SU1109273A2 - Process for two-electrode arc welding - Google Patents

Abstract

METHOD OF ARC WELDING TWO ELECTRODES according to auth. No. 502721, characterized in that, in order to increase the stability of the welding process and the quality of the formation of the seam, the distance between the straight sections of the tape is chosen to be 1.52, 0 times the diameter of the wire electrode.

Description

The invention relates to arc welding of large lengths such as pipes, tanks, etc.

According to the main auth. No. 502721, there is a known method of arc welding with two electrodes, in which a wire electrode is placed in front of a ribbon electrode, and a ribbon electrode is profiled on a wire electrode to obtain mutual contact in the arc burning zone, while the ribbon electrode is V-shaped with straight sections parallel to the axis of the weld, in the direction of welding, and the length of the straight sections is set equal to three to four diameters of the wire electrode til.

The disadvantage of this method is the violation of the stability of the process and the quality of the formation of seams depending on the distance between the straight sections of the tape.

The aim of the invention is to predict the stability of the process and the quality of the formation of welds. This goal is achieved by the fact that, according to the method of arc welding with two electrodes, the distance between the straight line sections of the tape is equal to 1.5-2 diameters of the wire electrode.

This ensures effective heat input in the front and side parts of the bath, the stability of the welding process and the high-quality formation of joints.

When the distance between the straight sections of the tape is less than 1.5 times the wire diameter, the heat input is concentrated on the axis of the panel, the arc mobility in the transverse direction and heat input on the edges of the bath are reduced, with the result that the seams are formed with undercuts. In addition, the minimum distance between the straight sections of the tape is limited by the violation of the stability of the welding process due to the interaction of arcs, the simultaneous existence of which on the edges of the tape is possible.

With an increase in the distance between the rectilinear sections of the tape with more than two wire diameters, the heat input in the fusion zone and the mobility of the arc in the transverse direction increase significantly.

However, this reduces the amount of heat spreading ahead of the blow, burning on the wire electrode, on the axis of the bath. As a result, with a significant displacement of melting isotherms to the heat source on the wire, the conditions for the existence of an active spot deteriorate, the arc is deflected backward, which leads to the formation of welds with undercuts during welding at a higher rate.

The welding method is as follows.

The tape electrode is positioned so that its straight sections in the direction of welding are located in front of the wire electrode. The current lead is made by the mouthpiece, which is made along the contour of the combined electrode. The arc is excited by the closure of one of the electrodes on the product. The tape and wire electrode is fed into the welding zone at the same speed. The tape is bent during the feeding process. The optimum distance between the rectilinear sections of the belt is provided by an appropriate gap between the bending rollers.

Welding is carried out on standard welding equipment with an attachment for feeding and profiling the electrode.

Example. Conducted unilaterally. Metal on a flux cushion with a thickness of 9 mm by two electrodes with different distances between the straight sections of the tape. The results of the conducted research on the effect of the distance between the straight sections of the tape on the stability of the welding process and the formation of seams are presented in the table.

By a known method

When the distance between the straight sections of the tape is less than 1.5 times the diameter of the wire

More than 2 wire diameters 1.5-2 wire diameters Welding is carried out at a constant mode: the current is 2500-2600 A, the voltage across the arc is 30-32V, the welding speed is 100 m / h. The process stability is estimated from current and voltage fluctuations, which are recorded by recorders. With current fluctuations above 150A and voltage over 2V, the mode is considered unstable. As a quality criterion for the formation of seams, the pruned depth of the undercut is adopted, since undercuts are the main defect that limits the welding speed. The undercut head is measured by a dial gauge with an accuracy of 0.1 m. By the State Standard for the manufacture of pipes, an allowable undercut depth of up to 0.5 mm is provided, therefore, at this depth of the undercut, the formation is of poor quality. As can be seen from the table, the stability of the welding process and the high-quality formation of the seams is ensured only when the distance between the straight sections of the tape is 1.5-2 times the diameter of the wire frame. The use of the proposed method of welding provides a comparison

Undercuts

Undercuts Undercuts There are no undercuts with known heat flow dispersion and effective heat input in both the front and side portions of the weld pool, which ensures high-quality weld formation at high speed welding; the burning of arcs on the edges of the tape in separate baths eliminates their interaction and ensures the stability of the submerged-arc welding process; The optimal distance between the straight sections of the tape reduces the pressure of the welding arc, since the arc in the area of the wire electrode fuses the adjacent sections of the tape, and when burning at the edges of the tape does not exert pressure on the bath axis. Decreasing the arc pressure allows to obtain a high-quality formation of a back roller with one-sided welding on a flux cushion. The introduction of the proposed method in welding of straight conduit pipes makes it possible to increase the welding speed and productivity of the process by 1.5–2 times due to the improvement in the quality of formation of welds.

Claims (1)

METHOD OF ARC WELDING TWO ELECTRODES by ed. No. 502721, characterized in that, in order to increase the stability of the welding process and the quality of the formation of the seam, the distance between the straight sections of the tape is chosen equal to 1.52.0 diameters of the wire electrode.