JPH10211578A - Two-electrode submerged arc welding method for square joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform bead shape and a sound weld zone over the whole length of a weld line by inclining the object to be welded into the specified angle or less so as to become descending slope welding and specifying the inclined angle of a preceding electrode and the inclined angle of a succeeding electrode. SOLUTION: The excessive penetration and depth are prevented, the too small bead depth is avoided and the crack due to high temperature and the groove incomplete fusion are hardly generated by inclining the object A to be welded into 3 deg. or less so as to become a descending slope. The inclined angle θL of the preceding electrode L is specified to be the sweepback angle of 15 deg.-35 deg.. When θL is less than 15 deg., since the action pushing the molten metal and molten slag backward by the arc of the preceding electrode L is insufficient and the molten metal and molten slag flow into just under the arc, slag inclusive is generated and the lack of uniformity on the bead depth and the height of reinforcement of weld are generated. The inclined angle θT is specified to be the sweepback angle of 10 deg.-30 deg.. When θT is less than 10 deg., the excessive bead width and the insufficient height of reinforcement of weld are not dissolved.

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 a column member of a building structure, and more particularly, to a high-efficiency method for obtaining a sound weld in a square joint welding of a box column having a thickness of more than 50 mm. Submerged arc welding method.

[0002]

2. Description of the Related Art With the height of buildings in recent years, steel materials used for box pillars, which are pillar members thereof, are becoming increasingly thick. As shown in FIGS. 2 (a) and 2 (b), the shape of the box pillar is such that four skin plates 1 and 2 are assembled in a box shape, and a diaphragm 3 as a reinforcing material is provided inside a connection portion for attaching a beam. Installed.

[0003] The manufacture of box pillars is made up of skin plates 1,
The joining portion of the two, that is, the four corners of the box are welded to form a hollow pillar. The groove shape of this square joint portion is as follows. In the case of a thick plate having a plate thickness exceeding 50 mm, both ends of the skin plate 2 of the horizontal plate and the skin plate 1 of the vertical plate shown in FIG. The mold groove is adopted. As a highly efficient welding method for such a box column corner joint, a method of finishing in one pass by submerged arc welding of two electrodes is generally adopted. As this welding method, for example, in Japanese Patent Publication No. Hei 6-30818, when the plate thickness is 40 mm or more,
Assuming that the workpiece to be welded has an ascending slope and a descending slope due to welding heat distortion, a groove arc welding method for a corner joint with a limited groove shape, welding conditions and electrode inclination angle is disclosed. I have.

[0004]

However, the box column corner joint 1 having a particularly large thickness in submerged arc welding.
In large-pass heat input welding, the angle of inclination of the workpiece greatly affects the bead appearance. Particularly in the manufacture of a long column of up to 12 m, in which the ascending and descending slopes are continuously welded at a large angle, the bead width and the extra height of the first half and the second half of the welding are adjusted by the same welding conditions. It is difficult to make it uniform.

[0005] That is, in the welding of the box column corner joint, it is general that the upper two corner joints shown in FIG. 2 (a) are simultaneously welded. The central part rises like a bow. Therefore, the first half of the welding is ascending welding, and the bead shape is small as shown in FIG.
And the center in the bead width direction tends to be triangular. On the other hand, the latter half of the welding was down welding,
As shown in (c), the bead width W tends to be large and the extra height H at the center of the bead tends to be small, contrary to the upward welding.

As described above, the bead appearances in the first half and the second half of welding may differ greatly. At that time, if the excess height H is excessively large in the first half of the weld bead or the bead width W is small, high temperature crack 6 is likely to occur in the center of the weld metal.
In the latter half, the bead width W is large and the margin height H is insufficient and the penetration 7 is liable to occur.

[0007] For these excess or deficiency, it is necessary to rework grinding and repair welding. Further, when high temperature cracking or insufficient penetration occurs, the weld metal is removed to the deepest part of the skin plate by, for example, arc air gouging, and then multi-layer welding is performed by CO ₂ shield welding or the like. The man-hours required for such reworking work is large due to the large thickness of the plate, resulting in a decrease in efficiency. This is an extremely important task for welding a long box-column joint.

An object of the present invention is to provide a highly efficient submerged arc welding method for obtaining a uniform bead shape and a healthy weld over the entire length of a welding line in box column corner joint welding of a thick steel plate. .

[0009]

That is, the gist of the present invention is to provide a two-electrode submerged arc welding method for a square joint, in which a workpiece is inclined at an angle of 3 ° or less so as to perform downward inclination welding, and a leading electrode is formed. Angle of inclination θ _L from 15 ° to 35
The present invention provides a submerged arc welding method for a square joint, wherein a receding angle of ゜ and an inclination angle θ _T of a trailing electrode are set to an inclination angle of 10 ° to 30 °.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below together with the operation. FIG. 1 is a schematic diagram showing the welding method of the present invention. In the present invention, it is necessary to incline and weld the workpiece A so as to be a downward inclined welding. When the workpiece A rises and becomes the inclined welding, the molten metal flows backward in the welding traveling direction V, so that the arc generating point by the leading electrode L is located at the bottom of the groove, and the penetration depth P is increased.

However, as the arcing point of the leading electrode L becomes deeper, the position of the molten metal by the leading electrode L at the arcing point of the trailing electrode T becomes deeper. An arc of T also occurs. Therefore, the bead width W is reduced. As a result, the bead width becomes smaller with respect to the penetration depth, so that high-temperature cracks 6 are generated in the central portion of the weld metal and groove fusion defects 9 on the surface of the steel sheet are more likely to occur.

As a countermeasure, it is possible to prevent the penetration depth in the upward inclined welding from becoming excessive.
For example, if the current value of the leading electrode L is reduced, the penetration is reduced but the amount of weld metal is also reduced. Therefore, the arc generation point of the trailing electrode T is located at a deep groove, and the groove fusion defect 9 is reduced. Or high temperature cracks 6 occur at the center of the bead.

However, by inclining the workpiece A at 3 ° or less so as to have a downward inclination, an excessive penetration depth or an excessively small bead width can be prevented, and high temperature cracking and groove fusion failure can be prevented. Defects are less likely to occur. To the effect of these defects prevent those clear, the inclination angle theta _A of the weld object A is preferably set to 0.3 ° or more.

Further, when the inclination angle theta _A of the weld object A is more than 3 °, the molten metal and molten slag flows into the arc generation point of the leading electrode L, most groove for an arc is generated on the molten metal The lower part cannot be melted deeply, resulting in insufficient penetration 7. Further, since the molten slag having poor electrical conductivity has an unstable arc generation state, slag entrainment 8 is generated, and the bead width and the extra height are uneven.

In order to prevent insufficient penetration during sloping welding, slag entrainment, or a tendency for bead width or extra height to be non-uniform, the electrode inclination is set to a receding angle for both the leading and trailing electrodes. There is a need.

First, the inclination angle θ _L of the leading electrode L needs to be a receding angle of 15 ° to 35 °. When θ _L is less than 15 °, the action of pushing back the molten metal or molten slag by the arc of the leading electrode L is insufficient, and the molten metal or molten slag flows directly below the arc, causing slag entrainment or beads. Non-uniformities in width and extra height occur. Further, in the case of the receding angle in which θ _L exceeds 35 °, the penetration depth becomes too large, so that high-temperature cracking is likely to occur.

It is necessary to set the inclination angle θ _T of the trailing electrode to a receding angle of 10 ° to 30 °. If θ _T is less than 10 °, an excessively large bead width or insufficient shortage height due to performing the downward inclination welding cannot be solved. However, θ _T is 3
If it exceeds 0 °, the penetration by the subsequent electrode T becomes large, so that the bead width becomes small, and defects such as high-temperature cracking and groove fusion defect on the steel sheet surface are likely to occur.

Here, the receding angles θ _L and θ _T represent the angle between the vertical line and the respective electrodes L and T, and the receding angles 0 _L and θ _T
゜ is a vertical line. Note that the leading electrode inclination angle θ _L is set to an angle that is about 10 ° larger than the following electrode inclination angle θ _T so that there is no interference in the arrangement of the power cable attached to the electrode nozzle or the wire feed motor. I do. However, by using a curved electrode nozzle, θ _L and θ _T
Can be substantially the same angle.

The flux to be used may be a commercial product (for example, type FS-BT1 of JIS Z3352) applied to welding for finishing a box column corner joint in one pass for large heat input welding.

[0020]

The present invention will be described in more detail with reference to the following examples. The welding material used was a bond flux containing iron powder (JIS Z 335) having a particle size of 12 × 100 mesh shown in Table 1.
2 FS-BT1), a wire having a diameter of 6.4 mm shown in Table 2 was used, and the steel plate was a SM490B steel having a thickness of 60 mm shown in Table 3 and a groove angle θ _B = 30 ° shown in FIG. It was processed into a 2 mm groove shape. The length of this specimen is 1
It was 500 mm. Using the welding conditions shown in Table 4, the inclination angle and the electrode inclination angle of the workpiece (specimen) shown in Table 5 were 2
Submerged arc welding with electrodes was performed.

After welding, the presence of internal defects was examined by evaluating the appearance of the bead and ultrasonic inspection. From the spot where the defect was found by the ultrasonic inspection, a macro test piece of a cross section was prepared and observed, and the type of the defect was confirmed. Table 5 shows the results.

In the welding No. of the present invention, In Nos. 1 to 6, since the inclination angle of the workpiece, the inclination angle of the leading electrode, and the inclination angle of the trailing electrode were appropriate, a good bead appearance was obtained, and there was no defect in the weld metal by ultrasonic inspection. .

In the comparative examples, No. No. 7 is a triangle bead having a small bead width and a large margin because of ascending welding, and a high temperature crack was also generated at the center of the bead. No. In Sample No. 8, the arc was unstable due to the small receding angle θ _L of the preceding electrode, the bead width and the height of the overfill were not uniform, and slag was involved. No. In No. 9, since the sweepback angle θ _L of the preceding electrode was large, the penetration was large, and high-temperature cracking occurred at the center of the bead.

No. 10, since receding angle theta _T of the trailing electrodes is small, the bead width is too large weld reinforcement height is insufficient. N
o. 11, since the receding angle theta _T of the trailing electrodes is larger groove incomplete fusion occurs and the high temperature cracking also occurred in the bead center. Thus, the comparative example No. In Nos. 7 to 11, various defects that required repair welding occurred, and none were satisfactory.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

According to the two-electrode submerged arc welding method for a square joint of the present invention, in a square joint welding of a box column having a plate thickness of more than 50 mm, it is possible to perform a highly efficient welding of a healthy weld. The effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a welding method of the present invention.

FIGS. 2A and 2B are a front view and a side view of a box pillar, respectively.

FIG. 3 is a view showing a groove shape.

FIGS. 4 (a), (b), (c), and (d) are diagrams showing a cross-sectional macro shape and a defect of a weld bead.

[Explanation of symbols]

1: Skin plate 3: Diaphragm 4: Backing metal 5: Weld metal 6: High temperature crack 7: Insufficient penetration 8: Slag inclusion 9: Poor groove fusion R: Root face P: Penetration W: Bead width H: excess metal height L: leading electrode T: trailing electrode V: welding direction theta _A: weld object inclination angle theta _L: leading electrode inclination angle theta _T: trailing electrode inclination angle theta _B: included angle

Claims (1)

[Claims] In a two-electrode submerged arc welding method for a square joint, an object to be welded is inclined to 3 ° or less so as to perform downward inclination welding, and the inclination angle θ _L of the leading electrode is set to a receding angle of 15 ° to 35 °; A submerged arc welding method for a square joint, wherein the inclination angle [theta] _T of the trailing electrode is set to a receding angle of 10 to 30 [deg.].