JPS61110795A - Anodically oxidizing method of aluminum material - Google Patents

Abstract

PURPOSE:To form hard oxidized film having no burn in a short time, by measur ing temp. of an Al material, and stopping or starting electricity conduction in cases a prescribed value is exceeded or turned back respectively, and repeating this. CONSTITUTION:The Al material 1 pretreated by conventional method, and an opposing electrode 2 are dipped in electrolytic bath in an electrolytic cell 8, DC current is impressed to each of them from a programmable DC source 6 to oxidize the material anodically. A thermocouple 3 is attached to the mate rial 1 to measure the temp. thereof, and the measured value is sent to a micro computer 5 through a multichannel and digital multimeter 4. Electricity conduc tion from the source 6 is stopped by the computer 5 if the measured value exceeds a prescribed value, and started if the returns to said value. The opera tion is repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming an anodic oxide film on an aluminum material in a short time, and in particular, a method for electrolyzing at a high voltage or high current density, and that does not cause burns on the oxide film. The present invention relates to a method for forming a hard anodic oxide film that does not bleed.

Conventional technology Aluminum or aluminum alloy (under μ).

When aluminum material and IIATI are anodized at high voltage or high current density, a hard oxide film can be formed in a short time. This is the essence of the high-speed alumite method and hard alumite method. However, when high-voltage electrolysis is carried out using the normal method, "burning" occurs on the surface of the film due to the Joule heat of the electrolytic current, so in order to prevent this burning, pulse electrolysis
) Special electrolysis methods such as Den II, shower electrolysis, and bubble electrolysis have been patented. In principle, all of these RIJs are designed to effectively release Joule heat from the aluminum sample.

Interlayer point to be solved by the invention In the conventional pulsed electrolytic alumite method, the on-time and off-time of the pulse of electrolytic voltage or electrolytic current are determined in advance. At this time, if the off time is too short, heat will not be diffused sufficiently from the sample surface, and if the off time is too long, heat will be sufficiently diffused from the sample surface, but the total There is a risk that the electrolysis time will become longer and the production efficiency of alumite formation will decrease, or that the alumite film will be chemically dissolved and become weak alumite.

Also, if pulse electrolysis is on and off.

Even if the time is set correctly, the bath temperature changes.

Because the Joule heat generation situation changes due to bath deterioration, changes in sample charge, etc., the previously set pulse on/off time is no longer an appropriate cycle.

Means for Solving the Problems The present invention takes into account the drawbacks of the pulse electrolysis method described above, and provides a method that is not affected by the conditions of the electrolytic bath by dissipating heat from the surface of the sample in a necessary and sufficient manner. , provides a method for effectively obtaining a hard oxide film.

The anodic oxidation method for aluminum material according to the present invention is a method for forming an anodized film on an aluminum material pretreated by a conventional method, in which the temperature of the aluminum material is measured and when the temperature exceeds a set value, the energization is stopped; The feature is that when the set value is returned, the energization is restarted and this operation is repeated.

That is, the temperature of the aluminum material is constantly monitored, and if the temperature of the aluminum material rises outside the set range, the power supply is stopped. Then, when the temperature of the aluminum material falls within the set range, energization is restarted.

The ffi degree of the electrolytic bath only needs to be lower than the set temperature of the aluminum material, and for example, the bath temperature can be controlled with precision such as "20°C or less", and the bath temperature does not need to be precisely controlled.

By repeating this operation and electrolyzing the aluminum material at high voltage or high current density so that the total of one normal time is a predetermined time, the temperature rise of the aluminum material is suppressed and the desired temperature is reached without causing burns. A thick, high-quality oxide film can be created in a short time.

For example, methods for measuring the temperature of aluminum materials include:
The temperature of aluminum materials can be measured by directly attaching a flat thermocouple to the aluminum material, by measuring the surface temperature of the aluminum material using infrared Wflffff, or by applying the electrical low loss measurement method as an indirect method. In a small model, there is almost no seat on any part of the aluminum material, so the thermocouple is sealed in one place, for example, on the aluminum material in the upper part of the bath, and on the aluminum material in the middle of the bath. Alternatively, the temperature set point can be set near the surface of the aluminum material using infrared rays such as 111 mNm in a bath.

In addition, in the case of large plates and shapes, it is possible to set the I1 degree setting point at several locations, and by measuring the temperature at multiple points, the passage S can be stopped when the temperature at any location exceeds the set temperature.

As the aluminum material, in addition to pure aluminum, aluminum alloy materials that are usually subjected to anodizing treatment, such as 52
It can be applied to 8.6063 shapes, various aluminum alloy materials, etc.

Also, examples of electrolytic baths include sulfuric acid bath and oxalic acid bath.

It can be applied to electrolytic baths such as chromic acid baths, which are usually used for forming anodic oxide films.

It also monitors the temperature of aluminum materials and turns on/off electricity.
It can be turned off manually, but it can also be turned off automatically using a micro combinator or the like. While the conventional pulse electrolysis method uses "sequential +5 m fixed frequency pulses", the present invention can be said to be an anodizing method for aluminum materials using "feedback controlled variable frequency pulses".

Function The function of the method of the present invention is explained in relation to the electrolysis time and the aluminum material as shown in Fig. 1.

When electricity starts, the temperature of the aluminum material rises, and when it reaches the set temperature, the current is cut off. However, due to the heat capacity of the aluminum material, it continues to rise against the bath temperature, but eventually it is cooled by the electrolytic bath and the lower fermentation occurs. Turned to

Finally, the set temperature is reached and the electricity is turned on again, but...
The temperature continues to decrease, eventually starts to increase, reaches the set temperature, and the current is cut off. This process is repeated thereafter at 0 energization time t.
on, power outage time t. ff changes depending on the electrolytic conditions, and the difference between the set temperature and the highest temperature Δ The difference between the upper film constant temperature and the lowest temperature Δτ depends on the heat capacity of the test sample 0 Under normal electrolytic conditions, 1 For example, the set temperature 21 If it is ℃ + joo +
joff is.

Each time is about 1 second, and ΔT and Δτ are about α5°C to Lθ°C.

In addition, the applied voltage is 10 to 25 V, and the 1B current density is α3 to IO.
It can be applied up to A/dm and the thickness of the oxide film can be up to several tens of μm.

The method of the present invention will be further explained below with reference to Examples.

Example Purity 9 to 5% A1 aluminum plate (l Q am
A 20 cm x α3 mm 1 piece was anodized in 15% aqueous sulfuric acid. At this time, a flat Almelo-Chromel thermocouple was attached to the top of the aluminum sample using cellophane tape.

Input the thermocouple output voltage into a digital multimeter,
This digital symbol was input into the microcomputer from the GP-IB bus. This microcontroller was also connected to a programmable DC power supply using the GP-IB path. When the temperature of the thermocouple reaches the set temperature of the aluminum material, the DC power is turned off based on the judgment of the microcomputer, and when the temperature of the thermocouple becomes lower than the set temperature, the DC power is turned on. A block diagram of this experimental equipment with the program is shown in Figure WL2.

In the figure, 1 is an aluminum material, 2 is a counter electrode, 3 is a thermocouple, 4 is a multi-channel digital multimeter, 5 is a microcomputer, 6 is a programmable DC power supply, 7
T indicates a pen recorder, and 8 indicates an electrolytic cell.

In the @2 device, bath! 118℃, setting 11 degrees 22℃
When an aluminum material was anodized under electrolytic conditions with a bath voltage of 23 Volt and a required time of 10 minutes, the oxide film thickness was 30 μm, the JIS alkali resistance test was over 1000 seconds, and the Hssm type abrasion test was over 60 minutes. DC electrolysis and pulsed electrolysis (t6
When pulse electrolysis (++=1 second, toff:=1 second) was attempted, current concentration occurred on the aluminum material sample in both electrolysis cases, making it impossible to form a uniform oxide film.

Effects of the Invention According to the method of the present invention, as shown in the examples, it is possible to form a hard, non-scorching oxide film in a short period of time, whereas in the Hiba example, the oxide film is soft and does not cause any burns. Also, the electrolysis time is extremely long to avoid burning.

That is, according to the method of the present invention, a hard, non-scorching oxide film can be formed in a short time, thereby increasing productivity and can be said to be an excellent industrial invention.

Note that the method of the present invention is based on P R (Periodic R
(Everse) It can also be applied to electrolysis.

E. During anodizing, the temperature of the aluminum material rises, and if the cathode voltage is applied when it reaches the set temperature, and the anode voltage is applied when the temperature drops to the set temperature, the feed pack separation can be improved. PR electrolysis can be performed by the department.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the temperature of aluminum material and electrolysis time in the method of the present invention, and FIG. FIG. 4 is a block diagram. 1... Aluminum material, 3... Thermocouple. 4...Digital multimeter, 5...Microcomputer, 6...Programmable DC power supply.

Claims (1)

[Claims] 1. In the method of forming an anodic oxide film on aluminum material that has been pretreated using a conventional method, the temperature of the aluminum material is measured, and when it exceeds the set value, the energization is stopped, and when it returns to the set value, the energization is restarted. , an anodizing method for aluminum materials, which is characterized by repeating this operation.