JPH0333436B2 - - Google Patents

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, submerged arc welding can be performed at higher speed by electromagnetically vibrating the arc to reduce the dispersion of the arc force applied to the molten pool. It was made in a similar manner. Multi-electrode welding is considered effective when submerged arc welding of thin plates is performed at high speed.
It is said that the three-electrode method can increase the speed up to about 250 cm/min. However, there is a very strong demand from industry to further increase welding speed and improve welding workability, and the conventional high-speed submerged arc welding method is unable to adequately meet the above demands due to its technical content. It is in. That is, in the multi-electrode method, as welding speed increases, the arc force directed toward the rear of the electrodes increases, causing the essential steel in the molten pool to flow further rearward 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. But this method runs the wire at about 10-30Hz
Since the vibration is performed at a frequency of As mentioned above, for this reason, it is not possible to sufficiently meet the demand for higher speeds. In view of this situation, the present inventors have conducted 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 achieve even higher speeds by electromagnetically oscillating the arc using this method. However, in the multi-electrode high-speed submerged arc welding method of the present invention, an alternating magnetic field is applied below at least the second and subsequent electrode wires to direct the arcs of adjacent and preceding electrodes in a horizontal direction orthogonal to the welding line. Magnetic flux density value (unit: Gauss) measured below the electrode wire while welding while vibrating
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: ampere) of the adjacent preceding electrode wire is at least 1/4 or more. The configuration and effects of the present invention will be specifically explained below with reference to the drawings. FIGS. 1 and 2 are explanatory diagrams of the principle of the method of the present invention, and for ease of understanding, show a case in which high-speed submerged arc welding is performed by a two-electrode method. P ₁ and P ₂ are leading electrodes and trailing electrodes, respectively; 1a and 1b are electrode wires, respectively;
Arcs 6a and 6b generated from their tips are radiated in a direction opposite to the welding direction (direction of arrow A). 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 smaller the distance d between the wire tips, the easier it is for the arc forces of both electrodes to coordinate. However, in the present invention, as shown in FIG. 2, a magnetic field 8 is applied below the trailing electrode wire 1b in which lines of magnetic force act so as to perpendicularly cross the arc 6a of the leading electrode _P1 , so that the arc 6a is located on Fleming's left hand. According to the law, a force is applied in a direction perpendicular to the plane of the paper (perpendicular to the weld line), and it is deflected in a direction that crosses the weld line. In this case, if the direction of the magnetic lines of force, that is, the magnetic vector H, is always kept constant, and the direction of the current, that is, the direction of the current vector I, is changed over time, then
The arc 6a will be vibrated in a direction across the weld line. In this case, since the leading electrode wire 1a is not particularly forcibly vibrated, there is no need to worry about the droplets at the tip of the wire being forcibly shaken off or the flux being disturbed by the wire, and the occurrence of burrs at the bead edge. It is possible to avoid appearance and structural welding defects caused by nitrogen intrusion into molten steel. Above, we have explained the case where the magnetic field of the trailing electrode acts on the arc of the leading electrode, but by applying a magnetic field directly below the leading electrode, that is, by a magnetic field that acts strongly under the leading electrode, the self-polar Of course, it is also conceivable to control the arc directly. 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,
As mentioned above, simply applying a magnetic field below the trailing electrode is sufficient to achieve the purpose, and 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 must be made. That is, the magnetic flux density value (unit: Gauss) measured at the tip of the electrode wire 1b is at least 1/4 or more of the welding current value (unit: ampere) of the adjacent and preceding electrode wire 1a (both are anonymized and compared, for example, 1000 arc 6 under electrode wire 1b).
It is not possible to induce a sufficient force to drive a in the direction across the welding line, and furthermore, it cannot be expected to be effective in eliminating inconveniences such as undercuts. However, in order to measure the above magnetic field strength, it is necessary to specify the ``wire tip position,'' which is because the length of the wire is usually called the ``wire extension'' (the current tip along the wire direction). (distance from the steel plate surface) (for example, points X ₁ and X ₂ in Figure 1). Further, some consideration must be given to the relationship with the electrode wire tip distance l. In other words, the shorter the distance between the wire tips l ₁ and ₂ (the distance between the tips of the first and second poles), the more cooperative the arcs 6a and 6b become, and the more the molten steel 5 is driven backwards, which is undesirable. , it is preferable to create a state in which the magnetic field 8 becomes stronger as the distance between the wire tips l ₁ and ₂ decreases. In experiments conducted by the inventors, the product of the wire tip spacing value (unit: mm) and the magnetic flux density value (unit: Gauss) is approximately 3000 or more (for example, if the spacing is 20 mm, it is 150 Gauss or more). It has been confirmed that if the distance between the wire tips l ₁ and ₂ becomes shorter, the coordination of the arcs 6a and 6b will not increase. 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 special 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 iron alloy, and an electromagnetic solenoid is provided around it. In this case, since the nozzle acts as an iron core, the magnetic flux is more effectively concentrated below the electrode wire 1b. 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 in which the electrode wire guide nozzle is constructed of a permanent magnet having an appropriate magnetic force. According to this method, when the welding conditions are almost strict, it is possible to
A necessary magnetic field can be applied to the arc, and the need for an excitation power supply or switch-on operation can be omitted. (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 capacity of the electromagnetic solenoid can be lowered than in the above cases (1) or (2) to obtain the same magnetic force, and 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, place the electromagnetic solenoid, wire guide nozzle serving as a magnetic core, permanent magnet, etc. as close to the tip of the electrode wire 1b as possible. It goes without saying that it is desirable to extend the However, from the tip of the electrode wire 1b,
Since an ultra-high temperature arc is generated and high-temperature radiant heat and gas are emitted from the molten pool, there is a limit to how close it can get to the tip of the electrode wire 1b. Therefore, when implementing it, a current-carrying chip 2b (usually made of copper alloy) attached to the tip of the wire guide nozzle,
It is convenient to use ones made of iron or iron alloys (disposable). In this case, in order to conduct electricity to the wire and prevent welding of iron spatters, the current-carrying chip 2b may be subjected to copper plating, copper dipping treatment, heat-resistant alloy spraying, etc., or the current-carrying chip 2b may be made of iron or iron alloy. It is also possible to form a composite structure in which the outer periphery of the tip is covered with something made of steel or a steel alloy. 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 unidirectional; when using an alternating magnetic field, the DC arc of an AC electromagnet can be used to achieve the desired purpose. can be achieved. However, in this case,
The above magnetic field forming method (4) cannot be adopted. Further, when using a commercial frequency current of 50 to 60 Hz as the arc current, for example, 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. 3, the first electrode (leading electrode) and the second
The electrode (trailing electrode) was tilted at 4° and 20° in the direction opposite to the welding direction with respect to the vertical line, respectively.
One-pass welding on both sides of a mild steel plate 4 having the groove shape shown in FIG. 4 was performed by two-electrode submerged arc welding using SiO ₂ --MnO flux. At that time, the electromagnetic solenoid 1 is connected to the second electrode 1b.
Welding was performed under the following conditions using 0.0 to investigate the relationship between the magnetic field strength at the tip of the wire and the state of the bead. However, 50Hz alternating current was used for the welding current, and direct current was used for the excitation current. The results are shown in Table 1. The current-carrying chips 2a and 2b were made of copper alloy and had a length of 30 mm, and the distance between the first electrode 1a and the second electrode 1b on the surface of the steel plate was l ₁ , ₂
was set to 15mm. [Welding conditions] 1st electrode: 900×36V 2nd electrode: 700×42V Welding speed: 170cm/min

[Welding conditions]

1st electrode: 1200A×34V 2nd electrode: 900A×42V 3rd electrode: 700A×44V Welding speed: 330cm/min

[Table] Example 3 Condition of undercut occurrence and electrode wire spacing,
In order to investigate the relationship between welding current and magnetic flux density, three-electrode submerged arc welding was performed by attaching an electromagnetic solenoid to the third electrode. 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 chip of the third electrode, a mild steel part 27 and a chromium copper part 28 as shown in FIG. 5b are used.
In addition to using a composite structure of 4.0mmφ
mild steel wire and SiO ₂ −Al ₂ O ₃ −CaO−TiO ₂
−CaF ₂ -based flux was used. The welding current uses 50Hz alternating current and the exciting current uses direct current.
A 9 mm thick mild steel plate with 3 mm deep 90° grooves on both sides was welded under the following conditions and the occurrence of undercuts was examined. However, the inclinations of the first, second, and third electrodes are 2°, 12°, and 24°; the inclination directions are the same as in Example 1, and the distance between the current-carrying chip and the steel plate surface is such that the first and second electrodes are 30mm, and the third electrode is 25mm. The results are shown in Table 3. [Welding conditions] A 1st electrode: 900A x 35V 2nd electrode: 600A x 40V 3rd electrode: 500A x 45V Welding speed: 300cm/min B 1st electrode: 1000A x 35V 2nd electrode: 800A x 40V 3rd electrode :650A×45V Welding speed: 360cm/min

[Table] Shows that.
As is clear from Tables 1 to 3 above, in any of Examples 1 to 3, the magnetic flux density (unit: Gauss) below the second and subsequent electrodes is the welding current value of the adjacent preceding electrode. (Unit: ampere) If it is at least 1/4 or more, no undercut will occur at all. Example 4 A copper/steel composite structure having a steel part was used as an energizing chip, and its wire excitation ability and heat resistance were investigated. However, the current-carrying chips shown in FIGS. 5a to 5c were prepared. 21, 25, 29 in the figure
22, 26, 30 are connecting screw portions, 23, 27, 31 are steel portions, 24, 28 are copper portions, and 32 is a copper plated portion. First, in order to confirm the improvement in the excitation ability, that is, the magnetic field strength, in Experiment No. 1-3 of Example 1, the current-carrying chips were replaced with the ones a to c above. A significant improvement was observed. Next, under the conditions of Example 1, the current-carrying chips a to c above were attached to the second electrode so that the tips of these chips were 30 mm from the steel plate surface, and welded continuously for 100 m. However, it was not inferior to those made of ordinary copper alloy. 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 even higher speeds without any loss in quality of the welded part.

[Brief explanation of drawings]

1 and 2 are diagrams explaining the principle of the method of the present invention,
FIGS. 3 to 5 are explanatory diagrams of the conditions of the embodiment. P ₁ ... Leading electrode, P ₂ ... Trailing electrode, 1a, 1
b... Electrode wire, 2a, 2b... Current-carrying chip,
4... Steel plate, 5... Molten steel, 6a, 6b... Arc, 7... Welding metal, 8... Magnetic field, H... Magnetic vector, I... Current vector.

Claims (1)

[Claims] 1. The magnetic flux density value (unit: Gauss) measured below the electrode wire and the welding current value (unit: ampere) at the adjacent preceding electrode are anonymized so that the following conditions are satisfied. A multi-electrode high-speed submerged arc welding method, characterized in that an alternating magnetic field is applied below the electrode wires of at least the second and subsequent electrodes, and welding is performed while the arcs of adjacent and preceding electrodes are vibrated in a horizontal direction perpendicular to the welding line. . Welding current value/magnetic flux density value≦4