JPH10113782A - Laser beam welding equipment and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the depth of penetration as same as the normal pulse welding and to reduce the welding defect of bead crack, etc., by repeatedly irradiating on a material with a pulse group composed of plural numbers of laser pulse having a specific interval in a longer interval than its interval. SOLUTION: A normal pulse is, at least, bi-sected, a wave form arranging plural numbers of divided pulse 101 in a row of 0.3 to 1.0 mil-second interval is made as one of pulse group 102, welding is executed by repeatedly irradiating on a material to be welded with this pulse group 102 in the interval as same as the normal pulse. Because this laser welding method is executed to weld while irradiating with plural numbers of high peak output short pulse 102, before the heat of former pulse being escaped, the next pulse is made to be irradiated, so in locally viewing, rapid heating and rapid cooling are relaxed and welding defect is reduced. Figure a is an example of bi-secting pulse, and Figure b is the example of tripartite pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus and method, and more particularly to a laser processing apparatus and method for welding a workpiece using a pulsed solid laser beam.

[0001]

2. Description of the Related Art Heretofore, as a welding process using a solid-state laser beam such as a yag (YAG) laser beam of this kind, conventionally, "Current status and future technology of laser welding" (March 1994, Laser Thermal Processing Research Group) As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, pulse welding for irradiating rectangular waves at regular intervals or CW welding for irradiating laser light with continuous oscillation (CW) is performed. Here, the oscillation waveform of the laser beam when performing pulse welding is shown in FIG.
FIG. 4B shows the oscillation waveform of the laser beam when performing CW welding.

[0002] In addition, in a welding process for a member such as an aluminum alloy or a galvanized steel plate, which is likely to cause welding defects,
The laser oscillation waveform is devised to make the rising gradual, as shown in FIG. 4C, a method of reducing the welding defect by making the falling gradual, and a quasi-C
A method has been proposed in which pulse oscillation is performed as the W mode, and as shown in FIG. 4D, a welding defect is reduced by controlling the waveform of the quasi-CW mode.

Further, "LAMP '92 Vol. 1"
(June 1992), a method of reducing welding defects by superimposing a CW laser beam and a pulsed laser beam has also been proposed.

[0004]

However, the conventional laser processing apparatus has the following problems.

[0005] That is, in the welding by the YAG laser beam, the above-described pulse welding can obtain the best fusion depth and welding speed with respect to the average output. However, in this pulse welding, rapid heating and quenching are repeated at the welding site. Welding defects are likely to occur.

[0006] As a method of reducing the welding defect, waveform control is performed to mitigate the rising and falling of the pulse so as to mitigate the rapid heat quenching.
In the case of using such a waveform control, a rising or falling waveform is added to a normal pulse in order to obtain a melting depth equivalent to that of a pulse laser, and the energy of one pulse is increased. There is a problem that heat input to the welding member is increased and thermal strain is generated, or the number of pulse repetitions is reduced and the welding speed is reduced.

Further, in the welding method in which the CW laser beam and the pulse laser beam are superimposed on each other, the CW waveform is added to the pulse waveform, so that the average output of the laser beam increases, and as a result, heat input to the welded member And the thermal strain increases.

[0008]

In order to solve the above problems, a laser processing apparatus according to the present invention is a laser processing apparatus for processing a material by irradiating a pulse laser beam emitted from a laser oscillator, A pulse group constituted by a plurality of laser pulses having an interval of 0.3 to 1.0 millisecond is repeatedly irradiated on the substance at intervals longer than the interval.

A laser processing apparatus according to the present invention is a laser processing apparatus for processing a substance by irradiating a pulsed laser beam emitted from a laser oscillator, wherein a waveform of power supplied to an excitation lamp provided in the laser oscillator is provided. Means for comparing a power control signal for controlling the power supplied to the excitation lamp and means for shaping a waveform of power to be supplied to the excitation lamp, according to a comparison result, The power control signal is sent from the laser oscillator at an interval of 0.3
A pulse group composed of a plurality of laser pulses of up to 1.0 millisecond is set so as to be repeatedly irradiated at intervals longer than the above-mentioned interval.

The laser processing method of the present invention is a laser processing method for processing a substance by irradiating a pulsed laser beam emitted from a laser oscillator, wherein the interval is 0.3 to 1.
A pulse group composed of a plurality of laser pulses of 0 millisecond is repeatedly irradiated on the substance at intervals longer than the interval.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a laser processing apparatus and method according to the present invention will be described in detail with reference to the drawings.

In the laser processing method of this embodiment, a normal pulse is divided into at least two pulses, and a plurality of divided pulses (hereinafter referred to as divided pulses) are arranged at intervals of 0.3 to 1.0 ms. The resulting waveform into one pulse group,
Welding is performed by repeatedly irradiating the pulse group to the workpiece at the same interval as a normal pulse. Here, a pulse YAG laser usually has a pulse width of 3
ms and a pulse interval of 47 ms, and a pulse width of 1 ms and a pulse interval of 9 ms. In the case where a pulse is generated by pulse-modulating a CW · YAG laser, there are a pulse width of 2.5 ms and a pulse interval of 2.5 ms, and a pulse width of 10 ms and a pulse interval of 20 ms.

According to this embodiment, since welding is performed while irradiating a plurality of short pulses having a high peak output, the next pulse is radiated before the heat of the previous pulse escapes. When seen, rapid heat quenching is alleviated, and welding defects can be reduced. The interval between divided pulses is 1.0 m
If it exceeds s, the next pulse is irradiated after the heat of the previous pulse has almost completely escaped. 0.3m
If it is shorter than s, a plurality of divided pulses become equivalent to one thermally continuous pulse. Therefore, it is preferable that the interval between the divided pulses is set within the range of 0.3 to 1.0 ms.

FIGS. 1A and 1B are diagrams showing the waveform of a pulse laser beam used in the present embodiment, in which a normal pulse is divided into two parts (see FIG. 1A) or three parts (see FIG. 1A). 1 (b)), and each divided pulse 10
One pulse group 102 is formed by waveforms each of which is arranged at intervals of 0.3 to 1.0 ms. The workpiece is irradiated with the pulse group 102 at an interval equivalent to that of a normal pulse, and welding is performed.

Each of the divided pulses 101 divided into two or three does not need to have the same pulse width, and the pulse width of each divided pulse 101 in one pulse group 102 is changed according to the processing conditions. You may change each.

Further, in order to make heat input by a normal pulse and heat input by a pulse group 102 composed of a plurality of divided pulses 101 equal, only the amount of heat that escapes due to a pause inserted between the divided pulses 101 is used. , Each divided pulse 101
May be corrected. For example, a normal pulse having a pulse width of 3.0 ms is irradiated at a peak output of 5 kW to perform welding. In the present embodiment, a divided pulse 101 having a pulse width of 1.5 ms is irradiated at an equivalent peak output. Then, the divided pulse 101 having a pulse width of 1.5 ms is applied with a pause of 0.5 ms. Here, even if the total pulse energies are the same, the escape of heat for 0.5 ms causes escape of heat, so that a penetration depth equivalent to that of a normal pulse cannot be obtained. Experimentally, energy escape for normal pulses is a few percent
It is about 10%, and it is necessary to compensate for this heat escape depending on the processing conditions. For this purpose, a method of correcting the pulse width of the divided pulse 101 or its peak output is implemented. Specifically, the divided pulse 101 divided into two as described above is divided into a pulse 101 having a pulse width of 1.6 ms.
, Or the peak output of the divided pulse 101 is set to 5.5 kW without changing the pulse width.

In this embodiment, FIG. 1A or FIG.
A pulse group 102 composed of a plurality of divided pulses 101 as shown in (b) is repeatedly irradiated on a workpiece at the same interval as a normal pulse. The waveform of this pulse group 102 is It is not limited.

For example, as shown in FIG. 2 (a) or FIG. 2 (b), a pulse group 102 whose waveform is controlled so that the falling portion or rising portion of all divided pulses 101 becomes gentle is repeatedly applied. The workpiece may be irradiated. Depending on the processing conditions, the waveform may be controlled so that both the falling edge and the rising edge of the divided pulse become gentle.

Further, as shown in FIG. 2C, a plurality of divided pulses 101 forming one pulse group 102 are provided.
The workpiece may be repeatedly irradiated with a pulse group 102 whose waveforms are controlled so that the pulse widths of the pulses become different from each other. In this example, the pulse width of the first-stage divided pulse 101 is larger than the pulse width of the second-stage divided pulse 101. Conversely, the pulse width of the second-stage divided pulse 101 is smaller than that of the first-stage divided pulse 101. The waveform may be controlled so as to be larger than the above.

Further, as shown in FIG. 2D, a plurality of divided pulses 101 forming one pulse group 102 are formed.
May be repeatedly irradiated on the workpiece with the pulse group 102 whose waveforms are controlled so that the peak outputs of the pulses have different values. In this example, the peak output of the divided pulse 101 at the preceding stage is larger than the peak output of the divided pulse 101 at the subsequent stage. Conversely, the peak output of the divided pulse 101 at the subsequent stage is set to be larger than that of the divided pulse 101 at the preceding stage. Waveform control may be performed so as to increase.

Further, in the examples shown in FIGS. 2A to 2D, only the waveform in the case where the normal pulse is divided into two has been described, but the normal pulse is naturally divided into three or more. Needless to say, the present invention can be applied to the case of division. Further, a divided pulse or a pulse group may be shaped into a waveform obtained by combining these waveforms. Further, the pulse width and the peak output of the divided pulses constituting the pulse group may be changed for each pulse group repeatedly irradiated.

Next, the configuration of the laser processing apparatus of the present embodiment will be described with reference to FIG.

Referring to FIG. 3, the power supplied from power supply 301 is an IGBT (Insulated-Gate).
The waveform is shaped by a semiconductor switch element 302 such as a Bipolar Transistor according to the signal from the comparator 303. Since the shaped power includes a high-frequency component when supplied from the power supply 301, the high-frequency component is smoothed through the filter 304 and shaped into a desired waveform. The electric power shaped into a desired waveform is supplied to the excitation lamp 305,
Is turned on, a pulsed solid laser (not shown) is oscillated according to a desired waveform. At this time, the excitation lamp 30
5 is measured by a voltmeter 306 and an ammeter 307, respectively, and the power supplied to the excitation lamp 305 is detected by the power detection circuit 308 based on the measurement results. The difference between the detected waveform shape of the power supplied to the excitation lamp 305 and the waveform shape of the power control signal 309 externally supplied to the comparator 303 is calculated by the comparator 303, and a signal corresponding to the difference is sent to the IGBT 302. . By feeding back the power supplied to the excitation lamp 305 in this way, the pulsed solid-state laser is oscillated according to the power control signal.

In the present embodiment, a normal pulse corresponds to FIG.
By supplying a power control signal 309 set to be shaped into the divided pulses shown in FIGS. 2A and 2B or FIGS. 2A to 2D to the comparator 303, a desired waveform can be obtained. A group of pulses can be obtained.

[0025]

As described above, according to the laser processing apparatus and method according to the present invention, it is possible to obtain a welding depth substantially equal to that of pulse welding with an average output and a welding speed substantially equal to those of ordinary pulse welding. And welding defects such as beat cracks can be reduced.

In order to irradiate a plurality of divided pulses within a short time, the melted portion is agitated by the reaction force of laser irradiation at the melted portion at the time of irradiation of each divided pulse, and the bias of the components of the melted portion is reduced. You. Therefore, welding defects such as cracks due to uneven components of the fusion zone are also reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pulse waveform of a pulse laser according to an embodiment of the present invention.
FIG. 3B shows a pulse waveform when the pulse is divided, and FIG. 4B shows a pulse waveform when a normal pulse is divided into three.

FIGS. 2A and 2B are diagrams showing another pulse waveform in one embodiment of the present invention, and FIG. 2A is a diagram showing a pulse waveform shaped so that the falling edge of a divided pulse becomes gentle; () Is a diagram showing a pulse waveform shaped so that the rising of the divided pulse becomes gentle, and FIG.
FIG. 3 is a diagram showing pulse waveforms when the pulse widths of a plurality of divided pulses constituting one pulse group are different from each other, and FIG. 4 (d) is a diagram showing each of a plurality of divided pulses constituting one pulse group. FIG. 7 is a diagram illustrating a pulse waveform when a peak output is set to a different value.

FIG. 3 is a diagram illustrating a configuration of a laser processing apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing a waveform of a conventional laser pulse.

[Explanation of symbols]

 Reference Signs List 101 pulse group 102 pulse group 301 power supply 302 IGBT 303 comparator 304 filter 305 excitation lamp 306 voltmeter 307 ammeter 308 power detection circuit 309 power control signal

Claims (8)

[Claims] 1. A laser processing apparatus for processing a substance by irradiating a pulse laser beam emitted from a laser oscillator, comprising a plurality of laser pulses having an interval of 0.3 to 1.0 millisecond. A laser processing apparatus, wherein a pulse group is repeatedly irradiated on the substance at intervals longer than the interval. 2. The laser processing apparatus according to claim 1, wherein the pulse group is formed by arranging two or three laser pulses at the intervals. 3. The laser processing apparatus according to claim 1, wherein the plurality of laser pulses constituting the pulse group have different pulse widths. 4. The laser processing apparatus according to claim 1, wherein the plurality of laser pulses forming the pulse group have different peak outputs. 5. A laser processing apparatus, wherein the waveform of the plurality of laser pulses is gently shaped at least one of its falling edge and rising edge. 6. A laser processing apparatus for processing a substance by irradiating a pulse laser beam emitted from a laser oscillator, comprising: a power control signal for controlling a waveform of power supplied to an excitation lamp provided in the laser oscillator. Means for comparing the power supplied to the excitation lamp, and means for shaping the waveform of the power to be supplied to the excitation lamp in accordance with the comparison result. The laser processing apparatus is set so that a pulse group composed of a plurality of laser pulses having an interval of 0.3 to 1.0 millisecond is repeatedly irradiated at an interval longer than the interval. 7. A laser processing method for processing a substance by irradiating a pulse laser beam emitted from a laser oscillator, comprising a plurality of laser pulses having an interval of 0.3 to 1.0 millisecond. A laser processing method, wherein a pulse group is repeatedly irradiated on the substance at intervals longer than the interval. 8. The laser processing method according to claim 6, wherein at least one of a pulse width and a peak output of the plurality of laser pulses is changed according to processing conditions.