JP2000052073A - Method and device for laser welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a laser welding device which can carry out a secure crater treatment in a short distance and surely reduce thermal influence and thermal distortion at a portion where a welding area is narrow and at a corner part of an acute angle. SOLUTION: A laser 6 oscillated from a YAG laser oscillator 2 is incident on a parabolic mirror 9 via a mirror 8, reflected downward by 90 deg., and condensed to a work 13. A laser 5 oscillated from a CO2 gas laser oscillator 1 is bent at 90 deg. by a mirror 7, introduced on the same shaft as an optical axis of the YAG laser 6 by the mirror 8 installed on the optical axis of the YAG laser 6 and condensed to the work 13 by the parabolic mirror 9. Since penetration depth by the mixed laser of the CO2 gas laser 5 and the YAG laser 6 is not rapidly reduced, a key hole is not rapidly vanished. Therefore, generation of craters accompanied with a rapid power reduction caused in a case of welding by only the CO2 gas laser 5 can be prevented. Additionally, compared with the case where only the CO2 gas laser 5 is used, a terminating treatment without generating the craters can be carried out in a short time and short distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a laser welding method and apparatus.

[0002]

2. Description of the Related Art In laser welding, if laser irradiation is suddenly stopped at the end of a welded portion, the molten portion is cooled and solidified before embedding a keyhole, so that a crater is generated.

In order to prevent the occurrence of craters at the welding end, the focal point of the laser beam is moved in the laser irradiation direction at the welding end, as described in Japanese Patent Application Laid-Open No. 55-114490. Then, there is a method of gradually lowering the processing power density. Also,
As described in JP-A-60-216987, the focus position of the laser beam is moved in the laser irradiation direction at the welding end and the power of the laser beam is reduced to prevent the occurrence of craters. I was

[0004] Further, in the case of laser welding a workpiece having a portion whose area is sharply reduced, or in the case where a sharp corner portion of the workpiece is continuously laser-welded, the narrow portion or the corner portion is reduced. , Because there is no escape by heat transfer,
Good welding cannot be performed due to thermal strain and thermal effects.

For this reason, even in the narrow portion and the corner portion, as described in Japanese Patent Application Laid-Open No. 55-114490, a process of moving the focal position of the laser beam in the laser irradiation direction is performed. Welding was performed by gradually lowering the power density of the laser.

[0006]

However, in the case of the method of moving the focal position described in Japanese Patent Application Laid-Open No. 55-114490, the width of the weld bead becomes large or the moving speed of the focal position decreases. If it is early, craters may occur.

When a carbon dioxide gas laser is used as a welding laser, the reflectance is high, so that the weld bead disappears suddenly due to the influence of the laser, and the welded portion is rapidly cooled, so that reliable crater treatment cannot be performed. And other problems occur.

Also, with the method described in Japanese Patent Application Laid-Open No. 60-216987, it is difficult to set the speed of energy reduction and the amount of defocus, and when a carbon dioxide laser is used as a welding laser, the reflectance is low. Since it is high, reliable crater processing at a high speed at the terminal end cannot be performed due to the influence of the surface condition.

As a result, a certain welding distance is required for the treatment at the terminal end, and there is a problem that a desired penetration depth cannot be secured at the terminal end.

That is, as shown in FIG. 6, the change in the penetration depth (vertical axis in FIG. 6) due to the power of the carbon dioxide laser (horizontal axis in FIG. 6) sharply decreases at a certain power density (region B). . In the case of performing keyhole welding for obtaining deep penetration, welding is performed in a region C shown in FIG. 6 where the penetration depth is deep. At the end of the keyhole welding, a crater is generated due to the blow-up of the vaporized gas in the keyhole and the solidification of the metal before the keyhole is completely closed.

[0011] To avoid this, the power density of the laser is reduced and the depth of the keyhole is reduced, so that the occurrence of craters can be reduced. But,
During the process, as shown in FIG. 6, there is a region B where the penetration depth is sharply reduced. Therefore, if the energy of the laser is sharply reduced, a crater may be generated.

Therefore, in order to avoid this, it is necessary to perform the crater process by slowly reducing the energy of the laser. In such a process, as shown in FIG. Becomes longer, and the portion with a shallower penetration depth becomes longer than when the distance is small.
Therefore, there is a problem that the desired penetration depth cannot be secured at the end portion.

[0013] Further, even when the area of the welded portion is narrow using a carbon dioxide laser or when sharp corners are continuously welded, as described above, the irradiation power can be reduced from the viewpoint of thermal influence and thermal strain. Required.

However, since the carbon dioxide laser has a high reflectance with respect to metal, if the power is reduced, welding under conditions close to the region B cannot be performed, and the power cannot be reduced so much. Further, there is a problem that stable welding cannot be performed due to the influence of the surface state and the stability of the oscillator.

An object of the present invention is to realize a laser welding method and apparatus which can perform a reliable crater treatment even in a short distance and can surely reduce thermal effects and thermal distortion even in a narrow welding area and a sharp corner. That is.

[0016]

The present invention is configured as follows to achieve the above object. (1) In a laser welding method for welding an object to be welded while suppressing the input power of a laser at a specific portion of the object to be welded, the first characteristic of the relationship between the input power and the penetration depth of the object to be welded is as follows. A first laser having a second characteristic different from the first characteristic with respect to the relationship between the input power and the penetration depth of the workpiece, and having a higher absorptivity for the workpiece than the first laser. Is irradiated to the workpiece, and the input power of the first laser and the second laser is suppressed at a specific location of the workpiece, and the penetration amount at the specific location is reduced. Prevent sharp drops.

(2) Preferably, in the above (1),
The first laser is a carbon dioxide laser, and the second laser is a YAG laser.

(3) Preferably, in (2) above, the crater process generated at the welding end portion is performed by reducing the input of the carbon dioxide gas laser and the YAG laser at the welding end portion of the workpiece. .

(4) Preferably, in the above (2), when welding a region where the portion to be machined of the workpiece is narrower than the upstream portion of welding and a sharp corner, the carbon dioxide laser and the YAG laser are used. By reducing the input power of at least one of the lasers or changing to a pulsed oscillation, the heat deformation and the heat affected zone in the narrowed area and the sharp corner are reduced.

(5) In a laser welding apparatus for welding an object to be welded while suppressing the input power of a laser at a specific portion of the object to be welded, the relationship between the input power and the penetration depth of the object to be welded. A first laser oscillator that oscillates a first laser having a first characteristic, and a second characteristic different from the first characteristic with respect to a relationship between an input power and a penetration depth of the workpiece; A second laser oscillator that oscillates a second laser having a higher absorptivity than the first laser with respect to the workpiece, and an optical device that guides the first laser and the second laser on the same workpiece Means, and control means for suppressing the input power of the first laser and the second laser at a specific location of the work to be welded, to prevent a sharp decrease in the penetration amount at the specific location.

(6) Preferably, in the above (5), the first laser is a carbon dioxide gas laser, and the second laser is a YAG laser.

(7) Preferably, in the above (6), the control means reduces the input of the carbon dioxide gas laser and the YAG laser at the welding end portion of the work to be welded, thereby generating the laser beam at the welding end portion. Crater processing.

(8) Preferably, in the above (6), the control means is provided for welding a region where a portion to be processed of the workpiece is narrower than an upstream portion of welding and a sharp corner. By reducing the input power of at least one of the carbon dioxide gas laser and the YAG laser or by changing to a pulsed oscillation, the heat deformation and the heat affected zone in the narrowed area and the sharp corner are reduced. Relationship between input power and penetration depth of workpiece
A first laser having the following characteristics and a second laser having a second characteristic different from the first characteristic in the above relationship and having a higher absorption rate than the first laser, And the input power of the first laser and the second laser is suppressed at a specific portion of the work to be welded, whereby the characteristic that the amount of penetration sharply decreases with respect to the input power can be improved. .

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment, a carbon dioxide gas laser having a characteristic capable of realizing deep penetration into a workpiece and a YAG laser having a characteristic of having a higher absorptivity for metal than this carbon dioxide laser are arranged on the same optical axis. The case of irradiating a work (weld target object) will be described.

FIG. 1 is a schematic configuration diagram of a laser welding apparatus according to one embodiment of the present invention. In FIG. 1, a laser welding apparatus includes a carbon dioxide laser 1 that oscillates a laser.
, A YAG laser oscillator 2 and laser oscillators 1 and 2
And a power supply (power unit) 3 and Y for a carbon dioxide gas laser for supplying power required for each oscillation.
There is a power supply (power unit) 4 for the AG laser.

The laser 6 oscillated from the YAG laser oscillator 2 enters the parabolic mirror 9 via the mirror 8 and
The light is reflected downward and focused on the work 13. The laser 5 oscillated by the carbon dioxide laser 1 is bent by 90 degrees by the bending mirror 7 and guided coaxially with the optical axis of the YAG laser 6 by the mirror 8 installed on the optical axis of the YAG laser 6. The mirror 8 is a substrate on which a reflection film of the carbon dioxide laser 5 and an antireflection film of the YAG laser 6 are applied. The carbon dioxide laser beam 5 guided as described above is converged on the work 13 by the parabolic mirror 9.

The work 13 is placed on an XY table 15,
The XY table 15 is fixed by a work fixing jig 14 and is controlled by a controller 16. The controller 16 controls the operations of the YAG laser oscillator 2, the carbon dioxide laser oscillator 1, and the power units 3 and 4, respectively.

A shield plane substrate 12 made of ZnSn is attached to a laser emission port of the processing head 10 in which the parabolic mirror 9 is housed so that a shielding gas does not enter the laser beam path. Further, an injection nozzle 11 for injecting the shielding gas is mounted on the laser emission light. With the above apparatus, the carbon dioxide laser 5 and the YAG laser 6
And the XY table 15 is moved to weld the work 13.

In the terminal treatment in laser welding of the work 13, the power of the carbon dioxide laser 5 is changed to that shown in FIG.
As shown in (2), the distance from the terminal portion to a portion that is at least a predetermined distance or more is constant, and linearly decreases from the predetermined distance toward the terminal portion.

The power of the YAG laser 6 is lower than the power of the carbon dioxide laser 5, and the power of the YAG laser 6 is linearly changed from the vicinity of the region B where the penetration depth of the carbon dioxide gas laser 5 shown in FIG. Is reduced to This Y
The starting point of the power reduction of the AG laser 6 is the
The position is closer to the terminal end than the power decrease start point.

Thus, the carbon dioxide laser 5 and the YAG
As shown in FIG. 2B, the total power obtained by adding the laser 6 and the power of the carbon dioxide gas laser 5 starts decreasing, and until the YAG laser 6 starts decreasing, as shown in FIG.
It is decreased by the same inclination as the inclination of the carbon dioxide laser 5. Then, as the power of the YAG laser 6 starts to decrease, the inclination becomes steeper than the previous inclination, and the power becomes zero at the terminal end.

Since the YAG laser 6 has a higher absorptivity to metal due to its wavelength than the carbon dioxide laser 5, a sharp decrease in the penetration depth due to a decrease in power is caused by the carbon dioxide laser 5.
Occurs in the region of lower input power than

Further, a keyhole is formed by the power of the YAG laser 6 even at a low power. Thus, the penetration depth by the laser of the carbon dioxide gas laser 5 + the YAG laser 6 is not sharply reduced, but a line as shown in FIG. 3 is drawn, and the rapid disappearance of the keyhole does not occur.

For this reason, it is possible to prevent the occurrence of a crater due to a sudden decrease in power that occurs when welding is performed using only the carbon dioxide gas laser 5, and the crater can be formed in a shorter time and a shorter distance than when only the carbon dioxide laser 5 is used. Terminal processing that does not occur can be performed.

That is, the carbon dioxide gas laser has a characteristic (first characteristic) that it has a large power and can penetrate deep into the welded material, but has a region where the penetration depth decreases sharply (first characteristic). Compared to carbon dioxide lasers, lasers have lower power and do not allow deeper penetration.However, the region where the penetration depth decreases sharply occurs in the region of lower input power than carbon dioxide lasers. Prepare.

Therefore, by combining the carbon dioxide gas laser and the YAG laser, it is possible to improve the characteristic in which the amount of penetration sharply decreases with respect to the input power.

Next, in the case where the area of the welded portion is narrow or the case where sharp corners are continuously welded, FIGS.
This will be described with reference to FIG. In the case of the work 17 having a narrow welding area as shown in FIG. 4, there is no escape area due to heat transmission near the narrow portion, and thus thermal strain and thermal influence become problems. FIG.
Workpiece 18 having a sharp weld 19 as shown in FIG.
The same problem occurs in the case of.

In order to avoid this, conventionally, the laser power is reduced as described above. However, in the case of a carbon dioxide gas laser, when the power is reduced, the work becomes more susceptible to the surface condition of the work.

When welding a narrow portion along the scheduled welding line 20 using the laser welding apparatus according to one embodiment of the present invention, the power of the carbon dioxide gas laser 5 is reduced while the power of the YAG laser 6 is kept constant. , The total input power to the work 17 is reduced,
Stable laser welding can be ensured even with power near the region.

Further, if the same method is used for welding at an acute angle as shown in FIG. 5, it is possible to perform welding with less ripening and thermal distortion.

As described above, according to one embodiment of the present invention, the carbon dioxide gas laser 6 and the YAG laser 5 are synthesized,
Since it was configured to obtain sufficient power for laser welding and to prevent a sharp decrease in the penetration depth due to a decrease in input power, reliable crater processing can be performed even at short distances, and the welding area is narrow and A laser welding method and apparatus capable of reliably reducing thermal influence and thermal distortion even at sharp corners can be realized.

For example, it is possible to make the output of the YAG laser 6 constant and make the output of the carbon dioxide gas laser 5 pulse-shaped, thereby reducing the influence of heat. In other words, welding by pulse oscillation using only the ordinary carbon dioxide gas laser 5 has a problem that good beads cannot be formed.
Thus, by forming a certain degree of molten state, it is possible to form a good bead by pulse oscillation of a carbon dioxide gas laser having little thermal influence.

In the above-described example, the configuration is such that the YAG laser is reduced following the reduction of the carbon dioxide gas laser, but the carbon dioxide laser and the YAG laser may be reduced substantially simultaneously.

In the above-described example, the YAG laser is used as the auxiliary heat source of the carbon dioxide gas laser. However, the auxiliary heat source is not limited to the YAG laser, and another laser may be used. For example, an iodine laser, a glass laser, a semiconductor laser, or the like can be used.

[0045]

According to the present invention, as described above, the crater treatment can be performed reliably even in a short distance, and the thermal influence and the thermal distortion can be reliably achieved even in a narrow welding area and a sharp corner. Thus, it is possible to realize a laser welding method and an apparatus that can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser welding apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a moving distance of a carbon dioxide gas laser and an input power, and a relationship between a moving distance of a total of a carbon dioxide laser and a YAG laser and an input power.

FIG. 3 is a graph showing the relationship between the input power of a laser, which is the sum of a carbon dioxide gas laser and a YAG laser, and the penetration depth;

FIG. 4 is a diagram illustrating an example of a shape when a region of a welded portion is narrow.

FIG. 5 is a diagram showing an example of a welding line in a case where a welding locus draws an acute angle.

FIG. 6 is a graph showing the relationship between input power and penetration depth when a carbon dioxide laser is used.

FIG. 7 is a diagram illustrating a penetration depth when a crater process is performed at a welding end portion using a carbon dioxide gas laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide laser oscillator 2 YAG laser oscillator 3 Power supply for carbon dioxide laser 4 Power supply for YAG laser 5 Carbon dioxide gas laser 6 YAG laser 7 Bending mirror 8 Substrate 9 Parabolic mirror 10 Processing head 11 Nozzle 12 Shielding flat substrate 13 Processing work 14 Work fixing jig Ingredient

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshiaki Shimomura 650, Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Within the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. F-term in Tsuchiura Plant (reference) 4E068 BA01 CA01 CD02 5F072 AA05 AB01 GG01 GG03 HH03 KK05 MM07 SS06 YY06

Claims (8)

[Claims] In a laser welding method for welding a workpiece while suppressing the input power of a laser at a specific portion of the workpiece, a first relationship between the input power and a penetration depth of the workpiece is described. A first laser having a characteristic, a second characteristic different from the first characteristic with respect to a relationship between an input power and a penetration depth of an object to be welded, and a first laser with respect to the object to be welded.
A second laser having a higher absorptance than that of the laser is irradiated on the workpiece, and the input power of the first laser and the second laser is suppressed at a specific location of the workpiece. A laser welding method for preventing a sharp decrease in penetration amount at a location. 2. The laser welding method according to claim 1, wherein
The first laser is a carbon dioxide laser, and the second laser is a YAG laser. 3. The laser welding method according to claim 2,
The carbon dioxide laser and YAG at the welding end of the workpiece
A laser welding method, wherein a crater process generated at the welding end portion is performed by reducing a laser input. 4. The laser welding method according to claim 2,
When welding a region where the portion to be processed of the workpiece is narrower than the upstream portion and a sharp corner, the input power of at least one of the carbon dioxide gas laser and the YAG laser is reduced or pulsed oscillation is performed. A laser welding method characterized by reducing the heat deformation and the heat affected zone in the narrowed area and the sharp corner by changing. 5. A laser welding apparatus for welding an object to be welded by suppressing an input power of a laser at a specific portion of the object to be welded, wherein a relationship between the input power and a penetration depth of the object to be welded is first. A first laser oscillator that oscillates a first laser having a characteristic; and a second characteristic different from the first characteristic with respect to a relationship between input power and a penetration depth of the workpiece. On the other hand, a second laser oscillator that oscillates a second laser having an absorption rate higher than that of the first laser, an optical unit that guides the first laser and the second laser on the same workpiece, And control means for suppressing the input power of the first laser and the second laser at a specific location of the workpiece to prevent a sharp decrease in the penetration amount at the specific location. Laser welding equipment. 6. The laser welding apparatus according to claim 5,
The first laser is a carbon dioxide laser, and the second laser is a YAG laser. 7. The laser welding apparatus according to claim 6, wherein
A laser welding apparatus, wherein the control means performs a crater process generated at the welding end portion by reducing the input of the carbon dioxide gas laser and the YAG laser at the welding end portion of the workpiece. 8. The laser welding apparatus according to claim 6, wherein
The control means reduces the input power of at least one of the carbon dioxide gas laser and the YAG laser when welding a region where the portion to be processed of the workpiece is narrower than the upstream portion and a sharp corner. A laser welding apparatus characterized by reducing the heat deformation and the heat affected zone in the narrowed area and the sharp corner by changing to the pulsed oscillation.