JPH044987A - Method and apparatus for producing extremely thin metal pipe with modulated output yag layer beam - Google Patents

Abstract

PURPOSE:To eliminate welding defect of melt-down and humping by welding an extremely thin metal pipe with YAG laser beam generating a modulated output superimposing pulse laser beam output to continuous laser beam output. CONSTITUTION:The extremely thin metal foil 1 is continuously formed to pipe- state and the faced butting end faces 2 are converged to wedge-shape and center of the laser beam is made to coincide with the point, which gap 3a, 3b at near the converged point 4 becomes 1-5 times the foil thickness, and irradiated to melt the range of 2-10 times the foil thickness from edge part and the molten end face is pushed just before solidifying and welded. By using the modulated output superimposing the pulse laser beam output to the continuous laser beam output, at the time of non-molten condition on surface of the metal foil 1, the high energy at the pulse part in a ripple output is radiated to instantaneously come to the molten condition. Successively, the output is lowered to the continuous output part to prevent over-melting. The welding is executed to the extremely thin pipe without developing welding defect.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the production of YAG
This invention relates to a method for manufacturing pipes by laser welding and an apparatus therefor.

[Prior art] Continuously forming ultra-thin metal foil into a tubular shape, converging the opposing end faces into a wedge shape, and performing electric welding such as TIG in the vicinity of the convergence point is a method of welding the pipe edge end face at the welding point. It is not suitable for welding ultra-thin metal foils because it requires precise adjustment of conditions such as edge burrs and roughness, - precise adjustment of gap and offset conditions, accurate adjustment of butt, and strict heat input limits. do not have. Furthermore, since the heat-affected zone is large, there is a problem in weldability, making it particularly unsuitable for bending pipes. Furthermore, even in conventional laser welding methods, laser irradiation is required when welding 8i thin metal foil due to accurate adjustment of butt conditions such as edges, gaps, and offsets, and strict heat input limitations. It is technically difficult to accurately limit the position, beam diameter, and power.

In addition, the welding method using a low-density focused YAG laser, as seen in Japanese Patent Application Laid-Open No. 60-96382, aims to alleviate the severe butt conditions mentioned above and also to weld the surface of ultra-thin metal foil. The ratio of the laser absorption rate during non-melting and melting is reduced, the melt falls off, and welding defects such as humping are prevented. However, regarding the prevention of welding defects, as stated in the same publication, the change ratio Ry of the absorption rate α0 in the non-melting state and the absorption rate αY in the melting state of the YAG laser is R,
>2.5, and the absorption rate change ratio Re of the C02 laser
>Although it is sufficiently small compared to II, the absorption rate of the laser input energy key changes by more than twice when it is not melted and when it is melted. When welding objects, even the slightest change in the welding condition greatly affects the welding result, so it cannot be said that this is sufficient to prevent welding defects.

[Problem to be solved by the invention] The present invention solves severe edge conditions that cannot be overcome by electric welding and conventional laser welding methods when ultra-thin metal foil is continuously formed into a tubular shape and welded into a pipe. offset condition,
The purpose of this invention is to overcome the problems of butt conditions and heat input conditions, and to provide a manufacturing method and apparatus that can produce high-quality ultra-thin metal foil pipes with less molten heat-affected layer.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and its gist is to continuously form ultra-thin metal foil and to form opposing butt end surfaces. In an ultra-thin metal foil pipe manufacturing device that converges and welds into a wedge shape, a lamp ignition trigger circuit and a simmer power supply circuit are connected in parallel to the laser excitation lamp, and in order to suppress mutual interference. A laser oscillator that emits a modulated output by superimposing the pulsed laser output on the continuous laser output, and a pulsed current circuit coupled to the lamp through a pulse transformer connected in parallel to the lamp, and a convergence of ultra-thin metal foil. An apparatus for manufacturing an ultra-thin metal foil pipe using a YAG laser, characterized in that it is equipped with an optical system that irradiates a wedge-shaped part formed in a section with a low-density focused beam; In the manufacturing method of an ultra-thin metal foil pipe, the opposing end faces are converged into a wedge shape, and the wedge-shaped portion is irradiated with a laser to weld. Low-density condensing light that emits a modulated output that is a continuous output and a pulsed output superimposed on the gap of the wedge-shaped part held and formed below or at a point that is 1 to 5 times the thickness of the ultra-thin metal foil. In this method, the centers of the YAG laser beams are aligned and irradiated to melt an area 2 to 10 times the thickness of the plate from the end face, and the molten end face is pressed just before solidification to complete welding.

[Function] (1) As shown in Fig. 1, the forming process of the pipe manufacturing method of the present invention involves continuously forming ultra-thin metal foil to converge the opposing butt end surfaces into a wedge shape, and Any forming method can be applied as long as the offset of the edge end face is within 30% of the plate thickness.

(2) Figures 2.3 are conceptual diagrams of a low-density energy beam area soft welding method using a YAG laser oscillator that emits a modulated output in which a pulsed output is superimposed on a continuous output. YAG
Irradiate the laser to the groove gap of the ultra-thin metal foil, which is between 1 and 5 times the plate thickness, and set the irradiation beam diameter to a width of 2 to 10 times the plate thickness on both end faces of the ultra-thin metal foil. The light is focused so that it melts over the area, the melt falls, and welding is performed without humping.

At this time, the width of the fused portions at both ends of the ultra-thin metal foil and the gear length g at both ends are equal to the beam radius of the YAG laser. The beam radius is controlled by the focal length f of the lens or by day focus irradiation, which sets the focal position above the steel plate. If the laser irradiation position is set to a position where the groove gap is less than the value of the plate thickness, it will be the same as irradiating the butt point, and there will be less clumping due to melting at both ends, and the edge offset will be reduced to 10% of the plate thickness. The accuracy must be as follows. This requires very advanced technology for ultra-thin metal foils and is difficult to implement. In addition, at a position beyond the 5 times the plate thickness, both ends are too far apart and cannot be butted together well, making it impossible to perform good welding. In addition, if the welding area from the end face is less than twice the plate thickness, the welding will be insufficient.
If it exceeds 10 times, excessive welding will occur and the melt will drop.

(3) Using a YAG laser to emit a modulated output in which a pulsed output is superimposed on a continuous output has the following advantages. The absorption rate of laser light on the metal surface differs greatly between when it is not melted and when it is molten, which changes the heat input state and causes welding defects when welding ultra-thin metal foils. Therefore, as seen in Japanese Patent Application Laid-Open No. 60-96382, a YAG laser is used to reduce the ratio of the absorption rate of the laser during non-melting and melting on the surface of ultra-thin metal foil, so that the melt falls off and welding such as humping is reduced. A method for preventing defects is disclosed. However, regarding the prevention of welding defects, as written in the same publication, the absorption rate α of the YAG laser when not melting. , the change ratio R, of the absorption rate α during melting is about R,>2.5, and Co2
Although this is sufficiently small compared to the laser absorption rate change ratio Re > 11, there is no difference in the fact that the absorption rate of the laser input energy changes by more than twice when it is not melted and when it is melted. When welding materials with small heat capacity, such as small welding conditions, slight changes in welding conditions can greatly affect the welding result, so it is extremely difficult to control the laser input energy to the optimal conditions because the control range is narrow. It cannot be said that this is sufficient to prevent welding defects.

On the other hand, by using a YAG laser with ripple output in which pulse output is superimposed on continuous output according to the present invention, the conditions for optimal control of the laser input energy as described above can be relaxed. FIG. 4 schematically shows the modulated YAG laser of the present invention. Pp indicates the peak output value of the pulse portion of the modulated output, PC indicates the output value of the continuous oscillation section of the modulated output, and pav indicates the time average value of the modulated output. Its action is as follows. When the metal foil surface is in a non-molten state, the high energy of the pulse portion of the ripple output is irradiated to instantly bring the metal foil surface into a molten state. Thereafter, when the molten state is reached and the absorption rate of the laser beam reaches an efficiency of 0.9 or more, the laser output of ripple oscillation is changed from the peak value Pp of the pulse part of the ripple output to P of the continuous output part according to the change in the absorption rate. By reducing the change to Furthermore, when the surface of the ultra-thin metal foil begins to solidify and the absorption rate of the laser beam decreases, the high energy of the pulse portion of the ripple output is applied again to keep the surface of the ultra-thin metal foil in a molten state. The energy density of the pulse portion is high and always forms a melting nucleus on the surface, but the amount of heat input by this is small and does not become heat input.

By repeating the above-mentioned molten solidification at a high speed, the molten metal falls onto the ultra-thin metal foil, making it possible to perform stable welding without welding defects such as humping. In this way, the control range of laser input energy is widened, making it possible to easily weld ultra-thin metal foil.

(4) The relaxation of the forming conditions by the surface heat source welding method using a low density energy density system is due to the following reasons.

■ By irradiating the laser at the gap g in Figure 2, which is about twice the thickness of the plate, the contact area will be wider than when melting ultra-thin metal foil at the butting point (Figure 5). The offset condition (10% or less of the plate thickness) is relaxed.

■ Even if the condition of the butt point (overlapping condition of both ends of the ultra-thin metal foil) changes slightly, heat can be input without being affected by the subtle change in heat capacity, resulting in no pinking or melting. can perform welding without welding. By this method, the allowable values for gaps and offsets (10% or less of the plate thickness) can be greatly expanded (2 to 3 times).

(5) FIG. 10 shows a block diagram of an excitation lamp power supply circuit for a laser oscillator according to the present invention.

The lamp includes an ignition trigger generation circuit, a simmer power supply circuit,
Pulse current circuits are connected in parallel.

The functions of each part lock are shown below.

・SCR*J control circuit constant current control section】8 Supplies simmer current to the lamp. This maintains the conductive state of the lamp and excites the YAG rod to a level near or above the laser oscillation threshold.

- Trigger generation circuit 19 Generates a high-voltage trigger to form a discharge path in the lamp at the start of lamp lighting.

- Boost voltage generation circuit 20 This circuit supplies a boost voltage that maintains the discharge path in the lamp formed by the trigger until the simmer power supply is turned on.

・Pulse R1 section 21, FET 22 and pulse transformer 2
3 (PT) Controls the pulse current supplied to the lamp. Pulse current is controlled by FET22, and pulse transformer 23 (PT)
It is supplied to the lamp through the

・Reverse current prevention diode (DI, D2) Stabilizes the simmer current against lamp impedance fluctuations due to simmer current discharge.

・Vacuum relay (RYI) Cuts off and protects 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 explained. The basic principle of pulse oscillation itself is similar to the normal pulse method, or in the present invention, the YAG lot is excited in advance by a simmer current to a level near the laser oscillation threshold or higher. Therefore, in the present invention, pulse oscillation can be achieved by superimposing a lower pulse current value than in the conventional normal pulse method. Furthermore, since a discharge path is always formed within the lamp and light can be emitted in a low impedance state, the voltage applied to the lamp can also be lowered at the same time. That is, if the pulse output and frequency are considered constant, the average value of the energy applied 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.

In addition, although Fig. 10 shows the case in which a single lamp is supplied with a simmer current and a pulse current in a superimposed manner, as shown in Fig. 11, the simmer current and pulse current are also supplied in a superimposed manner. When a YAG lot is excited with two lamps, the excitation power is increased compared to when one lamp is used, and as a result, a higher laser output can be obtained.

[Example] (1) Using an apparatus as shown in FIG.
A 0 μm metal box is formed into a pipe shape with an edge offset of less than 30% of the thickness of the ultra-thin metal foil and a butting angle of 0.3° to 5°, and pulsed with continuous laser output. Welding was performed using a YAG laser that emits a modulated output that is superimposed with laser output.

The procedure of the fatigue test in the above example is as follows. As shown in Fig. 7, welded ultra-thin metal foil pipes are welded so that the welded bead is included W: ]0++unX: 40
Cut it into a rectangular shape of mm, and adjust the corner curvature R as shown in Figure 8.
The weld bead follows the corner of two steel plates with a diameter of 0.5 mm, and the edges are bent 90 degrees in front and back. As a reference, the same experiment will be performed on a base material of ultra-thin metal foil.

i) Stainless steel plate 5US304 (plate thickness 0.IOmm
) is a YAG laser that emits a modulated output that is a continuous laser output superimposed with a pulsed laser output.
ffImφ, pulse part peak output 200W, continuous output part output 80W, average output 100W, when welding was carried out by irradiating the butt gap of the pipe at 0.2 mrn, the weld was welded without any welding defects. Speed 3.0
m/min. In addition, the thickness of the bead is 120% or less of the base metal thickness, and when a pipe welded part was cut out as a sample and a fatigue fracture test was performed by bending the welded pipe over 50 times, good results were obtained.

ii) A YAG laser that emits a modulated output by superimposing the pulsed laser output on the continuous laser output is applied to the above and the four-building stainless steel plate 5IJS304 (plate thickness 0.05 mm) with a beam diameter i nunφ at the plate surface and a pulse part peak output of 150 mm.
W, continuous output part output 40W, average output 50W, when welding was carried out by irradiating the butt gap of the pipes at 0.2 + nm, welding fell and there was no defect or welding at a welding speed of 2.5m/min. Obtained. In addition, the thickness of the cord is 120% or less of the base metal thickness, and when a pipe welded part was cut out as a sample and subjected to a fatigue fracture test by drawing back and bending it over 50 times, good results were obtained.

1ii) For weldability comparison with the conventional method, the plate thickness was 100 μm.
5 US304 flat plate material was butt welded by TIG welding.The plate thickness was 100 um, 501. As it was impossible to weld the ultra-thin metal foil pipe of Im), when we conducted a fatigue test on bending the edges of the same mori, the base metal part fractured 70 times and the TIG weld part fractured 35 times. It was found that laser welding is superior to TIG welding in terms of weldability.

iv) In the above example, when the welding beat width was measured, the 5LIS104 flat plate material with a plate thickness of +00 um was TI
The bead width when butt welded using G welding is approximately 400μm.
However, according to the method using a YAG laser according to the present invention, the width of one dot was reduced to one-fourth of that, to about 100 μm.

(2) Laser beam diameter 1.0 mmφ, YAG laser output 30 W for S [l5304 foil with plate thickness 50 g I + l
Under the conditions of the modulated output YAG laser of the present invention and the continuous output Y
A bead-on test was performed using an AG laser. The range in which a good bead can be obtained with a modulated output YAG laser is 2.5
m/min~3 and 1m/min, whereas continuous output YAG laser has the same range or 2.9m/min~3
．． ] m/min, and the heat-on test using the modulated output YAG laser of the present invention was able to obtain good beads over a wider range more than twice that of the beat-on test using the continuous output YAG laser (FIG. 9). This thing is
This means that even under welding conditions where a continuous output YAG laser would cause melt drop and humping to occur, using a modulated output YAG laser can prevent this.

[Effects 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 open grooves at both ends of ultra-thin metal foil, welding with a thickness of 150 μm or less, which was not possible with conventional TIG welding or laser welding. Butt welding of ultra-thin metal foils can be performed without melting and welding defects such as humping.

■ By irradiating the modulated output YAG laser with a low-density focused beam to the open grooves at both ends of the ultra-thin metal foil, it is possible to achieve a ratio of contact range when melting the ultra-thin metal foil at the butting point. Since it becomes wider, the offset conditions (conventionally, 1 of the board thickness)
0% or less).

- Modulated output YAG laser allows welding to be carried out without causing humping, etc., even under welding conditions where the melt drops and humping occurs in conventional laser welding methods.

As described above, according to the present invention, welding of extremely thin metal foil pipes, which could not be achieved conventionally, was achieved stably without melting and without causing any welding defects.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of forming an ultra-thin metal foil into a steel pipe. FIG. 2 is a perspective view showing the convergence state of the YAG laser beam and the concept of the irradiation method. FIG. 3 is a plan view of FIG. 2. 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 the forming conditions when forming and welding an ultra-thin metal foil into a pipe according to the present invention. FIG. 6 is a schematic diagram of an example of equipment used to implement the present invention. FIGS. 7(a) and 7(b) are a side view and a front view of the test section used in the example. FIG. 8 is a front view of an experimental mode of an embodiment of the present invention. FIG. 9 is a graph showing the results of a bead-on test of an example of the present invention. FIG. 10 is a block diagram of a pumping lamp power supply circuit for a modulated output YAG laser oscillator according to the present invention. FIG. 11 is a schematic diagram showing a laser structure using two lamps used in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Ultra-thin metal foil, 2... End part, 3... End surface, 4
...Variable output YAG laser irradiation position, 5...Modulated output YAG laser beam -16...Lens, 7...Low density focused modulated output YAG laser beam, 8...Change output YAG laser beam Spot, 9...Welding position, 1
0... Molten state part, 11-... Welding beat, 18...
- SCR control circuit constant current control section, 19... trigger generation circuit, 20... boost voltage generation circuit, 21...
Pulse oscillation unit, 22--FET, 23-- Pulse transformer, 24-- YAG rod, 25-- Arc lamp, 26-- Elliptical condenser, 27-- Resonator rear mirror 28--・Resonator output mirror 29...constant current lamp power supply, D...irradiation spot diameter, d...melting width, g...groove gap, PC...modulation output continuous full oscillation part output value, Pp...Modulation output pulse part peak output value,
p a. ...Modulation output average output value.

Claims (1)

[Claims] 1. Using a YAG laser that continuously forms ultra-thin metal foil, converges the opposing abutting end surfaces into a wedge shape, and irradiates a laser beam near the convergent portion to weld the abutting portions. A method for manufacturing an ultra-thin metal foil pipe using a modulated output YAG laser, characterized in that welding is performed using a YAG laser that emits a modulated output in which a pulsed laser output is superimposed on a continuous laser output. 2. Align the center of the low-density focused YAG laser beam to the point where the gap of the wedge-shaped part is between 1 and 5 times the thickness of the ultra-thin metal foil, and irradiate it from the edge to the point where the gap is between 2 and 5 times the thickness of the ultra-thin metal foil. 2. The method for manufacturing an ultra-thin metal pipe using a modulated output YAG laser according to claim 1, wherein an area 10 times larger is melted and the molten end face is pressed and welded immediately before solidification. 3. An ultra-thin metal foil pipe manufacturing device comprising a forming device that continuously shapes ultra-thin metal foil and converges opposing butt end surfaces into a wedge shape, and a welding device that irradiates the wedge-shaped portion with a laser. , a lamp ignition trigger circuit and a simmer power supply circuit each connected in parallel to the lamp, and a pulse current circuit connected via a pulse transformer connected in parallel to the lamp in order to suppress mutual interference. a laser oscillator that emits a modulated output in which pulsed laser output is superimposed on continuous laser output, and an optical system that irradiates a wedge-shaped part formed at the convergence part of the ultra-thin metal foil with a low-density focused YAG laser beam. YA characterized by having
Equipment for manufacturing ultra-thin metal pipes using G laser.