SU1731518A1 - Method of controlling the arc spot welding process and device thereof - Google Patents

Abstract

The use of arc welding of electric rivets, predominantly with a non-consumable electrode in the environment of protective gases in the engineering industry of shipbuilding and aircraft building. Invention: one adjustable parameter is used - welding duration. In this case, the average deviation of the main parameters affecting the welding process for a given period of time is determined. The duration of welding is determined by the total deviation of all parameters. Determination of average values is performed by comparing the actual measured by the sensors and the set values of the monitored parameters, from the gain, depending on the coefficient of influence of this parameter on the welding process, the summation and integration of the amplified signals, and control by the resulting signal by the power contactor 2 with the ffl, 3 silt

Description

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The invention relates to electric welding with electric rivets, mainly with a non-melting electrode in a protective gas environment and can be used in mechanical engineering, shipbuilding, aircraft manufacturing, and construction.

A known method for regulating the welding process by electric rivets with a non-consumable electrode, in which the parameters of the welding process (current, arc length, protective gas consumption, welding time, and others) is set before the welding process, initiates an arc, forms an electric rivet and turns off the arc after holding for a specified welding time The method is carried out with the help of a device containing a gass flow sensor and others as well as measuring priors showing the value of Psfamegrov

With this method of adjustment, in the period between welding individual points or in the process of welding a point, the set mode parameters change due to various disturbing effects. For example, the welding current changes due to fluctuations in the network voltage. Because of this, the stability of point formation is disturbed, the size of the point changes, the quality of welding deteriorates. The variation in the size of points and the quality of welding leads to uneven loading of points during the operation of the facility, reducing its reliability.

There is also known a method for regulating the welding process by electric rivets with a non-melting electrode, in which the parameters of the welding process are set, prior to the start of welding, an arc is measured.

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adjustable parameters, compare them with predetermined values and maintain welding parameters at a predetermined level during the welding process, form an electric rivet and turn off the arc after a specified welding time. The method is carried out with a device containing current sensors, gas flow and other nodes comparing the values of monitored parameters with given, amplifiers, regulators of monitored values.

A disadvantage of the known method and device is their complexity, due to the need to maintain at a given level several adjustable parameters, which is very difficult with a short duration of the welding process of electric rivets. The control device must contain a controller for each monitored parameter.

The aim of the invention is to simplify the method of controlling the welding process with electric rivets, as well as the device for its implementation by reducing the number of adjustable parameters.

The goal is achieved by the fact that in a known method of controlling the welding process by electric rivets, at which the process parameters are measured, their deviation is determined from the given ones and the welding control process is carried out by the deviation value, the average deviation value of each measured parameter d P | slave for a given length of time, and the duration of welding is changed by the value of Ate c. determined by formula

d t

 u ipao

A Pi.

where dt / d Pipa6 is derived from the dependence of welding time on the i-ro parameter for this parameter at the operating point:

n is the number of parameters taken into account.

A device for regulating the welding process with electric rivets, containing a current sensor, a gas flow sensor, a temperature sensor of the elements to be welded, nodes comparing the values of monitored parameters with the set ones and amplifiers, a sampling-storage device, an adder, an integrator, a comparator, a control device and a power switch, the output of the sampling-storage device is connected to the input of the adder, the output of the adder is connected to the input of the integrator, and the output of the integrator is connected to the comparator, the output of the comparator connected to the power key, the control device is connected to the sample storage device and the integrator.

FIG. 1 shows a three-dimensional

the space in which each point of the surface A, B, C, D defines a set of modes causing a welded point with a diameter of 6 mm DCp, taking into account the three mode parameters; on

0 FIG. 2 is a functional diagram of an apparatus for carrying out the proposed method; in fig. 3 - output waveform output voltage from current sensor (a), output voltage after amplifier (b), output

5 adder voltage (c), integrator output voltage (d), comparator output voltage (d).

In the diagram (Fig. 3), the following notation is used: Ozad.1 - voltage reference of the welding current; 11zad.2 - voltage control unit temperature of the part; Kzad.z tension of the gas flow control unit; Uzad.z - voltage control unit welding time. The device (Fig. 2) consists of a source

5 1 power supply, burner 2, power contactor 3, current sensor 4, welded elements 5, pressure sensor 6 gas flow meter 7 with temperature sensor 8 installed on it, comparison devices 9-11, amplifiers 12-14 with adjustable gain factors, device 15 sampling-storage, adder 16 lining 17, the in- grator 18, comparator 19 of the control device 20, buttons 21.

5 The essence of the method is

that the stabilization of the diameter of the electric rivets is carried out by not stabilizing the change -. process parameters, and the adjustment of only one parameter mode0 welding time. The welding time is controlled depending on the results of the comparison of the measured parameters with the set points and taking into account the type of welding time dependences on these parameters at a constant

5 diameter electric rivets. To do this, we first determine the dependence of the diameter of the electric rivets on the welding time for given parameters that affect the diameter of the electric rivets (current, temperature of the parts, flow rate of the plasma gas, and others). The controlled parameters are divided into two types: individual electric rivets varying between welding and varying during the welding process. Number

5 monitored parameters not limited.

The multidimensionality of the dependence of the diameter of the welded point on the technological parameters of the welding process is graphically displayed by a set of n-dimensional points

space. Welding modes for obtaining a welded point of a given diameter are displayed in this space by a certain surface. As an example in FIG. Figure 1 shows a three-dimensional space in which each point of the surface A, B, C, D defines a set of modes causing a welded point with a diameter of 6 mm DCp, taking into account three mode parameters. On this surface, the selected operating point P is indicated, for which the welding current ICB is slave 125 A, tee 3.5 s Tdet 20 ° C. The line DE for crossing the surface of the ABC and DEC plane is characterized by a temperature Tdet 20 °, determines the dependence of the welding time on the welding current to obtain a weld point with a diameter of DCp 6 mm. The LM line of the intersection of the ABC surface, the LJIM plane, characterized by the welding current value S 125 A, determine the dependence of the welding time on the temperature of the parts before welding Tdet. for producing electric rivets with a diameter of 6 mm. FIG. Figure 1 also shows the partial derivatives dtcB / dlpa6, and oChsv / cTo, which determine the angle of inclination of the tangents 1 and 2 to the corresponding DE and LM curves at the working point R. which is modeled by the proposed flowchart. The error that occurs when replacing the surface of the ABCF at the operating point on the tangent plane is small, since the random deviations of the parameters of the welding process usually do not exceed + 15% of the set value. At another operating point, the tangent plane will be defined in the same way.

The proposed scheme also takes into account the plasma gas flow rate, which is the fourth dimension and is not graphically represented.

Thus, the proposed scheme, simulating a tangent plane, which defines a set of modes for producing electric rivets of a given diameter, allows stabilizing the size of the weld points and improving the welding quality.

The method is carried out as follows.

Prior to welding, 1) 3ad 1 is set to the corresponding signal from the current sensor at rated operating current, 1ad2 voltage corresponding to the nominal temperature of the elements to be welded at the welding site, before welding, 11 backc - voltage corresponding to the nominal gas flow rate. Uchad 4 - voltage corresponding to the technologically required welding time. In accordance with the effect of this parameter on the diameter of the electric rivets, the gains of the blocks 12-14 are set. Weldable elements 5 are compressed with each

with the help of a pressure cup 7 and a lining 17. The temperature sensor 8 measures the temperature of the elements 5 in the zone where welding is to be performed. The signal from the temperature sensor 8 goes to the node 10

0 comparison, where it is compared with a given 1) ass. From the output of the node 10 of the comparison, the error signal, proportional to the temperature deviation from the set one, is fed to the amplifier 13, the coefficient

5, the gain of which is established in accordance with the magnitude of the derivative of the dependence of the welding time on the temperature of the elements 5, at a given temperature Tra. The signal amplifier 13 is fed to the input

0 device 15 sample-storage.

In such a state, the control system is located before pressing the button 21 connected to the input of the control unit 20. The control unit generates a reset signal to the integrator 18 and the command that the sampling-storage device 15 remembers the signal at the output of the amplifier 13 and stores it during the welding process of the electric rivet. Signal from Sampling Device

0 arrives at the adder 16. The signal at the output of the integrator 18 after resetting is zero. It is fed to the input of comparator 19, where it is compared with a fixed voltage level. At the output of the comparator 19, a signal is turned on, which turns on the power contactor 3. The voltage of the power source 1 through the power contactor 3 and the current sensor 4 is fed to the welded elements 5. The welding process begins.

0 The signal from the current sensor 4 (Fig. 3a) is fed to the comparison node 9, amplified in accordance with the value of the derivative (Fig. 36) dtcB / dlpa6 at the operating point depending on the welding current 1rab. (Fig. 1)

5 (right 1) and fed to the adder 16. In contrast to the temperature measured before welding, the welding current is monitored during the entire welding cycle of the electric rivets. Similarly

0, gas flow is monitored using gas flow sensor 6, comparison unit 11, amplifier 14. From amplifier 14, the signal goes to the input of adder 16. Welding time voltage

5 i3ad4 is also fed to the input of the adder 16. In the adder 16, the algebraic summation of 1bad4 and the signals from the amplifiers 12 and 14, as well as the sampling-storage device 15, takes place.

The welding current and plasma gas flow rate at the output of amplifiers 12 and 14 and the sampling-storage device 15 are zero and do not make corrections to the welding cycle time.

If these parameters deviate from the specified values in the voltage of 4. the welding time setter is corrected (Fig. 3 Sv) to obtain a welded electric rivet of a given diameter. The voltage from the output of the adder 16 goes to the integrator 18. The time during which the voltage at the output of the integrator 18 rises to a fixed level of the trigger voltage of the comparator 19, inversely proportional to the average value of the input voltage (Fig. 3g). Upon reaching the voltage at the output of the integrator 18 of a fixed level of operation of the comparator 19, the control voltage is removed at the output of the comparator (Fig. G) and the power switch 3 turns off the welding current. Electrofishing process is finished. In this state, the circuit is before welding the next point. When the pressure cup 7 is installed at the place of the next point, the information about the temperature of the sheets is again taken off by the temperature sensor 8 and then the process repeats.

Example. Plasma welding with electric rivets of elements from aluminum alloy AMts with a thickness of 1 + 1 mm with a compressed three-phase arc was carried out. Operating current in parts 1rab. 150 A, plasma-argon gas flow rate of л 4 l / min, diameter and length of the nozzle outlet dc 1s 4 mm, length of the open section of the arc column 10 3 mm, electrode diameter ds 4 mm, We chose as recorded parameters when stabilizing the electro-rivet current, argon consumption and temperature of elements at the weld site. Preliminarily, dependences of the welding time of a point of a given diameter on current I, flow rate (t, temperature of the welded elements in the vicinity of the operating parameters of the process: 1rab. 150 A, C 4 l / min, Trab. 293 K, Derivatives to static characteristics at operating points were dtcB / dl -0.02 s / A, dtCB / dЈ -0.02 s2 / g, dtcs / dT -0 005 s / K. In accordance with these values, the gains of the amplifiers in the circuit (Fig. 2) of the method were set Then, using a control circuit, ten electromixers are welded at nominal current values perature elements argon flow. lo welding time was 3.5 seconds. The half-sum of the upper and lower diameters with plug averaged 7.2 mm.

Then, welding was performed with the introduction of parameter deviations from nominal values. The current was I 160 A, Ј 4.5 l / min, T 343 K. When welding using the proposed method, welding was carried out using the circuit shown in FIG. 2, without changing the reference voltages 113ad2, OzadZ, and 3ad4, which remained the same as in the first series of welds. The circuit provided arc shutdown 3.0 s after the start of welding, and the sum of the upper and lower diameters of the electric blind was on average 7.3 mm.

When welding on the same modes (I 160 A, (4.5 l / min, T 343 K) with the control scheme turned off and the welding time of 3.5 s, the average diameter of electric rivets was 8 mm.

The proposed method and device for its implementation allows to simplify the process of stabilization of a welded electric riveting joint by reducing the number of adjustable process parameters to a single welding time. The use of this parameter as a controlled one does not require special control devices for other technological parameters of current, flow rate, temperature, and others that are difficult to implement. At the same time, compared with the rigid assignment of the welding modes, the stability of the weld area is increased by 20-40%, and compared to the automatic maintenance of the specified modes at a set level, the control circuit is significantly simplified, as a result of which the control reliability increases by 20-30%.

Claims (2)

1. The method of regulating the welding process with electric rivets, in which the process parameters are measured, determines the magnitude of their deviation from the set values and the magnitude of the deviations regulate the welding, characterized in that, in order to simplify the regulation of the welding process by reducing the number of adjustable parameters, are the average value of DR | deviations of each measured parameter for a given period of time, and the duration of welding is changed by the value of DsV, determined by the formula dt & dPipaa DR |, dt d P ipa6 derivative dependency welding time from i-ro parameter by this parameter at the working point; n is the number of measured parameters. 2. A device for controlling the welding process by electric rivets, comprising a current sensor, a gas flow sensor, a temperature sensor of the elements to be welded, each of which is connected to a corresponding comparison unit, amplifiers, and a control device characterized in that, for the sake of simplicity, it contains sampling-storage device, sum fat, dzr, ®UZ.i a torus, an integrator, a comparator, the control device is connected to the inputs of the sample storage device and an integrator, the second input of the sample storage device is connected to the temperature sensor through the amplifier and the comparison node, and the second input of the integrator is connected to the adder output corresponding to the output of the sample-hold device.  6lm  L ix g U / FIG. 2 a USvLtS Uuit (