JP2010253508A - Arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arc welding method capable of preventing galvanization cracking during galvanizing and manufacturing a structure with high quality in a steel structure to which hot dip galvanizing is applied. <P>SOLUTION: Multi-layer welding equal to or more than two layers/two passes is carried out when assembling the structure 30 by welding before the hot dip galvanizing. The welding pass B of the last layer of the multi-layer welding is laminated so as to temper a welded heat-affected zone H caused at a member with a side to be prevented from hot dip galvanization cracking by welding A executed before the last layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an arc welding method which is a main welding method when manufacturing a large steel structure such as a steel tower, a bridge, and a steel frame, and in particular, plating at the time of plating of a structure to be hot dip galvanized. The present invention relates to an arc welding method suitable for preventing cracking.

Hot dip galvanizing is widely used for large steel structures such as steel towers, bridges, and steel frames because it has excellent corrosion resistance and can be made maintenance-free.
However, it is known that in these large steel structures, cracking of the steel material due to plating occurs during hot dip galvanization (called plating cracking). For example, as shown in FIGS. 4 to 6, a stiffener mounting portion 10 for a steel tower steel pipe (see FIG. 4), a horizontal stiffener mounting portion 20 for a bridge plate girder (see FIG. 5), or a steel column-beam joint portion. In the scallop 33 edge portion (see FIG. 6) of 30 or the like, stress concentration due to the shape of the weld toe portion or deterioration of the material due to the thermal effect of welding occurs, and plating cracks are likely to occur.

For example, as shown in FIG. 7, in the welding of the column 31 and the web 32 of the beam 36 in the conventional column-beam junction 30, fillet welding is started from the scallop 33 on one end side, and the scallop 33 on the other end side is started. Until the end of the scallop 33 is turned.
In this case, in addition to the occurrence of tensile residual stress at the rotating weld toe at the end of the scallop 33, stress concentration is likely to occur due to irregular bead shape, and the heat affected zone (HAZ) H Due to curing, the ductility decreases. And when molten zinc is in contact with the steel material, when tensile stress (welding residual stress and thermal stress at the time of plating) acts on the steel material, zinc penetrates into the grain boundaries of the steel material, causing molten metal embrittlement. Therefore, it is considered that plating cracks are likely to occur.

  Therefore, as a measure for preventing such plating cracks, for example, Patent Documents 1 and 2 propose high-tensile steels having excellent plating cracking properties by controlling the steel plate composition and structure to a predetermined level.

JP-A-9-291338 JP-A-8-158005

  However, generally, plating cracks tend to occur more easily as the structure becomes larger and stronger. In particular, in recent years, as the above-described structures are further increased in size and strength, plating cracks tend to easily occur, which is a big problem. In other words, plating cracks in steel structures that tend to become larger and stronger in the future can be completely prevented only by measures for controlling the steel plate composition and structure as described in Patent Documents 1 and 2. Is difficult. Further, the measures for controlling the steel plate composition and structure as described in Patent Documents 1 and 2 may deteriorate various properties of the steel plate such as weldability and rigidity, and there is a disadvantage that the use of the steel plate is limited. is there.

  Therefore, the present invention has been made paying attention to such problems, and prevents arc cracks that occur in the welded part during plating, and can produce a steel structure with high quality. It is an object to provide a welding method.

  In order to solve the above-mentioned problems, the present inventors have intensively studied about the plating cracking and the arc welding conditions of the portion where the above-described plating crack is likely to occur. As a result, when arc welding is performed on a steel structure to be hot dip galvanized prior to hot dip galvanization, the welding laminating method is set to two or more passes, and by the final layer welding pass, it is made before the final layer. By adopting a laminating method in which the weld heat-affected zone generated in the member on the side that is intended to prevent hot-dip galvanized cracking by tempering is tempered (tempered), it is in the vicinity of the weld toe during plating. It has been found that plating cracks that occur can be prevented. In addition, the present inventors can stably prevent plating cracking if the bead length of the welding pass of the final layer is 10 mm or more and 100 mm or less, and the steel structure can be stably manufactured at high quality and at low cost. And found that it is more preferable in manufacturing.

  That is, the present invention is a method of performing arc welding on a steel structure subjected to hot dip galvanizing, and when assembling a steel structure by welding prior to the hot dip galvanizing, welding of two layers or more passes. Lamination is performed, and the welding pass of the final layer of the weld lamination is to temper the weld heat-affected zone generated in the member on the side that is intended to prevent hot dip galvanizing cracking by welding performed before the final layer. It is characterized by being laminated.

  ADVANTAGE OF THE INVENTION According to this invention, the plating crack which generate | occur | produces in the welding part of steel structures at the time of hot dip galvanization construction can be prevented stably, and a steel structure can be manufactured with high quality.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining one Embodiment of the steel structure to which the arc welding method of this invention is applied, The figure (a) is a figure of the state which gave the 1st welding among the welding lamination, b) is a view showing a state in which the welding pass of the final layer is applied to one scallop end, and FIG. 10C is a ZZ cross-sectional view in FIG. It is a figure explaining one Embodiment at the time of applying the arc welding method of the present invention to a bridge plate girder, the figure (a) is the front view, and the figure (b) is Y in the figure (a). It is -Y sectional drawing. It is a figure explaining one Example at the time of applying the arc welding method of this invention to a column-beam welding part, The figure (a) is the front view, The figure (b) is a top view. It is a figure explaining an example of the structure made from steel which performs hot dip galvanization. It is a figure explaining an example of the structure made from steel which performs hot dip galvanization. It is a figure explaining an example of the structure made from steel which performs hot dip galvanization. It is a figure explaining an example of the steel structure which applied the conventional arc welding method, The figure (a) is a figure of the state which gave the conventional welding, The figure (b) is the figure (a) It is XX sectional drawing in).

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. FIG. 1 is a view for explaining an embodiment of a steel structure to which the arc welding method of the present invention is applied. In addition, the example shown to the figure is an example which welds the pillar and the web of a beam in the pillar-beam junction part which consists of steel frames as a steel structure to which hot dip galvanization is performed, and FIG. The figure of the state which gave the welding of the 1st layer among welding lamination, the figure (b) is the figure of the state where the welding pass of the last layer was given to one scallop end, and the figure (c) is the figure ( It is ZZ sectional drawing in b).

  As shown in FIG. 1, in the arc welding method of the present invention, two or more layers are welded and laminated (in this example, two layers and two passes are welded and laminated). That is, as shown in FIG. 5A, the first-pass welding path A starts fillet welding from the end of the scallop 33 on one end side and continuously welds to the end of the scallop 33 on the other end side. To do. The end portion of the scallop 33 is turn welded. Next, as shown in FIG. 4B, the weld galvanizing crack is attempted to be prevented by the welding performed before the final layer (in this example, the first welding pass A) by the welding pass B of the final layer. Lamination is performed so that the weld heat affected zone H generated in the side member is tempered. At this time, the arrangement of the temper bead B, which is the welding of the final layer, is a position where the welding heat affected zone H by the welding path A welded before the final layer is tempered. Thereby, hardening and ductility fall of welding heat affected zone H can be controlled, and plating cracking can be prevented.

  More specifically, in the arc welding method of the present invention, as shown in FIG. 2B, the bead length W1 of the temper bead B of the final layer is 10 mm or more and 100 mm at a portion where the plating crack is likely to occur. The following is preferable. This is because if the bead length W1 of the temper bead B is less than 10 mm, it is difficult to obtain a stable bead and a weld defect is likely to occur. On the other hand, if the bead length W1 of the temper bead B exceeds 100 mm, the weld heat affected zone H where the plating crack is not likely to occur is also tempered, which is disadvantageous in terms of manufacturing efficiency of the structure and cost. Because it becomes.

  Further, it is preferable that the temper bead B is placed so that the toe portion of the temper bead B is located within 4 mm from the toe portion of the welding pass A, as indicated by reference numeral W2 in FIG. In this example, since plating cracks are likely to occur near the periphery of the scallop 33 of the web 32, the temper bead B of the final layer needs to be located at the position near the surface of the welding heat affected zone H on the web 32 side. .

  Here, for example, in the case of a bridge plate girder, plating cracking is likely to occur on the side of the stomach plate. Therefore, in the case of a bridge plate girder, as illustrated in FIG. 2, it is necessary to place a temper bead B as a final layer so that the vicinity of the surface of the welding heat affected zone H on the abdomen plate 22 side is tempered. Note that the temper bead B is not limited to one pass, and a plurality of passes may be performed so as to temper all the weld heat affected zones H where plating cracking is likely to occur, if necessary.

Next, an embodiment of the present invention will be described with reference to the drawings as appropriate.
The test body in this example is a column-beam joint 30 made of a steel frame having the shape shown in FIG. 3, and the column 31 uses a BCR295 material of □ -450 × 450 × 22. No. 36 uses SN490B material of H-section steel 800 × 350 × 16 × 32. And the manufacturing conditions of this column-beam welding part 30 were changed as shown in the following Table 1, and eight test bodies were manufactured, respectively.

  In the example of the present invention, as shown in FIG. 1 described above, after the fillet welding of the column 31 and the web 32 of the beam 36 is performed, the temper bead B is welded to the column 31 side in the vicinity of the scallop 33, What changed the welding length of the bead B to 6-150 mm (No. 2-6 of Table 1) was prepared. In addition, as a comparative example, one without temper bead B (No. 1 in Table 1) and one with temper bead B applied to the web 32 side of beam 36 (No. 7 and 8 in Table 1) are prepared. did.

Thereafter, hot dip galvanization was performed on each test specimen at an immersion speed of 2.0 m / min and a plating bath temperature of 450 ° C., and the occurrence of plating cracks in the vicinity of the weld toe of the scallop 33 was evaluated.
As a result, as shown in Table 1, all of the test bodies of the present invention examples (Nos. 2 to 6 in the same table) have a lower plating crack occurrence frequency than the comparative examples, and may cause plating cracks. It was confirmed that the welding method was suitable for high-quality steel frame production. In particular, a temper bead with a weld length of 10 to 100 mm. It was confirmed that the specimens 3, 4, and 5 had a low possibility of plating cracking and were good. On the other hand, the comparative example which deviates from the scope of the present invention has a high possibility of occurrence of plating cracks, and it was confirmed that the quality of the manufactured steel frame is lower than that of the present invention example.

  Here, in these embodiments, the portion where the plating crack is likely to occur is near the periphery of the scallop 33 of the web 32 of the beam 36. In contrast, in the comparative example, the temper bead B is applied to the web 32 side of the beam 36 (Nos. 7 and 8 in the table), the new weld heat affected zone H is added to the web 32 of the beam 36. Since the temper is not applied to the weld heat affected zone H of the member for which it is desired to prevent plating cracking, it is considered that there was no effect of preventing plating cracking. As described above, if any of the welding lamination method, the bead length of the temper bead B, and the position of the temper bead B is out of the preferred range of the present invention, plating cracks are likely to occur, and the quality of the manufactured steel frame is It was confirmed that it was lower than that of the inventive example.

  In addition, the arc welding method of the steel structure according to the present invention is not limited to the above-described embodiments or examples, but includes plating cracks such as steel towers, bridges, and the examples shown in FIGS. It can also be applied to the welding of a part that is likely to generate a crack. On the other hand, for the portion where the plating crack is difficult to occur, for example, the conventional normal welding method shown in FIG. 7 is used to reduce the cost of manufacturing the steel structure and to increase the efficiency of the welding work. Is desirable.

10 Stiffener attachment (steel structure for hot dip galvanizing)
DESCRIPTION OF SYMBOLS 11 Steel pipe 12 Forged flange 13 Stiffener 14 Gazette plate 15 Plane plate 20 Horizontal stiffener attachment part (steel structure to which hot dip galvanization is applied)
21 Flange 22 Abdominal plate 23 Vertical stiffener 24 Horizontal stiffener 30 Column-beam joint (steel structure to which hot dip galvanization is applied)
31 Column 32 Web 33 Scallop 34 Flange 35 Diaphragm 36 Beam A First layer welding (when welding with three or more layers, welding from the first layer to the last layer)
B Temperbead (welding the final layer)
C Plating crack H Weld heat affected zone

Claims (2)

A method of arc welding a steel structure to be hot dip galvanized,
Prior to the hot dip galvanization, when the structure is assembled by welding, two layers or two passes are welded and the final layer of the welded layers is welded before the final layer. An arc welding method characterized by laminating so as to temper a welding heat-affected zone generated in a member on the side to be prevented from hot-dip galvanizing cracking.   The arc welding method according to claim 1, wherein a bead length of a welding pass of the final layer is 10 mm or more and 100 mm or less.

Images