JPH0771757B2 - Method and apparatus for manufacturing ultra-thin metal pipe using modulated output YAG laser - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for manufacturing a pipe by YAG laser welding of an ultrathin metal foil having a thickness of 30 to 150 μm.

[Prior Art] It is necessary to form an ultra-thin metal foil in a continuous tube shape to converge opposing butt end faces into a wedge shape and to perform electrical welding such as TIG near the focusing point to the pipe edge end face of the welding point. It is suitable for welding ultra-thin metal foil because it requires precise adjustment of conditions such as edge burr and roughness, accurate adjustment of gap and offset conditions, accurate adjustment of butt and strict heat input. Absent. Further, since the heat-affected layer is large, there is a problem in terms of weldability, and it is not particularly suitable for bending a pipe. Even in the conventional method of performing laser welding, the above edge,
Due to precise adjustment of butt conditions such as gaps and offsets, and severe heat input restriction, it is necessary to precisely limit the laser irradiation position, beam diameter, and power when welding ultra-thin metal foil. Is difficult.

In addition, the welding method of irradiating with a low-density YAG laser as disclosed in JP-A-60-96382 aims at alleviating the severe butt conditions as described above, and at the same time, it does not apply to the non-thin metal foil surface. Reduce the ratio of laser absorptance during contact and melting,
This prevents welding defects such as burn-through and humping. However, as to the prevention of welding defects, as described in the publication, the change ratio R _y between the absorption rate α _c of the YAG laser when it is not melted and the absorption rate α _m when it is melted is about R _y > 2.5. Although it is sufficiently smaller than the absorption rate change ratio R _c > 11 of the CO ₂ laser, there is no change in that the absorption rate of the input energy of the laser changes more than twice when it is not melted and when it is melted. In the case of welding a material having a small heat capacity such as an ultra-thin metal foil, even a slight change in the welding state has a great effect on the welding result, so it cannot be said that it is sufficient to prevent welding defects.

[Problems to be Solved by the Invention] The present invention is directed to severe edge conditions and offsets that cannot be overcome by electric welding and a conventional laser welding method when continuously forming an ultrathin metal foil into a tubular shape and forming a pipe by welding. conditions,
It is an object of the present invention to provide a manufacturing method and apparatus capable of overcoming the problems of the butt condition and the heat input condition and obtaining a high quality ultra-thin metal foil pipe having a small heat-affected zone of melting.

[Means for Solving the Problems] The present invention has been made in order to achieve the above-mentioned object, and the gist of the present invention is to continuously form an ultra-thin metal foil so as to form opposing butt end surfaces. In an ultra-thin metal foil pipe manufacturing device that converges and welds in a wedge shape, a simmer power supply part including a lamp ignition trigger circuit connected in parallel to each laser excitation lamp and a pulse to suppress interference A low-density focused beam with a laser power source equipped with a pulsed power supply through a transformer, which emits a modulated output by superimposing a pulsed laser output on a continuous laser output, and a wedge-shaped part formed in the focusing part of an ultrathin metal foil. The ultra-thin metal foil pipe manufacturing device using the YAG laser, which is equipped with an optical system for irradiating with, and the ultra-thin metal foil are continuously molded to converge the facing end faces into a wedge shape. The wedge shape In the method of manufacturing an ultra-thin metal foil pipe in which a portion is irradiated with a laser and welded, the gap of the wedge-shaped portion formed by holding the offset of the end to 30% or less of the plate thickness of the ultra-thin metal foil is extremely thin. The thickness of the low density focused YAG laser beam that emits the modulated output by superimposing the pulse output on the continuous output is made to coincide with the point of 1 to 5 times the plate thickness of the metal foil, and the plate thickness is applied from the end face. Is a method of melting a region 2 to 10 times as large as the above and pressing the melting end face immediately before solidification to complete welding.

[Operation] (1) As shown in FIG. 1, in the forming process of the pipe manufacturing method of the present invention, an ultrathin metal foil is continuously formed so that the opposing end faces are converged into a wedge shape, and at the welded portion. It can be applied to any method as long as the offset of the edge face is within 30% of the plate thickness.

(2) FIGS. 2 and 3 are conceptual diagrams of a low density energy beam region soft welding method using a YAG laser oscillator that emits a modulated output by superimposing a pulse output on a continuous output. The YAG laser is radiated where the gap of the groove of the ultra-thin metal foil is 1 to 5 times the plate thickness, and the irradiation beam diameter is 2-10 times the plate thickness on both ends of the ultra-thin metal foil. Focuses so that it melts across the width, and it welds without melting or humping.
At this time, the width of the melted portion at both ends of the ultrathin metal foil + gap length at both ends g = the beam diameter D of the YAG laser. The beam diameter D is controlled by the focal length f of the lens or the defocus irradiation that sets the focal position to the upper side of the steel plate. When the laser irradiation position is set so that the groove gap is less than the plate thickness value, it is similar to irradiation at the abutting point, and the leaning due to melting of both ends is reduced, and the edge offset is 10% of the plate thickness. The following precision is required. This requires very advanced technology for ultra-thin metal foil and is difficult to implement. In addition, at a position where the value exceeds 5 times the plate thickness, both ends are too far apart from each other, so that they cannot be abutted well and good welding cannot be performed. Also, if the welding area from the end face is less than twice the plate thickness, insufficient welding will result.
If it exceeds 10 times, excessive welding will occur and burn through will occur.

(3) Issuing a modulation output by superimposing a pulse output on a continuous output of a YAG laser has the following advantages. The absorptance of laser light on the metal surface is greatly different between non-melting and melting, which changes the heat input state, which causes welding defects in the welding of ultra-thin metal foil. Therefore, JP-A-60
-96382 using a YAG laser, non-melting on the surface of the ultra-thin metal foil, to reduce the ratio of the laser absorption rate at the time of melting, there is a method of preventing welding defects such as burn-through, humping It is disclosed. However, as to the prevention of welding defects, as described in the publication, the change ratio of the absorption rate α _c of the YAG laser when it is not melted and the absorption rate α _m when it is melted.
R _y is approximately R _y > 2.5, and the absorption rate change ratio R _c > of the CO ₂ laser
Although it is sufficiently smaller than that of 11, the absorption rate of the input energy of the laser changes twice or more during non-melting and melting, and it has a small heat capacity like ultra-thin metal foil. In welding, a slight change in the welding state has a large effect on the welding result, so controlling the laser input energy to the optimum conditions is very difficult because the control range is narrow and it is sufficient to prevent welding defects. Is hard to say.

On the other hand, by using the ripple output YAG laser in which the pulse output is superimposed on the continuous output according to the present invention, the conditions for the optimum control of the laser input energy as described above can be relaxed. FIG. 4 shows an outline of the modulated YAG laser of the present invention. P _P is the peak output value of the pulse portion of the modulation output, P _C is the output value of the continuous oscillation part of the modulation output, and P _av is the time average value of the modulation output. The operation is as follows. When the surface of the metal foil is in a non-melted state, the pulsed portion of the ripple output is irradiated with high energy to instantly bring the surface of the metal foil into a molten state. Then, when the laser beam absorpted into the molten state and the absorptance of the laser beam became 0.9 or more, the laser output of ripple oscillation was changed from the peak value P _P of the ripple output to P _{C of the} continuous output according to the change of the absorptivity. By reducing the change, the ultra-thin metal foil is prevented from over-melting and the molten state is maintained. Further, when the surface of the ultra-thin metal foil begins to solidify and the absorptance of the laser beam decreases, high energy of the pulse portion of the ripple output is input again to keep the ultra-thin metal foil surface in a molten state. The pulse part has a high energy density and always forms the nuclei of melting on the surface, but the heat input by it is small, and it does not become added heat.

By repeating the melting and solidification as described above at high speed, it is possible to stably perform welding without welding defects such as burn-through and humping for ultra-thin metal foil. In this way, the control range of the energy input of the laser is widened, and it is possible to easily weld the ultra-thin metal foil.

(4) The relaxation of the forming conditions by the surface heat source welding method using the low density energy beam is as follows.

By irradiating the laser with the gap g in FIG. 2 at about twice the plate thickness, the contact range becomes wider than in the case where the ultrathin metal foil is melted at the butt point (the fifth point).
Figure), the condition of offset (10% or less of the plate thickness) is relaxed.

Even if the state of the butt point (the degree of overlap of both ends of the ultra-thin metal foil) changes subtly, heat can be input without being affected by the subtle changes in heat capacity that occur, so humping and burn-through can be prevented. Can do no welding. By this method, the allowable value of the gap and offset (10% or less of the plate thickness) can be greatly expanded (2 to 3 times).

(5) FIG. 10 shows a block diagram of the excitation lamp power supply circuit of the laser oscillator according to the present invention. The lamp has a simmer power supply including a trigger circuit for lamp ignition,
The pulse power supply units are connected in parallel via a pulse transformer to suppress mutual interference. The function of each part lock is shown below.

・ SCR control circuit Constant current controller 18 Supplies simmer current to the lamp. This maintains the lamp in a conducting state and excites the YAG rod above the laser oscillation threshold.

-Trigger generation circuit 19 Generates a high-voltage trigger for forming a discharge path in the lamp when the lamp starts to light.

-Boost voltage generation circuit 20 Supplies a boost voltage that maintains the discharge path in the lamp formed by the trigger until the simmer power supply starts up.

-Pulse oscillator 21, FET22 and pulse transformer 23 (PT) Controls the pulse current supplied to the lamp. The pulse current is
It is controlled by FET22 and supplied to the lamp through pulse transformer 23 (PT).

-Reverse current prevention diodes (D1, D2) Stabilize the simmer current against fluctuations in the lamp impedance due to discharge of the simmer current.

・ Vacuum relay (RY1) Shields the pulse power supply from the simmer power supply against the trigger pulse and boost voltage when the lamp is lit.

Next, the principle of pulse oscillation of the laser according to the present invention will be described. Although the basic principle of pulse oscillation is similar to that of the normal pulse method, in the present invention, the YAG rod is excited in advance by the simmer current to a level above the laser oscillation threshold. Therefore, in the present invention, by superimposing a pulse current value lower than that of the conventional normal pulse system,
Pulse oscillation can be achieved. Furthermore, since a discharge path is always formed in the lamp and light can be emitted in a low impedance state, the voltage applied to the lamp can be lowered at the same time.
That is, when the pulse output and the frequency are considered to be constant, the average value of the energy input to the lamp decreases. Therefore, according to the present invention, it is possible to increase the repetition frequency of the pulse current within the input limit of the lamp.

Further, in FIG. 10, the case where the simmer current and the pulse current are superimposed and supplied to one lamp is shown, but as shown in FIG. 11, the simmer current and the pulse current are superimposed and supplied. When the YAG rod is excited by two lamps, the excitation input increases more than the case of one lamp,
As a result, a high laser output can be obtained.

[Example] (1) Using an apparatus as shown in FIG.
The edge of the metal foil of m is 30
%, The pipe was shaped so that the abutting angles of the ends were 0.3 ° to 5 °, and welding was performed using a YAG laser that emits a modulated output by superimposing a pulse laser output on a continuous laser output.

The procedure of the fatigue test in the above example is as follows. An ultra-thin metal foil pipe welded as shown in Fig. 7 was cut into a strip of W: 10mm ×: 40mm to include the weld bead, and the corner curvature R was 0.5mm as shown in Fig. 8. It is sandwiched so that the welding bead follows the corners of two steel plates, and is repeatedly bent back and forth by 90 degrees. As a reference, the same experiment is performed on the base material of ultra-thin metal foil.

i) A stainless steel SUS304 (sheet thickness 0.10 mm) emits a modulated output by superimposing a pulsed laser output on a continuous laser output.
When the welding was carried out by irradiating the YAG laser on the surface of the plate with a beam diameter of 1 mmφ, a pulse peak output of 200 W, a continuous output of 80 W, and an average output of 100 W, where the pipe butt gap was 0.2 mm and welding was carried out, it melted down. Welding speed without defects
Obtained at 3.0 m / min. Also, the bead thickness is 12
It was 0% or less, and when a pipe welded portion was cut out and a fatigue fracture test by repeated bending was performed, it was 50.
Good results were obtained more than once.

ii) Similar to the above, a YAG laser that emits a modulated output by superimposing a pulsed laser output on a stainless steel plate SUS304 (plate thickness of 0.05 mm) is a beam diameter of 1 mmφ on the plate surface, a peak output of 150 W, and a continuous output. Part output 40W, average output 5
Welding was performed at 0 W at a butt gap of the pipe of 0.2 mm, and welding with no burn-through defect was obtained at a welding speed of 2.5 m / min. The bead thickness was 120% or less of the base metal thickness, and when the pipe welded portion was cut out and subjected to a fatigue fracture test by repeated bending, a favorable result of 50 times or more was obtained.

iii) For comparison of weldability with conventional method, SUS3 with 100 μm thickness
04 Flat plate materials were butt welded by TIG welding (because it was impossible to weld ultra-thin metal foil pipes with a plate thickness of 100 μm and 50 μm with TIG welding), and a similar repeated bending fatigue test was performed. The number of fractures is 70, and the number of fractures in TIG welds is 35
It was found that the laser welding method was superior in weldability compared to the TIG welding method.

iv) When the bead width of the welding was measured in the above example, the bead width obtained by butt-welding a SUS304 flat plate material having a plate thickness of 100 μm by TIG welding was about 400 μm. However, according to the method using the YAG laser according to the present invention, And the bead width is about 100μ
It became m and 1/4.

(2) Laser beam diameter of 1.
Under the conditions of 0 mmφ and YAG laser output of 30 W, the modulation output Y of the present invention
A bead-on test was performed with an AG laser and a continuous output YAG laser. In the modulated output YAG laser, the range in which a good bead was obtained was 2.5 m / min to 3.1 m / min, while in the continuous output YAG laser, the same range was 2.9 m / min to 3.1 m / min. The bead-on test using the modulated output YAG laser was more than twice as good as the bead-on test using the continuous output YAG laser, and good beads could be obtained over a wide range (Fig. 9). This means that even under welding conditions where continuous output YAG laser melts down and humping occurs, it can be prevented by using a modulated output YAG laser.

[Effect of the Invention] The following effects can be obtained by the method and apparatus of the present invention.

By irradiating a modulated output YAG laser with a low-density focused beam to the places where the grooves on both ends of the ultra-thin metal foil are open, a plate thickness of 150μ, which was not possible with the conventional TIG welding method or laser welding method.
Butt welding of ultra-thin metal foils of m or less can be performed without melting defects such as humping and welding defects.

By irradiating the modulated output YAG laser with a low-density focused beam where the grooves on both ends of the ultra-thin metal foil are opened, the contact area becomes wider than when melting the ultra-thin metal foil at the butt point. So offset condition (previously 10% of plate thickness
The following) can be relaxed.

With the modulated output YAG laser, welding can be performed under the welding conditions such as burn-through and humping that occur in the conventional laser welding method without causing them.

As described above, according to the present invention, the welding of the pipe of the ultra-thin metal foil which has not been obtained in the past can be stably obtained without melting and welding defects.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of forming an ultrathin metal foil into a steel pipe. FIG. 2 is a perspective view showing the concept of the irradiation method and the condensed state of the YAG laser beam. FIG. 3 is a plan view of FIG. FIG. 4 is a conceptual diagram of the output characteristics of the modulated output YAG laser of the present invention. FIG. 5 is a schematic diagram showing relaxation of forming conditions during forming / welding of an ultrathin metal foil to a pipe according to the present invention. FIG. 6 is a schematic diagram of an example of an apparatus used for implementing the present invention. 7 (a) and 7 (b) are a side view and a front view of the test piece used in the examples. FIG. 8 is a front view of the experimental mode of the embodiment of the present invention. FIG. 9 is a graph showing the results of the bead-on test of the example of the present invention. FIG. 10 is a block diagram of an exciting lamp power supply circuit of a modulation output YAG laser oscillator according to the present invention. FIG. 11 shows 2 used in the embodiment of the present invention.
It is a schematic diagram which shows the laser structure using the lamp of a book. 1 ... Ultra-thin metal foil, 2 ... Edge, 3 ... Edge, 4 ... Modulation output YAG laser irradiation position, 5 ... Modulation output YAG laser beam, 6 ... Lens, 7 ... Low density condensing Modulation output YAG laser beam, 8 …… Change output YAG laser beam spot, 9 …… Welding position, 10 …… Melting state part, 11 …… Welding bead, 18 …… SCR control circuit Constant current control part, 19 …… Trigger Generator circuit, 20 ... Boost voltage generator circuit, 21 ... Pulse oscillator, 22 ... FET, 23 ... Pulse transformer, 24 ... Y
AG rod, 25 ... Arc lamp, 26 ... Elliptical concentrator, 27
…… Resonator rear mirror, 28 …… Resonator output mirror, 29…
... constant current lamp power supply, D ... irradiation spot diameter, d ... melting width, g ... groove gap, P _C ... modulation output continuous oscillation part output value, P _P ... modulation output pulse part peak output value, P _av ...
... Modulation output average output value.

Claims (3)

[Claims] 1. An ultra-thin metal foil pipe using a YAG laser for continuously forming an ultra-thin metal foil, converging opposing butting end faces into a wedge shape, and irradiating a laser beam in the vicinity of the converging portion to weld the abutting portion. In the manufacturing method of, a modulated output is generated by superimposing a pulsed laser output on a continuous laser output.
A method for manufacturing an ultra-thin metal pipe using a modulated output YAG laser, which is characterized by welding with a YAG laser. 2. The low-density focused YAG laser beam is irradiated with its center aligned with a point where the gap of the wedge-shaped portion becomes 1 to 5 times the sheet thickness of the ultrathin metal foil, and the sheet thickness starts from the edge. 2. A method for producing an ultra-thin metal pipe by a modulation output YAG laser according to claim 1, wherein a region 2 to 10 times larger than that of FIG. 3. An ultrathin metal foil pipe comprising a forming device for continuously forming an ultrathin metal foil and converging opposing end faces into a wedge shape, and a welding device for irradiating the wedge-shaped portion with a laser. In the device, a simmer power supply unit including a lamp ignition trigger circuit connected in parallel to each lamp and a pulse power supply unit via a pulse transformer for suppressing interference are provided, and a pulse laser output is provided as a continuous laser output. A low-density YAG laser oscillator that emits a modulated output that superimposes
An apparatus for manufacturing an ultra-thin metal pipe using a YAG laser, which is provided with an optical system for irradiating with a laser beam.