SU1488100A1 - Electron-beam welding apparatus - Google Patents

Abstract

The invention relates to welding and can be used in electron beam welding in mechanical engineering, instrument making and other areas of the national economy. The purpose of the invention is to improve the quality of welding and the electron-optical image of the parts to be welded, as well as to expand the functionality of the electron guns. A final diaphragm is installed on the electron gun body after the deflecting coils, and a focal electrode is located between the anode and the focusing coil, which is connected to a voltage source controlled from the mode unit. A strobe pulse generator connected in series, a synchro generator, an adder, a cumulative unit and an automatic gain controller installed between the video amplifier and amplifier are inserted into the device. The amplifier is multi-channel. The master clock generator is connected to the mode block, line block and frame scan blocks. The adder is connected to the video monitor, the summary unit is connected to the video amplifier, the mode unit is connected to the strobe pulse generator and the vertical scanning unit. The device works in the modes of welding, review, welding and review. Since the secondary electron emission is sensitive to the presence of contaminants on the surface of the object of observation, the image formed in this mode allows us to objectively assess the quality of surface preparation. The image quality generated by the device is not affected by dusting or heating. This makes it possible to estimate with increasing tenfold the processes of flow of the molten metal during the formation of the weld. 3 il.

Description

The invention relates to fusion welding and can be used in electron beam welding (ELS) in mechanical engineering, instrument making and other industries of the national economy.

The purpose of the invention is to improve the quality of welding and the electron-optical image of the parts to be welded.

;

as well as expanding the functionality of electronic guns.

Figure 1 shows a block diagram of a device for electron beam welding; figure 2 - the welding process on the screen of the video monitor in the mode of welding and review} on fig.Z - timing diagram of the device.

 The device is located in the vacuum chamber 1, contains an electron gun 2, for example, a triode type with a cathode 3, a modulator 4, an intermediate HbiM anode 5, a focal electrode 6, an electromagnetic focusing coil 7, deflecting coils 8, a final aperture 9. At the output from the gun 2 is installed in isolation from its body a collector 10 of reflected and secondary electrons 11 formed during the scanning of the electron beam 12 of low intensity when it interacts with the surface of the product 13 installed separately from camera 1. Device The device also contains a unit 14 for operating the modulator 4, a lowercase unit 15 and a frame scanning unit 16, a voltage source 17 for a focal electrode 6 isolated from a gun body 2, a power supply 18 for a focusing coil 7, a multichannel high-frequency amplifier 19 variable input impedances, switches at the inputs, controllable pulses of the mode unit 14, automatic gain control (AGC) 20, additional wideband video amplifier 21, strobe pulse generator 22, which is one generator with a variable duration of a strobe pulse over a wide range, the timing generator 23 sets a single operation of the entire device, ny REDD unit 24 (and p1vertor. transducer), an adder 25 installed in the video signal path, which is a video signal amplifier with an input commutator diode, controls us-1YS of the synchronous generator 23, generating lia the output of the full television signal creating an image of the video monitor screen 26,

The device works. As follows.

When the metal surface is irradiated with a sharply focused beam 12, it is possible to collect information from the topography. the surface of the product 13 due to the processing of signals of secondary or reflected electrons 11 o According to the results of such processing, a video signal is generated that arrives at the monitor screen 26. If the product 13 is isolated from camera 1, then the current absorbed by the electron beam 12 over the product 13

About Q with

five

0

electrons after its enhancement can also be successfully used to obtain an image of the surface of article 13, even in those cases when collector 10 is at a disadvantage due to poor collection geometry. The image in the absorbed electrons has other advantages over the image generated from the signals in the emission mode (secondary or reflected electrons 11). So, when viewing non-planar and developed surfaces, due to the dependence of the electron reflection coefficient and secondary emission on the angle of inclination, it is better to use the mode of absorbed current.

Due to the inversion of contrast, the perception of topography seems to be the opposite of the current to which the observer is used. In order to understand the topography of the surface being examined when operating in the mode of absorbed current, the contrast is often inverted (change from black to white and vice versa) in summary block 24 Such an inverted image reproduces the contrast in the same way as in the emission mode, but is distinguished by the absence of sharp drops in the image contrast. The image view varies slightly when using not only different types of signals, but also their processing methods (contrast reversal, differential amplification, non-linear amplification, signal bias, etc.). The applicability of various signals and their processing methods depends on the nature of the observed object, purity and geometry of its surface.

In the proposed device, image formation according to the processing of several types of signals, which is most effective, is more often used.

The device has the following main modes of operation: welding mode, review mode, welding mode and review mode.

. In the welding mode, the mode unit 14 and the power source 18 of the focusing coil 7 operate in an independent mode. The mode unit 14 is in the welding position, in which the blocking voltage applied to the modulator 4 is adjusted by the operator to set the required voltage for the EBW. welding current and corresponds to the passport data on the gun 2. In this case, the collector 10, the focus electrode 6 and iz-,

dividing 13 are connected by a block 14 of the mode | Ma with the ground to protect the low-current system of the information channel of the image during welding,

In the mode, the review unit 14 modes is switched to the Obzbr position. At the same time, the modulator 4 is overcharged from the mode block 14 and the voltage is higher, which dramatically reduces the maximum possible beam current 12 to 50–70 μA and reduces the beam diameter 12 to thousand millimeters , increasing the resolution of the device. At the same time, the lowercase blocks 15 and the frame sweep 16 feed the sawtooth voltage to the deflection system, which displaces the beam 12 horizontally and vertically, forming a frame on the surface of the product 13 having 625 lines.

In the formation of the frame, the television principle of interlaced scanning is used. The frequency of changing half-frames is 50 Hz. This makes it possible to synchronize the operation of all parts of the device with the help of a clock generator 23. It generates damping and synchronizing pulses and controls the operation of the blocks 15 and frame 16 of the scanning beam 12 synchronously with the operation of the cathode-ray tube of the video monitor 26. The position of the beam 12 at any point in the frame corresponds to the exact same position of the electron beam on the screen of the video monitor 26, which ensures that the orientation of the image is unambiguous. Simultaneously with the formation of the frame, the focal electrode b supplies the potential from the voltage source 17, thereby creating between the focal electrode 6 and the anode 5 on the one hand and between the focal electrode 6 and the building a. 4881006

high quality imaging and highly developed surfaces. As soon as beam 12 is turned on, a signal appears on collector 10, which enters amplifier 19. The signal appears because beam 12 causes electron 11 to be emitted from the irradiated surface of product 13 during scanning. Their number is determined by the surface topology product 13, i.e. the magnitude of this signal and each moment in time is determined by the configuration of the surface in

15 location of the beam 12 when scanning. The implemented and amplified signal goes through the image channel through the AGC block 20, which provides the specified signal level at the output

20 without distorting its form, regardless of its size at the input, is fed to a wide-band, high-frequency, two-stage video amplifier 21. After that, the signal comes to free

25 block 24, where a non-linear signal amplification, i.e. to improve visual perception, the image contrast is reduced, if 30 of the product 13 creates contrast, occupies almost the entire dynamic range, and the parts of interest lie near the black and white levels. Using an inverter block 24. you can change the image from negative to positive and vice versa.

Next, in block 25, the signal is mixed with the synchronizing and damping pulses of the master clock generator 23, forming a television signal at the output of the television signal to a video monitor 26, on the screen of which the operator observes the current generated by the reflected, or secondary electrons

a som of a gun 2 on the other hand two electrons of 45 trones 11 image of the surface of i- / trostatic immersion lenses, with the help of which they fine-tune the focus of the beam 12. As the beam 12 deviates during the scanning process from the gun 2 to the surface product 13 is changed, then to compensate for the change in the diameter of the beam 12 arising from this, it is necessary to automatically change the optical power of the focusing system. This function 55 is performed by the power block 14 and the voltage source 17.

 Depth of focus provided

device large enough for

Section 13. Depending on actual observation conditions, the signal from the current of the transmitted electrons is also used, which alone or together with the emission signal is fed to the inputs of the differential high-frequency amplifier 19 in a ratio determined by their input resistances. Changing these resistances allows you to achieve the maximum ratio of signal to P1um and image clarity. Further signal processing is similar to the emission mode. To increase the signal level of the Plotlotron 11 signal, the image of the surface is

Section 13. Depending on actual observation conditions, the signal from the current of the transmitted electrons is also used, which alone or together with the emission signal is fed to the inputs of the differential high-frequency amplifier 19 in a ratio determined by their input resistances. Changing these resistances allows you to achieve the maximum ratio of signal to P1um and image clarity. Further signal processing is similar to the emission mode. In order to increase the signal level Absorbed Current and its sensitivity to the reflection effect of electrons, mode block 14 can be supplied to item 13 with a positive voltage of 40–40 V. In this voltage, secondary electrons cannot leave product 13.

In pe) idiMe, the beam axis 12 is exposed to the weld joint using the mechanisms for moving the product 13 or the gun 2 and the electronic gauge on the monitor screen 26. The change in image magnification is usually controlled by changing the frame size, i.e., if the information from the length 1 in the space of the object of observation is displayed along a segment of length L on the screen of the video monitor 26, then a linear increase,

After placing the axis of the beam 12 along the junction, the product 13 is retracted to its original position and turns off all the units of the device except the unit. 14 modes and a power supply source 18 of the focusing coil 7, needed for performing the EBW. In this case, the mode unit 14 is switched to the welding position and it reduces the blocking voltage on the modulator 4 to the value specified in the ELS mode. At the same time, it commutes with the ground the collector 10, the focal electrode 6 and the product 13 to protect the low-current image information channel system for the welding time. After the ELS, the device is again switched to observation mode and inspect the weld.

In the welding and viewing mode, the organization simultaneously welds and forms a qualitative image of the surface of the product 13, using the same beam 12 for both operations, which is full. a part of the time is welding, and the other part of the time its energy parameters are sharply reduced and it scans surfaces. This principle makes it possible to divide beam 12 in time into two beams: a survey and welding, and makes it possible to combine 12 different technological functions in one beam. The ratio between the scanning and welding times is selected depending on the specific features of the welding of this material. The device allows varying welding time over a wide range, for example, by scanning the return path of the beam 12 and vice versa.

Thus, the mode of the review and welding is a combination of the first two modes. Unit 14 mode works in this case in a pulsed mode, providing welding and monitoring almost simultaneously. Transition to such a mode of operation is effected by applying a permission signal to the counter of the strobe-pulse generator 22, which is then started by a quartz sync generator 23 and begins to work from the second half-frame. In the middle of the second half-frame, for example, from 416 to 526 lines, the counter of the generator 22 generates pulses, the duration of which forms its one-shot one over a wide range, determined by the size c j of the action zone of the strobe pulses (Fig. 2). The pulses arrive at block 14 of the mode and it reduces the blocking voltage of the modulator 4 to the value set by the operator for the duration of the pulse. This allows welding in the desired mode. At the same time, for the time of the strobe pulses, the mode unit 14 connects to the ground a collector 10, an item 13, a focal electrode 6 for protecting the layer of the current information channel of the image. At the pulse time, the deflection coils 8 are also grounded by mode unit 14.

The dimensions a and b, limiting the zone of action of the strobe pulses, determining the welding zone, can be adjusted; to go within the broad limits (figure 2) about. The welding time can also be increased by reducing the frame size; on the surface of the product 13. At the same time, an increase in the image object occurs. If beam 12 in the first half frame scans an area (ai 6) occupied by the strobe pulse area in the second half frame, this area is visible on the monitor screen 26 at a frequency of 25 Hz.

Upon termination of the strobe pulses, mode block 14 restores the blocking voltage on the modulator 4. Scanning continues. The processing of information from the collector 10 for imaging is similar to the observation mode;

The timing diagrams (FIG. 3) in relative units proportional to the voltage of the clock signal show a sequence of clock pulses formed by a cascade of the clock signal generator entering the clock generator 23 (a); the initial and final pulses of the pulse counter, which cascades into the unit and ensures the installation of the welding pulse in a pre-programmed location, for example, in the center of the line or in the center of the weld seam (b); the operation of the cascade included in the modulator control unit 14, which supplies the constant component of the blocking voltage, which determines the current of the electron beam gun in the review mode and gives a two-pole pulse signal of the direct damping of the backward motion of the beam and the reverse of the reducing voltage up to the value corresponding to the welding current (B) J operation of the diode-transistor switch control stage included in the

14 modes, which is a pulsed signal amplifier coupled from the unit, carrying out, together with diode-transistor keys, the ground of the input circuit of amplifier 19, product 13, and also switching in accordance with the timing diagram of the focusing elements. the electrode 6 and the deflecting coils 8 through the blocks

15 and 16 sweeps (d) j operation of additional diode-transistor switches in cascades in blocks 15

and 16, triggered from unit 14, which commute the deviation of the coil at the moment of passing the current of the deflecting system through a zero value at the moment of applying the pulsed welding beam along the optical axis of the electron-beam gun. In addition, the vertical axis shows the temporal correspondence of the operation of the described stages, which are controlled by a single synchronous generator 23.

The proposed device makes it possible to significantly reduce the number of equipment operating in the vacuum chamber, since it provides not only welding, but also observation, and with minor modifications, automatic beam guiding along the joint. The developed device for ELS was tested on the ELU-15 welding unit in all welding modes of steels and aluminum alloys of various thicknesses. The optimum viewing angle, without creating additional distortion, and the high image quality allow surface crevices to be detected with a width of less than 0.01 mm. Since the secondary electron emission is sensitive to the presence of contaminants on the surface of the object of observation, the image formed in this mode allows us to objectively assess the quality of surface preparation. The quality of the image generated by the device is not affected by the sweeping and heating. This makes it possible to view with the increase in the ten times the processes of flow of the molten metal during the formation of the weld.

Claims (1)

Invention Formula A device for electron-beam welding containing an electron gun with deflecting coils, a focusing coil, a simulated electron collector connected to an amplifier, a video amplifier, horizontal and vertical scanning units coupled to deflecting coils, a mode unit associated with a gun modulator , an amplifier controlled by a power source of the focusing coil and a horizontal scanning unit, a video monitor, characterized in that, in order to improve the accuracy of the beam installation on the welded joint and to expand it The electron guns have the following possibilities on the body: after the deflecting coils, the gun has a final diaphragm, and between the anode and the focusing coil there is a focusing electrode connected to a voltage source controlled from the mode unit; A block diagram of the device also includes a strobe-pulse generator connected in series, a clock generator, an adder, a composite block and an automatic gain controller installed between the video amplifier and amplifier, the amplifier being multichannel The master clock is connected to the mode unit, horizontal and vertical scanning units, the adder is connected to the video monitor, the master unit is connected to the video amplifier, the mode unit is connected to the strobe pulse generator, the vertical scanning unit, and the welded part is connected to the multichannel amplifier and block mode.