JPS6299424A - Method for controlling deflection of electron beam in electron beam melting - Google Patents

Abstract

PURPOSE:To precisely control deflection quantity and direction of an electron beam, by adjusting deflection current conducted to deflection coil by informations of deflected vector quantity and exciting current due to leakage magnetic flux accompanied with setting an electromagnetic stirring apparatus. CONSTITUTION:The electron beam 3a emitted from a filament 8 is irradiated to a molten titanium 6 in a hearth 2 while controlling irradiation direction by X and Y deflection coils 9, 10. In this time, the electromagnetic stirring apparatus 7 is provided to a side wall part 2a of the hearth 2 and exciting current is conducted to an EMS coil 11 of the apparatus 7 to electromagnetically stir the titanium 6. At this time, since leakage magnetic flux (broken line) is caused, a current detector 12 is connected with the coil 11 to detect exciting current and the detected information is inputted to a correcting arithmetic device 13. Hereupon, arithmetic for amending deflected quantity and direction is carried out, the result is reflected to X, Y deflection coil amplifiers 14, 15 as output signal to adjust X, Y deflection currents. In this way, deflection quantity caused by leakage magnetic flux and direction can be amended.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides highly accurate control of the deflection of an electron beam associated with the installation of an electromagnetic stirring device when performing electron beam melting of titanium, tartar, etc., for example. This invention relates to a particularly successful method for controlling the deflection of electron beams.

[Prior Art] With the progress of vacuum technology and improvements in electron beam guns in recent years, electron beam melting (hereinafter sometimes abbreviated as EBM) has been attracting attention.

In the electron beam melting method, an electron beam 3a emitted from an electron beam gun 3 is irradiated onto a material such as titanium 6, which is fed into a hearth 2 through a feeder 1, etc., as shown in FIG. The purpose is to melt the titanium 6, etc. in advance, and then guide it into a water-cooled mold 4, etc., and to manufacture an ingot 5, etc., by irradiating the inside of the mold 4 with an electron beam, if necessary. The irradiation direction of the electron beam 3a is freely adjusted by a deflection coil (not shown) provided in the electron beam gun 3, and the electron beam 3a is deflected two-dimensionally in a horizontal plane, thereby uniformly heating the irradiation surface while scanning it. do. In addition, the above-mentioned hearth 2 in the electron beam melting technology of the above-mentioned titanium 6
This also has the purpose of uniformly dispersing molten titanium (hereinafter referred to as molten titanium to distinguish it from the solid raw material titanium) 6, etc., or removing impurities.

[Problems to be Solved by the Invention] However, since the viscosity of the molten titanium 6 is quite high, the actual situation is that it is not always possible to achieve the above dispersion sufficiently just by irradiating it with an electron beam. There is a drawback that uniform dispersion of the molten titanium 6 and the like and removal of impurities cannot always be achieved satisfactorily. However, if the particles are allowed to remain in the hearth 2 for a long time, the above-mentioned uniformity can be achieved sufficiently, but in this case, the smooth flow of the manufacturing process is hindered.

Therefore, we have repeatedly studied techniques for uniform dispersion, and if we install an electromagnetic stirring device 7 as shown in FIG. I got the idea that I could do it. Therefore, in order to make this method industrially viable, an electromagnetic stirring device 7 was installed in an actual machine and an electron beam melting method was being carried out. They discovered a new problem: the electron beam's orbit is changed by the influence, making electron beam control unstable. This is considered to be because the electron beam 3a was affected by leakage magnetic flux accompanying the installation of the electromagnetic stirring device 7. Originally, EBM is based on precise control of the electron beam, so if the electron beam 3a is affected by the leakage magnetic flux, the EBM
The scale may not be able to perform its original function, or it may irradiate areas where irradiation is prohibited, such as the walls of the hearth.
This also poses a risk of damaging Hearth 2.

The present invention has been made in consideration of these circumstances, and even when an electromagnetic stirring device is used, the electron beam is not affected by the leakage magnetic flux accompanying the installation of the electromagnetic stirring device. The present invention aims to provide a method that can precisely control the amount and direction of deviation (hereinafter also referred to as the amount of deviation vector).

[Means for Solving the Problems] An electron beam deflection control method according to the present invention is a method for melting metal in a predetermined container while deflecting an electron beam by flowing a deflection current through a deflection coil. An electromagnetic stirring device is installed near the molten metal to apply electromagnetic stirring to the molten metal, and the deflection vector amount of the electron beam due to the leakage magnetic flux accompanying the installation of the stirring device and the amount of deflection vector of the electron beam flowing into the above 'rFL magnetic stirring device are calculated. The gist is that the relationship with the excitation current is determined in advance, and the deflection current applied to the deflection coil is adjusted based on information about the excitation current.

[Function] As mentioned above, the present inventors have introduced a means called electromagnetic stirring in order to achieve uniform dispersion and removal of impurities, but it has been found that the electron beam is caused to flow due to leakage magnetic flux caused by the introduction of the electromagnetic stirring device. We discovered a new problem and conducted extensive research to resolve it.

First, the inventors organized the causal relationships regarding the amount of deflection vector, leakage magnetic flux, etc. as shown in (1) and (2) below.

(1) When performing EBM while controlling electron beam irradiation with an electron beam deflection coil, the electron beam is deflected as described above, and the amount of the deflection vector has a certain relationship with the leakage magnetic flux. be.

(2) Since the leakage magnetic flux has a constant relationship with the excitation current flowing through the electromagnetic stirring device, the deviation vector amount has a constant relationship with the excitation current.

Based on the above considerations, the present inventors quantified the relationship between the deflection vector of the electron beam and the excitation current, and reflected the excitation current information on the deflection coil based on the quantified relationship. We have found that it is possible to accurately adjust the deviation vector amount, established a specific means, and completed the present invention.

The present invention will be specifically explained below with reference to Examples.

[Embodiment] FIG. 1 is a circuit explanatory diagram showing an embodiment of the present invention. The electron beam 3a emitted from the filament 8 irradiates the molten titanium (described as already molten titanium) 6 in the hearth 2 while the irradiation direction is controlled by the X deflection coil 9 and the Y deflection coil 10. , Hearth 2
An electromagnetic stirring device 7 is provided on the side wall portion 2a of the molten titanium 6.
Electromagnetic stirring is performed. However, since a leakage magnetic flux (indicated by the broken line in the figure) is generated in the upper part of the hearth 2, the electron beam 3a is deflected outward as shown by the arrow in FIG. becomes inconsistent with the goal.

By the way, as mentioned above, the deflection (1) and the direction are determined by the excitation current. For example, a current detector 12 such as a current transformer (CT) is connected to the EMS coil 11 to detect the excitation current, and The information is manually input to the correction calculator 13, where calculations are performed to correct the above deviation amount and direction, and the results are reflected as output signals to the X and Y deflection coil amplifiers 14 and 15. By adjusting the Y deflection current, it becomes possible to correct the amount and direction of the deviation caused by the leakage magnetic flux.

The computing unit 13 has built-in software based on the relationship (deviation amount and direction vs. excitation current) determined in advance, and when the actual excitation current is input, The deflection amount and direction are detected based on the relationship between direction and excitation current, and this is converted into X and Y deflection coil adjustment information and output.

In the above embodiment, when controlling the deflection of the electron beam 3a, the X and Y polarized and parallel currents were directly adjusted, but as shown in FIG.
It may be configured to give 3 outputs. It goes without saying that the EMS coil 11 of the electromagnetic stirrer 7 may be provided at the bottom of the hearth 2.

[Effects of the Invention] Since the present invention is configured as described above, the following effects are exhibited.

(1) Even when an electromagnetic stirring device is provided, the deflection vector amount of the electron beam can be precisely controlled without being affected by leakage magnetic flux accompanying the installation of the electromagnetic stirring device.

(2) Since the deflection vector (2) of the electron beam can be precisely controlled, electron beam melting can be performed safely and advantageously without the risk of irradiating slopes where electron beam irradiation is prohibited.

[Brief explanation of drawings]

Fig. 1 is an explanatory circuit diagram showing one embodiment of the present invention, Fig. 2 is a schematic diagram for explaining the electron beam melting method, and Fig. 3 shows a state in which an electromagnetic stirring device is provided on the side wall of the hearth. Pattern diagram,
FIG. 4 is an explanatory diagram showing the influence of leakage magnetic flux on an electron beam, and FIG. 5 is an explanatory diagram showing another embodiment of the present invention. 2... Hearth 3... Electron beam gun 3a
...electron beam 7...electromagnetic stirring device 9...
x deflection coil 10...Y deflection coil 11...E
MS coil

Claims (1)

[Claims] In a method of melting metal in a predetermined container while deflecting an electron beam by flowing a deflection current through a deflection coil, an electromagnetic stirring device is provided near the container to apply electromagnetic stirring to the molten metal, and the stirring device is installed. The relationship between the deflection vector amount of the electron beam due to the leakage magnetic flux accompanying the leakage flux and the excitation current flowing through the electromagnetic stirring device is determined in advance, and the deflection current flowing through the deflection coil is adjusted based on information on the excitation current. A method for controlling the deflection of an electron beam in electron beam melting.