JP6031227B2 - Welding method - Google Patents

Description

  The present invention relates to a laser welding method, and more particularly, to a technique for improving welding quality by laser welding.

In the field of steel structures such as shipbuilding and bridges, butt joint welding and corner joint welding, in which multiple steel sheets are integrated by abutting the edges of steel sheets, are often used to produce large steel structures. Is possible.
In recent years, in such butt joint welding and corner joint welding, laser welding using a laser beam tends to be employed instead of arc welding. Recently, laser arc hybrid welding in which arc welding and laser welding are combined has been developed.
By the way, when performing keyhole type welding on a joint by laser welding, there is a problem that defects called porosity are easily generated, and the weld quality of the joint is impaired.

Therefore, for example, a laser welding method has been conceived in which the flow of molten metal is controlled by modulating the laser output with a frequency or a waveform to suppress the generation of porosity (see Patent Document 1).
Further, for example, when 30% or more of the weld metal is occupied by an austenite structure, a technique for suppressing the generation of porosity by adjusting the chemical component is also considered (see Patent Document 2).

JP 2002-273586 A Japanese Patent No. 3912491

However, when an experiment was performed by modulating the laser output based on the laser welding method disclosed in Patent Document 1, it was confirmed that it was difficult to completely suppress the generation of porosity. In particular, in laser arc hybrid welding, it was confirmed that the arc pulse becomes a disturbance and the generation of porosity cannot be suppressed.
The technique disclosed in Patent Document 2 cannot be applied to carbon steel (structural steel JIS G 3101) that is generally used in large steel structures such as bridges.

On the other hand, studies have shown that porosity is very likely to occur after the second pass (second layer) of non-through welding, particularly multilayer welding.
From this, when multi-layer welding is performed by laser welding or laser arc hybrid welding, how to prevent the generation of porosity becomes a problem.
The present invention has been made to solve such problems, and an object of the present invention is to provide a laser welding method capable of preventing the occurrence of porosity when performing multilayer welding.

To achieve the above object, a method of welding according to claim 1, laser welding welding between more metal member thickness 25 mm, intends rows multilayer welding of three or more layers by arc welding and laser arc hybrid welding a welding method, in the first layer, the laser beam of the converging diameter smaller than the threshold keyhole laser welding of the value corresponding to the value and the thermal conductivity type laser welding corresponding to keyhole laser welding In the final layer, only the arc welding is performed, and in the layer between the first layer and the final layer, the arc is adapted to the heat conduction laser welding in which the focused diameter is larger than the threshold value. It is characterized by performing welding.

According to welding method according to claim 1, the heat conduction type made larger than the threshold value with the value corresponding to the value and the thermal conductivity type laser welding to the corresponding light condensing diameter in keyhole-type laser welding at the second and subsequent layers Since laser welding is performed, it is possible to prevent the occurrence of porosity when performing multilayer welding.

Further, according to the welding method according to claim 1, since the second and subsequent layers to perform the arc welding with heat conduction type laser welding, to ensure that to prevent the occurrence of porosity in the case of performing the multi-layer welding it can.

It shows a state where a laser arc hybrid welding apparatus applied to engagement Ru welding method according to the present invention is carried out the welding of the first layer (a), of the member to be welded along the line A-A of (a) It is a figure (c) which shows a welding section of a weld metal formed by welding of the 1st layer which meets a BB line of sectional views (b) and (a). The figure which shows a laser arc hybrid welding apparatus in the state which is welding the 2nd layer (a), The welding cross section of the weld metal formed by the 2nd layer welding along CC line of (a) FIG. 2B is a diagram showing a weld cross section of a weld metal when only heat conduction type laser welding is performed in the second layer. It is a figure which shows the welding result of the reference example 1 as an actual welding cross section. It is a figure which shows the welding result of the comparative example 1 as an actual welding cross section. It is a figure which shows the welding result of Example 1 as an actual welding cross section.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In FIG. 1 (a), is shown with the laser arc hybrid welding apparatus applied to engagement Ru welding method according to the present invention is performing the welding of the first layer.
As shown in the figure, the laser arc hybrid welding apparatus 1 is composed of an arc welding apparatus 10 and a laser welding apparatus 20.

Specifically, the arc welding apparatus 10 is configured so that the welding wire 14 is fed obliquely from the tip of the welding torch 12 to the welded portions (grooves) of the members to be welded S and S. In the first layer welding shown in FIG. 1A, arc welding is not performed as will be described later, so the arc welding apparatus 10 is in a retracted state without performing welding.
On the other hand, the laser welding apparatus 20 is configured so that a laser beam LB supplied from a laser generator (not shown) is condensed by a laser irradiation head 22 and irradiated to the welded portions (grooves) of the welded members S and S. Has been. Here, the laser irradiation head 22 can appropriately adjust the condensed diameter of the laser beam LB.

The welded members S, S are steel plates made of metal members (for example, carbon steel), and as shown in FIG. 1A, the end of one welded member S is the other welded member S. Forming a groove with a root portion as shown in FIG. 1 (b), which shows a cross-section of the welded members S and S along the line AA in FIG. 1 (a). In this way, the welded portion is configured. The groove angle of the mold groove is, for example, 30 °.
In the laser arc hybrid welding apparatus 1 configured as described above, the welded members S, S are welded lines of the welded portions of the welded members S, S are the tip of the welding wire 14 and the focal point of the laser beam LB. Is set along the line connecting

And when welding the 1st layer, it sends to the arrow direction in a figure, and only the laser welding is performed with respect to the root part of a lathe groove | channel by the laser welding apparatus 20. FIG. At this time, the laser irradiation head 22 of the laser welding apparatus 20 has a condensing diameter of the laser beam LB smaller than a threshold value between a value corresponding to keyhole type laser welding and a value corresponding to heat conduction type laser welding at the welded portion. Adjusted to be. That is, keyhole type laser welding is performed in the first layer welding.
Referring to FIG. 1C, the weld metal W formed by welding the first layer is shown as a weld cross section along line BB in FIG. Then, as shown in the figure, welding is performed so that a back wave is formed in the root portion by keyhole type laser welding.

FIG. 2 (a) shows the laser arc hybrid welding apparatus 1 in a state where the second layer is being welded.
When the second layer is welded, welding is performed in the order of arc welding and laser welding in the direction of the arrow in the figure. At this time, the laser irradiation head 22 of the laser welding apparatus 20 uses, for example, as shown in FIG. It is adjusted to be larger than the threshold value with the corresponding value. That is, in the second layer welding, heat conduction type laser welding is performed.
Referring to FIG. 2 (b), the weld metal W formed by the second layer welding is shown as a weld cross section along line CC in FIG. 2 (a). Then, as shown in the figure, the weld metal W is formed by superimposing the second layer on the first layer by arc welding and heat conduction type laser welding.

As described above, when heat conduction laser welding is performed together with arc welding in the second layer, the weld metal W is flattened without any hot cracking and formed well in the mold groove as shown in FIG. 2 (b). In addition, the generation of porosity is reliably suppressed. Thereby, the welding quality of the joint can be sufficiently ensured.
In addition, although the 2nd layer is demonstrated here, generation | occurrence | production of a porosity is also suppressed by implementing heat conduction type | mold laser welding with arc welding also after the 3rd layer. That is, the generation of porosity can be suitably suppressed by making the second and subsequent layers of laser welding heat conductive laser welding.

  Here, arc welding is carried out together with heat conduction type laser welding in the second layer, so that the generation of porosity can be reliably suppressed, but arc welding is performed in the second layer and thereafter. Only heat conduction type laser welding may be performed without carrying out, and even in this case, generation of porosity can be suppressed. That is, referring to FIG. 2C, a cross section in the case where only the heat conduction type laser welding is performed without performing arc welding in the second layer is shown corresponding to FIG. In addition, the weld metal W is flattened and formed satisfactorily without any hot cracking in the lip groove, and the generation of porosity is suppressed.

[ Reference Example 1]
As the members to be welded S and S, carbon steel (SS400) having a plate thickness of 12 mm was prepared. In these members to be welded S, S, as shown in FIG. 1 (b), the welded portion is configured so as to form a lathe groove having a root portion.
As the arc welding apparatus 10, an arc power source (DP350 manufactured by Daihen Co., Ltd.) and a welding wire (MG-S50 manufactured by Kobe Steel) were used, the protruding length of the welding wire was 20 mm, and the torch angle of the welding torch was 60 °.

As the laser welding apparatus 20, a laser generator (7 kW fiber laser manufactured by IPG) was used.
The distance between the arc welding weld and the laser welding weld was 3 mm.
And about the 1st layer, only keyhole type laser welding was performed. For the second layer, heat conduction laser welding and arc welding were performed. The welding conditions at this time are as follows.

-First layer welding conditions Laser power: 5kW, welding speed: 1m / min, defocusing distance: 0mm
-Second layer welding conditions Laser power: 4kW, welding speed: 0.8m / min, defocus distance: + 40mm, arc current: 250A
Here, the defocusing distance is the distance from the welded portion to the focal point of the laser beam LB, and the defocusing distance of 0 mm indicates the case where the focal point of the laser beam LB coincides with the welded portion and the condensing diameter is minimum. It is shown that the focal point of the laser beam LB moves away from the welded portion and the condensing diameter increases as the defocusing distance increases. For example, the threshold value between the value corresponding to the keyhole type laser welding of the condensing diameter and the value corresponding to the heat conduction type laser welding corresponds to the defocus distance of 40 mm when the condensing diameter is 3 mm, for example.

FIG. 3 shows an actual weld cross section as a result of welding the welded members S and S under such welding conditions.
As shown in the figure, the keyhole type laser welding is performed on the first layer, and the heat conduction type laser welding is performed together with the arc welding on the second layer, so that the weld metal W is heated at a high temperature in the mold groove. It can be seen that it is flat and well formed without cracks and no porosity is generated.

[Comparative Example 1]
In Comparative Example 1, with respect to Reference Example 1, the defocus distance in the second layer welding conditions was set to 0 mm as in the first layer welding conditions.
That is, only the keyhole type laser welding was performed for the first layer, and the keyhole type laser welding and arc welding were performed for the second layer instead of the heat conduction type laser welding.

FIG. 4 shows the result of welding the welded members S and S under such welding conditions as an actual weld cross section.
As shown in the figure, it can be seen that porosity occurs in the second layer as well as the first layer by performing keyhole laser welding. If porosity is generated in this way, the weld quality of the joint is impaired, which is not preferable.

[Example 1 ]
As the members to be welded S and S, carbon steel (SS400) having a plate thickness of 25 mm was prepared. In these members to be welded S, S, as shown in FIG. 1 (b), the welded portion is configured so as to form a lathe groove having a root portion.
And since the to-be-welded members S and S are as thick as 25 mm, here welding was performed with five layers from the first layer to the fifth layer.
For the first layer, only keyhole type laser welding was performed. About the 2nd layer-the 4th layer, heat conduction type laser welding and arc welding were performed. For the fifth layer, only arc welding was performed. The welding conditions at this time are as follows.

-First layer welding conditions Laser power: 7kW, welding speed: 0.8m / min, defocusing distance: 0mm
2nd and 3rd layer welding conditions Laser power: 5kW, welding speed: 0.8m / min, defocus distance: + 70mm, arc current: 200A
・ 4th layer welding conditions Laser power: 5kW, welding speed: 0.4m / min, defocusing distance: + 70mm, arc current: 200A
・ 5th layer welding conditions Welding speed: 0.18m / min, arc current: 200A

FIG. 5 shows a result of welding the welded members S and S under such welding conditions as an actual weld cross section.
As shown in the figure, even when the welded members S and S are as thick as 25 mm and welding is performed by multi-layer welding with more than two layers, the keyhole type laser welding is performed on the first layer. The second layer to the fourth layer are heat-conducting laser welded together with arc welding, and the fifth layer is arc welded so that the weld metal W is flattened without hot cracks in the lathe groove. It can be seen that it is well formed and no porosity is generated.

End of the description of one embodiment of the fastening Ru welding method according to the present invention above, embodiments are not limited to the above, and various modifications may be made without departing from the scope of the invention.
For example, in the first embodiment, the case where the plate thickness of the members to be welded S and S is 25 mm has been described. However, the plate thickness of the members to be welded S and S is not limited to this as long as the plate thickness is 25 mm or more. .
Further, in Example 1 described above, when the thickness of the members to be welded S, S is 25 mm, the welding is performed in five layers. However, the present invention is suitably used if the number of welding is three or more regardless of the thickness. Applicable.

Moreover, in the said embodiment, although the case where the to- be- welded members S and S were steel plates was demonstrated to the example, this invention, as long as the to-be-welded members S and S are metal members, an aluminum member and other weldable members It is also applicable to.

DESCRIPTION OF SYMBOLS 1 Laser arc hybrid welding apparatus 10 Arc welding apparatus 20 Laser welding apparatus 22 Laser irradiation head

Claims (1)

Laser welding joint between the plate thickness 25mm or more metal members welded in arc welding and multilayer welding three or more layers by laser arc hybrid welding a row cormorants welding method,
In the first layer, only the keyhole type laser welding is performed by making the condensing diameter of the laser beam smaller than the threshold value between the value corresponding to the keyhole type laser welding and the value corresponding to the heat conduction type laser welding,
In the final layer, only arc welding is performed,
Wherein in the layer between the first layer and the final layer, welding how to and performing the arc welding together the condensing diameter thermally conductive laser welding was greater than the threshold value.