JPH06114582A - Pulse laser beam irradiating method for plated steel sheet - Google Patents

Abstract

PURPOSE:To provide the pulse laser beam irradiating method of the plated steel sheet having good welding external appearance free from weld defects with a little scattering of spatters, etc., and capable of obtaining weld beads with sufficient welding strength. CONSTITUTION:A flash lamp control part 14 to control a flash lamp 13 so as to generate two rectangular waves in a pulse waveform in each period of a pulse laser beam oscillated by a YAG pulse laser 12 is provided. The flash lamp control part 14 controls the relation of a peak power value P1 and its pulse width t1 of a first rectangular wave with a peak power value P2 and its pulse width t2 of a second rectangular wave in the specified range and the plated steel sheet is irradiated with the pulse laser beam oscillated by the YAG pulse laser 12 under control of this flash lamp control part 14 to perform welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a plated steel sheet with a laser beam using a pulsed laser, and particularly in the case of performing partial penetration welding (semi-penetration) in lap spot welding and lap seam welding of the plated steel sheet. Pulsed laser irradiation method.

[0002]

2. Description of the Related Art A Zn-plated steel sheet is a steel sheet whose front and back surfaces are Zn-plated in order to obtain a rust preventive effect, and is stipulated in JIS G3302 as a typical steel sheet. The thickness of this Zn-plated steel sheet is 1.6 mm or more and 6.0 mm or less when the hot-rolled original sheet is used, and 0.11 mm or more and 3. 1 mm when the cold-rolled original sheet is used.
It is 2 mm or less. This Zn-plated steel sheet is widely used in light industry and heavy industry such as automobiles and home appliances.

Examples of lap welding of Zn-plated steel sheets are as follows. In the example of two-layer lap welding as shown in FIG. 14 (a), two steel plates having Zn plating 3 on both surfaces 2-
1 and 2 are stacked, and in the example shown in FIG. 14B, one steel plate 2a having the Zn plating 3 is bent to stack two.

In three-layer lap welding as shown in FIG. 15 (a), three steel plates 2-1 and 2-2 having Zn plating 3 on both sides are welded.
In the example shown in FIG. 15B, one steel plate 2b having Zn plating 3 on both sides is bent, and the recess of this steel plate 2b has Zn plating 3 on both sides. One steel plate 2-1 is inserted and three plates are stacked.

Multi-layer welding of four or more sheets as shown in FIGS. 16 (a) and 16 (b) is also performed in the same manner as above. The purpose of semi-penetration welding in lap welding is to maintain the appearance quality of the surface steel sheet while mainly securing the bonding strength. That is, as shown in FIG. 15 (b), the appearance quality of the original steel plate surface is ensured without surface finishing after welding. Further, in the case as shown in FIG. 15A, the appearance quality of the original steel plate surface is maintained by the minimum surface finishing. If a processing method that damages the surface of the Zn-plated layer, such as grinding, is used as the surface treatment of the Zn-plated steel sheet, the anticorrosive effect of the Zn plating treatment is significantly impaired.

Generally, as a method of laser welding a Zn-plated steel sheet, for example, a method using a CW (continuous oscillation) type laser and a pallet oscillation type laser (hereinafter referred to as a palace laser) is known. (1) As an example using a CW type laser, for example, a CW type C
Lap welding by O ₂ laser can be improved. In the CW type CO ₂ laser, the keyhole and laser-induced plasma are continuously maintained during welding. Therefore, the Zn metal vapor (partly turned into plasma) generated by laser irradiation is efficiently removed from the keyhole, but the laser output becomes excessive compared to the pulse laser.

For this reason, the melted and solidified portion becomes large, resulting in full penetration (penetration welding). Even if the irradiation conditions are carefully selected and a partial semi-penetration is obtained, the gap between the Zn-plated steel sheets, which is a welding work (hereinafter referred to as the work-to-work gap), varies, and further, the Zn-plated steel sheet There are variations in the coating weight of the plating (for example, in the case of F08, the Zn coating weight;
For example, 60 to 100 g / m ² ) or the like causes full penetration, or distortion occurs due to excessive heat input, so that a sound steel sheet surface appearance cannot be obtained. (2) On the other hand, as an example using a pulse laser, Nd:
Lap welding with a solid-state laser such as a YAG laser is used. For Nd: YAG laser, lap continuous welding and lap spot welding are known.

The output of the pulse laser is defined as follows. The average output P is P = E · f.

The energy E of one pulse is E = P'.t.

Where P (W) is the average output and E
(J) is the energy of one pulse. P '(W) is
It is the peak power of one pulse and the average peak power per pulse width, t (sec .; second) is the pulse width of one pulse, and f (Hz) is the pulse frequency.

Generally, in pulsed laser welding, the welding volume and the penetration depth for a given welding speed are almost determined by the pulse energy. Therefore, the energy of one pulse (determined by the average output and the pulse frequency) required to obtain the desired fusion is reported as shown in FIG. 17, for example. Here, in FIG. 17, in pulse welding, for example, pulse time, frequency, and average output are optimally matched as processing conditions even in the same curve. When the average output is the same, the pulse has deeper penetration than the CW.

The following are pulse waveforms that give pulse energy. With a rectangular wave as shown in FIG. 18, the peak power P is almost unchanged within the pulse width t. In the integrated waveform as shown in FIG. 19, the pulse width t
The peak power P is changing within. FIG. 20 shows a CW superposition type example. In these examples, basically, as described above, the desired penetration depth is determined by the pulse energy of the rectangular wave.

In the case of a metal whose surface is easily blown off by pulsed laser irradiation, a good weld bead can be obtained by selecting the pulse energy density (peak power density).

The pulse energy and the pulse energy density (peak power density) required to obtain the desired penetration depth for the plate thickness and the predetermined welding speed of such a Zn-plated steel sheet can be easily determined by a conventionally known method. can get.

Further, during laser welding, fumes and spatter prevention methods have been investigated because welding fumes and spatter adhere to the lens and damage the optical system. As a method of protecting the optical system from spatter and fume,
There are a method of installing a glass plate for protection between the work lenses, a method of blowing compressed air from a nozzle to blow out spatters, or a method of using both.

[0016]

However, the above method has the following problems. That is, in a general Nd: YAG laser pulse laser, keyhole and laser-induced plasma are intermittently generated by laser irradiation by pulse oscillation. Therefore, the plating metal vapor generated by laser irradiation (a part of it is converted to plasma) is
It must be removed efficiently for each pulse.

However, with a single rectangular wave pulse, the plating metal vapor cannot be removed and is taken into the molten pool and becomes a welding defect (this is called a blow hole).
Either the case or the case where the molten metal is scattered by the steam pressure (bonding failure). In either case, in addition to poor welding appearance such as blowholes and spatter scattering, the welding strength is significantly reduced.

Also, a large amount of spatter scattering or the like causes damage to the optical system and increases the burden of maintenance. Further, in the case where there is a gap between the steel plates, in addition to the above-mentioned phenomenon, the phenomenon that the weld metal scatters between the steel plates due to the escape of the plating metal vapor to the outside through the gap, resulting in poor welding. However, when the work gap is within a certain range, a good weld bead may be obtained because the plated metal vapor efficiently escapes from between the steel plates.

However, maintaining this gap range between works has been extremely difficult industrially. Regarding the protection of the optical system, the conventional method is
Since spatter is scattered with a large momentum (this is called splash), it cannot be completely removed by compressed air, and spatter adheres to the protective glass,
Get damaged.

Further, fumes (fine metal particles) cannot be completely removed and adhere to optical systems such as protective glass and parabolic mirrors. For this reason, there have been problems that the optical components such as the protective glass are expensive and that there is a time loss due to replacement of the optical components such as the protective glass.

It is an object of the present invention to obtain a weld bead having a good weld appearance with no welding defects such as blowholes, little scattering of spatter, etc., and sufficient welding strength in lap welding of plated steel sheets. It is to provide a pulsed laser irradiation method of a plated steel sheet that can be performed.

[0022]

In order to achieve the above object, the present invention is output from a pulse laser device provided with a pulse laser oscillator having a laser medium and an excitation source for externally exciting the laser medium. In a pulsed laser irradiation method of a plated steel sheet for irradiating a plated steel sheet with a pulsed laser, the pulse laser oscillator is controlled to generate two rectangular waves in a pulse waveform in each cycle of the pulse laser oscillated by the pulse laser oscillator. .

That is, the relationship between the peak power value P ₁ of the _first rectangular wave and its pulse width t ₁ and the peak power value P ₂ of the second rectangular wave and its pulse width t ₂ is controlled within a predetermined range. Then, within the predetermined range, the plated steel plate is irradiated with a pulse laser oscillated by the pulse laser oscillator to weld the plated steel plate.

For the solid-state laser, yttrium-aluminum garnet (Nd: YAG) doped with neondium, ruby, glass or the like is used as the laser medium. Further, CO ² or the like is used in the gas laser.

As the excitation source, Nd: YAG laser, ruby laser, dye laser, glass laser, etc., such as flash lamp, semiconductor laser, etc. are used. Here, as the control method, the peak power is controlled by changing the power of the excitation source, and the pulse width is controlled by changing the conduction time by using, for example, a semiconductor switch of the excitation source.

Further, in the present invention, in the pulse laser oscillator, the relationship between the pulse repetition number f, the welding speed V, and the diameter D of the welding nugget is limited to a predetermined range, and within this predetermined range, A pulse laser may be oscillated from the pulse laser oscillator.

[0027]

According to the present invention, the oscillation control section generates two rectangular waves in the pulse waveform in each cycle of the pulse laser in the pulse laser oscillator, and the peak power value P ₁ and the peak power value P _{1 of the first} rectangular wave are generated. Since the relationship between the pulse width t ₁ , the peak power value P ₂ of the second rectangular wave and the pulse width t ₂ is controlled within a predetermined range, when the oscillated pulse laser is applied to the plated steel sheet, the welding bead is The plated metal vapor can be efficiently removed from the to obtain high-strength weld beads with a good weld appearance with very few weld defects.

The predetermined range in the oscillation control section is 0 <t ₁ / (t ₁ + t ₂ ) <1 P ₁ / P ₂ > 1 t ₁ / (t ₁ + t ₂ ) <0.6. ( P ₁ / P ₂ ) −0.2, and by irradiating the pulse laser in this range, the above effect is exhibited.

The predetermined range is more preferably 0.3 <t ₁ / (t ₁ + t ₂ ) <0.5 1.5> P ₁ / P ₂ > 2.0, and within this range. Irradiation with a certain pulsed laser further enhances the effect. In this case, the waveform is CW
(Continuous oscillation) may be superposed.

Further, under the control of the oscillation control unit, the time interval tint between two rectangular waves is set to 10 millisecond (hereinafter,
m sec. (Abbreviated as)) The following effects are achieved.

Under the control of the oscillation controller, the time interval tint between the two rectangular waves is 2 msec. The effect will be even greater by setting the following. Further, the oscillation control unit applies a pulse so that the pulse energy of the pulse laser has such a strength that it penetrates the first plated steel sheet and partially melts the second plated steel sheet into a plurality of superposed plated steel sheets. By controlling the oscillator, it is possible to irradiate a pulsed laser with a semi-penetration intensity.

Further, the effect can be obtained by setting the angle θ formed by the central axis of the pulse laser and the perpendicular to the surface of the plated steel plate in the range of 0 ° to 60 °. Further, when the angle θ formed by the central axis of the pulse laser and the perpendicular to the surface of the plated steel sheet is in the range of 10 ° to 40 °, the effect is further enhanced.

On the other hand, in the pulse laser oscillator,
Relational expression between the pulse repetition number f, the welding speed V, and the diameter D of the welding nugget, 1-V / (f × D) = L, the pulse overlap rate L (hereinafter abbreviated as the lap rate)
Is limited to the range of 0.5 to 0.9, a weld bead with high weld strength can be obtained.

Here, by limiting the lap ratio L in the range of 0.7 to 0.8, the welding strength is high,
It is possible to obtain a stable weld bead.

[0035]

EXAMPLES Specific examples of the present invention will be described below.
FIG. 1 is a schematic configuration diagram of a laser welding machine for realizing a pulsed laser irradiation method for a plated steel sheet according to the present invention.

<Embodiment 1> As shown in FIG. 1, the laser processing machine is as follows. Pulse laser device 11
Is an Nd: YAG rod 12 and a flash lamp 13.
Device main body 11a having a laser device main body 11a
Power source 14 for supplying power to the
And a cooling device 15.

The Nd: YAG rod 12 receives the power from the flash lamp 13 and is multimode, has an average output of 400 W and oscillates at a wavelength of 1.06 μm. The number of pulse repetitions is 8 pps, and one pulse energy is 50J.

The optical fiber 21 is the laser device main body 11
The laser beam emitted from the laser device main body 11a is connected to the laser beam a and is transmitted to the laser emission unit 22. The laser emission unit 22 is attached to the 6-axis articulated robot 17, and the 6-axis articulated robot 17 allows X,
It is movable in three directions of Y and Z, and is set at an arbitrary coordinate position (X ₁ , Y ₁ , Z ₁ ).

The 6-axis articulated robot 17 has its own coordinate position (X ₂ , Y ₂ , Z ₂ ) and the robot controller 1.
Based on the control position information (X ₁ , Y ₁ , Z ₁ ) for setting the laser emission unit 22 output from 6 for a predetermined position, the laser emission unit 22 is moved to the coordinate position (X ₁ ,
Control to move to Y ₁ , Z ₁ ).

Further, the robot control device 16 is
Control position information for moving the laser emission unit 22 in a predetermined position or in a predetermined direction is also given to the 6-axis articulated robot 17.

FIG. 2 is a block diagram of the laser emission unit 22. As shown in FIG. 2, a condenser lens 22a is provided in the main body 22c, and the tip is tapered. The laser light condensed by the condenser lens 22a is configured to be emitted from the laser emission port 22d. The condensing lens 22a has a focal length of 120 mm, a divergence angle (half angle) of 15 mrad, and a focal position of just focus. A gas such as argon gas or nitrogen gas flows into the laser emission unit 22 at a rate of 10 liters / minute.

The 6-axis articulated robot 17 is a control for setting its own coordinate position (X ₂ , Y ₂ , Z ₂ ) and the laser emission unit 22 output from the robot control unit 18 at predetermined positions. Position information (X ₁ , Y ₁ , Z
Based on ₁ ), the laser emission unit 22 is controlled to move to the coordinate position (X ₁ , Y ₁ , Z ₁ ).

Therefore, by controlling the tilt of the laser emitting unit 22 in the X direction by the 6-axis articulated robot 17,
The angle θ of the central axis C of the laser light with respect to the perpendicular line H from the surface of the welded sample 1c is set to 20 °. Further, the welding sample 1 is controlled by the movement control of the laser emitting unit 22 in the X direction by the 6-axis articulated robot 17.
The welding speed of c is 50 cm / min.

The object to be welded 1c is a galvanized steel plate (JIS
G3302 SGCC SDN), F08 (minimum nominal weight both sides 60/60 g / m ² ), length L100 (mm) × width W30 (mm) × thickness T0.8
(Mm), three sheets are stacked, and the gap between the steel plates is 0 mm. The weld bead length is 20 mm.

The laser power supply unit 14 is the flash lamp 1
The peak power is controlled by the voltage control of 3 and the conduction time is controlled by using, for example, a semiconductor switch. Under such control, the laser waveform of the pulse laser oscillated by the pulse YAG laser 12 is 2 as shown in FIG.
A stepped rectangular wave is used. Here, P ₁ is the peak power of the first stage, and t ₁ is its pulse width. P ₂ is the peak power of the second stage, and t ₂ is its pulse width. Further, f is a pulse repetition frequency.

Therefore, the energy E ₁ of the first stage is represented by E ₁ = P ₁ · t ₁ , and the energy E ₂ of the second stage is represented by E ₂ = P ₂ · t ₂ . Further, here, the average peak power P _AU of 1 pulse is defined as E tot with the pulse energy of 1 pulse, and P _AU = Etot / (t ₁ + t ₂ ) = (E ₁ + E ₂ ) / (t ₁
+ T ₂ ).

In Example 1, in order to obtain a weld bead that partially penetrates from the first steel plate 2-1 through the second steel plate 2-2, the average peak power P _AU is set in addition to the constant pulse energy. It was set to be constant. Under this condition, the penetration depth does not change much even if other settings are changed. In Example 1, P _AU = 5 KW was set.

Further, the following quantities are defined. That is, α = P ₁ / P ₂ β = t ₁ / (t ₁ + t ₂ ). A matrix is constructed with these α and β as variables,
The experiment was performed in the range where the variable α was 3 or less. In addition to the bead appearance, the tensile shear load measured by the tensile test is obtained and evaluated.

As a result, the evaluation results shown in FIG. 4 were obtained from the tensile strength at each point. In FIG. 4, 25 is 25
0kgf or more, △ is 150kgf or more 250kg
It is less than f and x is less than 150 kgf. Further, FIG. 5 shows a change in tensile shear load when the variable α is changed when the variable β is fixed to 0.4.

Summarizing the above results, as shown in FIG. 6, in the range of 1 <α <3, 0 <β <1, β <0.6α-0.2 (1) It was found that a weld bead having sufficient weld strength and a good appearance was obtained as compared with the weld bead obtained from the simple one-step rectangular pulse of, and a great improvement was made.

In particular, in the range of 1.5 <α <2, 0.3 <β <0.5 (2), the welding defects are as shown in FIG. 9 (Photo 1). A very few beautiful bead appearance was obtained and the strongest welding strength was obtained.

As described above, in Example 1, the plated metal vapor can be efficiently removed from the weld bead to obtain a weld bead having a high weld strength and a good weld appearance with very few welding defects.

In Example 1 above, the gap between the steel plates was set to 0 m.
However, when welding was performed under the conditions within the range of the inequality (2) with a gap of 75 μm, a welding shear bead having a better tensile shear load of more than 400 kgf and almost no welding defects. Is obtained.

<Embodiment 2> The laser power supply unit 14a (not shown) has a pulse interval tint between the first-stage pulse waveform and the second-stage pulse waveform of 0 in a typical two-stage rectangular wave.
-10 msec. The flash lamp 13 is controlled so as to change up to. When the pulse interval tint is 0, that is, a two-stage continuous rectangular wave is shown in FIG.

The pulse interval tint is 0 to 10 msec.
As a result, as shown in FIG. 8, as the pulse interval tint of the first and second steps of the two-step rectangular wave is increased, the tensile shear load decreases, and the appearance of the welding bead also becomes a single rectangular wave. It turns out that it approaches (Comparative Example 1).

<Embodiment 3> In Embodiment 3, in the typical two-stage rectangular wave in Embodiment 1 described above, the pulse repetition number f, the welding speed V, and the welding nugget diameter D are used to obtain L = 1− The lap rate L (pulse overlap rate) represented by V / (f × D) was defined, and the pulse repetition number f and the welding speed V were changed so that the lap rate had various values. However, the value of the peak power was changed so as to partially weld the second galvanized steel sheet.

Here, the laser processing machine according to the third embodiment is different from the first embodiment in that the Nd: YAG rod 12 is used.
Pulse energy ratio of P ₁ and P ₂ at; α = P ₁ / P ₂
= 1.6 and the pulse width T ₁ of the first-stage rectangular wave
For 4 msec. , The pulse width T ₂ of the second-stage rectangular wave is 6
m sec. And The other conditions are the same as those in the first embodiment.

Under the above conditions, one of the lap rate L, the pulse repetition number f, and the welding speed V is kept at a constant value, and the other values are made variable to carry out an experiment to evaluate the tensile shear load. I went. The result is shown in FIG.

In the figure, when the value of the lapping rate L is in the range of 0.5 to 0.9, it is possible to obtain a good tensile shear load. Further, when the lap ratio L is in the range of 0.7 to 0.8, a better tensile shear load can be obtained. In other words, the lap rate L
It is possible to obtain a good tensile shear load by setting the pulse repetition number f and the welding speed V so that is within the above range.

Next, a comparative example of the first embodiment and others will be described. (Comparative Example 1) First, Comparative Example 1 is welding with a one-stage rectangular wave pulse having the same output and the same peak energy as those of Example 1. In the case of Comparative Example 1, FIG.
As shown in (Photo 2), the welding bead surface rises,
In addition, holes are formed and the appearance of the weld becomes poor. In the hole portion, the surface molten metal is scattered due to the ejection of zinc vapor, and the lack of molten metal occurs. In FIG. 11, a raised portion A and a hole portion B are shown, and blowholes are generated inside the molten metal in the raised portion A.

For this reason, a large amount of spatter due to the scattering of the molten metal adheres to the sample surface, which is one of the poor appearances. Further, in the raised portion, a large blow hole incorporating zinc vapor is generated inside the molten metal between the first steel plate 2-1 and the second steel plate 2-2, and the portion where this occurs In that case, there is almost no fusion site between the steel sheets. Due to the above two phenomena, the welding strength is extremely lowered, resulting in poor welding.

(Comparative Example 2) In Comparative Example 2, a gap of 75 μm was formed between the first steel plate 2-1 and the second steel plate 2-2, and welding was performed with a single rectangular wave. . As a result, similar to Comparative Example 1, as shown in FIG. 12 (Photo 3), the welding appearance becomes defective, for example, the surface rises, blowholes, spatters, etc., and the tensile shear load also shows a remarkably low value, resulting in welding failure. There is. In FIG. 12, the raised portion A is shown, and blowholes are generated inside the molten metal in the raised portion A. Further, the spatter spouts out of the system and damages the optical system of the laser emitting part.

Comparative Example 3 In Comparative Example 3, the pulse waveform is a two-stage rectangular wave, but the variables α and β are outside the range of the inequality (1). For example, if the variable α is 1.
FIG. 13 (Photo 4) shows the appearance of the weld bead at a point of 2 and β of 0.8. In this range, the appearance of the weld bead is disturbed, spatter is scattered, and the weld strength is reduced due to the incorporation of blowholes in the molten pool, resulting in poor welding.

In FIG. 13, a weld bead turbulence portion C including blow holes is generated, and spatter is jetted out of the system. Further, by setting the angle θ between the central axis of the pulse laser and the perpendicular to the surface of the plated steel sheet to be in the range of 0 ° to 60 °, the durability of the protective glass arranged immediately before the lens 22 (transmission laser output is 10% The weld bead count until it decreased was about 200 to about 800, which was about four times the durability.

If θ becomes too large, there is a problem of interference with the welding work, the work clamp jig, and the like. In that case, the durability of the protective glass can be secured by setting θ to an appropriate range of 10 ° to 40 °.

Although the first and second embodiments and the first to third comparative examples are described above, according to the first and second embodiments, the pulse laser irradiation waveform is a two-stage rectangular wave,
By setting the irradiation condition in a predetermined range, it is possible to efficiently remove the plating metal vapor from the weld bead and obtain a weld bead having a high welding strength and a good weld appearance with very few welding defects. In addition, the optical system is less likely to be damaged, and thus the burden of maintenance can be reduced.

[0067]

According to the present invention, the pulsed laser irradiation waveform is a predetermined two-stage rectangular wave, so that the plating metal vapor can be efficiently removed from the welding bead, resulting in good welding with very few welding defects. It is possible to obtain a weld bead having an appearance and high welding strength. Further, the optical system is less likely to be damaged, and the burden of maintenance can be reduced.

Further, by limiting the pulse overlap rate to a predetermined value, it becomes possible to provide a pulse laser irradiation method which has a high welding strength and can obtain a stable welding bead.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a laser emission unit.

FIG. 3 is a diagram showing a two-stage rectangular wave.

FIG. 4 is a diagram showing a shear load in a matrix test.

FIG. 5 is a diagram showing a relationship between α and a tensile shear load when β is 0.4.

FIG. 6 is a diagram showing a comprehensive good welding range of α and β.

FIG. 7 is a diagram showing a two-stage continuous rectangular wave.

FIG. 8 is a diagram showing a relationship between a pulse interval in the first and second steps and a tensile shear load.

FIG. 9 is a diagram showing the appearance of a weld bead of Example 1.

FIG. 10 is a diagram showing a relationship between a pulse overlap rate and a tensile shear load.

11 is a diagram showing the appearance of a weld bead in Comparative Example 1. FIG.

FIG. 12 is a view showing the appearance of a weld bead of Comparative Example 2.

13 is a diagram showing the appearance of a weld bead in Comparative Example 3. FIG.

FIG. 14 is a diagram showing an example of partial penetration welding in which two sheets are stacked.

FIG. 15 is a diagram showing an example of partial penetration welding in which three sheets are stacked.

FIG. 16 is a diagram showing an example of partial penetration welding in which four or more sheets are stacked.

FIG. 17 is a diagram showing one pulse energy required to obtain a desired penetration depth.

FIG. 18 is a diagram showing a rectangular wave.

FIG. 19 is a diagram showing an integrated waveform.

FIG. 20 is a diagram showing a CW superposition type waveform.

[Explanation of symbols]

 1 ··· Plated steel sheet 2 · · Steel sheet 3 · · Galvanized 11 · · Pulse laser device 11a · · Pulse laser device body 11b · · Laser controller 12 · · YAG laser 13 · · Flash lamp 14 · · Laser power supply unit 15 · ·・ Cooling device 16 ・ Robot control device 17 ・ ・ 6 axis articulated robot 21 ・ ・ Optical fiber 22 ・ ・ Laser emission unit 22a ・ ・ Condenser lens 22c ・ ・ Main body 22d ・ ・ Laser emission port

Claims (11)

[Claims] 1. A method for irradiating a plated steel sheet with a pulse laser, which irradiates a plated steel sheet with a pulse laser output from a pulse laser device having a pulse laser oscillator having a laser medium and an excitation source for exciting the laser medium from the outside. In the above, two rectangular waves are generated in the pulse waveform in each cycle of the pulse laser emitted from the pulse laser oscillator, and the peak power value P ₁ of the _first rectangular wave of the rectangular wave and its pulse width t ₁ , and wherein a second rectangular wave relationship between the peak power value P ₂ and the pulse width t ₂ of the limit in a predetermined range, irradiating a pulsed laser to the plated steel sheet in the range from the pulse laser oscillator Pulsed laser irradiation method for plated steel sheet. 2. The predetermined range is 0 <t ₁ / (t ₁ + t ₂ ) <1 P ₁ / P ₂ > 1 t ₁ / (t ₁ + t ₂ ) <0.6 · (P ₁ / P ₂ ) -0.2 was set, and the pulse laser irradiation method of the plated steel sheet according to claim 1 characterized by things. 3. The predetermined range is set to 0.3 <t ₁ / (t ₁ + t ₂ ) <0.5 1.5 ≧ P ₁ / P ₂ ≧ 2.0. A method for irradiating a plated steel sheet with a pulsed laser. 4. The time interval between the two waveforms is 10 m
sec. (Milli second) or less, The pulse laser irradiation method of the plated steel plate of Claim 1 characterized by the above-mentioned. 5. The time interval between the two waveforms is 2 ms.
ec. The pulsed laser irradiation method for a plated steel sheet according to claim 1, wherein: 6. When welding the output of the pulse laser oscillator up to the Nth sheet of the plated steel sheets with the pulse energy of the pulsed laser, the (N-
1) The pulse laser irradiation method for a plated steel sheet according to claim 1, wherein the strength is controlled so as to penetrate the first plated steel sheet and partially melt the Nth plated steel sheet. 7. The method for irradiating a plated steel sheet with a pulse laser according to claim 1, wherein an angle formed by a central axis of the pulse laser and a perpendicular to the surface of the plated steel sheet is in a range of 0 ° to 60 °. 8. The angle formed by the central axis of the pulse laser and the perpendicular to the surface of the plated steel sheet is 10 ° to 40 °.
2. The method for irradiating a plated steel sheet with a pulsed laser according to claim 1, wherein: 9. The pulse of a plated steel sheet according to claim 1, wherein in the pulse laser oscillator, the relationship among the pulse repetition number f, the welding speed V, and the diameter D of the welding nugget is limited to a predetermined range. Laser irradiation method. 10. The pulse laser irradiation method according to claim 9, wherein the predetermined range is 0.5 ≦ {1-V / (f × D)} ≦ 0.9. 11. The pulse laser irradiation method according to claim 9, wherein the predetermined range is 0.7 ≦ {1-V / (f × D)} ≦ 0.8.