SU1366334A1 - Method of welding with arc rotating in magnetic field - Google Patents

Abstract

The invention relates to arc welding, in particular to welding methods. heating by an arc burning between the ends of the parts to be welded, and subsequent draft. It can be used mainly in the manufacture of welded thick-walled pipes. The aim of the invention is to improve the quality of welded joints of thick-walled pipes and expand the range of weldable thicknesses. The welding method consists in obtaining a uniform gap between the welded ends of the parts during the preheating process. This is achieved by a brief increase in the welding current at the moment of arc arc closing with liquid metal. In this case, a layer of liquid metal is removed from the plane of the junction by the action of electrodynamic forces, which prevents the heating process from proceeding further. In order to obtain uniform heating throughout the welded section, pipes with an X-shaped groove of their ends are prepared, the edges of which are blunt-edged. The magnetic fields in the gap, which are closed through the protrusions of the tubes, form sufficiently strong magnetic fluxes in the zone of arc rotation and contribute to the stabilization of the arc rotation rate. 1 hp f-ly. 2 Il. (L with O) about with with 4511

Description

The invention relates to arc welding, in particular to methods of welding with heating arc, burning between the ends of the parts to be welded, and subsequent downfall, and can be used mainly in the manufacture of thick-walled welded pipes.

The aim of the invention is to improve the quality of the welded joints of thick-walled pipes and to expand the range of weldable thicknesses.

FIG. Figure 1 shows a sequence diagram of the variation of the welding current, arc voltage, and movement in time of one of the parts being welded; in fig. 2 is a schematic of an apparatus for carrying out the method. .

The welding method consists in obtaining a uniform gap between the welded ends of the parts during the preheating process. This is achieved by a brief increase in the arc current at the time of closing the arc gap with liquid metal. A decrease in the gap in the junction at its individual sections is recorded by a drop in voltage on the arc (Fig. 1), a short-term increase in the arc current under the action of electrodynamic forces promotes the removal of a layer of liquid metal that prevents further uniform heating of the junction.

Upon reaching the necessary heating zone at the final stage of welding, a sharp, short-term increase in the welding current and sludge of the welded pipes is made.

To obtain uniform heating throughout the welded section, pipes with an X-shaped groove of their ends are prepared. The size of the bluntness of the end (cutting) is determined by the size of the autonomous spots of the arc. Exceeding the size of the bluntness of the edge cutting leads to a shift of the active spots of the arc to the outer surface of the joint and its uneven heating according to the table. Rotation of the arc according to the limited area of the active spots in the arc of the square of the end of the tubes ensures stabilization of its burning and uniform heating of the outer and inner layers of the tubes. The magnetic fields in the cutting gap, closing through the protrusions of the tubes, form sufficiently strong (concentrated) magnetic fluxes in the zone of rotation of the arc and help stabilize its rotational speed. Speed

r

about 5 about

d

0

rotation of the arc over the entire heating cycle is almost constant.

Weldable parts 1 and 2 with clamps 3 and 4 set coaxially with a gap of 3 mm between the ends (Fig. 2). Parts 1 and 2, which are sections of steel pipes with a diameter of 80 mm and a thickness of 13 mm, are made with a bevel of the pipes in such a way that the bluntness width is 3.5 mm. Clips 3 and 4 are connected to the corresponding poles of power supply 5, for example VDU-1201, which can switch from one current value to another using contacts 6 of the relay 6. Electromagnetic coils 7 and 8 are placed in close proximity to the welded joint to provide arc movement along the closed contour of the ends of the parts. They are connected to power source 9. After excitation of the arc in the gap of the arc pipe, the initial heating current is set to 300 A. rotational arc associated with a change in the gap.

The change in arc voltage, resulting from the appearance of the fused sections of the end surface, is detected by the sensor-10, issuing a command to the relay 6, which switches the source to the set increased value of the welding current. There is an emission from the welded surfaces of the liquid metal layer, which prevents the further conduct of the process. When the arc voltage is restored to the specified value, the sensor 10 switches off the relay b, the source 5 switches to a lower (heating) welding current value.

For such a cycle, parts were heated for 35 s. The source is switched 4 times during this time. During this period of heating, the welded pipes are heated to the required depth with a uniform zone. At the end of the heating, the current value is set at 1300 A, the melting time is 0.1-0.2 s. After pulsed fusion, a precipitate is produced by the mechanism of 11 parts in the short-term short-circuit mode. The slump velocity is at least 200 mm / s. Simultaneously with the welding source, the power supply of the magnetic coils is disconnected. Mechanical testing of a batch of welded joints made by the proposed method showed the absence of defects in the joint and the equal strength of the pipe base metal.

Compared with the base object, for which the prototype is adopted, the proposed welding method makes it possible to reduce the scrap of welded pipes by up to 1-2% and expand the range of weldable thicknesses.

Claims (1)

1. The method of welding by an arc rotating in a magnetic field, in which the preheating of the edges of the connected parts is first carried out across the thickness of the joint, and then heated 1366334 C g welded edges with welding current followed by draft, differing in that, in order to improve the quality of welded joints of thick-walled pipes and expand the range of weldable thicknesses, at the moments of short-term arc arc liquid metal heating, the heating current increases and the edges of the parts to be joined are made with X -shaped blunting. 2, the method according to claim 1, about tl and h.a y - yi and so that the width of the blunting is chosen equal to the size of the active, arc spot. I g I l tc Au Sriе.1