JPH07266047A - Welding method for manufacture of tube - Google Patents

Abstract

PURPOSE:To attain a defectless weld zone with a high speed welding by combining gas metal arc welding and submerged arc welding using parallel arcs, and specifying the interval of wires with a slender diameter in the submerged arc welding. CONSTITUTION:In welding for manufacture off a tube, first of all, submerged arc welding with one molten pool two electrodes, is performed from an internal surface side. Next, gas metal arc welding with one electrode, is performed from an external surface side. Successively, submerged arc welding with one molten pool three electrodes, is performed on it. In the submerged arc welding, plural wires with a slender diameter, are arranged at right angle to a weld line direction, and parallel arc electrodes in which the interval of the wires with a slender diameter is within four times the wire diameter, are adopted. For a preceding electrode, a DC power source is used, and for the other electrodes, an AC power source is used. After securing the deep depth of penetration by gas metal arc welding, external surface welding can be made speedy by an allotted function performing submerged welding with a large deposited amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe-making welding method used for producing a submerged arc welded steel pipe, and more particularly to a high-speed welding method in which multiple electrodes and parallel arcs are combined.

[0002]

2. Description of the Related Art Welded steel pipes are roughly classified into electric resistance welded steel pipes, forged welded steel pipes and submerged arc welded welded steel pipes according to the type of welding. Of these, submerged arc welded steel pipes are usually large-diameter steel pipes, and UO
It is divided into E steel pipe and spiral steel pipe.

The UOE steel pipe is manufactured by forming a cut plate into an open pipe, temporarily attaching the abutting portions of its side edges by gas metal arc welding, and then performing submerged arc welding from the inner surface side and the outer surface side. It is customary. The tack weld by gas metal arc welding is completely remelted by the subsequent submerged arc welding, and the weld metal does not remain behind.

On the other hand, manufacture of a spiral steel pipe is usually carried out by forming a steel strip into a spiral shape and submerged arc welding the side edge butting portions from the inner surface side and the outer surface side, respectively.

The production speed of these submerged arc welded steel pipes is slower than the production speed of other welded steel pipes. For example, in the production of spiral steel pipes, the welding electrodes on the inner and outer surfaces are made into multiple electrodes so that both the inner and outer surfaces can be formed in one pass. The efficiency is improved by welding.

Aside from the use of multiple electrodes, a high-efficiency submerged arc welding method using a parallel arc for generating a single arc from two parallel welding wires using the same welding electrode and wire feeding mechanism has been known for a long time. (E.g. J.
E.Hinkel and FW Worsthoefel: "Submerged Arc Weldi
ng with Twin Electrodes ", Welding Journal, March (197
6) p175).

As a technique for performing highly efficient submerged arc welding by combining multiple electrodes and parallel arcs,
The following are presented: A) JP-A-52-97344 B) JP-A-58-125373 C) JP-A-61-212480 D) JP-A-61-232067 E) JP-A-62-9777 F) Japanese Patent Laid-Open No. 4-71782

These will be described below with reference to FIG.
In the figure, 1 is a welding wire, 2 is a tip, 3 is a pool, and 4 is a bead. It is a normal electrode that sends out one welding wire 1 from one tip 2 and a parallel arc electrode that sends out two welding wires 1 and 1 from one tip 2. The welding wires 1, 1 in the parallel arc electrodes may be arranged parallel to the welding line direction or may be arranged at right angles. A thin wire is used as the welding wires 1, 1.

Method A employs a parallel arc electrode as the leading electrode of the multiple electrodes. The two thin wires in the parallel arc electrode are arranged at right angles to the welding line direction.

Method B employs a parallel arc electrode for any one of the multiple electrodes. Method C employs parallel arc electrodes for all of the multiple electrodes. The two thin wires in the parallel arc electrode are both arranged parallel to the welding line direction.

The method D is characterized in that a plurality of pools are formed and a parallel arc electrode is adopted as the final pool. The two thin wires in the parallel arc electrode may be arranged parallel to the welding line direction or may be arranged at right angles to the welding line direction.

The E method employs parallel arc electrodes for the last electrode of the multiple electrodes and the electrode immediately before it. The F method employs parallel arc electrodes for the three electrodes to shape the electric resistance welded portion, displacing the leading electrode to one side and the next electrode to the other side with respect to the welding center line. It is a feature. The two thin wires in the parallel arc electrode are both arranged parallel to the welding line direction.

To summarize the above, it is the A and D methods that employ the "right angle" parallel arc electrodes in which two thin wires are arranged at right angles to the welding line direction, and the other two A "parallel arrangement" of parallel arc electrodes in which the thin wires are arranged parallel to the welding line direction is adopted.

[0014]

In these conventional methods, due to the limitation of the penetration depth and the surface defect of the bead, even if the plate thickness is about 10 mm, 3 m / mi except for the F method.
High-speed welding exceeding n is difficult. Also, the high speed in the F method is largely due to the combination of electric resistance welding and submerged arc welding, and it is difficult to achieve high speed welding exceeding 3 m / min only by submerged arc welding.

An object of the present invention is to provide a pipe welding method capable of obtaining a sound welded portion even at a welding speed of more than 3 m / min and more than 5 m / min when the plate thickness is 10 mm or more. is there.

[0016]

The reason why high-speed welding exceeding 3 m / min is difficult by the conventional method is basically that submerged arc welding alone cannot provide a sufficient penetration depth. The present inventors have been continuing research focusing on combination with gas metal arc welding in order to compensate for insufficient penetration in submerged arc welding, and as one of the results, "steel strip is formed into a tubular shape. After performing submerged arc welding or carbon dioxide arc welding on the butt portion from either the inner surface side or the outer surface side, perform carbon dioxide gas arc welding from the other side while the welding portion has a temperature of 150 ° C. Japanese Patent Application No. 4-2.
Filed under No. 03111.

The greatest feature of this method is that, among the gas metal arc welding, a carbon dioxide gas arc welding, which provides a particularly deep penetration depth, ensures a sufficient penetration depth, and a submerged arc welding with a large amount of welding is performed from above. There is something to do. That is, the functions of securing the penetration depth and securing the amount of welding are shared, and the burden of submerged arc welding is reduced, thereby increasing the speed.

However, if the gas metal arc welding having a deep penetration depth is performed prior to the submerged arc welding, the welded portion by the gas metal arc welding remains after the submerged arc welding. As shown in FIG. 3, the welded portion formed by gas metal arc welding has a high central portion,
Narrow and deep valleys occur on both sides. The valleys on both sides surrounded by the broken line are likely to remain as a fusion defective portion after the submerged arc welding, which hinders the speedup. Moreover, even if the burden of submerged arc welding is reduced by gas metal arc welding,
When the submerged arc welding is carried out at high speed, unevenness of bead wrinkles occurs due to poor wetting of the molten metal, and this surface defect also hinders the speedup. For these reasons, the expected speed-up cannot be realized.

In order to solve this problem, Japanese Patent Application No. 4-2
The method of No. 03111 uses the residual heat of the welded portion by the arc welding performed from the back side prior to the gas metal arc welding, but apart from this, the high efficiency submerged arc welding method by the parallel arc described above also solves this problem. The present inventors have newly found that it is effective for various studies.

The present invention was made on the basis of the above findings. Steel plates were formed into a tubular shape, and submerged arc welding was performed from the inner surface side to the abutting portion and gas metal arc welding was performed from the outer surface side. Pipe welding for welding, wherein submerged arc welding from the inner surface side and the outer surface side is one pool multi-electrode welding with two or more electrodes, and one electrode other than the preceding electrode is included in the multi-electrode.
A parallel arc electrode in which two thin wires are arranged at right angles to the welding line direction in two or more poles and the distance between the thin wires is within 4 times the wire diameter A gist of the pipe welding method is characterized in that a DC power source is used for the other electrode and an AC power source is used for the other electrode.

The pipe-making welding method of the present invention is particularly suitable for producing a spiral steel pipe due to its process.

As the gas metal arc welding, carbon dioxide gas arc welding is preferable because it is easy to obtain a deep penetration depth. Further, it is desirable to perform the welding at a stage where the welded portion by submerged arc welding performed from the inner surface side has a temperature of 150 ° C. or higher.

In the production of UOE steel pipes, temporary joining by gas metal arc welding is performed prior to submerged arc welding. The temporary joining welding is completed by submerged arc welding in which the welded portion is continued as described above. However, the burden of submerged arc welding has not been reduced yet. Even if a sufficient penetration depth is secured in the gas metal arc welding, the expected speeding up cannot be realized due to the above-mentioned defective fusion and uneven beading.

[0024]

In the pipe-making welding method of the present invention, after the deep penetration depth is secured by gas metal arc welding, the function of performing submerged arc welding with a large amount of deposition is shared to speed up the outer surface welding, and to combine the outer surface welding. The first feature is to speed up the welding by reducing the burden of the inner surface welding by speeding up the welding.

A second feature is that parallel arc welding is adopted for submerged arc welding from the inner surface side and the outer surface side, and in inner surface welding, high speed welding is enabled by preventing unevenness of bead wrinkles, and in outer surface welding, In addition to this, by preventing the fusion failure of the valley portions shown in FIG. 3, it is possible to perform high-speed welding of each.

In the following, parallel arc welding employed in the pipe welding method of the present invention prevents uneven bead wrinkles in submerged arc welding and fusion failure when gas metal arc welding is performed prior to submerged arc welding ( (Fig. 3)
Explain that it is effective in preventing

It is known that the bead formation in multi-electrode submerged arc welding depends on the trailing electrode (for example, Kawasaki Steel Technical Report Vol. 6 No. 4 (1974) P100). Therefore, the present inventors examined the application of a parallel arc electrode that generates a single arc from two thin wires using the same welding power source and wire feeding mechanism to the trailing electrode. As a result, it has been found that the unevenness of the bead wrinkles can be prevented only when a parallel arc electrode in which two small-diameter wires are arranged at right angles to the welding line direction is applied to the trailing electrode. This is because the two thin wires are placed in the same electrode at right angles to the welding line direction, and the arc generated in each wire is stably directed toward both sides by the electromagnetic force. The reason is that the bead is constantly pushed to the edge.

Therefore, in the pipe welding method of the present invention, the parallel arc electrodes arranged at right angles are applied to one or more poles including at least one pole other than the preceding electrode.

Even if this parallel arc electrode arranged at a right angle is applied to the leading electrode, if this parallel arc electrode is applied to at least one electrode of the trailing electrode, there is no problem in bead formation, but the penetration depth The problem arises that the depth becomes shallow. Therefore, it is desirable to use a normal electrode that uses one welding wire as the leading electrode. The parallel arc electrodes arranged at right angles to the leading electrode are used when the plate thickness is relatively thin and the conditions for the penetration depth are relaxed.

When the number of electrodes is three or more, the final electrode may be a normal electrode without any great difference. This seems contrary to the idea that the trailing electrode plays a major role in bead formation, but in the case of three or more electrodes, bead formation is possible if the trailing electrode before the final pole is stabilized. It is found from the investigation by the present inventors that excellent results can be obtained.

According to the investigation conducted by the present inventors, a parallel arc electrode in which two thin wires are arranged at a right angle to the welding line direction has a parallel arc electrode, which is shown in FIG. It was also found to be effective in prevention. That is, according to the right-angled arrangement, when the two small-diameter wires intensively remelt the valleys on both sides surrounded by the broken line in FIG. 3, and the submerged arc welding is performed at high speed after the gas metal arc welding. Also,
No fusion failure remains.

In order to prevent defective fusion with the parallel arc electrodes arranged at right angles, it is necessary to narrow the distance (gap) between the two thin wires to within 4 times the wire diameter, preferably within 3 times. More preferably, it is within 2.5 times. When the distance between the thin wires increases, the fusion defects in the valleys on both sides will remain. Regarding the lower limit of the wire interval, from the point of interference of the arc generated from the two thin wires, the wire diameter is 0.5.
It is preferably double or more, more preferably once or more.

The diameter of the thin wire in the parallel arc electrode is preferably 1.6 to 2.0 mm. If it is less than 1.6 mm, it may not be possible to feed it due to the occurrence of a waist break in the wire feeding cable, and if it exceeds 2.0 mm, it may be difficult to simultaneously and stably feed two thin wires.

The wire diameter of the normal electrode is 3.2.
~ 4.8 mm is desirable. If it is less than 3.2 mm, the amount of welding cannot be secured due to the limitation of the current value that can be used, and if it exceeds 4.8 mm, the current density becomes low and the amount of welding becomes insufficient, so a very large capacity is required to secure an appropriate current density. It is necessary to use a power source that has power, which is economically disadvantageous.

The most desirable electrode arrangement of the multi-electrode submerged arc welding in the pipe welding method of the present invention is that the leading electrode is a normal electrode and the trailing electrode is a parallel arc electrode in two electrodes, and the leading electrode is in three or more electrodes. The normal electrode and the other electrode are parallel arc electrodes.

Among the above-mentioned conventional methods, the A method and the D method use parallel arc electrodes arranged at right angles, but the A method applies the parallel arc electrodes only to the leading electrode, so that the bead wrinkles are particularly stabilized. I can't. Further, since the D method forms a plurality of pools and uses parallel arc electrodes arranged at right angles in the final pool, high speed welding cannot be performed. Because the welding speed depends on the amount of welding per unit time,
Even if the number of electrodes is the same, if the pool is divided, the amount of welding per pool will decrease. That is, the welding speed is rate-controlled from the viewpoint of the amount of welding.

Therefore, in the pipe manufacturing welding method of the present invention, one pool multi-electrode welding is used in principle, and parallel arc electrodes arranged at right angles to one or two or more poles including at least one pole other than the preceding electrode of the multi-electrode. I decided to adopt it.

As a power source, a direct current power source is used for the leading electrode,
The AC power supply is used for the other pole because the DC power supply has a more stable arc, but the multi-electrode method using only the DC power supply causes magnetic spraying and makes the arc unstable. I used it as a power source. Since the DC power source is easier to secure the melted amount, the DC power source is used for the leading electrode.

In the gas metal arc welding, it is advantageous that the wire diameter is thin in comparison of the deposition rates at the same current, but if it is less than 3.2 mm, the upper limit of the usable current value is low, so a sufficient deposition amount is secured. Can not. On the contrary, if it exceeds 4.8 mm, the current value for stabilizing the arc at a high speed becomes very large, and the welding power source becomes expensive. Therefore, the wire diameter in gas metal arc welding is 3.2 to 4.8.
mm is preferable, and 4.0 mm or less is particularly preferable. This diameter is considerably larger than the wire diameter normally used for gas metal arc welding (around 1.2 mm).

[0040]

EXAMPLES Next, examples of the present invention will be shown and the effects thereof will be clarified by comparison with comparative examples.

As welding for manufacturing a spiral steel pipe for a pile having an outer diameter of 609.6 mm and a thickness of 16 mm specified by JIS G3444 as STK490, first, submerged arc welding of one pool and two electrodes is performed from the inner surface side, and then the outer surface. Gas metal arc welding of one electrode (carbon dioxide welding) was performed from the side, and subsequently submerged arc welding of one pool and three electrodes was performed from above.

The electrode arrangement in submerged arc welding is the same as in FIG. 1 for two-electrode welding from the inner surface side.
B, C, and D, and a, b, c, d, e, and f in FIG. 1 for three-electrode welding from the outer surface side.

Frac for submerged arc welding is made of SiO.
_{A 2-} MnO type molten flux was used. The wire used was 1.2% Mn system for gas metal arc welding and 1.5% Mn system for submerged arc welding. Wire diameter is 4 mm for gas metal arc welding and 4 mm (normal electrode) or 2 mm (parallel arc electrode) for submerged arc welding.
And The wire spacing in the parallel arc electrode is
It was 4 mm, which is twice the wire diameter.

The groove shape was a V-groove having a depth of 3 mm and an opening angle of 50 ° on the inner surface side, and a V-groove having a depth of 9 mm and an opening angle of 40 ° on the outer surface side.

As a power source, a direct current power source is used for the leading electrode,
An AC power supply was used for the other pole. The welding current and voltage are as follows. Inner surface 2 electrodes SAW: 1400A (36V) -850A
(45V) Outside GMAW: 1350A (26V) Outside 3 electrodes SAW: 1700A (35V) -1150
A (40V) -850A (35V)

The welding quality when welding was performed at a welding speed of 5.3 m / min (constant) was investigated. The survey results are shown in Table 1. The temperature of the inner surface submerged arc welded portion when the gas metal arc welding was performed from the outer surface side was 120 ° C, which was lower than 150 ° C.

[0047]

[Table 1] * 1 Insufficient penetration * 2 Insufficient amount of welding * 3 Random bead wrinkle * 4 Poor fusion

No. 1 is a case where submerged arc welding of two electrodes on the inner surface and three electrodes on the outer surface, which is a general spiral pipe welding method, is performed. Since the outer surface gas metal arc welding was not performed, at the high-speed welding of 5.3 m / min, insufficient penetration occurred in the outer surface welding and the welding amount was insufficient.

With regard to the inner surface welding, in any case, in order not to cause deficiency in the penetration depth and the welding amount,
The groove is shallower than that of external welding.

Since No. 2 was subjected to outer surface gas metal arc welding, the penetration depth and the amount of welding in the multi-face welding were sufficient. However, since parallel arc welding is not used for inner / outer surface submerged arc welding, fusion defects occur in the valley portions shown in FIG.

No. 3 used a parallel arc for the inner and outer surface submerged arc welding, but the two thin wires in the parallel arc electrode were not arranged at right angles, but were arranged parallel to the welding line direction, resulting in poor fusion. And bead ruffles were not prevented.

No. 4 employs parallel arc electrodes arranged at right angles, but since the parallel arc electrodes are used only for the leading electrodes, the problem of uneven bead wrinkles has not been solved.

On the other hand, Nos. 5 to 7 used parallel arc electrodes arranged at right angles to one or more poles including at least one pole other than the preceding electrode of the multi-electrode for inner and outer surface submerged arc welding. Despite the high-speed welding of 5.3 m / min, a sound weld was obtained.

When performing external gas metal arc welding,
The temperature of the inner submerged arc weld is 150 ℃ or more 1
At 75 ℃, it is 5.6, which is faster than 5.3m / min.
The same result as in Table 1 was obtained at m / min.

As described above, according to the pipe manufacturing welding method of the present invention, high-speed welding of 5 m / min or more was realized even in the manufacture of a spiral steel pipe having a plate thickness of 16 mm.

Although the above-described embodiment is suitable for the spiral pipe according to the present invention, it can be applied to the production of UOE steel pipe, and the technique can be applied to thick plate welding and the like.

[0057]

As described above, the pipe welding method of the present invention uses the combination of gas metal arc welding and submerged arc welding using parallel arc to achieve a plate thickness of 1
5m / min for 0 mm or more, and even for 15 mm or more
Enables the above high quality and high speed welding. Therefore, a great effect is exerted in improving the pipe manufacturing efficiency and thereby reducing the pipe manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an electrode arrangement example of submerged arc welding in the method of the present invention, together with a conventional arrangement and a comparison arrangement.

FIG. 2 is a schematic diagram showing an electrode arrangement for conventional submerged arc welding using parallel arcs.

FIG. 3 is a schematic diagram showing a penetration shape in gas metal arc welding.

[Explanation of symbols]

 1 Welding wire 2 Tip 3 Pool 4 Bead

Claims (1)

[Claims] 1. A pipe-making welding in which a steel plate is formed into a tubular shape, and the butted portion is subjected to submerged arc welding from the inner surface side, gas metal arc welding is performed from the outer surface side, and then submerged arc welding is performed. Submerged arc welding from the inner surface side and the outer surface side is one-pool multi-electrode welding with two or more electrodes, and two thin wires with one or more poles including one pole other than the preceding electrode Are arranged at right angles to the direction of the welding line, and the parallel arc electrodes are used in which the distance between the thin wires is within 4 times the wire diameter. A DC power source is used for the leading electrode and an AC power source is used for the other pole. A method for welding pipes characterized in that