JP2007253216A - Gas feed nozzle for laser welding and laser welding equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in the quality of a weld zone by easily forming a stable oxidation preventive atmosphere around a molten pool generated by the irradiation of laser light. <P>SOLUTION: A gas feed nozzle 3 for laser welding has a nozzle body part 3a tilted to the light axis LS of laser light L emitted to a sheet material W and injecting a shielding gas G from the oblique part thereof, and the tip 3E of the nozzle body 3a is provided on a planar face PA tilted to the standard plane SP orthogonal to the tube axis line NS of the nozzle body 3a and orthogonal to the light axis LS. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser welding gas supply nozzle and a laser welding apparatus for injecting a shielding gas.

  2. Description of the Related Art A laser welding apparatus having a gas supply nozzle that injects a shielding gas toward a molten pool in order to prevent oxidation of the molten pool when a welded body is irradiated with laser light is known. As this type of laser welding apparatus, there is an apparatus having a shield box surrounding a molten pool and a gas supply nozzle extending through the shield box and movable relative to the shield box (see Patent Document 1). . In this laser welding apparatus, the molten pool is surrounded by a shield box to form an antioxidant atmosphere around the molten pool, and the shield gas is injected from the gas supply nozzle toward the molten pool, thereby Suppresses the generation of plasma in the surroundings.

JP-A-7-136791

  In a conventional laser welding apparatus, a stable antioxidant atmosphere cannot be formed around the molten pool unless a shield box is used. If a shield box cannot be installed due to restrictions in laser scanning or restrictions on the shape of the welded object, it is difficult to form a stable antioxidant atmosphere at a constant gas pressure, which is caused by oxidation of the molten pool. As a result, the weld bead was poorly shaped and burned up, leading to poor quality welds.

  An object of the present invention is to provide a laser welding gas supply nozzle and a laser welding apparatus that can easily form a stable oxidation-preventing atmosphere around a molten pool caused by laser light irradiation and can prevent deterioration in quality of a welded portion. And

  The present invention is a laser welding gas supply nozzle that is inclined with respect to the optical axis of a laser beam irradiated to a welded body and has a nozzle main body for injecting a shielding gas from an oblique direction. The tip is inclined with respect to a reference plane orthogonal to the tube axis of the nozzle body and is provided on a plane orthogonal to the optical axis.

  When the shield gas is jetted using this laser welding gas supply nozzle, the shield gas is jetted in the direction along the optical axis, collides with the welded body, and further along the surface of the welded body. An anti-oxidation atmosphere is formed around the molten pool caused by spreading and laser light irradiation. As a result, the molten pool is shielded from the atmosphere, oxidation in the molten pool is prevented, and defective shape and burnt of the weld bead are suppressed. In particular, according to the laser welding gas supply nozzle, a stable antioxidant atmosphere can be formed around the molten pool by making the tip of the nozzle main body perpendicular to the optical axis of the laser beam. An oxidation-preventing atmosphere can be easily formed even without using.

  The laser welding apparatus according to the present invention is a laser head for irradiating an object to be welded with laser light, and is attached to the laser head and tilted with respect to the optical axis of the laser light to inject the shielding gas from an oblique direction. A gas supply nozzle having a nozzle main body, and the tip of the nozzle main body is provided on a plane that is inclined with respect to a reference plane orthogonal to the tube axis of the nozzle main body and orthogonal to the optical axis. It is characterized by.

  According to this laser welding apparatus, laser light is irradiated from the laser head toward the welded body, and shield gas is injected from the tip of the nozzle main body portion of the gas supply nozzle toward the welded body. The shield gas is ejected in the direction along the optical axis, collides with the welded body, spreads along the surface of the welded body, and forms an oxidation preventing atmosphere around the molten pool caused by the laser light irradiation. As a result, the molten pool is shielded from the atmosphere, oxidation in the molten pool is prevented, and defective shape and burnt of the weld bead are suppressed. In particular, according to this laser welding apparatus, a stable antioxidant atmosphere can be formed around the molten pool by making the tip of the nozzle main body of the gas supply nozzle perpendicular to the optical axis of the laser beam. An oxidation-preventing atmosphere can be easily formed even without using.

  According to the present invention, a stable oxidation-preventing atmosphere can be easily formed around the molten pool caused by laser light irradiation, and the quality of the welded portion is prevented from being deteriorated.

  Hereinafter, preferred embodiments of a laser welding gas supply nozzle and a laser welding apparatus according to the present invention will be described in detail with reference to the drawings.

[First embodiment]
(Laser welding equipment)
As shown in FIGS. 1 to 3, the laser welding apparatus 1 is a welding apparatus that uses a YAG (Yttrium Aluminum Garnet) laser as a heat source for welding. The laser welding apparatus 1 is tilted with respect to an optical axis LS of a laser head 2 that irradiates a laser beam L toward a stainless steel plate W as an object to be welded, and a shielding gas (common name) from obliquely above. A gas supply nozzle 3 for injecting G). The laser head 2 and the gas supply nozzle 3 are moved along a straight joining line SS at a place where the two plate materials W are overlapped.

  The laser head 2 includes a laser oscillation unit 2b in a case 2a. The YAG laser is an optically pumped solid laser, and the laser oscillation unit 2b emits a laser beam L having an oscillation wavelength of 1.06 μm. A condensing lens 2c made of optical glass is disposed on the optical axis LS of the laser light L, and the laser light L transmitted through the condensing lens 2c is condensed at an extremely small point.

  In the following description, the direction perpendicular to the optical axis LS of the laser light L and along the moving direction of the laser head 2 is defined as the X-axis direction, and the direction perpendicular to the X-axis and the optical axis LS of the laser light L is defined as Y. The axial direction and the direction along the optical axis LS of the laser beam L will be described as the Z-axis direction.

  The case 2a of the laser head 2 is provided with a bracket 2d protruding rearward with respect to the traveling direction of the laser head 2, and the first linear actuator 4 is attached to the bracket 2d. The first linear actuator 4 has a servo motor and a ball screw formed on the output shaft of the servo motor, and linearly moves in the Y-axis direction with respect to the bracket 2d by the rotation of the ball screw. A second linear actuator 5 is attached to the first linear actuator 4. The second linear actuator 5 also has a servo motor and a ball screw similar to the first linear actuator 4, and linearly moves in the X-axis direction with respect to the first linear actuator 4 by the rotation of the ball screw. A third linear actuator 6 is attached to the second linear actuator 5. The third linear actuator 6 includes a servo motor and a ball screw, a housing 6a that houses the servo motor and the ball screw, and a rod 6b that linearly moves from the housing 6a in the Z-axis direction by the rotation of the ball screw.

  A U-shaped nozzle bracket 6c is provided at the tip of the rod 6b. As shown in FIG. 2, the nozzle bracket 6c is provided with a pair of left and right side walls 6f, 6g so as to sandwich the gas supply nozzle 3, and bearings 6d, 6e are incorporated in the side walls 6f, 6g. A pair of shaft portions 3b and 3c projecting from the nozzle main body portion 3a of the gas supply nozzle 3 are supported by the pair of bearings 6d and 6e. The shaft portions 3b and 3c are provided in the vicinity of the base end 3d of the nozzle main body portion 3a, and extend orthogonally to the plane PL including the optical axis LS of the laser light L. The tube axis NS of the nozzle body 3a is located on the plane PL including the optical axis LS, and the nozzle body 3a is tilted about the rotation axis C on the plane PL including the optical axis LS.

  A tilt servomotor 8 is fixed to one side wall 6f of the nozzle bracket 6c. The shaft of the tilt servomotor 8 is connected to one shaft portion 3c through a reduction gear. By driving the tilt servomotor 8, the shaft portions 3b and 3c rotate, and the gas supply nozzle 3 tilts. A nozzle actuator 9 is configured by the tilt servomotor 8 and the first to third linear actuators 4 to 6 described above.

  An absolute type rotary encoder 11 is attached to the tilt servomotor 8. The rotary encoder 11 detects the rotation angle of the shaft portion 3c by outputting absolute binary code information according to the rotation angle of the shaft portion 3c. By adopting the absolute type rotary encoder 11, the rotation angle of the shaft portion 3c can be acquired immediately even after the power is turned off and the power is turned on again.

  The nozzle body 3a of the gas supply nozzle 3 is made of copper and is a straight tube having the same inner diameter over the entire length, and has a length of about five times the inner diameter in order to form a laminar flow. Further, the nozzle main body 3a is formed with a closed base end 3d and an open front end 3e. As shown in FIGS. 1 and 3, the tip 3e is formed by being cut so as to have an inclination of an angle γ with respect to a reference plane SP orthogonal to the tube axis NS. A pipe joint portion 3f communicating with the gas supply nozzle 3 is provided on the peripheral wall of the gas supply nozzle 3, and a hose 3g for supplying the shield gas G is fixed to the pipe joint portion 3f. The shield gas G contains argon which is an inert gas. The compressed shield gas G is supplied into the gas supply nozzle 3 through the hose 3g, and is injected from the tip 3e of the gas supply nozzle 3. The gas supply nozzle 3 is moved by the nozzle actuator 9, but the tip 3 e of the nozzle body 3 a is held in a plane PA (see FIG. 3) orthogonal to the laser beam L.

  As shown in FIGS. 1 and 3, the movable arm portion 12 a of the manipulator 12 is fixed to the upper end portion of the laser head 2 via a support column portion 2 e. The manipulator 12 moves the laser arm 2 in the X-axis direction by moving the movable arm portion 12a. On the welding table 13 on which the plate material W is placed, the two plate materials W are placed in a state of being overlapped. The plate material W is a flat plate and extends on the welding table 13 in the horizontal direction. The laser head 2 irradiates the laser beam L toward the linear joining planned line SS in the vertical direction and at the place where the two plate materials W overlap. Further, the laser head 2 moves linearly on the welding table 13 by the operation of the manipulator 12. As the laser head 2 moves, the irradiation part of the laser light L is scanned along the planned joining line SS. By irradiation of the laser beam L, a molten pool S is generated in the plate material W, and after the laser beam L has passed, the molten pool S is solidified to form a laser weld LJ.

  As shown in FIG. 3, the laser welding apparatus 1 includes a main control processing unit 18 configured by a CPU 14, a ROM 16, a RAM 17, and the like connected via a bus. The CPU 14 is connected to the manipulator 12, the laser oscillation unit 2b, the servo motors of the first to third linear actuators 4 to 6, the tilt servo motor 8, and the rotary encoder 11 so that signals can be transmitted and received by wire or wirelessly. The CPU 14 controls the operation of the entire laser welding apparatus 1, and in particular, a laser scanning control unit 14 a that controls the irradiation intensity and laser scanning speed of the laser light L, and a nozzle control unit 14 b that controls the movement of the gas supply nozzle 3. Have The laser scanning control unit 14a outputs an irradiation intensity setting signal for setting the irradiation intensity of the laser light L to the laser oscillating unit 2b and an ON / OFF signal regarding the start and stop of the irradiation of the laser light L, and further to the manipulator 12 A speed setting signal for setting the laser scanning speed, a laser scanning start signal, and a laser scanning stop signal are output. Further, the nozzle control unit 14b outputs a control signal for moving the gas supply nozzle 3 to the nozzle actuator 9 based on the rotation angle detected by the rotary encoder 11, and the tip 3e of the nozzle main body 3a of the gas supply nozzle 3 is It is arranged on a plane PA orthogonal to the optical axis L. The CPU 14 is also connected to a control valve (not shown) that opens and closes the flow path of the shield gas G supplied to the gas supply nozzle 3 so that signals can be transmitted and received, and also outputs an open / close signal to the control valve.

  A touch panel 19 as an operation unit is connected to the CPU 14 so that signals can be transmitted and received. On the liquid crystal screen of the touch panel 19, a touch part is displayed for instructing the initial conditions of laser welding and the start of laser welding. The touch panel 19 detects a position touched by the operator's finger on the liquid crystal screen and outputs an initial setting signal based on the position information. The initial setting signal output from the touch panel 19 is input to the CPU 14, and the CPU 14 outputs various signals to the laser head 2, the manipulator 12, and the nozzle actuator 9 in order to execute control according to the initial setting signal. To do.

(Laser welding method)
A laser welding method using the laser welding apparatus 1 will be described. When performing laser welding, as shown in FIG. 1, the irradiated portion of the laser light L irradiated from the laser head 2 is aligned with the planned joining line SS of the plate material W, and the irradiated portion is aligned with the planned joining line SS. Then, laser scanning is performed by moving at a predetermined speed. Simultaneously with the laser scanning, the shield gas G is ejected from the gas supply nozzle 3. The shield gas G is injected along the optical axis L from the tip 3 e of the gas supply nozzle 3 and collides with the surface of the plate material W. The shield gas G then spreads toward the molten pool S after colliding with the surface of the plate material W, and an oxidation-preventing atmosphere SA having a constant gas pressure is formed around the molten pool S. The molten pool S is shielded from the atmosphere by the formation of the antioxidant atmosphere SA. When laser scanning is performed while forming a stable oxidation-preventing atmosphere SA (see FIG. 5A), laser scanning is performed without forming the oxidation-preventing atmosphere SA (see FIG. 5B). ), The shape of the weld bead is more stable, and burn-in is also suppressed. Since the tip 3e of the nozzle body 3a of the gas supply nozzle 3 is orthogonal to the optical axis LS of the laser light L, a stable antioxidant atmosphere SA can be formed around the molten pool S. The oxidation-preventing atmosphere SA can be easily formed without using Patent Document 1).

The present invention is not limited to the above embodiments. For example, a CO ₂ laser may be used as a welding heat source. Further, the nozzle main body of the gas supply nozzle is not limited to a straight pipe having the same inner diameter over the entire length, and may be a pipe having a narrowed tip inner diameter or a constriction in the middle of the flow path. .

1 is a perspective view showing a first embodiment of a laser welding apparatus according to the present invention. It is sectional drawing along the II-II line of FIG. It is sectional drawing along the III-III line of FIG. It is a block diagram of a laser welding apparatus. It is the photograph which shows a laser welding part, (a) is a photograph which shows the laser welding part which performed laser scanning, forming an antioxidant atmosphere, (b) is a laser scanning without forming an antioxidant atmosphere It is a photograph which shows the laser welding part which performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser welding apparatus, 2 ... Laser head, 3 ... Gas supply nozzle (gas supply nozzle for laser welding), 3a ... Nozzle main-body part, 3e ... Tip, W ... Plate material (to-be-welded body), L ... Laser beam, LS ... optical axis, G ... shield gas, NS ... tube axis, SP ... reference plane, PA ... plane.

Claims (2)

A gas supply nozzle for laser welding, which is inclined with respect to the optical axis of the laser beam irradiated to the welded body and has a nozzle body for injecting shield gas from an oblique direction,
A gas supply nozzle for laser welding, wherein a tip of the nozzle body is provided on a plane that is inclined with respect to a reference plane perpendicular to the tube axis of the nozzle body and perpendicular to the optical axis. . A laser head for irradiating a workpiece with laser light;
A gas supply nozzle attached to the laser head and inclined with respect to the optical axis of the laser beam, and having a nozzle body for injecting a shielding gas from an oblique direction,
The laser welding apparatus according to claim 1, wherein a tip of the nozzle main body is provided on a plane that is inclined with respect to a reference plane orthogonal to the tube axis of the nozzle main body and orthogonal to the optical axis.

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