JP2018023986A - Laser welding device and laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding device and a laser welding method capable of keeping the occurrence of porosity low while achieving simplification of device constitution and cost reduction.SOLUTION: A laser welding device comprises a negative pressure environment generation unit 10 having a nozzle 11 for injecting inert gas G in a direction crossing a laser beam L emitted to a faucet joint Wa from a laser head 4 and a diffuser 12 which lies opposite the nozzle 11 across the laser beam L and introduces the inert gas G that has been injected from the nozzle 11 and crossed the laser light L. The gas discharge side of the diffuser 12 of the negative pressure environment generation unit 10 comprises an additional negative pressure unit 20 for reducing a pressure of the inert gas G discharged from the diffuser 12.SELECTED DRAWING: Figure 1

Description

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

  In the laser welding using the laser beam described above, the laser beam is blocked by high-concentration fumes (metal vapor) or spatter (metal droplets) generated at the laser beam irradiation portion of the workpiece, and reaches the workpiece. When the amount of energy is small, the keyhole generated in the laser beam irradiated portion of the work piece is closed with fume left inside and remains as porosity (bubbles).

  This porosity is known to occur frequently in the case of non-penetrating laser welding such as circumferential welding performed on an inlay joint. Conventionally, as a means for preventing the occurrence of porosity, a negative pressure environment is used. There has been devised a laser welding apparatus for performing laser welding below (see, for example, Patent Document 1).

  This laser welding apparatus has a configuration in which a negative pressure environment generation mechanism that generates a negative pressure environment in a laser beam irradiation portion of an object to be welded is disposed below the laser head. A nozzle that injects an inert gas such as nitrogen gas or argon gas in a direction that crosses the laser beam emitted from the laser head, and an inert gas that crosses the laser beam across the nozzle with the laser beam interposed therebetween. It has a diffuser that diffuses.

JP2015-231629A

  In the laser welding apparatus described above, a negative pressure environment generating mechanism that generates a negative pressure environment is disposed in the laser light irradiation portion of the work piece, so that the porosity is lower than when the negative pressure environment generating mechanism is not used. Although it is possible to greatly suppress the occurrence of the above, it cannot be said that it is satisfactory from the viewpoint of welding quality.

  Therefore, in the laser welding apparatus described above, for example, it may be possible to create an excellent negative pressure environment by lowering the pressure of the laser light irradiated portion of the workpiece to be welded by using an accumulator as an inert gas supply source. However, there is a problem that the apparatus configuration becomes complicated and the apparatus cost increases, and it has been a conventional problem to solve these problems.

  The present invention has been made in order to solve the above-described conventional problems. A laser welding apparatus capable of suppressing the generation of porosity while realizing a simplified apparatus configuration and cost reduction, and The object is to provide a laser welding method.

  A first aspect of the present invention is a laser welding apparatus including a laser head that irradiates laser light, a nozzle that injects gas in a direction across the laser light irradiated from the laser head to an object to be welded, and In the laser welding apparatus comprising a negative pressure environment generating section provided with a diffuser that introduces a gas that is jetted from the nozzle and opposed to the laser beam across the laser beam, the negative pressure environment On the gas discharge side of the diffuser of the generating section, an additional negative pressure section for reducing the pressure of the gas discharged from the diffuser is provided.

  In the second aspect of the present invention, the additional negative pressure section is discharged from the diffuser of the negative pressure environment generating section together with the additional nozzle for injecting additional gas and the additional gas injected from the additional nozzle. In addition, an additional diffuser for introducing the gas is provided.

  Furthermore, the third aspect of the present invention includes a control unit that individually adjusts the gas injection amount of the nozzle in the negative pressure environment generation unit and the additional gas injection amount of the additional nozzle in the additional negative pressure unit. It is configured.

  Furthermore, a fourth aspect of the present invention includes a container that covers the laser beam irradiated from the laser head and accommodates the workpiece, and the nozzle and the diffuser of the negative pressure environment generation unit are provided in the container. Is configured to be fixed.

  Furthermore, the fifth aspect of the present invention is configured such that the container is filled with an inert gas.

  Furthermore, in the sixth aspect of the present invention, the additional negative pressure section is a vacuum pump into which the gas discharged from the diffuser of the negative pressure environment generation section is introduced.

  On the other hand, according to the seventh aspect of the present invention, when welding is performed by irradiating a workpiece with a laser beam from a laser head, a nozzle and a diffuser are opposed to each other with the laser beam irradiated from the laser head interposed therebetween. A gas is jetted from the nozzle in a direction crossing the laser beam irradiated from the head, and the gas crossing the laser beam is introduced into the diffuser to create a negative pressure environment in the laser beam irradiated portion of the workpiece. An additional negative pressure portion for reducing the pressure of the gas discharged from the diffuser is disposed on the gas discharge side of the diffuser, and welding is performed while further reducing the pressure of the gas discharged from the diffuser by the additional negative pressure portion. It is set as the structure which performs.

  The laser welding apparatus according to the present invention has a very excellent effect that the generation of porosity can be reduced while realizing simplification of the apparatus configuration and cost reduction.

It is a section explanatory view showing roughly the laser welding apparatus concerning one embodiment of the present invention. It is a partial expanded sectional explanatory drawing in the spigot joint between the shafts joined by the laser welding apparatus of FIG. CT image explanatory drawing (a) in the spigot joint between a pair of shafts joined by operating the additional negative pressure part of the laser welding apparatus of FIG. 1 and the spigot between the pair of shafts joined without operating the additional negative pressure part It is CT image explanatory drawing (b) in a coupling. It is a partial expanded sectional explanatory view which shows the other structural example of the laser welding apparatus of FIG. It is a fragmentary sectional view showing a laser welding apparatus according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a laser welding apparatus according to an embodiment of the present invention. In this embodiment, the laser welding apparatus according to the present invention is used for circumferential welding at an inlay joint between a pair of shafts. Is shown.

  As shown in FIG. 1, the laser welding apparatus 1 includes a laser oscillator 2 and an optical system, which condenses laser light L supplied from the laser oscillator 2 through an optical fiber 3 to collect a pair of shafts Wn. , Ws, the laser head 4 for irradiating the spigot joint Wa and the control unit 5 for controlling the welding speed, the laser output and the spot diameter. In this embodiment, the focal point LA of the laser light L is that of the spigot joint Wa. It is set to be located on the surface.

  Further, the laser welding apparatus 1 includes a negative pressure environment generation unit 10 that generates a negative pressure environment in the vicinity of the laser light irradiation portion of the pair of shafts Wn and Ws, that is, in the vicinity of the focal point LA of the laser light L.

  The negative pressure environment generation unit 10 injects an inert gas G such as nitrogen gas or argon gas at a high speed in a direction crossing the laser light L emitted from the laser head 4, and the nozzle 11 and the laser light L. A diffuser 12 that introduces and diffuses an inert gas G that is jetted from the nozzle 11 and crosses the laser beam L in a confronting manner, and a negative pressure near the focal point LA covering the laser beam L irradiated from the laser head 4. A container 13 having a coated cylinder 13 a capable of maintaining the environment and a transparent cover 14 covering the laser head 4 side of the coated cylinder 13 a of the container 13 are provided. Both the nozzle 11 and the diffuser 12 are coated cylinders of the container 13. It is fixed to 13a.

  In this case, the container 13 has a shaft support cylinder 13b that supports a pair of shafts Wn and Ws that are rotated by driving means (not shown) integrally with the covering cylinder 13a, and the transparent cover 14 and the upper ends of the covering cylinder 13a By arranging the O-ring 15 between the shaft support cylinder 13b and the O-ring 16 between the pair of shafts Wn and Ws, the negative pressure environment in the covering cylinder 13a of the container 13 is maintained. It is trying to be.

  The laser welding apparatus 1 further includes an additional negative pressure unit 20 disposed on the gas discharge side of the diffuser 12 of the negative pressure environment generation unit 10.

  The additional negative pressure unit 20 introduces an additional nozzle 21 that injects the additional gas Ge, and the inert gas G discharged from the diffuser 12 of the negative pressure environment generation unit 10 together with the additional gas Ge injected from the additional nozzle 21. And an additional diffuser 22 that discharges as a combined gas GM.

  That is, in this additional negative pressure unit 20, the pressure of the inert gas G discharged from the diffuser 12 of the negative pressure environment generation unit 10 is further reduced, so that the laser light already in the negative pressure environment is generated by the negative pressure environment generation unit 10. The irradiation part is further decompressed.

  In this embodiment, the diffuser 12, the additional nozzle 21 and the additional diffuser 22 of the negative pressure environment generating unit 10 are all connected by a merging box 23 in which a negative pressure environment is maintained, and the additional gas Ge from the additional nozzle 21 and The operation of causing the inert gas G from the diffuser 12 of the negative pressure environment generating unit 10 to merge and introduce it into the additional diffuser 22 is performed in the merge box 23.

  Further, in this embodiment, the inert gas injection amount of the nozzle 11 in the negative pressure environment generation unit 10 supplied from the inert gas cylinder 17 and the additional gas of the additional nozzle 21 in the additional negative pressure unit 20 supplied from the additional gas cylinder 18. The injection amount is individually adjusted by the control unit 5.

  Here, if the interval between the nozzle 11 and the diffuser 12 in the negative pressure environment generation unit 10 is set narrow, a good negative pressure environment can be formed in the vicinity of the focal point LA of the laser light L, but welding performed between the nozzle 11 and the diffuser 12 is performed. On the other hand, if the distance between the nozzle 11 and the diffuser 12 is set wide, the welding situation can be easily observed, but the pressure reduction effect in the vicinity of the focal point LA of the laser light L is reduced.

Therefore, the interval between the nozzle 11 and the diffuser 12 in the negative pressure environment generator 10 is adjusted according to the laser output and the magnitude of the negative pressure required near the focal point LA of the laser light L.
In order to maintain or improve the weldability, the inert gas G may be supplied into the coated cylinder 13a of the container 13 via the same system as the negative pressure environment generation unit 10 or a different system.

In the laser welding apparatus and laser welding method according to the present invention, the “negative pressure environment” refers to an atmosphere having a pressure of 90 kPa or less, and the injection speed of the inert gas from the nozzle is a pressure of 90 kPa or less between the nozzle and the diffuser. It is the speed that can be made into the atmosphere.
Examples of the laser used in the laser welding apparatus and the laser welding method according to the present invention include a YAG laser, a CO ₂ laser, a fiber laser, and a disk laser, but are not limited thereto.
Further, laser welding by a laser welding apparatus is not limited to circumferential welding.

Next, the point in the case where the laser welding apparatus 1 performs circumferential welding on the spigot joint Wa between the pair of shafts Wn and Ws to join the pair of shafts Wn and Ws together will be described.
First, from the nozzle 11 of the negative pressure environment generator 10 and the diffuser 12 facing each other with the laser beam L irradiated from the laser head 4, the inert gas G is accelerated at a high speed in a direction crossing the laser beam L. And an inert gas G that has crossed the laser beam L is introduced into the diffuser 12.

  At the same time, the additional gas Ge is injected from the additional nozzle 21 of the additional negative pressure unit 20 at a high speed, and the additional gas Ge injected from the additional nozzle 21 is discharged from the diffuser 12 of the negative pressure environment generation unit 10. The gas G is introduced into the additional diffuser 22 and diffused as a combined gas GM.

  Next, welding is started in this state, and the pair of shafts Wn and Ws supported by the shaft support cylinder 13b of the container 13 is illustrated while irradiating the spigot joint Wa between the pair of shafts Wn and Ws. It is rotated by outside driving means.

  Due to the rotation of the pair of shafts Wn and Ws, as shown in FIG. 2, the weld metal We is formed over the entire circumference of the spigot joint Wa in a non-penetrating state. As a result of the melt evaporation of the portion of the spigot joint Wa due to the above, a keyhole is formed in the spigot joint Wa portion, and fumes are ejected from the inside.

  However, by accelerating the inert gas G between the nozzle 11 and the diffuser 12 of the negative pressure environment generation unit 10, the laser light irradiation portion between the pair of shafts Wn and Ws, that is, the focus LA of the laser light L. The vicinity has a negative pressure. In addition, the additional gas Ge from the additional nozzle 21 of the additional negative pressure section 20 is introduced into the additional diffuser 22 together with the inert gas G discharged from the diffuser 12 of the negative pressure environment generating section 10. Since the pressure of the inert gas G is further reduced, the vicinity of the focal point LA of the laser light L already in the negative pressure environment is further reduced, and the fumes ejected from the keyhole are reliably sucked by the diffuser 12. At this time, spatter may be ejected together with fume, which is also sucked into the diffuser 12.

  As described above, in this laser welding apparatus 1, fumes and spatters generated in the keyhole are sucked and removed by the diffuser 12 of the negative pressure environment generation unit 10 without blocking the laser light L, so that the generation of porosity is small. It will be suppressed.

  Further, in this laser welding apparatus 1, since an expensive accumulator is not used in order to create an excellent negative pressure environment by lowering the pressure of the laser light irradiation portion, the apparatus configuration is simplified and the cost is reduced. Therefore, the generation of porosity can be suppressed to a small extent.

  Therefore, the inert gas G and the additional gas Ge are allowed to flow through the negative pressure environment generating unit 10 and the additional negative pressure unit 20 of the laser welding apparatus 1 so that the pressures thereof are 0.8 MPa and 0.05 MPa, respectively. As a result of circumferential welding, a negative pressure environment of 0.02 atm was formed in the vicinity of the focal point LA of the laser beam L.

  For comparison, when an inert gas G was allowed to flow only through the negative pressure environment generating unit 10 of the laser welding apparatus 1 and circumferential welding was performed so that the pressure became 0.5 MPa, the focal point LA of the laser beam L was obtained. A negative pressure environment of 0.16 atm was formed in the vicinity.

  Further, when the inert gas G is allowed to flow only through the spigot joint Wa and the negative pressure environment generating portion 10 when the inert gas G and the additional gas Ge are allowed to flow through the negative pressure environment generating portion 10 and the additional negative pressure portion 20, respectively. When CT scanning was performed on each of the inlay joints Wa, CT images shown in FIGS. 3A and 3B were obtained.

  In the situation where the inert gas G is allowed to flow only to the negative pressure environment generating unit 10 for comparison, the negative pressure environment near the focal point LA of the laser light L is 0.16 atm, and the CT image in FIG. From this, it can be seen that porosity P is not a little generated.

  On the other hand, in a situation where the inert gas G and the additional gas Ge are caused to flow through the negative pressure environment generation unit 10 and the additional negative pressure unit 20, respectively, the negative pressure environment near the focal point LA of the laser light L is 0.02 atm. Yes, it can be seen from the CT image of FIG. 3 (a) that only a small amount of porosity P is generated. Therefore, according to this laser welding apparatus 1, it was demonstrated that the generation of porosity P can be significantly suppressed. .

  The configurations of the laser welding apparatus and the laser welding method according to the present invention are not limited to the above-described embodiments. As another configuration, for example, as shown in FIG. A merge pipe 25 may be employed. In this case, the pressure loss when the additional gas Ge injected from the additional nozzle 21 of the additional negative pressure unit 20 and the inert gas G discharged from the diffuser 12 of the negative pressure environment generation unit 10 merge can be reduced. it can.

  As another configuration, for example, as shown in FIG. 5, a vacuum pump 30 as an additional negative pressure portion may be arranged on the gas discharge side of the diffuser 12.

  Furthermore, as another configuration, it is possible to add an additional negative pressure portion to the downstream side of the additional negative pressure portion 20.

DESCRIPTION OF SYMBOLS 1 Laser welding apparatus 4 Laser head 5 Control part 10 Negative pressure environment generation part 11 Nozzle 12 Diffuser 13 Container 13a Coated cylinder (container)
13b Shaft support tube (container)
20 Additional negative pressure section 21 Additional nozzle 22 Additional diffuser 30 Vacuum pump G Inert gas Ge Additional gas L Laser light LA Focus of laser light Wn, Ws Shaft (workpiece)

Claims (7)

A laser welding apparatus including a laser head for irradiating laser light,
A nozzle that injects a gas in a direction across the laser beam irradiated from the laser head to the workpiece, and a gas that is injected from the nozzle opposite the nozzle and the laser beam across the laser beam In a laser welding apparatus provided with a negative pressure environment generator equipped with a diffuser for introducing
A laser welding apparatus comprising an additional negative pressure section for reducing the pressure of the gas discharged from the diffuser on the gas discharge side of the diffuser of the negative pressure environment generating section.   The additional negative pressure unit includes an additional nozzle that injects additional gas, and an additional diffuser that introduces the gas discharged from the diffuser of the negative pressure environment generation unit together with the additional gas injected from the additional nozzle. The laser welding apparatus according to claim 1.   The laser welding apparatus according to claim 2, further comprising a control unit that individually adjusts the gas injection amount of the nozzle in the negative pressure environment generation unit and the additional gas injection amount of the additional nozzle in the additional negative pressure unit.   4. The device according to claim 1, further comprising a container that covers the laser beam irradiated from the laser head and that accommodates the workpiece, and wherein the nozzle and the diffuser of the negative pressure environment generation unit are fixed to the container. The laser welding apparatus according to any one of the items.   The laser welding apparatus according to claim 4, wherein the container is filled with an inert gas.   The laser welding apparatus according to claim 1, wherein the additional negative pressure part is a vacuum pump into which the gas discharged from the diffuser of the negative pressure environment generation part is introduced. When performing welding by irradiating the workpiece with laser light from the laser head,
The nozzle and the diffuser are opposed to each other with the laser light emitted from the laser head interposed therebetween,
A gas is injected from the nozzle in a direction crossing the laser beam irradiated from the laser head, and the gas crossing the laser beam is introduced into the diffuser to create a negative pressure environment in the laser beam irradiation portion of the workpiece. Give rise to
An additional negative pressure part that lowers the pressure of the gas discharged from the diffuser is disposed on the gas discharge side of the diffuser,
A laser welding method for performing welding while further lowering the pressure of the gas discharged from the diffuser by the additional negative pressure portion.

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