JP3308871B2 - Metal surface local treatment equipment by vacuum arc - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a oxidized film, dirt, and a coating film on a metal surface by causing a direct current arc discharge between an anode and a cathode in a vacuum or for modifying the surface of various metal surfaces. The present invention relates to an apparatus provided for a metal surface treatment by a vacuum arc for performing quality control.

[0002]

2. Description of the Related Art In metal surface treatment using a vacuum arc, an arc discharge is usually performed in an atmosphere of 10 ⁴ Pa to 1 Pa. Although it is called vacuum arc processing, it is not a processing technique in a strict sense of vacuum but a processing technique using an arc created in a reduced-pressure atmosphere. An arc formed in such a reduced-pressure atmosphere is referred to as a vacuum arc in accordance with the practice of the present invention. Vacuum arc is used for surface cleaning such as removal of oxide film (scale and rust) on metal surface, removal of oil and fat adhering to the surface, removal of coating film, and surface treatment such as roughening and heat treatment. ing.

In these metal surface treatments using a vacuum arc, a metal member to be treated is connected to a negative electrode of an arc power supply, and an arc is generated between the metal surface and a separately installed anode. The above-described surface treatment is performed by the action of the arc cathode spot formed on the surface of the processing target serving as the cathode.

In order to perform this kind of vacuum arc treatment, a vacuum vessel is provided for accommodating the entire target member to be treated, and a member to be treated is used as a cathode between an anode and a separately disposed vacuum vessel. In general, a vacuum arc is generated to perform a surface treatment of the member. However, in many cases, even large members do not always require the entire surface treatment.
Even in such a case, a large vacuum vessel is used in which the whole is housed in a large member, and the arc treatment in vacuum is often performed in this vessel. In such a method, there is a problem that a large cost is required for the equipment, or a long time is required to reduce the pressure of a large container, and the operation cost is also large.

In order to solve these problems, the present inventors locally expose only a portion necessary for processing a member to be processed to a vacuum atmosphere, and arc-process only this local surface. (Japanese Patent Application No. 08-058762).

[0006] As is apparent from the use of a vacuum atmosphere as a circuit breaker in a power transmission system, it is difficult to generate an arc in a vacuum. Conventionally, as a method of reliably igniting a vacuum arc, there is a method in which an anode or a pilot anode is instantaneously brought into contact with a metal to be treated and then separated to start an arc, or a high frequency is applied between a pilot electrode and a metal to be treated. A method has been adopted in which a high voltage is applied to generate a spark in a pilot electrode and the arc is used as a starting point of the arc to start the arc.

FIG. 1 shows an example of a high-frequency application arc ignition method in a conventional local vacuum arc processing apparatus. A vacuum container is constituted by the metal material 1 to be treated, the water-cooled body 2 and the detachable hem 8 and the like, and the packing 7 keeps airtightness and maintains a reduced-pressure atmosphere. The vacuum container is connected to a vacuum pump via the exhaust port 3. The cooling water is supplied from the cooling water inlet 5 to the anode electrode 4 and the water-cooled body 2, and is discharged through the cooling water outlet 6. The pilot electrode 9 mounted for arc start is connected to a high frequency high voltage source, and a high frequency high voltage is applied at the time of arc start.
The high frequency high voltage causes a spark between the pilot electrode 9 and the metal member 1 to be processed, and becomes a starting point of arc generation.

However, in this local vacuum arc processing apparatus for locally creating a reduced-pressure atmosphere, the vacuum chamber is small, and there are many restrictions on providing a pilot anode or a mechanism for separating the electrodes after they are brought into contact with each other. In many cases, a method of directly applying a voltage in which a high frequency is superimposed between an anode and a cathode is employed without using a pilot electrode, without sacrificing performance.

[0009]

The local vacuum arc processing apparatus proposed by the present inventors (Japanese Patent Application No. 08-05876).
In No. 2), since the arc is generated in a small vacuum chamber, heat is trapped in the vacuum chamber and heat must be removed, so cooling must be strengthened.
There has been a problem that a large amount of cooling water is required or a complicated cooling structure is required to increase the cooling efficiency.
In addition, parts that are difficult to pack and cool for maintaining airtightness are susceptible to damage due to excessive temperature rise, and there is a problem that the life as a vacuum chamber constituent member is short and the reliability of the apparatus is not high.

Due to these restrictions, long-term continuous processing and frequent repetitive processing cannot be performed, so that the processing must be performed in a short period, interrupted for a long time, cooled sufficiently, and then restarted. No work speed could be increased. It is an object of the present invention to provide an apparatus that reduces heat load, is highly reliable, and improves work efficiency in local vacuum arc processing.

Further, in the local vacuum arc processing, another problem is to develop a reliable and simple ignition technique for the arc. As described above, the structure of the apparatus is complicated if the ignition is to be ensured, and the reliability of the ignition is reduced if the apparatus structure is to be kept simple, which has hindered the reduction of the operation cost. A second object of the present invention is to provide a local vacuum arc processing apparatus that enables reliable and simple ignition.

[0012]

The above object of the present invention can be achieved by an apparatus having the following configuration. That is,
(1) In a metal surface treatment apparatus using a vacuum arc composed of an electrode, a vacuum vessel, an arc power supply capable of superimposing a high-frequency voltage, and an exhaust device, the vacuum vessel incorporates an electrode and is made of an insulating member so as to have close contact with a workpiece. (2) a metal surface local treatment apparatus using a vacuum arc, characterized in that the vacuum vessel has a cup-shaped vacuum vessel having a sealing material at a skirt thereof and an inner wall of the vacuum vessel is surrounded by ceramics.
A vacuum container having a sealing portion according to the processing shape of the member to be processed, and a side in contact with the cup-shaped container is further provided with an auxiliary container having a surface adapted to the cup shape, and the inner surface of the vacuum container is made of ceramics. A device for local metal surface treatment by vacuum arc, which is enclosed and has a gap between the ceramic sushi and the auxiliary container,
(3) A metal surface treatment device using a vacuum arc, wherein the inner surface of the ceramic is covered with a conductive film; and (4) a ceramic extruder for constantly bringing the end surface of the ceramic into contact with the surface of the workpiece. A metal surface local treatment apparatus using a vacuum arc having a mechanism.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has found a method for simultaneously solving the problems of the heat load and the difficulty of ignition, which were the problems of the conventional apparatus, and has realized the apparatus. The operation of the method will be described below. FIG. 2 shows an example of the device configuration. In FIG. 2, in order to emphasize the features of the present invention, details of an arc power supply and a vacuum exhaust device capable of superimposing a high-frequency voltage which is the same as the conventional method are omitted, and only a cup-shaped vacuum vessel portion is illustrated. The vacuum vessel includes the metal material 1 to be treated, the water-cooled body 2 and the detachable skirt 8, and the reduced-pressure atmosphere is held by the packing 7. The vacuum container is connected to a vacuum pump via the exhaust port 3. The cooling water is supplied from the cooling water inlet 5 to the anode electrode 4 and the water-cooled body 2 and discharged through the cooling water outlet 6. The inside of the vacuum vessel wall is surrounded by ceramics 10. The anode 4 is connected to a DC power supply on which a high-frequency high voltage is superimposed at the start. The DC power supply on which the high-frequency high voltage is superimposed is not different from the arc power supply generally used in TIG arc welding and the like. When an arc is generated, the presence of the ceramics 10 not only reduces the heat load of the vacuum vessel, but also ensures the ignition of the arc.

The reason why the ignition is facilitated by the presence of the ceramic wall is considered to be as follows. That is, oxides, coatings and other surface layers existing on the surface of the metal surface during the vacuum arc treatment or the metal itself are decomposed and evaporated by the heat of the arc cathode spot. A part of the decomposed and evaporated surface layer or metal goes to the evacuation device, but a considerable amount adheres to the ceramics 10 in the vacuum chamber. The film formed by adhesion contains metal or carbon and thus exhibits conductivity.

That is, the inner surface of the ceramics 10 is automatically and always coated with the conductive material through the vacuum arc processing operation. When a high-frequency voltage is applied between the anode 4 and the metal material 1 to be processed using a DC power supply provided with a high-frequency high-voltage generator, the high-frequency current flows through the ceramic inner wall as a part of a current circuit. At this time, a high-frequency spark is generated between the metal material 1 to be processed and the end face of the ceramics 10, and this is the starting point of the main arc formation. Therefore, if there is a ceramic whose inner wall is conductive, reliable ignition is possible without the pilot electrode 9 as shown in FIG.

If the ceramic material itself has conductivity, the ceramic itself may serve as a cathode and a stable cathode spot may be formed on the ceramic surface. When a stable arc is formed on the ceramic surface, the ceramic is damaged by thermal shock, so the ceramic material must be electrically insulating. When a thin conductive film is formed on the surface of the insulating material, the electric resistance of the conductive film is high, and a stable cathode spot is not formed on this surface.

Although the heat shielding effect of ceramics is great, the temperature of the ceramics itself increases when the arc current is large, when vacuum arc processing is performed continuously for a long time, or when the processing is performed repeatedly and frequently. Since it is difficult to make the removable hem 8 a cooling mechanism, as the temperature of the ceramic rises, the amount of heat transferred from the ceramics 10 to the hem 8 increases, and the hem and the packing are damaged.
In order to suppress the amount of heat transfer from the ceramics 10 to the skirt 8, the contact between the water-cooled body 2 and the ceramics 10 is made dense to cool the ceramics,
The space as shown in FIG. 3 is formed between the skirt portion 8 and the skirt portion 8 to prevent direct contact, and the invention described in claim 2 is extremely effective.

As described above, the ignition of an arc is facilitated by the presence of the ceramics 10. However, the reason that the ignition of the ceramics is facilitated is not the direct cause of the presence of the ceramics, but the surface of the ceramics. The presence of attached conductive material. Since the adhesion of the conductive substance occurs only when the ceramic is placed in the place of metal surface treatment by a vacuum arc, the first arc ignition when wearing new ceramics that has never been exposed to the atmosphere of metal treatment The problem of no effect remains. In order to ensure reliable arc ignition even at the time of first use, the ceramics used first must be ceramics which has been made conductive on the inner surface by another method.
To do this, cover the ceramic surface with a thin conductive film, or
Alternatively, it may be soiled with a conductive material. Various methods, such as plating, CVD or PVD, thermal spraying, or applying a conductive paint, can be used for covering with a thin conductive film. Further, the surface may be easily stained by rubbing the ceramic with a carbon-based material such as graphite.

Since a high-frequency spark is generated where ceramic having a conductive surface is in contact with the metal surface and becomes the starting point of the main arc, the ceramic must be in contact with the metal surface at the time of ignition. is necessary. If the metal material to be processed is below and there is a vacuum chamber above, the ceramic receives a downward force due to gravity and can always keep in contact with the metal surface, but the positional relationship between the metal material and the vacuum chamber is reversed. In some cases, the metal material to be processed must be processed in a state where the vacuum chamber comes down and the vacuum chamber comes down. There is a gap in the space. If a gap is formed, high-frequency sparks are not generated, and it is difficult to shift to the main arc.

FIG. 4 shows an example of a metal surface treatment apparatus using a vacuum arc, which is provided with a ceramic extruding mechanism for constantly bringing the end face of the ceramic according to claim 4 into contact with the metal surface to be treated. . The ceramic inner cylinder 10 is pushed from behind by a spring 11,
The end face of the ceramic is always kept in contact with the surface of the metal to be treated.

[0021]

【Example】

(Example 1) A hot-rolled steel sheet covered with black scale was used as a treated metal material, and a process of locally removing scale, which is black scale on the surface of the steel material, was performed under various conditions. The vacuum vessel shown in FIG. 3 is basically used, and the apparatus is configured as shown in FIG. 5. In some cases, for comparison, ceramics may be removed, the inner surface treatment state of the ceramics may be changed, or between the skirt and the ceramics. The conditions were changed by providing an air gap in the sample. Reference numeral 12 denotes a vacuum device connected to the evacuation port 3, and reference numeral 13 denotes an arc power supply.

The water-cooled body 2 is made of stainless steel,
Is made of bakelite material. The O-ring used as the sealing material 7 is made of silicone rubber. In this embodiment, a thermocouple is embedded in the skirt portion 8 so that the temperature near the inner surface of the bakelite during vacuum arc processing can be measured. An alumina pipe was used as ceramics. A comparison is also made between the case where the inner surface of the alumina pipe is coated with a conductive film in advance and the case where the alumina pipe is kept clean without any operation. Wire explosion spraying of steel wire is used as a pre-coating method of the conductive film. The difference in the heat insulating effect when a space was provided between the ceramics 9 and the skirt 8 was also examined.
In this case, the distance between the ceramic and the bakelite at the bottom is 1
There is a gap of mm. Table 1 summarizes the implementation conditions and the results under each condition.

In the arc start item, "high-frequency ignition" indicates that the arc has started with a DC power supply on which a high-frequency high voltage is superimposed, and "forced ignition" indicates that the high-frequency application has not been performed. Since the arc could not be started, a thin steel wire was connected between the anode and the metal to be processed in a vacuum, and the arc power supply was activated to melt the steel wire and start the arc. In the section of the method of imparting conductivity,
"Line explosion spraying" means that ceramics with a thin metal conductive film formed on the inner surface of a ceramic pipe by the line explosion spraying method, and "vacuum arc" means
This shows that a ceramic pipe with an evaporant adhered to the inner surface was used by starting the arc by the forced ignition method using clean alumina and performing vacuum arc treatment on the metal surface.

More specifically, the embodiment of the case 3 uses, as a starting ceramic, an alumina pipe obtained from the embodiment of the case 2 and having an inner surface to which an evaporant from the vacuum arc processing adheres. The bakelite temperature in the table is the temperature in the vicinity of the inner surface of the bottom bakelite determined from the thermocouple electromotive force immediately after the vacuum arc treatment was continued for 90 seconds at an arc generating atmosphere pressure of 50 Pa and an arc current of 100 A. . However, only in case 1 arc start 20
Since the measurement temperature exceeded 200 ° C. per second, the arc treatment was stopped at the time point of 20 seconds with fear of damage to the bakelite.

[0025]

[Table 1]

From a temperature comparison between the case 1 not surrounded by the ceramic inner wall and the other cases surrounded by the ceramic inner wall, it was confirmed that the heat shielding effect of the ceramic was extremely large. Furthermore, by providing a gap between the ceramic and the skirt as in the case 5, the effect of reducing the thermal load is greater than when the ceramic stub and the skirt are in close contact as in the case 2, the case 3, or the case 4. It was confirmed that it became. As is clear from the comparison between Case 2 and Case 3, it was confirmed that even if ceramics were present, the ignition of the arc was facilitated by the adhesion of the evaporant during the vacuum arc treatment. When using ceramics for vacuum arc treatment for the first time, it was confirmed from Case 4 or Case 5 that a normal high-frequency arc start was possible by forming a conductive film in advance.

[0027]

The processing apparatus according to the present invention described above simplifies the cooling of the apparatus for performing local cleaning and heat treatment of the metal surface by the vacuum arc, simplifies the start of the arc, and provides a long-term stable operation. Operation is now possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a vacuum chamber of a conventional metal surface local processing apparatus using a vacuum arc.

FIG. 2 is a cross-sectional view showing an example of a vacuum container of the apparatus for locally treating a metal surface by a vacuum arc surrounded by a ceramic inner wall surface of the present invention.

FIG. 3 is a cross-sectional view showing an example of a vacuum vessel of the apparatus for locally treating a metal surface by a vacuum arc according to the present invention, which has a gap between ceramics and a vacuum chamber tail.

FIG. 4 is a cross-sectional view showing an example of a vacuum vessel of the apparatus for locally treating a metal surface by a vacuum arc according to the present invention, which has a ceramic extruding mechanism from the rear.

FIG. 5 is a conceptual diagram of the overall configuration of a processing apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Metal to be processed 2; Vacuum container water cooling body part 3; Vacuum exhaust port 4; Anode 5; Cooling water supply inlet 6; Cooling water discharge outlet 7; Packing 8; Vacuum container hem 9; Pilot electrode 10; Spring 12; vacuum device 13; arc power supply

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C23F 4/00 C23F 4/00 A C23G 5/00 C23G 5/00 (56) References JP-A-4-110084 (JP, A JP-A-57-134559 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 45/06 C23F 4/00 C23G 5/00

Claims (4)

(57) [Claims] In a metal surface treatment apparatus using a vacuum arc, comprising an electrode, a vacuum vessel, an arc power supply capable of superimposing a high-frequency voltage, and an exhaust device, the vacuum vessel incorporates an electrode and is insulated to have adhesion to a member to be processed. A metal surface local treatment apparatus using a vacuum arc, comprising: a cup-shaped vacuum vessel having a sealing material made of a member at a skirt portion; and an inner wall of the vacuum vessel is surrounded by ceramics. 2. A vacuum container having a sealing portion adapted to the processing shape of the member to be processed, and further comprising an auxiliary container having a surface adapted to the cup shape on the side in contact with the cup-shaped container. 2. The apparatus according to claim 1, wherein the inner surface is surrounded by ceramics, and a gap is provided between the ceramic sushi and the auxiliary container. 3. The apparatus according to claim 1, wherein an inner surface of the ceramic is covered with a conductive film. 4. The metal surface local treatment apparatus using a vacuum arc according to claim 1, further comprising a ceramic extruding mechanism for constantly bringing the end face of the ceramic into contact with the surface of the member to be processed.