JP2002316282A - Laser beam machining method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a conventional problem of increasing welding speed of aluminum alloy, a problem of inferior absorption characteristic of aluminum at the wavelength in the welding of aluminum alloy, making the effective use of laser beam energy difficult for welding, and the ineffective utilization of only 1-6% of laser output. SOLUTION: A first laser 1, which is pulse-oscillated to have a peak power for melting the surface of a workpiece, is emitted to the workpiece, a second laser 2, which has a peak power smaller than that of the first laser and which is larger in the irradiation time, is emitted to the same place as the first laser 1 and timing for starting the irradiation is adjusted between the first and the second laser 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a difficult-to-process material such as aluminum or an aluminum alloy (hereinafter simply referred to as an aluminum alloy) at a high speed by using a laser beam.

[0002]

2. Description of the Related Art Conventionally, TIG welding, MIG welding, plasma welding, and laser welding are generally used for welding aluminum alloys, which are a type of difficult-to-process materials. But,
In TIG welding, MIG welding, and plasma welding, heat input is large and thermal energy is spread over a wide range, so that a large thermal strain is generated in a welding member.

On the other hand, in laser welding, since the energy of a laser beam is locally focused and welding is performed at a high energy density, welding distortion is small and high quality welding can be performed. For example, a carbon dioxide laser and a Nd: YAG pulse laser are used for welding an aluminum alloy using a laser beam.

The absorptance of aluminum to a wavelength of 10.6 μm of a carbon dioxide laser is 1 to 2%, and most of the light is reflected. As a result, it is possible to cause a laser beam to be absorbed locally in a processing portion by laser irradiation and to store heat. Difficult, and as for laser welding, it is cited as a difficult-to-work material. However, welding of an aluminum alloy is forcibly performed with a high output using a high output carbon dioxide gas laser of several tens of kW class.

On the other hand, an Nd: YAG laser having a wavelength of 1.06
The absorption rate of aluminum for 4 μm is about 4 to 6%, which is about three times that of a carbon dioxide laser, and energy efficiency is relatively good. In addition, since the wavelength is shorter than that of the carbon dioxide laser, the condensing property of the laser beam is also improved. Further, in recent years, the output of Nd: YAG laser has been increased, and an output of 1 kW or more has been put into practical use. Therefore, Nd: YAG laser is used for welding a high quality aluminum alloy having less heat influence. ing. In particular, an Nd: YAG pulse laser capable of securing a high peak power is used.

[0006] Once the aluminum alloy is melted,
The reflectance at the molten surface decreases, and the absorptance also increases. Therefore, in laser welding of aluminum alloys, first, how to efficiently melt the surface of the aluminum alloy, and then apply the entire aluminum alloy without giving excessive laser power to the molten aluminum alloy The point is to melt.

For this reason, for example, a two-step pulse using waveform control as shown in FIG. 14, that is, a short pulse high peak power first pulse (pulse width: T1, peak power: P1) and a long pulse low peak power Of the second pulse (pulse width: T2, peak power: P2).

[0008]

As described above, in the welding of an aluminum alloy using a carbon dioxide gas laser or a Nd: YAG laser which is currently in practical use, the absorption characteristics of aluminum at that wavelength are poor, and the laser beam is poor. Energy cannot be efficiently used for welding. That is, since only about 1 to 6% of the laser output can be effectively used, the welding speed of the aluminum alloy cannot be increased.

For example, in a carbon dioxide gas laser with a laser output of 1 kW, only 10% to 20 W of 1 to 2% thereof can be used effectively. On the other hand, Nd: YAG pulse lasers have begun to be widely used at manufacturing sites in that they have a high absorptivity to aluminum and can use optical fibers.
However, even with a 1 kW Nd: YAG laser,
%, That is, only 40 to 60 W can be used effectively.

For example, when welding an aluminum alloy with a 500 W class Nd: YAG laser, the welding speed is only about 30 mm / s.

Further, processing by a pulse having a high energy density is required, and a longer time is required for power charging for laser oscillation than in normal processing, and the processing tact is very slow, from several Hz to several tens of Hz. Becomes

Further, poor absorption characteristics mean that the reflectance is very high, and 90% or more of aluminum is reflected. Therefore, in actual laser welding, it is necessary to pay attention to the reflection of the laser beam.

Further, there is a problem regarding the high thermal conductivity which is another feature of the difficult-to-process material. This is when processing
The point is that once the material is melted, processing proceeds at a stretch because of its high thermal conductivity. This is particularly noticeable in the processing of micro-areas, and the progress of processing of difficult-to-process materials is faster than that of materials generally suitable for welding, such as carbon steel and stainless steel. It is difficult to maintain the processing quality such as the size of the processing region and the melting depth in the micro region.

The size of the processing area in the micro area is N
d: In the case of processing by the YAG pulse laser alone, the size of the processing area and the melting depth are in a proportional relationship, and one of them determines the processing conditions, and the size of the processing area and the melting depth required at present are determined. Can't satisfy relationship.

[0015] Specific quality issues relating to micro spot welding include the required depth of fusion of the micro area with respect to the size of the processing area and the gap at the joint of the workpiece. In general, it is considered that joining is considerably difficult if there is a gap of 10% or more of the fusion depth at the joining portion of the workpiece. In particular, when performing spot welding of several hundred micro-sizes, the size allowed for the gap is as small as tens of microns. In order to process a difficult-to-process material, energy higher than that input to the processing of a material suitable for welding is input, so that the processed portion and the peripheral portion of the processed portion are deformed accordingly. This causes or increases the gap in the processing area of the workpiece, and a gap exceeding several tens of microns is formed.

Further, from the viewpoint of the global environment, there is a demand for reduction of power consumption in manufacturing facilities. In this respect, in the conventional welding method of aluminum alloy, only 1% to 6% of the laser energy can be effectively used, and the remaining 90% or more is wasted, which is not good from the viewpoint of power consumption.

[0017]

In order to solve this problem, the present invention provides a method of irradiating a first laser having a peak power for oscillating a pulse and melting a surface of a workpiece to the workpiece, A second laser having a smaller peak power and a longer irradiation time than the first laser is irradiated to the same place as the first laser, and irradiation of the first laser and the second laser is started. The timing is adjusted.

This has the advantageous effect of improving productivity.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on specific examples.

First, the spectral characteristics of aluminum, which is a difficult-to-process material, are evaluated. The spectral characteristics represent the relationship between the wavelength and the energy absorption for a certain material, and indicate how much the material absorbs light of a certain wavelength. FIG. 1 shows the spectral characteristics with respect to aluminum.
For 0 nm (0.6 to 1.0 μm), the absorptance is significantly improved, with an absorptivity of 6 to 14%. This is five times or more the absorption rate as compared with the carbon dioxide gas laser and twice or more as compared with the Nd: YAG laser.

A semiconductor laser is one of the lasers in this wavelength band. The semiconductor laser has a different oscillation wavelength depending on its composition, and generally has a wavelength of 600 to 1000 nm, which is almost the same as the absorption region of aluminum. Further, in recent years, the output of the semiconductor laser itself has been increased, and the output thereof has been increased by the multiplication thereof. As the maximum output, a laser output of several kW has been obtained. However, a high-output semiconductor laser is basically a continuous wave laser, and has a drawback that a high peak power cannot be obtained unlike a Nd: YAG pulse laser.

FIG. 2 shows a laser processing apparatus according to a first embodiment of the present invention. In this figure, an example of lap welding is given as a typical example of welding of an aluminum alloy. In FIG. 2, 1 is a pulse laser, 2 is a semiconductor laser, 3 is a total reflection mirror, 4 is a dichroic mirror, 5 is a condenser lens, 6 and 7 are aluminum alloys to be welded, and 8 is emission from the pulse laser 1. Reference numeral 9 denotes a semiconductor laser beam emitted from the semiconductor laser, and reference numeral 10 denotes a polymerized laser beam in which the pulse laser beam 8 and the semiconductor laser beam 9 are superposed. Also,
The aluminum alloys 6 and 7 to be welded are placed in the holder 1.
The holder 11 is mounted on a one-axis stage 12. In this embodiment, Nd: YAG having an oscillation wavelength of 1064 nm is used as the pulse laser 1.
A laser is used, and pulse oscillation is performed by an acousto-optic device (AOQsw device). As the semiconductor laser 2, a continuous wave semiconductor laser is used, and its oscillation wavelength is 808 nm.

The pulse laser beam 8 emitted from the pulse laser 1 is totally reflected by the total reflection mirror 3. The dichroic mirror 4 transmits at a wavelength of 1064 nm and totally reflects (at a 45-degree incident laser beam) a wavelength of 808 nm. for that reason,
The pulse laser beam 8 having a wavelength of 1064 nm passes through the dichroic mirror 4, and the semiconductor laser beam 9 having a wavelength of 808 nm totally reflects the dichroic mirror 4. Therefore, it passes through the dichroic mirror 4
Each of the reflected laser beams (the pulse laser beam 8 and the semiconductor laser beam 9) is superimposed and becomes a superimposed laser beam 10. This polymerized laser beam 10 includes a pulse laser beam 8 having an oscillation wavelength of 1064 nm,
The laser beam has characteristics of two types of laser beams, that is, a semiconductor laser beam 9 having an oscillation wavelength of 808 nm. The superposed laser beam 10 is condensed by the condensing lens 5 and irradiated on the aluminum alloys 6 and 7 as the materials to be welded, and lap welding is performed. Since the aluminum alloys 6 and 7 to be welded are mounted on the single-axis stage 12 through the holder 11,
By moving 2 in one direction, seam welding can be performed in a straight line. FIG. 3 shows a final state in which the aluminum alloys 6 and 7 to be welded are overlap-welded. In FIG. 3, reference numeral 13 denotes an aluminum alloy weld.

Next, FIG. 4 shows the pulse waveform of each laser beam (pulse laser beam 8 and semiconductor laser beam 9) when the aluminum alloys 6 and 7 are overlapped and welded in this embodiment. 4A shows a pulse waveform of the pulse laser beam 8, FIG. 4B shows a pulse waveform of the semiconductor laser beam 9, and FIG.
5 shows a pulse waveform of the superposed laser beam 10 in which the laser beam 9 and the semiconductor laser beam 9 overlap.

The pulse laser 1 has an average output of about 20 W, and its pulse laser beam 8 has a pulse width of 200 n.
s, repetition frequency 1 kHz, pulse energy 20 mJ /
P, peak power 100 kW. On the other hand, the semiconductor laser 2 has an average output of about 500 W and is a continuous wave laser. That is, since the peak power of the semiconductor laser beam 8 is 500 W, the peak power of the pulse laser beam 8 is about 200 times that of the semiconductor laser beam 9 when compared with the peak power. FIG. 4 (c)
, T0, t1, t2, t3, and t4 are elapsed times of the laser beam, t0 is before laser irradiation, and t1 is 1
When the pulse laser beam of the shot is irradiated, t2
Is the time between the first shot pulse laser beam and the second shot pulse laser beam, t3 is the time when the second shot pulse laser beam is irradiated, and t4 is the first shot pulse laser beam and the second shot pulse laser beam. Between the laser beam. As a matter of course, the semiconductor laser beam 9 is continuously irradiated during the period from t1 to t4.

In this embodiment, the oscillation repetition frequency of the pulse laser 1 is 1 kHz. That is, the pulse laser beam 8 oscillates 1000 times per second, and the pulse interval is 1 ms. That is, assuming that the time intervals from time t0 to time t4 are equal, the respective values are t0 = 0m
s, t1 = 0.5 ms, t2 = 1 ms, t3 = 1.5 m
s, t4 = 2 ms.

Next, as shown in FIG. 4, the aluminum alloys 6 and 7 are irradiated with a polymerized laser beam 10 obtained by superimposing a pulse laser beam 8 and a semiconductor laser beam 9 on the aluminum alloys 6 and 7. FIG. 5 shows a process of lap welding.

FIG. 5A shows a state before irradiation of the superposed laser beam 10, that is, a state at t0 in FIG. 4C. FIG. 5B shows a state after the time t1. At time t1, the aluminum alloy 6 is irradiated with a polymerized laser beam 10 obtained by polymerizing the pulse laser beam 8 and the semiconductor laser beam 9. At that time, the peak power of the pulse laser 1 is as high as 100 kW, and
Since the aluminum alloy 6, which is the material to be welded, is irradiated in a short time, only the surface of the aluminum alloy 6 is melted, and a thin surface molten layer 14 is formed. In general metal materials, including aluminum, when the surface melts,
Its absorption properties are known to be very good.

Further, after the time t2 shown in FIG. 5C, the aluminum alloy 6 is irradiated only with the semiconductor laser beam 9. Semiconductor laser 2 at that time
Has a low peak power of 500 W. However, at time t1, a thin surface molten layer 14 is formed in the aluminum alloy 6 by the pulse laser beam 8 having a peak power of 100 kW, and therefore, in the molten state, the absorption rate of the laser beam is improved. . And a wavelength of 600 to 100 having basically good absorption characteristics with respect to aluminum.
0 nm semiconductor laser 2 (in this embodiment, 808n
If m) is used, even at a low power of 500 W, the inside of the aluminum alloys 6 and 7 which are the materials to be welded can be melted and the through-welded portion 15 can be formed.

Next, after the time t3, as shown in FIG. 5 (d), as in the case of the time t1, the overlapped laser beam 1 in which the pulse laser beam 8 and the semiconductor laser beam 9 are superimposed.
0 is irradiated, and only the surface of the aluminum alloy 6 is melted by the pulse laser beam 8 having a peak power of 100 kW, and a thin surface molten layer 16 is formed.

After time t4, as shown in FIG. 5 (e), as in time t2, a 1 kW semiconductor laser beam 9 is used to form a penetration welding portion 15 that melts into the aluminum alloys 6 and 7. Is done.

In FIGS. 5 (a) to 5 (e), the aluminum alloys 6 and 7 are attached to the holder 1 as shown in FIG.
1 and mounted on the one-axis stage 12.
However, in FIGS. 5A to 5E, the holder 11, and
The one-axis stage 12 is not shown. Single axis stage 12
Is a speed of 100 mm / s in the direction of arrow 17 on FIG.
ec, and the pulse pitch of the pulse laser beam 8 is 0.1 mm. At this time, good overlap seam welding of the aluminum alloy 6 can be performed. That is, the welding speed is 100 mm / sec, which is 3 mm of the conventional method.
Double welding speed is obtained.

The method for welding an aluminum alloy according to the present invention comprises:
The present invention can be applied not only to the lap welding described in the present embodiment but also to various laser welding methods.

FIG. 6 shows an example of butt welding. When the end faces of the aluminum alloys 6a and 7a are abutted and the boundary surface is irradiated with the superposed laser beam 10 (FIG. 6).
(A)), an aluminum alloy weld 13a is formed, and the aluminum alloys 6a and 7a are welded (FIG. 6).
(B)).

FIG. 7 shows an example of fillet welding. When the aluminum alloys 6b and 7b are fixed perpendicularly to each other and the fillet portion is irradiated with the superposed laser beam 10 (FIG. 7).
(A)), an aluminum alloy weld 13b is formed, and the aluminum alloys 6b and 7b are welded (FIG. 7).
(B)).

FIG. 8 shows an example of butt welding using the aluminum wire 18 as an auxiliary agent. Each of the aluminum alloys 6c and 7c has a C-chamfer at a corner thereof. This is for positioning the aluminum wire 18 as an auxiliary material during laser welding. FIG.
As shown in (a), when the overlapping laser beam 10 irradiates the aluminum wire 18 on the aluminum alloys 6c and 7c, the aluminum wire 18 and the aluminum alloy 6c and
7c is melted, an aluminum alloy weld 13a is formed, and the aluminum alloys 6a and 6b are welded (FIG. 8B).

In the semiconductor laser 2, the semiconductor laser 2 having an oscillation wavelength of nominally 808 nm, 915 nm, or 940 nm provides the highest output. Therefore, it is preferable to use the semiconductor laser 2 in that wavelength band.

As the pulse laser 1, a pulse laser in which the applied current waveform is a pulse waveform (pulse width: 0.1
ms to 20 ms), and the pulse laser (pulse width: 200 ns or less) by Qsw described in this embodiment is practically used.
No. Since a pulse laser having a pulse waveform has a pulse width on the order of ms, high peak power cannot be obtained so much. On the other hand, when the pulse width is 200 ns or less as in the case of a pulse laser based on Qsw, a high peak power that cannot be obtained by a pulse laser based on a pulse waveform is obtained, so that the aluminum alloy is easily melted.

Thus, according to the method of the present invention, an aluminum alloy can be welded at a speed about three times faster than that obtained by the conventional method.

FIG. 9 shows a laser processing apparatus according to a second embodiment of the present invention. The size of the workpiece 23 is 60 × 25 mm, the thickness is 100 μm, and the purity is 99.9%.
It is tough pitch copper. In this embodiment, processing is performed using the fundamental wave YAG laser 2 and the harmonic wave YAG laser 1. The laser processing conditions were as follows: the fundamental wave YAG laser 2 had an energy of 10.4 J, a pulse width of 10 ms, and a spot diameter of 200.
μm, and the harmonic YAG laser has a wavelength of 5 at the second harmonic.
The irradiation is 5 at 32 nm and 1 kHz laser repetition, the pulse width is 100 ns, and the power is 0.2 W. Under such laser processing conditions, using a dichroic mirror 21 that transmits a wavelength of 532 nm and reflects a wavelength of 1064 nm, the fundamental laser light 24 and the harmonic laser light 25 are placed on the same processing optical axis,
Laser irradiation was performed with a condenser lens 22 having little chromatic aberration at 532 nm and 1064 nm so as to converge on the surface of the workpiece 23. Regarding the irradiation time of the fundamental wave laser beam 24 and the second harmonic laser beam 25, as shown in FIG. 10, the start of irradiation of the fundamental wave laser beam 24 and the harmonic wave laser beam 25 is synchronized, and deep penetration is performed by laser superposition. After the irradiation, the irradiation of the harmonic laser light 25 is completed during the irradiation of the fundamental laser light 24, the desired melting depth of about 120 μm is achieved, and the nugget diameter can be suppressed to about 200 μm. In addition, when the number of irradiations is 1, irradiation depth can be about 60 μm, and when 10 irradiations are performed, the melting depth can be about 200 μm. The melting depth can be controlled by the number of irradiations. Can be.

FIG. 11 shows a laser processing apparatus according to a third embodiment of the present invention. The size of the workpiece 23 is 60 × 25 mm, 100 μm thick, made of pure aluminum and aluminum alloy hydrosodium. is there. Here, irradiation with an AOQ switch fundamental wave YAG laser 26 was performed instead of the harmonic laser, and multipoint simultaneous processing was performed for the purpose of suppressing the junction gap. An AOQ switch fundamental wave YAG laser 26 having a characteristic of linearly polarized light is used.
Laser processing conditions: 5 repetitions of 1 kHz laser repetition, 100 ns pulse width, 0.8 W were used. Fundamental wave YAG
The laser 20 is an AOQ switch fundamental wave YAG laser 26
Has a polarization characteristic perpendicular to the linearly polarized light, and has processing conditions of an energy of 3 J, a pulse width of 10 ms, and a spot diameter of 200.
Used at μm. The fundamental wave short pulse laser beam 30 and the fundamental wave laser beam 24 passing through the half mirror 27 are aligned on the same optical axis of the processing laser by the polarizing plate 28, transmitted by the reflecting mirror 29, and covered by the condensing lens 22. Irradiation is performed on two processing points on the workpiece 23 at 50 mm intervals. In the case of processing only one point, FIG.
As illustrated in FIG.
Occurs at a position 50 mm away from the processing point, sometimes reaching a level of several tens of microns, in which case spot welding cannot be realized even by laser irradiation. Therefore, as shown in FIG. 12B, the problem of poor welding due to the gap 31 was solved by simultaneously processing a plurality of distant portions. As a result, two points of nugget diameter 200 μm
It is possible to perform spot welding with a melt depth of about 120 μm.

FIG. 13 shows a laser processing apparatus according to a fourth embodiment of the present invention, in which a Q-switch carbon dioxide laser 31 is used in place of the harmonic laser, and the fundamental wave YAG
The processing axis 32 of the laser 20 is irradiated at an angle of 45 degrees with respect to the vertical direction of the workpiece 23, and the carbon dioxide laser 31 is irradiated in the vertical direction of the workpiece 23 so that the processing point overlaps the fundamental wave YAG laser 20. , And micro spot laser welding was performed. The laser processing conditions at this time were: energy 6 J, pulse width 10 ms, spot diameter 200 × 280
The AOQ switched carbon dioxide laser has a wavelength of 9.24 μm, 5 irradiations at 1 kHz laser repetition, and a pulse width of 150 ns and 3.6 W. Under such laser processing conditions, spot welding with a nugget diameter of about 200 μm and a melting depth of about 120 μm was performed, and the processing was repeated at 30 Hz.

As a result, good laser processing of difficult-to-process materials such as aluminum has become possible.

[0044]

As described above, according to the present invention, a first laser having a peak power for oscillating a pulse and melting a surface of a workpiece is irradiated to the workpiece, and the first laser is irradiated with the first laser. A second laser having a smaller peak power and a longer irradiation time is irradiated to the same place as the first laser,
Laser processing for difficult-to-process materials by increasing the efficiency of fundamental wave laser absorption by forming the fusion nuclei such as melting and holes by adjusting the timing of starting the irradiation of the first laser and the second laser. And welding of difficult-to-process materials such as aluminum alloy with good productivity can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing spectral characteristics of aluminum.

FIG. 2 is a schematic view of a laser processing apparatus according to the first embodiment of the present invention.

FIG. 3 is a view showing a result of lap welding of an aluminum alloy;

FIG. 4 is a pulse waveform diagram of a laser beam.

Fig. 5 Lamination welding process diagram of aluminum alloy

FIG. 6 is a butt welding process diagram of an aluminum alloy.

FIG. 7 is a fillet welding process diagram of an aluminum alloy.

FIG. 8 is a lap welding process diagram of an aluminum alloy using an aluminum wire.

FIG. 9 is a schematic diagram of a laser processing apparatus according to a second embodiment of the present invention.

FIG. 10 is a pulse waveform diagram of a laser beam.

FIG. 11 is a schematic view of a laser processing apparatus according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a micro gap generated in micro spot laser welding.

FIG. 13 is a schematic view of a laser processing apparatus according to a fourth embodiment of the present invention.

FIG. 14 is a pulse waveform diagram of a Nd: YAG pulse laser in conventional laser processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulse laser 2 Semiconductor laser 5 Condensing lens 6 Aluminum alloy 7 Aluminum alloy

Continued on the front page (72) Inventor Koji Funami 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 4E068 BA01 CA03 CA08 CD02 DB04

Claims (10)

[Claims] A step of irradiating the workpiece with a first laser having a peak power for oscillating a pulse and melting a surface of the workpiece, and irradiating the workpiece with a peak power smaller than that of the first laser. Irradiating a second laser whose time is long to the same place as the first laser, and irradiating the first laser with the second laser at the same timing. Laser processing method. 2. The laser processing method according to claim 1, wherein the workpiece is irradiated with the first laser a plurality of times. 3. The laser processing method according to claim 1, wherein laser processing is performed on a plurality of portions of the workpiece at the same time. 4. The workpiece is aluminum or an aluminum alloy, and the first laser is a Q-switch fundamental wave YA.
4. The laser processing method according to claim 1, wherein the G laser and the second laser are a fundamental wave YAG laser. 5. The method according to claim 1, wherein the workpiece is aluminum or an aluminum alloy, the first laser is a Q-switched carbon dioxide laser, and the second laser is a fundamental wave YAG laser. 2. The laser processing method according to 1. above. 6. A workpiece is aluminum or an aluminum alloy, the first laser is a short pulse laser, and the second laser is
4. The laser processing method according to claim 1, wherein said laser is a semiconductor laser having a wavelength of 600 to 1000 nm. 7. The method according to claim 1, wherein the workpiece is aluminum or an aluminum alloy, and the first laser is a short pulse laser having a pulse width of 200 ns or less.
7. The laser processing method according to any one of items 3 and 6. 8. A method for manufacturing a part, comprising welding a workpiece by the method according to claim 1. Description: 9. A first laser having a peak power for oscillating a pulse and melting a surface of a workpiece, and a second laser having a lower peak power and a longer irradiation time than the first laser. And means for irradiating the same spot with the first laser and the second laser, and means for matching the timing of starting irradiation of the first laser and the second laser. Laser processing equipment. 10. The laser processing apparatus according to claim 9, further comprising means for controlling the number of times of irradiation of the first laser.