SU662297A1 - Method of controlling electric heating process at spot and seam welding - Google Patents

Description

one

The invention relates to the field of resistance spot and seam electric welding.

A known method of controlling the electric heating process in spot and seam welding, in which the regulation of the welding process is carried out by stabilizing the average value of the welding current through a closed-loop automatic control system with feedback. A decrease or increase in the welding current is compensated for by appropriate correction of the firing angle of the power thyristors of the welding machine interrupter contactor, thereby stabilizing the specified average value of the welding current 1.

The disadvantage of this method of regulation is the lack of control over the wear of the working surface of the electrodes, the change in the compression force, and the welding time.

Of the known methods, the closest to the proposed method is a method of controlling the electric heating process in spot and seam welding, in which the electrical energy released in the welding contact from the moment the welding current is applied to the current time is measured, and the current is switched off when electrical energy is reached setpoint 2.

The disadvantage of this method is the instability of the quality of welding. This is due to the fact that it does not take into account the dependence of the amount of energy dosed to form a good-quality welded joint on the heating time, the compressive force of the welded products, the wear of electrodes or rollers, the shunting of the welding current by adjacent points or seams.

The aim of the invention is to improve the accuracy of electric heating control and improve the quality of welding under the conditions of changing the parameters of the welding circuit.

The goal is achieved by the fact that

Claims (2)

According to the proposed method, the amount of electrical energy in the welding contact is obtained by measuring the sum of two signals, one of which is proportional to the actual welding current flow time, and the other signal is inversely proportional to the contact resistance average during the welding time, and the specified energy value is determined as the sum of these signals and this value determined by the selected welding mode. The drawing shows a block diagram of a device for controlling an electrical heating process that implements the proposed method. This device contains a welding machine 1, a current sensor 2, a voltage sensor 3, a time sensor 4, a multiplying device 5, an integrator 6, an inverter 7, a dividing unit 8, an integrator 9, a b.uch 10 division, a multiplying device 11, an output adder 12, a multiplying device 13, a source 14 of an adjustable stabilized voltage, a switching device 15. During the welding cycle, electrical energy released in the welding contact is measured. To do this, multiplying the signals from current sensor 2 and voltage sensor 3 proportional to the welding current in the parts and the voltage applied to the welding contact, respectively, in the multiplier device 5, respectively, the resulting product is integrated in real time in the integrator 6. At the integrator output 9 receive a voltage proportional to the actual welding energy. The specified energy value is defined as the sum of the following values (1), (trf-t "") -Kg {g "-g" ") where QO is the value of the energy supplied to the welding contact under nominal conditions, i.e. t" g tet,, there is no shunting of the welding current, no wear of the electrodes, the compressive force of the parts is equal to the nominal value in this case: GEEGE cdm 5 Ki And Kg are coefficients depending on the metal of the parts to be welded and their thickness; let and tet "oN are the actual and nominal welding times, respectively; gee and gmnvm are the average contact resistance and nominal contact resistance during welding, respectively. Since, for a given material and thickness of details, the values of t gSiok and g 9Ets are constant, the expression (1) can be written in a simplified form: Qj Q + K | .r,., (2) where Q QO - K (t (L4 ', M + Kageenvm) (3) The welding machine is disconnected at the time of equality of the energy released in the welding contact with a given value. To correct the set value of the energy being dosed, x changes in welding circuit parameters are measured during the welding process, the actual duration of heating and the average electrical resistance of the welding contact during welding.The voltage is removed from sensor 4 and is proportional to the welding time. The average resistance of the welding contact is determined as follows ohm: the signal from the voltage sensor 3 is divided by the current sensor 2 signal in dividing unit 8, the result of dividing, integrating in real time by integrator 9 and dividing by the actual welding time removed from sensor 4 in dividing unit 10. In multipliers 11 and 13, values proportional to CrGe and K | tot, respectively, are obtained.At the output of divider 14, stresses establish a voltage proportional to the value of Q from relation (2). The energy setpoint is obtained by summing the output voltages of blocks 11, 13, and 14 at the input of the adder 12. From the inverter 7, a signal proportional to the value of the actual energy taken with the opposite sign is sent to the sum. The machine is switched off by switching device 15 at the moment when the signals from blocks 7, I, 13 and 14 give zero voltage at the output of the adder 12. Experimental data showed that the manufacture of flame tubes by the proposed method included in the high and low pressure blocks turbines GT-100, increases the service life of these units by 2 times. Claims The method of regulating the electric heating process in spot and groove welding, in which the electrical energy released in the welding contact is measured from the moment the welding current is applied to the current time, and the current is switched off when the electrical energy reaches a predetermined value, characterized in that , in order to increase the accuracy of electric heating control and improve the quality of welding under the conditions of changing the parameters of the welding circuit, the amount of electrical energy in the welding contact was obtained by measuring the sum of two signals, one of which is proportional to the actual welding current flow time, and the other signal is inversely proportional to the contact resistance average for the welding time, and the specified energy value is determined as the sum of these signals and a constant value determined by the selected mode welding. Sources of information taken into account in the examination 1.Orlov B. D. “Technologists and equipment for resistance welding, M., Mashinostroenie, 1975, p. 494-495. 2. USSR author's certificate number 285737, cl. In 23 K 11/24, 1974.