JPH06280071A - Method and device for degreasing metallic material to be treated - Google Patents

Abstract

PURPOSE:To precisely degrease the entire metallic material to be treated and to improve the chemical properties of the degreased surface of the material by using this device. CONSTITUTION:A space 2 for placing a material 12 to be treated and an electrode 7 to fill the space 2 with a plasma atmosphere are provided in a vacuum chamber 1. The material 12 coated with grease is placed in the space 2, and the chamber 1 is filled with the plasma atmosphere. The entire material 12 is brought into uniform contact with the plasma atmosphere and degreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for degreasing the surface of a metal product and a degreasing apparatus used therefor.

[0002]

2. Description of the Related Art An object to be processed is kept in a vacuum chamber, while plasma is generated by a plasma generator outside the vacuum chamber, and a plasma gas is introduced from the plasma generator through an introduction pipe into the vacuum chamber, and the plasma gas is discharged. The plasma gas is ejected from the ejection port provided on one side of the vacuum chamber and exhausted from the other side of the vacuum chamber to circulate the plasma gas in the vacuum chamber. The plasma treatment is performed by touching (see, for example, Japanese Patent Laid-Open No. 62-15233). According to such a technique, there is a feature that the surface of the object to be treated can be favorably plasma-treated with the plasma gas.

[0003]

However, in this conventional technique, since the flowing plasma gas is brought into contact with the surface of the object to be processed, the plasma gas flow of the above-mentioned plasma gas flows on various parts of the surface of the object to be processed. There was a problem that unevenness in processing occurred because there were places that were good and places that were not. In addition, since the plasma gas is one generated outside the vacuum chamber and sent through the introduction tube, components such as ultraviolet rays, ionized gas, and electrons are significantly reduced on the way of being sent, and radicals are not generated. It will be gas-based. When the object to be treated is a metal, the surface properties of the object to be treated after the plasma treatment with such a plasma gas will cause variations in degreasing. When the atmosphere in the process is contaminated or the object to be treated that is not sufficiently degreased is used as the contact material, it becomes a contact material having a high contact resistance, and there is a problem that the defective rate as a contact material increases.

The present invention has been made in order to solve the above-mentioned problems (technical problems) of the prior art. The object to be treated can be uniformly degreased and the surface of the degreased object to be treated can be chemically treated. It is an object of the present invention to provide a degreasing method and a degreasing device for a metal workpiece, the properties of which can be improved.

[0005]

In order to achieve the above object, a method of degreasing a metal object to be treated according to the present invention is such that a metal object to which oils and fats are attached is kept in a vacuum chamber, The inside of the vacuum chamber is made into a plasma atmosphere by the electrode for plasma generation provided in the above-mentioned vacuum chamber, and the fats and oils adhering to the above-mentioned to-be-processed object are degreased by the plasma atmosphere. Further, the degreasing device for a metal object to be treated according to the present invention comprises a space for holding a metal object to be treated in which oils and fats are adhered in a vacuum chamber, and an electrode for making the above-mentioned space a plasma atmosphere. The vacuum chamber is provided with gas supply means for supplying a gas for plasma atmosphere into the vacuum chamber.

[0006]

When a metal object to which oils and fats are attached is left in the vacuum chamber and the inside of the vacuum chamber is placed in a plasma atmosphere, the entire object is exposed to the plasma atmosphere. Therefore, the above-mentioned fats and oils are uniformly degreased in the whole object to be treated. In the case of this degreasing, the plasma atmosphere in the vacuum chamber contains all of ultraviolet rays, ionized gas, electrons and radical gases, all of which come into contact with the surface of the object to be degreased.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In the degreasing apparatus A shown in FIG. 1, reference numeral 1 denotes a vacuum chamber, which is made of, for example, stainless steel, and has a port (not shown) provided with a sealable door for loading and unloading objects to be processed. Is provided. The mouth may be for loading and unloading individually, or may be shared. Reference numeral 2 denotes a space for holding the object to be processed in the vacuum chamber. An exhaust port 3 of the vacuum chamber is connected to a vacuum exhaust device 4.
Reference numeral 5 denotes a gas supply means for supplying a gas for plasma atmosphere (referred to as process gas) into the vacuum chamber 1. In the figure, one end is connected to the chamber 1 and the other end is connected to a gas supply source (not shown). The gas supply pipe which carried out is shown.

Next, 7 and 7 are electrodes for plasma generation provided in the vacuum chamber 1, and two sets are used in this example. Reference numerals 8 and 8 denote power supply devices for supplying a current for plasma generation to each electrode 7, and as an example, can supply a high frequency (also called radio wave) current of 13.56 MHz. It may be 27.12 MHz. The output of each power supply device 8 is variable so that the amount of plasma generated by each electrode 7 can be controlled. When it is sufficient to control the amount of plasma generated by both electrodes 7 and 7, only one of them may be variable and the other one may be fixed. Examples of the power supply device 8 include a transformer whose output can be adjusted and a current regulator. Regarding the number of the electrodes 7 and the relationship between the electrodes 7 and the power supply device 8, the number of the electrodes 7 may be 3 or more. In that case, a corresponding number of power supply devices 8 are prepared and each electrode 7 is individually connected, a plurality of electrodes 7 are divided into two or more groups, and the same number of power supply devices 8 as the number of groups are prepared. It is possible to employ a configuration in which a plurality of electrodes 7 are connected to separate power supply devices 8 for each group. Reference numeral 9 is a water-cooled feedthrough for introducing high-frequency current, and 10 is an automatic matching device. Next, reference numeral 11 denotes a means for loading and unloading the object to be processed into and from the existing space, and, for example, a roller conveyor is used. 12 indicates the object to be processed that has been carried into the storage space,
It is a metal object to which oils and fats are attached. The object to be processed is handled while being held by a holding means, for example. The holding means is, for example, a holding container 13 as shown in the case of a small object to be processed, and a jig or a table for supporting it in the case of a large object. In some cases, no holding means is used.

Next, degreasing of the object to be treated by the degreasing device A will be described. The object to be processed 12 is put into the space 2 for storage. The object to be treated 12 is a relay contact made of, for example, a copper alloy. Next, the inside of the vacuum chamber 1 is evacuated (for example, 10 ^-1
To about torr). Next, while continuing the exhaust, a process gas such as nitrogen is fed so that the pressure in the vacuum chamber 1 becomes a pressure suitable for plasma discharge, for example, about 0.05 to 3 mbar. Next, a high frequency current is supplied to the electrode 7 to cause plasma discharge (glow discharge) in the vacuum chamber 1. The output density is, for example, 1 × 10 ^-4 ~
It is 0.1 W / cm ³ . The process gas is turned into plasma (generation of low-pressure plasma or low-temperature plasma) by the discharge, and the inside of the vacuum chamber 1 becomes a plasma atmosphere. The plasma atmosphere degreases and activates the surface of the object to be treated 12. This state corresponds to oils and fats on the surface of the object 12 to which ultraviolet rays, nitrogen ions, nitrogen in a radical state, or electrons generated by the plasma discharge are attached, respectively. Then, the fats and oils are decomposed into water vapor and carbon dioxide, which separate from the surface of the object to be treated 12. In this way, the water vapor and carbon dioxide separated from the object to be processed are exhausted to the outside of the vacuum chamber 1 by the exhaust of the vacuum exhaust device 7. The above plasma discharge is performed for a predetermined time, for example
Degreasing of the object to be treated 12 is completed by continuing for about 10 minutes. After that, the supply of the high-frequency current is stopped to stop the plasma discharge and the vacuum exhaust is stopped, and the inside of the vacuum chamber 1 is restored to the atmospheric pressure by, for example, air, and the object 12 to be processed is carried out.

In the case of the above plasma treatment, since the low temperature plasma is generated by using the above-mentioned high frequency, the uniformity of the plasma atmosphere at each place in the vacuum chamber 1 can be improved. Therefore, the entire object 12 can be degreased uniformly. Further, in this case, a plurality (two in this embodiment) of electrodes 7 are used, and each of them is connected to an individual power supply device 8 to enable control of the plasma generation amount at different places in the chamber 1. Therefore, even if the arrangement condition of the object to be processed in the chamber 1 is uneven, the entire object to be processed can be degreased uniformly.

Object to be degreased as described above
12 is sent to the next process. UV rays, ions,
Since the surface of the object to be processed 12 that has been processed by the plasma atmosphere containing radical nitrogen and electrons has high degreasing completeness, atmospheric pollution in the next step is prevented and the object to be processed is used as a contact material. If so, the defective rate can be reduced.

When the degreasing apparatus A is provided with an individual carry-in port and a carry-out port, it is advisable to carry out the treatment of the object to be treated continuously. That is, the object to be processed 12 that has been processed in the storage space 2
Is carried out from the carry-out port, and at the same time, the next object 12 to be processed is carried into the storage space 2 from the carry-in port and the above-described processing is repeated. By doing so, the degreasing treatment of the object to be treated can be performed very efficiently.

As the above process gas, one suitable for the material of the object to be treated is preferably used, and argon gas may be used in addition to the above exemplified ones. When the material to be processed is a material that is easily oxidized, a gas obtained by mixing, for example, about 30% hydrogen with argon may be used as the process gas.
A reducing gas may be used. With such a gas,
Oxidation of the object to be treated can be prevented, and not only the glitter of the metal can be maintained, but also rust can be removed. If the object to be treated is silver, dry air or the like can be used. Further, when it is desired to quickly remove oils and fats attached to the surface of the object to be treated, an oxidizing gas may be used, and then a reducing gas may be used. Alternatively, a mixed gas of an oxidizing gas and a reducing gas may be used.

Another example of the treatment using the degreasing device A is precision degreasing of other metal products. For example, there is a pre-bonding process for bonding rubber to an engine mount bush made of mild steel. This processing is also carried out in substantially the same manner as in the case of the relay contact. Since the degreasing is complete and the activated metal product is well activated, the adhesion of rubber in the next step is extremely high.

[0015]

As described above, according to the present invention, when degreasing the surface of the object 12 to be treated, it is needless to say that the surface of the object 12 to be treated can be degreased by exposing it to a plasma atmosphere. In the above case, since the inside of the vacuum chamber 1 itself is set to the plasma atmosphere, there is an effect that the entire object 12 to be processed is uniformly in contact with the plasma atmosphere and the entire object 12 to be processed can be uniformly degreased.

Further, in the above case, since the plasma is generated in the vacuum chamber 1 as described above, the plasma atmosphere in the vacuum chamber 1 is of a good quality including any of ultraviolet rays, ionized gas, electron and radical gas. It has the characteristic of being an atmosphere. Therefore, in the vacuum chamber 1, the surface of the object 12 to be processed can be degreased by contacting all of the ultraviolet rays, ionized gas, electrons and radical gas, and the cleanliness of the surface of the processed product. There is an effect that can improve. This means that when the processed product is processed in the next step, contamination of the processing atmosphere is prevented,
Further, when the processed product is used as the contact material, the defective rate can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a degreasing device.

[Explanation of symbols]

 1 vacuum chamber 2 space for storage 7 electrode for plasma generation 12 object to be processed

Claims (4)

[Claims] 1. A metal workpiece to which oils and fats are attached is left in the vacuum chamber, and a plasma atmosphere is created in the vacuum chamber by a plasma generating electrode provided in the vacuum chamber. A method for degreasing a metal object, comprising degreasing oils and fats attached to the object. 2. The plasma atmosphere is a plasma atmosphere of an inert gas, a reducing gas or a mixed gas thereof.
A method for degreasing a metal object to be treated as described. 3. The metal object to be treated according to claim 1, wherein the degree of vacuum of the plasma atmosphere in the vacuum chamber is 0.05 to 3 mbar, and the power density of the plasma is 1 × 10 ^{−4 to} 0.1 W / cm ³ . Degreasing method. 4. A vacuum chamber is provided with a space for holding a metal-made object to which oils and fats are attached and an electrode for creating a plasma atmosphere in the space, and the vacuum chamber is provided with the vacuum. A degreasing device for a metal object to be treated, characterized in that gas supply means for supplying a gas for a plasma atmosphere is additionally provided in the chamber.