JP5343771B2 - Tandem rotating submerged arc welding method - Google Patents

Description

  The present invention relates to a tandem rotating submerged arc welding method, and more particularly to a tandem rotating submerged arc welding method capable of controlling a weld bead shape and penetration in tandem submerged arc welding.

As illustrated in FIG. 1, submerged arc welding is known in which an arc is generated between a welding wire 22 and a base material 10 under a granular flux 20 and welding is performed using high heat generated thereby. In this submerged arc welding, a granular flux 20 is deposited in advance on the base material 10, and the tip of the welding wire 22 is inserted into the flux 20 for welding. The arc is covered with the flux 20 and is not visible from the outside. The flux 20 contributes to the blocking of the atmosphere and the refining action of the weld metal, and contributes to the formation of the slag 26 and the weld bead 28. In the figure, 12 is a backing material, and 24 is an electrode.

  This submerged arc welding is widely used for shipbuilding, bridge welding of bridges, BOX columns and pressure vessels of high-rise buildings. Since it is possible to employ a large current and multiple electrodes, it has high efficiency (high welding speed) and deep penetration, but the welding posture is downward as illustrated in FIG. 2 or illustrated in FIG. However, most of the construction is downward. 2 and 3, reference numeral 14 denotes a standing plate (for example, a flange of an H-shaped steel material), and 16 denotes a lower plate (also a web). In addition, most of the rod moving methods are straight and there are cases where they are swung.

  In the downward posture illustrated in FIG. 2, thick wire and high current welding are applied and high efficiency and high quality (deep penetration, good bead appearance), but the workpiece posture is changed so that the welding posture is downward. In the case of H-shaped steel, only one joint on one side of the web can be constructed.

  On the other hand, in the horizontal posture illustrated in FIG. 3, two joints on both sides of the web can be simultaneously applied even in the case of an H-shaped steel material, but bead sagging occurs due to the action of gravity, and the horizontal fillet as illustrated in FIG. In welding, upper leg length shortage or undercut is likely to occur on the standing plate 14 side. Furthermore, on the long leg side where the leg length is long, the drooping appearance is poor, the shape of the bead toe portion is bad, and it is very difficult to put a large leg long fillet weld having a length of 10 mm or more in a horizontal posture to practical use.

  Further, tandem submerged arc welding in a horizontal posture has been proposed in Patent Document 1 and the like for the purpose of reducing the number of times of reversal of the target workpiece and shortening the construction time (for example, simultaneous construction on both sides of build edge BH neck welding). However, in the conventional horizontal tandem submerged arc welding, the appropriate welding condition range (especially the target position) is very narrow, and usually adjustment of welding conditions (current, voltage, speed, electrode arrangement (angle), etc.) and welding We strive to meet the required welding quality by selecting the wire and flux, but are inferior in high-speed weldability, large leg length, and undercut resistance, especially with conventional mechanical copying and pushing-type potentiometers. In the copying control, there is a high possibility that an upper leg length shortage or a vertical undercut will occur in a long workpiece due to a delicate aim.

  Therefore, conventionally, downward tandem submerged arc welding is generally used because of the above-mentioned tolerance of conditions and workability.

  On the other hand, in gas shielded arc welding without using flux, as proposed by the applicant in Patent Document 2, as shown in FIG. 4, rotating arc fillet welding in which the tip of the welding wire 22 is rotated has been put into practical use. . In the figure, 23 is an arc. Patent Document 2 also suggests that this rotating arc fillet welding is used not only for gas shielded arc welding but also for submerged arc welding.

  Patent Document 3 describes tandem rotating gas shielded arc welding.

JP-A 63-16870 JP 61-249667 A JP 2000-667 A

  However, when the inventor tried to apply the technique of Patent Document 2 to submerged arc welding as it was, it turned out that it did not work. That is, in the submerged arc welding, the bead bias is reversed from that of the gas shielded arc welding, and the bead appearance is poor at the rotational frequency of 50 Hz which is general in the gas shielded arc welding. .

  Most of arc welding is applied to automatic carts (equipment), but in the case of submerged arc welding, the arc generation point is covered with flux and cannot be confirmed visually. Position adjustment is very difficult. The conventional technologies include (1) mechanical carriage copying with a guide roller, etc. that keeps the positional relationship between the member and the electrode along with the guide roller in contact with the member to be welded, and (2) the target position of the carriage rail. Or (3) a method of controlling the position by pressing a potentiometer (position sensor) with a roller at the tip against the member to be welded. It was.

  That is, position control using mechanical copying or a potentiometer can only control the positional relationship between the electrode and the portion where the guide roller or sensor is in contact, and accurately copies the crossing portion of the member, the groove root portion, and the like. It is not possible. Also, it cannot cope with thermal deformation during welding. In particular, in the case of tandem welding, there is a problem that it is impossible to set a target position with respect to the preceding electrode.

  The present invention has been made to solve the above-mentioned conventional problems. When the welding wire rotating state of gas shielded arc welding is applied as it is, the welding wire rotating state of tandem submerged arc welding, which does not work well, is appropriately used. It is an object to improve high-speed weldability, large leg length, and undercut resistance.

The present invention uses a leading electrode and a trailing electrode to generate an arc between the welding wire and the base metal under a granular flux, and welds the target position when performing tandem submerged arc welding using the high heat generated thereby. the welding wire tip of the leading electrode which is shifted to one side than the line, Rutotomoni rotated in the direction of the welding wire front approaches the weld line, the distal end of the welding wire of the row electrodes after shifted to the side opposite to the leading electrode aim position, The problem is solved by rotating the front side of the welding wire in a direction approaching the welding line.

Here, during horizontal fillet welding, the aiming position of the leading electrode welding wire tip is shifted to the lower plate side from the welding line, and the aiming position of the trailing electrode welding wire tip is shifted from the welding line to the vertical plate side. Can do.
The present invention also uses a leading electrode and a trailing electrode to generate an arc between the welding wire and the base metal under a granular flux, and performs horizontal fillet welding by tandem submerged arc welding using the high heat generated thereby. At this time, the tip of the welding wire of the following electrode is always welded without shifting the tip of the welding wire of the leading electrode shifted from the welding line to the lower plate side than the welding line. The problem is solved by rotating the front side of the wire in a direction approaching the weld line.

Here, at the time of the tandem rotation submerged arc welding, Cf is the center in a predetermined rotation condition range in which there is regularity between the front center point Cf in the welding progress direction in the arc rotation circle and the arc voltage waveform or arc current waveform. Tracking control by an arc sensor is possible by controlling the target position so that the difference between the integrated values of arc voltage values or arc current values in a predetermined symmetrical integration region (for example, 0 ° to 90 °) is constant. It can be. In the case of submerged arc welding, the regularity is established only in a predetermined rotation condition range of, for example, a rotation frequency of 3 Hz to 30 Hz, unlike gas shielded arc welding in which the regularity is always established regardless of the rotation conditions. Also, there is a limit of the rotation diameter, and in addition, it can be defined by the rotation pitch.

  According to the present invention, even in tandem submerged arc welding, the bead shape and penetration can be controlled by rotating the tip of the welding wire. Therefore, high-speed weldability, large leg length, and undercut resistance can be improved. Furthermore, the condition tolerance of the target position can be improved, and high quality and high stability in actual construction can be realized.

The perspective view which shows the principle of the submerged arc welding which this invention makes object Sectional view showing an example of downward welding Cross section showing an example of horizontal fillet welding Perspective view showing the state of rotating arc fillet welding in gas shielded arc welding The figure which shows a part of experiment result which investigated the influence of the rotation direction and rotation frequency for demonstrating the principle of this invention. The perspective view which shows the outline | summary of 1st Embodiment of this invention. (A) Front view and (B) Plan view showing the arrangement of the leading electrode and the trailing electrode. Figure showing the welding cross section in comparison with the conventional method Figure showing the upper leg length and welding speed in comparison with the conventional method The perspective view which shows 2nd Embodiment of this invention. Diagram showing definition of arc rotation position Diagram showing the relationship between the target position of the welding torch and the output of the arc sensor The figure which shows the example of the arc welding line scanning control circuit which can be used by the said embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  For horizontal fillet submerged arc welding with a torch angle of 50 ° between the left standing plate 14 and the right lower plate 16 as shown in FIG. 3, the inventor rotates the tip of a welding wire 22 having a diameter of 1.6 mm. When the experiment was carried out with a diameter of 3 mm, when the tip of the welding wire 22 was rotated clockwise (referred to as forward rotation) so as to scoop up the weld bead 28, the welding bead 28 was reversed. When the tip of the welding wire 22 was rotated counterclockwise CCW (referred to as reverse rotation) so as to scrape, the results shown in Table 2 were obtained.

  FIG. 5 shows an example when the rotation frequency is 30 Hz and 50 Hz.

  From Table 1 and Table 2, when the welding wire is rotated forward (Table 1), the leg length (lower leg length) on the lower plate side becomes larger and rotates counterclockwise, contrary to the tendency at the time of gas shield arc welding. When (reversed) (Table 2), the leg length (upper leg length) on the standing plate side is increased contrary to the tendency at the time of gas shield arc welding, and the bead deflection is increased as the rotational frequency is increased. However, when the rotational frequency was increased to 50 Hz, which is common in rotating gas shield arc welding, it became clear that there was a limit due to bead defects such as humping beads in both forward and reverse rotation.

  The present invention has been made on the basis of the above knowledge. In the first embodiment, as shown in FIG. 6, when performing horizontal fillet tandem submerged arc welding, the welding wire 22A of the leading electrode 24A is not rotated. A straight rod is used, and only the tip of the welding wire 22B of the trailing electrode 24B has a rotational frequency of 3 to 15 Hz, which is a relatively low speed compared to gas shield arc welding in which a rotational frequency of 50 Hz is general, and the front side of the welding wire 22B. The front side of FIG. 6 is rotated down in the counterclockwise direction CCW approaching the weld line WL.

  An example of the arrangement of the nozzle rotation shaft 25A of the preceding electrode 24A and the nozzle rotation shaft 25B of the subsequent electrode 24B is shown in FIG.

  All welding conditions other than rotation are the same (welding speed is 84 cpm), and the tip of the welding wire 22B of the trailing electrode 24B is rotated under appropriate conditions (in the embodiment, the rotation diameter is 3 mm, the rotation frequency is 7 Hz, and the rotation pitch is 2 mm). Thus, as shown in FIG. 8 (A), as shown in FIG. 8 (B), as shown in FIG. 8 (B), as shown in FIG. The leg length of the upper leg could be increased to 9 mm. Further, when the welding speed was reduced to about 40 cpm, as shown in FIG. 8C, the upper leg leg length could be increased to 13.5 mm.

  An example of the relationship between the upper leg leg length and the welding speed in this embodiment is shown by a solid line A in FIG. In the same way as shown by the solid line B, when compared to the conventional example using a large-diameter wire that is non-rotating both front and rear and capable of high current, when using a thin-diameter wire by rotating only the welding wire of the trailing electrode, the standard leg length It was confirmed that the welding speed in the case of (8 mm) was improved by 20% from 70 cpm to 84 cpm, and the upper leg leg length in the case of low speed welding (50 cpm) was improved by 19% from 11.8 mm to 14.0 mm.

  Since it is relatively easy to ensure the shape and leg length of the lower leg, in this embodiment, the welding wire 22A of the leading electrode 24A is a non-rotating straight conveying rod, so that the molten pool between the electrodes is stabilized. Can be controlled easily.

  As in the second embodiment shown in FIG. 10, the tip of the welding wire 22A of the leading electrode 24A is scraped up in the clockwise direction CW where the front side (front side in FIG. 6) of the welding wire 22A approaches the welding line WL. The tip of the welding wire 22B of the trailing electrode 24B can also be rotated down in the counterclockwise direction CCW as in the first embodiment.

  According to this embodiment, it is necessary to consider the stability of the molten pool between the electrodes, but the shape and leg length of the lower leg can also be controlled.

  The welding line scanning control in the embodiment can be performed as follows, for example.

  FIG. 11 shows an example of the definition of the arc rotation position in rotary arc welding. Here, in the arc of rotation of the arc, the front center point in the welding progress direction is Cf, the rear center point is Cr, the standing plate 14 side is the R side, and the lower plate 16 side is the L side.

Also, taking the target position x _p of the welding torch on an axis 21 perpendicular to the nozzle rotating shaft 25, the x _p when the aiming position of the welding torch is consistent with the weld line WL is set to x _p = 0, x _p With respect to = 0, the standing plate 14 side (R side when indicated by the arc rotation position in FIG. 11) is defined as positive, and the lower plate 16 side (L side when indicated by the arc rotation position in FIG. 11) is defined as negative.

  In the arc sensor welding line tracking control method, as shown in FIG. 11, the left and right (L, R) phase angle θ is the same (for example, 0 ° <θ <90 °) around the Cf point for each rotation of the arc. For example, the arc voltage value is integrated, and the difference (SL−SR) between the integrated value SL of the arc voltage value on the lower plate (L) side and the integrated value SR of the arc voltage value on the standing plate (R) side is calculated. It is taken out as an output, and the target position of the welding torch is automatically corrected according to the value and sign of (SL-SR).

That is, the output (SL-SR) of the arc sensor is SL-SR = 0 when the target position of the welding torch coincides with the weld line (x _p = 0) as shown in FIG. Therefore, welding is advanced as it is. Also, as shown in FIG. 12B, when the target position of the welding torch is shifted to the lower plate 16 side (x _p <0), the arc length is higher on the vertical plate 14 side than on the lower plate 16 side. Since it becomes longer and SL-SR <0, a command is given to correct the target position of the welding torch toward the upright plate 14 side. Also, as shown in FIG. 12C, when the target position of the welding torch is shifted to the standing plate 14 side (x _p > 0), the arc length is lower on the lower plate 16 side than on the standing plate 14 side. Since it becomes longer and SL-SR> 0, a command is given to correct the target position of the welding torch toward the lower plate 16 side.

As apparent from FIG. 11, since the sign of the arc sensor output (SR-SL) is reversed from positive to negative with x _p = 0 and SL-SR = 0 as the center, the target position of the welding torch is on the vertical plate 14 side or When it is shifted to the lower plate 16 side, the target position of the welding torch may be corrected in the direction in which SL-SR = 0 is always established. Note that if the target value of (SL-SR) is other than 0, the target position can be offset from the weld line.

  An example of the arc sensor welding line copying control device used in the embodiment is shown in the block circuit diagram of FIG.

  In the figure, 31 is an arc voltage detector, 32 is a welding current detector, 33 is a switch, and is connected to the arc voltage detector 31 here. When controlling by welding current, switch 33 is switched to the welding current detector 32 side.

  An arc rotation position detector 35 detects the arc rotation position (Cf, R, Cr, L) shown in FIG. Reference numeral 36 denotes a timing pulse generator which inputs the arc rotation position detected by the arc rotation position detector 35 and outputs the timing pulse to the L side integrator of the arc voltage Ea so that the integration region becomes a predetermined angle range. 37 and the R-side integrator 38 are commanded.

  The angle range commanded by the timing pulse generator 36 is 0 ° to 90 ° left and right in this example. This angle range is set in advance, and is set to 0 ° to 90 ° in the present example as described above, but is not limited to this and may be symmetrical.

  Reference numeral 39 denotes a differential amplifier that calculates the difference between the L-side integral value SL by the L-side integrator 37 and the R-side integral value SR by the R-side integrator 38. The differential amplifier 39 outputs an arc sensor output (SL-SR). ) Is required.

  The obtained arc sensor output (SL-SR) is input to the weld line scanning control circuit 40. In the welding line scanning control circuit 40, the scanning distance is calculated based on the deviation signal of the differential amplifier 39, the motor 41 is controlled based on the calculation result, and the welding torch 47 is scanned.

  In tandem arc welding, the target position of the succeeding electrode has a great influence on the bead shape, so that the effect of introducing automatic scanning by this arc welding line scanning control is great, and the quality stability in actual construction can be improved.

  In the above embodiment, the present invention is applied to horizontal fillet welding, and the relationship between the leading electrode and the trailing electrode is illustrated in FIG. 7, but the application target of the present invention is not limited to this, It can be applied to electrode arrangements other than those shown in FIG. 7 and downward welding.

DESCRIPTION OF SYMBOLS 14 ... Standing plate 16 ... Lower plate 20 ... Flux 22, 22A, 22B ... Welding wire 24A ... Leading electrode 24B ... Subsequent electrode 28 ... Welding bead

Claims (4)

When using a leading electrode and a trailing electrode to generate an arc between the welding wire and the base metal under a granular flux, when performing tandem submerged arc welding using the high heat generated by this,
Welding wire of the row electrodes after the welding wire tip prior electrodes a target position shifted to one side from the weld line, the welding wire forward has shifted to the side opposite to the leading electrode Rutotomoni rotated toward the weld line, the target position A tandem rotating submerged arc welding method, wherein the front end of the welding wire is rotated in a direction in which the front side of the welding wire approaches the welding line. During horizontal fillet welding, the target position of the leading electrode welding wire tip is shifted to the lower plate side from the welding line, and the target position of the trailing electrode welding wire tip is shifted from the welding line to the vertical plate side. The tandem rotating submerged arc welding method according to claim 1 .   When using the leading electrode and the trailing electrode to generate an arc between the welding wire and the base metal under the granular flux, and when performing horizontal fillet welding by tandem submerged arc welding using the high heat generated by this,
  The leading electrode welding wire tip is shifted from the welding line to the lower plate side, but the leading electrode welding wire tip is always rotated so that the leading electrode welding wire tip is shifted from the welding line to the upper plate side. A tandem rotating submerged arc welding method characterized by rotating in a direction approaching a welding line. In the tandem rotation submerged arc welding, the center of rotation is symmetrical with respect to Cf within a predetermined rotation condition range in which there is regularity between the front center point Cf in the welding progress direction in the arc rotation circle and the arc voltage waveform or arc current waveform. The tandem rotating submerged arc welding method according to any one of claims 1 to 3 , wherein the aiming position is controlled so that a difference between an integrated value of an arc voltage value or an arc current value in a predetermined integration region becomes a constant value. .