JPH10314946A - Two electrode submerged arc welding method for box column corner joint - Google Patents

Abstract

[PROBLEMS] To provide a submerged arc welding method capable of obtaining a weld having excellent penetration resistance and excellent hot cracking resistance by box column corner joint welding. SOLUTION: When welding a Y-shaped groove having an angle of 40 ° or less, sealing welding is performed in advance on the entire groove, and the groove width W (mm) of the surface of the sealing weld bead and the wire diameter D (mm) of the leading electrode. ) And a ratio W / D of 0.4 to 1.5, wherein the box-column joint is a two-electrode submerged arc welding method, and the sealing welding is performed using a flux-cored wire or a solid wire. To be performed by carbon dioxide shielded arc welding. According to the welding method of the present invention, it is possible to obtain a sound weld having no poor penetration and excellent resistance to high-temperature cracking, so that highly efficient production of a box column can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method applied to the manufacture of column members of a building structure, and more particularly, to a box joint of a box column, which is free from poor penetration and has high hot cracking resistance. The present invention relates to a submerged arc welding method for obtaining a weld having excellent weldability.

[0002]

2. Description of the Related Art In recent years, submerged arc welding of box column corner joints has been required to achieve a plate thickness of 40 to 10 with the increase in height of buildings and the like.
The application to a 0 mm extra-thick steel plate has increased.

[0003] In the manufacture of a box column, a joining portion of the skin plates 1 and 2 shown in FIG. 2, that is, a box-shaped four-sided corner portion is welded into a hollow column. The groove shape of the square joint differs depending on the plate thickness, and the Y-shaped groove shown in FIG.
A grooved groove shown in (b) is used. Normally, the use section is a groove-shaped bevel in which only the end of the skin plate 2 of the horizontal plate shown in FIG. 3B is processed up to a plate thickness of about 40 mm. , FIG. 3 (a)
The Y-shaped groove in which both ends of the horizontal skin plate 2 and the vertical skin plate 1 shown in FIG.

[0004] In the temporary assembling of the box column before the submerged arc welding, the separation of the skin plates 1 and 2 from the backing metal 4 due to the thermal distortion during the submerged arc welding is prevented, so that problems such as hot metal leakage do not occur. Temporary welding with a pitch of about 200 to 250 mm, a bead length of about 50 mm, and a throat thickness of about 7 to 8 mm is performed in the groove by carbon dioxide arc welding or the like.

[0005] After such a temporary assembling step, a method is generally employed in which a square joint is finished in one pass by submerged arc welding of two electrodes up to a plate thickness of about 60 mm. As this welding method, for example, Japanese Unexamined Patent Publication (Kokai) No. 1-241380 discloses a submerged arc welding method for a square joint portion in which a groove shape, a welding condition, a flux composition, and the like are limited and a plate thickness of 40 mm or more is enabled. It has been disclosed. Japanese Patent Application Laid-Open No. 258191/1990 mainly specifies the composition and particle size distribution of the flux, and also limits the welding current and the groove shape to obtain good welding workability and prevent welding defects. Techniques are disclosed.

[0006]

However, even in the welding of the box column joints according to the prior art described above, there is no welding defect, and the welding portion is actually repaired. One of the welding defects generated in box-column joint welding by submerged arc welding is a penetration defect in which the weld metal 6 does not reach the thickness of the skin plate 2 shown in FIG. 4 and a sufficient penetration P cannot be obtained. is there.

[0007] Penetration P is inspected by ultrasonic flaw detection, but penetration P of about 3 mm or less is determined as a defect in consideration of inspection accuracy and may be repaired.
Further, as a serious welding defect, there is a hot crack generated at a central portion of a weld bead cross section. When the penetration P becomes excessive, the hot cracking occurs when the solidification direction of the weld metal becomes nearly horizontal toward the center of the bead, and occurs in the final solidified portion.

[0008] Repairs when these welding defects occur are as follows:
After removing welding defects by gouging to the deepest part of the weld, multi-layer welding is performed by carbon dioxide arc welding or the like. Such a repair work requires a large number of man-hours due to a large plate thickness, resulting in a significant decrease in work efficiency. For this reason, stabilization of appropriate penetration in box column corner joint welding is an extremely important issue.

An object of the present invention is to provide a submerged arc welding method capable of obtaining a welded portion free from poor penetration in box column corner joint welding and having excellent hot cracking resistance.

[0010]

Means for Solving the Problems The present inventors have intensively studied to obtain a stable penetration by submerged arc welding of a box column joint.

As a result, it has been found that the fluctuation of the penetration P becomes extremely small by performing the sealing welding on the entire line in the groove. Furthermore, as a result of detailed examination of the sealing welding conditions, the method of the present invention was obtained. Here, penetration P of two-electrode submerged arc welding by performing sealing welding
An example of investigating the impact on the environment is described below.

An SM having a thickness of 50 mm indicated by the symbol M1 in Table 1
490B steel is used for skin plates 1 and 2, and FIG.
A Y-shaped groove having a groove angle θ of 35 ° and a root surface R of 2 mm shown in FIG.
The sealing welding in the groove is indicated by the symbol W1 in Table 2.
Using a solid wire having a diameter of 6 mm, at a current of 300 A and a voltage of 35 V, the welding speed is adjusted to variously change the sealing weld bead width, that is, the groove width W of the surface of the sealing weld bead, and a carbon dioxide gas shield at a CO ₂ flow rate of 30 l / min. This was performed by arc welding.

[0013]

[Table 1]

[0014]

[Table 2]

One specimen was prepared for each sealing welding condition, and submerged arc welding was performed using two electrodes. The submerged arc welding is 4.8 m shown in the symbol W2 in Table 2.
The lead wire of the m diameter wire is 6.4 mm of the symbol W3 on the leading pole and the trailing pole.
Using a diameter wire, in combination with the iron powder-containing bond flux shown in Table 3, under the welding conditions shown by the symbol N1 in Table 4,
Pass welding was performed.

[0016]

[Table 3]

[0017]

[Table 4]

After the end of welding, 300 mm of the welding condition unstable portion on the welding start side and 400 mm on the welding end side where the crater portion remains.
from a 1300 mm long weld bead excluding 10 mm
Twelve cross-sectional macro test pieces were taken every 0 mm, and the penetration P
Was measured. As a result, the groove width W of the surface of the sealing weld bead and the wire diameter D of the leading electrode of the submerged arc welding are obtained.
FIG. 1 shows the relationship between the ratio W / D to the maximum value, the minimum value, and the average value of the penetration P (indicated by a circle in the figure).

In the case of W / D = 0 where sealing welding was not performed, the difference between the maximum value and the minimum value of the penetration P, that is, the variation of the penetration P in the same welding bead was 9 mm. On the other hand, by performing the sealing welding, the minimum value of the penetration P increases, and the fluctuation between the maximum value and the minimum value is about half of 4 to 5 m.
m. Further, when W / D = 1.5 or less, the decrease in the average value of penetration P was extremely small, and it was found that there was a good range of W / D for obtaining stable penetration P.

That is, the gist of the present invention is that the angle 4
At the time of welding a Y-shaped groove of 0 ° or less, sealing welding is performed in advance on the entire line in the groove, and the ratio W of the groove width W (mm) of the surface of the sealing weld bead to the wire diameter D (mm) of the leading electrode is obtained. / D is set to 0.4 to 1.5 in a two-electrode submerged arc welding method for a box column joint.

Further, the welding efficiency is improved by performing sealing welding by carbon dioxide shielded arc welding using a flux-cored wire or a solid wire. Note that the sealing welding is to perform welding with a small heat input so that the groove root, that is, the joint portion of the skin plates 1 and 2 does not remain, and to produce a weld bead in which tack welding is continuously performed. .

[0022]

Embodiments of the present invention will be described below in detail. First, the reason why the groove angle is limited to 40 ° or less will be described. As the groove angle increases, deep penetration is easily obtained, but the groove cross-sectional area also increases. Therefore, it is necessary to increase the heat input for welding to obtain the required weld metal. Since the construction with a large welding heat input tends to deteriorate the toughness of the weld metal, the groove angle is set to 40 ° or less.

It should be noted that if the groove angle is small, the welding efficiency is increased, but if the groove is too narrow, it is difficult to obtain deep penetration, and the cross-sectional shape of the bead tends to be thin, so that hot cracking occurs at the center of the cross section of the weld bead. More likely to occur. For this reason, the groove angle is preferably 40 ° or less, and more preferably 25 ° or more.

Next, the sealing weld bead surface width W (m
When the ratio W / D between m) and the wire diameter D (mm) of the lead electrode is less than 0.4, the arc by the lead electrode of the submerged arc welding forming the weld metal at the tip of the penetration is:
Since it occurs below the groove, a deep penetration weld is created, but on the left and right sides of the groove wall, arcs also occur,
Penetration of that part becomes small. Accordingly, a weld bead having a large difference between the maximum value and the minimum value of the penetration is formed. In a deep penetration portion, a high-temperature crack is easily generated at a central portion of a weld bead cross section, but a portion where the penetration is insufficient also occurs.

If the ratio W / D of the surface width W (mm) of the sealing weld bead to the wire diameter D (mm) of the preceding electrode exceeds 1.5, the arc generated by the preceding electrode in the submerged arc welding causes the bead of the sealing welding to fail. Occurs stably between the surface. However, since the throat thickness of the sealing weld bead increases as the bead width increases, penetration tends to decrease, and penetration failure tends to occur.

As the sealing welding method, a covered arc welding method or a gas shielded arc welding method can be considered, but a carbon dioxide gas shielded arc welding method using a flux-cored wire or a solid wire is excellent in welding efficiency.
This is adopted in the present invention.

[0027]

EXAMPLES The effects of the present invention will be more specifically described below with reference to examples. SM having a plate thickness of 60 mm indicated by symbol M2 in Table 1.
490B steel was used for skin plates 1 and 2 and FIG.
A 2000 mm long square joint specimen having a Y-shaped groove with a groove angle of 30 ° and a root surface R of 2 mm shown in FIG.

The sealing welding in the groove is represented by the symbol W in Table 2.
Using a 1.6mm diameter solid wire shown in
The welding was performed by carbon dioxide shielded arc welding at 00 A, a voltage of 30 V, and a CO ₂ flow rate of 30 l / min. The welding speed was adjusted for the width of the sealing weld bead, that is, the groove width W of the surface of the sealing weld bead, and the W / D ratio was changed. Here, when sealing welding is performed by covered arc welding,
The required time was about four times that of carbon dioxide shielded arc welding.

The submerged arc welding is performed by the symbol W3 in Table 2.
The 6.4 mm diameter wire shown in Table 1 was used for the leading electrode and the trailing electrode, and one-pass welding was carried out under the welding conditions shown by the symbol N2 in Table 4 in combination with the iron powder-containing bond flux shown in Table 3. . In addition, as one of the comparative examples, a test body without performing sealing welding was also prepared.

After the completion of the submerged arc welding, a macro test specimen having a cross section of every 100 mm in a 1300 mm long weld bead excluding the 300 mm welding condition unstable part on the welding start side and the 400 mm on the welding end side where the crater remains remains. Twelve pieces were sampled, and the crack resistance was evaluated, that is, the presence or absence of hot cracks generated at the center of the weld bead cross section and the penetration P were measured.

The results are shown in Table 5. The ratio W / D between the groove width of the surface of the sealing weld bead, which is a requirement of the present invention, and the diameter of the leading electrode wire in submerged arc welding is 0.4 to 1%. No. 5 within the range of welding No. 1 to No. 5
No hot cracking occurred and sufficient penetration was obtained.

[0032]

[Table 5]

However, welding no. No. 6 shows a case where sealing welding was not performed, in which the difference between the maximum value and the minimum value of the penetration was large, and hot cracking occurred in the weld portion where the penetration was large. Welding No. In No. 7, since the groove width of the sealing weld bead surface is small, W / D = 0.2, the difference between the maximum value and the minimum value of penetration is large, and hot cracking occurs at the weld portion where penetration is large. There has occurred. Welding No. 8 is
W / D with large groove width of sealing weld bead surface =
Since it was 1.5, poor penetration occurred.

[0034]

As described above, according to the welding method of the present invention, it is possible to obtain a sound weld having no penetration defect and excellent hot cracking resistance. Highly efficient production becomes possible.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between a penetration W and a ratio W / D between a sealing weld bead surface width and a lead electrode wire diameter.

FIG. 2 is a view showing the shape of a box column.

3A and 3B are views showing a groove shape, wherein FIG. 3A shows a Y-shaped groove, and FIG.
Is a groove.

FIG. 4 is a diagram showing a cross-sectional macro shape of a weld bead and sealing welding, and corresponds to the groove in FIG. 3 (a).

[Explanation of symbols]

 1, 2 ---- Skin plate 3--Diaphragm 4--Back metal 5--Sealing weld bead 6 ---- Weld metal θ ---- Groove angle d ---- Groove depth R- −−Root surface W −−− Sealing weld bead surface width P −−− Penetration

Claims (2)

[Claims] When welding a Y-shaped groove having an angle of 40 ° or less, sealing welding is performed in advance on the entire groove, and the groove width W (mm) of the surface of the sealing weld bead and the wire diameter D ( mm) with a ratio W / D of 0.4 to 1.5. 2. The two-electrode submerged arc welding method for a box column joint according to claim 1, wherein the sealing welding is performed by carbon dioxide shielded arc welding using a flux-cored wire or a solid wire.