RU2012463C1 - Method and device for electron welding beam focusing adaptive control - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: density of steam stream flowing out of a gas and steam channel is measured. The focusing degree is controlled by changing of steam stream density in points symmetrically disposed in the plane of joining on both sides of the welding bath at a distance L from the beam axis, with L = K*P (mm), where K is a proportionality factor equal to 12, P - source beam emissive power, and at the height equal twice the welded part thickness. The device for electron welding beam focusing adaptive control has steam stream density sensor 2; band-pass filter 7; detector 8; extremator 13, trigger 16; pulse generator 18; control unit 14; focusing lens 21; counter 15; digital-analog converter 19; focusing unit 20; adjustable generator 1; standard frequency generator 6; mixer 5; limiter 9; limit level setting device 10; frequency and phase analyzer 11; switch 12. EFFECT: increased accuracy of beam focusing control. 2 cl, 2 dwg

Description

 The invention relates to welding, namely, to control the parameters of the process of electron beam welding.

 The aim of the present invention is to increase the accuracy of focus control by increasing the reliability of information about the nature of the processes in the gas-vapor channel, the invention further allows to expand the scope by increasing the speed and expanding the range of operating powers of the electron beam, in which adaptive focus control is carried out.

To do this, in the focus control method, information on the beam focusing is obtained when processing radiation from the welding zone, using a steam stream leaving the steam-gas channel, while the steam flow sensor is installed symmetrically on both sides of the weld pool in the joint plane above the surface of the welded part at a height of equal to twice the thickness of the welded part and at a distance L from the axis of the beam L = kP (mm), where k is the proportionality coefficient equal to 12; P is the power of the radiation source, kW; P = U _USH ˙Ilucha, an electrical signal, the frequency and phase of which depends on the density of the vapor stream in at the sensor, and change the focus is controlled to change the density in the vapor stream at the sensor.

 In FIG. 1 shows a functional diagram of a device for adaptive focus control of a welding electron beam; in FIG. 2 is a sketch of the design of the sensor.

 The essence of the proposed method is as follows. When welding during the interaction of the electron beam with the material of the part to be welded, a steam stream flows from the depth of the vapor-gas channel, carrying information about the processes occurring in the depth of the channel. The density of the vapor flow depends on the specific power density of the electron beam, determined by the position of its focal plane relative to the surface of the welded part, i.e., focusing. A change in focusing causes a change in the value of the specific power density, which causes a change in the density of the vapor stream flowing from the depth of the vapor-gas channel. The density of the vapor stream is controlled by a sensor, which is two plates spaced apart in space, between which a vapor stream propagates. The capacity between the plates at a constant distance between them and their area is determined by the parameters of the dielectric located between the plates, i.e., the density of the vapor stream. A change in the flux density causes a change in the capacitance of the sensor, which is a sign of a change in focus.

 A practical implementation of the method is to control the density of the vapor stream exiting from the depth of the penetration channel using a sensor. An electronic circuit generates a voltage whose frequency and phase are proportional to the value of the flux density. A change in the vapor flux density leads to a change in the frequency and phase of the indicated voltage, which is a sign of a focus violation (change).

 The essence of the practical implementation of the proposed device is as follows. The frequency of the output voltage of the tunable generator 1 is determined by the capacitance of the sensor 2, depending on the density of the steam stream 3. Changing the focus of the electron beam 4 causes a change in the frequency of the output voltage of the generator 1, which is fed to the input 5.1 of the mixer 5. The output voltage of the generator 6 of a fixed frequency . The output signal of the mixer 5 after filtering by means of a filter 7 is fed to the input of a synchronous-phase detector 8. The amplitude ripples are eliminated by a parallel amplitude limiter 9, the limiting threshold of which is set by the limiter 10 of the limiting level. The output signal of the mixer 5 after filtering by the filter 7 is analyzed in the frequency and phase analyzer 11 and is fed to the input 12.1 of the switch 12. In the extremator 13, the output signal of the synchronous-phase detector 8 is analyzed to an extremum, and the output signal of the extremator is fed to the second input of the switch 12. Block control 14 generates command signals that set the counter 15 pulses in a state that determines the focus current at the initial moment of the welding process, and trigger 16 - in a state in which the control signal input 16.2 allows the passage through the key 17 pulses from the output of the generator 18 to the counting input 15.1 of the counter 15 pulses. In this case, a digital code is generated at the output of counter 15, which is converted by a digital-to-analog converter 19 into a linearly changing voltage, and after conversion and amplification in the amplifier 20, the focusing current enters the focusing lens 21. The steam flow sensor 2 is mounted symmetrically on both sides of the weld pool 22 in the plane the joint above the surface of the part at a distance L from the axis of the beam L = kP, (mm), where k is the proportionality coefficient equal to 12; P is the power of the radiation source, and at a height equal to twice the thickness of the welded part.

 The practical implementation of the device is to use the steam stream of the weld pool 22, the density of which is monitored by the sensor 2 of the steam stream. The sensor capacity at fixed values of the distance between the plates and their area is determined by the value of the dielectric constant of the substance, which fills the space between the plates. The value of this capacitance at fixed values of other parameters of the frequency-setting circuits of the generator 1 determines the value of the frequency generated by it. The inputs 5.1 and 5.2 of mixer 5 receive signals from the outputs of generator 1 and generator 6. The use of generator 6 with a fixed generation frequency allows you to transfer the spectrum of the information signal to the frequency region where interference is practically absent, significantly increase the temporal stability of the average frequency of the information signal, and optimize geometric parameters of the sensor 2. The filter 7 performs additional frequency filtering of the information signal, and its amplitude fluctuations are eliminated by the limiter 9, by The restriction horn of which is set using the device 10. It should be noted that the device 10, in order to ensure automatic selection of the threshold value, can include a circuit for automatic analysis of the magnitude and sign of the amplitude fluctuations of the signal and a circuit for automatically setting the threshold value. The synchronous-phase detector 8 converts the change in the frequency of the information signal into a voltage change corresponding in magnitude and sign. The conversion is carried out taking into account the frequency and phase of the information signal, which further increases the noise immunity of the signal isolation (information) path. The output of the phase-synchronous detector 8 is connected to the input of the extremator 13, which analyzes (controls) the magnitude and rate of change of the signal amplitude from the output of the synchronous-phase detector 8. When the signal amplitude reaches its maximum value (the rate of change of amplitude is zero) the output of the extremator 13, a control signal is generated, which is fed to the switch 12. The mode of determining the maximum amplitude of the information signal is used if welding is carried out with a "dagger" melt lening, that is, with "sharp" focusing and a maximum penetration depth. Additionally, the signal from the output of the filter 7 is analyzed in the analyzer 11 frequency and phase, which allows you to set the desired position of the focal plane of the beam when using modes of welding with "re-" or "unfocused" beam. The choice of parameters for analysis and control (the amplitude of the signal and the derivative - for welding with "sharp" focusing and the frequency and phase of the signal - for welding with "over- or" unfocused "beam) is due to their adequate connection with the controlled process, noise immunity, availability and ease of measurement. The control signal at the output of the analyzer 11 is formed at the moment when, according to the results of the analysis, it became apparent that the focal plane has taken the required position. The signal is supplied to the switch 12, the position of which is selected depending on the welding mode. The trigger 16 controls the passage through the key 17 of the counting pulses from the output of the generator 18. When the counting pulses arrive at the counting input of the counter 15, an increasing digital code is generated at its output, which is converted by a digital-to-analog converter 19 to a voltage increasing linearly. Its slew rate is determined by the pulse rate generated by the generator 18. This voltage is converted into current by the focus current amplifier 20, which enters the focusing lens 21. The control unit 14 generates signals by an external command, which set the counter 15 to a state that determines the amount of current focusing at the initial moment of the welding process, and trigger 16 to a state in which the signal at its output opens the key 17 and "allows" the passage of counting pulses only when the beam reaches a certain previously set corresponding to the beginning or the evaporation material, the power (current value) of the beam.

 At the initial moment of the welding process, the current (power) of the electron beam increases, and the magnitude of the focusing current is unchanged. With a further increase in the beam current, the trigger 16, under the influence of the signal coming from the control unit 14, goes into a state in which the signal at its output opens the key 17, and the counting pulses from the output of the generator 18 go to the first input of the counter 15. A linear increase in the current focusing. In this case, the rate of increase of the beam current is higher than the focusing current. The simultaneous increase in the values of the welding and focusing currents at the next stage of the welding process can significantly reduce the search and installation time (compared with the prototype) of the focus current for a specific welding mode. If the power of the electron beam is insufficient to evaporate the material, there is no vapor flow and the frequency of the generator 1 is unchanged; the output signals of SFD 8, analyzer 11, mixer 5 are also unchanged in magnitude.

 The presence of steam flow in the space between the plates of the sensor 2 causes a change in the frequency of the generator 1 by an amount proportional to the density of the steam stream. At the output of mixer 5, a signal appears that, after filtering by filter 7 and limited by a limiter 9, is fed to the input of the SFD 8 and analyzer 11. SFD 8 converts the input signal into a constant voltage, the magnitude of which is proportional to the change in the frequency of the generator 1. In the extremator 13, the magnitude and the rate of change of the output voltage of the SFD 8 and when the voltage reaches a maximum, which corresponds to a zero rate of change of voltage, a control si cash. In the analyzer 11, an analysis of the frequency and phase of the input signal is carried out, and upon reaching a predetermined frequency value that corresponds to the required focusing, a control signal is also generated at its first output.

 Depending on the selected welding mode, input 16.1 of trigger 16 is connected to input 12.1 or 12.2 of switch 12; mode of "under-" or "refocusing" and "sharp" focus, respectively. The control signal received at the input 16.1 of the trigger 16, puts it in a state in which the signal at its output closes the key 17, while the output of the counter 15 sets a digital code that determines the focus current for this welding mode.

 It should be noted that if, in accordance with the requirements of the technological process, it is not enough to search and once set the position of the focal plane, it is also necessary to change the position of the focal plane (this may be necessary when welding parts of variable cross-section, with radial run-outs of the part, etc.) during welding, it is possible to use information about the sign of the deviation of the signal from the original or the value obtained as a result of setting. Information on the deviation sign contained in the output voltage of the synchronous-phase detector is converted in the extremator 13 into a control signal, which from the output 13.2 through the input 12.3 from the output 12.6 of the switch 12 goes to the input 15.3 of the counter 15, which determines the direction of counting. A similar signal is generated at the output 11.2 of the analyzer 11. The use of information on the deviation sign allows adaptation of the focusing directly during welding with virtually no deterioration in the quality of the weld, since the time to detect deviations, search and set a new focus value is less (1.5 - 2) ˙10-3 s, including the time of signal conversion to SFD.

 Laboratory studies were carried out on samples of AMg-6 material and corrosion-resistant steel on an ELU-5 installation using the ELU 15/30 energy complex, KEP4 and UL-119 welding guns, at an accelerating voltage of 28-30 kV, an electron beam current of 170-250 mA ; sensor size: length - 100 mm; width - 50 mm; the distance between the plates is 40 mm.

The tests were carried out in the following sequence:
- welding at a fixed distance between the surface of the sample and the lower end face of the welding gun R = const;
- welding at R = const; while the sample is installed at an angle of 45 ^{about the} horizontal plane.

 During welding, the parameters of the information and control signals and the magnitude of the focusing current were controlled. According to the results of the control, it can be concluded that the information signal is stable in the entire power range of the electron beam and is resistant to interference from control signals.

Claims (2)

 1. A method of adaptive control of the focusing of a welding electron beam, in which information about the focusing of the beam is obtained by processing radiation from the welding zone, characterized in that, in order to improve the control accuracy, the density of the vapor stream flowing from the gas-vapor channel is used as an information signal, at points located in the joint plane symmetrically on both sides of the weld pool, at a distance from the beam axis equal to 12P, where P is the power of the radiation source, and at a height equal to twice the thickness of the weld ivaemoy parts, and to change the value of the density of the vapor flow rate of change is judged on the beam focusing.  2. A device for adaptive control of the focus of a welding electron beam, comprising an information signal sensor, a series-connected bandpass filter, a detector, an extremator, a trigger, a key, a counter, a digital-to-analog converter and an amplifier connected to a focusing lens, and a pulse generator connected to the second key input, and the control unit, the outputs connected to the second input of the counter and the first input of the trigger, characterized in that, in order to improve the accuracy of control and expansion of technological capabilities, a tunable generator, a fixed-frequency generator, a mixer, a limiter, a limiter, a frequency and phase analyzer and a switch are introduced into it, a steam flow density sensor is used as an information signal sensor, and a synchronous-phase detector is used as a detector moreover, the output of the steam flow density sensor is connected through a tunable generator to the first input of the mixer, the second input of which is connected to a fixed frequency generator and the output goes to the inputs of the bandpass filter and the amplitude limiter, the setpoint of which is connected to the limiter, the input of the frequency and phase analyzer is connected to the output of the bandpass filter, and its two outputs and two outputs of the extremator are connected to the corresponding inputs of the switch, two outputs of which are connected respectively, with the second input of the trigger and the third input of the counter.

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