JP2929447B2 - Welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method in which two or more plate members are brought into close contact with each other and welded by irradiating a high energy beam such as a laser beam.

[0002]

2. Description of the Related Art Conventionally, a vehicle structure used for a railway vehicle or the like is assembled by welding an outer panel panel and a reinforcing member integrally formed with ribs and joints (Japanese Patent Laid-Open No. 4-12659). No.). As an example of the welding method, after the outer panel and the reinforcing member are brought into close contact with each other, a large current is applied after the joint between the outer panel and the reinforcing member is sandwiched between the two electrodes, thereby reinforcing the outer panel and the reinforcing member. Resistance spot welding, which generates Joule heat at a joint with a member and heats and melts it, is generally used. In this method, a large number of welding spots are formed at the joint between the outer surface of the outer panel and the reinforcing member.

[0003]

However, in the conventional resistance spot welding, indentations due to electrode pressing and discoloration due to high-temperature oxidation are likely to remain on the outer surface (decorative surface) of the outer panel. In particular, in the case of stainless steel vehicles that are used without painting, repair and cleaning after welding are indispensable in order to remove indentations and discoloration of the outer panel due to product quality. Has become. Further, since resistance spot welding is spot welding, a large number of spot weldings are required to secure the joining strength between members. Therefore, the number of movements and the number of movements of the electrode increase, and the time required for welding increases,
Position control is also complicated.

Therefore, non-contact type laser lap welding has been studied instead of contact type resistance spot welding. The outer plate of the railway vehicle is formed of carbon steel, stainless steel, or the like having a plate thickness of about 1 mm. The material and plate thickness of the reinforcing member are almost the same as those of the outer plate. When the outer plate and the reinforcing member are to be joined by laser welding, a laser beam is irradiated from the reinforcing member side to penetrate the reinforcing member and reach the outer plate to perform joining. .

FIG. 6 is a sectional view showing an example of a conventional laser welding method. By laying the reinforcing member 2 on the outer plate 1 and irradiating the laser beam 61 with the surface normal direction P of the reinforcing member 2 parallel to the optical axis 60, that is, perpendicular to the surface of the reinforcing member 2, A penetration region 62 from the surface of the reinforcing member 2 to the inside of the outer plate 1 is formed.

At this time, in order to make the outer surface 1a of the outer plate 1 smooth and maintain an aesthetic appearance, it is necessary to stop the penetration region 62 by the laser beam 61 inside the outer plate 1 and not to penetrate the outer plate 1. . Furthermore, when the outer plate 1 made of stainless steel is used, the outer surface 1a is generally not often coated, so that if the outer surface 1a undergoes oxidative discoloration due to welding heat, the outer plate appearance is greatly impaired. Therefore, when laser lap welding is used, the penetration area 62 by the laser beam 61 is suppressed to a predetermined depth or less inside the outer plate 1 and the outer surface 1
It is necessary to suppress overheating of a.

In FIG. 6, the bottom 62 of the penetration region 62
When a is within the region RA, the penetration is too shallow and sufficient bonding strength cannot be obtained. On the other hand, the bottom 6 of the penetration region 62
When 2a is in the region RC, the penetration is too deep and the temperature rise of the outer surface 1a due to welding heat is increased, which may cause discoloration of the outer surface 1a due to high-temperature oxidation or expose the weld bead. Therefore, the bottom 62a of the penetration region 62
Is a region RB (length L) suitable for bonding strength and appearance.
It is necessary to control within the range of 1).

However, since the thickness of the outer plate is as thin as about 1 mm, it is extremely difficult to control the penetration inside the outer plate in the depth direction. In particular, when performing a two-dimensional shape welding by relatively moving a laser beam, for example, if a predetermined welding speed cannot be maintained at a corner, the amount of heating at the corner becomes excessive, and the penetration area on the outer plate is reduced. There is a risk of reaching the outer surface.

It is an object of the present invention to provide a welding method which makes it easy to control the penetration depth with a high energy beam such as a laser.

[0010]

SUMMARY OF THE INVENTION According to the present invention, two or more plate members are stacked and a high energy beam such as a laser beam is applied in a range of 30 to 45 degrees with respect to the normal to the surface of the plate members. Irradiation while moving while tilting at the set tilt angle, heating and melting the area from the surface of the front plate member to the inside of the back plate member, the bottom of the molten pool does not reach the outer surface of the back plate member In this manner, the welding is performed while controlling the beam output or the beam moving speed.

[0011]

[0012]

[0013]

According to the present invention, a high-energy beam such as a laser beam is irradiated onto a surface normal of a plate-like member in a state where two or more plate-like members exemplified by, for example, an outer panel of a vehicle structure and a reinforcing member are stacked. Irradiation is performed at a predetermined inclination angle θ with respect to the direction. Therefore, as compared with the conventional case where the laser beam is irradiated vertically, the distance until a high-energy beam such as a laser penetrates each plate member becomes longer in proportion to the reciprocal of cos θ. Therefore, when the depth of the penetration region is controlled by the beam moving speed, the laser output, or the like, the controllable range is expanded, so that the depth of the penetration region is easily controlled.

Further, since the incident direction of the laser beam is inclined with respect to the surface of the plate-like member, the reflected light on the surface hardly returns to the incident direction, so that the return light to the laser oscillator is significantly reduced. Laser oscillation stabilizes.

Further, the metal vapor generated at the time of welding tends to return in the direction of the surface normal, but flows into the laser welding head because the incident direction of the laser beam is inclined with respect to the surface of the plate member. The amount of metal vapor is reduced, and the replacement life of optical elements such as reflectors and lenses can be extended.

Further, since the laser beam is inclined with respect to the bonding surface, the cross-sectional area obtained by cutting the penetration region along the bonding surface becomes larger in proportion to the reciprocal of cos θ as compared with the conventional perpendicular incidence. . Therefore, the joint strength increases due to the increase in the welding area. In addition, by controlling the beam output or the beam moving speed so that the bottom of the molten pool does not reach the outer surface of the back side plate-shaped member, the appearance defects such as weld beads, indentations, and discoloration do not remain on the outer surface of the plate-shaped member. , High quality welding can be realized.

Further, it is preferable that the inclination angle of the laser beam is set in the range of 30 to 45 degrees with respect to the surface normal direction. When the inclination angle is larger than 45 degrees, the surface reflection increases and the energy contributing to welding decreases, and the area to be melted becomes longer, so that the welding time becomes longer. Conversely, if the inclination angle is smaller than 30 degrees, the conventional problem gradually emerges. Therefore, when the laser welding head is tilted to such an extent that interference between the laser welding head and the plate-like member does not occur, this range becomes appropriate.

[0018]

[0019]

FIG. 1 is a perspective view for explaining an embodiment of the present invention. FIG. 2 is a configuration diagram showing a cross section taken along line A1-A1 in FIG. After the flat outer panel 1 and the reinforcing member 2 integrally formed with the ribs 2b and the joints 2a are placed on the processing table 10 and brought into close contact with each other, the laser beam 21 is obliquely irradiated from the reinforcing member 2 side. By performing the laser welding, a railway vehicle structure in which the outer panel 1 and the reinforcing member 2 are joined is obtained.

The reinforcing member 2 is formed by forming a flat plate such as a steel plate into a plurality of rounded trapezoidal depressions by press molding or the like, and the bottom surface of the depressions constitutes the joint 2a. The joining portion 2a and the flat portion 2c of the reinforcing member 2 are connected by a rib 2b formed of an inclined surface or a vertical surface.
b increases the rigidity of the railway vehicle structure. The outer panel 1 and the reinforcing member 2 are formed of carbon steel, stainless steel, aluminum alloy, or the like.

In FIG. 2, a high-power laser beam 21 is focused from the reinforcing member 2 side to a portion where the joining portion 2a of the reinforcing member 2 and the outer panel 1 are in close contact with each other. P is irradiated at a predetermined inclination angle θ. Then, a region from the surface of the reinforcing member 2 to the inside of the outer panel 1 is heated and melted to form a wedge-shaped molten pool. Therefore, when a welding head that generates the laser beam 21 is mounted on a numerical control processing machine or the like and the laser beam 21 is continuously moved along the joint 2a, a linear welding line 8 can be formed. . At this time, the length of the welding line 8 and the welding path are determined in consideration of the required joining strength and the press shape of the reinforcing member 2.

FIG. 3 is an enlarged sectional view showing a welding state of a laser welding portion. The reinforcing member 2 is superimposed on the outer plate 1,
The optical axis 2 has an inclination angle θ with respect to the surface normal direction P of the reinforcing member 2.
By irradiating the laser beam 21 at an angle of 0, the penetration region 22 is formed along the optical axis 20 from the surface of the reinforcing member 2 to the inside of the outer plate 1.

At this time, in order to make the outer surface 1a of the outer plate 1 smooth and maintain an aesthetic appearance, it is necessary to stop the penetration region 22 by the laser beam 21 inside the outer plate 1 and not to penetrate the outer plate 1. Become. Further, in the case of using the stainless steel outer plate 1 whose surface coating may be omitted, if the outer surface 1a undergoes oxidation discoloration due to welding heat, the outer plate appearance is greatly impaired. Is suppressed to a predetermined depth or less inside the outer plate 1 to suppress overheating of the outer surface 1a.

In FIG. 3, the bottom portion 22 of the penetration region 22
“a” is controlled within a range of an appropriate region RB (length L2) in terms of bonding strength and appearance. Here, when compared with the length L1 of the appropriate region RB shown in FIG. 6, the length L2 of the appropriate region RB shown in FIG. 3 satisfies L2 = L1 / cos θ, and 0
If <θ <90 degrees, the relationship of L1 <L2 is established. Therefore, when controlling the depth of the penetration region 22 by the beam moving speed, the laser output, or the like, the controllable range is expanded, so that the depth control of the penetration region 22 becomes significantly easier. Further, since the incident direction of the laser beam 21 is inclined with respect to the surface of the reinforcing member 2, return light to the laser oscillator and adhesion of metal vapor to the welding head are significantly reduced. Further, since the cross-sectional area of the penetration region 22 cut along the bonding surface is larger than that of the conventional normal incidence,
The joining strength is greatly improved.

The inclination angle θ of the laser beam 21 is
In terms of the energy injection efficiency, the shape of the laser welding head, and the securing of an appropriate region RB, it is preferable that the angle is set in the range of 30 to 45 degrees with respect to the surface normal direction P.

Returning to FIG. 2, by bringing the outer surface 1a of the outer panel 1 into close contact with the processing table 10, the processing heat of the outer panel 1 is radiated to the processing table 10, so that the temperature rise is suppressed. Therefore, the processing table 10 is preferably formed of a material having excellent heat conductivity, for example, copper or a copper alloy. Further, by cooling the processing table 10 with water, the heat radiation efficiency is further improved.

In the inside of the processing table 10 shown in FIG.
A cooling pipe 30 for flowing a cooling medium M such as water is formed to cool the processing table 10. The cooling pipe 30 is connected to a pipe 32 via a connector 31, and further includes a fluid pump 33 for circulating the cooling medium M and a storage tank 3 for storing the cooling medium M and lowering the temperature.
4 are connected.

FIG. 4 is a sectional view showing an embodiment of the laser welding head according to the present invention. Laser welding head 40
Are reflecting mirrors 42 and 43 for reflecting the laser beam 21;
Focusing lens 45 for focusing laser beam 21
And a gas nozzle 47 for injecting an assist gas such as an argon shield gas to the workpiece B, and a housing 41 for accommodating them. A bent hollow conduit is formed in the housing 41, through which the laser beam 21 travels. The condenser lens 45 is provided inside the hollow conduit and is attached by a lens holding ring 44. Further, a gas pipe 46 connected to the gas nozzle 47 is formed in the housing 41, and an assist gas is supplied from an external gas cylinder or the like.

Next, the operation will be described. When the laser beam 21 supplied from a laser oscillator (not shown) is introduced into the housing 41 along the surface normal direction P of the workpiece B, the reflecting mirror 42 is reflected in a right angle direction, and the laser beam is further reflected. 21 travels inside the housing 41 and is reflected by the reflecting mirror 43 so as to be incident on the surface normal direction P at an inclination angle θ. Laser beam 21 reflected by reflecting mirror 43
Are condensed in a spot shape on the workpiece B by the condenser lens 45. In this way, energy is concentrated on the welding point B1 of the workpiece B, and laser welding by heating and melting is performed.

On the other hand, the gas nozzle 47 supplies the assist gas in the vicinity of the welding point B along the surface normal direction P, thereby uniformly forming a shield atmosphere surrounding the welding point B1. Oxidation reaction is suppressed, and stable welding can be realized.

FIG. 5 is a graph showing a comparative example of welding evaluation according to the prior art and the present invention. The horizontal axis indicates the welding speed of the laser beam, and the vertical axis indicates the beam incident angle θ with respect to the surface normal direction of the work to be welded. The workpiece to be welded is obtained by joining the 0.8 mm thick reinforcing member 2 and the 1.2 mm thick outer panel 1. Further, the laser beam output is kept constant regardless of the welding speed.

First, when the incident angle θ = 0 °, 1) when the welding speed is less than 5 m / min, the penetration region 62 in FIG. 5-
In the range of 6 m / min, rear surface oxidation discoloration occurs on the outer panel 1, and 3) in the range of welding speed of 6 to 7 m / min, the bottom 62a of the penetration region 62 is controlled to be within the region RB and proper welding is performed. 4) When the welding speed was 7 m / min or more, the penetration of the penetration region 62 was insufficient and the penetration was insufficient.

Next, when the incident angle θ is 30 degrees, 1) when the welding speed is less than 4 m / min, the penetration region 22 shown in FIG. Is 4
When the welding speed is in the range of 5 to 6.5 m / min, the rear surface oxidation discoloration occurs in the outer panel 1 in the range of 5 to 5 m / min.
The bottom portion 22a of the penetration region 22 is controlled to be within the region RB to obtain proper welding. 4) If the welding speed is 6.5 m / min or more, the penetration depth is insufficient because the penetration region 22 is not deep enough. .

As described above, when the laser beam is inclined with respect to the workpiece, the range of the welding speed at which proper welding can be obtained is shifted in a direction of decreasing the overall speed (left side in FIG. 5). It is understood that the size is increased by about 1.5 times, so that the depth control of the penetration region is facilitated accordingly.

In the above description, the case where the outer panel 1 and the reinforcing member 2 constituting the railway vehicle body are used as the plate-like members to be welded is exemplified. However, the present invention is applied to a case where three or more members are overlap-welded. May be applied as well.

As described in detail above, according to the present invention, a high-energy beam such as a laser is irradiated at an inclination angle .theta. Of 30.degree. To 45.degree. Because the control tolerance of the embedding area is expanded,
Control of the depth of the penetration region is facilitated. In addition, return light to the laser oscillator and return of metal vapor are remarkably reduced, and strength can be improved by enlarging a welding area.

[0037]

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a cross section taken along line A1-A1 in FIG.

FIG. 3 is an enlarged sectional view showing a welding state of a laser welding portion.

FIG. 4 is a sectional view showing one embodiment of a laser welding head according to the present invention.

FIG. 5 is a graph showing a comparative example of welding evaluation according to the related art and the present invention.

FIG. 6 is a sectional view showing an example of a conventional laser welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer panel 2 Reinforcement member 2a Joining part 2b Rib 2c Flat part 8 Welding line 10 Processing table 20 Optical axis 21 Laser beam 22 Penetration area 40 Laser welding head 42, 43 Reflecting mirror 45 Condensing lens 47 Gas nozzle

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Koga 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Kobe Plant (72) Inventor Hiroshi Hase Higashi-Kawasaki, Chuo-ku, Kobe-shi, Hyogo 3-1-1 Cho-cho Kawasaki Heavy Industries, Ltd. Kobe Plant (56) References JP-A-58-38688 (JP, A) JP-A-6-106376 (JP, A) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B23K 26/00 310 G

Claims (1)

(57) [Claims] 1. A method in which two or more plate-like members are overlapped, and a high-energy beam such as a laser is tilted at a tilt angle set in a range of 30 to 45 degrees with respect to the normal direction of the surface of the plate-like members. Irradiate while moving, heat and melt the area from the surface of the front plate member to the inside of the back plate member, and beam output or beam moving speed so that the bottom of the molten pool does not reach the outer surface of the back plate member A welding method characterized by joining while controlling the welding.