RU144976U1 - DEVICE FOR MONITORING AND CONTROL OF BEAM FOCUSING IN ELECTRON BEAM METAL WELDING - Google Patents

Abstract

A device for monitoring and controlling beam focusing in electron beam metal welding, comprising an electron collector, a load resistor connected to the collector via a bias source, first and second analog-to-digital converters, a synchronous storage unit, a digital-to-analog converter, a unit for measuring the current of deflecting coils, PID -regulator, control unit for current of focusing coils, control unit for current of deflecting coils and sawtooth or sinusoidal oscillator connected to the input of unit current control of the deflecting coils and with the first input of the focusing coil current control unit, while the second input of the focusing coil current control unit is connected to the output of the PID controller, the input of which is connected to the output of the digital-to-analog converter, the input of the digital-to-analog converter is connected to the output of the synchronous storage unit, the inputs of which connected to the outputs of the first and second analog-to-digital converters, while the input of the first analog-to-digital converter is connected to the electron collector, and One of the second - with the output of the current measuring unit of the deflection coils.

Description

The technical field to which the utility model relates.

The invention relates to the welding or cutting of metals by electron beam, namely, to control circuits for these purposes.

State of the art

A device for monitoring and controlling beam focusing in electron beam welding of metals, comprising an electron collector, load resistors with bias sources connected in series to them, a switch connected to load resistors, first and second filters, first and second amplitude detectors, a signal conversion unit , trigger and series-connected pulse generator with a control key, a pulse counter and an analog-to-digital converter, the output of which is designed to be connected I’m connected to the focusing lens of the electron gun, the inputs of both filters connected to the switch, the outputs of the filters connected to the inputs of the amplitude detectors, the outputs of the latter connected to the inputs of the signal conversion unit, and the output of the signal conversion unit connected to the input of the trigger, the output of which is connected to the input of the generator control key pulses (Aut. certificate. USSR No. 1468700, IPC B23K 15/00, 1989).

Signs of the known device that match the features of the claimed utility model are that the device contains an electron collector, a load resistor with a bias source connected in series to it, a pulse generator, and an analog-to-digital converter.

The reason that prevents obtaining a technical result in a known device, which is provided by the claimed utility model, is the impossibility of ensuring regular fluctuations in the current of the focusing system relative to the required value due to the stochasticity of the processes occurring in the weld pool with a large penetration depth of the metal.

The closest analogue (prototype) is a device for monitoring and controlling beam focusing in electron beam welding of metals, containing an electron collector, a modulation unit, the outputs of which are designed to be connected to an electron gun and a focusing lens, a bias voltage source and a load resistor connected in series to an electron collector, a bandpass filter, the input of which is connected to a load resistor, an amplitude detector connected to the output of the bandpass filter, a synchronous detector p, the input of which is connected to the output of the amplitude detector, a focus current control unit, the output of which is intended to be connected to the focusing lens, and a focus setting unit, the output of the focus setting unit being connected to one of the inputs of the focus current control unit, the second input of this unit is connected to the output of a synchronous detector (see the description of the invention to patent RU No. 2183153 C2 ", IPC B23K 15/00, published 10.06.2002).

The features of the known device that match the features of the claimed utility model are that the known device comprises an electron collector, a modulation unit, a bias voltage source and a load resistor connected in series to the electron collector, a bandpass filter, a synchronous detector, and a focus current control unit.

The reason that prevents obtaining a technical result in a known device, which is provided by the claimed utility model, is that sufficient accuracy of control and focus control of the beam is ensured only when welding with a modulated beam, and for real-time monitoring directly during welding, low-frequency search oscillations of the electron focus are required beam, which adversely affects the quality of the formation of the weld.

Utility Model Disclosure

The problem to which the utility model is directed is to improve the quality of the weld formation in the deep penetration mode by an oscillating electron beam.

The technical result, which mediates the solution of this problem, is to increase the accuracy of operational control in the process of controlling the focus of the electron beam during welding in the mode of deep penetration by an oscillating electron beam. Thanks to the introduction of an additional oscillation of focusing of the electron beam, in phase with respect to the oscillation of the longitudinal deviations of the electron beam, the linearity of the dependence of the information parameter on the focusing mode is improved, monotonicity is ensured in a wide range of modes, and the signal-to-noise ratio increases. These advantages can improve the accuracy and speed of the operational control of the focusing of the electron beam, as well as simplify the implementation of the device for implementing the method. The high-frequency oscillation of the longitudinal deviations of the electron beam used in conjunction with the in-phase oscillation of its focus further improve the quality of the weld formation. The device in the process of electron beam welding provides the necessary sequence of steps for oscillation, measuring the secondary current and the current of the deflecting coils in the plasma, processing the measured signals and adjusting the focus of the electron beam. These advantages of the claimed device provide high quality welding in the deep penetration mode and allow with high accuracy and speed to carry out operational control of the focusing of the electron beam.

A technical result is achieved in a device for monitoring and controlling beam focusing in electron beam welding of metals in that the device contains an electron collector, a load resistor connected to the collector via a bias source, first and second analog-to-digital converters, a synchronous storage unit, digital-to-analog transducer, deflecting coil current measuring unit, PID controller, focusing coil current control unit, deflecting coil current control unit, and sawtooth generator or sinusoidal oscillations connected to the input of the deflecting coil current control unit and to the first input of the focusing coil current control unit, the second input of the focusing coil current control unit is connected to the output of the PID controller, the input of which is connected to the output of the digital-to-analog converter, and the digital-to-analog input the converter is connected to the output of the synchronous storage unit, the inputs of which are connected to the corresponding outputs of the first and second analog-to-digital converters, while the input of the first analog the logo-digital converter is connected to the electron collector, and the input of the second one is connected to the output of the current measuring unit of the deflecting coils.

New features of the claimed device relative to the prototype are the presence of the first and second analog-to-digital converters, a synchronous storage unit, a digital-to-analog converter, a unit for measuring the current of deflecting coils, a PID controller, as well as in the electrical connections of the listed structural elements.

Brief Description of the Drawings

In FIG. 1 shows a block diagram of a device for monitoring and controlling beam focusing in electron beam welding of metals.

In FIG. 2 shows a diagram of the reference signal g (t) for realizing synchronous accumulation generated from the signal in the deflecting coils and representing rectangular oscillations of short duty cycle (1 - waveform of the current of the deflecting along the joint of the coil (Osc (t)); 2 - the generated reference signal (g (t + τ),); 3 - shift of the reference signal relative to the signal of the deflecting coils (τ)).

In FIG. Figure 3 shows the function S (τ), which is the result of processing the secondary signal by the synchronous accumulation method, depending on the shift of the reference signal (a) and on the signal in the deflection coils (b), according to the formula

,

where t ₀ is the sampling time.

In FIG. Figure 4 shows the dependence of the delay value Δτ _{0 of the} function S (τ) on the degree of focusing ΔI _{f of the} electron beam obtained as a result of a multivariate experiment at various oscillation frequencies (1 - frequency 450 Hz; 2 - frequency 630 Hz; 3 - frequency 960 Hz).

In FIG. Figure 5 shows the dependence of the delay Δτ ₀ on time during welding at a constant underfocused mode (ΔIf = -10 mA)

Utility Model Implementation

A device for monitoring and controlling beam focusing during electron beam welding of metals (Fig. 1) contains an electron collector 1 to which a load resistor 3, a current measuring unit 4 of the deflecting coils 16, the first 5 and second 6 analog-to-digital converters are connected through an offset source 2, synchronous storage unit 7, digital-to-analog converter 8, PID controller 9, focusing coil 15 current control unit 15, deflecting coil 16 current control unit 11, and sawtooth or sinusoidal oscillator 12. In FIG. 1 also shows the actual device for electron beam welding of metals (vacuum chamber 13, electron gun 14, focusing coils 15, deflecting coils 16), as well as the welded article 17. The input of the first analog-to-digital converter 5 is connected to the collector 2, and the input of the second analog-to-digital converter 6 is connected to the output of block 4. The input of the digital-to-analog converter 8 is connected to the output of block 7 of synchronous storage, the inputs of which are connected to the corresponding outputs of the first 5 and second 6 analog-to-digital converters Atelier. The generator 12 is connected to the input of block 11 and to the first input of block 10. The second input of block 10 is connected to the output of the PID controller 9, the input of which is connected to the output of the digital-to-analog converter 8.

The operation of the device are as follows.

A sawtooth or sinusoidal oscillator 12 generates an oscillation signal of a given frequency. The current control unit 10 of the focusing coils 15 summarizes the signal from the output of the PID controller 9 with the signal from the generator 12, amplifies the result and sets the corresponding current to the focusing coils 15 for oscillating the beam focus. The signal from the generator 12 also arrives at the current control unit 11 of the deflecting coils 16, amplifies and sets the corresponding current of the deflecting coils 16, which provide oscillation of the longitudinal deflections of the beam (along the junction of the welded article 17) in phase with the oscillation of the beam focus. The input of the analog-to-digital Converter 5 receives a signal from the collector 1 of electrons. The input from the analog-to-digital converter 6 receives a signal from the current measuring unit 4 of the deflecting coils 16. From the outputs of the analog-to-digital converters 5 and 6, the voltage signals on the collector 1 and the current of the deflecting coils 16 are transmitted to the synchronous storage unit 7. In block 7, the current value of the electron collector is calculated by the formula I _к = (ε-U) / R, where ε is the magnitude of the emf of the bias source 16, U is the voltage at the electron collector 14, R is the resistance of the load resistor 15. Further, in this same block, the value of the collector current I _in conjunction with the current signals I _none deflecting coils, is processed by the synchronous accumulation.

To implement synchronous accumulation of the current signal of the deflecting coils, a reference signal g (t) is formed, which is a rectangular oscillation of a small duty cycle (Fig. 2). The reference signal g (t + τ), shifted by the time τ (0 <τ <T, where T is the period of the signal in the deflecting coils), is multiplied by the secondary current signal I _k and then is integrated (summed or averaged) over time t. The result of these transformations is the function S (τ) (Fig. 3), which describes the change in the result of synchronous accumulation depending on the shift of the reference signal

,

where t ₀ is the sampling time, which was 300 ms.

The function S (τ) describing the change in the result of synchronous accumulation has a characteristic delay relative to the current signal in the deflecting coils (Fig. 3). The value Δτ ₀ monotonically depends on the degree of focusing ΔI _{f of the} electron beam (Fig. 4) and assumes values equal to zero during acute focusing of the electron beam. From block 7, the quantity Δτ ₀ through the digital-to-analog converter 8 enters the PID controller 9, which, together with the block 10, controls the focusing current of the electron beam, maintaining the aforementioned delay value Δτ ₀ at a constant level corresponding to a certain degree of focusing of the electron beam relative to the surface of the product 17 . In particular, maintaining the value of the retardation Δτ ₀ zero provides maximum power at a given speed and welding penetration depth that corresponds to the maxi cial specific power released in the welding zone. Oscillation of longitudinal deviations of the electron beam, according to the claimed method, is preferably carried out along the welded joint. However, it should be noted that x-shaped oscillations can also be used and with the use of other special forms of trajectories to further improve the quality of welding. In this case, the focus oscillation is carried out in phase with the signal of the coil whose current is responsible for the deviation along the junction.

The device was experimentally tested on 12Kh18N10T steel samples on an electron beam welding machine with an inverter power source with an accelerating voltage of 60 kV and a power of 6 kW. Oscillation longitudinal deviations of the electron beam (along the junction) was carried out by introducing into the corresponding deflection coil current I _none periodic sawtooth oscillation. The distance from the cut of the electron gun to the product was 100 mm. The electron collector for the selection of the secondary current in the plasma was a disk with a diameter of 17 mm, located at a distance of 35 mm from the welding zone. Active experiment planning was used. Four factors varied: welding power - P; oscillation sweep size - 2A; oscillation frequency of the electron beam - f; the amplitude of the focusing current I _fm ; the degree of focusing of the electron beam is ΔI _f = I _f -I _f0 , the difference between the values of the focusing current during welding I _f and the sharp focusing current providing the maximum depth is I _f0 . The welding speed was 5 mm / s. The depth of penetration during sharp focusing was 10 ... 18 mm. The limits of variation of the factors are presented in table. one.

Table 1. Factors ΔI _f , mA f Hz 2A mm I _fm , mA P kW Lower limit of variation -twenty fifty 0.4 0 1.5 Upper limit of variation twenty 1400 3.5 fifteen 2.5

During welding passes using a computer information-measuring system equipped with a multi-channel analog-to-digital interface, a current was recorded in the circuit of the collector 1 of secondary electrons at a positive potential of 48 V (Fig. 1). At the same time, signals proportional to the current in the deflecting coils 16 were recorded. The registration results were recorded in a file for further processing. The sampling frequency during analog-to-digital conversion in the experiments was 400 kHz for two measuring channels. All melted samples were subjected to further processing in order to produce longitudinal macro sections.

The signal of the secondary current in the plasma from the electron collector installed above the welding zone and the current signal in the deflecting coils were processed using a computer information-measuring system equipped with a multi-channel analog-to-digital interface.

In FIG. Figure 4 shows graphs expressing the dependence of the delay Δτ ₀ on the degree of focusing ΔI _f , constructed using the regression equation obtained by processing the experimental results at three oscillation frequencies. Graphs are plotted at constant welding power P = 2 kW, the sweep size of the oscillations 2A = 1 mm, and the amplitude of the oscillations of the focusing current, providing focus scanning, I _fm = 8 mA. The graphs demonstrate that the combined use of in-phase focus oscillations and longitudinal beam deviations provides good linearity of the dependencies. The curves in FIG. 4 monotonously decrease with increasing degree of focusing and take zero values in the region of sharp focusing, which provides the maximum penetration depth. In FIG. Figure 5 shows the time lag Δτ ₀ as a function of time during welding with a constant unfocused mode (ΔI _f = -10 mA). When implemented according to the claimed method, the use of additional focal scanning in phase with the oscillation of the longitudinal deviations of the electron beam provides relatively small fluctuations Δτ ₀ in time, which demonstrates a high signal to noise ratio.

Thus, the results obtained using the claimed device are characterized by better linearity, greater stability in time, better ratio / signal to noise ratio and allow more accurate identification of the focus mode. These advantages can improve the accuracy and speed of operational control of focusing of the electron beam.

Claims (1)

A device for monitoring and controlling beam focusing in electron beam metal welding, comprising an electron collector, a load resistor connected to the collector via a bias source, first and second analog-to-digital converters, a synchronous storage unit, a digital-to-analog converter, a unit for measuring the current of deflecting coils, PID -regulator, control unit for current of focusing coils, control unit for current of deflecting coils and sawtooth or sinusoidal oscillator connected to the input of unit current control of the deflecting coils and with the first input of the focusing coil current control unit, while the second input of the focusing coil current control unit is connected to the output of the PID controller, the input of which is connected to the output of the digital-to-analog converter, the input of the digital-to-analog converter is connected to the output of the synchronous storage unit, the inputs of which connected to the outputs of the first and second analog-to-digital converters, while the input of the first analog-to-digital converter is connected to the electron collector, and One of the second - with the output of the current measuring unit of the deflection coils.