JP2008260036A - Surface modification method and apparatus by electron beam irradiation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface modification method and apparatus converting a low pressure ionized gas in a housing into plasma and irradiating a body to be irradiated with an electron beam from a cathode electrode, the method and apparatus being adapted to modify the inside surface of a cavity or a hole in the body to be irradiated by electron beam irradiation. <P>SOLUTION: When the inside surface of the cavity or the hole in the body to be irradiated is slightly angled relative to or parallel with the electron beam irradiation axis, a permanent magnet or an electromagnet is arranged in the cavity so that a magnetic flux goes along a surface to be irradiated, thereby deflecting the electron beam axis, making irradiation on the inside surface possible and materializing the modification thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

This invention irradiates the surface with an electron beam in order to make the surface of various metal parts, molds, tools, electrical connection parts, medical metal parts, metal ornaments, etc. mirror-like, cleaned, amorphized, and corrosion-resistant. Belongs to the technology for surface modification.

The technology of the present invention improves a surface modification device using an electron beam of a material surface modification device by an electron beam, more specifically, a LEHCEB (Low Energy High Current Electron Beam [Non-Patent Document 1]), and expands the application range. Is. As a conventional example, it was developed for smoothing the surface of a high-voltage electrode. An electron beam pulse having a cross-sectional area of 10 cm ² or more, a low energy of 10 to 50 kV, a high current of 10 to 30 kA, and a pulse width of several microseconds is used. The surface is modified by irradiating the metal surface, and the device is characterized as a PFD (plasma filled diode) electron gun because it contains ionized gas plasma and keeps the electron beam cross-section density uniform. There is also. In addition, an annular discharge electrode is used to stabilize plasma-generated glow discharge, and a solenoid that forms a magnetic field in the gun is provided on the outer periphery of the electron gun.

The function of this device is not a high-density electron beam by a conventional vacuum electron gun, but an electron beam dispersed in a wide area with low energy that passes through plasma ionized gas. It is used for surface modification because it has no processing action and gives a uniform action over a wide area. The term “reformation” as used herein refers to removal and purification of foreign substances adhering to the material surface, improvement of surface roughness, flattening of microscopic irregularities to form a mirror surface, amorphization of metal by rapid heating and cooling, and corrosion resistance. Etc.

As described above, this apparatus is a kind of electron gun, but it is not a vacuum chamber, but is filled with a low piezoelectric separation gas of 0.1 Pa or less and is turned into plasma, so it is also called a plasma electron gun. In order to keep this plasma stable, an annular plasma anode called a reflected discharge method is provided, and a solenoid is provided outside to create a magnetic field in the space inside the electron gun to prevent electron beam contraction (pinch). Yes.

In the electron beam emission mechanism of this apparatus, a disk-like metal or graphite cathode having an area of several tens of cm ² is used as the field emission cathode, and the irradiated object becomes the target anode. A high-voltage capacitor discharge of 10 to 40 kV is generated between both electrodes to emit an electron beam pulse of about several μs to 0.1 μs. The plasma generation circuit generates a discharge by charging / discharging the capacitor between the annular anode and the electron gun housing to turn the ionized gas into plasma. The plasma holding time is 100 to several hundreds μs, and the electron beam emission is performed within that time. Another capacitor charge / discharge circuit is provided as a power source for exciting the solenoid for creating a magnetic field in the electron gun before and after the plasma holding time.

The target to be surface-modified is placed on the table as a target, the inside of the electron gun is evacuated, then ionized gas, for example, Ar gas is filled at a low pressure, and the magnetic field formation, plasma formation, and electron beam firing are performed in this order. As a result, the surface of the irradiated object is modified. The number of times of irradiation varies depending on the condition of the irradiated object.

FIG. 7 is an overall configuration diagram of the above-described conventionally known LEHCEB surface reforming apparatus. An electron including a housing 4A, an annular electrode 2A, a cathode 1A, an excitation solenoid 5A, a table 6A, and an electron beam target irradiated body 3A. This is a beam irradiation surface modification device. The irradiated body 3A, the table 6A, and the housing 4A are at the same potential, and the cathode 1A and the annular electrode 2A are insulated and independent. Although not shown, the table 6A is appropriately provided with front and rear, right and left movement mechanisms.
The electron beam is emitted from the cathode end face and travels straight to reach the target 3A, and the electron beam cross-sectional area is substantially equal to the cathode end area.

PROSKUROVSKY, D.I. et al. 3, Use of Low-energy, High-current electron beam of surface treatment of metals, Surface and Coatings Technology 96 (1997), 117-122 G.E.OZUR outside 3, Production and application of low-energy, high-current electron beams; Laser and Paricle Beams (2003), 21, 157-174 Cambridge University Press JP 2006-187799 A Patent application for Japanese Patent Application No. 2006-290970

In the above-described prior art and apparatus, the electron beam travels straight on and collides with the target, so that surface modification is not performed when the irradiated surface is parallel to the electron beam.

  As described above, the electron beam for the modification treatment in this apparatus is obtained by applying a high-voltage pulse to the cathode after previously converting the low piezoelectric gas in the electron gun into plasma and collecting it at the gun center by an external solenoid. generate. The electron beam pulse travels straight from the cathode toward the irradiated object, and the surface is modified by thermal action. However, it is impossible to modify the surface parallel to the flight direction of the electron beam. Moreover, the reforming efficiency is low for the inclined surface having a slight inclination angle.

  Accordingly, the present invention provides a magnet disposed in the cavity to deflect the electron beam axis when the inner surface of the cavity or hole of the irradiated object is parallel to or slightly inclined with respect to the electron beam irradiation flight axis, This is to make it possible to reform the material.

In the present invention, a linear electron beam is made to enter the cavity or hole of the irradiated object, and then the flight direction of the electron beam is deflected by the action of the magnetic field lines of the magnet disposed along the inner surface of the cavity. It enables irradiation to the side. The magnet refers to a permanent magnet or an electromagnet that is magnetized so as to generate a magnetic field line perpendicular to the flight axis of the electron beam pulse.

The present invention utilizes the principle that when a magnetic field line perpendicular to the flight axis of the electron beam emitted from the cathode is applied, the flight axis is deflected according to the Lorentz force. The electron beam emitted from the cathode to the plasma space is prevented from expanding and diffusing by the magnetic lines of force provided by the solenoid for holding the plasma provided outside the electron gun, and becomes almost cylindrical and travels straight into the irradiated body.

At this time, as shown in FIGS. 3 and 4, a permanent magnet is arranged in the irradiated object, and the electron beam irradiation flight is different from the magnetic field lines of the solenoid as shown in FIG. 4 when FIG. 3 is viewed from above. If there exists a deflection magnetic force line 4 crossing the axis, preferably orthogonal, the flight direction of the electron beam can be directed to the inner surface of the irradiated object. 3 and 4 show a case where a permanent magnet is used, and in particular, although not shown in detail, it can be replaced by an electromagnet 2 '.

  3 and 4, 1 is an object to be irradiated, 2 is a permanent magnet, 3 is an electron beam, 3 ′ is a black circle and represents an electron and is flying in the direction of the paper surface. Deflection in the direction under the Lorentz force.

Further, as shown in FIG. 4, in the case of one permanent magnet 2, about half 101 on one side of the irradiated body 1 is irradiated and the surface 102 on the opposite side is not irradiated.

At this time, the magnetic force lines 4 of the permanent magnet 2 should be in a direction along the surface to be reformed in a plane orthogonal to the original electron beam axis 3, so that the cylindrical inner wall is surface-modified over the entire circumference. When it is necessary to irradiate, it is possible to irradiate both sides of the inner surface of the irradiated object 1 by combining a plurality of permanent magnets 201 and 202 as shown in FIG.

Further, depending on the shape and size of the irradiated object 1, means for moving the permanent magnet 2 in the axial direction and the turning direction are provided in order to modify the entire inner surface.
Further, in order to prevent the permanent magnet 2 itself exposed to the electron beam 3 from absorbing the reforming energy, if the permanent magnet 2 is coated with an insulator 16 such as glass or ceramics, the permanent magnet 2 is further improved. Efficient surface modification becomes possible.

FIG. 1 is a sectional view of the principal axis of an embodiment of an apparatus having a basic configuration of the present invention, and FIG. 2 is a sectional view taken along line A-A 'of FIG. The apparatus includes an electron gun unit 20 and a gantry unit 21.

The electron gun 20 is composed of a housing 5 that houses the irradiated object 1 and keeps an ionized gas (Ar) at a low pressure hermetic, a cathode 6 and a plasma generation anode (referred to as an anode) 9. The housing 5 and the irradiated object 1 are electrically grounded, and are insulated from the cathode 6 and the anode 9 by high voltage withstanding insulators 7 and 10. The connectors 8 and 11 are conducting wires connected to an external electric circuit. The electron beam emitting surface of the cathode 6 is made of a bundle-like metal wire (Ti) or graphite having an area of several tens of cm ² , and is opposed to the irradiated object 1 as a target. The anode 9 is an annular electrode, and causes glow discharge between the anode 9 and the housing 5 to turn the ionized gas into plasma.
In addition, the electron gun 20 is provided with a solenoid 12 outside, and a magnetic field is created inside the housing 5 to suppress the expansion and diffusion of the plasma and to irradiate the electron beam.

The irradiated body 1 is fixed on a mounting base 13 by a mounting tool 14, and its upper end is covered with a ceramic insulating mask 15 so that the electron beam efficiently enters the cavity.

The magnet 2 is covered with a ceramic box 16 made of a ceramic box, is attached to a ceramic base 17 made of a ceramic plate, and is arranged to freely move up and down in the cavity. The magnet base 17 is fixed to the moving rod 18. The operation of the magnet 2 is as described with reference to FIGS. 3 and 4 in the above paragraphs [0013] to [0018]. The opening / closing door 19 is a door provided in the housing 5 for sealing the opening 19a, and is opened and closed when the irradiated body 1 is attached / detached and inspected. Although the magnet 2 shows a case where a permanent magnet is used, the magnet 2 can be replaced with an electromagnet 2 'described on the right side. In this case, the excitation method and the coating method are the same as in the case of using a permanent magnet.

The gantry unit 21 includes a base 23 on the upper surface, the electron gun 20 is fixed to the upper surface, and a supply / exhaust device, a power supply device, and other devices (not shown) are accommodated in a space formed by the lower leg 22. . 1 is a device that moves the magnet 2 up and down inside the irradiated body 1, and a moving rod 18 enters the electron gun 20 through an airtight sliding bearing 25. The vertical swing motion is transmitted to the magnet 2.

The vertical swing moving device 24 is a device that drives the moving rod 18, and a shifter m10 in which a disk m8 and a gear m9 are integrated is attached to the operating rod 18, and the shifter yoke m4 of the bracket m3 sandwiches both end surfaces of the disk m8. When the bracket m3 is guided by the guide m2 of the column m1 and moved up and down by the motor m7, the screw m5, and the nut m6, the shifter yoke m4 is connected across the both end surfaces of the disk m8, so that the moving rod 18 moves up and down. Moving. In addition, the motor m11 and the shaft m12 attached to the bracket m3 cause the indexing and turning gear m13 to mesh with the gear m9 to turn the permanent magnet 2 to a required angle regardless of the vertical position. The column m1 is fixed to the lower surface of the base 23.

FIG. 6 is an explanatory diagram of the plasma generation circuit 30 and the electron beam generation circuit 40 of the apparatus of the present invention, and the reference numerals are the same as those in FIG.

The capacitor 31 of the plasma generation circuit 30 is connected to the anode 9 on the positive electrode side via an open / close control element (SCR) 32 and connected to the housing 5 on the negative electrode side to form a plasma generation circuit. The open / close control element (SCR) 32 is turned on by a signal from a control device (not shown) to the control terminal 32a.
In order to charge the capacitor 31, a high-voltage DC power supply 33 and a charging resistor 34 are connected to the capacitor 31 via a switch 35 to form a charging circuit.

The capacitor 41 of the electron beam generating circuit 40 has a negative electrode side connected to the cathode 6, and a positive electrode side connected to the housing 5 (the same potential as the irradiated object 1) via an open / close control element (gas switch) 42. It becomes a beam generation circuit. The opening / closing control element (gas switch) 42 is turned on by a signal from a control device (not shown) of the control terminal 42a. In order to charge the capacitor 41, a high-voltage DC power supply 43 and a charging resistor 44 are connected to the capacitor 41 via a switch 45 to form a charging circuit.

The procedure for using the above-described embodiment apparatus is as follows. After the irradiated object 1 is attached to the mounting base 13 in the housing 5, the magnet 2 is arranged at the irradiation position of the cavity of the irradiated object 1 by the up-and-down turning device 24, and the ionized gas in the electron gun by the atmospheric pressure adjusting device (not shown). Is maintained at a predetermined low pressure. When an electromagnet is used as the magnet 2, excitation means is added, and the excitation timing is synchronized with the external solenoid 12.

Next, the solenoid 12 is actuated to create a magnetic field in the electron gun 20, and then the plasma generation circuit 30 is actuated to turn the low-pressure gas in the electron gun 20 into plasma. A portion to be converted into plasma is a lower portion P from the inside of the ring of the anode 9 in FIG. 6 and reaches the inside of the cavity of the irradiated object 1. When the discharge current of the capacitor 31 reaches a peak and the electron beam generating circuit 40 is activated and the capacitor 41 is discharged, the electron beam 3 is emitted from the cathode 6 toward the object 1 and flies into the cavity 1. To do.

The flight direction of the electron beam is parallel to the cavity side surface, but is deflected by the influence of the magnetic force lines 4 of the magnet 2, and as a result, the inner surface of the cavity is irradiated and surface modification is performed. The above procedure is a single cycle, but the part to be surface-modified is band-shaped, and since it is limited, when the entire part needs to be modified, the arrangement of the magnet 2 is changed and the next cycle is performed. carry out.

In the above description, as is already clear, the magnetic force lines 4 formed by the magnet 2 inserted into the cavity or hole of the irradiated object 1 intersect with the flight axis of the irradiated electron beam 3 and in many cases. , Preferably arranged so as to be orthogonal to the horizontal direction, and further so that the magnetic field lines 4 are formed along the turning direction with respect to the inner surface of the irradiation, for example, as shown in FIG. Is preferable for achieving the purpose.

According to the present invention, when the irradiated object has a cavity or a hole and the inner surface thereof is parallel to the electron beam flight axis or has a slight inclination angle, the magnetic lines generated by the magnet disposed inside the cavity are applied to the electron beam. Acting and deflecting the flight axis towards the cavity inner surface allows surface modification of the inner surface.

It is sectional drawing which cut | disconnected the front view explaining the structure of the whole apparatus of this invention horizontally in the cathode central axis. However, a part of the vertical turning movement means of the gantry is not cut. FIG. 2 is a cross-sectional view of the device taken along line A-A ′ in FIG. 1. FIG. 6 is a partially cutaway explanatory view when a magnet is arranged inside an irradiated body in order to deflect an electron beam. Explanatory drawing of the flight direction deflect | deviating because the magnetic force line of a magnet acts on an electron beam. FIG. 5 is an explanatory diagram of an embodiment in which a plurality of magnets are used as an improvement of FIG. FIG. 3 is an explanatory diagram of an embodiment of a plasma generation circuit and an electron beam emission circuit of the apparatus of the present invention. Explanatory drawing of the apparatus explaining a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, Irradiated body 2, Magnet 3, Electron beam 4, Magnetic field line 5, Housing 6, Cathode electrodes 7, 10, Insulators 8, 11, Connector 9, Anode annular electrode 12, Solenoid 13, Mounting base 14, Fixture 15, 16, ceramic mask 17, magnet base 18, moving rod 19, opening / closing door 19 a, opening 20, electron gun 21, gantry 22, leg 23, base 24, vertical swing moving device 25, hermetic sliding bearing

Claims (7)

In an electron beam irradiation surface modification method in which an electron beam emitted from a cathode is irradiated into a cavity or hole of an object to be irradiated through a low-pressure gas that has been made into plasma and the inner surface is modified,
A surface modification characterized in that a permanent magnet or an electromagnet is inserted in the cavity or hole so as to form a line of magnetic force intersecting the irradiation axis of the irradiation electron beam, and the pulse of the electron beam is emitted. Method.   2. The surface modification according to claim 1, wherein a crossing angle between the irradiation axis of the electron beam and a magnetic force line is substantially a right angle, and the magnetic force line is formed along a horizontal turning direction with respect to the irradiation inner surface. Method.   3. The surface modification method according to claim 1, wherein the irradiation is repeated while rotating the permanent magnet or the electromagnet that outputs the lines of magnetic force around the electron beam irradiation central axis.   The surface modification method according to claim 1, 2, or 3, wherein the irradiation is repeated by moving the permanent magnet or electromagnet that outputs the magnetic lines of force up and down along an axis parallel to the irradiation axis of the electron beam. Voltage application means using an annular anode electrode for converting low-pressure gas into plasma, magnetic field forming excitation means for suppressing expansion and diffusion of plasma-generated low-pressure gas, and means for applying a high-voltage DC voltage between the cathode electrode and the irradiated object In an electron beam irradiation surface modification apparatus having
A magnet base for attaching a permanent magnet or an electromagnet is provided so that magnetic lines of force output from the magnet are along the modified side surface in the cavity or hole of the irradiated object and intersect the irradiation axis of the electron beam. Electron beam irradiation surface modification equipment.   6. The electron according to claim 5, wherein the crossing angle between the irradiation axis of the electron beam and the magnetic force line is a right angle, and the magnet base is configured and held so as to be able to move up and down and turn along an axis parallel to the irradiation axis. Beam irradiation surface modification equipment.   7. The electron beam irradiation surface modification device according to claim 5, wherein the surface of the permanent magnet or electromagnet is coated with ceramics resistant to electron beam irradiation modification.

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