Manufacturing method of sintered body

Abstract

To provide a method for manufacturing a sintered compact, which can manufacture the sintered compact by using metal powders different in melting point and sintering temperature without melting the metal powders, and surely maintain gradation even when it is polished or abraded.SOLUTION: This method for manufacturing the sintered compact is for manufacturing a jewel having gradation and comprises: a filling step of filling a sintering mold 14 with gold alloy powder P1, platinum alloy powder P2, and mixed powders M1-M3 containing gold alloy powder P1 and platinum alloy powder P2 by different ratios in a layered manner; and a pressure sintering step of pressurizing and sintering the gold alloy powder P1, the platinum alloy powder P2, and the mixed powders M1-M3 layered to fill the mold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a sintered body for use in jewelry having gradation. [Background technology]

[0002] Jewelry such as rings and necklaces require excellent design including color. Among them, jewelry with a gradation composed of two or more colors is popular because of its visual design. Various methods are known for imparting a gradation to jewelry, such as a chemical reaction method, a surface coating method, and a casting method (for example, Patent Document 1). The manufacturing method of a decorative part disclosed in Patent Document 1 adjusts the oxygen partial pressure and supply rate in an electric furnace for a decorative part having an oxide layer containing cuprous oxide on its surface, heats a part precursor whose surface is made of copper to a predetermined temperature and then cools it to form an oxide layer, and changes the color shade of the oxide layer in a gradational manner from one end side to the other end side of the oxide layer. In addition to this, a method of treating the surface of a jewelry with a gas burner and a method of painting the surface of a jewelry are also known.

[0003] On the other hand, Patent Document 2 discloses a method for producing a monochrome composite material by mixing raw metal particle materials and spark plasma sintering them in a vacuum atmosphere, while Patent Document 3 discloses a method for producing a monochrome precious metal composite material with an aesthetic color pattern by combining platinum and a material in which gold and iron have been added, and heating the material at a temperature of 200°C to 450°C in an oxygen-containing atmosphere to change the color tone of the gold-iron alloy and reveal a platinum color pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-285515 A [Patent Document 2] JP 2007-92119 A [Patent Document 3] Japanese Patent Application Publication No. 3-202454 Summary of the Invention [Problem to be solved by the invention]

[0005] When a gradation is imparted by forming an oxide layer using a gas burner, the reproducibility of the color tone of the oxide layer is poor, and it is difficult to control the color tone to a uniform color tone. Furthermore, the above-mentioned jewelry produced by the method of treating the surface with a gas burner, the method of painting the surface of the jewelry, and the method of using an electric furnace can impart a gradation or a desired color tone to the surface layer of the jewelry, but the gradation is not imparted to the part other than the surface layer. Therefore, when the jewelry is polished in post-treatment or the surface is worn down severely during use, the surface layer that constitutes the gradation may peel off.

[0006] Therefore, an object of the present invention is to provide a method for producing a sintered body by using metal powders having different melting points and sintering temperatures, without melting the metal powder, and by which the gradation is reliably maintained even when the sintered body is polished or worn. [Means for solving the problem]

[0007] The method for producing a sintered body according to the present invention is for producing a sintered body to be used for jewelry having a gradation, and is characterized by including a filling step in which mixed powders having different blending ratios of the first metal powder and the second metal powder are filled in layers into a mold using at least a first metal powder and a second metal powder, and a pressure sintering step in which the mixed powders filled in layers are sintered while being pressurized.

[0008] The method for producing a sintered body according to the present invention is characterized in that the mold is cylindrical or columnar, and mixed powders having different compounding ratios are filled from the bottom to the top of the mold or in the circumferential direction of the mold.

[0009] The method for producing a sintered body according to the present invention is characterized in that the first metal powder and the second metal powder are composed of any of gold, silver, platinum, palladium, copper, zinc, nickel, indium, gallium, aluminum, ruthenium, or an alloy containing at least one selected from the group consisting of these.

[0010] The method for producing a sintered body according to the present invention is characterized in that the particle size of the first metal powder and the second metal powder is 5 μm to 200 μm.

[0011] The method for producing a sintered body according to the present invention is characterized in that the pressure sintering step is carried out by a spark plasma sintering method, the pressure for pressing the mixed powder is 5 MPa to 100 MPa, and the pressure for pressing the mixed powder is increased stepwise.

[0012] The method for producing a sintered body according to the present invention is characterized in that in the pressure sintering step, a temperature gradient is generated in a mold and the mixed powder is sintered. Effect of the Invention

[0013] The method for producing a sintered body according to the present invention uses at least a first metal powder and a second metal powder, fills a mold with layers of mixed powders having different compounding ratios of the first metal powder and the second metal powder, and sinters these mixed powders while applying pressure. This production method produces a sintered body having a gradation, and can produce a jewelry having a gradation. Since the jewelry has a gradation in parts other than the surface layer, the gradation can be maintained even if the jewelry is polished or worn in post-processing.

[0014] Furthermore, in the method for producing a sintered body according to the present invention, the pressure sintering step utilizes a spark plasma sintering method and is performed under predetermined conditions, thereby making it possible to produce a dense sintered body having excellent mechanical properties and a microcrystalline structure with suppressed grain growth in a short time.Furthermore, it is possible to produce a sintered body with high reproducibility of gradation.

[0015] The method for producing a sintered body according to the present invention can produce a sintered body by sintering different metal powder raw materials without melting metal powder, and can produce jewelry (particularly rings) with excellent aesthetic appeal in terms of gradation, color, texture, design, pattern, shape, etc., in a short time using energy- and resource-saving techniques. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a spark plasma sintering apparatus used in a method for producing a sintered body according to a first embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams showing a sintering mold used in a method for producing a sintered body according to a first embodiment of the present invention, in which (a) shows the configuration of the sintering mold, and (b) shows the space into which the mixed powder is filled. [Diagram 3] FIG. 2 is a diagram for explaining a filling step in the method for producing a sintered body according to the first embodiment of the present invention. [Figure 4] FIG. 2 is a partial enlarged view of the sintering mold after a filling step in the method for producing a sintered body according to the first embodiment of the present invention. [Diagram 5] 10A to 10C are diagrams for explaining a filling step in the method for producing a sintered body according to a modified example of the first embodiment of the present invention. [Figure 6] 1A to 1C are diagrams illustrating an example of a jewelry item manufactured by the method for manufacturing a sintered body according to the first embodiment of the present invention. [Figure 7] FIG. 4 is a diagram for explaining a method for producing a sintered body according to a second embodiment of the present invention. [Figure 8] FIG. 4 is a diagram for explaining a method for producing a sintered body according to a third embodiment of the present invention. [Figure 9] FIG. 4 is a diagram for explaining a method for producing a sintered body according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] [First embodiment] The method for producing a sintered body according to this embodiment is used to produce jewelry such as a ring, necklace, and earrings having gradation. In this embodiment, a method for producing a ring having gradation is taken as an example and will be described with reference to Fig. 1 to Fig. 4. Note that Fig. 2 is used as a reference, and the vertical direction is defined as X and the horizontal direction is defined as Y.

[0018] The method for producing a sintered body of this embodiment includes a mixed powder preparation process for preparing a mixed powder using at least a first metal powder and a second metal powder, a filling process for filling a formwork, a pressure sintering process for sintering the mixed powder while applying pressure, and a post-processing process. The first metal powder and the second metal powder are composed of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), zinc (Zn), nickel (Ni), indium (In), gallium (Ga), aluminum (Al), ruthenium (Ru), or an alloy containing at least one selected from these groups. In this embodiment, a gold alloy is used for the first metal powder, and a platinum alloy is used for the second metal powder. In addition, the particle size of the first metal powder and the second metal powder is preferably 5 μm to 200 μm.

[0019] The pressure sintering process is carried out using a spark plasma sintering apparatus 10 shown in Fig. 1. This spark plasma sintering apparatus 10 includes a vacuum chamber 11, an upper electrode 12 arranged above the vacuum chamber 11, a lower electrode 13 arranged below the vacuum chamber 11, a sintering formwork 14 installed between the upper electrode 12 and the lower electrode 13, and a control unit 15 connected to the upper electrode 12 and the lower electrode 13. The control unit 15 includes a pressure control mechanism that operates the upper electrode 12 and the lower electrode 13 up and down to apply pressure, a pulse power supply unit mechanism that applies a pulse current between the upper electrode 12 and the lower electrode 13, and the like.

[0020] As shown in Fig. 2(a), the sintering mold 14 has a cylindrical lower punch 20 with a spacer 24 attached to its lower end, a rod-shaped core 21 attached to the lower punch 20, a cylindrical die 22 provided so as to surround the periphery of the core 21, and a cylindrical upper punch 23 with a spacer 26 attached to its upper end (Fig. 3(b)). The lower punch 20, upper punch 23, core 21 and die 22 are made of graphite. The die 22 is attached to the lower punch 20 so that the distance a between the upper end of the die 22 and the lower end of the spacer 26 is longer than the distance b between the lower end of the die 22 and the upper end of the spacer 24 (FIG. 3(b)). A temperature gradient is generated in the sintering mold 14 by changing the area of ​​the exposed part of the upper punch 23 and the exposed part of the lower punch 20 (the amount of contact between the die 22 and each punch 23, 20) and changing the electrical resistance.

[0021] As shown in Fig. 2(b), a ring-shaped space S is formed between the core 21 and the die 22. A mixed powder of metals is filled into this space S. A thermocouple is provided inside the die 22, and the temperature at which the mixed powder is sintered is adjusted based on the temperature of the thermocouple. Note that the lower punch 20, upper punch 23, core 21, and die 22 that constitute the sintering mold 14 are not limited to graphite.

[0022] [Mixed powder preparation process] In the mixed powder preparation process, mixed powder M3 is prepared from three mixed powders M1 with different mixing ratios of gold alloy (18K: 75% gold, silver, copper, palladium) and platinum alloy (95% platinum, palladium, ruthenium). Specifically, mixed powder M1 (mixing ratio 8:2), mixed powder M2 (mixing ratio 5:5), and mixed powder M3 (mixing ratio 2:8) are prepared. Mixed powders M1 to M3 are stirred / mixed to obtain the desired mixture of two types of metal powder. The above mixing ratio is calculated based on the volume ratio of each metal powder. Also, M (number) indicates that it is a mixed powder of different metals, and does not indicate a mixed powder with a specific mixing ratio.

[0023] [Filling process] In the filling step, the gold alloy powder P1, platinum alloy powder P2, and mixed powders M1 to M3 prepared in the mixed powder preparation step are filled into the sintering mold 14. To facilitate release, carbon paper (not shown) is provided on the upper surface of the lower punch 20, the inner part of the die 22, the outer surface of the core 21, and the lower surface of the upper punch 23, which constitute the sintering mold 14. Note that a release agent may be applied instead of providing carbon paper.

[0024] In the filling step, as shown in Fig. 3(a), the gold alloy powder P1 is filled into the space S of the sintering mold 14, and then the mixed powder M1 is filled on top of the gold alloy powder P1. Similarly, the mixed powder M2, mixed powder M3, and platinum alloy powder P2 are filled, and then the upper punch 23 is attached. Then, as shown in Fig. 3(b), the sintering mold 14 is placed between the upper and lower water-cooled plates 28 via the spacer 25 and spacer 27. Inside the water-cooled plate 28, a water flow channel 29 is provided.

[0025] In this way, the gold alloy powder P1, the platinum alloy powder P2, and the mixed powders M1 to M3 are filled in layers in the height direction of the sintering mold 14. The gold alloy powder P1 and the platinum alloy powder P2 are filled so that the layer thickness is thicker than the layer thickness of the other mixed powders M1 to M3, as shown in Fig. 4. In other words, the gold alloy powder P1 and the platinum alloy powder P2 are filled in greater amounts than the mixed powders M1 to M3.

[0026] [Pressure sintering process] The pressure sintering process is performed by the spark plasma sintering method (SPS). The sintering mold 14 filled with the gold alloy powder P1, the platinum alloy powder P2, and the mixed powder M1 to M3 is placed between the upper electrode 12 and the lower electrode 13 in the spark plasma sintering device 10. The inside of the vacuum chamber 11 is evacuated, and the spark plasma sintering is performed. The pressure for pressing the mixed powder filled in layers is preferably 5 MPa to 80 MPa, and the temperature for sintering the mixed powder filled in layers (SPS sintering temperature) is preferably 400°C to 1500°C. Here, the SPS sintering temperature does not mean the temperature inside the mixed powder, but the temperature measured at the position (temperature measurement point) of a thermocouple attached to the die 22 or the like.

[0027] The pressure sintering process of this embodiment is carried out in the following multiple steps by adjusting the conditions of the heating rate, pressure, and SPS sintering temperature: In steps 1 to 5, the heating rate is slowed down and the pressure is increased stepwise. Step 1: Heating rate 40℃ / min, pressure 10MPa, SPS sintering temperature 500℃ Step 2: Heating rate 20℃ / min, pressure 10MPa, SPS sintering temperature 600℃ Step 3: Heating rate 20℃ / min, pressure 40MPa, SPS sintering temperature 700℃ Step 4: Heating rate 10℃ / min, pressure 50MPa, SPS sintering temperature 800℃ Step 5: Heating rate 5℃ / min, pressure 60MPa, SPS sintering temperature 815℃

[0028] [Post-processing process] After the pressure sintering process, a post-processing process is carried out. In the post-processing process, the ring-shaped sintered body is removed from the sintering mold 14, and the carbon paper adhering to the sintered body and burrs generated by the pressure sintering are removed. The ring is then machined into the desired shape on a lathe to produce a jewelry piece, a ring.

[0029] An example of the SPS sintering temperature, which is one of the sintering conditions, will be explained. At SPS sintering temperatures above the designated level, the metal with a low melting point elutes, making it impossible to obtain a sintered body with gradation.Also, at SPS sintering temperatures below the designated level, the metal is not densified sufficiently, residual pores are generated, and it is not possible to obtain the desired sintered body.

[0030] Next, the effects of the method for producing a sintered body according to this embodiment will be described.

[0031] In the manufacturing method of the sintered body of this embodiment, a gold alloy and a platinum alloy are used, and the gold alloy powder, the platinum alloy powder, and each mixed powder (M1 to M3) with different compounding ratios of these metal powders are filled in layers in a mold, and the powder filled in layers is sintered while being pressurized. This manufacturing method can reliably manufacture a ring with gradation. And, since this ring has gradation in the parts other than the surface (bulk part), the same gradation is maintained even when polished or worn, and excellent design can be maintained for a long time. In addition, in the spark plasma sintering device 10 used in the manufacturing method of the sintered body of this embodiment, the die 22 is attached so that the distance a is longer than the distance b, and the part where the upper punch 23 and the lower punch 20 are exposed is adjusted, so that a temperature difference is generated above and below the vertical direction X of the sintering mold 14, and mixed powders with different melting points can be sintered. At a temperature of 80% to 85% of the melting point (melting point), the metal powder can be sintered without melting.

[0032] In the manufacturing method of the sintered body of this embodiment, the discharge plasma sintering method is used in the pressure sintering step, so that the desired sintered body can be produced in a relatively short time, and a ring with high reproducibility can be produced. In addition, the discharge plasma sintering apparatus 10 can adjust various conditions such as temperature and pressure, so that the conditions can be easily set appropriately according to the mixed powder of metals to be sintered.

[0033] In addition, the gold alloy used as the first metal in this embodiment is available in different colors, such as pink gold, yellow gold, white gold, and black gold, and rings of different colors can be made by using these powders. Note that metal powders of various colors other than the gold alloy and platinum alloy used in this embodiment can be used, and jewelry with many variations and different colors can be made.

[0034] In the pressure sintering process of the manufacturing method of the sintered body of this embodiment, the pressure applied to the mixed powder packed in layers is increased stepwise in multiple steps. By increasing the pressure stepwise, the gas (O2) adsorbed on the surface of the starting material (metal powder) and the gas generated during the sintering process are pushed out and removed, the generation of residual pores during the densification process is suppressed, and a high-density sintered body can be obtained by sintering.

[0035] The method for producing a sintered body according to the present embodiment can produce a sintered body by sintering different metal powder raw materials (gold alloy, platinum alloy) without melting the mixed powders M1 to M3. This method for producing a sintered body can produce a ring (jewelry) with excellent aesthetics such as gradation, color, texture, design, pattern, and shape in a short time and with low energy consumption.

[0036] As a modification of this embodiment, mixed powders M1 to M8 with different compounding ratios can be filled in layers in the circumferential direction of a sintering mold 14 to produce a jewelry ring, as shown in Fig. 5. A ring produced under such conditions also has gradation in parts other than the surface, and maintains its excellent design for a long time. Although FIG. 5 shows an example in which eight mixed powders M1 to M8 are evenly filled, the number of mixed powders can be changed as appropriate, and the mixed powders may be filled ununiformly in the circumferential direction of the sintering formwork 14.

[0037] In the method for producing a sintered body according to the present embodiment, a ring-shaped sintered body having a gradation was produced, but the shape of the sintering mold 14 can be changed to produce a cylindrical or polygonal sintered body. In addition, the method for producing a sintered body according to the present embodiment can impart a pattern other than the gradation to the sintered body. For example, in the filling step, a jig is used to fill a metal powder or a metal solid at a desired position, and a pressure sintering step is performed, so that patterns 30A, 30B, 31A, and 31B other than the gradation can be imparted to the sintered body 30 and 31 as shown in Figs. 6(a) and 6(b). Furthermore, in the filling step, a solid having a specific shape, such as a heart or a circle, is placed in the mixed powder M1 to the mixed powder M5, and pressure sintering is performed, so that a heart mark 32A or a circle 32B can be imparted to the sintered body 32 as shown in Fig. 6(c). The solid having a specific shape may be arranged so that these marks appear on the surface when the sintered body is scraped. In this way, the method for producing a sintered body according to this embodiment makes it possible to produce a wide variety of jewelry items, including those with a variety of color tones.

[0038] [Second embodiment] In this embodiment, a method for manufacturing a sintered body for producing a timepiece dial having gradation will be described.

[0039] The method for producing a sintered body according to this embodiment includes a mixed powder preparation step using a first metal powder and a second metal powder, a filling step for filling a mold, a pressure sintering step for sintering the mixed powder while applying pressure, a cutting step for cutting the sintered body, and a post-treatment step. As in the first embodiment, the first metal powder and the second metal powder are composed of any of gold, silver, platinum, palladium, copper, zinc, nickel, indium, gallium, aluminum, ruthenium, or an alloy containing at least one selected from these groups. The method for producing a sintered body according to this embodiment differs from the method for producing a sintered body according to the first embodiment in that it includes a step of cutting the sintered body. Therefore, a description of the similar steps will be omitted and the different steps will be mainly described.

[0040] In the manufacturing method of the sintered body according to the present embodiment, mixed powders M1 to M7 with different compounding ratios are prepared using a gold alloy (first metal powder) and a platinum alloy (second metal powder), and each mixed powder M1 to M7 is filled into a sintering mold 14, and the mixed powder is sintered while being pressurized to produce a rectangular parallelepiped sintered body or a cubic sintered body 40 (FIG. 7(a)). Next, a cutting process is performed to cut the sintered body to a predetermined thickness. By the cutting process, a plate-shaped sintered body 41 having a gradation is obtained as shown in FIG. 7(b). Thereafter, in a post-processing process, the plate-shaped sintered body 41 is processed into a circular shape. Then, as shown in FIG. 7(c), a watch dial 42 is produced by providing numbers and the like required for a watch dial on the surface of the processed sintered body 41.

[0041] In the method for producing a sintered body according to this embodiment, a sintered body 40 having a predetermined shape with a gradation of a predetermined shape is produced, and a part of the sintered body 40 can be used to produce a jewelry item (watch face).

[0042] [Third embodiment] In this embodiment, an example of producing a sintered body by generating a temperature gradient in the sintering mold 14 will be described with reference to Figures 8 and 9. This temperature gradient is generated by utilizing the electrical resistance of the upper punch 23A and the die 22A that constitute the sintering mold 14. In this embodiment, a cylindrical upper punch 23A is used. Note that the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0043] As shown in FIG. 8, the mixed powders M1 to M5 are filled into the space between the upper punch 23A and the spacer 24. The region R1 has a higher temperature than the region R2, in which the current path is the upper punch 23A and the die 22A, because the region R1 has only the upper punch 23A. In addition, the temperature of the lower side of the region R2 is lowered by flowing water through the water flow path 29 of the water cooling plate 28. In this way, by generating a temperature difference between the top and bottom in the vertical direction X of the sintering mold 14, mixed powders with different melting points can be sintered. The metal powder can be sintered without melting at a temperature of 80% to 85% of the melting point.

[0044] 9, the die 22B is configured so that the diameter of the lower portion is larger than the diameter of the upper portion, creating a temperature gradient in the sintering mold 14. In this case, the temperatures decrease in the order of region R3, region R4, and region R5. In this way, the shape of the die 22B can create a larger temperature gradient, allowing the metal powder to be sintered without melting. In addition to the configurations of the sintering mold 14 shown in Figures 8 and 9, a temperature difference of several tens of degrees to approximately 300 degrees can be created in the sintering mold 14 by adjusting the thickness of the upper punch 23A, the material of the upper punch 23A (graphite, super steel), and the thickness and shape of the dies 22A and 22B.

[0045] Although the present embodiment has been described above, it is possible to select and change the configurations given in the above embodiment to other configurations as appropriate without departing from the spirit of the present invention. For example, in this embodiment, two types of metal powder are used to impart gradation, but three or more types of metal powder can be used to produce jewelry with gradation. Furthermore, three or more types of metal powder can be used to create a temperature gradient in the sintering mold 14 and sintering can be performed by the spark plasma sintering method.

[0046] In addition, in this embodiment, an example was shown in which a sintered body having a gradation for use in a 5-layer or 7-layer jewelry was produced using 5 or 7 mixed powders with different compounding ratios, but a sintered body having 3 to 20 layers can also be produced depending on the color tone of the gradation, the desired thickness, etc. By forming such a layered structure, a gradation can be expressed in the sintered body.

[0047] In the second and third embodiments, examples were shown in which mixed powders with different compounding ratios were used, but the top layer of each mixed powder may be made of only the first metal powder, and the bottom layer may be made of only the second metal powder. In this embodiment, graphite was used for the lower punch 20, upper punch 23, core 21, and die 22 that constitute the sintering mold 14, but die steel, cemented carbide, and ceramics may also be used as appropriate depending on the type of metal powder to be sintered and the purpose of sintering. In this case, the same type of material may be used for all the members that constitute the sintering mold 14, or different types of materials may be used in appropriate combination for each member.

[0048] The shape of the sintering mold 14 is not limited to ring, cylinder, or rectangular parallelepiped, and can be changed as appropriate according to the desired shape of the jewelry to be produced. The number and mixing ratio of the mixed powders can be changed as appropriate depending on the jewelry to be produced, and the mixing ratio can be adjusted to a random mixing ratio rather than a regular ratio. By separately SPS sintering each mixed powder having a different mixing ratio of the first metal powder and the second metal powder, multiple sintered bodies that can express subtle colors can be produced. [Explanation of symbols]

[0049] 10 Spark plasma sintering equipment 11 Vacuum Chamber 12 Upper electrode 13 Lower electrode 14 Sintering mold 15 Control Unit 20 Lower punch 21 Core 22, 22A, 22B Die 23,23A Upper punch 24~27 spacer 28 Water cooler 29 Waterway 30, 31, 32 Sintered body 30A, 30B, 31A, 31B Pattern 40,41 Sintered body 42 Clock Face a,b distance M1~M8 mixed powder P1 gold alloy powder P2 Platinum alloy powder R1~R5 area S space X vertical direction Y left / right direction

Claims

1. A method for producing a sintered body for use in jewelry having gradation, comprising the steps of: a filling step of filling a form with layers of mixed powders, each of which has a different blending ratio of the first metal powder and the second metal powder, using at least a first metal powder and a second metal powder; A pressure sintering step of sintering the mixed powder packed in layers while applying pressure, The pressure sintering step is carried out by a spark plasma sintering method, and the pressure for pressing the mixed powder is increased stepwise while the heating rate of the sintering temperature is decreased stepwise. The method for producing a sintered body comprising the steps of:

2. The mold is cylindrical or columnar, and the mixed powders having different blending ratios are filled from the bottom to the top of the mold or in the circumferential direction of the mold. The method for producing a sintered body according to claim 1 .

3. the first metal powder is a gold alloy and the second metal powder is a platinum alloy; The gold alloy includes silver, copper, and palladium, and the platinum alloy includes platinum, palladium, and ruthenium. The method for producing a sintered body according to claim 1 or 2.

4. The particle size of the first metal powder and the second metal powder is 5 μm to 200 μm; The method for producing a sintered body according to claim 1 or 2.

5. In the filling step, a solid having a specific shape is placed in each of the mixed powders, and then the pressure sintering step is performed. The method for producing a sintered body according to claim 1 or 2.

6. The formwork has an upper punch, a first spacer attached to an upper end of the upper punch, a lower punch arranged opposite the upper punch, a second spacer attached to a lower end of the lower punch, a rod-shaped core member arranged inside the upper punch and inside the lower punch, and a die surrounding the core member; the die is positioned such that a distance between an upper end of the die and a lower end of the first spacer is longer than a distance between a lower end of the die and an upper end of the second spacer; In the pressure sintering step, a temperature gradient is generated in the mold to sinter the mixed powder. The method for producing a sintered body according to claim 1 or 2.

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