JP2013237103A - Multi-electrode submerged arc welding method of steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-electrode submerged arc welding method capable of controlling a bead width without considerably changing welding conditions and electrode arrangement, of increasing the bead width to prevent surface defects, such as undercut, and of forming beads in an excellent shape evenly on both sides of the weld line.SOLUTION: An N-th electrode arranged at the backmost part in the welding progress direction and an (N-1)th electrode arranged immediately before the N-th electrode are arranged on both the left side and the right side of the weld line; a distance between a wire tip end position and the weld line on the steel sheet surface of the N-th electrode and a distance between the wire tip end position and the weld line on the steel sheet surface of the (N-1)th electrode are both set within a range between 5 and 15 mm, and an electrode-to-electrode distance in the welding progress direction of the N-th electrode and the (N-1)th electrode is set within a range between 0 and 20 mm; and at the same time, a phase difference θbetween an (N-2)th electrode arranged immediately before the (N-1)th electrode and the (N-1)th electrode, a phase difference θbetween the (N-1)th electrode and the N-th electrode, and a phase difference θbetween the (N-2)th electrode and the N-th electrode are all set within a range between 60 and 300°.

Description

  The present invention relates to multi-electrode submerged arc welding of steel plates, and relates to multi-electrode submerged arc welding suitable for seam welding of large-diameter steel pipes such as UOE steel pipes and spiral steel pipes.

For seam welding of large-diameter steel pipes such as UOE steel pipes and spiral steel pipes, submerged arc welding using two or more electrodes (see, for example, Patent Documents 1 and 2) is widespread. From the viewpoint of improving the productivity of large-diameter steel pipes, High-efficiency double-sided single-layer welding, in which the inner surface side is welded in one pass and the outer surface side is welded in one pass, is widely adopted.
In double-sided single-layer welding, it is necessary to secure a depth of penetration so that the weld metal on the inner surface side and the weld metal on the outer surface side are sufficiently overlapped, and unmelted parts do not occur. It is common to supply and perform welding.

On the other hand, seam welding of large-diameter steel pipes has a problem that the toughness of the welded part, particularly the heat-affected zone, is deteriorated, and it is necessary to reduce the welding heat input as much as possible in order to improve the toughness of the welded part. However, if the welding heat input is reduced, there is a problem that the risk of inadequate penetration increases, an unmelted portion is likely to occur, and surface defects such as undercuts are likely to occur.
In order to suppress surface defects such as undercut, it is necessary to obtain a wide bead width, and welding conditions for that purpose are being studied. For example, Patent Document 3 discloses a technique for expanding the bead width by supplying two wires to one torch so as to be arranged at right angles to the welding line direction and performing welding. However, with this technique, it is difficult to greatly increase the bead width, and it is difficult to sufficiently increase the bead width in the welding of thick materials having a plate thickness exceeding 20 mm.

Patent Document 4 discloses a technique for adjusting a bead shape by applying a magnetic field to an unsolidified weld metal during welding. However, in this technique, in addition to the welding device, a device for applying a magnetic field must be used together, so that the configuration becomes complicated and the maintenance load of the device increases.
Patent Documents 5 and 6 disclose a technique for expanding a bead width by arranging a plurality of electrodes at intervals from a welding line and performing welding. However, with the techniques disclosed in Patent Documents 5 and 6, it has been difficult to increase the bead width evenly on both sides of the weld line over the entire length of the weld. In particular, in high heat input welding, even though the toughness of the heat affected zone is an issue, the formation of a bead that is biased to one side forms a Charpy impact test that is a toughness evaluation test for the weld heat affected zone. The absorbed energy varies greatly depending on whether the piece is taken from the left or right side of the bead, and there is a problem that stable mechanical performance cannot be obtained.

Japanese Patent Laid-Open No. 11-138266 Japanese Patent Laid-Open No. 10-109171 JP 7-266047 A Japanese Patent Laid-Open No. 2002-120068 Japanese Patent Publication No. 63-39350 JP-A-8-257752

  The present invention controls the bead width without significantly changing the welding conditions and electrode arrangement, and also enlarges the bead width to prevent surface defects such as undercuts, An object of the present invention is to provide a multi-electrode submerged arc welding method that can be uniformly formed on both sides.

The inventor performed submerged arc welding using three or more electrodes and produced welded joints of steel plates under various welding conditions. And as a result of investigating the relationship between the obtained bead shape and welding conditions,
(a) The rearmost Nth electrode and the immediately preceding N-1 electrode are disposed on both sides of a trajectory (hereinafter referred to as a welding line) through which the first electrode disposed at the head in the welding progress direction passes. The bead width can be expanded by
(b) By supplying an alternating current to the Nth electrode, the N-1 electrode, and the N-2 electrode arranged immediately before the N-1 electrode, and adjusting the phase difference thereof, a good shape It was found that the bead can be formed evenly on both sides of the weld line. The present invention has been made based on these findings. Here, N is an integer of 3 or more and indicates the number of electrodes.

That is, according to the present invention, in a multi-electrode submerged arc welding method for welding steel plates by submerged arc welding of three or more electrodes, the Nth electrode disposed at the end of the welding progress direction and the first electrode disposed immediately before the Nth electrode. N-1 electrodes are arranged on both the left and right sides of the weld line, and the distance between the wire tip position on the steel plate surface of the Nth electrode and the weld line, and the wire tip position on the steel plate surface of the N-1 electrode and the weld line. All the distances are within the range of 5 to 15 mm, and the distance between the electrodes in the welding progress direction of the Nth electrode and the (N-1) th electrode is within the range of 0 to 20 mm, and is disposed immediately before the (N-1) th electrode. phase difference theta ₁ of the first N-2 electrode and the N-1 electrodes, the phase difference theta ₂ between the first N-1 electrode and the N electrodes, the phase difference between the first N-2 electrode and the N electrode theta ₃ in the multi-electrode submerged arc welding method in the range of either 60 to 300 ° to That.

  In the multi-electrode submerged arc welding method of the present invention, the total heat input of submerged arc welding of three or more electrodes is preferably 7.0 kJ / mm or more. More preferably, the total is 7.0 to 10.0 kJ / mm. Moreover, it is preferable that the wire diameter of the 1st electrode arrange | positioned at the head of a welding progress direction shall be 2.4-3.2 mm.

  According to the present invention, it is possible to control the bead width without significantly changing the welding conditions and electrode arrangement. As a result, in multi-electrode submerged arc welding, the bead width is increased to undercut or the like. By forming evenly shaped beads on both sides of the weld line, high toughness can be obtained in both the heat affected zone on the left and right sides of the bead. Play.

It is a perspective view which shows typically the example of the multi-electrode submerged arc welding method of this invention. It is a side view of the electrode and steel plate in FIG. It is a top view which shows the front-end | tip position in the steel plate surface of the wire in FIG. It is sectional drawing which shows the example of groove shape. It is sectional drawing which shows the example of a welded joint. It is sectional drawing which shows the collection position of a Charpy impact test piece.

  FIG. 1 is a perspective view schematically showing an example in which steel plates are welded by applying the multi-electrode submerged arc welding method of the present invention, and FIG. 2 is a side view thereof. FIG. 3 is a plan view showing the tip position of each wire in FIG. 1 on the steel plate surface. Below, with reference to FIGS. 1-3, the multi-electrode submerged arc welding method of this invention is demonstrated. In addition, although the example using four electrodes is shown in FIGS. 1-3, this invention is a multi-electrode submerged arc welding method using three or more electrodes, and does not limit an electrode to four.

  As shown in FIG. 1, when four electrodes are used (N = 4), the first electrode 1 in the welding progress direction indicated by the arrow A is the first electrode 1 and the tip position of the wire 12 of the first electrode 1 Let the trajectory on the surface of the steel plate 5 through which welding passes be the weld line 6. The second electrode in the welding progress direction A is used as the second electrode 2 and is arranged behind the first electrode 1. The tip position of the third third electrode (N-1 electrode) 3 and the tip position of the fourth fourth electrode (Nth electrode) 4 in the welding progress direction A are respectively arranged on the left and right sides of the weld line. One wire 12, 22, 32, and 42 is supplied to each of the torches 11, 21, 31, 41 of each electrode.

First, the first electrode will be described.
The current supplied to the wire 12 of the first electrode 1 can supply a direct current in order to ensure the penetration depth. However, when the present invention is applied using three electrodes (N = 3), an alternating current is supplied to the first electrode 1.
Further, as shown in FIG. 2, the first electrode 1 is formed by inclining the wire 12 so that the tip of the wire 12 is positioned behind the torch 11 in the welding progress direction A (that is, the last electrode side). It is preferable to set. If the angle α (hereinafter referred to as the receding angle) formed by the wire 12 and the vertical line is set to 5 to 10 °, the effect of increasing the penetration depth appears significantly, which is preferable.

In addition, since the current density is increased by setting the wire diameter of the first electrode to 2.4 to 3.2 mm, the arc pressure is increased and a deep penetration can be obtained.
Next, the second electrode will be described.
As shown in FIG. 3, the second electrode 2 is set so that the tip position 23 of the wire 22 on the steel plate surface is disposed on the weld line 6. The current supplied to the wire 22 of the second electrode 2 supplies an alternating current in order to prevent arc interference with other electrodes.

When the present invention is applied using three electrodes, the tip position 23 of the wire 22 of the second electrode 2 is not arranged on the welding line 6, and the second electrode 2 and the last third electrode Are arranged on the left and right sides of the weld line 6 respectively.
When the present invention is applied using five or more electrodes, the third to N-2 electrodes are arranged on the weld line 6 behind the second electrode 2, and the N-1 electrode 2 The rearmost Nth electrode is arranged on each of the left and right sides of the welding line 6. Here, N indicates the number of electrodes.

Next, the last fourth electrode and the third electrode immediately before will be described.
As shown in FIG. 3, the third electrode and the fourth electrode are set so that the tip positions 33 and 43 of the wires 32 and 42 on the steel plate surface are arranged on the left and right sides of the welding line 6, respectively.
If the distance W _R between the tip position 33 of the wire 32 of the third electrode 3 and the weld line 6 and the distance W _L between the tip position 43 of the wire 42 of the fourth electrode 4 and the weld line 6 are less than 5 mm, the width of the bead The effect of spreading is not obtained. When the distance W _R and distance W _L exceeds 15 mm, the weld metal of the third electrode 3 and the fourth electrode 4, so it separated from the weld metal first electrode 1 and the according to the second electrode 2, a bead is formed separately And the appearance of the bead is impaired. Therefore, the distance W _R and the distance W _L are both 5 to 15 mm. The distance W _R and the distance W _L are not necessarily the same, but it is preferable to set W _R = W _L in order to form a bead having a good shape and prevent undercut.

When the interelectrode distance G between the third electrode 3 and the fourth electrode 4 exceeds 20 mm, the variation in the bead width increases. Therefore, the inter-electrode distance G between the third electrode 3 and the fourth electrode 4 is set to 20 mm or less. Here, the inter-electrode distance is an interval in the welding progress direction at the tip position of the wire.
The current supplied to the wires 32 and 42 supplies an alternating current to prevent arc interference between the electrodes. Phase difference θ ₁ between the second electrode (N-2 electrode) and the third electrode (N-1 electrode), the position of the third electrode (N-1 electrode) and the fourth electrode (Nth electrode) When the phase difference θ ₂ and the phase difference θ ₃ between the second electrode (N-2 electrode) and the fourth electrode (N electrode) are less than 60 °, a bead that is biased to one side of the weld line 6 is formed. Even if the phase differences θ ₁ , θ ₂ , and θ ₃ exceed 300 °, a bead that is biased to one side of the weld line 6 is formed. Accordingly, the phase differences θ ₁ , θ ₂ , and θ ₃ are all set to 60 to 300 °.

  Further, as shown in FIG. 2, the third electrode 3 and the fourth electrode 4 are such that the tips of the wires 32 and 42 are positioned in front of the torch 31 and 41 in the welding progress direction A (that is, the first electrode side). Further, it is preferable to set the wires 32 and 42 to be inclined. If the angle β (hereinafter referred to as the advance angle) formed by the wires 32 and 42 and the vertical line is set to 10 to 50 °, the effect of widening the width of the bead appears remarkably, which is preferable.

  The example using four electrodes has been described above. However, the present invention is not limited to four electrodes, and can be applied to multi-electrode submerged arc welding using three or more electrodes, particularly 3-5. A remarkable effect is obtained when the book electrode is used. When the present invention is applied to high heat input welding where the sum of welding heat input of these electrodes totals 7.0 kJ / mm or more, the problem of conventional high heat input welding that the toughness of the heat affected zone decreases is solved. It is preferable because the toughness of the weld heat affected zone can be improved.

The present invention can be applied to various plate thicknesses and groove shapes, and can be applied to single-sided welding and double-sided welding.
Furthermore, in general, a solid wire is used in submerged arc welding, but the present invention can be applied not only to a solid wire but also to a metal cored wire including metal powder or the like as a filler.

  As shown in FIG. 4, after the groove processing is performed on a steel plate 5 having a thickness T of 31.8 mm and a groove angle γ of 70 ° and a groove depth D of 13.5 mm, 3 to 5 electrodes are used. Then, multi-electrode submerged arc welding was performed to produce a welded joint as shown in FIG. Table 1 shows the components of the steel sheet, Table 2 shows the groove shape, Table 3 shows the welding conditions, Table 4 shows the electrode arrangement, and Table 5 shows the setting of the welding current.

  The bead appearance of the obtained welded joint was visually observed, and the width B (mm) of the bead steady portion, the interval Q (mm) between the width direction center of the bead and the groove center, and the penetration depth (mm) ) Was measured. In addition, a Charpy impact test piece (No. 4 test piece specified in JIS standard Z3111) is taken from the stationary part, and a Charpy impact test is performed in accordance with the metal material impact test method of JIS standard Z2242, and the absorbed energy (J) is measured. Asked. The Charpy impact test was performed for each welded joint at a test temperature of −30 ° C., 20 pieces each, and the minimum value of absorbed energy was evaluated.

The sampling position of the Charpy impact test piece is as shown in FIG. In other words, the sample is taken so that the position of 7 mm from the steel sheet surface layer is the center position in the thickness direction of the Charpy impact test piece 7, the 2 mm V notch of the test piece is parallel to the thickness direction, and the weld metal and the base metal ( The welding heat-affected zone was set at a position where the ratio was 50%.
Of the 20 Charpy impact test specimens collected from each welded joint, 10 were collected from the left side in the welding progress direction of the beads, and 10 were collected from the right side. Table 6 shows the bead width, the distance between the center of the bead width and the center of the groove, the penetration depth, the minimum value of absorbed energy measured by the Charpy impact test, and the evaluation of the bead appearance.

As shown in Table 6, the weld symbols 1 to 12 (N = 3 to 5) of the inventive examples were able to obtain a wide bead width and to suppress the bead unevenness. In particular, each of the welding symbols [1, 2], [3, 4], [5, 6], [7, 8], [9, 10], [11, 12] can change the bead width only by phase difference control. In the above six sets, the bead width could be changed by 2 mm or more.
In addition, welding symbols 3, 4, 5, 6, 9, 10, 11, and 12 used a wire having a wire diameter of 2.4 mm or 3.2 mm for the first electrode, and thus a particularly deep penetration was obtained.

The weld symbol 13 (N = 5) of the comparative example is an example in which all the electrodes are arranged on the weld line, and the bead width is the narrowest.
In welding symbol 14 (N = 5), since the position of the wire tip on the steel plate surface of the second N-1 electrode (that is, the fourth electrode) from the tail was less than 5 mm, a wide bead width was not obtained.
The welding symbol 15 (N = 5) indicates that the wire tip position on the steel plate surface of the Nth electrode at the end (namely, the fifth electrode) and the second N-1 electrode (namely, the fourth electrode) from the tail is Also, since it exceeded 15 mm, the beads were formed separately.

Further, the above welding symbols 16, 17, 18, and 19 could not obtain high absorbed energy in the welding heat affected zone.
The welding symbol 16 (N = 5) is a phase difference θ between the third N-2 electrode (ie, the third electrode) from the tail and the second N-1 electrode (ie, the fourth electrode) from the tail. _{Since 1} was less than 60 °, the bead bias increased. Since the weld symbol 17 (N = 5) has a phase difference θ ₁ exceeding 300 °, the bead deviation is large.

The welding symbol 18 (N = 5) indicates that the phase difference θ ₃ between the third N-2 electrode (that is, the third electrode) from the tail and the last N electrode (that is, the fifth electrode) is less than 60 °. As a result, the bead bias became larger. Since the weld symbol 19 (N = 5) has a phase difference θ ₃ exceeding 300 °, the deviation of the bead is large.
The welding symbols 20 and 21 (N = 5) have a phase difference θ ₂ of 60 between the _second N−1 electrode (ie, the fourth electrode) from the tail and the Nth electrode (ie, the fifth electrode) at the tail. Since the angle was less than 0 °, the bead width could not be changed by 2 mm or more. For the welding symbols 22 and 23 (N = 5), the phase difference θ ₂ exceeded 300 °, so that the bead width could not be changed by 2 mm or more.

  The welding symbol 24 (N = 5) is because the inter-electrode distance G between the second N-1 electrode (that is, the fourth electrode) and the last Nth electrode (that is, the fifth electrode) from the tail exceeds 20 mm. The bead width became non-uniform, high absorbed energy could not be obtained in the weld heat affected zone, and a beautiful bead appearance could not be obtained.

1 First electrode
11 First electrode torch
12 First electrode wire
13 Tip position of the wire of the first electrode 2 Second electrode
21 Second electrode torch
22 Second electrode wire
23 End position of wire of second electrode 3 Third electrode
31 Third electrode torch
32 Third electrode wire
33 Tip position of third electrode wire 4 Fourth electrode
41 4th electrode torch
42 Fourth electrode wire
43 Tip position of wire of 4th electrode 5 Steel plate 6 Weld line 7 2mm V notch Charpy impact test piece

Claims (3)

  In a multi-electrode submerged arc welding method for welding steel plates by submerged arc welding of three or more electrodes, an Nth electrode disposed at the end of the welding progress direction and an N-1 electrode disposed immediately before the Nth electrode Are arranged on the left and right sides of the weld line, the distance between the wire tip position on the steel sheet surface of the Nth electrode and the weld line, and the distance between the wire tip position on the steel sheet surface of the N-1 electrode and the weld line. Are within the range of 5 to 15 mm, and the distance between the N-th electrode and the N-1 electrode in the welding direction is within the range of 0 to 20 mm, and immediately before the N-1 electrode. The phase difference between the N-2 electrode and the N-1 electrode, the phase difference between the N-1 electrode and the Nth electrode, and the N-2 electrode and the Nth electrode. All of the phase differences are in the range of 60 to 300 °. Multielectrode submerged arc welding method.   2. The multi-electrode submerged arc welding method according to claim 1, wherein the total heat input of the three or more submerged arc weldings is 7.0 kJ / mm or more.   3. The multi-electrode submerged arc welding method according to claim 1, wherein the wire diameter of the first electrode arranged at the head in the welding progress direction is set to 2.4 to 3.2 mm.

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