JP6327453B2 - Laser welding method and apparatus - Google Patents

Description

  The present invention relates to a laser welding method and apparatus for suppressing the occurrence of welding defects such as porosity in butt welding of metals using laser light.

  In laser welding, a cylindrical body case having an opening having an outer periphery constituted by a rectangular frame including two long sides facing each other and two short sides facing each other is inserted into the opening of the case. A sealing member such as a lid may be welded over the entire circumference of the sealing member. In such a case, as a conventional laser welding method, there is a welding method in which spot portions having high laser intensity are arranged on the case side and the sealing member side, respectively (see, for example, Patent Document 1). . FIG. 6A is a diagram showing a conventional laser welding method described in Patent Document 1. FIG. FIG. 6B is an enlarged view of the laser spot 104 of FIG. 6A.

  6A and 6B, the laser spot 104 includes three laser spots 104a, 104b, and 104c. Laser spots 104b and 104c having a high power density are applied to the metal case 101 and the lid 102, respectively. As a result, the metal case 101 and the lid 102 can be melted deeply regardless of the size of the gap between the metal case 101 and the lid 102. For this reason, generation | occurrence | production of the welding defect by a clearance gap is suppressed.

  In addition, as a conventional laser welding method, there is a method in which a laser beam is branched using a diffractive optical element (Differential Optical Element. Hereinafter, simply referred to as DOE) to simultaneously process multiple points (for example, (See Patent Document 2). FIG. 7 is a diagram showing a conventional laser welding method described in Patent Document 2. As shown in FIG.

  In FIG. 7, welding is simultaneously performed by irradiating the connection terminals 211 and 212 of the crystal resonator 210 and the crystal resonator terminals 221 and 222 of the substrate with the branched beam 202 </ b> A branched by the DOE 204.

JP 2013-220462 A Japanese Patent No. 3775410

  However, in the conventional configuration, when the surface of the welded portion is contaminated by deposits or surface oxides, the contaminated portion is taken into the weld pool of the welded portion. Therefore, it has the subject that defects, such as a porosity, will generate | occur | produce in a welding part. Here, the term “porosity” is used as a general term for blow holes generated in the weld metal part after solidification by gas generated in the molten metal, pits having holes in the form of worms, and the like.

  FIG. 4 is a schematic diagram of a cross-section of a melted part of a material to be welded 206 in the conventional laser welding method described in Patent Document 1. Reference numeral 207 denotes the moving direction of the spot 241. The surface contamination 208 on the surface of the material 206 to be welded is gasified by the spots 241 and is taken into the molten pool 251 before being sufficiently diffused to become a porosity 209. Conventionally, in order to remove the surface dirt 208, another process such as cleaning has been required in advance.

  The present invention solves the above-mentioned conventional problems, and performs laser cleaning at the same time as welding to prevent the deposits on the surface of the welded portion from being taken into the molten pool, thereby suppressing the occurrence of welding defects. It is an object to provide a welding method and apparatus.

In order to achieve the above object, a laser welding method according to one aspect of the present invention is directed to welding by irradiating a material to be welded while moving a focused laser beam using a lens and a diffractive optical element. In the way to do
As the diffractive optical element, a focused spot on the workpiece to be welded by the laser light is disposed in front of the focused spot in the traveling direction of the focused spot, away from the preceding spot, and is welded. A main spot for melting the material, and when irradiating the surface of the material to be welded with the preceding spot, the gas other than the material to be welded adhered to the surface of the material to be welded is decomposed and gas While using a diffractive optical element that is heated to a temperature that generates or higher and the energy intensity is set so that the melting depth from the surface of the workpiece to be welded is shallower than the allowable porosity diameter,
Irradiating the surface of the material to be welded with the preceding spot to decompose the substance other than the material to be welded attached to the surface of the material to be welded to generate the gas,
After the irradiation of the preceding spot, the generated gas is diffused before being irradiated at the main spot,
Then, the surface of the material to be welded is irradiated at the main spot to melt the material to be welded ,
The preceding spot is linear, the longitudinal direction of the linear preceding spot is a direction intersecting the moving direction of the focused spot, and the longitudinal dimension of the linear preceding spot is and larger than the width of the main spot in the direction parallel to the longitudinal direction, including the area for melting the material to be welded in the main spot, you irradiating a wider area of the preceding spot the linear, It is characterized by that.

In order to achieve the above object, a laser welding apparatus according to another aspect of the present invention welds a material to be welded by irradiating a laser beam condensed by using a lens and a diffractive optical element while moving. In a laser welding apparatus that performs
As the diffractive optical element, a focused spot on the workpiece to be welded by the laser light is disposed in front of the focused spot in the traveling direction of the focused spot, away from the preceding spot, and is welded. A main spot for melting the material, and when irradiating the surface of the material to be welded with the preceding spot, the gas other than the material to be welded adhered to the surface of the material to be welded is decomposed and gas Using a diffractive optical element that is heated to a temperature higher than the temperature at which it is generated and the energy intensity is set so that the melting depth from the surface of the workpiece to be welded is shallower than the allowable porosity diameter ,
The preceding spot is linear, the longitudinal direction of the linear preceding spot is a direction intersecting the moving direction of the focused spot, and the longitudinal dimension of the linear preceding spot is It is characterized by being larger than the width dimension of the main spot in the direction parallel to the longitudinal direction .

  As described above, according to the laser welding method and apparatus of the above aspect of the present invention, the deposit on the surface of the workpiece to be welded in front of the focused spot traveling direction is cleaned before deep penetration and the probability of porosity generation is increased. It becomes possible to greatly lower. In addition, since the surface is melted at the preceding spot before irradiation of the main spot, the change in the absorptance on the surface of the main spot is stabilized, and uniform penetration can be obtained. Therefore, it is possible to suppress the occurrence of welding defects such as porosity without removing contamination due to deposits or surface oxides on the surface of the welded part in a separate process before welding.

The block diagram of the optical system of the laser welding method in 1st Embodiment of this invention The schematic diagram of the beam profile of the laser welding method in 1st Embodiment of this invention. The schematic diagram of the fusion | melting part cross section of the laser welding method in 1st Embodiment of this invention. The schematic diagram of the fusion | melting part cross section of the laser welding method in 1st Embodiment of this invention. Schematic diagram of cross section of melted portion in conventional laser welding method described in Patent Document 1 The schematic diagram of the beam profile of the laser welding method in 2nd Embodiment of this invention The schematic diagram of the beam profile of the laser welding method in the modification of 2nd Embodiment of this invention The schematic diagram of the beam profile of the laser welding method in the modification of 2nd Embodiment of this invention The schematic diagram of the beam profile of the laser welding method in the modification of 2nd Embodiment of this invention Top view in the conventional laser welding method described in Patent Document 1 Enlarged view of the laser spot in FIG. 6A Explanatory drawing of welding to a substrate of a crystal unit having two connection terminals in the conventional laser welding method described in Patent Document 2

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram of an optical system of a laser welding method and apparatus according to a first embodiment of the present invention. In FIG. 1, the laser welding apparatus 30 includes a laser oscillator 31, a DOE 2, and a lens 3.

  In FIG. 1, a laser beam 1 emitted from a laser oscillator 31 forms a focused spot 4 on the upper surface of a workpiece 6 through a DOE 2 and a lens 3. The said condensing spot 4 is moving toward the moving direction 7 of the condensing spot 4, and the welding part 5 is formed on the upper surface of the to-be-welded material 6 in the back.

  FIG. 2 is a schematic diagram of a beam profile at the focused spot 4 (see FIG. 1) of the laser welding method according to the first embodiment of the present invention. As shown in the upper diagram (a) of FIG. 2, the focused spot 4 (FIG. 1) includes a linear preceding spot 42 positioned forward with respect to the moving direction 7 of the focused spot 4. The circular main spot 41 is located behind the preceding spot 42 and located away from the preceding spot 42. The preceding spot 42 and the main spot 41 having such a shape can be formed by the DOE 2.

  Further, as shown in the lower diagram (b) of FIG. 2, the laser oscillator 31 and the DOE 2 are configured so that the energy intensity of the preceding spot 42 is smaller than the energy intensity of the main spot 41. ing. In this way, the preceding spot 42 is heated more than necessary with sufficient energy intensity to gasify the surface dirt 8 so that the surface of the material 6 to be welded is not melted.

  The width dimension (longitudinal dimension of the preceding spot 42) W1 of the preceding spot 42 in the direction orthogonal to the moving direction 7 of the condensed spot 4 (an example of the direction intersecting the moving direction 7 of the condensed spot 4) is the main spot. The width dimension of the welded portion in the direction orthogonal to the moving direction 7 of the focused spot 4 formed at 41 (the dimension (diameter) in the direction parallel to the longitudinal direction of the preceding spot 42) W2 is larger. It is set with DOE2. With this configuration, a wider area including the welding area is heated with the preceding spot 42 to decompose the surface dirt 8 and generate gas to diffuse with respect to the welding area of the main spot 41. And surface dirt 8 can be removed more reliably.

  Further, the interval L between the preceding spot 42 and the main spot 41 is set so that the melting portion generated by the preceding spot 42 is caused by the main spot 41 in order to reliably obtain the cleaning effect of the surface of the workpiece 6 by the preceding spot 42. In order to prevent the cleaning effect from being obtained, the DOE 2 is set at an interval of 50 μm to 5 mm.

  The distance L along the moving direction 7 between the preceding spot 42 and the focused spot 4 is at least one time larger than the dimension along the moving direction 7 of the preceding spot 42.

  3A and 3B are schematic views of a cross section of the fusion zone 30 of the laser welding method according to the first embodiment of the present invention. The operation will be described using this.

  First, using the lens 3 and the diffractive optical element 2 with respect to the material to be welded 6, the laser beam 1 is condensed on the surface of the material to be welded 6, and the collected laser beam 1 is moved while being moved. 6 is irradiated to start welding. At this time, first, the preceding spot 42 of the focused spot 4 that is the focused laser beam 1 is irradiated on the surface of the material 6 to be welded including the welded portion to be welded. As shown in FIG. 3A, in the region irradiated with the preceding spot 42, the deposit or oxide surface contamination (substance other than the material to be welded) 8 existing on the surface of the workpiece 6 is removed from the preceding spot 42. Is heated to a temperature at which the surface dirt 8 is decomposed and gas is generated. That is, due to the preceding spot 42, the surface dirt 8 itself becomes a gas, and a generated gas 81 is generated. If the generated gas 81 is taken into the molten pool 51 and solidifies as it is, a welding defect occurs. However, in the first embodiment, since the predetermined interval L is maintained between the preceding spot 42 and the main spot 41, the main spot 41 is not immediately irradiated after the preceding spot 42 is irradiated, and the preceding spot 42 is not irradiated. The temperature of the region irradiated in step 1 temporarily decreases, and the generated gas 81 diffuses during that time (the time between the irradiation of the preceding spot 42 and the irradiation of the main spot 41). In order to promote the diffusion of the generated gas 81, an intake / exhaust device (not shown) may be provided. As a result, when the main spot 41 is irradiated and the molten pool 51 is generated by the main spot 41, the generated gas 81 generated in the preceding spot 42 is not already diffused and taken in, and welding defects such as porosity are not generated. It does not occur. Further, since the interval L exists between the preceding spot 42 and the main spot 41 in this way, the temperature of the portion heated by the preceding spot 42 is once lowered, and the main spot is continued from the preceding spot 42. When heated at the spot 41, overheating can be prevented. At this time, as shown in FIG. 3B, the preceding spot 42 is formed so that the melted welding depth 52 of the surface of the material 6 to be welded generated by the preceding spot 42 becomes shallower than the diameter 91 of the porosity allowed at the time of welding. The energy intensity is set. In the case of the first embodiment, as an example that can be implemented, the following parameters are used.

Energy intensity _{I 2} of the preceding spot 42 with respect to energy intensity _{I 1} of the main spot 41, and _{I 1 × 1% ≦ I 2} ≦ I 1 × 20%.

  The width dimension W1 of the preceding spot 42 in the direction orthogonal to the moving direction 7 of the focused spot 4 is 1 mm.

  An interval L between the preceding spot 42 and the main spot 41 is 150 μm.

  Further, in the first embodiment, since the surface state of the material 6 to be welded at the position where the main spot 41 is irradiated is a molten liquid, the absorption coefficient of the laser beam 1 is varied depending on the surface roughness as in the case of a solid. Since the absorption coefficient is a constant value depending on the material to be welded 6, the stable melting state is maintained.

  In the first embodiment, the DOE 2 is disposed in front of the lens 3 with respect to the traveling direction of the laser light 1, but the order may be reversed.

  According to the first embodiment, before the deposit 8 on the surface of the material 6 to be welded in front of the focused spot traveling direction 7 is deeply melted, it is cleaned and gasified from the preceding spot 42, and Since the predetermined interval L is maintained after the irradiation and before the irradiation of the main spot 41, the gasified before the irradiation of the main spot 41 can be diffused. Therefore, the probability of occurrence of porosity can be greatly reduced. Further, since the surface is melted at the preceding spot 42 before the main spot irradiation, the change in the absorptance on the surface of the main spot 41 is stabilized, and uniform melting can be obtained.

(Second Embodiment)
In the laser welding method and apparatus according to the second embodiment of the present invention, the shape of the beam profile is different from that of the first embodiment. 5A to 5D are schematic diagrams of various beam profiles in the laser welding method and apparatus according to the second embodiment of the present invention. These various beam profiles can be formed by DOE2. 5A to 5D, the same components as those in FIGS. 1 to 3B are denoted by the same reference numerals, and description thereof is omitted. Moreover, since the cross-sectional view of the welded portion 5 shown in the first embodiment and the cross-section of the welded portion 5 of the second embodiment are the same as those in FIGS. 3A and 3B, description thereof will be omitted.

  First, as shown in FIG. 5A, the main spot 41 can be divided into two, and the main spot 41 can be constituted by two circular divided main spots 41a and 41b. In such a configuration, by dividing the main spot 41 into two parts, the interface at the time of butt welding is brought between the divided main spots 41a and 41b divided into two, thereby generating porosity at the butt interface. Risk can be reduced. In the second embodiment, the number of divisions of the main spot 41 is two. However, it may be divided into an arbitrary number larger than two divisions.

  Next, as shown in FIG. 5B, the preceding spot 42 is divided into a plurality of divided preceding spots 42a, 42b, 42c, 42d, and 42e arranged on one straight line. It is characterized by a point-like aggregate. At this time, energy is distributed to the divided preceding spots 42a to 42e so that the surface of the workpiece 6 positioned between the divided preceding spots 42a to 42e is melted by the adjacent divided preceding spots 42a to 42e. As a result, it becomes possible to simplify the design of the DOE 2 such that the beam can be designed only by beam splitting. Further, it is possible to relatively reduce the energy allocated to the divided preceding spots 42a to 42e. At this time, the relationship between the spot diameter and the spot interval of the divided preceding spots 42a to 42e is (spot interval = 2 to 10 times the spot diameter).

  Further, as shown in FIG. 5C, the arrangement of the divided preceding spots 42a to 42e is a curved curve as if closing to the main spot 41 side, in other words, the center of the radius of curvature is in the moving direction 7 of the focused spot 4. You may arrange | position on the curve arrange | positioned at the main spot 41 side. By arranging the preceding divided spots 42a to 42e in a curved manner in this way, the distance from the main spot 41 becomes equal, and the efficiency of the preheating effect on the main spot 41 increases. Has the effect of reducing.

  FIG. 5D is characterized in that the preceding spots 42a to 42l are arranged so as to surround the main spot 41 in a point-symmetric manner (in other words, so as to surround the periphery of the main spot 41). As a result, there is no restriction on the moving direction 7 of the focused spot 4 and the relative arrangement of the beam profile, and the weld defect suppressing effect is exhibited no matter which direction the focused spot 4 is moved.

  In the second embodiment, five divided preceding spots 42a to 42e and ten divided preceding spots 42a to 42l are provided as the preceding spot 42. However, the number of divisions is not limited to them, and is linear to many. It may be the number of preceding spots.

  In addition, it can be made to show the effect which each has by combining arbitrary embodiment or modification of the said various embodiment or modification suitably.

  The laser welding method and apparatus of the present invention have the effect of suppressing the occurrence of welding defects by providing a preceding spot in the beam profile of the condensing spot portion without providing a preliminary cleaning step, etc., and sealing welding in a storage battery It can also be applied to welding applications where the occurrence of defects such as these is not allowed.

1 Laser light 2 DOE
DESCRIPTION OF SYMBOLS 3 Lens 30 Laser welding apparatus 31 Laser oscillator 4 Condensing spot 41 Main spot 41a, 41b Division | segmentation main spot 42 Advance spot 42a-42l Division precedence spot 5 Welding part 51 Molten pool 52 Melting depth 6 Welding material 7 Focus spot Movement direction 8 Surface contamination 81 Generated gas 9 Porosity 91 Porosity diameter 101 Metal case 102 Lid 104, 104a to 104c Laser spot 202A ... Branch beam 204 ... Diffractive optical element 210 ... Crystal resonator 211, 212 ... Crystal resonator connection terminal 221 , 222 ... Terminal for crystal resonator on substrate

Claims (10)

In a method for performing welding by irradiating a workpiece with a laser beam condensed using a lens and a diffractive optical element,
As the diffractive optical element, a focused spot on the workpiece to be welded by the laser light is disposed in front of the focused spot in the traveling direction of the focused spot, away from the preceding spot, and is welded. A main spot for melting the material, and when irradiating the surface of the material to be welded with the preceding spot, the gas other than the material to be welded adhered to the surface of the material to be welded is decomposed and gas While using a diffractive optical element that is heated to a temperature that generates or higher and the energy intensity is set so that the melting depth from the surface of the workpiece to be welded is shallower than the allowable porosity diameter,
Irradiating the surface of the material to be welded with the preceding spot to decompose the substance other than the material to be welded attached to the surface of the material to be welded to generate the gas,
After the irradiation of the preceding spot, the generated gas is diffused before being irradiated at the main spot,
Then, the surface of the material to be welded is irradiated at the main spot to melt the material to be welded ,
The preceding spot is linear, the longitudinal direction of the linear preceding spot is a direction intersecting the moving direction of the focused spot, and the longitudinal dimension of the linear preceding spot is and larger than the width of the main spot in the direction parallel to the longitudinal direction, including the area for melting the material to be welded in the main spot, you irradiating a wider area of the preceding spot the linear,
Laser welding method.   Maintaining an interval between the preceding spot and the main spot such that the gas generated at the preceding spot diffuses before the irradiation of the main spot, and separating the main spot from the preceding spot, After irradiation of the preceding spot and before irradiation of the main spot, a time for the gas generated at the preceding spot to be diffused is secured, and after irradiation of the preceding spot is completed, irradiation is performed at the main spot. The laser welding method according to claim 1, wherein the generated gas is diffused before starting. The laser welding method according to claim 1 or 2 , wherein the preceding spot is composed of a plurality of divided preceding spots, and the surface of the workpiece is irradiated with the plurality of divided preceding spots as the preceding spots. The laser welding method according to claim 3 , wherein the plurality of divided preceding spots are configured to surround a periphery of the main spot, and the surface of the workpiece is irradiated with the plurality of divided preceding spots as the preceding spots.   2. The laser welding according to claim 1, wherein the main spot is composed of a plurality of divided main spots, and the surface of the material to be welded is irradiated with the plurality of divided main spots as the main spots to melt the material to be welded. Method. In a laser welding apparatus for performing welding by irradiating a welded material while moving a laser beam condensed using a lens and a diffractive optical element,
As the diffractive optical element, a focused spot on the workpiece to be welded by the laser light is disposed in front of the focused spot in the traveling direction of the focused spot, away from the preceding spot, and is welded. A main spot for melting the material, and when irradiating the surface of the material to be welded with the preceding spot, the gas other than the material to be welded adhered to the surface of the material to be welded is decomposed and gas Using a diffractive optical element that is heated to a temperature higher than the temperature at which it is generated and the energy intensity is set so that the melting depth from the surface of the workpiece to be welded is shallower than the allowable porosity diameter ,
The preceding spot is linear, the longitudinal direction of the linear preceding spot is a direction intersecting the moving direction of the focused spot, and the longitudinal dimension of the linear preceding spot is A laser welding apparatus larger than the width dimension of the main spot in a direction parallel to the longitudinal direction . The main spot is separated from the preceding spot by maintaining an interval between the preceding spot and the main spot such that the gas generated at the preceding spot diffuses before the irradiation of the main spot. Item 7. The laser welding apparatus according to Item 6 . The laser welding apparatus according to claim 6 or 7 , wherein the preceding spot is composed of a plurality of divided preceding spots. The laser welding apparatus according to claim 8 , wherein the plurality of divided preceding spots are configured to surround a periphery of the main spot. The laser welding apparatus according to claim 6 , wherein the main spot is composed of a plurality of divided main spots.

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