JPS5839796A - Hard anodizing method for inside surface of pipe - Google Patents

Abstract

PURPOSE:To form hard anodized films uniformly on the inside surfaces of Al pipes by circulting and passing a cooled electrolyte in the bores of the pipes immersed in a treating tank from one to the other and maintaining the temp. of the electrolyte interposed on the inside surfaces of the pipes as desired. CONSTITUTION:Pipes W made of an Al alloy ae disposed upright in parallel in the electrolyte L of an anodizing tank T, and are anodized. The electrolyte L is circulated between the tank T and a heat exchanger H. The electrolyte L cooled in the heat exchanger H is discharged through the discharge ports A of discharge pipes P to the center at the bottom ends of the pipes W, flow upward in the pipes W and flow out from the top ends thereof. The heat of electrolysis generated in the inside surfaces of the pipes W is thoroughly removed, and the temp. of the electrolyte interposing in the pipes W is maintained always at a desired temp. By such method, hard anodized films are formed easily and uniformly on the inside surfaces of the Al alloy pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hard anodic oxidation treatment method for forming a hard anodic oxide film layer of uniform thickness on the inner surface of an aluminum alloy pipe.

Conventionally, in the case of this type of anodizing treatment, the method of removing the electrolytic heat generated during the anodizing treatment was to lead the electrolytic solution for anodizing treatment outside the anodizing treatment tank, cool it, and then restart the anodizing treatment. Methods such as circulating the electrolyte so that it flows into the tank or stirring the electrolyte by blowing air into the treatment tank have been adopted, but in either case, the inner surface of the pipe to be treated is , because the generated electrolytic heat is not removed sufficiently, the temperature of the electrolytic solution is approximately 23 to 25 degrees.
C, it was not possible to maintain the desired temperature of approximately 10°C, and as a result, it was not satisfactory to form a hard and uniformly thick anodic oxide film layer on the inner surface of the pipe. Ta.

The present invention compensates for such conventional drawbacks and maintains the temperature of the electrolytic solution present on the inner surface of the pipe at the desired temperature, so that the hardness of the generally obtained anodic oxide film layer (approximately HV2
Extremely hard (HV450-55) far exceeding
0), and is characterized in that an anodic oxide film layer of uniform thickness is formed on the inner surface of the pipe.

Hereinafter, one embodiment of the present invention will be described based on the drawings. T is an anodizing treatment tank, L is an anodizing electrolyte stored in the treatment tank T, and H is a heat exchanger installed outside the treatment tank T. Further, W is an aluminum alloy pipe to be treated, and a plurality of pipes are immersed in an electrolytic solution L in an upright parallel arrangement, and pole rods E are respectively inserted into the inner surface of the pipe W, and the ends of each pipe are Connect to power source (not shown).

Further, P is a pipe-shaped blow-off pipe having a diameter smaller than the diameter of the pipe W, and the upper discharge port A thereof is located close to the center of the lower end of the pipe W, and is disposed vertically at the bottom of the processing tank T. B is connected to the outlet 0 of the heat exchanger H, while the inlet I of the heat exchanger H is connected to the outlet C formed at the upper part of the processing tank T. Note that M indicates a fluid pump.

However, when a series of anodizing treatment facilities for the pipe W having the above-described configuration are operated, the electrolyte L is transferred to the treatment tank T.
and the heat exchanger H in the direction shown by the arrow in the figure, and during this time the electrolytic solution L, which was forced to rise in temperature due to the electrolytic heat generated in the anodizing process in the treatment tank T, is cooled. It goes without saying that it is well known that the average temperature of the electrolyte in the treatment tank T can be maintained at a certain predetermined temperature.

By the way, considering the above-mentioned positional relationship between the pipe W and the discharge pipe P, the electrolyte L cooled by the heat exchanger H is directly discharged from the discharge port A of the discharge pipe P to the center of the lower end of the pipe W. This is inevitable, and the liquid then flows upward along the inner surface of the pipe W, and then flows out from the upper end of the pipe W. During that time, the electrolytic heat generated on the inner surface of the pipe W is sufficiently removed so that the temperature of the electrolyte L present on the inner surface of the pipe W is always maintained at approximately the desired temperature (approximately 10° C. as described above). will be realized. As a result, it can be expected that the anodic oxide film layer formed on the phase surface of the pipe W is hard at HV450 to 550 as described above, and has a uniform thickness.

As described above, by circulating the cooled electrolyte L from one side of the inner surface of the pipe W to the other, it is possible to maintain the temperature of the electrolyte L present on the inner surface of the pipe W at approximately a desired temperature. This is the gist of the invention.

In addition, in the method of circulating and flowing the cooled electrolytic solution L to the inner surface of the pipe W, it goes without saying that configurations and methods other than those of the above-mentioned embodiments fall within the scope of the present invention.

As described above, the present invention uses an extremely simple method and equipment to uniformly form a hard anodic oxide film layer on the inner surface of an aluminum alloy pipe, and can be said to be an ideal treatment method. .

[Brief explanation of drawings]

The drawing is an explanatory diagram showing a partially vertical end face of an embodiment of the present invention. L... Electrolyte for anodizing treatment, T... Anodizing treatment tank,
W...Aluminum alloy pipe. Patent applicant: Tetsuro Hasegawa, representative of Sanko Aluminum Co., Ltd.

Claims (1)

[Claims] When forming a hard anodic oxide film layer on the inner surface of an aluminum alloy pipe, electrolytic heat generated on the inner surface of the pipe immersed in the anodizing electrolyte stored in the anodizing tank The electrolytic solution cooled outside the treatment tank is passed through the inner surface from one end of the pipe to the other end so that the temperature of the electrolytic solution interposed on the inner surface of the pipe is maintained at approximately the desired temperature by constantly removing the electrolytic solution. A hard anodizing treatment method for the inner surface of a pipe, characterized in that the pipe is made to circulate and flow.