RU1775252C - Method of girth welding by magnetic field-controlled arc - Google Patents

Abstract

Usage: welding of pipes with tube sheets in the energy and petrochemical engineering. SUMMARY OF THE INVENTION: When welding ring joints with a magnetically controlled arc, a ring non-consumable electrode and an asymmetric reversible magnetic field are used. Before reversing the magnetic field, it is briefly turned off. 1 C.p. f-ls, 3 ill.

Description

The invention relates to welding production, in particular to methods for welding ring joints, mainly pipes with tube sheets, an electric arc rotating in a magnetic field and can be used in power and petrochemical engineering.

A known method of welding annular seams, in which welding is performed using an annular electrode and a rotating, electric arc, is moved around the perimeter of the seam by a constant magnetic field;

However, due to the possibility of access to the tube sheet only from the outside, this method does not allow high-quality welding of pipes with tube sheets.

Closest to the proposed method is a method for heating metal parts with a traveling electric arc moved by a magnetic field. The method consists in alternately changing the direction of rotation of the arc as a result

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changes in the direction of the magnetic flux. In this case, the electric arc alternately shifts to the outer surface of the pipe and electrode when the influence of magnetic forces increases and to the inner edge when the effect of magnetic forces decreases;

The disadvantage of this method is the uneven depth of penetration around the perimeter of the annular weld and local melting of the end face of the non-consumable ring electrode due to the regular localization of more efficient heating during the reduction of the speed of movement of the arc while weakening the control magnetic field in certain parts of the perimeter of the weld and the end of the electrode due to the regulation symmetric reverse rotation of the ugle rotation. As a result, cooking quality and resistance of the non-consumable electrode are reduced.

The purpose of the invention is to improve the quality of welded joints by uniformly melting the welded edges around the entire perimeter of the weld and to increase the resistance of the non-masonry electrode by eliminating local overheating of its working highlander.

The goal is achieved in that the control reversible magnetic field is formed asymmetric, and before reversing the magnetic field it is briefly turned off.

New in the proposed method is the asymmetry of the control reversible magnetic field and its short-term shutdowns before reversing. The asymmetry of the control reversible magnetic field can be achieved by changing the amplitude or duration of the opposite half-periods of the current of the control electromagnet. During smaller amplitudes or a shorter half-period of the current of the control electromagnet, as well as during short-term shutdowns of the latter, the movement of the welding arc slows down. In this case, certain parts of the seam perimeter and the end of the electrode warm up more intensively, and the penetration depth of the weld metal increases. In the half-periods of greater amplitude and duration of the control current of the electromagnet, the control reversible asymmetric magnetic field will change similarly and, therefore, the welding arc will make a greater rotational movement along the ring contour in the direction of rotation of the arc, corresponding to a half-period with a longer duration and amplitude of the current of the electromagnet, which ensures periodic translational motion zones of intense heating, along an annular contour in the direction of arc rotation, corresponding to a half-cycle with Olsha amplitude and duration of solenoid current, the result is achieved by increasing the depth of penetration uniform around the perimeter of the annular weld, and elimination of local submelting end neplav luminant electrode and increase its resistance.

In FIG. Figure 1 shows an example of the asymmetric formation of a control reversible magnetic field by varying the amplitude of the opposite half-periods of the current of the electromagnet ki 5 Ika. where ki is the current amplitude in the first half-cycle, and the half-periods are ti t2, where ti is the duration of the first half-cycle, ta is. opposite half period. In FIG. Figure 2 shows the same with magnetic field shutdowns during the pause time tn before reversing the field by briefly disconnecting the electromagnet. In FIG. Figure 3 shows an example of asymmetric formation of a control reversible magnetic field by varying the duration of opposite half-periods of the electromagnet current

ti t2 with its short-term shutdowns, where the current amplitude of the opposite half-period Iki and the first half-period Ik2 are equal, and the current duration of the first half-period ti and the opposite half-period

0 are not equal, respectively, the duration of the current pauses after the first half-period tni and after the opposite half-period tn2 is not equal. Possible simultaneous combination

 asymmetric formation of a control reversible magnetic field. thereby changing the amplitude lki Ik2 and the duration ti t2 of opposite half-periods of the electromagnet current ,,.

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Welding by this method is carried out

in the following way. Set the welding device concentrically to the longitudinal axis of the welded tube with a given

5 arc spacing. The arc stop times and asymmetries of the amplitudes or durations of opposite reversal half-periods are determined by the technology. Turn on the power

0 of the electromagnetic device and in the arc gap create an asymmetric reversible magnetic field. Excite a welding arch. The interaction of the magnetic field of the arc with the magnetic field of the electromagnetic coil leads to an asymmetric reversal of the rotation of the arc with short stops of it during a change in the direction of rotation. During slow motion and short-term arc stops, certain parts of the end of the electrode and the perimeter of the seam are heated more efficiently, the penetration depth increases, In half periods of longer duration and amplitude of the control current

from a magnetic coil, the arc makes a greater rotational movement along the annular contour, which in opposite half-periods of shorter duration and amplitude, as a result, the effective

P heating receives one-way translational motion along the annular contour in the direction of arc rotation, corresponding to a half-period of the electromagnet current with a longer duration and amplitude, which

It allows one to achieve a uniform increase in the penetration depth with high-quality metal formation along the entire annular perimeter of the weld, elimination of local subfusion of the end of the non-consumable electrode and increase of its resistance.

Example 1. Pipes were welded with tube sheets of steel 12x18 H 10 T with asymmetry in the amplitude of the electromagnet current of opposite reversing half-periods and short-term shutdown of the electromagnet current. The size of the tubes is 25x2.0 mm. The tube grill was located in the lower position. After the installation of a welding head with a ring electrode, a shielding gas is supplied to a concentric-welded joint with an arc length of 2.2-2.4 mm - argon about 30-35 l / min, the current inverted / with a frequency of 7 Hz, the power supply current of the electromagnetic coil 3.6-3 , 7 A at one and 3.1-3.35 A at the other half-cycle with a dead time of 0.005 s, a welding arc with a current of 650670 A is excited. As a result of the interaction between the control magnetic field of the coil and the intrinsic magnetic field, the arc receives an asymmetric reversible rotation in 6 sec There is uniform penetration at a depth of about 1.8-2 mm of the ring joint and high-quality weld formation along the entire perimeter. After turning off the arc, the cooling seam is blown for 3-4 with a protective flow of argon.

PRI me R 2. Welded pipes of size 35x2.5 mm with tube sheets in the lower position of steel 12x18 N 10 T with asymmetry of the electromagnet current duration of opposite reversing half-periods and short-term shutdown of the electromagnet current. After the installation of a welding head with a ring electrode, concentrically welded the joint with an arc length of 2.2-2.4 mm, shielding gas is supplied - af5roH about 30 3S / i / min. turn on the invertable Chg for 7 Hz; the supply current of the electromagnetic coil is 3.6-3.7 A with a duration of 0.065 s and a pause of 0.005 s

on one half-cycle and, respectively, 0.060 s and 0.010 s on the other, a welding arc with a current of 670-700 A is excited. Due to the interaction of the control magnetic field of the coil and its own

the magnetic field of the arc receives an asymmetric reversible rotation and for a period of 6-6.5 s ensures uniform penetration of about 2.0-2.4 mm of the ring joint and high-quality weld formation along

the entire perimeter. After turning off the arc, the cooling seam is blown for 3-4 with a protective flow of argon.

Using the proposed method provides in comparison with the known

making high-quality compounds with a given penetration depth and increasing the resistance of the non-consumable electrode.

Claims (2)

SUMMARY OF THE INVENTION 1. A method of welding ring joints with a magnetically controlled arc, in which a ring non-consumable electrode and a reversible control magnetic field are used, characterized in that, in order to improve the quality of welded joints, mainly pipes with tube sheets, and increase the service life of the non-consumable The electrode controlling the reversible magnetic field is formed asymmetric. 2. The method according to claim 1, with the exception of the fact that before reversing the magnetic field, it is briefly turned off. i,.