JPH1171603A - Production of sintered body with dovetail groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sintered body the inside of which has a shape more expanded than that of the opening part without requiring a mechanical working stage by forming a groove on the surface of a compacted body formed from powder, placing the compacted body on a tray while keeping the opening part of the groove to the down side and executing sintering. SOLUTION: On the surface of a compacted body 3 compacted by using powder, a groove 4 having an opening part 4a and having such a shape that the groove width is approximately equal in the depth direction is formed. The surface of the compacted body is compacted so as to form the cross-section in the groove width direction into a recessed one 5. The opening part 4a of the groove 4 compacted into the compacted body 3 is placed on a tray 6 for sintering or on a setter while keeping the opening part 4a of the groove 4 formed on the compacted body 3 to the down side in such a manner that the groove part wall 4b is made vertical to the face of the tray 6 for sintering or of the setter. The placed compacted body 3 is held at a prescribed temp. for a prescribed time in a sintering furnace and is sintered. At the time of the sintering, the lower part of the compacted body 3 is deformed by the operation of gravity to form such a dovetail groove 2 that the equal groove width is expanded in the depth direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sintered body having a dovetail groove, and more particularly to a method of manufacturing a sintered body having a dovetail groove which forms a dovetail groove during sintering.

[0002]

2. Description of the Related Art As a method of manufacturing a sintered body, a basic press sintering is performed in which powder is mixed and kneaded, filled in a mold, compression molded to form a molded body, and then sintered at a predetermined temperature and atmosphere. The method has been conventionally adopted. In recent years, a metal injection molding (MIM) process in which a kneaded product of a metal fine powder and a binder is formed into a molded body by injection molding, and then degreased and sintered, has been applied to relatively small parts having a complicated shape.

[0003] In particular, recently, for example, orthodontic brackets having the shape shown in Fig. 3 have been manufactured by a metal injection molding (MIM) process. The orthodontic bracket manufactured by MIM is not limited to the shape shown in FIG. 3, but various shapes are prepared. The bracket is adhered to the teeth or the like to be corrected, a wire is passed through a slot of each bracket, and the wire is tensioned between the brackets to apply torque or the like to the teeth to correct the teeth.

[0004]

Not only the orthodontic bracket described above, but also a dovetail groove is often formed on the bonding surface of a part to be bonded and used in order to increase the bonding strength. In particular, the brackets for orthodontics mentioned above include:
Because a large force (torque force etc.) acts during orthodontics,
The bracket must be firmly bonded to the teeth. Therefore, it is required to form a dovetail groove on the bonding surface of these brackets.

[0005] The dovetail groove is usually formed by machining, but machining has good machining accuracy, but has the problem that the machining process is complicated and the cost is high. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a sintered body with a groove, which can advantageously solve the above-mentioned problem and can form a groove in the sintered body without using machining.

[0006]

Means for Solving the Problems The present inventor has conducted intensive studies on a method of forming a groove in a sintered body without using mechanical processing, and as a result, by advantageously utilizing deformation during sintering,
It has been found that a dovetail groove can be easily formed. The present invention has been made based on the above findings.

That is, the present invention relates to a method for producing a sintered body in which powder is formed into a molded body and then sintered, wherein the molded body has an opening on a surface and a groove width in a depth direction. A groove having substantially the same shape is formed, the molded body is placed on a sintering tray with the opening facing downward, and sintered, and the groove is formed as a dovetail groove having a shape whose inside is larger than the opening. A method for producing a sintered body with a dovetail, characterized in that the molded body is preferably a metal injection molded body.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a dovetail groove having a typical shape shown in FIG. 1 is formed in a sintered body. The sintered body of the present invention is kneaded with a powder, molded and formed into a molded body, and then sintered. The powder used in the present invention is preferably made of a metal or an alloy. A lubricant, a binder and the like may be added together with the powder.

As a method for producing a molded article, any of a press method and an injection molding method can be suitably applied, and there is no particular limitation. It goes without saying that any of the press method and the injection molding method can be suitably applied to a generally known method. In the press sintering method, the type of metal powder and the amount thereof are selected so that desired characteristics can be obtained, and these powders are mixed, or a lubricant is further added and kneaded. The obtained mixed powder is filled in a mold and molded with an appropriate compression force to obtain a molded body. These compacts are sintered to produce products.

In the injection molding method, a metal fine powder is selected so that desired characteristics can be obtained, and a kneaded material kneaded with a binder is injected into a mold to form a molded body. After debinding, it is sintered to produce a product. The method of the present invention is schematically shown in FIG. 2 by taking a case where two dovetail grooves are formed in a sintered body as an example. It goes without saying that the method of the present invention is basically independent of the number of dovetail grooves.

In the present invention, the groove 2 is provided on the bonding surface of the sintered body 1.
First, a groove 4 having an opening 4a on the surface and having a substantially equal groove width in the depth direction is formed on the molded body 3 (see FIG. 2A). In the present invention, it is important to appropriately control the shape of the compact in order to advantageously utilize the deformation during sintering.

That is, as the shape of the molded body, the molded body is molded so that the surface of the molded body has a concave cross section 5 in a cross section in a groove width direction (a cross section perpendicular to the longitudinal direction of the groove) (FIG. 2A). In order to form such a shape, it is preferable to select the shape of the concave portion R according to the shape of the finished groove. Next, the compact is placed on a sintering tray or setter with the opening facing downward. At this time, it is essential that the groove wall 4b is placed so as to be perpendicular to the surface of the tray or the setter 6 (FIG. 2B).

The compact placed as described above is held and sintered in a sintering furnace at a predetermined temperature for a predetermined time. At the time of sintering, the lower part of the molded body is deformed by the action of gravity (the concave portion R of the molded body is linearly deformed), and the groove width equal to the depth direction is increased internally. (Figure 2
(C)). The dovetail groove 2 to be formed can be easily formed as a one-way groove, a crossing groove or a groove of any shape.
When crossing dovetail grooves are formed, grooves having equal groove widths may be formed in the molded body by crossing them in the depth direction, and the grooves are formed by deformation during sintering due to the action of gravity.

In the present invention, the conditions, temperature,
No special conditions of time or sintering atmosphere are required. It goes without saying that the optimum generally known conditions according to the material may be selected. In the method of the present invention, when the molded body is obtained by the metal injection molding method, it is relatively easily deformed by the influence of gravity during sintering, so that the formation of the dovetail groove becomes easy.

[0015]

[Embodiment] 17wt% Cr-4wt% Ni is the main component, and Nb + Ta is 0.1%.
SUS 630 steel powder containing 35 wt% was kneaded with a binder and injection molded to obtain a molded body. Then, after sintering through a binder removal process, an orthodontic bracket having a shape shown in FIG. 3 was obtained. This molded product has an opening in the surface corresponding to the surface to be bonded to the teeth, and has a groove having a groove width of 0.5 mm, a groove depth of 0.5 mm and a groove width equal to the depth direction. Articles are formed. The cross section of the surface of the molded product was concave between the grooves or at the ends (R30 to R40).

Then, the compact was placed on a sintering tray with the opening facing downward so that the groove wall was perpendicular to the tray surface (the product was horizontal). The sintering tray on which the compact was placed was placed in a sintering furnace, and heat-treated at 1300 ° C for 3 hours (atmosphere:
N ₂ partial 20Torr) was carried out. As a result, a dovetail groove having an opening groove width: 0.3 mm, a bottom groove width: 0.4 mm, and a depth: 0.4 mm could be formed.

[0017]

According to the present invention, a slotted sintered body can be manufactured economically and inexpensively without the need for a machining step.
It has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing the shape of a dovetail groove.

FIG. 2 is an explanatory view schematically illustrating the procedure of the method of the present invention.

FIG. 3 is an explanatory view showing an example of the shape of an orthodontic bracket.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sintered body 2 Groove 3 Molded body 4 Groove 4a Opening 4b Groove wall 5 Concave section 6 Sintering tray (setter)

Claims (2)

[Claims] 1. A method for producing a sintered body in which powder is formed into a compact and then sintered, wherein the compact has a groove having an opening on a surface and a groove width substantially equal in a depth direction. Formed,
The molded body is placed on a sintering tray with the opening part being on the lower side and sintered, and the groove is formed as a dovetail groove having a shape in which the inside is larger than the opening part. How to make the body. 2. The method for producing a sintered body according to claim 1, wherein the molded body is a metal injection molded body.