JPH08269799A - Surface treatment of aluminum material and surface treatment device therefor - Google Patents

Abstract

PURPOSE: To form hard oxidized protective films having good surface roughness at the time of subjecting a work made of aluminum to an anodic oxidation treatment. CONSTITUTION: A three-phase AC power source 1 is converted to a DC power source by current rectification and thereafter, this DC power source is smoothed and is supplied to the work 4. Then, the stable DC power source free from distortion is supplied to the work 4 and, therefore, the current densities in the respective parts of the work 4 are uniformized. The oxygen generation rates in the respective parts of the work 4 are consequently uniformized and eventually, the surface roughness of the hard oxidized protective films is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method and a surface treatment apparatus for forming a protective film on the surface of an aluminum material.

[0002]

2. Description of the Related Art An example of a protective film formed on the surface of an aluminum material is a hard oxide protective film (Al2O3). This hard oxidation protection film is obtained by generating oxygen on the surface of the aluminum material immersed in the electrolytic solution, and this treatment method is called anodization treatment.

Conventionally, when anodizing an aluminum material in a sulfuric acid aqueous solution, a three-phase 200V AC power source is converted to a DC power source by using a thyristor-controlled rectifier circuit, and this DC power source is supplied to the aluminum material. are doing. In this case, the conduction angle of the rectifier circuit is adjusted according to the size (resistance value) of the aluminum material to maintain the current flowing between the anode (aluminum material) and the cathode at a predetermined value. Therefore, depending on the size of the aluminum material, the treatment may be performed in a state where the rated capacity of the rectifier circuit is less than the rated capacity.

FIGS. 4A and 4B show voltage waveforms output from the rectifier circuit. FIG. 4A shows a voltage waveform when the rectifier circuit has a rated capacity, and FIG. 4B shows a voltage waveform below the rated capacity. The voltage waveform when the voltage is applied is shown. As shown in the figure, a voltage waveform with a relatively small amount of fluctuation is obtained at the rated capacity, and when the voltage is below the rated capacity, the fluctuation of the voltage waveform becomes large. Note that (a ′) of FIG. 4 is a current waveform with respect to the voltage waveform of (a), and (b ′) is a current waveform with respect to the voltage waveform of (b).

[0005]

However, since the above-mentioned conventional device has a structure in which the DC power source converted by the rectifier circuit is directly applied to the aluminum material, as shown in FIG. When it was below the range, the voltage fluctuation was large and the fluctuation of the current flowing in the sulfuric acid aqueous solution was also large.

Since aluminum materials generally contain impurities, there is some variation in the conductivity of each part. Therefore, when the fluctuation of the current flowing through the sulfuric acid aqueous solution becomes large,
Large variations occur in the current density in each part of the aluminum material. Then, the oxygen generation rate in each part of the aluminum material varies, and the surface roughness of the hard oxidation protection film deteriorates. Therefore, Ni or the like is added to the sulfuric acid aqueous solution to facilitate the flow of current, or the hard oxidation protection film is formed. Extra work is required to improve the surface roughness by cutting.

The present invention has been made in view of the above circumstances, and an object thereof is to form a hard oxide protective film having a good surface roughness without extra work such as adding Ni and cutting an oxide film. An object of the present invention is to provide a surface treatment method and surface treatment apparatus for an aluminum material that can be used.

[0008]

A method for surface treatment of an aluminum material according to claim 1, wherein a protective film is formed on the surface of the aluminum material, wherein a hard oxide protective film is formed on the surface of the aluminum material. It is characterized in that it comprises an anodizing process, and this anodizing process is performed based on smoothing a DC power source obtained by rectifying a multi-phase AC power source and supplying it to the aluminum material. The surface treatment method for an aluminum material according to a second aspect is characterized by including a soft protective film forming step of forming a soft protective film made of a fluororesin on the surface of the hard oxidation protective film.

According to a third aspect of the present invention, there is provided a surface treatment apparatus for an aluminum material, which is for forming a protective film on the surface of the aluminum material, and is provided with an anodizing section for forming a hard oxidation protective film on the surface of the aluminum material. The anodizing unit has rectifying means for rectifying the multi-phase AC power source and converting it to a DC power source, and smoothing means for smoothing the DC power source converted by the rectifying means and supplying the smoothed aluminum material. There is a feature in that.

[0010]

According to the means described in claims 1 and 3, the multi-phase AC power supply is rectified and converted into the DC power supply, and the DC power supply is smoothed and supplied to the aluminum material. Therefore, a stable direct current power without distortion is supplied to the aluminum material,
The current density in each part of the aluminum material is made uniform. Therefore, the oxygen generation rate in each part of the aluminum material is made uniform, and as a result, the surface roughness of the hard oxidation protection film is improved. According to the second aspect of the present invention, the soft protective film made of fluororesin is formed on the surface of the hard oxidation protective film.
Therefore, the wear resistance of the aluminum material is improved and the frictional resistance is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will now be described with reference to FIGS.
It will be described based on. First, in FIG. 1, a rectifier circuit 2 corresponding to a rectifying means is connected to a three-phase 200V AC power source 1 corresponding to a multi-phase AC power source. This rectifier circuit 2
Is a thyristor control system whose conduction angle can be adjusted, and converts the three-phase 200V AC power supply 1 into a DC power supply by three-phase full-wave rectification.

A smoothing circuit 3 corresponding to a smoothing means is connected to the power supply line (+) 2a and the power supply line (-) 2b of the rectifier circuit 2. The smoothing circuit 3 includes a choke coil 3a inserted in a power supply line (+) 2a and a capacitor 3b connected between the power supply line (+) 2a and the power supply line (-) 2b.
And a resistor 3c connected between the power supply line (+) 2a and the power supply line (−) 2b, and smoothes the DC power supply converted by the rectifier circuit 2.

2A and 2B show voltage waveforms output from the smoothing circuit 3, wherein FIG. 2A is a voltage waveform when the rectifying circuit 2 has a rated capacity, and FIG. 2B is a rated capacity. Shows the voltage waveform when it is below. In this case, since the output voltage of the rectifier circuit 2 is smoothed by the smoothing circuit 3, the fluctuation of the DC power source is small both at the rated capacity and when the rated capacity is less than the rated capacity. In addition, (a ') of FIG.
Is a current waveform with respect to the voltage waveform of (a), and (b ') is
It is a current waveform with respect to the voltage waveform of (b).

The power supply line (+) 2a of the rectifying circuit 2 has a structure shown in FIG.
As shown in FIG. 3, the object to be processed 4 made of an aluminum material is connected, and the power source line (−) 2b is connected to the cathode plates 5 and 5 (cathode). The object to be processed 4 is composed of, for example, a fixed scroll or an orbiting scroll of a compressor, and functions as an anode as described later. Further, the sulfuric acid aqueous solution is stored in the electrolytic bath 6,
Is immersed in an aqueous sulfuric acid solution.

Then, a DC power source smoothed by the smoothing circuit 3 is applied between the object to be processed 4 and the cathode plates 5 and 5, and when a current starts to flow in the sulfuric acid aqueous solution, (1 The electrode reaction of the formula) occurs, and electrons are extracted from the water molecules to the object 4 side. 2H2 O → O2 + 4H + + 4e- (to cathode plate 5) (1) As a result, oxygen is generated on the surface of the object 4 to be processed, and the generated oxygen causes porous hard oxidation on the surface of the object 4 to be processed. A protective film (Al2 O3) is formed. The following equation (2) shows the electrode reaction on the surface of the cathode plate 5. 4H + + 4e- (from cathode plate 5) → 2H2 (2)

A current detector 7 is inserted in the power supply line (-) 2b of the rectifier circuit 2. The current detector 7 is composed of a moving coil type ammeter 7a and a shunt 7b, and the moving coil type ammeter 7a displays a current value flowing through the device. Therefore, the rectifier circuit 2 is adjusted according to the size (resistance value) of the workpiece 4 while observing the display of the current detector 7.
Is adjusted to maintain the amount of current flowing between the object to be processed 4 and the cathode plate 5 at a predetermined value. Incidentally, reference numeral 8 indicates an anodizing unit composed of a rectifying circuit 2, a smoothing circuit 3, an electrolytic bath 6 and a current detector 7.

A sealing treatment tank 9 is provided on the side of the electrolytic cell 6. A nickel acetate solution is stored in the sealing treatment tank 9, and the object to be treated 4 for which the formation of the oxide film is completed.
Is washed with water and then immersed in a nickel acetate solution. Then, when the nickel acetate solution is allowed to stand for 1 to 5 minutes while being heated to about 60 to 80 ° C., a hydration reaction occurs (formation of Al2 O3 .H2 O), and the holes of the hard oxidation protection film are partially sealed.

A lubrication treatment tank 10 made of stainless steel is provided on the side of the sealing treatment tank 9. This lubrication tank 10
A lubrication treatment solution in which polytetrafluoroethylene (PTFE) particles are dispersed is stored therein, and the object 4 to be treated after the sealing treatment is washed with water and then immersed in the lubrication treatment solution. . Then, the lubricating treatment solution is added to 30-40
When left for 5 minutes or more while being heated to about ° C, the PTFE particles in the lubricating treatment solution are adsorbed on the surface of the hard oxidation protection film.

After the adsorption of the PTFE particles is completed, the object 4 to be processed is dried to complete the surface treatment of the object 4 to be processed. After that, when the object to be treated 4 slides while coming into contact with the other side, the PTFE particles are deformed, and a thin soft protective film made of a fluororesin is formed on the surface of the hard protective film. Well sealed.

The reason why the hard oxidation protective film is semi-sealed in the above-mentioned sealing treatment step is that the PTFE particles are easily adsorbed to the hard oxidation protective film in the lubrication treatment step. An insulating sheet (not shown) made of vinyl chloride is attached to the inner surface of the lubricating treatment tank 10, and the lubricating treatment tank 10 and the lubricating treatment solution are electrically insulated by the insulating sheet. . Therefore, even if a stray current is applied to the lubrication treatment tank 10 from surrounding equipment, the lubrication treatment solution is prevented from being decomposed.

Above the processing tanks 6, 9 and 10,
A carrier (not shown) movable in the horizontal direction and the vertical direction is provided, and a plurality of hangers (not shown) are suspended on the carrier. Then, the processing object 4 is hung on each hanger, and each processing object 4 is
The carrier is supplied to each of the processing tanks 6, 9 and 10 by moving the carrier in the horizontal direction and the downward direction.

According to the above embodiment, the DC power source converted from the three-phase AC power source 1 is smoothed and supplied to the object to be processed 4. Therefore, even when the rated capacity of the rectifier circuit 2 is reduced, as shown in (b) and (b ') of FIG.
A stable DC power source with little distortion is supplied to the object to be processed 4.

Therefore, the oxygen generation rate in each part of the object to be processed 4 is made uniform, and as a result, the surface roughness of the hard oxidation protective film is improved to the same level as when the processing is performed at the rated capacity. Therefore, adding Ni etc. to the sulfuric acid aqueous solution,
The extra work of cutting the hard oxidation protection film is eliminated. In addition, using AC8C material, the film thickness is 20 μm and the hardness is H
As a result of forming the hard oxidation protection film of V450, the surface roughness of this example was improved to RZ4.2 in comparison with the conventional surface roughness RZ9.5.

Further, since the soft protective film is formed on the surface of the hard oxidation protective film by performing the soft protective film forming step including the sealing treatment step and the lubricating treatment step, the object to be treated 4
Wear resistance is improved and frictional resistance is reduced. Therefore, it is advantageous to apply the surface treatment of this embodiment to a sliding component such as a scroll in terms of improving the initial sliding characteristics and shortening the familiar time.

By the way, since the anodic oxidation treatment is carried out at a relatively low voltage below the rated capacity, the fluctuation of the rectified output becomes large, and the surface roughness of the hard oxidation protection film tends to deteriorate. Therefore, it is generally believed that the hard oxidation protection film has a poor surface roughness, and it has rarely been applied to parts that require high sliding characteristics. For this reason, in the past, the fact is that the requirement for high sliding characteristics has been met by surface measures such as adding Ni to the electrolytic solution and cutting the hard oxidation protection film.

In the present embodiment, attention is paid to the fact that when the fluctuation of the power source becomes large, the current density in each part of the object to be processed, that is, the oxygen generation rate varies, and the surface roughness of the hard oxidation protection film deteriorates. It was devised to take fundamental measures against the cause of the deterioration of the degree of deterioration, and it is possible to break the convention that the hard oxide protective film has poor surface roughness.

Although the smoothing circuit 3 is composed of the choke coil 3a, the capacitor 3b and the resistor 3c in the first embodiment, the present invention is not limited to this, and the second embodiment of the present invention will be described. As shown in FIG. 3, the smoothing means may be composed of the choke coil 3a. Further, although the thyristor control type rectifier circuit 2 is used in the first and second embodiments, the present invention is not limited to this, and a transistor control type rectifier circuit may be used, for example.

Further, in the above-mentioned first and second embodiments, the sealing treatment step was carried out in order to adsorb the PTFE particles to the article to be treated 4, but the present invention is not limited to this, and the hard oxide protective film is not limited thereto. It may be omitted when a fluorine-based resin that easily bonds to is used. Further, in the above-mentioned first and second embodiments, the scroll is exemplified as the object 4 to be processed, but the present invention is not limited to this, and mechanical parts such as shafts and gears, automobile parts such as cylinders and valves, etc. It may be applied to sliding parts that require high sliding characteristics.

[0029]

As is apparent from the above description, the surface treatment method and the surface treatment apparatus for an aluminum material of the present invention have the following effects. According to the means described in claims 1 and 3, since a stable direct current power source without distortion can be supplied to the aluminum material, the oxygen generation rate in each part of the aluminum material is made uniform, and as a result, the surface roughness of the hard oxide protective film is increased. The degree improves. Therefore, the extra work of adding Ni or the like to the electrolytic solution or cutting the hard oxidation protection film is eliminated. According to the means described in claim 2, since the soft protective film can be formed on the surface of the hard oxidation protective film, the wear resistance of the aluminum material is improved and the frictional resistance is reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of a surface treatment apparatus showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a voltage waveform and a current waveform of a DC power supply.

FIG. 3 is a schematic view of an anodizing unit showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG. 2 showing a conventional example.

[Explanation of symbols]

1 is a three-phase 200V AC power supply (multi-phase AC power supply), 2 is a rectifying circuit (rectifying means), 3 is a smoothing circuit (smoothing means), 3a is a choke coil (smoothing means), and 4 is an object to be processed (aluminum material). , 8 indicates an anodizing portion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C25D 11/04 101 C25D 11/04 101A 11/18 306 11/18 306A

Claims (3)

[Claims] 1. A surface treatment method for forming a protective film on a surface of an aluminum material, comprising: an anodizing treatment step of forming a hard oxidation protective film on the surface of the aluminum material, the anodizing treatment step comprising: A surface treatment method for an aluminum material, which is performed based on smoothing a DC power source obtained by rectifying a phase AC power source and supplying the smoothed DC power to the aluminum material. 2. The surface treatment method according to claim 1, further comprising a soft protective film forming step of forming a soft protective film made of a fluororesin on the surface of the hard oxidation protective film. 3. A surface treatment apparatus for forming a protective film on the surface of an aluminum material, comprising an anodizing section for forming a hard oxidation protective film on the surface of the aluminum material, wherein the anodizing section is An aluminum material having rectifying means for rectifying a phase alternating current power source and converting it into a direct current power source, and smoothing means for smoothing the direct current power source converted by the rectifying means and supplying the smoothed aluminum material to the aluminum material. Surface treatment equipment.