JPH05245667A - Laser beam welding method and device used for its execution - Google Patents

Abstract

PURPOSE:To provide a welded part formed nearly uniformly all over the body under a proper molten state irrespective of the surface state of a part to be welded by the laser beam when the welded part is formed by irradiating the part to be welded with the laser light beam. CONSTITUTION:A part 14 to be welded is irradiated with the laser light beam 16 from a laser beam generating part 15 and welded by the laser beam 16, photoelectric transfer is carried out regarding reflected laser beam 18 from the part 14 to be welded and the output in the laser beam generating part 15 is controlled in accordance with the comparison output obtained by comparing an output voltage obtained by the photoelectric conversion with a reference voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method for irradiating a portion to be welded with a laser light beam and performing welding by the laser light beam, and an apparatus used for carrying out the method.

[0002]

2. Description of the Related Art In welding a metal material containing iron, aluminum or the like as a main component, a portion of the metal material to be welded is irradiated with a laser light beam having relatively large light energy. Laser welding has been proposed in which welding is performed by causing melting at a portion to be welded by light energy of a laser light beam.

When laser welding is performed, for example, a state in which a laser light beam is continuously obtained from a laser light generating section constituted by a carbon dioxide gas laser device or the like is taken.
The laser light beam is incident on the portion of the metallic material to be welded, and the incident position of the laser light beam on the metallic material is assumed to move at a prescribed speed, and the welded portion extends along the prescribed direction. Is formed. In the welded portion obtained by laser welding, a bead having a relatively large depth of penetration is formed, and further, the width of thermal influence on the surroundings is relatively narrowed, so that the thermal strain generated in the metal material is reduced. Will be done.

In laser welding of such a metal material, the temperature of the portion of the metal material to be welded gradually rises after the irradiation of the laser light beam from the laser light generating portion is started. To be taken.
With such a temperature change, the surface of the portion of the metal material to be welded has a low light reflectance immediately after the irradiation of the laser light beam from the laser light generator is started. It is high under the condition that substantial melting is not started, and exceeds about 90% in the case of an aluminum-based material, and thereafter,
After the temperature rises and the substantial melting starts, the temperature sharply decreases. For example, in the case of an aluminum material, it becomes about 10 to 20%. Therefore, most of the laser light beam incident on the portion of the metallic material to be welded is reflected from the surface of the portion of the metallic material to be welded immediately after the start of the incidence. , The light energy absorbed and effectively acting on the portion of the metal material to be welded is made small, and then the portion of the metal material to be welded gradually rises to start substantial melting. When,
After that, most of the light energy is absorbed in the portion of the metallic material to be welded, and the light energy that effectively acts on the melting of the portion of the metal material to be welded is large.

Therefore, under the condition that the laser light source for emitting the laser light beam is in a substantially constant output state, the metal material to which the laser light beam from the laser light generator is made to enter is welded. The weld formed in the power part is formed in a state where it is not sufficiently melted at the start of welding by the laser light beam and for a while after that, and in a state where it is sufficiently melted in the subsequent period. As shown in FIG. 4, for example, the unfavorable portion Ra formed in the insufficient welding state at the initial stage of welding along the welding direction W as shown in FIG.
And a subsequent good portion Rb formed under an appropriate molten state. That is, the weld portion formed on the metal material is accompanied by the poor portion Ra formed under the insufficient melting state prior to the favorable portion Rb formed under the proper melting state. Will be.

Therefore, in a laser welding apparatus equipped with a laser beam generator for performing laser welding, when performing laser welding on a metal material, a uniform weld is formed on a portion to be welded on the metal material. Therefore, preset welding conditions according to the material of the metal material used for welding,
By controlling the output of the laser light generator that emits the laser light beam according to the welding conditions, for example, at the start of welding by the laser light beam and at a subsequent period, the output of the laser light generator is compared to the subsequent welding period. It has been proposed to adjust it to be large.

[0007]

However, the individual metal materials that are actually subjected to laser welding differ in the degree of surface roughness, the degree of rust generation, the state of adhesion of deposits such as oil, and the like. The light reflection conditions on the surface are different even if the materials are the same. Therefore, in the case of individual metal materials, some welding conditions set in advance depending on the material may not be met, and the welded portion formed in the portion where the welding of such metal material is to be performed, There is a possibility that the material may not be homogeneous, including a portion that has not been properly melted.

In connection with such a situation, for example, as disclosed in JP-A-62-118994, a welding portion formed by laser welding is irradiated with predetermined light. Originally imaged, a device for determining the quality of the welded portion by analyzing the obtained image, or, for example, as disclosed in JP-A 1-241391,
There has been proposed a method of detecting light generated by a weld when laser welding is performed, and determining the quality of the weld based on the detection result.

In view of such a point, the present invention irradiates a portion of a metallic material to be laser-welded with a laser light beam to form a welded portion, and in forming a welded portion, the degree of surface roughness and rust of the metallic material. Regardless of how it is generated or the state of adherence of deposits such as oil, the resulting welded part, including the part that was formed in the initial stage of welding, is formed to be almost homogeneous under a proper molten state. It is an object of the present invention to provide a laser welding method and an apparatus used for carrying out the laser welding method, which can achieve the above-mentioned good results.

[0010]

In order to achieve the above-mentioned object, a laser welding method according to the present invention irradiates a laser light beam from a laser light generator to a portion to be welded, and the laser light is emitted. Welding with a beam and performing photoelectric conversion on the reflected laser light beam from the part to be welded, and comparing the output voltage obtained by photoelectric conversion with the reference voltage, the laser light The output of the generator is controlled to increase or decrease.

Further, the laser welding apparatus according to the present invention generates a laser light beam, irradiates the portion to be welded with the laser light beam to perform welding, and the portion to be welded. Receiving a reflected laser light beam from, a photoelectric conversion unit that performs photoelectric conversion for the reflected laser light beam, a voltage comparison unit that obtains a comparison output by comparing the output voltage obtained from the photoelectric conversion unit with a reference voltage, And a laser output control unit that controls the increase / decrease of the output of the laser light generation unit according to the comparison output from the voltage comparison unit.

[0012]

According to the laser welding method according to the present invention as described above, or the laser welding apparatus according to the present invention which is an apparatus used for carrying out such a laser welding method, the laser beam from the laser beam generator is generated. The output voltage obtained by photoelectric conversion of the reflected laser light beam from the portion where the beam welding is performed is compared with the reference voltage, and the output in the laser light generator is controlled according to the comparison output obtained as a result. .. Therefore, the output of the laser light generator that irradiates the portion to be laser-welded with the laser light beam is the light reflection state of the portion to be welded by the laser light beam, that is, the actual value in the portion to be laser-welded It will be adjusted according to the surface condition. As a result, irrespective of the degree of surface roughness, the degree of rust generation, the adhered state of deposits such as oil, etc. at the portion to be laser welded, the portion to be laser welded should be It is possible to obtain a good weld which is formed substantially homogeneously in a proper molten state including the formed portion.

[0013]

1 shows an example of an apparatus used for carrying out a laser welding method according to the present invention, together with a member to be welded by laser welding.

In FIG. 1, as a member to be laser-welded on a base 11, two plate-shaped metal materials, for example, two thin steel plates 12 are provided, which are partially overlapped with each other. And 13 are arranged, and the superposed portions of the two thin steel plates 12 and 13 are the portions 14 to be laser-welded. And
Above the two thin steel plates 12 and 13, for example, a laser light generator 15 composed of a high-power carbon dioxide laser is arranged.

The laser light generator 15 emits a laser light beam 16 having a predetermined wavelength, and the laser light beam 1
6 is two thin steel plates 12 and 1 arranged on a base 11.
A portion 14 to be laser-welded in 3 is incident with a preset incident angle. As a result, welding is performed by the laser light beam 16 at the incident position of the laser light beam 16 in the portion 14 of the two thin steel plates 12 and 13 arranged on the base 11 to be laser welded, and the welding portion 17 is formed. In this way, when the welding with the laser light beam 16 is performed, the two thin steel plates 12 and 13 arranged on the base 11 are
The incident position of the laser light beam 16 in the portion 14 to be laser-welded is to move in a predetermined direction by moving the base 11 with respect to the laser light generator 15, for example. A welded portion 17 extending along the moving direction of the incident position of the laser light beam 16 is formed in a portion 14 of the two thin steel plates 12 and 13 to be laser-welded.

Further, above the two thin steel plates 12 and 13, there are disposed, for example, three photoelectric conversion units 20, 21 and 22 each composed of, for example, a semiconductor light receiving element. These photoelectric conversion units 20, 21 and 22 are 2
A laser light beam 16 from a laser light generator 15 on the thin steel plates 12 and 13 is incident, and a reflected laser light beam 18 from a portion where welding is performed by the laser light beam 16 is spread over a relatively wide range. receive. Then, the photoelectric conversion unit 20 performs photoelectric conversion on the received reflected laser light beam 18, and sends out a voltage Va according to the energy of the received reflected laser light beam 18, and the photoelectric conversion unit 21 receives the voltage Va. The reflected laser light beam 18 is photoelectrically converted to output a voltage Vb corresponding to the energy of the received reflected laser light beam 18, and the photoelectric conversion unit 22 further photoelectrically converts the received reflected laser light beam 18. The conversion is performed and the voltage Vc according to the energy of the received reflected laser light beam 18 is transmitted.

The voltages Va, Vb, and Vc obtained from the photoelectric conversion units 20, 21 and 22, respectively, are supplied to an adder 24 where they are added up, and the reflected light voltage Vx (= Va) is added from the adder 24.
+ Vb + Vc) is obtained and supplied to the voltage comparison unit 25. The voltage comparison unit 25 includes two level comparators 26 and 2
7, polarity inverting circuit 28 connected to the output terminal of the level comparator 27, output terminal of the level comparator 26 and the polarity inverting circuit 28
Of the reference voltage Vo + α and Vo−α ((Vo + α)> (V
o-α)) is included in the reference voltage generation circuit 30. The reflected light voltage Vx from the adder 24 is supplied to each of the positive terminal of the level comparator 26 and the negative terminal of the level comparator 27, and the negative terminal of the level comparator 26 and the positive terminal of the level comparator 27 are respectively supplied. Are supplied with the reference voltages Vo + α and Vo−α from the reference voltage generating circuit 30, respectively. Then, the output signal Sa obtained from the level comparator 26 and the output signal Sb obtained from the level comparator 27
Is added in the adder 29 to the inverted output signal −Sb whose polarity is inverted by the polarity inversion circuit 28, and the adder 29
The added output signal obtained from the voltage comparison unit 25 is transmitted as the comparison output signal Sc from the voltage comparison unit 25.

The comparison output signal Sc obtained from the voltage comparison section 25 is sent to the output control section 32 which is attached to the laser light generation section 15 and adjusts the output of the laser light generation section 15 after passing through the amplification circuit 31. Supplied as. Thereby,
The output of the laser light generation unit 15 which emits the laser light beam 16 depends on the comparison output signal Sc obtained from the voltage comparison unit 25, and accordingly, the reflected light voltage Vx obtained from the adder 24.
Will be controlled accordingly.

Under these circumstances, according to the laser welding method according to the present invention, two thin steel plates 12 arranged on the base 11 are provided.
When laser welding is performed on the portion 14 to be laser-welded at 13 and 13, for example, at the time t1 shown in FIG. 2, as shown in A (horizontal axis: time t) of FIG. The output PL of the light generating unit 15 is set to the initial value PL1, and the laser welding of the portion 14 to be laser welded by the laser light beam 16 emitted from the laser light generating unit 15 is started. And
At time t1, as shown by B (horizontal axis: time t) in FIG. 2, the reflected light voltage Vx obtained from the adder 24.
, Takes an initial value V1 higher than the reference voltage Vo + α.

During the period from time t1 to time t2 shown in FIG. 2, the portion 14 to be laser welded is to be formed.
Is gradually increased from a relatively low value, and accordingly, the light reflectance in the portion 14 to be laser-welded is relatively high, and the reflected light obtained from the adder 24 is increased. The voltage Vx has a relatively high value. Then, as shown in FIG. 2B, the reflected light voltage Vx obtained from the adder 24 has the maximum value V1 ′ at the time point t1 ′ within the period from the time point t1 to the time point t2.

After the time point t1 'at which the reflected light voltage Vx obtained from the adder 24 takes the maximum value V1', the temperature of the portion 14 to be laser-welded reaches a predetermined value, which is relatively high. A sufficient melting can be obtained at the incident position of the laser light beam 16 in the portion 14 to be laser-welded, and the light reflectance in the portion 14 to be laser-welded is drastically lowered accordingly. Go As a result, as shown in FIG. 2B, the reflected light voltage Vx obtained from the adder 24 suddenly drops from the state where it takes the maximum value V1 ′, and at the time t2,
The reflected light voltage Vx obtained from the adder 24 decreases to the reference voltage Vo + α from the reference voltage generation circuit 30.

In such a period from time t1 to time t2, the reflected light voltage Vx obtained from the adder 24 supplied to the positive terminal of the level comparator 26 is supplied to the negative terminal of the level comparator 26. Is higher than the reference voltage Vo + α, and the reflected light voltage Vx obtained from the adder 24 supplied to the negative terminal of the level comparator 27 is higher than the reference voltage Vo−α supplied to the positive terminal of the level comparator 27. Therefore, as indicated by C (horizontal axis: time t) in FIG. 2, the output signal Sa from the level comparator 26 has a positive level, and as indicated by D (horizontal axis: time t) in FIG. The output signal Sb from the level comparator 27 has a zero level. During the period from the time t1 to the time t2, the output signal Sa having a positive level from the level comparator 26 is supplied to the positive level through the adder 29 as shown by E (horizontal axis: time t) in FIG. Is output as a comparison output signal Sc, and the amplification circuit 3
The signal is supplied as a control signal to the output control unit 32 attached to the laser light generation unit 15 via 1. As a result, as shown in FIG. 2A, the output PL of the laser light generator 15 becomes
It is increased according to the comparison output signal Sc having a positive level, and accordingly, the output signal Sa having a positive level, and reaches the maximum value PL2 at the time point t2.

During the period from time t2 to time t3 shown in FIG. 2, as shown in B of FIG.
The reflected light voltage Vx obtained from the reference voltage generation circuit 30
Is further decreased from the reference voltage Vo + α from the reference voltage Vo + α.
It decreases to o-α. In such a period from time t2 to time t3, the reflected light voltage Vx obtained from the adder 24 supplied to the positive terminal of the level comparator 26 is the reference voltage Vo + α supplied to the negative terminal of the level comparator 26.
Since the reflected light voltage Vx obtained from the adder 24 supplied to the negative terminal of the level comparator 27 is lower than the reference voltage Vo−α supplied to the positive terminal of the level comparator 27, As shown in C of FIG.
The output signal Sa from 6 takes a zero level, and
As indicated by D, the output signal Sb from the level comparator 27 also takes a zero level. As a result, in the period from time t2 to time t3, as shown in E of FIG.
The comparison output signal Sc is set to zero level, and the output PL of the laser light generator 15 is maintained at the maximum value PL2 as shown in A of FIG.

Then, after time t3, time t shown in FIG.
In the period up to 4, as shown in FIG. 2B, the reflected light voltage Vx obtained from the adder 24 further decreases from the reference voltage Vo-α from the reference voltage generating circuit 30 and then gradually increases. At time t4, the reference voltage Vo-α from the reference voltage generation circuit 30 is reached. In the period from time t3 to time t4, the reflected light voltage Vx obtained from the adder 24 supplied to the positive terminal of the level comparator 26 is the reference voltage Vo + α supplied to the negative terminal of the level comparator 26. Lower and level comparator 2
Since the reflected light voltage Vx obtained from the adder 24 supplied to the negative terminal of 7 becomes lower than the reference voltage Vo-α supplied to the positive terminal of the level comparator 27, as shown in C of FIG. The output signal Sa from the level comparator 26 takes a zero level, and the output signal Sb from the level comparator 27 takes a positive level, as shown in D of FIG. In such a period from time t3 to time t4, after the output signal Sb having the positive level from the level comparator 27 is inverted by the polarity inversion circuit 28 to be the inverted output signal −Sb having the negative level. As shown in E of FIG. 2, a comparison output signal Sc having a negative level is output through an adder 29, and is supplied as a control signal to an output control section 32 attached to the laser light generation section 15 via an amplification circuit 31. It Thereby, as shown in A of FIG.
Output PL is reduced in accordance with the comparison output signal Sc having a negative level, and accordingly the output signal Sb having a high level, and takes a value PL3 smaller than the initial value PL1 at the time t4.

Further, in the period after the time t4, the reflected light voltage Vx obtained from the adder 24 is the reference voltage Vo from the reference voltage generating circuit 30, as shown in B of FIG.
Between −α and the reference voltage Vo + α, for example, the reference voltage Vo
The value V2 is set to be slightly lower than the value Vo which is an intermediate value between −α and the reference voltage Vo + α. In the period after the time t4, the reflected light voltage Vx obtained from the adder 24 supplied to the positive terminal of the level comparator 26 is lower than the reference voltage Vo + α supplied to the negative terminal of the level comparator 26, Further, since the reflected light voltage Vx obtained from the adder 24 supplied to the negative terminal of the level comparator 27 is higher than the reference voltage Vo-α supplied to the positive terminal of the level comparator 27, the voltage is indicated by C in FIG. As shown, the output signal Sa from the level comparator 26 takes a zero level, and
, The output signal Sb from the level comparator 27
Also takes a zero level. As a result, in the period after the time t4, the comparison output signal Sc is set to the zero level as shown in E of FIG. 2, and as shown in A of FIG.
The output PL of the laser light generator 15 is maintained in the state of taking the value PL3.

As described above, the portion 1 to be laser-welded on the two thin steel plates 12 and 13 arranged on the base 11 according to the laser welding method according to the present invention.
4 is laser-welded, the temperature of the portion 14 to be laser-welded from the start of the laser-welding to the portion 14 to be laser-welded by the laser light beam 16 emitted from the laser-beam generator 15. Reaches a relatively high predetermined value so that the laser light beam 16 in the portion 14 to be laser-welded is in a state in which sufficient melting is actually obtained at the incident position of the laser light beam. When the output of the generation unit 15 is increased and a sufficient melting is actually obtained at the incident position of the laser light beam 16 in the portion 14 to be laser-welded, the laser is The output of the light generator 15 is reduced.

Therefore, regardless of the degree of roughness of the surface of the two thin steel plates 12 and 13 to be laser-welded, the degree of rusting, the state of deposits of oil and the like, the laser Part to be welded 14
At the start of laser welding with the laser light beam 16, it is assumed that the temperature is gradually increased from a relatively low value and the light reflectance in the portion 14 to be laser welded is relatively high. Even in the period from when the laser light beam 16 is incident on the portion 14 to be laser-welded to the state where sufficient melting is actually obtained, relatively large light is emitted from the portion 14 to be laser-welded. The energy is absorbed and good welding is performed, and in the subsequent period, the power consumption in the laser light generating portion 15 is relatively small, and the portion 14 to be laser welded is sufficient. Good welding is done under the melt.

As a result, the portion 14 of the two thin steel plates 12 and 13 to be laser-welded includes the portion formed along the welding direction W and formed at the initial stage of welding as shown in FIG. As a result, it is possible to obtain a good welded portion 17 that is formed substantially homogeneously under a proper molten state as a whole.

[0029]

As is apparent from the above description, according to the laser welding method of the present invention, or the laser welding apparatus of the present invention which is an apparatus used for carrying out the laser welding method, The output voltage obtained by photoelectric conversion of the reflected laser light beam from the portion where welding is performed by the laser light beam from the light generation part is compared with the reference voltage, and laser light generation is performed according to the comparison output obtained as a result. Since the output of the laser beam is controlled, the output of the laser light generation part that irradiates the laser light beam to the part to be laser welded is appropriate according to the actual light reflection state in the part where the laser light beam is welded. Can be adjusted to. As a result, irrespective of the degree of surface roughness, the degree of rust generation, the adhered state of deposits such as oil, etc. at the portion to be laser welded, the portion to be laser welded should be It is possible to obtain a good weld that is formed substantially homogeneously in a proper molten state including the formed portion.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an apparatus used for carrying out a laser welding method according to the present invention, together with a member to be welded.

FIG. 2 is a time chart used for explaining the operation in the example shown in FIG.

FIG. 3 is a conceptual diagram provided for explaining a welded portion obtained by the example shown in FIG.

FIG. 4 is a conceptual diagram provided for explaining a welded portion obtained by a conventional laser welding method.

[Explanation of symbols]

 12, 13 Thin steel plate 15 Laser light generation part 16 Laser light beam 17 Welded part 18 Reflected laser light beam 20, 21, 22 Photoelectric conversion part 24 Addition part 25 Voltage comparison part 26, 27 Level comparator 28 Polarity inversion circuit 29 Adder 30 reference voltage generation circuit 32 output control unit

Claims (2)

[Claims] 1. A laser light beam from a laser light generator is applied to a portion to be welded to perform welding by the laser light beam, and a laser beam reflected from the portion to be welded is reflected. A laser welding method characterized by performing photoelectric conversion, and increasing / decreasing the output of the laser light generator according to a comparison output obtained by comparing an output voltage obtained by the photoelectric conversion with a reference voltage. 2. A laser light generation part for generating a laser light beam and irradiating the portion to be welded with the laser light beam for welding, and a laser light beam reflected from the portion to be welded. A photoelectric conversion unit that receives and photoelectrically converts the reflected laser light beam, a voltage comparison unit that compares an output voltage obtained from the photoelectric conversion unit with a reference voltage to obtain a comparison output, and a voltage comparison unit according to the comparison output. A laser welding apparatus configured to include a laser output control unit that controls increase / decrease of output in a laser light generation unit.