JPS60240382A - Multiple-electrode high speed submerged arc welding - Google Patents

Abstract

PURPOSE:To speed up submerged arc welding further without spoiling the quality of a weld zone by making welding giving a magnetic field of specified intensity to the lower part of the second and sulese quent electrode wires. CONSTITUTION:An arc 6a is oscillated electromagnetically in the direction perpendicular to the face of paper (perpendicular to the weld line) by making the direction of magnetic line of force that crosses the arc 6a of preceding electrode P1 perpendicularly under a succeeding electrode wire 1b, i.e. magnetic vector H, giving fixed magnetic field at all times, and changing the direction of welding current of the preceding electrode P1, i.e. the direction of current vector I, with the passage of time. At this time, the intensity of the magnetic field that makes magnetic flux density (unit: gauss) under the electrode wire 1a at least >=1/4 of welding current value (unit: ampere) is maintained. To give the magnetic field 8, there are various ways such as providing an electrode solenoid around the electrode wire 1b.

Description

[Detailed Description of the Invention] The present invention relates to a method of performing submerged arc welding at high speed using a multi-electrode wire, and in particular to a method in which the arc is electromagnetically vibrated to reduce the dispersion of the arc force applied to the molten pool. 1) Submerged arc welding can be performed at higher speeds.

When performing submerged arc welding of thin plates at high speeds, multi-electrode welding is considered to be effective. Up to now, for example, the two-electrode method has a maximum welding speed of approximately 150 cffI/m, and the three-electrode method has a maximum welding speed of approximately 2,500 m/i. It is said that it is possible to increase the speed up to There is a very strong demand from the industry to further increase welding speed and improve welding workability, and considering the technical content of the conventional high-speed submerged arc welding method, it is difficult to fully meet the above demands. I'm in a situation where I can't. That is, in the multi-electrode method, as the welding speed increases, the arc force directed toward the rear of the electrodes increases, causing the molten steel in the molten pool to flow further backward than necessary, making welding defects such as undercuts and humping more likely to occur. Therefore, in order to prevent such inconveniences from occurring, it is considered an effective means to disperse and reduce the arc force acting on the molten pool.From this perspective, conventional methods have been to mechanically vibrate the welding wire. method is implemented. However, with this method, the wire is approximately 10 to 3
Because the vibration is made at a frequency of 0 Hz, the droplets at the tip of the wire are forced to fall off and remain as bulges at the bead edge), or the wire through which the flux is passed through is filled with nitrogen, which is harmful to the molten steel. As mentioned above, there is a problem of crowding, and as a result, it is difficult to meet the demands for higher speeds.

In view of this situation, the present inventors have been conducting research to develop a means to disperse and reduce the arc force applied to the molten pool without mechanically vibrating the wire. We have completed a method that can realize even higher speeds by electromagnetically oscillating the arc using this method, and we are going to present it here.

However, in the multi-electrode high-speed submerged arc welding method of the present invention, a magnetic field is applied below at least the second electrode wire, and the magnetic flux density value (unit: nigauss) measured below the electrode wire is applied. However, the gist of this method is to perform submerged arc welding while maintaining the strength of the magnetic field so that the welding current value (unit: 2 amperes) of the adjacent preceding electrode wire is at least A or more.

The configuration and effects of the present invention will be specifically explained below with reference to the drawings. 1 and 2 are explanatory diagrams of the principle of the method of the present invention, and for ease of understanding, the case in which high-speed submerged arc welding is performed (by a two-electrode method) is shown. P1+P2
are a leading electrode and a trailing electrode, respectively, 1a+1b are electrode wires, and an arc 6a y is generated from the tip thereof.
6b is radiated in a direction opposite to the welding direction (arrow direction). Therefore, the molten steel 5 in the molten pool is blown up onto the rear solidification surface, resulting in a shortage of molten steel in the front, creating a situation where undercuts are likely to occur. This situation shows a remarkable tendency as the distance d between the wire tips becomes smaller, as the arc forces of both electrodes become easier to coordinate.

However, in the present invention, as shown in FIG.
Below b, the magnetic field 8 is applied by lines of magnetic force that perpendicularly cross the arc 6a of the preceding electrode P□.
The arc 6a receives a force in a direction perpendicular to the plane of the paper (perpendicular to the welding line) according to Fleming's left-hand rule, and is deflected in a direction across the welding line. In this case, if the direction of the magnetic lines of force, that is, the magnetic vector H, is always constant U, and the direction of the current, that is, the direction of the current vector I, is changed over time, the arc 6a will be vibrated in the direction across the welding line. In this case, since the leading electrode wire 1a is not particularly forcibly vibrated, there is no need to worry about the droplet at the tip of the wire being forcibly dropped or the flux being disturbed by the wire, and the bead edge is not forced to vibrate. It is possible to avoid appearance and structural welding defects such as nitrogen generation and nitrogen contamination into molten steel.

The case where the magnetic field of the trailing electrode acts on the arc of the leading electrode has been explained above, but it is also possible to apply the magnetic field directly below the leading electrode, that is, by applying a magnetic field that acts strongly under the leading electrode, the sandalwood It can also be thought of as directly controlling the arc. However, since the present invention is intended to be effectively applied to high-speed welding, that is, when the arc is flowing in a nearly horizontal state, simply applying a magnetic field below the trailing electrode as described above is sufficient to achieve the purpose. Moreover, it is more effective in controlling the arc of the leading electrode.

However, when applying the magnetic field 8 below the trailing electrode P2, the following considerations need to be made.

That is, the magnetic flux density value (unit: 2 gauss) measured at the tip of the electrode wire 1b is at least A greater than the welding current value (unit: 2 amperes) of the adjacent preceding electrode wire (both are anonymized and compared 9, for example, 1000 250 Gauss or more with respect to the ampere), it is possible to induce a sufficient force to drive the arc 6a under the electrode wire 1b in the direction across the welding line, and it is also expected to have the effect of eliminating inconveniences such as undercuts. become unable.

However, in order to measure the magnetic field strength mentioned above, it is necessary to specify the ``wire tip position'', but this is because the wire is usually called a ``wire extension'' and is energized along the wire direction. The position when the tip protrudes by the distance (distance between the tip and the steel plate surface) (for example,
2 points).

Further, some consideration must be given to the relationship with the electrode wire tip distance l. That is, the distance between the wire tips is 4. , t (distance between the tips of the first pole and the second pole) is short, 11-door 6a,
6b becomes more cooperative and the molten steel 1.5 is driven further backwards, which is undesirable, so the wire tip spacing is 1.
It is preferable to create a state in which the magnetic field 8 becomes stronger as the magnetic field decreases by about 1 or 20. In experiments conducted by the present inventors, the product of the wire tip spacing value (unit: l1lnl:) and the magnetic flux density value (unit: n Gauss) was set to be approximately 3000 or more (for example, if the spacing was 20 mm, it was 150 Gauss or more). Then, confirm that even if @ZS, t between the wire tips becomes shorter, the coordination of the arcs 6a and 6b will not increase (Pa).

By the way, in order to apply the magnetic field 8 below the electrode wire 1b, it is effective to form an external magnetic field around the electrode wire 1b, and the following methods can be cited as specific means for this. (1) A method of providing an electromagnetic solenoid around the electrode wire 1b. In this case, it is preferable in terms of device design to provide an electromagnetic solenoid around a general-purpose wire guide nozzle (not shown) because no extra space is required even in multi-electrode welding with narrow electrode spacing.

(2) In the configuration of (1), the electrode wire guide nozzle is made of a ferromagnetic material such as iron or an iron alloy, and an electromagnetic solenoid is provided around it. In this case, since the nozzle acts as an iron core, the concentration of magnetic flux below the electrode wire 1b is more effectively achieved. The excitation strength required for the solenoid is small. Therefore, the electromagnetic solenoid can be made smaller and can be easily applied to multi-electrode welding with narrower electrode spacing.

(3) A method of constructing the electrode wire guide nozzle with a permanent magnet having an appropriate magnetic force.

According to this method, if the welding conditions are almost fixed,
In particular, without using an electromagnetic coil, it is possible to avoid applying a necessary magnetic field to the arc, and it is possible to omit an excitation power supply device and a switch-on operation.

(4) A method in which the electrode wire guide nozzle is a permanent magnet and an electromagnetic solenoid is further provided around it.

This method has the advantage that the excitation ability of the electromagnetic solenoid can be lowered than in the case of (1) or (2) to obtain the same magnetic force, and that the electromagnetic solenoid can be further miniaturized.

In order to efficiently guide the magnetism excited by any of the methods (1) to (4) above to the tip of the electrode wire 1b, the electromagnetic solenoid, the wire guide nozzle serving as the magnetic core, the permanent magnet, etc. should be placed as close to the electrode wire 1b as possible. Needless to say, it is desirable to extend it to the vicinity of the tip. However, an extremely high temperature arc is generated from the tip of the electrode wire 1b.
Furthermore, since high-temperature radiant heat and gas are released from the molten pool, there is a limit to how close it can be to the tip of the electrode wire 1b.

Therefore, in practice, it is convenient to use iron or an iron base metal as the current-carrying tip 2b (usually made of copper alloy and disposable) attached to the tip of the wire guide nozzle. In this case, the current-carrying tip 2b was subjected to copper plating, copper dipping treatment, energized alloy thermal spraying treatment, etc. in order to conduct electricity to the wire and prevent iron spatter from adhering. It is also possible to form a composite structure covered with something.

According to the principle of the present invention, the magnetic field at the tip of the electrode wire 1b and its vicinity does not necessarily have to be in one direction.
When using an alternating magnetic field, the intended purpose can be fully achieved by using an alternating current electromagnet and a direct current arc. However, in this case.

The above magnetic field forming method (4) cannot be adopted.

Further, when a commercial frequency current of 50 to 60 Hz is used as the arc current, an alternating current with a frequency lower than 50 Hz can be used as the exciting current instead of a direct current.

Next, examples of the present invention will be shown.

(Example 1) As shown in FIG.
and 20° inclined 4.0mm diameter mild steel wire and S i O,
The groove shape shown in FIG. 4 was formed by using MnO-based flux in one pass by two-electrode submerged arc welding. At that time, welding was performed under the following conditions using the electromagnetic solenoid 10 as the second electrode 1b, and the relationship between the magnetic field strength at the tip of the wire and the state of the bead was investigated. However, a 5 oz alternating current was used for the welding current, and a direct current was used for the excitation current. The energization results are shown in Table 1. The energizing tips 2a l 2b were made of prepared alloy and had a length of 3 om, and the distance between the first electrode 1a and the second electrode 1b on the steel plate surface! 89. was set to 15 mm.

[Welding conditions]

First electrode: 900 x 36 V Second electrode: 700 x 42 V Welding speed: 1700 m/*i Table 1 (Example 2) The first electrode was tilted at 2 degrees, the second electrode was at 13 degrees, and the third electrode was tilted at 26 degrees as in Example 1. 4.0 mmφ mild steel wire and S
Double-sided one-pass welding of high-strength steel having the groove shape shown in FIG. 4 was carried out using a three-electrode submerged arc welding method using an O, -MnO-CaO-CaF1 flux. At that time, welding was performed under the following conditions using a copper or iron wire guide nozzle equipped with an electromagnetic solenoid as the second or third electrode, and the relationship between the magnetic field strength at the wire tip and the bead condition was investigated. Ta. The welding current is 50Hz AC, and the exciting current is DC and 10Hz.

A 30 Hz alternating current was used. The energization results are shown in Table 2, and the energizing tips are all made of prepared alloy and have a length of 3.
0 nm is used, and the distance between the first electrode and the second electrode is 112. The distance between the second and third electrodes is 20111ms l! , 8 was set to 25 mm.

[Welding conditions]

First electrode: 1200AX34V Second electrode: 900AX42V Third electrode: 700AX44V Welding speed: 330cm/m (Example 3) The third electrode An electromagnetic solenoid was attached to the 3-electrode submerged arc welding. In this case, the core of the electromagnetic solenoid was made of mild steel and also served as a wire guide nozzle. Further, as the current-carrying tip of the third electrode, one having a composite structure of a mild steel part 27 and a chrome steel part 28 as shown in FIG. 5(b) is used;
0 mmφ mild steel wire and Si (%-A1203
CaOT ((%-CaFz-based flux was used. A 50 Hz alternating current was used for the welding current and a direct current was used for the excitation current. A 9-thickness mild steel plate with 90° grooves of 3 mm depth on both sides was heated under the following conditions. The presence or absence of undercut was examined by welding under the following conditions.However, the inclination directions of the first, second, and third electrodes I were 2°, 12°, and 24°, which were the same as in Example 1. The distance between the current-carrying tip and the steel plate surface is 1, and the second electrode is 3.
0 mm, and the third electrode is 25 mm. The results are shown in Table 3.

[Welding conditions]

Indicates that welding conditions A and B are applied.

As is clear from Tables 1 to 3 above, in any of Examples 1 to 3, the magnetic flux density (in Gauss) below the second and subsequent electrodes is the welding current value of the adjacent preceding electrode ( If the value is at least A (unit: ampere), no undercut will occur at all.

(Example 4) A copper/copper composite structure having a steel part was used as the current-carrying chip, and its wire excitation ability and heat resistance were examined. However, the current-carrying chips shown in FIGS. 5(a) to 5(c) were prepared. In the figure, 21, 25, and 29 are wire passing holes, 22, 26, and 30 are connection screw parts, 23, 27, and 31 are steel parts, 24, 28 are steel parts, and 32 is a copper plated part. First, in order to confirm the improvement of excitation ability, that is, magnetic field strength, Example 1
In experiment number 1-3, the energized chip was
As a result of replacing it with the one in c), it was found that the wire tip was significantly improved to 1300°, 1700 Gauss, and 1500 Gauss, respectively.

Next, according to the conditions of Example 10, the current-carrying tips of (a) to (C) above were attached to the second electrode so that the tips of these tips were 30 mm from the steel plate surface, and welded continuously for 100 m. As a result,
The current conduction characteristics, degree of erosion, etc. were not inferior to those of ordinary copper alloy films.

The present invention is configured as described above, but the key point is to electromagnetically vibrate the arc using magnetic force of a predetermined strength without mechanically vibrating the wire, thereby reducing the dispersion of the arc force applied to the molten pool. As a result, submerged arc welding can now be performed at higher speeds without any loss in the quality of the weld.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining the principle of the method of the present invention, and Figures 3-
FIG. 5 is an explanatory diagram of the conditions of the embodiment. Pl... Leading electrode P2... Trailing electrode 1a+1b・
... Electrode wire 2a * 2b ... Current-carrying tip 4.
...Steel plate 5... Molten steel 6a, 6b... Arc 7... Weld metal 8...
・Magnetic field H...Magnetic vector ■...Current vector Figure 1 9Fi' 2nd diagram q

Claims (1)

[Claims] (1) The magnetic flux density value (unit: nigauss) measured below the electrode wire and the welding current value (unit: 2 amperes) at the adjacent preceding electrode, each anonymized, satisfy the following conditions. A multi-electrode high-speed submerged arc welding method characterized by applying a magnetic field below the electrode wire.