JP7069843B2 - Manufacturing method of aluminum parts - Google Patents

Description

The present invention relates to a method for manufacturing an aluminum component having an anodic oxide film formed on its surface.

Conventionally, an anodic oxide film has been formed on an aluminum component (see, for example, Patent Document 1).

It is known that the anodic oxide film formed on an aluminum component is excellent in properties such as corrosion resistance, wear resistance, hardness, and insulating property.

JP-A-2015-102111 (Claims, etc.)

Although the anodic oxide film has excellent properties, long-term treatment (about 20 to 60 minutes) is required to form the anodic oxide film on the surface of the rough material. Since the formation of the anodic oxide film is proportional to the amount of current flowing, it is necessary to improve the current density in order to improve the formation rate of the anodic oxide film and shorten the processing time.

However, if the current density is simply increased and the anodic oxidation treatment is performed, the ductility of the obtained anodic oxide film becomes low and cracks may occur due to external force, and high-pressure gas flows in and high stress is applied to parts and parts. If an anodized film is formed on a part used in a high temperature environment, it may cause breakage.

The present invention has been completed in view of the above circumstances, and it is an object to be solved to provide a method for manufacturing an aluminum component capable of forming an anodized film in which cracks are unlikely to occur even if the speed of anodizing treatment is increased.

(1. Manufacturing method of aluminum parts)
As a result of diligent studies for the purpose of solving the above problems, the present inventors decided on the cell size of the anodic oxide film formed in order to determine whether or not cracks are likely to occur in the anodic oxide film formed on the surface of the rough material. I came up with the idea that I should pay attention to it. From the results of the examples described later, it can be seen that the cell size formed in the anodic oxide film increases as the applied voltage increases, and the cell size can be reduced to 40 nm or less by further reducing the applied voltage to 18 V or less. It was found that it became possible and the formation of cracks could be suppressed. Based on these findings, the following invention was completed. The "cell size of the anodic oxide film" in the present specification means the distance of 703 micropores in the adjacent 702 film cell based on the 701 schematic diagram of JIS H0201: 1998.

That is, in the method for manufacturing an aluminum component according to the present invention, a crude material made of aluminum or an aluminum alloy and to be treated is used as an anode, and a cathode and an electrolytic solution having a sulfuric acid concentration of 150 g / L to 300 g / L are brought into contact with each other to generate an electric current. A current is passed between the anode and the cathode under constant voltage conditions where the density is 0.8 A / dm ² to 7.5 A / dm ² and the applied voltage is 13 V or more and 18 V or less (excluding 15 V or less) . An anodic oxide film having a cell size of 40 nm or less is generated, an integrated value of the current flowing between the anode and the cathode is calculated, and the formed thickness of the anodic oxide film calculated based on the calculated integrated value is predetermined. By terminating the treatment when the value is reached, the anodic oxide film having a predetermined thickness is formed, and an aluminum component in which cracks do not occur when heat-treated at 165 ° C. for 1 hour is manufactured.

Even if the current density is increased in the anodic oxidation treatment to improve the formation rate of the anodic oxide film, the formation of cracks can be suppressed by setting the applied voltage to 18 V or less and keeping the cell size of the anodic oxide film below a certain level. Is now possible. In particular, the cell size could be stabilized by processing at a constant voltage.

It is a schematic diagram which shows the manufacturing apparatus of the aluminum part in an embodiment. It is a graph which showed the time-dependent change of the electric current at the time of carrying out the manufacturing method of the aluminum part in an Example. It is a graph which showed the correlation between the integral value of the electric current which flowed between an anode and a cathode, and the thickness of the generated anodized film.

(1. First Embodiment: Manufacturing method of aluminum parts)
(1-1. Configuration)
The method for manufacturing the aluminum parts of the present embodiment will be described below. In the method for manufacturing aluminum parts of the present embodiment, a crude material made of aluminum or an aluminum alloy is subjected to anodizing treatment in an electrolytic solution containing sulfuric acid as a target to be treated, and an anodizing film is formed on the surface of the material. This is a method of using aluminum parts. The material constituting the crude material is aluminum or an aluminum alloy, and the aluminum alloy is not particularly limited as long as it contains an aluminum element as a main component. Further, it is sufficient as long as it has a structure in which aluminum or an aluminum alloy is exposed on the surface of the rough material, and the material forming the inside is not particularly limited.

Since an anodic oxide film that is unlikely to crack due to external force can be formed as an aluminum component, it can be applied to any product component, but it is particularly preferable to apply it to a component to which a large external force is applied. .. For example, a valve body applied to high pressure gas.

The present manufacturing method includes a first step, a second step, and other necessary steps.
The first step is a step in which the crude material to be treated is used as an anode and is brought into contact with the electrolytic solution together with the cathode. The electrolytic solution contains sulfuric acid. Preferred conditions for the electrolytic solution will be described later. The contact with the electrolytic solution may be performed, for example, by immersing the crude material in the electrolytic solution. The cathode is not particularly limited.

The second step is a step of performing anodizing treatment by passing a current between the anode and the cathode under constant voltage conditions where the current density is 0.8 A / dm ² to 7.5 A / dm ² and the applied voltage is 18 V or less. ..

It is preferable that the current density is as high as possible because the rate at which the anodic oxide film is formed increases when the current density is equal to or higher than this lower limit. Further, when the current density is set to the upper limit or less, "film burning" does not occur in the anodic oxide film formed. It can be inferred that "film burning" occurs when the current does not flow uniformly due to the high current density and is concentrated in a part of the film. The characteristics of the anodized film obtained are not sufficient.

As a method of controlling the current density, it can be realized by adopting an appropriate electrolytic solution. An appropriate electrolytic solution is an electrolytic solution adjusted to have a resistance value within the range of the above-mentioned current density. The resistance value can be adjusted by controlling the sulfuric acid concentration and temperature of the electrolytic solution. By increasing the sulfuric acid concentration and temperature, the resistance value can be reduced and the current density can be increased. As for the concentration in the electrolytic solution, the concentration of the sulfuric acid contained is preferably 150 g / L to 300 g / L. The temperature of the electrolytic solution is preferably 10 ° C. or higher and 30 ° C. or lower.

As for the magnitude of the applied voltage, it is desirable that the higher the voltage is, the easier it is to improve the current density. Although the lower limit is not particularly limited, the theoretical lower limit is the voltage at which an anodic oxide film can be formed on the surface by the redox reaction.

In the second step, the film formation state can be calculated accurately based on the integrated value of the current value obtained by measuring and integrating the value of the current flowing between the anode and the cathode in the first half. In the prior art, it was usual to perform anodizing with a constant current density, so the processing time is proportional to the amount of current flowing, and the anodizing film is formed by measuring the processing time. It was possible to calculate the speed.

(1-2. Action effect)
Since it has the above-mentioned configuration, the method for manufacturing an aluminum component of the present embodiment can limit the voltage to 18 V or less even if the current applied to the rough material fluctuates due to factors such as the condition of the electrolytic solution, and the cell. Since the size can be kept within an appropriate range (40 nm or less), the formation of cracks can be suppressed. Then, by increasing the current value with the upper limit of the power supply limited, it became possible to increase the formation rate of the anodic oxide film. That is, it has become possible to form an anodic oxide film in which the formation of cracks can be suppressed at a high speed.

(2. Second embodiment: Aluminum component manufacturing apparatus)
(2-1. Configuration)
The aluminum component manufacturing apparatus of the present embodiment is an apparatus capable of suitably carrying out the above-mentioned aluminum component manufacturing method. As shown in FIG. 1, the aluminum component manufacturing apparatus of the present embodiment includes a dipping tank 10, a power supply device 20, a control device 30, a temperature control means 40, an anode wiring 21, a cathode wiring 22, and a cathode 25 and 26. ..

The immersion tank 10 is a member that holds the electrolytic solution E, and the rough material W to be treated can be immersed therein. Since the electrolytic solution E is as described in the above-mentioned column of the method for manufacturing aluminum parts, further description will be omitted.

The power supply device 20 is a constant voltage power supply. The output voltage is 18 V or less, as described in the above-mentioned column of the method for manufacturing aluminum parts. From the power supply device 20, the anode wiring 21 and the cathode wiring 22 are connected. A rough material W is connected to the anode wiring 21. Cathodes 25 and 26 are connected to the cathode wiring 22. The cathodes 25 and 26 and the crude material W are fixed to a jig (not shown) so as to be disposed in the electrolytic solution E with a gap.

The control device 30 includes a power supply device control unit 30a for controlling the power supply device 20 and a temperature control means control unit 30b for controlling the temperature control means 40. A control line 31 is connected to the power supply control unit 30a. A control line 32 is connected to the temperature control means control unit 30b.

The power supply control unit 30a has a current integrating unit 30a1 and a control unit 30a2, integrates the current value output by the current integrating unit 30a1 over time, and the control unit 30a2 of the anodized film generated based on the integrated value. The thickness is calculated and control is performed to stop the output of the voltage from the power supply device 20 when the target thickness is reached.

The temperature control means control unit 30b controls the temperature control means 40 so that the temperature of the electrolytic solution E becomes a target value based on the temperature of the electrolytic solution E measured by the temperature control means 40. The target value of the temperature of the electrolytic solution E is as described in the above-mentioned method for manufacturing aluminum parts.

The temperature controlling means 40 is arranged so as to be immersed in the electrolytic solution E, and measures the temperatures of the stirring means (not shown) for stirring the electrolytic solution, the heater (not shown) for heating the electrolytic solution E, and the electrolytic solution E. It has a thermometer (not shown).

Although FIG. 1 describes an embodiment in which there is only one crude material W, it is also possible to adopt an embodiment in which a plurality of crude materials W are processed at the same time. In that case, it is necessary to prepare a plurality of sets of the power supply device 20, the power supply device control unit 30a, the cathodes 25 and 26, the anode wiring 21, and the cathode wiring 22 according to the number of rough materials W. The immersion tank 10, the electrolytic solution E, the temperature control means 40, and the temperature control means control unit 30b can be prepared as a set of a plurality of crude materials W in a number smaller than the number of the plurality of crude materials W.

(2-2. Action effect)
Since it has the above-mentioned configuration, the aluminum component manufacturing apparatus of the present embodiment can be limited to 18 V or less even if the voltage applied to the crude material fluctuates due to factors such as the condition of the electrolytic solution, and thus the cell size. Can be contained in an appropriate range (40 nm or less), so that the formation of cracks can be suppressed. Then, by increasing the current value with the upper limit of the power supply limited, it became possible to increase the formation rate of the anodic oxide film. That is, it has become possible to form an anodic oxide film in which the formation of cracks can be suppressed at a high speed.

The manufacturing method and manufacturing apparatus for aluminum parts of the present invention will be described in detail based on the following examples.

(Test 1)
The relationship between the cell size of the anodic oxide film and the applied voltage was evaluated. The applied voltages were 18V (Test Example 1-1), 20V (Test Example 1-2), and 22V (Test Example 1-3). The peak values of the current densities flowing through each were 1 A / dm 2 in Test Example 1-1, 5 A / dm ² in Test Example ^{1-2, and 7.5 A / dm 2 in} Test Example 1-3. Therefore, in order to keep the thickness of the anodic oxide film formed constant, the treatment time was 900 seconds for Test Example 1-1, 180 seconds for Test Example 1-2, and 120 seconds for Test Example 1-3. The obtained crude material on which the anodic oxide film was formed was treated at 165 ° C. for 1 hour. Then, the state in the cross section in the direction orthogonal to the direction in which the anodic oxide film was formed was observed with a metallurgical microscope and SEM, and the presence or absence of cracks in the anodic oxide film and the cell size were measured.

As a result, only Test Example 1-1 did not generate a crack. The cell size was 40 nm for Test Example 1-1, 50 nm for Test Example 1-2, and 55 nm for Test Example 1-3. Therefore, it was found that the occurrence of cracks can be suppressed by setting the applied voltage to 18 V or less. It was found that the cracks could be suppressed because the cell size could be reduced to 40 nm or less. Furthermore, it was confirmed that an anodic oxide film was formed and cracks did not occur even when the applied voltage was 13 V.

(Test 2)
Regarding the presence or absence of cracks and changes in cell size when the current value (peak value) is changed under the conditions of Test Example 1 (applied voltage is 18 V) in which cracks did not occur under the conditions of Test 1. Study was carried out. The values of the applied current are shown in Table 1. The value of the current was controlled by adjusting the concentration of sulfuric acid contained in the temperature of the electrolytic solution as shown in Table 1. The crude material on which the anodic oxide film was formed was evaluated in the same manner as in Test 1. Furthermore, the appearance was observed to confirm the presence or absence of film burning. The results are shown in Table 1.

As is clear from Table 1, no film burning or cracking occurs when the current density is in the range of 0.98 A / dm ² (Test Example 2-1) to 7.19 A / dm ² (Test Example 2-5). Do you get it. In this case, when the sulfuric acid concentration of the electrolytic solution is 200 g / L, the current density increases as the temperature rises in the range of 10 ° C. (Test Example 2-1) to 30 ° C. (Test Example 2-5). It was clarified that the anodic oxide film formed in this range did not burn or crack. The cell size was also 40 nm, and the cell size did not change even if the current density changed.

It was found that when the sulfuric acid concentration of the electrolytic solution was 300 g / L, the anodic oxide film formed at the electrolytic solution temperature of 15 ° C. (Test Example 2-6) did not cause film burning or cracking. The cell size was also 40 nm, and the cell size did not change even if the current density changed. Film burning and crack formation were observed at electrolyte temperatures of 20 ° C (Test Example 2-7) and 25 ° C (Test Example 2-8). In this case, the current density is 11.4 A / dm ² at an electrolytic solution temperature of 20 ° C. and 68.6 A / dm ² at 25 ° C., and the current density becomes too high due to the high electrolytic solution temperature, resulting in a large Joule heat. It was speculated that the cause was the occurrence of.

It was found that the sulfuric acid concentration of the electrolytic solution was preferably 200 g / L because the variation in the film thickness of the formed anodic oxide film was smaller than that of 300 g / L.

(Test 3)
FIG. 2 shows the change with time of the current value when the applied voltage is fixed at 18V. As is clear from FIG. 2, the current value changes with time, but it was confirmed that there is almost a correlation between the integrated value of the current and the thickness of the generated anodic oxide film (see FIG. 3). Therefore, it was confirmed that the thickness of the anodic oxide film can be measured by calculating the integrated value of the current density.

10 ... Immersion tank 20 ... Power supply device 21 ... Anode wiring 22 ... Cathode wiring 25, 26 ... Cathode 30 ... Control device 30a ... Power supply device control unit 30b ... Temperature control means control unit 40 ... Temperature control means W ... Rough material (processed) subject)

Claims (2)

A crude material made of aluminum or an aluminum alloy and to be treated is used as an anode, and is brought into contact with an electrolytic solution having a sulfuric acid concentration of 150 g / L to 300 g / L together with a cathode.
A current is passed between the anode and the cathode under constant voltage conditions where the current density is 0.8 A / dm ² to 7.5 A / dm ² and the applied voltage is 13 V or more and 18 V or less (excluding 15 V or less) . , Produces an anodic oxide film with a cell size of 40 nm or less,
By calculating the integrated value of the current flowing between the anode and the cathode and ending the process when the formed thickness of the anodic oxide film calculated based on the calculated integrated value reaches a predetermined value. Generates the anodic oxide film of a predetermined thickness and
A method for manufacturing an aluminum part in which cracks do not occur when heat-treated at 165 ° C. for 1 hour. When the sulfuric acid concentration is 150 g / L to 300 g / L, the temperature of the electrolytic solution is 10 ° C. or higher and 30 so that the current density is 0.8 A / dm ² to 7.5 A / dm ² . The method for manufacturing an aluminum component according to claim 1, wherein the value is constant within the range of ° C. or lower.

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