JP3482298B2 - Masking method in vacuum arc descaling method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a surface of a member, and more particularly, to a method for partially removing dirt or an oxide film on a metal surface by a DC arc discharge in a vacuum. The present invention relates to a masking method in a vacuum arc descaling method for removing a gas. 2. Description of the Related Art As a method for cleaning the surface of a metal member, as disclosed in Japanese Patent Application Laid-Open No. 5-86451, a processing member is placed in a vacuum container, and the processing member is used as a cathode and the vacuum container is used. A method has been devised in which a DC arc is generated between a cathode and an anode using an electrode separately provided therein as an anode to remove oxides and impurities on the member surface. [0003] This method is called vacuum arc descaling, in which arc discharge is usually performed in an atmosphere of 10 ⁴ Pa to 1 Pa. It is called vacuum arc descaling, but it is not a technology in a strict sense of vacuum,
This is a scale removal technology using an arc created in a reduced-pressure atmosphere. An arc formed in a reduced-pressure atmosphere is referred to as a vacuum arc according to the practice of the present invention. The term “descaling” here includes removal of scale, removal of thin oxide film, or removal of other surface contamination. Since the surface is roughened by vacuum arc descaling, it may be used as a method for roughening the surface. In the present invention, the surface cleaning and the surface roughening treatment using the vacuum arc are collectively referred to as vacuum arc descaling. In vacuum arc descaling, a member to be treated for scale removal is connected to the negative polarity of a power source, acts as a cathode, and generates an arc between the anode and a separately installed anode. The oxide film on the cathode surface is removed by the action of the arc cathode spot formed on the surface of the object to be treated as the cathode. Some members dislike such a surface change, and it is necessary to mask portions where they do not want to be changed to protect them from the cathode spot. Conventionally, for such masking, a glass fiber tape is stuck or a plate made of Teflon (registered trademark) material, glass, or heat-resistant ceramic is used in close contact with the member surface. [0005] When the conventional masking method is adopted, the following problems occur. That is, since the energy density of the arc cathode spot is very high, when the cathode spot approaches the edge of the masking material, the masking material melts, thermally decomposes, or evaporates. As a result, the surface of the descaling processing member is soiled, or the masking effect is lost. For example, as shown in FIG.
Between the member 2 to be subjected to the vacuum arc descaling process and the anode electrode 3 installed in the
Consider a case in which a vacuum arc is formed and a part of the member surface is descaled. In order to mask a part of the surface of the member 2, a part of the surface of the member 2 is covered with a masking material 5 made of a refractory ceramic such as alumina, and when the vacuum arc treatment is performed, the masking material on the surface of the member 2 is covered. The oxide film in the unexposed area is removed by the action of the arc cathode spot, and the surface covered with the masking material is protected from the arc cathode spot. However, in this case, the surface of the member near the end of the masking material indicated by 6 is different from the other parts in the function of the arc cathode spot, and the cathode spot is often concentrated.
For this reason, the vicinity of the masking boundary becomes a defective portion where the surface roughness is conspicuous. As described above, the use of the vacuum arc for the purpose of cleaning the surface may instead cause surface contamination and defects. The present invention is a method for solving such a problem of the conventional masking method, and an object of the present invention is to enable partial descaling without causing a descaling defect at a masking boundary. . [0008] The present invention provides a masking method for protecting a member surface from a vacuum arc cathode spot.
Vacuum arc descaling, characterized in that a material electrically insulated from the material to be scaled is used as a masking material, and the masking material is descaled with the end of the masking material separated from the surface of the material by 0.3 to 2 mm. It is a masking method in the method. The method of the present invention will be described with reference to FIG. When a vacuum arc is formed by a DC power supply 4 between a member 2 to be subjected to a vacuum arc descaling process installed in a vacuum chamber 1 and an anode electrode 3 and descaling is performed, descaling is performed as necessary. Mask the parts that you do not want to process. The present invention relates to this masking technique. Conventionally, the masking material has been applied by directly attaching or directly placing the masking material on the surface of the member to be descaled. It has been found that the placement eliminates defects such as surface roughening and local excessive melting in the masking boundary region, which have conventionally occurred. The distance between the masking material 5 and the surface of the descaling member is desirably 0.3 mm or more and 2 mm or less. If it is smaller than 0.3 mm, the effect of preventing surface roughness is weak, and if it is larger than 2 mm, the arc cathode spot enters between the masking material and the descaling member, and the masking effect cannot be sufficiently exhibited. Separating the masking material from the descaling member does not necessarily mean that the entire masking material is completely lifted from the surface of the descaling member. What is necessary is that it does not contact the surface of the scaling member. As shown in FIG. 1, when the depression is formed and the end of the masking material is not brought into contact with the descaling member, it is desirable that the depth of the depression is at least twice the interval of the gap. Needless to say, the masking material and the descaling member must be electrically insulated. By providing a gap between the masking material and the surface of the descaling member, the degree of freedom in selecting the material of the masking material is increased. That is, since the arc cathode spot does not come into direct contact with the masking material, the heat load of the masking material is reduced, and strict heat resistance is not required. Melting point 1000 ° C in addition to various ceramics and glass
The following metals and synthetic resins such as bakelite can also be used. When a conductive material such as a metal is used as the masking material, an insulating tape or an insulating plate 7 is interposed between the masking material 5 and the descaling member 2 to ensure electrical insulation. EXAMPLE A descaling process using a vacuum arc was performed on the surface of a stainless steel SUS430 steel plate. This stainless steel sheet is heat-treated in advance and has a thickness of about 1μ on the surface.
m oxide film is formed. Part of the surface was masked with an alumina plate to perform partial descaling. As shown in FIG. 2, the method of placing the alumina masking plate is as follows, according to the conventional method, when the alumina plate is directly placed on the surface of the stainless steel material, and as shown in FIG.
A gap was created between the surface and the alumina plate, and two methods, that is, vacuum arc descaling, were performed, and the descaling surface properties of both were compared. In the latter method according to the present invention, the gap between the alumina plate and the stainless steel plate was 0.5 mm. In each case, the arc current was 200 A,
Descaling was performed at a degree of vacuum of 0.1 Torr. Visual observation after vacuum arc descaling shows that, according to the conventional method, when the alumina plate was directly placed, the surface of the stainless steel near the end of the alumina plate was excessively melted and solidified. Spots were scattered. When the surface roughness of such a masking boundary was measured by a stylus type surface roughness meter, the maximum surface roughness was 90 μm in the region near the masking boundary according to the conventional method. On the other hand, in the vicinity of the masking boundary according to the method of the present invention, the maximum roughness is 20 μm.
m, which was not much different from the maximum surface roughness of 18 μm in the central area of the descaling remote from the masking boundary, and no defect was found in the boundary region. As described above, according to the present invention,
In the vacuum arc descaling process, masking can be performed without generating a surface defect near the masking boundary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the principle of the masking method of the present invention in vacuum arc descaling. FIG. 2 is a principle diagram of a conventional masking method in vacuum arc descaling. [Description of Signs] 1 Vacuum chamber 2 Descaling member (cathode) 3 Electrode (anode) 4 DC arc power supply 5 Masking member 6 Defect generating part 7 Insulating material

Claims (1)

(57) [Claim 1] In a masking method for locally protecting a surface of a member to be descaled in a vacuum arc descaling method, a material electrically insulated from the member to be descaled is treated. A masking method in a vacuum arc descaling method, wherein descaling is performed by using a masking material such that an end portion of the masking material is separated from a surface of a member to be processed by 0.3 to 2 mm.