JP2009039749A - Laser beam machining apparatus and laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a laser beam machining apparatus with which stable and fine welding is easily performed. <P>SOLUTION: In the laser beam machining apparatus with which metal plates 2a, 2b are welded by irradiating the metal plates 2a, 2b with a laser beam 1 emitted from a machining head, the machining head is provided with an inside machining nozzle 31 from which the laser beam 1 is emitted to the welding position between the metal plates 2a, 2b and also with which shielding gas 5 for interrupting air from the welding position between the metal plates 2a, 2b is blown against the welding position between the metal plate 2a, 2b in the coaxial direction with the outgoing axis of the laser beam 1 and an outside machining nozzle 32 which is arranged so as to enclosing the peripheral edge part of the inside machining nozzle 31 and from which shielding gas 6 for interrupting air from the welding position between the metal plates 2a, 2b is blown in the coaxial direction with the outgoing axis of the laser beam 1 against the welding position between the metal plates 2a, 2b. The specific gravity of a first shielding gas is made larger than that of a second shielding gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus and a laser processing method for welding a workpiece by laser light.

  In laser processing, laser light output from a laser oscillator is focused on a processing surface of a workpiece by an optical component such as a lens, and the workpiece is processed using high-density energy generated on the processing surface of the workpiece at this time. This is thermal processing that cuts and welds steel. Since the laser beam used when performing this laser processing has high density energy, the time required for melting and solidifying the workpiece is shorter in laser processing than in arc welding or the like. For this reason, laser processing is 5 to 10 times faster than arc welding.

  When plate materials made of, for example, aluminum or an aluminum alloy (hereinafter referred to as aluminum materials) are welded at a high speed by laser processing, welding defects such as bubbles (blow holes) occur in the depth direction of the welded portion (joint surface), and as a result. , The strength of the welded portion is reduced. For this reason, the aluminum material was welded by low-speed welding such as MIG welding (Metal Inert Gas Welding) or TIG welding (Tungsten Innert Gas Welding). Blow holes generated during welding of an aluminum material by a laser are generated by air entrainment, an oxide film on the surface of the aluminum material, and a difference in hydrogen solid solubility between the solid and liquid of the aluminum material.

  As a method of performing laser welding while preventing the occurrence of this blowhole, argon gas or nitrogen gas is introduced into the first nozzle of the inner circle of the machining nozzle, and the outer circle of the opening concentrically arranged with the first nozzle. There is a laser welding method in which helium gas is introduced into the second nozzle (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 6-7984

  However, since the laser beam emission axis and the shield gas emission axis are not coaxial in the above-described conventional technology, the laser beam emission direction and the shield gas emission direction are different, making it difficult to perform curved welding or welding to narrow areas. There was a problem that there was.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a laser processing apparatus and a laser processing method that easily perform stable and good welding.

  In order to solve the above-described problems and achieve the object, the present invention provides a laser processing apparatus that welds the workpieces to each other by irradiating the workpieces with laser light emitted from the processing head. Emits the laser beam to a welding position of the workpiece, and uses a first shield gas for blocking air from the welding position of the workpiece in the direction coaxial with the emission axis of the laser beam. An inner processing nozzle that sprays the welding position of the laser beam, and a second shield gas that is disposed so as to surround a peripheral edge of the inner processing nozzle and blocks air from the welding position of the workpiece, And an outer processing nozzle that sprays the welding position of the workpiece in the coaxial direction, wherein the specific gravity of the first shield gas is larger than the specific gravity of the second shield gas.

  According to this invention, since the specific gravity of the first shield gas sprayed to the welding position of the workpiece in the same direction as the laser beam emission axis is larger than the specific gravity of the second shield gas, stable and good welding is achieved. There is an effect that it can be easily performed.

  Embodiments of a laser processing apparatus and a laser processing method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment FIG. 1 is a diagram showing a configuration of a laser processing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining laser welding by the laser processing apparatus. The laser processing apparatus 100 is an apparatus that irradiates a workpiece (plate materials 2a and 2b shown in FIG. 2) with laser light (laser beam 1 shown in FIG. 2) to perform laser processing (welding, etc.) on the workpiece. , A control device 10, a laser oscillator 11, an inner shield gas supply unit 12X, an outer shield gas supply unit 12Y, and a machining head 3.

  The laser oscillator 11 sends the laser beam 1 oscillated at a predetermined timing to the machining head 3. The processing head 3 irradiates the joining surfaces of the plate members 2a and 2b with the laser beam 1 sent from the laser oscillator 11 and the shield gases sent from the inner shield gas supply unit 12X and the outer shield gas supply unit 12Y. Then, the plate materials 2a and 2b are welded.

  The processing head 3 has a substantially cylindrical shape, and surrounds the cylindrical inner processing nozzle 31 disposed on the peripheral portion (innermost periphery) of the central axis and the peripheral portion (outermost periphery) of the inner processing nozzle 31. A circular columnar outer processing nozzle 32 is provided. In other words, the processing head 3 is divided into a central portion and a peripheral portion, and an inner processing nozzle 31 is disposed in the central portion and an outer processing nozzle 32 is disposed in the peripheral portion. The inner machining nozzle 31 and the outer machining nozzle 32 are arranged in the same direction so that the central axes thereof coincide with the laser beam emission axis. The inner machining nozzle 31 and the outer machining nozzle 32 are coaxial double nozzles. It has become.

  The inner machining nozzle 31 emits the laser beam 1 and a predetermined shielding gas (gas used for blocking the welding position from the air) in the coaxial direction from the side of the inner circle of the opening, and the outer machining nozzle 32 is arranged on the outer circle of the opening. A predetermined shielding gas is emitted from the blowing side.

  The inner shield gas supply unit 12 </ b> X supplies a predetermined flow rate of shield gas to the inner processing nozzle 31, and the outer shield gas supply unit 12 </ b> Y supplies a predetermined flow rate of shield gas to the outer processing nozzle 32.

  The control device 10 controls the laser oscillator 11, the inner shield gas supply unit 12X, the outer shield gas supply unit 12Y, and the processing head 3. In the present embodiment, the control device 10 controls the gas flow rate supplied to the processing head 3 from the inner shield gas supply unit 12X and the outer shield gas supply unit 12Y and sprayed on the plate members 2a and 2b. Further, the control device 10 controls the oscillation timing of the laser beam 1 of the laser oscillator 11 and the position of the machining head 3.

  Next, laser welding by the laser processing apparatus 100 will be described. In the present embodiment, the case where the plate members 2a and 2b are made of aluminum or an aluminum alloy and the laser processing apparatus 100 butt laser welds the plurality of plate members 2a and plate members 2b at one time will be described as an example of laser processing.

  As shown in FIG. 2, two types of shield gas are ejected from the machining head 3 from an inner machining nozzle 31 at the center and an outer machining nozzle 32 at the periphery. The inner machining nozzle 31 sprays the shield gas (first shield gas) 5 supplied from the inner shield gas supply unit 12X to the welding positions of the plate materials 2a and 2b. The outer processing nozzle 32 sprays the shield gas (second shield gas) 6 supplied from the outer shield gas supply unit 12Y onto the plate materials 2a and 2b. The shield gases 5 and 6 irradiated from the inner processing nozzle 31 and the outer processing nozzle 32 are supplied to the weld metal portion 4 of the plate members 2a and 2b and the vicinity thereof. The weld metal portion 4 is a portion in which the plate materials 2a and 2b are melted when the plate materials 2a and 2b are welded. The weld metal portion 4 joins the plate material 2a and the plate material 2b.

  Oxidation of the surface of the weld metal part 4 can be prevented by irradiation of the shield gas 5 to the plate members 2a and 2b. Further, it is possible to suppress the plasma generated when welding the plate materials 2a and 2b and to smooth the surface of the weld metal portion 4. In addition, it is possible to prevent air from being entrained from around the weld metal part 4 by irradiating the shield gas 6 to the plate members 2a and 2b.

  In the present embodiment, the plate materials 2a and 2b are irradiated with shield gas 5 and shield gas 6 having different flow rates and specific gravity. Thus, when laser welding aluminum or aluminum alloy, by supplying shield gas having different flow rate and specific gravity from the inner processing nozzle 31 and the outer processing nozzle 32 arranged concentrically, Since air entrainment can be prevented, the occurrence of welding defects such as blow holes can be reduced.

  Next, the types and supply flow rates of the shielding gases 5 and 6 when the plate materials 2a and 2b are laser-welded will be described. FIG. 3 is a diagram showing various welding conditions when laser welding a plate material. FIG. 3 shows the types and supply flow rates of the shield gases 5 and 6 supplied from the inner processing nozzle 31 and the outer processing nozzle 32 as welding conditions (conditions A to J) when laser welding the plate members 2a and 2b. .

  For example, under condition A, 5 liters of argon per minute is irradiated from the inner processing nozzle 31 and no shielding gas is irradiated from the outer processing nozzle 32. In condition B, 5 liters of argon is irradiated from the inner processing nozzle 31 per minute, and 20 liters of argon is irradiated from the outer processing nozzle 32 per minute. Further, under condition C, 5 liters of argon is irradiated from the inner processing nozzle 31 per minute, and 20 liters of nitrogen is irradiated from the outer processing nozzle 32 per minute.

  In condition D, 10 liters of argon per minute is irradiated from the inner processing nozzle 31, and no shielding gas is irradiated from the outer processing nozzle 32. Further, under condition E, 10 liters of argon per minute is irradiated from the inner processing nozzle 31 and 20 liters of argon is irradiated from the outer processing nozzle 32 per minute. Under the condition F, 20 liters of argon per minute is irradiated from the inner processing nozzle 31 and no shielding gas is irradiated from the outer processing nozzle 32.

  Further, under the condition G, nitrogen is irradiated from the inner processing nozzle 31 at 5 liters per minute, and the outer processing nozzle 32 is not irradiated with the shielding gas. Under the condition H, nitrogen is irradiated from the inner processing nozzle 31 at 5 liters per minute, and argon is irradiated from the outer processing nozzle 32 at 20 liters per minute. In condition I, nitrogen is irradiated from the inner processing nozzle 31 at 5 liters per minute, and nitrogen is irradiated from the outer processing nozzle 32 at 20 liters per minute. Further, under the condition J, nitrogen is irradiated from the inner processing nozzle 31 at 5 liters per minute, and the outer processing nozzle 32 is not irradiated with the shielding gas.

  When welding the plate materials 2a and 2b under the conditions A to J, for example, a heat-treatable aluminum alloy (A5052) is used for the plate materials 2a and 2b. Further, when the plate materials 2a and 2b are welded under the conditions A to J, the laser processing apparatus 100 performs processing at a processing speed of 2 m / min with a laser output of 2.5 kW continuous wave (CW), for example.

  The quality of welding when the plate materials 2a and 2b are welded under conditions A to J will be described. Here, the determination result when the quality determination of welding is performed based on the following two evaluation items will be described.

  The first evaluation item is the degree of unevenness on the surface of the weld metal part 4. The degree of the unevenness is calculated based on the maximum dent amount in the region where the surface is observed. In welding in the case where the plate members 2a and 2b are aluminum or an aluminum alloy, the surface of the plate members 2a and 2b is subjected to surface machining after welding. Therefore, the weld metal portion 4 must be convex. Therefore, it is judged that the weld metal part 4 having a convex shape is good welding.

  Here, the measuring method of the unevenness | corrugation amount of the weld metal part 4 is demonstrated using FIGS. FIG. 4 is a view showing the plate material after laser welding. As shown in the figure, the welded metal portions 4 are present on the boundary surfaces of the plate material 2a and the plate material 2b along the welding direction in the welded plate materials 2a and 2b.

  5 and 6 are x1-x2 cross-sectional views of the plate shown in FIG. As shown in FIG. 5, if there are concave portions on the surfaces of the plate members 2a and 2b, the concave amount h1 of the portion having the largest concave portion is obtained. Further, as shown in FIG. 6, if there are no recesses on the surfaces of the plate members 2a and 2b, the height h2 of the most convex portion is obtained.

  The second evaluation item is the number of blow holes generated in the weld metal part 4 per unit length. In the present embodiment, the number of blow holes generated is counted and evaluated for each supply method of shield gas 5 and 6 (for each processing condition). The number of blow holes generated is measured, for example, by taking an X-ray transmission photograph of the weld metal part 4.

  A description will be given of the maximum surface dent amount and the number of blow holes generated in the weld metal portion 4 when the plate materials 2a and 2b are welded based on the welding conditions shown in FIG. 7 and 8 are diagrams showing an example of measurement results of the maximum dent amount on the surface of the weld metal part and the number of blow holes generated.

  In FIG. 7, the unevenness | corrugation amount (maximum value) of the weld metal part 4 surface is shown for every conditions AJ. As shown in FIG. 7, the surface has a convex shape under the conditions C and H. Therefore, in order to make the surface convex, the supply flow rate of the shield gas 5 from the inner processing nozzle 31 needs to be 5 liters / minute or less. Further, it is necessary to spray a different kind of shield gas 6 from the outer processing nozzle 32 from the shielding gas 5 injected from the inner processing nozzle 31. When the supply flow rate of the shield gas 5 from the inner machining nozzle 31 is large, the aluminum melt is pushed down or scattered as spatter, so that the dent on the surface of the weld metal portion 4 is considered to be large. For this reason, when the supply flow rate of the shielding gas 5 from the inner processing nozzle 31 is reduced, the surface becomes convex.

  In FIG. 8, the relationship between the specific gravity ratio (shield gas 6 / shield gas 5) of the shield gases 5 and 6 and the number of blowholes generated (total number) in the weld metal part 4 is represented by the conditions B, C, E, H, Shown for each I. The number of blowholes generated in FIG. 8 is 100, where the number of blowholes generated in condition F (when argon is injected from the inner processing nozzle 31 only at 20 liters per minute), which is the same condition as the conventional processing method, This is a standardized number of blowholes generated under other conditions. The number of blowholes generated is smaller than in condition F in the cases of conditions C, B, E, and I.

  In addition, the conditions A, D, G, and J for injecting the shield gas 5 only from the inner machining nozzle 31 are the number of blow holes that is substantially equal to the condition F. For this reason, in order to reduce the number of blowholes generated, a double shield gas is used, and argon gas is injected from the inner processing nozzle 31, and the outer processing nozzle 32 has the same or lower specific gravity than the inner processing nozzle 31. Inject nitrogen. Furthermore, the gas flow rate of the shield gas 5 injected from the inner processing nozzle 31 is set to 5 liters per minute or less.

  From the measurement results of FIGS. 7 and 8, when welding the plate materials 2 a and 2 b under any of the conditions A to J, the most appropriate welding condition is the condition C. Therefore, in the present embodiment, the laser processing apparatus 100 performs welding of the plate materials 2a and 2b using the condition C, for example.

  Next, the inner diameters of the inner processing nozzle 31 and the outer processing nozzle 32 will be described. FIG. 9 is a diagram showing a change in the number of blowholes generated when the inner diameter of the outer processing nozzle 32 is changed. FIG. 9 shows the relationship between the inner diameter of the outer processing nozzle 32 and the number of blow holes generated when the plate materials 2a and 2b are welded under the condition C. 9, the number of blowholes generated under other conditions is normalized with the number of blowholes generated under condition F being 100, as in the case of FIG. As shown in FIG. 9, in order to reduce the number of blow holes generated, an outer processing nozzle 32 having an inner diameter larger than that of the inner processing nozzle 31 may be used, and an inner diameter ratio (inner diameter of the outer processing nozzle 32 / inner processing nozzle 32). The larger the inner diameter (31), the greater the effect.

  For this reason, in the present embodiment, the inner diameter of the outer processing nozzle 32 is made larger than the inner diameter of the inner processing nozzle 31 in order to reduce the number of blow holes generated and improve the quality of laser welding. The ratio of the inner diameter of the inner processing nozzle 31 to the inner diameter of the outer processing nozzle 32 may be changed according to the required quality of laser welding. For example, when it is desired to reduce the number of blow holes generated, the inner diameter of the outer processing nozzle 32 is set to 4.5 times the inner diameter of the inner processing nozzle 31.

  In the present embodiment, the case where butt laser welding is performed on the aluminum or aluminum alloy plate materials 2a and 2b has been described. However, the laser processing apparatus 100 may be another material in which blowholes may be generated due to air entrainment. Alternatively, other welding such as lap welding may be performed. In other words, when the plate members 2a and 2b are welded, the shield gas may be supplied by a double nozzle, and the type and supply method of the shield gas may be conditions other than the condition C. For example, helium or carbon dioxide may be used for the shield gases 5 and 6. Further, a mixed gas such as argon, nitrogen, helium, carbon dioxide may be used for the shielding gases 5 and 6. This makes it possible to perform good laser welding by supplying the shielding gas from the inner processing nozzle 31 and the outer processing nozzle 32 without using a special supply nozzle for the shielding gas.

  As described above, according to the embodiment, since the emission axis of the laser beam 1 and the emission axis of the shield gas are coaxial, the emission direction of the laser beam 1 and the emission direction of the shield gas are the same, and curve welding or narrowing is performed. It is possible to easily perform welding to a certain part. Therefore, stable and good welding of the plate materials 2a and 2b can be easily performed.

  Further, since the specific gravity of the shielding gas 6 emitted from the outer machining nozzle 32 is welded to the plate materials 2a and 2b using the shielding gas 5 and 6 which is smaller than the specific gravity of the shielding gas 5 emitted from the inner machining nozzle 31, welding is performed. It is possible to perform welding with few dents on the surface of the metal part 4 and a small number of blow holes.

  Further, by setting the gas flow rate of the shield gas 5 to 5 liters or less per minute, it is possible to efficiently suppress the generation of blow holes with a small amount of the shield gas 5. Moreover, it becomes possible to suppress generation | occurrence | production of a blowhole efficiently by making the shielding gas 5 into argon gas and making the shielding gas 6 into nitrogen gas. Therefore, even when the plate members 2a and 2b are plate members made of aluminum or an aluminum alloy, it is possible to efficiently suppress the generation of blow holes.

  As described above, the laser processing apparatus and the laser processing method according to the present invention are suitable for welding a workpiece by laser light.

It is a figure which shows the structure of the laser processing apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the laser welding by a laser processing apparatus. It is a figure which shows the various welding conditions at the time of laser-welding a board | plate material. It is a figure which shows the board | plate material after laser welding. It is x1-x2 sectional drawing (1) of the board | plate material shown in FIG. It is x1-x2 sectional drawing (2) of the board | plate material shown in FIG. It is a figure which shows the result of having measured the maximum dent amount of the surface of a weld metal part for every welding condition. It is a figure which shows the result of having measured the generation | occurrence | production number of blowholes for every welding condition. It is a figure which shows the change of the blowhole generation number at the time of changing the internal-diameter ratio of an outer side processing nozzle and an inner side processing nozzle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam 2a, 2b Plate material 3 Processing head 4 Welding metal part 5,6 Shield gas 10 Control apparatus 11 Laser oscillator 12Y Outer shield gas supply part 12X Inner shield gas supply part 31 Inner process nozzle 32 Outer process nozzle 100 Laser processing apparatus

Claims (4)

In a laser processing apparatus that welds the workpieces by irradiating the workpieces with laser light emitted from a processing head,
The processing head is
The laser beam is emitted to a welding position of the workpiece, and a first shield gas that blocks air from the welding position of the workpiece is welded to the workpiece in a direction coaxial with the laser beam emission axis. An inner working nozzle that sprays the position,
A welding position of the workpiece that is disposed so as to surround a peripheral portion of the inner machining nozzle and that shields air from the welding position of the workpiece in a direction coaxial with the laser beam emission axis. An outer working nozzle that sprays on
With
The laser processing apparatus, wherein the specific gravity of the first shield gas is greater than the specific gravity of the second shield gas.   2. The laser processing apparatus according to claim 1, wherein a flow rate of the first shield gas sprayed from the inner processing nozzle to a welding position of the workpiece is 5 liters per minute or less.   3. The laser processing apparatus according to claim 1, wherein the first shield gas is an argon gas, and the second shield gas is a nitrogen gas. 4. In the laser processing method for welding the workpieces by irradiating the workpieces with laser light emitted from the processing head,
When the laser beam is emitted to the welding position of the workpiece, the first shield gas that shuts off air from the welding position of the workpiece is disposed in the coaxial direction with the laser beam emission axis. A second shield gas that blows from the machining nozzle to the welding position of the workpiece and blocks air from the welding position of the workpiece from an outer machining nozzle disposed so as to surround the peripheral edge of the inner machining nozzle. Spraying a welding position of the workpiece in a direction coaxial with an emission axis of the laser beam,
The laser processing method according to claim 1, wherein a specific gravity of the first shield gas is larger than a specific gravity of the second shield gas.

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