Laser welding device and laser welding method

Abstract

To provide a laser welding device which performs pinpoint welding to join a keeper body of a keeper forming a magnetic dental artificial tooth attachment to a holder, and to provide a laser welding method.SOLUTION: A laser welding device includes: a keeper body supply device unit 10 on which a keeper body 2 is placed and fixed; a holder supply device unit 20 on which a holder 3 is laterally installed and fixed; a positioning device unit which specifies positions of the keeper body and the holder; a laser welding device unit 30 formed by integrally assembling a laser welding device 31 which radiates a laser to each contact portion between the keeper body and the holder and a laser welding work observation device 32 which observes laser welding work of the contact portions; and a take-out device. The device is provided that radiates the laser to the contact portions at the lower side of a diameter of the holder and the upper side of the diameter from both sides to perform laser-welding at four points in total.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a welding apparatus and a welding method for welding a keeper body and a holder of a keeper that constitutes a magnetic denture attachment. [Background technology]

[0002] The keeper 50, one element of a denture attachment that utilizes magnetic attraction, consists of a thin, disk-shaped keeper body 501 and a thin rod-shaped holder 502, and is usually fixed to a root surface plate 503 by casting. Figure 5 shows the structure of the root surface plate 503, which includes a holder 502 for fixing the keeper in a mold so that it can be securely fixed in a predetermined position within the mold. During the fitting process to accurately position the keeper 50 on the root surface plate 503, the holder 502 is bent and held from outside the mold, and then a casting alloy heated to 1050°C is poured in as a feeder and replaced with wax to form a root surface plate integrated with the keeper. The holder portion exposed from the root surface plate is then cut away.

[0003] Patent Document 1 discloses a method for joining the keeper body and the holder. As shown in Fig. 6, keeper body 601 and holder 602 are joined at two welding spots by irradiating joint 605 with a laser beam. Therefore, as shown in Fig. 6, joint 605 between the keeper body and holder is not joined entirely, and the joint area is small. Also, the joint between holder 602 and keeper body 601 is recessed and thin. For this reason, the holder often breaks at the bent portion during the fitting process, and the company discloses a solution to this problem.

[0004] 7 and 8, the disclosure states that when joining holder 702 to the side surface of keeper body 701, the entire joining surface of holder 702 is melted by irradiating it from two directions simultaneously, and then welded to the side surface of keeper body 701. When joining, holder 702 is pressed against the side surface of keeper body 701 with a pressing force of 0.3 to 1.5 kgf, thereby forming molten zone 711 in which the entire joining surface is melted. Moreover, molten zone 711 is larger than the thickness of holder 702.

[0005] In the method of Patent Document 1, the molten zone 711, where the entire joining surface is melted, is thicker than the holder 702, and therefore the keeper body 701 is made of 17Cr-2Mo-Ti steel, which is a ferritic stainless steel, as disclosed in Table 1, and the grains of the ferritic stainless steel become coarse. The heat-affected zone 712, where the grains become coarse, becomes brittle and its strength deteriorates, particularly its bending strength. As shown in Figure 5, this caused problems such as fracture at the joining zone when the holder was bent. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-276294 Summary of the Invention [Problem to be solved by the invention]

[0007] When bending the holder, if there is a depression in the weld or if the joint area is small, as shown in Figure 6, problems occur with the joint breaking. Also, if the fusion zone is firmly joined across the entire contact surface as shown in Figure 8, the ferrite grains in the heat-affected zone on the keeper side become coarse and embrittled, causing problems with breakage at that location. In other words, if the welding heat capacity is small, the small joint area becomes a problem, and if it is large, the heat-affected zone becomes embrittled, causing problems, which is a troublesome issue. The object of the present invention is to find a way to solve the problem of breakage at the laser welded joint between the keeper body and the holder when bending the holder, and to invent a laser welding method and laser welding device that will achieve this. [Means for solving the problem]

[0008] In order to achieve the above object, the inventors realized through trial and error that an appropriate solution could not be found because the conventional method involved irradiating the laser from two positions, from the left and right, and discovered that the problem could be solved by adopting a laser irradiation method from four positions. Two laser irradiation devices were fabricated as shown in Figure 1, and the laser irradiation points were set at four points above and below the center of the holder, ensuring sufficient joint strength across the entire circumference of the holder as shown in Figure 3. At the same time, as shown in Figure 4, the center of the holder did not melt, and the heat-affected zone did not extend to the ferrite structure (ferrite phase) of the keeper body, and no coarsening of the crystal grains was observed. This four-point irradiation method succeeded in melting the entire circumference of the holder to ensure sufficient strength, while suppressing the supply of excessive heat and preventing the embrittlement of the ferrite phase. This successfully solved the problem of breakage during holder bending.

[0009] However, it was a difficult task to create a laser welding device that would allow a 0.2 mm diameter holder to be attached to the side of a keeper and irradiate the four points of the attachment point with a laser symmetrically. The inventors invented a structure that ensures the precise positioning of the keeper and holder, a mechanism to adjust the amount of pressure required to stabilize this positional relationship, and a mechanism that moves the laser welding irradiation position to symmetrically position the four irradiation points.

[0010] The laser welding device according to the present invention comprises: a first base having a recess for accommodating a keeper body, and a first weight for fixing the keeper body to the first base; a keeper body supplying device unit comprising: a second base having a groove for horizontally placing the holder; a drive device for moving the second base in the longitudinal direction of the holder; a holder supplying device unit including a second weight for fixing the holder to the second base; a positioning adjustment unit for adjusting the positions of the keeper body and the holder, and a device for applying an appropriate amount of pressure; a laser welding device unit which is integrally assembled with a laser welding device that irradiates a laser beam from the side of the contact portion between the keeper body and the holder, and a laser welding operation observation device that observes the contact portion between the keeper body and the holder and the laser irradiation, and which is movable in the vertical direction; a take-out device for taking out the keeper, which is made by laser welding the keeper body and the holder; The drive device brings the holder into vertical contact with the side of the keeper body, and then the lower central position of the holder is laser-welded to the contact point of the holder by irradiating it with laser from both sides, and the laser welding device unit is moved in the vertical direction, and the upper central position of the holder is laser-welded by irradiating it with laser from both sides, thereby laser-welding a total of four points.

[0011] The keeper body is made of magnetic stainless steel and is a disk-shaped object with a diameter of 2 mm to 6 mm and a thickness of 0.3 mm to 1 mm. The holder is made of austenitic stainless steel and is made of a thin wire with a diameter of 0.2 mm to 0.6 mm and a length of 10 mm to 20 mm. The holder is attached to the side of the keeper body and bent to hold it, so its diameter needs to be approximately 60% or less of the keeper's thickness. However, if the diameter is too small, it will be too weak to hold the object, so a diameter of 0.2 mm or more is required.

[0012] The method is characterized by spraying Ar gas from an Ar gas spraying device onto the contact area between the keeper body and the holder in conjunction with laser irradiation from both sides. This is to prevent oxygen from penetrating the molten joint during welding, which would embrittle the joint. This ensures a molten joint with great strength.

[0013] In addition, a laser welding method for welding a keeper body and a holder of a keeper constituting a magnetic denture attachment is as follows: The first step comprises placing the keeper body and the holder on their respective bases; (1) The keeper body is disposed in a recess provided in an end portion of an upper surface of the first seat, with the laser welded portion extending beyond the first seat; (2) Then, the keeper body has its upper surface fixed to the first base by a first weight, (3) The holder is provided with a groove formed in an upper surface end portion of a second base opposite the first base, facing the recess and in a direction of the recess, with the laser welded portion extending beyond the groove, (4) Then, the holder is fixed at its upper surface by a second weight, (5) The second seat, which is held on a driving device that reciprocates in the groove direction, moves forward toward the first seat, and the keeper body and the holder are brought into contact with each other with an appropriate load. the second step comprises a step of laser welding the contact portion between the keeper body and the holder, (6) Start spraying Ar gas onto the contact area between the keeper body and the holder, (7) A laser welding work observation device is integrated with a laser welding device installed in two opposing directions on the lower side of the diameter of the holder at the abutting portion to identify a laser irradiation position, and at the same time, a laser is irradiated from the laser welding device to pinpoint the laser to partially join the abutting portion, (8) Next, the laser welding device and the laser welding work observation device are raised by a vertically moving drive device, and the laser welding work observation device is used to identify the laser irradiation position above the holder, and at the same time, the laser welding device irradiates the laser at a pinpoint to partially join the abutting portions, (9) The spraying of the Ar gas is terminated, a third step of removing the keeper, in which the keeper body and the holder have been integrated by laser welding, from the laser welding device; (9) removing the first weight and the second weight from the top surfaces of the first stage and the second stage, respectively; (10) removing the keeper from the recess of the first stage and the groove of the second stage using an ejection device; It is characterized by: [Effects of the Invention]

[0014] According to the present invention, by using four laser welds irradiated with a laser at pinpoint locations, a molten zone is formed around the entire circumference of the abutting wire, ensuring high bending strength and making it possible to reduce the heat-affected zone of the keeper body, thereby preventing the coarsening of crystal grains and preventing deterioration of welding strength and bending strength. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a laser welding device according to an embodiment; [Figure 2] 10 is a diagram showing a first irradiation position and a second irradiation position relative to the contact portion between the keeper body and the holder in the embodiment. FIG. [Figure 3] 10 is a view showing a fused portion around the entire periphery of the holder and a non-fused portion in the center of the joint portion between the keeper body and the holder. FIG. [Figure 4] 10A and 10B are diagrams showing the welded portion and its heat-affected portion at the joint between the keeper body and the holder. [Figure 5] FIG. 10 is a diagram showing bending of the holder to form a root surface plate. [Figure 6] 10A and 10B are diagrams showing a joint between a keeper body and a holder according to a conventional joining method. [Figure 7] FIG. 1 is a diagram (FIG. 1) showing a method of joining a keeper body and a holder disclosed in Patent Document 1. [Figure 8] FIG. 1 is a diagram showing a heat-affected zone in the state of the joint between the keeper body and the holder (FIG. 2) disclosed in Patent Document 1. BEST MODE FOR CARRYING OUT THE INVENTION

[0016] A laser device according to one embodiment of the present invention will be described in detail with reference to FIGS. First, this is an apparatus and method for manufacturing a keeper that constitutes a magnetic denture attachment by butting (contacting) a holder to the side of a disk-shaped keeper body and welding it by pinpoint laser irradiation. The keeper body is a small disk made of ferritic magnetic stainless steel, 2mm to 6mm in diameter and 0.4mm to 1mm in thickness. The mating holder is a thin wire made of austenitic stainless steel, 0.2mm to 0.6mm in diameter and 10mm to 20mm in length. The butt joint (contact area) is laser welded in two places by applying a first laser irradiation to pinpoint points on both sides below the center of the outer periphery of the holder, which has a diameter of 0.2 mm to 0.6 mm, and then applying a second laser irradiation to pinpoint points on both sides above the center, for a total of four laser welds. The configuration of the laser device will be described below.

[0017] <Configuration of laser welding equipment> The laser welding device consists of a supply device section that supplies, positions, and fixes the keeper body and holder, a welding device section that irradiates the laser and observes the laser irradiation position, and a removal device section that removes the laser-welded product after laser welding is completed.

[0018] <Feeding device section> As shown in FIGS. 1 and 2, the supply device section is made up of a keeper body supply device section 10 and a holder supply device section 20. As shown in FIG. The keeper body supply device unit 10 comprises a first pedestal 11 having a recess 12 in which the keeper body 2 is disposed, and a first weight 13 that fixes the keeper body 2 to the first pedestal 11 from above. The holder supply device unit 20 comprises a second pedestal 21 having a groove 22 in which the holder 3 is placed horizontally, a second weight 23 that fixes the holder 3 from above, and a drive device 24 that places the holder 3 in the groove 22 and then abuts the holder 3 against the keeper body 2 on the first pedestal, applying a predetermined pressing force and moving the second pedestal 21 back and forth.

[0019] A recess 12 is formed at the edge of the top surface of first pedestal 11 so that a small circular plate with a diameter of 2 mm to 6 mm can be placed therein for laser welding. The shape of the recess 12 is an inverted triangle in the example of FIG. 1, but it may also be a square or other shape. The size of the recess 12 is larger than the diameter of the small circular plate so that it will not fall off the first pedestal, while ensuring that the protruding portion of the circular plate can be secured so that the first pedestal is not irradiated with the laser during laser welding. The depth of recess 12 should be equal to or greater than that of a small circular plate having a thickness of 0.4 mm to 1 mm, and should be such that the keeper body can be fixed by first weight 13. This is to maintain the contact area between the keeper body and the holder during laser welding.

[0020] A groove 22 is formed in the longitudinal direction of the central part from the tip of the second base 21 so that a thin wire having a diameter of 0.2 mm to 0.6 mm and a length of 10 mm to 20 mm can be laid horizontally for laser welding and can be butted against the keeper body 2 on the first base 11. The size of groove 22 is preferably a depth equivalent to the diameter of the thin wire. It is sufficient if the holder can be fixed by second weight 23. The length is sufficient if a protruding portion is secured so that second pedestal 21 is not irradiated with laser light when the second pedestal is brought into contact with the keeper body and the contact area is laser-welded.

[0021] A positioning adjustment part (not shown) is provided for positioning the keeper body 2 and the holder 3, in other words, for positioning the contact part. The positioning adjustment unit for positioning the keeper body 2 and the holder 3 is a mechanism that fixes the first base 11 on which the keeper body 2 is mounted and moves the holder 3 in the lateral direction (X direction). For example, it may be combined with a micrometer that is capable of minute movements. Next, a driving device 24 may be used as a mechanism for adjusting the second base 21 in the X direction relative to the first base 11 so that the center point of the disk of the keeper body 2 is on an extension of the longitudinal direction of the holder 3 (Y direction). In this example, a spring mechanism is used as the driving force. The spring stress is just enough to butt the keeper body and the holder together and maintain that state, so no pressing force is required. This creates a fusion zone that corresponds to pinpoint welding, and prevents the formation of a fusion volume greater than the thickness of the holder.

[0022] The positioning (in the Z direction) of the keeper body 2 and holder 3, i.e., the position (upper, lower, or center as shown in Figure 2) of the holder 3 relative to the side of the keeper body 2, is determined by a mechanism that moves one of the pedestals up and down in the Z direction. For example, this may be combined with a micrometer that is capable of minute movements.

[0023] <Laser welding equipment section> It consists of a laser welding device 31 that irradiates the contact point between the keeper body 2 and the holder 3 with a laser from the side, and a laser welding work observation device 32 that observes the contact point between the keeper body 2 and the holder 3 and the laser irradiation, and both devices are assembled together and can be driven in the vertical direction (Z direction). This laser welding device allows pinpoint laser irradiation of the contact area from both sides simultaneously with an accuracy of 0.01 mm, thereby reducing the size of the melted area and the heat-affected area.

[0024] After the holder 3 is brought into contact with the side surface of the keeper body 2 perpendicularly by the drive device 24 of the supply device part, The laser welding work observation device 32 adjusts and identifies the laser irradiation points (311, 312). As the first laser welding, a laser is irradiated simultaneously from both sides to the abutment portion 311 on the lower diameter side of the holder 3. Next, as the second laser welding, the laser welding device unit is moved upward (in the Z direction) so that abutment portion 312 on the upper diameter side of the holder 3 can be irradiated simultaneously from both sides, and laser irradiation is performed. These two laser irradiations result in a total of four points being laser welded. As shown in Figure 3, the melted zones 41 at the four laser irradiation points spread all around the outer diameter of the holder 3, ensuring sufficient bending strength. In addition, there are no melted zones in the abutting center, which limits the amount of welding heat and prevents the coarsening of the crystal grains of the keeper ferrite phase and the expansion of the heat-affected zone, which is preferable in terms of bending strength.

[0025] FIG. 4 shows a cross-sectional view of the fusion zone 41 formed by this laser welding, taken along the line a-a' in the thickness direction. Also shown in FIG. 4 is the heat-affected zone 402 (A, B). The fusion zone 401 is a mixed alloy of an 18Cr-8Ni austenite phase and a 17Cr-1Mo ferrite phase, and has a two-phase structure of austenite and ferrite. A heat-affected zone 402A extends into the austenite phase of the holder 3, but is not embrittled. A heat-affected zone 402F is formed in the ferrite phase of the keeper body 2, but it is very small, and grain coarsening is suppressed.

[0026] In order to prevent oxidation of the contact area between the keeper body 2 and the holder 3 due to the heat generated during laser welding, an Ar gas spraying device that sprays Ar gas in conjunction with laser irradiation from both sides is installed between the keeper body supply device section 10 and the laser welding device section (not shown). [Example]

[0027] In Example 1, a keeper body with a diameter of 4 mm and a thickness of 0.8 mm was placed in the recess of the first base, and a holder with a diameter of 0.4 mm and a length of 10 mm was placed horizontally in the groove of the second base.The two were then butted against the lower part of the side of the keeper body, and laser welding was performed by irradiating a laser while spraying Ar gas. As a result, it was found that four laser welds were made at approximately equal intervals around the circumference of the contact area. The weld strength was sufficient for all 10 welds, and the joint between the keeper body and the holder did not withstand five bending tests. [Industrial Applicability]

[0028] The present invention makes it possible to stably perform the bending operation of the holder when fixing the keeper of a magnetic denture attachment to a root plate, and is expected to be used widely in the dental field. [Explanation of symbols]

[0029] 1: Welding equipment 2:Keeper body 3: Holder 10:Keeper main body supply device section 11:First pedestal 12: Dent 13:First spindle 20: Holder supply device section 21: Second pedestal 22: Groove 23:Second weight 24: Drive unit 30: Laser welding equipment section 31: Laser welding equipment 32: Laser welding work observation device 331: First laser irradiation point (bottom center of holder) 332: Second laser irradiation point (upper center of holder) 401: Fusion zone of a two-phase structure consisting of austenite and ferrite phases 402A: Heat-affected zone of the austenite phase of the holder 402B: Heat-affected zone of ferrite phase of keeper body 41: Welding section 5: Casting of root plate 501:Keeper body 502: Holder 503: root plate 6: Keeper 601:Keeper body 602: Holder 605: Joint 7: Keeper 701:Keeper body 702: Holder 711: Welding section 712: Heat-affected zone

Claims

1. The laser welding device that welds the keeper body and holder of the keeper that constitutes the magnetic denture attachment is a first base having a recess for accommodating the keeper body; and a second base for fixing the keeper body to the first base. a keeper body supplying device part consisting of a first weight; a second base having a groove for horizontally supporting the holder; a second base for moving the second base in the longitudinal direction of the holder; a holder supplying device unit including a drive unit for driving the holder and a second weight for fixing the holder to the second base; a positioning adjustment unit for adjusting the positions of the keeper body and the holder; a laser welding device unit which is integrally assembled with a laser welding device that irradiates a laser beam from the side of the contact portion between the keeper body and the holder, and a laser welding operation observation device that observes the contact portion between the keeper body and the holder and the laser irradiation, and which is movable in the vertical direction; a take-out device for taking out the keeper, the keeper body and the holder being fabricated by laser welding; Equipped with A laser welding device characterized in that the drive device brings the holder into vertical contact with the side of the keeper body, laser-welds the lower central position of the holder to the contact point of the holder by irradiating laser from both sides, and moves the laser welding device unit in the vertical direction, and laser-welds the upper central position of the holder by irradiating laser from both sides, thereby laser-welding a total of four points.

2. In claim 1, The keeper body is made of magnetic stainless steel and has a disk shape with a diameter of 2 mm to 6 mm and a thickness of 0.4 mm to 1 mm. The laser welding device is characterized in that the holder is made of stainless steel and is made of a thin wire having a diameter of 0.2 mm to 0.6 mm and a length of 10 mm to 20 mm.

3. In claim 1, A laser welding device characterized in that Ar gas is sprayed from an Ar gas spraying device onto the contact portion between the keeper body and the holder in conjunction with laser irradiation from both sides.

4. The laser welding method for welding the keeper body and holder of the keeper constituting the magnetic denture attachment is as follows: The first step comprises placing the keeper body and the holder on their respective bases; (1) The keeper body is disposed in a recess provided in an end portion of an upper surface of the first seat, with a laser-welded portion extending beyond the first seat; (2) Then, the keeper body is fixed at its upper surface to the first base by a first weight, (3) The holder is provided with a groove formed in an end portion of an upper surface of a second seat facing the first seat, facing the recess in the direction of the recess, with the laser welded portion extending beyond the groove, (4) Then, the holder is fixed at its upper surface by a second weight, (5) The second seat, which is held on a driving device that reciprocates in the groove direction, moves forward toward the first seat, and the keeper body and the holder come into contact with each other with an appropriate load applied. the second step comprises a step of laser welding the contact portion between the keeper body and the holder, (6) Start spraying Ar gas onto the contact area between the keeper body and the holder, (7) A laser welding operation observation device integrated with laser welding devices installed in two opposing directions on the lower diameter side of the holder at the abutting portion is used to identify the laser irradiation position, and at the same time, a laser is irradiated from the laser welding device to pinpoint the laser to partially join the abutting portion; (8) Next, the laser welding device and the laser welding work observation device are raised by a vertically moving drive device, and the laser welding work observation device identifies a laser irradiation position above the holder, and at the same time, the laser welding device irradiates a laser beam at a pinpoint to partially join the contact portions. (9) The spraying of the Ar gas is terminated, a third step of removing the keeper, in which the keeper body and the holder have been integrated by laser welding, from the laser welding device; (9) removing the first weight and the second weight from the upper surfaces of the first base and the second base, respectively; (10) removing the keeper from the recess of the first base and the groove of the second base using a removal device; A laser welding method characterized by:

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