JPS5991650A - Electron-beam welder - Google Patents

Abstract

PURPOSE:To prevent any defective welding which might be caused due to electric discharge developing within an electron gun by detecting change in the acceleration voltage and change in the current of a beam irradiated on a substance to be worked, and stopping the operation of the electron gun when the acceleration voltage becomes smaller than rated voltage by over 10% or when the beam current becomes larger than rated current by over 10%. CONSTITUTION:A high voltage power source 1, an electron gun 2 and a vacuum tube 18 constitute a high voltage main circuit. Welding of a substance 6 to be worked is performed by accelerating an electron beam 5 by applying high voltage to thermions discharged through heating carried out with a cathodic power source 3 after they are controlled with a bias power source 4. The output of an acceleration-voltage detector 7 is compared with that of a voltage setting device 8 by means of an acceleration-voltage comparing circuit 9, and a multivibrator 10 works when the acceleration voltage becomes smaller than the set point by over 10%. The output of a beam-current detector 11 is compared with that of a current setting device 12 by means of a beam-current comparing device 13, and the circuit 13 delivers output when the beam current becomes larger than the set point by over 10%. The output of the vibrator 10 or the circuit 13 is selected with a selection circuit 14 thereby cutting off the high voltage circuit. By the means mentioned above, any defective welding which might be caused due to electric discharge developing within the electron gun 2 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam processing machine, and more particularly to a beam control device suitable for preventing welding defects caused by discharge generated within an electron gun.

The closest known example of the present invention is Japanese Patent Publication No. 4B-27278. This technology works when a discharge occurs within the electron gun.

The high voltage side circuit current is detected and this value is, for example, 0.6A.
A high-voltage circuit control device is provided that can shut off the electron gun in less than 25 microseconds and turn it on after 35 milliseconds if the current exceeds the current limit.
It was developed for the purpose of protecting equipment due to overload.

However, when carrying out, for example, welding work using an actual electron beam processing machine, the most expensive thing is that it must be possible to perform good welding even if electrical discharge occurs within the electron gun.

As a result of conducting actual welding tests, the following drawbacks were revealed in this technology.

(1) The device's maximum permissible current is, for example, 0.6 A or higher, and the high voltage circuit is turned off and then turned on. Due to micro discharges that occur frequently,
The control device will not operate even if a current of 90.6 A or less flows. Therefore, when a current several times higher than the set current is applied to the workpiece, it is impossible to prevent defects such as undercuts from occurring in the welded portion due to excessive melting.

(2) In an electron beam processing machine with a rated acceleration voltage of 30 KV or more, if the turn-off time is less than 25 microseconds, L- will become a dog and the operational amplifier of the electronic control circuit will be damaged by the surge. (L mainly refers to high-voltage cables and high-voltage transformers) (3) If the interruption elapsed time is 35 milliseconds, for example, welding continuity cannot be maintained in horizontal penetration welding with a thickness of 100 mm, and void defects will occur.

As described above, it is currently impossible to prevent welding defects such as voids occurring in the welded portion due to metal vapor entering the electron gun and generating electric discharge.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to
An object of the present invention is to provide an electron beam processing machine that can obtain good welding results even if electric discharge occurs in an electron gun during electron beam welding.

In order to achieve such an object, the present invention provides an acceleration voltage of a beam irradiated onto a workpiece in a high voltage electric circuit consisting of a high voltage power source of an electron beam processing machine and an electron gun which is a load of the power source. and a change in the beam current, and selects a high-voltage electric circuit when the acceleration voltage decreases by 10% or more from the set value or the beam current increases by 10% or more from the set value based on the detection signal. It is characterized by being equipped with a cut-off and control mechanism and a high-voltage electric circuit that cut off the electron gun at any desired time and stop the operation of the electron gun.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, the electron beam processing machine includes a high voltage power supply 1, an electron gun 2. Vacuum tube 18 constitutes a high voltage main circuit. The electron gun uses thermionic electrons emitted by the cathode heating by the cathode power supply 3 to the bias power supply 4.
A high pressure is applied thereto to accelerate the electron beam 5 and weld the material 6 to be welded. In the steady state, the vacuum tube 18 is in a conductive state and welding proceeds as described above. When abnormal discharge occurs within the electron gun, the output voltage of the accelerating voltage detector 7 and the output voltage of the beam current detector 11 change. Changes in the output voltage of the accelerating voltage detector 7 are compared by a voltage setting device 8 and an accelerating voltage comparison circuit 9, and a DC output signal is output. Is this a multi-vibrator? -10, works. Further, changes in the output voltage of the beam current detector 11 are compared by a voltage setting device 12 and a beam current comparison circuit 13 to output a DC output signal. The multivibrator mentioned above
Either the output signal of 10 or the output signal of the beam current comparison circuit 13 operates the control transistor 15 through the selection circuit 14, and the output of the control grid power supply 16 is applied to the vacuum tube 1B, and this vacuum tube operates the high voltage circuit. can be blocked. Immediately after the cutoff, the output signal of the multi-by-break-10 becomes O, and the vacuum tube 18 becomes conductive again, restarting operation of the electron gun. symbol 1
7 is the screen grid power supply for the vacuum tube.

FIG. 2 shows a more detailed representation of the operation of the circuit described above.

In a steady state, a beam acceleration voltage V is applied to the electron gun, and electron beam welding is performed. However, during welding,
When metal vapor emitted from weld metal enters the electron gun, high pressure (between cathode and anode, or between bias and anode) occurs.
breakdown of the insulation occurs, and a discharge occurs within the electron gun.

Therefore, the accelerating voltage V, decreases and the beam current {circle around (2)} increases. However, the degree of decrease in acceleration voltage and increase in beam current differs depending on the degree of discharge. When a discharge occurs and the beam current reaches Ib (Is=1.11.), that is, when it increases from point 27 to point 28, the control transistor described above is activated. During this time, the beam current is at point 2
8 to point 29, but this time 1o is a negligible time of several microseconds or less. By turning on this control transistor, the plate voltage of the vacuum tube is maintained so that the beam current changes from point 29 to point 30 (zero ampere) in t3 seconds. Accordingly, as the beam current decreases, the acceleration voltage also decreases from point 19 to point 20 to point 21 to point 22 (zero potential). At this point 20, that is, V b (V b
= 0.9 V-) Ic, a DC voltage is output from the above-mentioned accelerating voltage comparison circuit, and the multivibrator is turned on. The output of this multivibrator is 11
It is set to hold for 1 second. At this time, since the beam current is zero, the output of the beam current comparison circuit described above becomes zero after 15 seconds. Therefore, the plate voltage of the vacuum tube is maintained by the output of the multivibrator via the 1 selection circuit. Therefore, after 18 seconds, the output of the multivibrator is turned off, the plate voltage starts to turn off, and after t1 seconds, the plate voltage becomes zero. Along with this, the accelerating voltage of the electron gun passes from point 22 to point 23 and returns to the initially set value (■), and the beam current similarly passes from point 30 to point 31 and returns to the value (■) at point 32. , again continuous electron beam welding is possible.

In addition, if a discharge occurs and the beam current does not change significantly and only the accelerating voltage decreases to Vb (Vb = 0.9v,), the accelerating voltage comparison circuit will detect the DC voltage as described above. output and immediately output to the multivibrator.
turns on and performs the same operation, 1, +11+1. After +14 seconds, the steady state is restored and continuous electron beam welding becomes possible.

Furthermore, in this device, when the accelerating voltage fails to re-ignite, the multivibrator is activated from point 23 to 1. +1
．． After a few seconds, the above operation is performed again, and the acceleration voltage is restored from point 25 to normal at point 26.

The sequence of operations for each element in this case is shown by a chain line.

Furthermore, excessive beam current (≧I
If b) occurs, the above-mentioned operation is performed to restore normality. The most important factors in the operation of each of the above elements are the values of Ib g Vb @ j2 @ j3 and t. These specific setting values and their results are shown below.

T! and t should be set from 500 microseconds to 1 millisecond to protect the device.

This is because the inductance L present in the high voltage circuit causes damage to electronic components, especially the operating amplifier. Experimentally, when the acceleration voltage is 30 KV and the beam current is 100 mA, t! The damage occurred in less than 100 microseconds.

For this reason, it has been found that it is effective to set the time between 500 microseconds and 1 millisecond depending on the beam current used.

(2) is a drop of about 20% in 30 to 50 milliseconds, which poses no problem for welding, so it was set to half that, 10%.

Furthermore, for Ib, 30 to 50 mi, l>, 9 to 20
Since it has been confirmed that an increase of about 10% does not affect welding, it was set at 10%, which is half of that increase.

t is the most important value for maintaining weld continuity, that is, for obtaining a sound weld.

As a result of electron beam welding through a plate thickness of 100 wm at a welding speed of 100 m+/min, 1. +1. Good results were obtained when +1° was less than 1z milliseconds, but beyond this,
Despite rapid recovery, void defects occurred. This situation is shown in Figures 3 and 4.

Figure 3 shows the recovery of the discharge generated in the electron gun described above by butt welding workpieces 33 and 34 with a thickness of 100 mm.
．． +1. +1. This is the result of electron beam welding with the time set to 12 milliseconds or less, and the cross section of the weld is (a) and its A
-A section, that is, a longitudinal section is shown in (b). Weld metal 35 showed good quality with no defects in any cross section. Further, the back bead 36 also shows a uniform and good shape. On the other hand, when the bead is 12 mm or more, as shown in FIG. 4, a recess 38 is formed on the bead surface, a protrusion 39 is formed on the back surface, and a void 37 is formed in a portion.

Furthermore, similar results were obtained for thin plates having a thickness of 9.3 to 30.9 m.

From the above, it is desirable that t3 be 10 milliseconds or less. According to the present invention, it is possible to eliminate welding defects caused by discharge generated within the electron gun in electron beam welding. Furthermore, it is possible to eliminate damage to electronic components of the device due to surges caused by discharge.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the operation of the control device, FIG. Figure 3 (bJ is Figure 3 (aJ
FIG. 4 is a cross-sectional view taken along the line AA of FIG. 1... High voltage power supply, 2... Electron gun, 3... Cathode power supply, 4... Bias power supply, 5... Electron beam, 6...
- Workpiece material, 7... Accelerating voltage detector, 8... Voltage setting device, 9... Accelerating voltage comparison circuit, 10... Multivibrator-111... Beam current detector, 12...
・Voltage setting device. 13... Beam current comparison circuit, 14... Selection circuit,
15... Control transistor, 16... Control grid power supply, 17... Screen grid power supply,
18...Vacuum tube % 19-26...Indicates a point to explain the change situation of the accelerating voltage, 27-32...Indicates a point to explain the change situation of the beam current, 33゜3
4...Workpiece material, 35...Weld metal, 36...Back bead, 37...Void defect, 38...Top bead dent. # is darkness □

Claims (1)

[Claims] 1. In a high-voltage electric circuit consisting of a high-voltage power supply of an electron beam processing machine and an electron gun that is a load of the power supply, changes in the acceleration voltage and beam current of the beam irradiated onto the workpiece are detected. However, only when the acceleration voltage decreases by 10% or more of the rated acceleration voltage or the beam current increases by 10% or more of the rated current according to the detection signal, the high voltage electric circuit is shut off for a selected period of time and the electron gun is turned off. An electron beam processing machine characterized in that a high-voltage electric circuit is equipped with a shutoff and control mechanism for stopping operation. 2. Claim 1, characterized in that the time for stopping the operation of the electron gun is 10 milliseconds or less, and the turn-off and turn-on times are controlled within 500 microseconds to 1 millisecond.
Electron beam processing machine according to paragraph.