JP3409592B2 - Assist gas nozzle for laser welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to an assist gas Roh <br/>'s Le for laser welding, more particularly, a laser beam from the substantially plane perpendicularly to the weld object Upon welding in, about the assist gas nozzle blowing the assist gas from a direction different from said laser beam irradiation direction toward the laser beam irradiation point on the object to be welded. In laser welding, in order to eliminate metal plasma (metal vapor) that is harmful to welding quality, helium (He), argon from the side toward the laser beam irradiation point position on the workpiece to be welded. Techniques in which an inert gas such as (Ar) or nitrogen (N ₂ ) is blown as an assist gas are disclosed in JP-A-58-125391 and JP-A-59-104.
No. 289 and JP-A-5-169288. [0003] In spraying the assist gas as described above, the assist gas nozzle for blowing the assist gas has a linear shape, and the length of the assist gas nozzle increases. However, depending on the shape of the work piece and the conveyance form, the assist gas nozzle length may not be sufficiently ensured in relation to other equipment. In such a case, the gas blown out from the assist gas nozzle causes turbulent flow, and the metal plasma that is the intended purpose as described above is not necessarily effectively removed, and there is a limit to improving the welding quality. The present invention has been made paying attention to the above-mentioned problems, and the structure of the assist gas nozzle capable of obtaining a necessary and sufficient rectifying effect even when the length of the straight portion of the assist gas nozzle is limited. Is to provide . According to the first aspect of the present invention, there is provided a laser on the work piece when welding the work piece by irradiating the work piece with a laser beam from a direction substantially perpendicular to the plane. a assist gas nozzle laser welding for blowing the assist gas from the direction different from the laser beam irradiation direction towards the beam irradiation point, the tip of the nozzle body, the eye as a means for rectifying the flow of a Shisutogasu
Metal mesh with a roughness of 300-400 mesh
It is characterized by a rate . Accordingly, in the invention described in claim 1 ,
The assist gas rectification effect is exerted by the mesh plate, which is the rectifying means provided at the tip of the nozzle body, and even if the length of the straight portion of the assist gas nozzle is limited, the length is insufficient. The mesh plate compensates for the rectifying effect . Thereby, the turbulent flow of the gas blown out from the assist gas nozzle is suppressed, and the directivity of the gas flow is enhanced. However, the mesh plate has a mesh roughness of 3
A sufficient rectifying effect can not be obtained with anything other than 00-400 mesh . According to the first aspect of the present invention, the means for rectifying the flow of the assist gas at the tip of the nozzle body is provided.
As a metal mesh with a mesh size of 300-400 mesh
By providing a ash plate , for example, even when the length of the straight part of the assist gas nozzle is limited due to the relationship with other equipment, the necessary and sufficient assist gas rectification effect is exerted to prevent the occurrence of turbulence. it can. As a result, the removal of the metal plasma, which is the original purpose of the assist gas spraying, is effectively performed to improve the welding quality, and the assist gas nozzle can be shortened to reduce the size and weight and reduce the installation space. Restrictions are also eased. FIG. 1 is a diagram showing a typical embodiment of the present invention, and shows a nozzle as a nozzle body which is the center of an assist gas nozzle 1. A gas supply pipe 4 is connected to the rear end of the body 2 via a screw-in type adapter 3, while a pipe-like nozzle tip 5 is fixed to the tip of the nozzle body 2, and the nozzle tip 5 A disc-shaped metal mesh plate 6 is mounted as a rectifying means through a screw-type ring cap 7. The mesh plate 6 has a mesh size of 300 to 400 mesh. Assist gas nozzle 1 having such a structure
2 is fixedly supported by a supporting means (not shown) so as to form an angle of, for example, 60 ° with respect to the irradiation direction of the laser beam B from the laser processing head 8 to the workpiece W, as shown in FIG. Adjustment is made so that the axis of the assist gas nozzle 1 coincides with the laser beam irradiation position P on the workpiece W. At the time of welding, when the workpiece W is irradiated with the laser beam B, the base metal melts at a predetermined penetration depth while the metal plasma Q is generated. If the metal plasma Q interrupts the laser beam B, the energy density of the laser beam B, which is a heat dose to the base material, is reduced, or the penetration depth is adversely affected. At the same time, the assist gas (inert gas) G is sprayed from the assist gas nozzle 1 toward the laser beam irradiation point position P, and the metal plasma Q harmful to the welding quality is quickly eliminated as described above. [0020] Particularly in the form status of the implementation is to be shorter than the conventional length L of the straight portion of the assist gas nozzle 1 and the first condition, blown from the assist gas nozzle 1 along with the shortening Since the mesh plate 6 is added to prevent the gas G from generating turbulent flow,
The mesh plate 6 sufficiently exhibits the effect of rectifying the assist gas G, and the directivity of the assist gas G with respect to the laser beam irradiation point position P is enhanced despite the shortening of the length L of the assist gas nozzle 1. The metal plasma Q can be efficiently removed. The inventor of the present invention pays attention to the fact that there is a correlation between the removal efficiency of the metal plasma Q and the shear strength of the weld which is the main element of the weld quality. The relationship with roughness was investigated. FIG. 3 is a graph showing the results. When 200 mesh mesh plate 6 is used, the shear strength varies greatly, and 300 to 400 is required to keep the shear strength within the allowable control limit. It turns out that the mesh is suitable. Similarly, the relationship between the shear strength of the welded portion and the length L of the straight portion of the assist gas nozzle 1 was also examined, and the results are shown in FIGS. FIG. 4 shows a conventional assist gas nozzle 1 having no mesh plate 6. As can be seen from FIG. 4, when the straight portion length L of the nozzle 1 is less than 100 mm, the shear strength varies. It can be seen that 100 mm or more is necessary to keep the shear strength within the allowable control limit. On the other hand, according to the present embodiment having the mesh plate 6 as shown in FIG. 5, the variation in the shear strength as a whole is compared regardless of the length L of the straight portion of the nozzle 1. It can be seen that about 60 to 80 mm is sufficient to keep the shear strength within the allowable control limit. That is, even if the straight portion L of the assist gas nozzle 1 is shortened, if the mesh plate 6 is attached, the flow of the assist gas G is rectified and is harmful to the extent that it does not affect the shear strength of the welded portion. It was confirmed that the metal plasma Q can be efficiently removed. The shortening of the length of the assist gas nozzle 1 as described above is effective, for example, in welding assembly of a steel road wheel H of an automobile as shown in FIG. That is, when the wheel rim and the wheel disk are welded in the manufacturing process of the steel road wheel H, it is necessary to weld at least a quarter of the circumference over a predetermined length. Therefore, conventionally, the road wheel H is changed from the previous process to the welding process S.
, And lifted up by a predetermined amount m for positioning, and then, considering the productivity, irradiate the laser beam B from the direction of 45 degrees with respect to the vertical axis O passing through the axis of the load wheel H. Welding is performed at two locations simultaneously while rotating the load wheel H by a predetermined amount, and then welding is performed at a total of four locations by rotating the load wheel H, which is an object to be welded, by 180 degrees and performing the same operation as described above. I am doing so. Thereafter, the load wheel H is lifted down again by a predetermined amount m and then carried out to the next process. At this time, if the length of the straight portion L of the assist gas nozzle 11 is large, the nozzle 11 and the road wheel H interfere with each other, but the assist gas nozzle 1 of the present embodiment.
Such a problem can be prevented beforehand by using. Here, as described above, in order to efficiently remove the metal plasma Q that is harmful to the welding quality, in addition to the flow of the assist gas being rectified, the axis of the assist gas nozzle 1 has a central axis. It is important that the laser beam irradiation point position P is correctly directed. Therefore, in this embodiment, the mesh plate 6 for assist gas rectification described above is effectively used, and this is used in combination with a CCD camera as an image pickup means so that the axis of the assist gas nozzle 1 is positioned at the position of the laser beam irradiation point. Aiming to match with P. More specifically, as shown in FIGS. 7 and 8, the nozzle body 2 of the assist gas nozzle 1 has an arm portion 12.
The arm portion 12 is positioned and fixed to the adjustment bracket 16 via the locate pin 14 and the bolt 15 in addition to the shim plate 13, while the adjustment bracket 16 is fixed to another adjustment bracket 17. Furthermore, this adjustment bracket 17 is provided with the mounting bracket portion 1 on the laser processing head 8 side.
8 is fixed. One adjustment bracket 16 is fixed to the other adjustment bracket 17 by a bolt 20 inserted from the elongated hole 19, but can be finely adjusted in the vertical direction according to the rotation operation of the adjustment screw 21. Similarly, the other adjustment bracket 17 is fixed to the mounting bracket portion 18 by a bolt 22 inserted into a long hole (not shown), but can be finely adjusted in the horizontal direction according to the rotation operation of the adjustment screw 23. However,
The angle θ of the assist gas nozzle 1 with respect to the axis of the laser processing head 8, that is, the optical axis of the laser beam B is fixed at 60 °. Then, the degree of freedom in the X direction of the assist gas nozzle 1 by replacing the shim plate 13, the degree of freedom in the vertical direction of the adjustment bracket 16, and the degree of freedom in the horizontal direction of the other adjustment bracket 17 are utilized. Then, the alignment of the axis of the assist gas nozzle 1 and the position P of the laser beam irradiation point on the workpiece W is performed. In this case, the adapter 3 at the rear end of the nozzle body 2 is once removed (see FIGS. 1 and 2), and a CCD camera 24 as an imaging means is detachably screwed and fixed instead. On the other hand, a laser beam for aiming (for example, a beam of He—Ne laser) B ₁ is irradiated from the laser processing head 8 toward the workpiece W, and the laser beam irradiation point position P on the workpiece W is CCD The image is captured by the camera 24 and displayed on the CRT display 25 that is a monitor. Then, while looking at the monitor screen, the position of the assist gas nozzle 1 is adjusted so that the laser beam irradiation portion P (the cross-hatched portion) is positioned at the center of the mesh plate as shown in FIG. . More specifically, the deviation in the direction of the arrow X between the laser beam B ₁ and the assist gas nozzle 1 is adjusted by replacing the shim plate 13 with a different thickness,
In other cases, the adjustment screws 21 and 23 are individually rotated to adjust the adjustment bracket 16 so that the adjustment bracket 16 is displaced in the vertical direction and the other adjustment bracket 17 is displaced in the horizontal direction. [0037] At this time, since the mesh of the mesh plate 6 to the imaging screen of the CCD camera 24 are displayed simultaneously, since the shift amount of the laser beams B ₁ can be grasped on the basis of the mesh, said aiming Matching can be done very easily. When the aiming is completed, the bolts 15, 20, and 22 are finally tightened, while the CCD camera 24 is removed from the nozzle body 2 and the adapter 3 is inserted as shown in FIGS. The gas supply pipe 4 is connected to prepare for regular laser welding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a typical embodiment of the present invention.
(A) is sectional explanatory drawing of an assist gas nozzle, the figure (B)
Is a right side view of FIG. FIG. 2 is an explanatory diagram at the time of laser welding using the assist gas nozzle shown in FIG. 1; FIG. 3 is a characteristic diagram showing the relationship between the mesh plate mesh roughness and the welded portion shear strength. FIG. 4 is a characteristic diagram showing the relationship between the length of a straight portion of a conventional assist gas nozzle and the shear strength of a welded portion. FIG. 5 is a characteristic diagram showing the relationship between the length of the straight portion of the assist gas nozzle of the present invention and the shear strength of the welded portion. FIG. 6 is a schematic explanatory diagram when laser welding is used for welding assembly of an automobile road wheel. FIG. 7 is a configuration explanatory view of an assist gas nozzle position adjusting mechanism. 8 is a left side view of FIG. FIG. 9 is an explanatory diagram when aiming the axis of the assist gas nozzle and the laser beam irradiation position when a mesh plate is used. [Description of Symbols] 1 Assist gas nozzle 2 Nozzle body (nozzle body) 4 Gas supply pipe 6 Mesh plate 8 Laser processing heads 16 and 17 Adjust brackets 21 and 23 Adjust screw 24 CCD camera (imaging means) 25 ... CRT display (image display device) B ... Laser beam P ... Laser beam irradiation point position G ... Assist gas W ... Workpiece

Claims (1)

(57) [Claims] [Claim 1] When welding an object to be welded by irradiating a laser beam from a direction substantially perpendicular to the surface thereof, the laser beam is directed toward the laser beam irradiation point on the object to be welded. a assist gas nozzle laser welding for blowing an assist gas from the laser beam irradiation direction different from the direction, of the nozzle body tip, mesh size as a means for rectifying the flow of a Shisutogasu is 300-400 mesh Money
An assist gas nozzle for laser welding, comprising a genus mesh plate .