TWI611898B - Forming mold for metal powder injection molding - Google Patents

Abstract

The metal powder injection molding die of the present invention comprises: a plurality of gates for introducing a metal powder injection molding material into a cavity; a main channel, an autonomous runner connected to a flow path branch point; and a plurality of gates The auxiliary flow path is connected to each gate from the flow path branch point; and the plurality of auxiliary flow paths are set as the first auxiliary flow path at an angle which is an obtuse angle with the main flow path, and the main flow path is When the angle is a second sub-flow path, the length of the first sub-flow path is shorter than the length of the second sub-flow path, and the second sub-flow path is curved in the middle.

Description

Forming mold for metal powder injection molding

The present invention relates to a molding die for metal powder injection molding.

In recent years, as a method of forming a metal sintered body having a complicated shape, Metal Injection Molding (MIM) has been popularized. The metal powder injection molding method is produced by molding a kneaded material of a metal powder and an organic binder into a cavity of a molding die, and degreasing and calcining the obtained molded body to produce a desired metal sintered body. The method. According to this method, since the metal sintered body having a shape close to the final shape can be produced, the secondary processing can be omitted or the amount of processing can be reduced, thereby simplifying the manufacturing steps and reducing the manufacturing cost.

The forming die used in the injection molding method generally includes a cavity, and a molding material is supplied to the gate, the runner, and the runner of the cavity. The molding material supplied from the nozzle of the molding machine is sequentially filled in the cavity through the runner, the flow path, and the gate. As a result, a molded body in which the shape of the cavity is transferred is obtained.

Further, depending on the shape of the cavity, a multi-gate type molding die having a plurality of gates with respect to one cavity is used. In this case, the molding material is supplied from a plurality of gates. However, in order to improve the filling property of the molding material, it is important to start the supply of the molding material substantially simultaneously from the gates.

Therefore, an equal-length flow path in which the lengths of the flow paths up to the gates are equal is used (for example, refer to Patent Document 1). In the isometric flow path, the flow path is branched into two branch points by repeating the arrangement, and the flow path lengths up to the gates are designed to be equal. Therefore, as long as If the flow rates of the forming materials are equal, it is in principle considered that the forming materials reach the gates at substantially the same time.

However, in the case of a multi-cavity forming die, the number of branches of the isometric flow path becomes large. Further, when three or more gates are provided for one cavity, the number of branches becomes larger. As a result, the flow resistance of the molding material in the flow path becomes large, resulting in a decrease in the filling property.

Therefore, an object of the present invention is to reduce the number of branches as much as possible, and to equalize the arrival time of the molding material to each gate, thereby improving the filling property.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2007-50554

It is an object of the present invention to provide a metal powder injection molding die which can efficiently produce a high-quality molded article even when it has a high filling property with respect to a cavity having a complicated shape.

The above object is achieved by the present invention described below.

The metal powder injection molding die of the present invention is characterized by comprising: a plurality of gates for introducing a metal powder injection molding material into a cavity; a main channel, which is connected from a runner to a flow path branch point; a plurality of secondary flow passages respectively connected to the secondary runners connected to the gates from the flow path branch points; and the angles formed by the plurality of secondary flow passages and the main flow passages are respectively right angles or obtuse angles, In the plurality of auxiliary flow passages, the first sub-flow passage is set to be an obtuse angle with respect to an angle perpendicular to the surface of the runner and the main passage, and the main passage is When the angle formed is a second sub-flow path, the length of the first sub-flow path is shorter than the length of the second sub-flow path, and the second sub-flow path is bent in the middle view in the plan view. .

Thereby, the time lag when the molding material is supplied to the cavity from the plurality of gates can be shortened, so that it is possible to efficiently produce a high-quality molded body even if it exhibits high filling property with respect to a cavity having a complicated shape. The metal powder is injection molded into a molding die.

In the molding die for metal powder injection molding of the present invention, it is preferable that the number of the first sub-flow paths is one or more and three or less for each of the flow path branch points, and the second sub-flow path The number of articles is one or two.

Thereby, a metal powder injection molding die which can efficiently produce a high-quality molded body can be obtained regardless of the number of gates.

In the metal mold for injection molding of the present invention, it is preferable that the first sub-flow path extends linearly in plan view.

Thereby, the molding material flowing from the autonomous flow path is filled into the first sub-flow path in a shorter time. As a result, the time until the molding material is filled in the first sub-flow path can be further shortened, and the time lag before the supply of the molding material from the plurality of gates can be further shortened.

In the molding die for metal powder injection molding of the present invention, it is preferable that the arrangement of the plurality of sub-flow passages is in line symmetry with respect to the main flow path.

Thereby, the molding material flowing through the main flow path is equally distributed to the plurality of second sub-flow paths. As a result, the time lag before the molding material is filled in the plurality of second sub-flow passages is surely shortened, and the time lag before the supply of the molding material from the plurality of gates can be further shortened.

Preferably, the metal powder injection molding die of the present invention further includes a runner branch point for branching the runner into a plurality of the main flow channels; and the arrangement of the plurality of main channels and the main flow channels The arrangement of the plurality of branches of the sub-flow passages satisfies the point symmetry relationship with respect to the sprue branch points.

Thereby, the forming materials flowing through the runner are equally distributed among the plurality of mainstreams Road. As a result, unevenness in packing density and filling time of the molding material filled in each cavity is suppressed, and a molded body having a small individual difference can be efficiently produced.

1‧‧‧forming mould

2‧‧‧Flow path

10‧‧‧ cavity

11‧‧‧Upper side panel

12‧‧‧Intermediate board

13‧‧‧ Lower side panel

21‧‧‧main runner

22‧‧‧ flow path

23‧‧‧ gate

24‧‧‧Sub runner

215‧‧ ‧ sprue branch point

221‧‧‧mainstream

222‧‧ ‧ secondary runner

225‧‧‧Flower branch point

231‧‧‧ gate

232‧‧‧gate

2221‧‧‧1st secondary flow channel

2222‧‧‧2nd secondary runner

P‧‧‧分模面

Fig. 1 is a longitudinal cross-sectional view showing a mold clamping state of a first embodiment of a metal powder injection molding die of the present invention.

Fig. 2 is a plan view schematically showing a flow path for forming a molding material formed in the metal powder injection molding die shown in Fig. 1 .

Fig. 3 is a perspective view schematically showing the flow path shown in Fig. 2.

Fig. 4 is a plan view schematically showing a part of a flow path for forming a molding material formed in a second embodiment of the metal powder injection molding mold of the present invention.

Fig. 5 is a plan view schematically showing another configuration example of the flow path shown in Fig. 4.

Fig. 6 is a plan view schematically showing a flow path for forming a molding material formed in a molding die used in Comparative Example 1.

Hereinafter, the metal powder injection molding die of the present invention will be described in detail based on the preferred embodiment shown in the drawings.

<First embodiment>

First, a first embodiment of a molding die for metal powder injection molding of the present invention will be described.

1 is a longitudinal cross-sectional view showing a mold clamping state of a first embodiment of a metal powder injection molding die of the present invention, and FIG. 2 is a view schematically showing formation of a metal powder injection molding die formed in FIG. A plan view of a flow path for material flow, and Fig. 3 is a perspective view schematically showing a flow path shown in Fig. 2.

The metal powder injection molding die (hereinafter simply referred to as "forming die") 1 shown in Fig. 1 includes an upper side plate 11, an intermediate plate 12, and a lower side plate 13 which are mold-openable and mold-molded, and the intermediate plate 12 and the lower plate. The side plates 13 form a parting plane P between them. Forming a mold for forming on the parting surface P Cavity 10.

Further, a flow path 2 for flowing a molding material into the cavity 10 is formed in the upper side plate 11 and the intermediate plate 12. The flow path 2 includes a main runner 21 located on the most upstream side from the cavity 10, a flow path 22 located on the downstream side of the main runner 21, and a gate 23 located at a connection portion between the flow path 2 and the cavity 10. Further, as shown in FIG. 2, the flow path 22 is divided into a main flow path 221 which is a portion on the upstream side thereof, and a sub-flow path 222 which is located on the downstream side of the main flow path 221. The molding material supplied from the injection molding machine is sequentially filled in the cavity 10 through the main runner 21, the flow path 22, and the gate 23. Thereby, the molding material is shaped into the shape of the cavity 10, whereby a molded body of an arbitrary shape can be obtained.

Further, the molding die 1 shown in Fig. 1 is a so-called multi-gate molding die, and a plurality of gates 23 are provided for one cavity 10. Furthermore, the forming die 1 may be a so-called multi-cavity having a plurality of cavities 10 as shown in FIGS. 1 to 3, or may be a single cavity. In the case of a multi-cavity gate forming mold as shown in FIGS. 1 to 3, a plurality of gates 23 are provided for each of the cavities 10, respectively.

Hereinafter, the flow path 2 will be described in detail.

In the flow path 2 shown in Figs. 2 and 3, the main runner 21 is branched into four main flow paths 221 at its end. This branch point is referred to as a sprue branch point 215. The four main flow paths 221 are configured to extend radially from the runner branch point 215, that is, the parting plane P which is orthogonal to the main runner 21.

Further, each of the main flow paths 221 is branched into three sub-flow paths 222 at their ends. The branch point is referred to as a flow path branch point 225. The three auxiliary flow paths 222 are configured to extend radially from the flow path branch point 225 in a plan view (hereinafter simply referred to as "plan view") with respect to the parting surface P.

Here, one of the three auxiliary flow paths 222 is disposed so as to extend the main flow path 221 beyond the flow path branch point 225, and the two lines are at right angles to the main flow path 221 from the flow path branch point 225 in plan view. The direction is extended. One of the former secondary flow passages 222 is referred to as a first secondary flow passage 2221, and the latter two secondary flow passages 222 are referred to as a second secondary flow passage 2222, respectively. The first sub-flow passage 2221 and the second sub-flow passage 2222 are connected to the gate 23 via the sub-passage 24, and the gates 23 communicate with the same cavity 10. Therefore, the forming materials are respectively supplied from the three gates 23 It is fed and filled in the cavity 10 in a short time. Further, the gate 23 connected to the end of the first auxiliary flow path 2221 is referred to as a gate 231, and the gate 23 connected to the end of each of the second auxiliary flow paths 2222 is referred to as a gate 232, respectively. Further, the sub-gates 24 extend parallel to the main runner 21 as shown in FIG. 3, and are connected between the ends of the respective sub-flow passages 222 and the gates 23.

The first sub-flow passages 2221 of the three auxiliary flow passages 222 extend linearly in a plan view to the gate 231. Further, in the case of FIG. 2, the first sub-flow path 2221 and the main flow path 221 are disposed on the same straight line, and the angle θ1 between the first sub-flow path 2221 and the main flow path 221 (hereinafter also referred to as "branch angle") ) is 180°. Furthermore, the angle θ1 is an angle formed by the axis of the first sub-flow path 2221 and the axis of the main flow path 221 in plan view. The angle θ1 may be an obtuse angle, and specifically may be more than 95° and less than 180°. Further, the angle θ1 is preferably 100° or more and 180° or less, more preferably 110° or more and 180° or less, and still more preferably 120° or more and 180° or less.

Further, the length (extension) of the first sub-flow path 2221 is set to be shorter than the second sub-flow path 2222. Further, the length of each of the sub-flow passages 222 is a length in a plan view from the flow path branch point 225 to the connection point between each of the sub-flow paths 222 and the sub-gates 24.

On the other hand, the two second sub-flow paths 2222 are formed at right angles to the angle θ2 (hereinafter also referred to as "branch angle") of the main flow path 221 in plan view as described above, and extend in directions opposite to each other. Further, the angle θ2 is an angle formed by the axis of each of the second sub-flow passages 2222 in plan view and the axis of the main flow path 221, and is a right angle means that the angle θ2 is 88° or more and 95° or less.

By specifying the branch angle and length of the runner branch point 225 for the secondary runner 222 as described above, the molding material can be supplied from the three gates 23 substantially simultaneously in the forming die 1. Thereby, the molding material is filled in the cavity 10 in a short time, and the temperature change of the molding material or the change in the properties of the time-dependent property can be suppressed. As a result, generation of weld marks at positions where the molding materials supplied from the respective gates 23 meet each other is suppressed, and uniformization of the packing density is achieved. In this way, a high-quality molded body which is homogeneous and has high shape reproducibility is obtained.

This effect can be considered to be due to the following reasons. Pass through the main runner 21, runner The molding material of the branch point 215 and the main flow path 221 is branched into three directions at the flow path branch point 225. At this time, since the molding material is intended to continue to flow in the extending direction of the main flow path 221, it is preferentially flowed into the first sub-flow path 2221 in which the angle θ1 of the three main flow paths 221 is an obtuse angle. As a result, the inside of the first sub-flow path 2221 is filled with the molding material in a very short time.

On the other hand, when the first sub-flow path 2221 is filled with the molding material, the molding material that has no place to go naturally flows in the second sub-flow path 2222 which is a right angle with respect to the angle θ2 of the main flow path 221. As a result, the molding material is also filled in the two second sub-flow passages 2222 in a short time. When the first auxiliary flow path 2221 and the second auxiliary flow path 2222 are filled with a molding material, the molding material is supplied from the respective gates 23 to the cavity 10.

In the series of operations, the time until the molding material is filled in the first auxiliary flow path 2221 to the time when the molding material is filled in the second auxiliary flow path 2222 is extremely short. This is because the length (extension) of the first sub-flow path 2221 is set to be shorter than that of the second sub-flow path 2222, so that the molding material can be filled in the first sub-flow path 2221 in a very short time, and then quickly filled. The second auxiliary flow path 2222 flows the molding material in a manner.

In other words, in the present invention, the flow path length and the branch angle of the flow path are set such that the first sub-flow path 2221 is filled with the molding material in a short time, so that the first sub-flow path 2221 can be filled. The molding material having no material to be removed is turned to the second sub-flow path 2222 side in a short time, and as a result, the time lag before the molding materials are supplied from the three gates 23 can be shortened.

Further, in the previous isometric flow path, the two auxiliary flow path autonomous flow paths are branched at equal branch angles at the flow path branching point, so that the molding material can start flowing substantially simultaneously with respect to each of the auxiliary flow paths. In this respect, the isometric flow path is useful, but in the case of a multi-gate forming die, in order to provide a plurality of gates, it is necessary to branch the main flow path into a plurality of secondary flow paths, so the number of flow path branch points It has become very much. Therefore, there is a problem that the flow resistance of the flow path increases together with the number of flow path branch points, and the time until the supply of the molding material starts from each gate becomes long.

On the other hand, in the molding die 1 shown in Fig. 2, the main flow path 221 can be branched into the three sub-flow paths 222 at the flow path branching point 225, so that the number of flow path branch points can be reduced. As a result, the time until the molding material reaches the gate 23 can be shortened, and generation of melt marks, poor filling, and the like can be suppressed.

Further, the two second sub-flow passages 2222 are bent in the middle in a plan view. By bending the second auxiliary flow path 2222 in this manner, an increase in the flow resistance of the second auxiliary flow path 2222 can be suppressed, and the degree of freedom in arrangement of the gate 23 can be improved. In other words, when the length of the first sub-flow path 2221 is set shorter than that of the second sub-flow path 2222, the gate 231 located at the end of the first sub-flow path 2221 in plan view and the second sub-flow are located. The longest separation distance that can be obtained by the gate 232 at the end of the track 2222 is also shortened, so that the degree of freedom in the arrangement of the gate 23 is restricted, but by lengthening the second auxiliary flow path 2222, the longest length can be obtained. Separating the distance and suppressing the increase in flow resistance as compared with the case of bending without bending. As a result, the degree of freedom in the arrangement of the gates 23 is improved.

Further, by setting the angle θ2 formed by the second sub-flow path 2222 and the main flow path 221 to a right angle, it is possible to suppress an increase in the flow resistance of the flow path branching point 225, and it is possible to obtain a longer gate 231 and a pouring. The longest separation distance that port 232 can obtain. Further, when the angle θ2 is smaller than the right angle, the flow direction of the molding material flowing through the main flow path 221 is forcibly changed largely in the flow direction, so that the flow resistance of the flow path branch point 225 becomes When the flow rate is lowered, the time until the molding material is filled in the second sub-flow path 2222 becomes long. On the other hand, when the angle θ2 is larger than the right angle, the significant increase in the flow resistance of the flow path branch point 225 is suppressed, but it is difficult to ensure the separation distance between the gate 231 and the gate 232, and the degree of freedom in the arrangement of the gate 23 is changed. small.

In addition, the behavior of the above-mentioned molding material is such that the metal powder is contained in the molding material, that is, the molding material for injection molding of the metal powder, and the above-described action and effect are more reliably exhibited when the molding material is molded. The reason for this is that the molding material containing the metal powder has a large specific gravity, so that the kinetic energy during the flow is large, and it is difficult to rapidly change the flow direction. another On the one hand, since the kinetic energy of the molding material is large, for example, the flow path branching point 225 shown in FIG. 2 naturally naturally produces the following behavior even if it is not particularly controlled, that is, the molding material preferentially flows into the first auxiliary flow path first. In 2221, after the first auxiliary flow path 2221 is filled with the molding material, the molding material flows into the second auxiliary flow path 2222. Therefore, the molding die of the present invention can sufficiently exert its function only in the case of using a molding material containing a metal powder.

On the other hand, the first sub-flow path 2221 shown in FIG. 2 extends linearly in plan view. Thereby, the molding material flowing from the autonomous flow path 221 is filled in the first sub-flow path 2221 in a shorter time. As a result, the time until the molding material is filled in the first sub-flow path 2221 can be further shortened, and the time lag before the supply of the molding material from the three gates 23 can be further shortened.

Further, the first sub-flow path 2221 may be curved in a plan view. Moreover, the main channel 221 can also be bent in a plan view.

Further, the arrangement of the two second sub-flow paths 2222 satisfies the line symmetry relationship with respect to the main flow path 221. With this arrangement, the molding materials flowing through the main flow path 221 are equally distributed to the two second sub-flow paths 2222. As a result, the time lag before the molding material is filled into the two second sub-flow passages 2222 is surely shortened, and the time lag before the supply of the molding material from the three gates 23 can be further shortened.

As described above, in the present invention, the first sub-flow path 2221 having an obtuse angle with respect to the main flow path 221 and the second sub-flow path 2222 having a right angle are included, and the length of the first sub-flow path 2221 is included. The length is shorter than the length of the second sub-flow passage 2222, and the second sub-flow passage 2222 is bent in the middle, whereby the time lag before the supply of the molding material from the gate 23 connected to each of the sub-flow passages 222 can be sufficiently shortened. . As a result, the molding material can be uniformly supplied to the cavity 10 from the plurality of gates 23 and filled in a short time. Therefore, even if the cavity 10 has a complicated shape, the occurrence of the melt marks, the filling failure, and the like can be surely suppressed. A homogeneous and high-density molded body can be efficiently produced.

Further, the number of the first sub-flow paths 2221 may be two or more, but it is preferably one or more. 3 or less. Further, the number of the second sub-flow passages 2222 is also not particularly limited, but is preferably one or two.

Further, in the flow path 2 formed in the molding die 1, as described above, the main runner 21 branches into four main flow paths 221 at the ends thereof, and the respective auxiliary flow paths 222 are provided at the front ends of the main flow paths 221, respectively. The sub-gate 24, each gate 23, and the like are further provided with a cavity 10 at the tip end thereof.

Here, the arrangement of the main flow paths 221 and the respective auxiliary flow paths 222 provided at the front end thereof is as shown in FIG. 2, and the point of the point symmetry is satisfied with respect to the sprue branch point 215. Thereby, the molding material flowing through the main runner 21 is equally distributed to the four main flow paths 221. As a result, unevenness in the filling density and the filling time of the molding material filled in each of the cavities 10 is suppressed, and the molded body having a small individual difference can be efficiently produced.

In addition, the number of the cavity 10 formed in one molding die 1 is not particularly limited, and may be one to three or five or more.

<Second embodiment>

Next, a second embodiment of the molding die for metal powder injection molding of the present invention will be described.

Fig. 4 is a plan view schematically showing a part of a flow path for forming a molding material formed in a second embodiment of the metal powder injection molding mold of the present invention.

In the following, the second embodiment will be described, but the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. In the same manner as in the first embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.

The second embodiment is the same as the first embodiment except that each of the main flow paths 221 is branched into four sub-flow paths 222 at the ends thereof.

Two first sub-flow paths 2221 are disposed in the flow path 2 shown in FIG. The arrangement of the first sub-flow paths 2221 satisfies the line symmetry relationship with respect to the main flow path 221. By this arrangement, the molding materials flowing through the main flow path 221 are equally distributed to the two first sub-flow paths 2221. As a result, the time lag before the molding material is filled in the two first sub-flow paths 2221 is surely shortened.

Fig. 5 is a plan view schematically showing another configuration example of the flow path shown in Fig. 4.

Three first sub-flow paths 2221 are disposed in the flow path 2 shown in FIG. The arrangement of the first sub-flow paths 2221 also satisfies the line symmetry relationship with respect to the main flow path 221. Furthermore, in this case, one of the three first sub-flow paths 2221 is disposed on the extension line of the main flow path 221.

Hereinabove, the present invention has been described based on preferred embodiments, but the present invention is not limited thereto.

For example, in the forming mold, any structure may be added in addition to the above-described structure.

Further, the cavity of the metal powder injection molding die of the present invention may have any shape.

[Examples]

Next, a specific embodiment of the present invention will be described.

1. Manufacturing of formed body 1

(Example 1)

First, SUS316L powder manufactured by the water mist method is prepared. For the SUS316L powder, the average particle diameter was measured by a laser diffraction type particle size distribution measuring apparatus (Microtrac, manufactured by Nikkiso Co., Ltd., HRA9320-X100), and the average particle diameter was 10 μm. . The organic binder is obtained by mixing polypropylene and paraffin in a mass ratio of 9:1. Moreover, the mass ratio of SUS316L powder to organic binder was set to 91:9.

Then, they are mixed and kneaded in a pressure kneader (kneader).

Then, the obtained kneaded product was pulverized by a granulator to obtain granules having an average particle diameter of 5 mm.

Then, using the obtained pellets, molding was carried out in an injection molding machine under the molding conditions of a material temperature of 150 ° C and an injection pressure of 10.8 MPa (110 kgf / cm ² ). Thereby, a molded body is obtained. Further, the shape of the formed body was a disk shape having a diameter of 30 mm × a thickness of 5 mm.

Further, a case where a number of cavities of four cavities are used as a forming die, and a flow path is used as the shape shown in FIG. Furthermore, the shape conditions of the flow path are as follows.

<shape of the flow path>

‧Number of branches of the sprue branch point: 4

‧The number of branches of the runner branch point: 3

‧Number of gates per cavity: 3

‧Number of the first sub-flow passage: 1

‧Number of second secondary runners: 2

‧The branch angle of the first secondary flow channel: 180°

‧Second secondary runner branch angle: 90°

(Example 2)

A molded body was obtained in the same manner as in Example 1 except that the shape of the flow path was changed to the shape shown in the following (the shape shown in FIG. 4), and the number of the gates of each cavity was changed to four. .

<shape of the flow path>

‧The number of branches of the runner branch point: 4

‧The number of the first secondary runner: 2

‧Number of second secondary runners: 2

‧The branch angle of the first sub-flow channel: 135°

‧Second secondary runner branch angle: 90°

(Example 3)

A molded body was obtained in the same manner as in Example 1 except that the shape of the flow path was changed to the shape shown in the following (the shape shown in FIG. 5), and the number of the gates of each cavity was changed to five. .

<shape of the flow path>

‧The number of branches of the runner branch point: 5

‧Number of the first secondary runner: 3

‧Number of second secondary runners: 2

‧The branch angle of the first sub-flow channel: 120° and 180°

‧Second secondary runner branch angle: 90°

(Comparative Example 1)

A molded body was obtained in the same manner as in Example 1 except that the shape of the flow path was changed to the shape shown below. In addition, FIG. 6 is a plan view schematically showing a flow path for forming a molding material formed in a molding die used in Comparative Example 1.

<shape of the flow path>

‧Number of the first sub-flow passage: 1

‧Number of second secondary runners: 2

‧The branch angle of the first secondary flow channel: 180°

‧Second secondary runner branch angle: 60°

(Comparative Example 2)

A molded body was obtained in the same manner as in Example 2 except that the shape of the flow path was changed to the shape shown below.

<shape of the flow path>

‧The number of the first secondary runner: 2

‧Number of second secondary runners: 2

‧The branch angle of the first sub-flow channel: 135°

‧Second secondary runner branch angle: 60°

(Comparative Example 3)

A molded body was obtained in the same manner as in Example 3 except that the shape of the flow path was changed to the shape shown below.

<shape of the flow path>

‧Number of the first secondary runner: 3

‧Number of second secondary runners: 2

‧The branch angle of the first sub-flow channel: 120° and 180°

‧Second secondary runner branch angle: 60°

2. Evaluation of the shaped body

Next, the molded body obtained from each of the examples and the comparative examples was degreased and calcined to obtain a sintered body. Then, the obtained sintered body was subjected to the following evaluation. Further, the degreasing conditions and the calcination conditions are as follows.

<degreasing conditions>

‧ Degreasing temperature: 500 ° C

‧ Defatting time: 1 hour

‧Degreasing environment: nitrogen environment

<calcination conditions>

‧ Calcination temperature: 1300 ° C

‧ Calcination time: 3 hours

‧ calcination environment: argon environment

2.1 Evaluation of Sintering Density

With respect to 100 sintered bodies obtained in each of the examples and the comparative examples, the density was measured by a method according to the Archimedes method (defined by JIS Z 2501). Further, the relative density of the sintered body was calculated from the average value of the measured sintered density and the true density of the metal powder.

As a result, it was confirmed that the sintered body obtained in each of the examples had a higher relative density than the sintered body obtained in each of the comparative examples.

2.2 Appearance evaluation

The appearance of the sintered body obtained from each of the examples and the comparative examples was evaluated based on the following evaluation criteria.

<Appraisal basis for appearance>

◎: The number of sintered bodies which are broken, defective, and deformed is three or less.

○: The number of sintered bodies which are broken, defective, and deformed is 4 or more and 10 or less.

△: The number of sintered bodies which are broken, defective, and deformed is 11 or more and 50 or less.

×: The number of sintered bodies in which fracture, defect, and deformation occurred was 51 or more.

2.3 Evaluation of dimensional accuracy

The outer diameter of each of the sintered bodies obtained in each of the examples and the comparative examples was measured by a micrometer. Then, the average value of the measured values is evaluated based on the following evaluation criteria based on the "normal tolerance of width" defined by JIS B 0411 (common tolerance of the metal sintered product).

<Evaluation criteria for dimensional accuracy>

◎: The grade is a precision grade (the tolerance is ±0.05 mm or less).

○: The grade is intermediate (the tolerance is more than ±0.05 mm and is ±0.1 mm or less).

△: The grade is a normal grade (the tolerance is more than ±0.1 mm and is ±0.2 mm or less).

×: Deviation from the allowable range.

The evaluation results of 2.2 and 2.3 are shown in Table 1.

2.4 Evaluation of sintering uniformity

For the 100 sintered bodies obtained from the respective examples and the comparative examples, the randomly selected ones were selected. The Vickers hardness at 10 points was measured. Then, the distribution width of the ten measured values was calculated, and compared between each of the examples and the comparative examples.

As a result, it was confirmed that the sintered body obtained in each of the examples had a narrower distribution of Vickers hardness than the sintered body obtained in each of the comparative examples, and the average value thereof was high. That is, it was confirmed that the sintered body obtained in each of the examples had higher sintering uniformity than the sintered body obtained in each of the comparative examples.

Claims (7)

A molding die for metal powder injection molding, comprising: a plurality of gates for introducing a metal powder injection molding material into a cavity; a main channel, which is connected to a runner branch point by a runner; and plural a secondary flow passage connected to the secondary runner connected to each of the gates; and the angle formed by the plurality of secondary flow passages and the main flow passage is a right angle or an obtuse angle, respectively In the auxiliary flow passage, the angle formed by the plane perpendicular to the runner and the angle formed by the main passage is a first sub-flow passage, and the angle formed by the main passage is a right angle. When the second sub-flow path is set, the length of the first sub-flow path is shorter than the length of the second sub-flow path, and the second sub-flow path is curved in the middle direction in the plan view. The metal powder injection molding die according to claim 1, wherein the number of the first sub-flow paths is one or more and three or less for each of the flow path branch points, and the number of the second sub-flow paths It is 1 or 2 pieces. The metal powder injection molding die according to claim 1, wherein the first sub-flow path extends linearly in plan view. The metal powder injection molding die according to claim 2, wherein the first sub-flow path extends linearly in plan view. The metal powder injection molding die according to any one of claims 1 to 4, wherein the arrangement of the plurality of sub-flow passages satisfies a line symmetry relationship with respect to the main flow path. The metal powder injection molding die according to any one of claims 1 to 4, further comprising a runner branch point for branching the runner into a plurality of the main flow paths; The arrangement of the plurality of main channels and the arrangement of the plurality of sub-channels branched from the main channels are satisfied with a point symmetry relationship with respect to the sprue branch points. The metal powder injection molding die according to claim 5, further comprising a runner branch point for branching the runner into the plurality of main channels; and arranging the plurality of main channels and branching from the main channels The arrangement of the plurality of sub-flow passages satisfies the point symmetry relationship with respect to the sprue branch point.