Keeper for dental attachment and method of manufacturing the same

Abstract

To provide a keeper constituting a denture attachment and a method for manufacturing the same.SOLUTION: A keeper 3 in which a holder 32 is brought into contact with a main side surface of a keeper main body 31, laser welding is simultaneously performed from both sides with respect to a contact portion on a lower side of a diameter of the holder, next, laser welding is simultaneously performed from both sides with respect to a contact portion on an upper side of the diameter of the holder, a center portion of a contact surface is in a contact state between an unmelted keeper main body and the holder, an outer peripheral portion thereof becomes a melted portion 34, and a joint portion is formed, and the melted portion of the contact portion forms a melted portion smaller than a radius of the holder by laser welding at four places.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a keeper for a denture attachment that constitutes a denture attachment, and a method for manufacturing the keeper. [Background technology]

[0002] The keeper 70, an element of a denture attachment that utilizes magnetic attraction, consists of a thin, disk-shaped keeper body 701 and a thin rod-shaped holder 702, and is typically fixed to a root surface plate 703 by casting. Figure 7 shows the structure of the root surface plate 703, which includes a holder 702 for fixing the keeper in the mold so that it can be securely fixed in the desired position within the mold. During the fitting process to accurately position the keeper 70 on the root surface plate 703, the holder 702 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 portion of the holder 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. Conventionally, as shown in FIG. 8, a keeper body 801 and a holder 802 are joined at two welding spots by irradiating a joint 805 with a laser beam. As a result, as shown in FIG. 8, the joint 805 between the keeper body and the holder is not joined entirely, and the joint area is small. Furthermore, the joint between the holder 802 and the keeper body 801 is recessed and thin. For this reason, the holder often breaks at the bent portion during the fitting process, a problem that has been raised, and a solution to this problem is disclosed.

[0004] 9 and 10, the disclosure states that when joining holder 902 to the side surface of keeper body 901, the entire joining surface of holder 902 is melted by irradiating it from two directions simultaneously, and then welded to the side surface of keeper body 901. Furthermore, when joining holder 902, by pressing it against the side surface of keeper body 901 with a pressing force of 0.3 to 1.5 kgf, a molten zone 1011 is formed in which the entire joining surface is melted. Moreover, this molten zone 1011 is larger than the thickness of holder 1002.

[0005] In the method of Patent Document 1, the molten zone 1011, where the entire joining surface is melted, is thicker than the holder 1002, and therefore the keeper body 1001 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 1012, where the grains become coarse, becomes brittle and its strength deteriorates, particularly its bending strength, and this causes problems such as breakage at the joining zone when the holder is 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 8, problems occur in which the joint breaks. Also, if the fusion zone is firmly joined across the entire contact surface as shown in Figure 10, the crystal grains of the ferrite structure 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 and the joint area is small, problems occur, 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 keeper and a manufacturing method thereof that solves the problem of breakage at the laser-welded joint between the keeper body and the holder when bending the holder. [Means for solving the problem]

[0008] In order to achieve the above object, the inventors found through trial and error that the contact surface of the holder that contacts the side of the keeper body is in a state of contact between the two at the center, with no change in structure, and only the outer periphery is welded to form a joint, and the molten part of the holder is smaller than the radius of the holder. The fact that the center of the contact surface between the keeper body and the holder remains in contact indicates that the amount of heat generated during laser welding was small, which means that the grain size of the ferrite structure in the heat-affected zone on the keeper body side did not become coarse. Also, the fact that the fused part of the holder is smaller than the radius of the holder means that this reduced fused part contributes to the formation of the joint surface between the keeper body and the holder.

[0009] The manufacturing method for the above-mentioned keeper involves applying appropriate welding conditions, i.e., supplying an appropriate amount of heat, so that the entire circumference of the holder is melted to maintain sufficient strength while leaving the central part (core part) of the joining surface intact. In laser irradiation, the number of irradiation points has been doubled from the conventional two to four, halving the amount of heat per point, and the irradiation position is four equally spaced points on the outer periphery of the holder, from the contact surface to the contact point on the holder side, resulting in two-stage laser welding.The first laser welding is performed from both sides at the contact point on the lower diameter of the holder, and the second laser welding is performed from both sides at the contact point on the upper diameter of the holder. Here, in the laser welding of this method, the keeper body and holder are placed horizontally with the holder abutting the keeper body, and this abutment state is maintained during welding, so a slight pressing force of more than 0 kgf to 0.2 kgf is required to abut the holder against the side of the keeper body. This four-point irradiation method melts the entire circumference of the holder to ensure sufficient strength while supplying an appropriate amount of heat, that is, by controlling the amount of heat supplied to be neither too small nor too large, it was possible to ensure sufficient welding strength and successfully solve the problem of breakage during the holder bending process. [Effects of the Invention]

[0010] According to the present invention, laser welding at four points irradiated with a laser does not melt the core part of the abutting holder, but forms a molten zone only around the entire circumference of the holder, and by reducing the heat-affected zone on the keeper body side, coarsening of the crystal grains is prevented, thereby successfully achieving high welding strength and bending strength, and realizing the effect of reducing work problems when attaching the keeper to the root surface plate. [Brief explanation of the drawings]

[0011] [Figure 1] 10A and 10B are diagrams showing a method of joining the keeper body and the holder in the embodiment. [Figure 2] 10A and 10B are diagrams showing the first and second irradiation positions for the contact portion between the keeper body and the holder in the embodiment. [Figure 3] FIG. 10 is a cross-sectional view showing four laser irradiation positions at the contact portion of the holder and the melted portion after laser irradiation. [Figure 4] 10 is a diagram showing a fusion zone at the joint between the keeper body and the holder. FIG. [Figure 5] 5A and 5B are cross-sectional views taken along lines a-a', bb', and cc' in FIG. 4. [Figure 6] A perspective view of a keeper in an embodiment and a cross-sectional view of d-d' in the thickness direction are shown. [Figure 7] FIG. 1 is a diagram showing the structure of a root surface plate. [Figure 8] 10 is a diagram showing the retaining rod that has become concave and thin due to the small bonding area caused by the bonding between the keeper body and the retaining rod. FIG. [Figure 9] FIG. 1 is a diagram (FIG. 1) showing a method of joining a keeper body and a holder disclosed in Patent Document 1. [Figure 10]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

[0012] The first embodiment of the present invention is The keeper body of the keeper constituting the denture attachment and one end of the keeper body are aligned with the side of the keeper body. A keeper for a denture attachment comprising a holder that is physically fixed to the denture, The keeper body is made of ferritic magnetic stainless steel, and the holder is made of austenitic Made of stainless steel, The keeper body and the holder are in contact with each other at the side of the keeper body, and the contact surface is This relates to a keeper for a denture attachment, characterized in that the central part is in contact with the other, there is no change in the structure, the outer periphery forms a joint consisting of a fused part, and the fused part is smaller than the radius of the holder.

[0013] In addition, the second embodiment is The keeper body of the keeper constituting the denture attachment and one end of the keeper body are aligned with the side of the keeper body. A method for manufacturing a keeper for a denture attachment comprising a holder to be physically fixed to the denture attachment, abutting the holder toward the main side of the keeper body; The first laser welding is performed by simultaneously irradiating the contact area on the lower diameter of the holder from both sides, Next, the second laser welding is performed by simultaneously irradiating the abutting part on the upper diameter of the holder from both sides. The present invention relates to a method for manufacturing a keeper for a denture attachment, characterized in that a fused portion having a smaller radius than the holder is formed by melt-joining the outer periphery of the contact surface between the holder and the keeper body.

[0014] This will be explained in detail below. The keeper constituting the denture attachment comprises a keeper body and a holder, one end of which is fixed integrally to the side of the keeper body. The keeper body is circular and made of ferritic magnetic stainless steel such as SUS434 or 444. It is a small disk-shaped body with a diameter of 2 to 6 mm and a thickness of 0.4 to 1 mm. The holder that it comes into contact with is a thin wire made of austenitic stainless steel such as SUS304 or 316, with a diameter of 0.2 to 0.6 mm and a length of 10 to 20 mm.

[0015] The keeper body and the holder are abutted against the side of the keeper body, and the center of the abutting surface is in contact with the keeper body and the holder. Here, abutting means that the two are in contact and that the holder is placed horizontally on the side of the keeper body to laser weld them together, and that they are in a butted state during laser welding. The pressing pressure required for this is a slight pressure of more than 0 kgf to 0.2 kgf. "The centers are in contact" means that the ferrite structure of the adjacent keeper body and the austenite structure of the holder remain, and they are not fused together.

[0016] The outer periphery of the holder that is in contact with the keeper body is melted by laser welding to form a fused zone, which becomes the outer periphery of the joint. Note that the inside of the joint is in the above-mentioned contact state. Furthermore, the molten zone at the contact point on the holder side of the contact surface is smaller than the radius of the holder. This is because the outer periphery of the keeper body is rounded and the end face of the holder is flat, so the contact surface forms a line contact in the thickness direction of the keeper body, and tiny gaps are formed on both sides of the line contact. The initial molten stainless steel of the holder flows away due to the heat of the laser irradiation on the contact point, filling this gap, and the molten zone becomes smaller than the radius of the holder.

[0017] Next, the manufacturing method will be described. The keeper body is placed on the first pedestal, and the holder is placed on the adjacent second pedestal. The height of the second pedestal is adjusted so that the center of the keeper body's main side is aligned with the holder's radial center. The holder is then horizontally abutted against the keeper body's main side. To ensure that the keeper body, placed on the pedestal, maintains contact with the holder's end face for laser welding, the holder is pressed against the keeper body with a slight force of 0 kfg to 0.2 kgf. If the holder is not pressed against the keeper body at all, the impact of the laser welding will make it impossible to maintain the abutment state, and laser welding itself will not be possible. Furthermore, if the pressing force is too great, the laser heat will melt the holder deep into the interior, causing the molten area to grow thicker and the ferrite grains in the keeper body to coarsen.

[0018] Laser welding involves two laser irradiations, as shown in Figures 1 and 2. With the holder 12 in contact with the main side surface of the keeper body 11, lasers are irradiated from both sides of the holder 12 by laser irradiation devices LS1 and LS2 facing each other. A first laser irradiation LS11 is performed from both sides to the abutment portion 212 on the lower diameter side of the holder 22. Next, the laser irradiation devices LS1 and LS2 are raised above the first laser irradiation, and a second laser irradiation LS12 is performed from both sides to the abutment portion 212 on the upper diameter side of the holder 22. Here, the contact portion refers to a portion that is separated from the contact surface by approximately 1 / 8 to 1 / 4 (0.05 mm to 0.15 mm) of the diameter of the holder. It should be noted that there is no problem if the first and second irradiations are performed in reverse order, from the upper contact area to the lower contact area, with the same effect.

[0019] Figure 3 shows two laser irradiations on holder 32. The first laser irradiation positions are positions 331 on the left and right, and the second laser irradiation position is position 332 above the first. The four laser irradiation positions 331, 332 on the outer periphery of holder 32 are approximately equally spaced, and the thickness of the ring-shaped molten zone 34 formed thereby can be said to be approximately the same (Figure 3 3-2)).

[0020] Figure 4 is a side view of the keeper after laser welding. The molten part of the keeper body 41 is larger than the contact surface, and the molten part of the holder at the contact point is smaller than the radius of the holder. The positions for observing each cross section are identified as a-a' and bb', and the position for observing the cross section of the holder near the molten part is identified as c-c'. Figure 5 shows cross sections of the above-mentioned a-a', bb', and cc'. At the abutment surface position of a-a', the size of the fusion zone 511 is larger than the diameter of the holder, and the central portion 510 is the ferrite structure of the keeper body itself. At the position of bb' where the fusion zone is smaller than the radius of the holder, the fusion zone 521 is ring-shaped, and the central portion 520 is made of the austenite structure of the holder itself and is not fused. At c-c', the entire 530 is the austenite structure of the holder.

[0021] With the holder lightly pressed against the side of the keeper body (Fig. 2), two laser welds are performed, allowing the laser to be evenly applied to the outer periphery of the holder at the four weld points, forming a ring-shaped molten zone around the holder's outer periphery. The molten zone around the outer periphery of the abutment area is smaller than the radius of the holder, making it easier to bend and ensuring sufficient bending strength. Furthermore, there is no molten zone in the center where the keeper is abutting, which limits the amount of welding heat and prevents the coarsening of the ferrite phase crystal grains in the keeper body and the expansion of the heat-affected zone, which is favorable from the perspective of bending strength. [Example]

[0022] The keeper body is made of 17Cr-1Mo ferritic stainless steel, and the holder is made of 18Cr-8Ni austenitic stainless steel. The keeper body is 4 mm in diameter and 0.8 mm thick, and the holder is 0.4 mm in diameter and 10 mm in length. It is abutted against the main side of the keeper body with a pressing force of 0.1 kgf. Next, laser welding was performed by irradiating a laser while spraying Ar gas. The first laser welding was performed simultaneously from both sides of the contact area on the lower diameter of the holder, and the second laser welding was performed simultaneously from both sides of the contact area on the upper diameter of the holder, melting the holder and filling the gap between the contact surface between the keeper body and the holder with molten liquid, and forming a molten zone around the outer periphery of the holder at the contact surface, joining them. The molten zone at the contact area formed a molten zone smaller than the radius of the holder.

[0023] FIG. 6 shows a perspective view and a cross-sectional view taken along line dd' of the keeper 6 thus produced. The size of the contact portion is smaller than the diameter of the holder, and the fusion zone 600 spreads from the contact portion to the contact surface, forming a fusion zone on the outer periphery of the holder that the keeper body contacts, making it larger than the diameter. The fusion zone 600 is an 18Cr-8Ni austenite alloy, and the keeper body is a mixed alloy of 17Cr-1Mo ferrite, resulting in a two-phase structure of austenite and ferrite. A heat-affected zone 602A extends into the austenite phase of the holder, but is not embrittled. A heat-affected zone 602F forms in the ferrite phase of the keeper body, but it is very small and grain coarsening is suppressed.

[0024] The 10 welded products that were produced had sufficient welding strength, and the welded part between the keeper body and the holder did not break even after five bending tests. [Industrial Applicability]

[0025] The present invention makes it possible to stably bend the holder when fixing the keeper of a denture attachment to a root plate, and is expected to be used in a wide range of fields in dentistry. [Explanation of symbols]

[0026] 1, 2, 3, 4, 5, 6: Keeper 11, 21, 31, 41, 51, 61: Goalkeeper body 12, 22, 32, 42, 52, 62: Holder LS1, LS2, LS11, LS12: Laser welding (laser irradiation) 211: Contact surface (butting surface) 212: Contact area 331, 332: Laser irradiation position 34: Welding section 510: Ferrite structure of the keeper body 511: Welding section 520: Austenite structure of holder (unmelted) 521: Welding section 600: Welding section 601F: Heat-affected zone of ferrite structure 601A: Heat-affected zone of austenitic structure 612: Contact state between the keeper body and the holder (unmelted) 7: Casting of root plate 701:Keeper body 702: Holder 703: root plate 8: Goalkeeper 801:Keeper body 802: Holder 805:Joint 9: Goalkeeper 901:Keeper body 902: Holder 905: Joint 10: Goalkeeper 1001:Keeper body 1002: Holder 1011: Welding section 1012: Heat-affected zone

Claims

1. One end of the keeper body of the keeper that constitutes the denture attachment is integral with the side of the keeper body. A keeper for a denture attachment comprising a holder fixed to the denture attachment, The keeper body is made of ferritic magnetic stainless steel, and the holder is made of austenitic Made of stainless steel, The keeper body and the holder are in contact with each other at the side surface of the keeper body, and the contact surface is A denture attachment keeper characterized in that its central part is in contact with the two, there is no change in the structure, and its outer periphery forms a joint consisting of a fused part, and the fused part is smaller than the radius of the holder.

2. The keeper body of the keeper constituting the denture attachment and one end of the keeper body are aligned with the side of the keeper body. A method for manufacturing a keeper for a denture attachment comprising a holder to be physically fixed to the denture attachment, abutting the holder toward the main side of the keeper body; In the first laser welding, laser irradiation is performed simultaneously from both sides on the contact portion on the lower diameter side of the holder, Next, the second laser welding is performed by simultaneously irradiating the abutting portion on the upper side of the diameter of the holder from both sides. A method for manufacturing a keeper for a denture attachment, characterized in that a fused portion having a smaller radius than the holder is formed by melt-joining the outer periphery of the contact surface between the holder and the keeper body.

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