SU620344A1 - Method of electric arc welding with modulated current - Google Patents

Description

The invention relates to welding and the mohset is used in dp automatic welding with a non-consumable electrode in a protective gas environment.

Of the known methods of arc welding, the closest in technopogical essence and the achieved positive effect to the invention is the method of automatic welding by modulated current with a non-melting electrode in a protective gas environment with a through penetration p. . This method involves adjusting the formation of the back side of the seam using an optical sensor, which detects the intensity of the light emitted from the back side and affects the parameters of the welding current pulse.

The disadvantages of this method are of limited use, since in many welded structures it is difficult or impossible to access the reverse side of the seam (for example, box girders), and the complexity of the system

adjustment, due to the fact that the sensor is moved synchronously with the arc and placed at a certain distance from the root of the seam and under a given angle to the surface of the product to be welded.

To improve the quality of welding and simplify the control system, the regulation of the pulse current duration is dependent on sagging of the weld pool, which is determined by comparing the arc voltage in the interval of current flow of the pulse with the reference value, the pulse current is turned off.

FIG. 1 is a functional diagram of the proposed device for the implementation of the proposed method; in fig. Figure 2 shows the voltage and current plots.

In the welding circuit of the power supply source 1, a ballast resistance 2 is included, which limits the current during a pause 1y, which is shunted by a thyristor switch 3 during a pulse. Modulated current is obtained by turning the thyristor switch 3 on and off. A signal arriving at the thyristor switch 3 from the unit 4 comparisons through the amplifier 5, switches on the current of the dy. Starts jogging pause J. After a time equal to the duration of switching on the tapping pause nut tf, the signal received in block 6 of the die-pause formation switches on the pulse current CJ (j. Reference voltage) The reference voltage generation unit 7 generates the reference voltage. In this case, the current of the pulse of the charger} pause is set by the program pause duration tjq, and the duration of the impulse -Lu during the welding process is changed depending on the state of the weld pool, which is judged by the amount of back sag. liquid metal during an impulse. The arc voltage depends on the welding bath. It is defined as the sum of the voltage drops on the open and hidden arc length components. The arc component that is open remains constant for the specified welding conditions and hidden - varies depending on the state of the weld pool. During the flow of imulse current J (j under the influence of arc pressure and the increasing weight of the weld pool, the sag of the weld pool increases, which leads to an increase in the hidden allowed to guide the arc length, thus to increase the overall voltage dugii it. This voltage is continuously compared with the reference voltage UQ, which is used to set the critical sag of the weld pool. An increase in sagging above the critical level leads to burn-through. When the arc voltage Ug reaches the reference voltage U, i.e. At the moment of critical sagging of the weld pool, the pulse current is switched off by the feedback signal and a pause current begins to flow. The arc pressure is reduced and the sagging of the weld pool is reduced by the action of surface tension. The molten metal occupies an equilibrium state and crystallizes. After a pause, the current is turned on and the process continues. Adjusting the pulse duration of the welding current depending on the amount of sagging of the weld pool eliminates vaprovary and burnout when the gap between the products being welded changes, the edges become blunt and there are other disturbances, such as changes in heat sink conditions at the beginning and in the edge of the welding process. The use of the proposed method, electric arc welding provides an extension of the possibilities of applying the method, and simplifying the control system in comparison with known methods. Formula: Products The method of electric arc welding with a modulated current with a non-melting electrode with automatic control of the formation of the reverse side of the seam by varying the pulse duration of the welding current, characterized in that, in order to improve the quality of welding and simplify the control system, the pulse current duration is controlled depending on sagging of the weld pool and at the point of achieving critical sagging of the weld pool, which is determined by comparing the voltage across the arc to The protrusion of the eye of the impinge with a reference value, the pulse is turned off Sources of information taken into account in the examination: 1. US Patent No. 3702915 l. 219-137, 1973.

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