RU2146583C1 - Method for welding by non-consumable electrode with immersed arc - Google Patents

Abstract

FIELD: welding production. SUBSTANCE: welding is realized by alternative current of immersed arc of non-consumable electrode at using rectangular pulses of alternative current. Melt metal of welding bath is subjected to action of lengthwise magnetic field in period of inverse-polarity pulse. Ratio of direct and inverse polarity electric current pulses is 10:1. EFFECT: possibility of enhancing formation of welded seam due to elimination of single-side notch. 1 ex

Description

 The invention relates to mechanical engineering and can be used in the welding industry.

 A known method of welding by a submerged arc, in which to eliminate the undercut in order to improve the quality of the formation of the seam, a second pass is performed by the surface arc with a reduced current and increased voltage on the arc [Welding in mechanical engineering / Handbook t.1 / ed. N.A. Olshansky - M.: Mechanical Engineering, 1978, p.221].

 The disadvantages of the analogue are a decrease in the productivity of the process with an increase in labor and energy costs, the inadmissibility of re-heating of a number of materials at low heat input (for example, the possibility of sticking the welding zone).

There is a method of arc welding in a protective gas environment, in which, in order to improve the quality of the formation of the weld, forced pressure is applied to the molten metal in the caudal part of the bath [MKI ⁴ AS USSR N 1240530 B 23 K 8/13, 1986].

 The disadvantages of the analogue are the significant consumption of scarce protective gas, leakage of liquid metal onto the surface of the welded edges, unacceptably high rates of cooling of the weld metal for many materials.

 A known method of arc welding using a longitudinal reversible magnetic field to control the hydrodynamics of the melt [Magazine "Welding", 1975, N 11, p. 3 - 5].

 The disadvantage of the analogue is that the reversible magnetic field used in the method does not provide a displacement of the melt in the direction of a one-side undercut.

The closest in technical essence and the achieved result is a method of electric arc welding with modulated current with a low frequency [IPC ⁶ AS USSR N 508356 B 23 K 9/16, 1976].

 The disadvantages of the prototype are a decrease in the productivity of the process due to the periodic decrease in current; the need for a special device that provides periodic vertical rise and lowering of the electrode, synchronized with a change in current; small changes in the modes can lead to "freezing" of the electrode and thereby disruption of the process.

 When welding with a submerged arc in one pass of materials with a thickness of more than 5 mm, due to high currents in the molten metal, significant volume electromagnetic forces arise, directed to the axis of the weld. As a result, undercuts occur at the edges of the seam. The reduction of undercuts can be achieved by significantly reducing the welding speed, however, in this case, the main advantage of the method is lost. A two-sided symmetrical undercut occurs when the current lead is placed strictly along the seam axis. In real designs, the current lead is usually placed on one side of the seam, as a result of which the current density from the current lead is greater. This leads to a violation of the symmetry of the cross section of the seam and there is a one-sided undercut from the side opposite to the current supply.

 The problem to which the invention is directed is to improve the formation of a weld by eliminating a one-side undercut.

 The problem is achieved in that in the method of welding with a non-consumable electrode by a submerged arc with the longitudinal magnetic field acting on the molten metal of the weld pool during welding, rectangular AC pulses are used with a ratio of current pulses of direct polarity and reverse polarity 10: 1, and on the molten metal of the weld pool by means of a solenoid they act with a longitudinal magnetic field during the period of a pulse of reverse polarity.

 In this case, the magnetic field induction vector is directed to the surface of the sheets to be welded. In this case, the movement of the weld pool metal from the current supply side is inhibited, and from the opposite side (i.e., from the side of a possible undercut) is accelerated. This eliminates unilateral undercut and weld asymmetry.

 An example of a specific implementation of the method.

 Samples are welded from steel 12X18H10T with a thickness of δ = 12 mm.

 Welding begins on a technological plate of the same material, gradually increasing the current and the deepening of the electrode.

Steady-state welding mode: welding current I = 600 A; arc voltage U _d = 12 V; welding speed V _St = 10 m / h

 The magnitude of the magnetic induction of the solenoid is B = 0.025 T.

 Welding is carried out by pulses with a frequency of 50 Hz. The time of the reverse pulse, i.e., the on-time of the solenoid, is 0.018 s.

 When welding without a solenoid, the samples had a one-side cut under the depth of 1.5-2.0 mm. The use of a solenoid completely eliminated the undercut. Thus, the proposed method allows to eliminate a one-sided undercut and improve the shape of the seam without the use of filler material and re-melting of the seam.

Claims (1)

 A method of welding with a non-consumable electrode by a submerged arc, including conducting welding with alternating current, characterized in that they use rectangular AC pulses with a ratio of current pulses of forward and reverse polarities 10: 1, and the molten metal of the weld pool by means of a solenoid is affected by a longitudinal magnetic field during the pulse period reverse polarity.