is too high, the oxidizing power will be weak, and the corrosion resistance will not be very good.Furthermore, if the heat exchange medium is degreased with, for example, a trichloride solution after molding, the water wetting property will be significantly reduced, and vice versa. If the concentration of hypochlorite ions is too high, pitting may occur in the film, it will be difficult to obtain a uniform film thickness, and furthermore, water-wetting properties will decrease when degreasing with a trichloride solution, etc. Therefore, the hypohalite ion concentration is preferably about 200 to 300 (lppm, preferably about 200 to 800 ppm).

In addition, 1r of the solution during treatment with hypohalite aqueous solution
H is about 10-12, preferably about 10.2-11.4
It is desirable to adjust with sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. so that

Further, it is desirable that the liquid temperature during this treatment be about 25 to 100 u, preferably about 70 to 90[deg.] C., and the treatment time be about 1 to 20 minutes, preferably about 2 to 10 minutes. Furthermore, from the viewpoint of processability into fins, the thickness of the oxide film is approximately 2 to 10 cm.
/d is desirable.

Furthermore, the treatment with an aqueous silicate solution such as sodium silicate or potassium silicate that is performed after the treatment step with an aqueous hypohalite solution is different from the treatment when sealing an alumite film or MBV film. It does not act as a pore-sealing effect for the purpose of improving the corrosion resistance of the heat exchange medium, but acts as an anti-corrosion effect to prevent the water-wetting property of the film from decreasing during degreasing treatment with a trichloride solution, etc., which is performed after molding into a heat exchange medium. It can be easily processed. This means that several molecular layers of silicon dioxide and metal oxides in a solution containing alkali metal oxides and silicon dioxide, collectively known as silicates, are bonded to the surface of an oxide film formed by an aqueous hypohalite solution. Therefore, the treatment conditions with the silicate solution are such that the PpH of the solution is about 10 to 12, preferably about 10.5 to 11.
5 with a basic organic compound such as sodium hydroxide, potassium hydroxide, or alkylethanolamine, and the treatment temperature is approximately 25 to 100°C, preferably approximately 60 to 95°C, and the treatment time is takes about 5 to 60 seconds,
Preferably, it is about 20 to 45 seconds. For example, if the treatment time with an aqueous silicate solution is too long, the film becomes brittle during treatments such as pore sealing, and as a result, the workability of forming the material into a heat exchange medium decreases. On the other hand, if the treatment time is too short, the water wettability of the film surface will be reduced due to the fat treatment with a trichlene solution or the like, which is performed after the material is molded into a heat exchange medium or roted.

In addition, drying after silicate treatment is performed at 230℃ after washing with water.
It is desirable to dry at a temperature below, preferably about 100 to 150°C. This is because if the drying temperature is too low, the bond between the silicate and the oxide film will be insufficient, and if the drying temperature is too high, the mechanical properties of the material will change and it will not be possible to form it into a heat exchange medium. This is because processability deteriorates.

Next, specific examples of the present invention will be described.

Example I J I S 12QO-H26 aluminum alloy thin-walled wrought material (coil width 500 mm, coil length 3000 m,
:, thickness 0.110mm), temperature approx. 80~8
Ca(C[0)-aqueous solution (1 about 11.2, cto
After forming an oxide film with a thickness of about 8.0 mg per product on the surface of the wrought material by immersion treatment in a water glass solution (concentration of about 5 ooppm) for about 4 minutes, it is washed with water, and then soaked in a water glass solution (water glass solution with a temperature of about 95°C). Glass concentration xs, f' pH about 1 u) was immersed for about 45 seconds, followed by a shower followed by immersion washing, followed by drying at about 100° C. for 30 seconds.

After pre-coating the surface of the wrought material in this way, fins of a predetermined shape are formed by applying drawless press processing to the pre-coated wrought material, and after the processing step, the fins are subjected to Triclean degreasing treatment, and The oil adhering to the inside is removed, and finally the fins are assembled to form a heat exchanger with a small fin pitch.

Example 2 The same wrought material as in Example 1 was heated to Naf at a temperature of about 80 to 85°C.
Jj6 aqueous solution (11)H about 10.6~IQ, 8ρIQ concentration about zooppm) for about 3.5 minutes to form an oxide film with a thickness of about 6.0cm/ze on the surface, and then washed with water. Next, a water glass solution at a temperature of about 90°C (water glass concentration o
, s %, "rfH about 112) for about 30 seconds, followed by a shower, immersion washing, and then drying at about 100° C. for 30 seconds.

The wrought material that has been precoated as described above is subjected to the same molding process as in Example 1 to form fins, subjected to Triclene degreasing treatment, assembled into fins, and heated in the same manner as in Example 1. Configure the exchanger.

Example 3 Instead of the treatment with an aqueous solution of Ca(amO) in Example 1, the wrought material was treated with NaBr0 at a temperature of about 80 to 85°C.
After treatment with I solution (IH about 11.0 to 11.2, BrO concentration about 2 oppm) for about 4 minutes to form an oxide film about 6.51 mm thick on the surface of the wrought material, Example A heat exchanger is constructed in the same manner as in Step 1.

Example 4 Instead of the treatment with Ca (6Ae) and aqueous solution in Example 1, the wrought material was treated with a NaC-based O aqueous solution (pH about 10.8-11.0, ε breath O concentration about 800p
pm) for about 4 minutes, and about 8.5 nm was applied to the surface of the wrought material.
After forming an oxide film with a thickness of @/a+M, a heat exchanger is constructed in the same manner as in Example 1.

Example 5 Instead of the treatment with Ca(・ahω) and aqueous solution in Example 1, the wrought material was heated to a temperature of about 70 to 75°C QN a 61
The surface of the wrought material was treated with a Ql aqueous solution (?H about 10.8 to 11.0, εum O concentration about sooppm) for about 5 minutes to give about 7.
After forming an oxide film with a thickness of 0.01 cm, it was washed with water, and then the same treatment was performed using the water glass solution of Example 1 at a temperature of about 60°C. Configure.

Example 6 Hypochlorous acid in Example 5) The treatment temperature with the IJium aqueous solution was approximately 80 to 85°C, and the treatment time was approximately 3 minutes to form an oxide film of approximately 1, smg/product thickness on the surface of the wrought material. After that, it was washed with water, and then soaked in a water glass solution (water glass concentration 05%, ?H about 108) at a temperature of about 60°C for about 45 minutes.
Post-treatment is performed by dipping for a second, and then the same procedure as in Example 5 is carried out to construct a heat exchanger.

Example 7 What about the treatment with water glass solution in Example 6 with dimethylamine alcohol? Concentration approximately 0 adjusted to H approximately 11,0
．． A heat exchanger is constructed as in Example 6 using a 0.5% water glass solution at about 90° C. for about 30 seconds.

Example 8 The treatment with water glass solution in Example 6 was performed with dimethylamine alcohol! ! A heat exchanger is constructed in the same manner as in Example 6, using a water glass solution with a concentration of about 0.001 H adjusted to about 1098 H and heated at about 60° C. for about 60 seconds.

Comparative Example In step 9 of the treatment with the calcium hypochlorite aqueous solution in Example 1, the wrought material was treated with 0.5% ammonia water (pH approximately 105) at a temperature of approximately 95°C for approximately 3.5 minutes. Approximately 12. After forming an oxide film with a thickness of srng/rm, a heat exchanger is constructed in the same manner as in Example 1.

The heat exchange performance and corrosion resistance of the heat exchanger made as in the above example are extremely excellent, whereas the heat exchange performance and corrosion resistance of the heat exchanger made as in the comparative example are inferior. It was something. In particular, the heat exchanger used as a comparative example is
In the process of molding the precoat material into fins, for example, flaring occurs, the precoat film is damaged, and the corrosion resistance is significantly inferior.

This is clear from the scanning electron micrograph of the oxide film treated in Example 4 shown in FIG. 1 and the electron micrograph of the oxide film treated in Comparative Example shown in FIG. The oxide film of the present invention has a high density petal-shaped oxide film, and the oxide film is formed finely, making it a thin film with good workability and excellent corrosion resistance.

That is, when observing the surface of a fin obtained by applying drawless press processing to a material having such an oxide film treated with a silicate solution, for example, Example 4 shown in FIG.
Scanning electron micrograph of the surface of the fin of the fin and the fourth
As is clearer from the scanning electron micrograph of the surface of the ironed part of the fin of the comparative example shown in the figure 1, the pre-coated film of the present invention has almost no damage during the forming step 7110, whereas the pre-coated film of the comparative example has no damage. , large cracks were generated due to the engraving process, and as a result, the corrosion resistance was significantly inferior to that of the comparative example.

Furthermore, even if the precoated film of the heat exchange medium of the present invention is subjected to, for example, trichlene degreasing treatment after the fins are formed, the water wetting properties of the precoated film do not decrease significantly, making it possible to use a heat exchange medium with a small fin pitch. Even when assembled, no bridges due to water droplets are created between the fins, so ventilation resistance is not increased, the capacity of the fan is small, energy is saved, and running costs are also advantageous.

As mentioned above, the method for producing a heat exchange medium according to the present invention involves treating an aluminum or aluminum alloy material with a hypochlorite solution to form an oxide film on the surface, and then treating it with a lysinate solution. Then, this surface-treated aluminum or aluminum alloy material is molded, and the molded material is assembled to make a heat exchange medium, so the surface treatment is performed after the aluminum or aluminum alloy material is molded. It is much smoother, easier, and more efficient to produce heat exchange media at low cost than the production method that involves making heat exchange media using heat exchange media, and the surface treatment film will not be damaged even if it is molded after surface treatment. , it can be molded with good workability, and furthermore, the manufactured heat exchange medium has excellent heat exchange efficiency and corrosion resistance, and even if the fin pitch is small, water droplets will not adhere to it and form bridges. It has features such as low friction, low running cost, and no pollution problems in the treatment of waste liquid during manufacturing, that is, surface treatment process.

[Brief explanation of the drawing]

FIGS. 1 and 3 are scanning electron micrographs of the surface of the heat exchange medium according to the present invention before and after the molding process;
The figure and FIG. 4 are scanning electron micrographs of the surface of the heat exchange medium according to the comparative example before and after the molding process.

Claims (1)

[Claims] ■ After treating aluminum or an aluminum alloy material with a hypochlorite solution to form an oxide film on the surface, treating it with a silicate solution, and then applying the surface-treated aluminum or A heat exchange medium manufacturing method characterized by forming an aluminum alloy material and assembling the formed material to produce a heat exchange medium. ■The treatment with a silicate solution is such that several molecular layers of silicon dioxide are bonded to the surface of the oxide film.Claim 1
A method for producing a heat exchange medium as described in Section 1. (2) The method for producing a heat exchange medium according to claim 1 or 2, wherein the oxide film has a thickness of 2 to 1 oCam.