JP2001047272A - Method for laser beam welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for laser beam welding capable of welding with excellent efficiency and stable quality by applying a twin spot optical system. SOLUTION: A laser beam from a laser oscillator is received in a part comprising a roof-type prism 14 to split the received laser beam into two portions and a holding part to hold the roof-type prism 14 movable in a direction rectangular to a laser beam optical axis, and then the received laser beams are applied to a laser beam welding machine comprising a beam splitting means to split the received beams in a variable splitting ratio and a working lens 15 to project the split laser beams onto different points as spot lights, thus two spot lights are arranged in the direction rectangular to the welding direction and at the same time distance between two spot lights is to be in a range of 0.3 mm-1.0 mm and yet output ratio of the two spot lights is to be in the range of 1:1-1:6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method, and more particularly to a laser processing method capable of performing stable quality welding.

[0002]

2. Description of the Related Art Welding can be performed by condensing a laser beam on a small spot and irradiating the object such as metal with a laser beam. However, in butt welding of dissimilar materials having different heat capacities and melting points, the energy suitable for each material is different, and in order to perform high-quality welding, it is desired to provide laser beam energies respectively suited to dissimilar materials. .

[0003] When performing such butt welding of dissimilar materials with a single laser beam, a technique is known in which the center position of the laser beam is decentered with respect to the butt position. In this case, high-precision irradiation position control is required, and it is difficult to cope with it.

[0004] The same applies to butt welding of the same material if there is a difference in the plate thickness. On the other hand, it is also desired to increase the gap allowance for the butting gap.

On the other hand, the present inventor has proposed a laser beam machine capable of forming two laser spot lights using a single laser beam (Japanese Patent No. 2902550).
did. This will be described briefly with reference to FIG. The laser beam generated by the laser oscillator is transmitted by an optical fiber and is emitted downward from the tip 101 of the optical fiber in the figure. Laser light diverging from the tip 101 of the optical fiber is collimated by a collimating lens 102 to become a parallel light beam. The parallel light beam travels straight and enters the roof prism 103. The roof prism 103 is
In the upper part of the figure, there is a symmetrical incident surface inclined left and right.

The roof prism 103 deflects the laser beam incident on the left half in the figure downward and to the right, and deflects the laser beam incident on the right half downward and to the left. As described above, the roof prism 103 plays a role of splitting the incident laser beam into two beams. The roof prism 103 is movable in a direction perpendicular to the optical axis of the laser beam. As a result, the division ratio becomes variable depending on the incident area ratio of the laser beam incident on the two inclined surfaces of the roof prism 103. The fact that the division ratio is variable means that the output ratio is variable.

The two laser beams split by the roof prism 103 are condensed by a condensing lens (working lens) 104 and condensed in different spots at different points. The position of the condensing point is determined by the deflection (refraction) angle given by the roof prism 103, the distance between the roof prism 103 and the condenser lens 104, the focal length of the condenser lens 104, and the like.

Although not shown, each of the above elements is housed in a cylindrical case. In particular, the roof prism 103 is held in a prism cell, and the condenser lens 104 is held in a condenser lens cell. The lower end of the prism cell and the upper end of the condenser lens cell are threaded to engage with each other. By screwing the condenser lens cell into the prism cell, the two are integrated. Further, it is configured such that the prism cell and the condenser lens cell can be integrally rotated by a rotation drive mechanism. As a result, the arrangement angle of the two spot lights can be arbitrarily set by rotating the roof prism 103 and the condenser lens 104 integrally about the optical axis of the incident laser beam. Here, the arrangement angle of the two spot lights means an angle between a line connecting the centers of the two spot lights and the welding direction. For welding, this angle is typically 9
0 degrees.

On the other hand, the collimating lens 102 is held in a collimating lens case. In the fiber case holding the distal end portion 101 of the optical fiber, a screw portion formed at the lower end thereof is screwed into a screw portion formed at the upper end of the collimating lens case and fixed.

An optical system for obtaining two spot lights from a single laser beam as described above is called a twin-spot optical system, but the detailed structure is disclosed in the above-mentioned patent publication. Detailed description is omitted.

[0011]

However, using only the twin spot optical system as described above, butt welding, especially when the thickness of two members to be welded is different,
Alternatively, in butt welding when the materials of the two members to be welded are different from each other, there is a problem that it is difficult to stably obtain a desired quality.

An object of the present invention is to provide a laser welding method capable of performing efficient and stable welding using a twin spot optical system.

[0013]

SUMMARY OF THE INVENTION The present invention provides a laser welding method for performing welding by irradiating two laser spot lights from a twin spot optical system so that the arrangement of the two spot lights is perpendicular to the welding direction. The distance between the two spot lights is set in the range of 0.3 mm to 1.0 mm, and the output ratio of the two spot lights is set to 1: 1 to 1:
6 is set.

The twin-spot optical system includes a light-receiving portion for receiving laser light from a laser oscillator, a roof-type prism for dividing the received laser light into two, and the roof-type prism with respect to the optical axis of the laser light. Beam splitting means for splitting a received laser beam including a holding portion which is held in a state of being movable in a direction perpendicular to the beam at a variable splitting ratio, and processing for irradiating the split laser beam as a spot beam to different positions Lens.

When the present laser welding method is applied to butt welding, the method is carried out with the center between two spot lights positioned on the welding line or shifted to one of the members to be welded. The amount of the shift is .0.
5 mm or less.

In the butt welding, when there is a difference between the plate thicknesses of the two members to be welded, the spot light having the larger output of the two spot lights is positioned on the member to be welded having the larger plate thickness.

On the other hand, when the materials of the two members to be welded are different in the butt welding, the output ratio of the two spot lights is changed within the range of the output ratio according to each material.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention divides a laser beam into two in order to increase the gap allowance between butt surfaces, particularly in a butt welding process, and focuses the two split laser beams at two points. Using a twin-spot optical system, a range in which welding efficiency and gap tolerance can be improved, which cannot be obtained with a normal single-spot optical system, is specified to improve performance.

1 to 3 show a laser welding apparatus to which the present invention is applied. This laser welding apparatus is shown in FIG.
It is the same in principle as the laser welding machine described in. That is, the laser light emitted from the distal end of the optical fiber 11 is incident on the collimator lens 13 through the half mirror 12 to be converted into a parallel light flux. This parallel light beam is split into two laser beams by being incident on the two inclined surfaces of the roof-shaped prism 14, and the split laser beams are condensed in two spots by the processing lens 15. The casing accommodating the roof prism 14 and the casing accommodating the processing lens 15 are internally formed by forming a female screw on one side and a screw on the other side and by screw engagement. The rotation drive mechanism as described in the above is integrally rotatable about its central axis. The knob 16 is for moving the roof prism 14 in a horizontal direction, that is, in a direction perpendicular to the optical axis of the laser beam. The knob 16 is combined with a rotary motion-linear motion conversion mechanism by a combination of a rack and a pinion. By turning the knob 16, the prism cell holding the roof prism 14 can be moved in the left-right direction in FIG. ing. Since the inclination angle (θ in FIG. 13) of the inclined surface of the roof-shaped prism 14 is very small,
Although difficult to distinguish in the figure, the two inclined surfaces appear on the left and right sides of the roof prism 14 in FIG.

In this laser welding apparatus, a CCD
An observation optical system using a camera is provided. The image of the welded portion is taken into the observation optical system through the half mirror 12 and the return mirror 17.

As described above, the movement of the roof-shaped prism 14 is realized by the one-axis driving stage, and has a function that can arbitrarily set the division ratio of the laser beam in the range of 1: 1 to 1: 0. I have. Further, by changing the roof-shaped prism 14 and changing its inclination angle θ, it is possible to change the distance d between the centers of the two spot lights (spot distance). Further, both the diameter D of the spot light and the spot interval d can be changed by changing the processing lens 15.

At the time of welding, a nozzle 20 shown in FIG. 3 is attached to a casing accommodating the condenser lens 15, and the welding is performed while supplying a shielding gas to the tip. That is, a conical space is formed at the tip of the nozzle 20 so as to surround two spot lights passing through the center portion, and the conical space opens toward the spot light irradiation unit. Further, a shielding gas such as an argon gas can be introduced into the conical space from the shielding gas introduction port 21.

The result of welding using the twin spot optical system as described above will be described below. The present invention is characterized in that the output ratio of the two spot lights and the applicable range of the spot interval d are specified as follows from the results obtained by testing using this twin spot optical system.

(1) First, a bead-on test was performed to observe the effect of the energy ratio of twin spot light on the weld bead shape. The bead-on test is performed under the test conditions shown in FIG.
This was bead-on to a cold-rolled steel sheet 30 having a thickness of 1 mm, and the results are shown in FIG.

As shown in FIG. 5, by changing the output ratio of the two spot lights, the cross-sectional shape of the bead is different.
In FIG. 5, JF indicates a case where the spot light is focused on the surface of the cold-rolled steel sheet 30 and is +2 m.
m means that the spot light is focused on a height position 2 mm away from the surface of the cold-rolled steel sheet 30 (in the direction of the arrow marked with + in FIG. 4). For reference, the case of single spot light is also shown, and by making it a twin spot, the bead shape shifts from a keyhole type that is thin vertically to a heat conduction type that spreads horizontally, and the bead width increases, The penetration depth becomes shallower. In particular, in the twin spot optical system, the output ratio is 1: 1.1 under the conditions of 3.5 kW and the spot light moving speed of 3.0 m / min.
The transition from the keyhole type to the heat conduction type is made at the boundary of 6. From these results, it can be seen that when it is desired to make the bead width larger than the penetration depth, an output ratio of about 1: 1 to 1: 1.6 is effective.

6 to 8 show the relationship between the output ratio and the penetration depth, the relationship between the output ratio and the bead width, and the relationship between the output ratio and the bead cross-sectional area, respectively. 6 to 8, it can be seen that there is a region where the bead width is kept large and the penetration depth does not change significantly within the range of the output ratio of 1: 1 to 1: 1.6. Accordingly, when the diameter D of the spot light is 0.6 mm and the spot interval d is 0.5 mm, the output ratio in the range of 1: 1 to 1: 1.6 is effective for keeping the bead width large under the present processing conditions. It can be seen that it is.

(2) Next, in order to observe the improvement of the butt gap tolerance due to the twin spot in the butt welding, under the test conditions shown in FIG.
Cold-rolled steel sheet 41 having a thickness of 0.8 mm and 1.6 mm shown in FIG.
The result of the butt welding test at 42 will be described. The butted end faces of the two cold-rolled steel sheets 41 and 42 are shaper ground. Further, the two spot lights are applied so as to form an array perpendicular to the welding line with the welding line therebetween. In particular, the output ratio of the two spot lights is 1: 1.
In the case where the outputs of the two spot lights are different, except for the case of
It is needless to say that the light is irradiated to No. 2.

Referring to FIG. 10, in this test, the maximum butting gap was 0.3 m for a single spot light.
m, a sound weld bead was obtained in the appearance evaluation. In contrast, in the twin spot optical system according to the present invention, 2
By optimizing the output ratio of the two spot lights, a sound weld bead was obtained even in a gap of at most 0.5 mm.

As described above, from FIG. 10, by changing the output ratio of the two spot lights, the two cold-rolled steel sheets 4
It can be seen that sound welding can be performed even if the butting gaps of Nos. 1 and 42 are large. Output ratio than 1: 1
It can be seen that by setting the ratio to 1: 2 to 1: 4, the gap margin increases.

FIG. 11 shows the output ratio and the butting gap amount at which a sound bead is obtained. In the case of a single spot light, the gap tolerance is 0.3 mm. On the other hand, the gap tolerance is improved from 0.4 mm to 0.5 mm between the output ratios of the two spot lights of 1: 1 to 1: 8, and this range of the output ratio is effective.

Next, regarding the distance d between the two spot lights, the above experimental results are obtained when the distance d is 0.5 mm, but similar results can be obtained when the distance d is 0.3 mm. This has been confirmed (see FIG. 13). In addition, the upper limit of the interval d requires that the two spot lights are actually irradiated so that some of them overlap each other as shown in FIG. In order to satisfy this, it is about 1 mm depending on the diameter D of the spot light.

From the above, in the twin spot optical system,
By arranging two spot lights in a direction perpendicular to the welding direction and performing welding, it is effective to increase the bead width, and in the case of butt welding, the gap tolerance can be improved. Further, the range of the output ratio of the two spot lights varies depending on the thickness of the plate to be combined, and as a range that is effective for both (1) the shape of the weld bead and (2) the tolerance of the butt gap: The range of 1-1: 6 is effective. Of course, even if the output of the laser oscillator changes,
This effect is obtained.

FIG. 12 shows one side of two cold-rolled steel sheets 41 and 42 to which two spot lights are butt-welded, in particular, a spot light having a large output is applied to the cold-rolled steel sheet 4 having a larger thickness.
The case where welding is performed by shifting to the two sides is shown, and in this case, the same effect can be obtained. In this case, it has been confirmed that the upper limit of the shift amount (the distance from the end face of the cold-rolled steel sheet 42 to the intermediate point between the centers of the two spot lights) is 0.5 mm.

On the other hand, when the materials of the two members to be welded are different, the output ratio of the two spot lights may be changed within the range of the output ratio according to each material.

Although the present invention has been described with reference to laser welding, the present invention can be applied to the above-described output ratio change also in a cutting method. In this case, the arrangement direction of the two spot lights is adjusted to the direction of the cutting line.

[0036]

According to the present invention, it is possible to provide a laser welding method capable of performing efficient and stable welding by using a twin spot optical system.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a twin spot optical system in a laser welding apparatus to which the present invention is applied.

FIG. 2 is a longitudinal sectional view of the twin spot optical system of FIG. 1 as viewed from the side of FIG.

FIG. 3 is a longitudinal sectional view showing a configuration of a nozzle combined with a tip portion of the twin spot optical system of FIG.

FIG. 4 is a diagram for explaining a bead-on test performed to observe the effect of the energy ratio of twin spot light on the weld bead shape in the present invention.

5 is a diagram showing a cross-sectional shape of a welded portion obtained by the bead-on test of FIG. 4 together with a cross-sectional shape of the welded portion in the case of a single spot light as a comparative example.

6 is a diagram showing the relationship between the output ratio of twin spot light measured in the bead-on test of FIG. 4 and the penetration depth.

FIG. 7 is a diagram showing a relationship between an output ratio of twin spot light measured in the bead-on test of FIG. 4 and a bead width.

FIG. 8 is a diagram showing a relationship between an output ratio of twin spot light measured in the bead-on test of FIG. 4 and a bead cross-sectional area.

FIG. 9 is a diagram for explaining a case where a laser welding test using twin spot light is applied to butt welding.

10 is a diagram showing a cross-sectional shape of a welded portion measured in the laser welding test of FIG. 9 together with a cross-sectional shape of the welded portion in the case of a single spot light as a comparative example.

11 is a diagram showing the relationship between the output ratio of twin spot light measured in the laser welding test of FIG. 9 and the butting gap amount when the interval d between twin spot light is 0.5 mm.

FIG. 12 is a diagram showing a case where the laser welding test of FIG. 9 is performed by shifting twin spot light.

13 is a diagram showing the relationship between the output ratio of twin spot light measured in the laser welding test of FIG. 9 and the butting gap amount when the interval d between twin spot light is 0.3 mm.

FIG. 14 is a longitudinal sectional view for explaining a schematic configuration of a twin spot optical system to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Optical fiber 12 Half mirror 13, 102 Collimating lens 14, 103 Roof prism 15 Processing lens 16 Knob 17 Folding mirror 20 Nozzle 21 Shield gas introduction port 104 Condensing lens

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 103: 18 (72) Inventor Kiyoyuki Fukui 1-8 Fuso-cho, Amagasaki City, Hyogo Prefecture Sumitomo Metal Industries (72) Inventor Masanori Taiyama 1-8 Fuso-cho, Amagasaki-shi, Hyogo Sumitomo Metal Industries, Ltd. F-term (reference) 4E068 BA01 BE00 CA11 CB08 CD09 DB01 4E081 AA01 BA02 BA16 BA34 CA19 DA72 FA08

Claims (6)

[Claims] In a laser welding method for performing welding by irradiating two laser spot lights from a twin spot optical system, an arrangement of two spot lights is made to be perpendicular to a welding direction and two spots are arranged. 0.3mm ~
A laser welding method, wherein the laser beam is formed in a range of 1.0 mm and an output ratio of two spot lights is in a range of 1: 1 to 1: 6. 2. The laser welding method according to claim 1, wherein the twin spot optical system includes: a light receiving unit that receives a laser beam from a laser oscillator;
The received laser light at a variable split ratio including a roof-type prism for splitting into two, and a holding unit that holds the roof-type prism movable in a direction perpendicular to the optical axis of the laser light. A laser welding method comprising: a beam splitting means for splitting; and a processing lens for irradiating the split laser light to different positions as spot light. 3. The laser welding method according to claim 1, wherein the laser welding is a butt welding, and a center between two spot lights is positioned on a welding line or one of the members to be welded. A laser welding method characterized in that the method is performed in a state where the laser beam is shifted to a predetermined position. 4. The laser welding method according to claim 3, wherein the shift amount is 0.5 mm or less. 5. The laser welding method according to claim 3, wherein, in the butt welding, when there is a difference between the plate thicknesses of the two members to be welded, the larger one of the two spot lights is used as the plate light. A laser welding method characterized by being positioned on a member to be welded having a larger thickness. 6. The laser welding method according to claim 3, wherein in the butt welding, when the materials of the two members to be welded are different, the output ratio of the two spot lights is in the range of the output ratio according to each individual material. A laser welding method characterized in that the method is changed by: