JP2018048357A - Punch for discharge plasma sintering, molding die for discharge plasma sintering, discharge plasma sintering device and discharge plasma sintering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a punch for discharge plasma sintering capable of stably conducting discharge plasma sintering by suppressing generation of breakage of a molding die for discharge plasma sintering in discharge plasma sintering, the molding die for discharge plasma sintering, a discharge plasma sintering device and a discharge plasma sintering method.SOLUTION: Punches 2 (2A and 2B) used for discharge plasma sintering is constituted by a columnar body having a first columnar part 21 having relatively large cross section area which is vertical to an axis and a second columnar part 22 having relatively small cross section area in same axis, and cross section shapes of the first and second columnar parts 21 and 22 are constituted to be almost similar shape each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a discharge plasma sintering punch, a discharge plasma sintering mold, a discharge plasma sintering apparatus, and a discharge plasma sintering method.

  Conventionally, as one of sintering methods for metals and ceramics, a discharge plasma sintering method (SPS: Spark Plasma Sintering, hereinafter abbreviated as “SPS”) is known. This discharge plasma sintering method is a method in which a molding material is filled with a solid or powdered molding material, and uniaxial pressurization and DC pulse voltage / current are simultaneously applied to the molding die and the molding material to sinter. is there.

  For example, FIG. 6 is a cross-sectional view showing a configuration of a conventional spark plasma sintering apparatus. A conventional discharge plasma sintering apparatus 100 ′ includes a discharge plasma sintering mold 10 ′, spacers 4 and 5, and a pressure ram 3 disposed at both ends thereof.

  The discharge plasma sintering mold 10 ′ is constituted by a cylindrical cylinder 1 having a hollow portion and a punch 2 ′ inserted from both ends of the cylinder 1 toward the inside. In the discharge plasma sintering mold 10 ′, when the cylinder 1 and the punch 2 ′ are combined so as to hold the molding material M therebetween, the discharge plasma sintering mold 10 ′ is assembled. The molding material M is sintered by pressurizing and compressing the molding material M with the punch 2 ′ and applying current to the punch 2 ′ and the cylinder 1 to heat them.

  In such a discharge plasma sintering apparatus 100 ′, the discharge plasma sintering mold 10 ′ is configured using, for example, graphite from the viewpoint of electrical conductivity and moldability (see, for example, Patent Documents 1 and 2). ). However, in the discharge plasma sintering mold 10 ′ made of graphite, when it is heated to a high temperature in an atmosphere containing oxygen, the graphite is gradually consumed, so that sintering in the atmosphere is not possible. It becomes possible.

  Therefore, in order to keep the surroundings in a vacuum state or a state filled with an inert gas, it is necessary to provide a vacuum chamber for blocking a portion where sintering proceeds and the peripheral portion from the outside. However, the mechanical strength of the discharge plasma sintering mold 10 ′ made of graphite is not sufficient to withstand repeated pressure changes accompanying withdrawing into and out of the high-pressure vacuum chamber, and the pressure applied to the molding material M is not sufficient. It was necessary to suppress the pressure to less than 100 MPa, and it was difficult to sinter the molding material M under ultrahigh pressure conditions exceeding 100 MPa.

  In order to solve such a problem, a method using a discharge plasma sintering mold made of silicon carbide has been proposed (see, for example, Non-Patent Document 1). Silicon carbide is not consumed even when heated to a high temperature in an oxygen atmosphere. Therefore, by using a mold composed of silicon carbide, sintering can be performed in the atmosphere, a vacuum chamber is not required, and mass productivity can be greatly improved. Furthermore, since silicon carbide is also a material having high strength, it can be sintered under ultrahigh pressure conditions exceeding 500 MPa.

  However, it has been found that if the sintering is repeated, the required load for performing the operation of taking out the molding material after the spark plasma sintering increases, and eventually the cylinder 1 is destroyed. Furthermore, it was also found that the higher the sintering temperature, the more the cylinder 1 is destroyed with a smaller number of sintering repetitions.

  Destruction of expensive silicon carbide cylinders is a major obstacle to realizing mass production of sintered bodies through industrialization.

  Therefore, when the cause of the cylinder breakage was examined, expansion of the punch 2 'was predicted. Therefore, an attempt was made to measure the diameter of the punch 2' every time it was sintered. As a result, the diameter of the portion of the punch 2 'located inside the hollow portion of the cylinder 1 hardly changed, whereas the diameter of the portion located outside the hollow portion of the cylinder 1 was changed every time the test was performed. I found that it was getting bigger. In addition, it was thought that the expansion of the diameter of the portion located inside the hollow portion of the cylinder 1 of the punch 2 ′ was suppressed by the wall surface of the hollow portion of the cylinder 1. From this result, when performing the operation of repeating the sintering and taking out the molding material, the diameter of the punch 2 ′ positioned outside the hollow portion of the cylinder 1 increases as the number of times of sintering increases, and the increased portion of the cylinder 1 It has been found that the interference with the cylinder increases and eventually the cylinder 1 is destroyed.

JP 11-335707 A Japanese Patent Laid-Open No. 2003-081649

K. Kakegawa, C.I. M.M. Wen, N.A. Uekawa, T .; Kojima, “SPS Using SiC Die”, Key Engineering Materials, Vol. 617, pp. 72-77, Jun. 2014

  The present invention has been made in view of such a situation, and suppresses the occurrence of breakdown of the discharge plasma sintering mold in the discharge plasma sintering, and stably performs the discharge plasma sintering. It is an object of the present invention to provide a discharge plasma sintering punch, a discharge plasma sintering mold, a discharge plasma sintering apparatus, and a discharge plasma sintering method.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, due to the plasma application, the portion of the punch located outside the hollow portion of the cylinder expands, causing the cylinder to be destroyed, and the diameter of the portion located outside the hollow portion of the cylinder to be reduced. It has been found that by using a silicon carbide mold that is smaller than the diameter of the portion located inside the hollow portion of the cylinder, the destruction of the cylinder can be suppressed, and the present invention has been completed. Specifically, the present invention provides the following.

  [1] A first invention of the present invention is a punch used for spark plasma sintering, and includes a first columnar portion having a relatively large cross-sectional area perpendicular to the axis and a relatively small first cross-sectional area. A columnar body having two columnar portions coaxially, and the cross-sectional shapes of the first and second columnar portions are discharge plasma sintering punches having substantially similar shapes.

  [2] In the second invention of the present invention, the similarity ratio (second columnar portion / first columnar portion) in the similar shape of the second columnar portion to the first columnar portion is 0.5 or more and 0. .9 or less, the discharge plasma sintering punch according to [1].

  [3] A third invention of the present invention is the spark plasma sintering punch according to [1] or [2], wherein the cross-sectional shapes of the first and second columnar parts are each a circle.

[4] According to a fourth aspect of the present invention, the ratio (h ₂ / h ₁ ) of the height (h ₂ ) of the second columnar part to the height (h ₁ ) of the first columnar part is The punch for spark plasma sintering according to any one of [1] to [3], which is 0.3 or more and 0.7 or less.

  [5] A fifth invention of the present invention is the discharge plasma sintering punch according to any one of [1] to [4], wherein the first and second columnar portions are made of a conductive material. is there.

  [6] A sixth invention of the present invention is the discharge plasma sintering punch according to [5], wherein the first and second columnar parts are made of silicon carbide.

  [7] A seventh invention of the present invention is a discharge plasma sintering mold for performing discharge plasma sintering by applying a voltage while pressurizing a molding material, and a cylinder having a hollow portion; [1] To the discharge plasma sintering punch according to any one of [6], wherein the discharge plasma sintering punch has the first columnar portion positioned inside a hollow portion of the cylinder, and 2 is arranged in the hollow part of the cylinder so that the two columnar parts are located outside the hollow part of the cylinder and at least the entire first columnar part is located inside the hollow part of the cylinder. This is a forming mold for spark plasma sintering.

  [8] An eighth invention of the present invention is a discharge plasma sintering apparatus provided with the discharge plasma sintering mold of [7].

  [9] A ninth invention of the present invention is a discharge plasma sintering method for sintering a sintering raw material by discharge plasma sintering using the discharge plasma sintering apparatus of [8].

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the fracture | rupture of the shaping | molding die for discharge plasma sintering in discharge plasma sintering can be suppressed, and discharge plasma sintering can be performed stably.

It is sectional drawing which shows the structure of a discharge plasma sintering apparatus. It is sectional drawing which shows the structure of the shaping | molding die for spark plasma sintering. It is sectional drawing which shows the structure of the cylinder used for the Example and the comparative example. The structure of a punch is shown, (a) is a perspective view, (b) is the sectional drawing. The structure of the conventional cylindrical punch is shown, (a) is a perspective view, (b) is the sectional drawing. It is sectional drawing which shows the structure of the conventional discharge plasma sintering apparatus. It is a schematic diagram which shows the method of taking out the molding material after spark plasma sintering.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment at all, In the range of the objective of this invention, it can add and change suitably.

1. Discharge Plasma Sintering Apparatus The discharge plasma sintering apparatus 100 of the present invention directly applies pulsed electric energy to the molding material M, and generates high energy of high temperature plasma generated instantaneously by spark discharge, such as thermal diffusion, electrolytic diffusion, etc. By applying to the above, it is possible to perform the sintering in a short time of about 3 to 30 minutes including the temperature raising time and the holding time.

  As shown in FIG. 1, a discharge plasma sintering apparatus 100 includes a discharge plasma sintering mold 10 including a cylinder 1 and punches 2 (2A, 2B). Although FIG. 1 shows a pair of punches 2, that is, one consisting of one punch 2A and the other punch 2B, it may be one. As will be described later, the discharge plasma sintering forming die 10 having the cylinder 1 and the punch 2 (2A, 2B) is characterized. A silicon carbide spacer 5, a metal spacer 4, and a pressure drum 3 are disposed in this order on both ends of the discharge plasma sintering mold 10 respectively.

  The silicon carbide spacer 5 is disposed between the discharge plasma sintering mold 10 and the pressure ram 3. Specifically, the silicon carbide spacer 5 is disposed so as to come into contact with the punch 2 (2A, 2B) in the discharge plasma sintering mold 10, and the pressure from the pressure ram 3 is applied to the punch 2 (2A, 2B). ) And the molding material M charged in the discharge plasma sintering mold 10 is compressed. By providing the silicon carbide spacer 5 in this manner, the pressure of the punch 2 can be dispersed on the lower bottom of a larger area, and the metal spacer 4 can be protected.

  The metal spacer 4 is used for protecting the pressure ram 3 and adjusting the vertical position of the mold 10. The metal spacer 4 is not particularly limited as long as it is made of a metal having conductivity and high strength. Further, the shape and size of the metal spacer 4 are not particularly limited. For example, the metal spacer 4 is slightly larger than the silicon carbide spacer 5 and may have a cylindrical shape.

  The pressurization ram 3 applies a predetermined pressure to the molding material M through the punch 2 (2A, 2B) of the discharge plasma sintering mold 10 and a pulse voltage / current.

  In the discharge plasma sintering apparatus 100, when the cylinder 1 and the punch 2 (2A, 2B) are combined so as to hold the molding material M therebetween, and the molding die 10 for discharge plasma sintering is assembled, the molding material is obtained. Sintering is performed by applying a voltage to M under pressure.

  Although not shown, the discharge plasma sintering apparatus 100 surrounds the discharge plasma sintering mold 10 and the silicon carbide spacer 5 from the viewpoint of sufficiently ensuring the conductivity of the silicon carbide spacer 5 made of silicon carbide. A heating unit can be provided. By heating the discharge plasma sintering mold 10 and the silicon carbide spacer 5 with this heating unit, sintering can be performed more efficiently.

  The molding material M is not particularly limited as long as a sintered body is formed by discharge plasma sintering. Specifically, for example, ceramics such as oxides, carbides, nitrides, borides, fluorides, metals, alloys, cermets, and the like can be used. Further, the shape is not particularly limited, and a powdery or solid raw material can be used.

2. As shown in FIGS. 1 and 2, the discharge plasma sintering mold 10 is used by being installed in the above-described discharge plasma sintering apparatus 100. It is a reaction field for performing discharge plasma sintering by applying a voltage while pressing.

  As shown in FIG. 2, the discharge plasma sintering mold 10 of the present invention includes a cylinder 1 and punches 2 (2A, 2B). In the discharge plasma sintering mold 10, the molding material M is sintered in a pressurized state in a space surrounded by the cylinder 1 and the punch 2 (2A, 2B). Hereafter, each component of the shaping | molding die 10 for discharge plasma sintering is demonstrated concretely.

(cylinder)
As shown in FIGS. 3A and 3B, the cylinder 1 is a cylindrical member having a hollow portion, for example. As shown in FIG. 2, the cylinder 1 guides the vertical movement of the cylindrical punch 2 (2A, 2B) inserted into the hollow portion. The cylinder 1 is charged with the molding material M, and the molding material M is pressurized and compressed by applying pressure by the punch 2 (2A, 2B).

  It does not specifically limit as a magnitude | size of the cylinder 1, It can adjust suitably with the yield of an installation or a sintered compact.

  Moreover, it is preferable that the cylinder 1 is comprised with an electroconductive material, for example, it is especially preferable that it is comprised with silicon carbide. By using the cylinder 1 made of silicon carbide, high-temperature plasma sintering can be performed in an oxygen atmosphere without forming a vacuum atmosphere, and cracking can be suppressed even under such high-temperature heating conditions.

(punch)
As shown in FIG. 2, the punch 2 (2 </ b> A, 2 </ b> B) is inserted into the hollow portion of the cylinder 1 to compress and compress the molding material M charged in the cylinder 1 together with the cylinder 1. Specifically, one punch 2A is inserted from one end of the hollow portion of the cylinder 1 in which the molding material M is inserted, and the other punch 2B is inserted from the other end, and these punches 2 (2A, 2B) are inserted. Thus, a pressure is directly applied to the molding material M inside the cylinder 1.

  In the present embodiment, as shown in FIGS. 4A and 4B, the punch 2 (2A, 2B) has a first columnar portion 21 and a cross-sectional area that are relatively large in cross-sectional area perpendicular to the axis. This is a columnar body having a relatively small second columnar portion 22 coaxially.

  Here, as described above, in the prior art, when performing the operation of repeating the sintering and taking out the molding material, the diameter of the punch located outside the hollow portion of the cylinder increases as the number of times of sintering increases, Increased interference with the cylinder will increase, eventually leading to cylinder destruction.

  On the other hand, since the punch 2 (2A, 2B) has the above-described configuration, the punch 2 (2A, 2B) is combined with the cylinder 1 to form the discharge plasma sintering mold 10 and is used for the discharge plasma sintering operation. In this case, interference with the cylinder 1 can be prevented. For this reason, generation | occurrence | production of the fracture | rupture of the shaping | molding die for discharge plasma sintering in discharge plasma sintering can be suppressed, and discharge plasma sintering can be performed stably.

  When the punch 2 (2A, 2B) is combined with the cylinder 1 to form the discharge plasma sintering mold 10, the first columnar portion 21 is positioned inside the hollow portion of the cylinder 1, and the first The two columnar portions 22 are arranged in the hollow portion of the cylinder 1 so as to be located outside the hollow portion of the cylinder 1. By being arranged in this way, even if the diameter of the punch 2 (2A, 2B) increases with sintering, the interference of the punch 2 (2A, 2B) with the cylinder 1 can be prevented.

  The punch 2 (2A, 2B) is arranged so that at least the entire first columnar portion 21 is located inside the hollow portion of the cylinder 1, that is, the first columnar portion 21 and the second columnar portion 22 The joint is disposed in the hollow portion of the cylinder 1 so as to be located inside the hollow portion of the cylinder 1. By being arranged in this way, the cylinder 1 can be prevented from being destroyed when the molding material M is taken out.

  Specifically, the cross-sectional shape of the first and second columnar portions 21 and 22 can be configured in a shape such as a circle, an ellipse, an oval, a track shape, a square, a rectangle, a polygonal shape, A circle is preferred. That is, the punch 2 (2A, 2B) is preferably a cylinder with a different diameter coaxial.

  In addition, the punch 2 (2A, 2B) can smoothly move up and down in a relative relationship with the size (diameter) of the cylinder 1 and can effectively apply pressure to the molding material M. It is composed of various sizes (diameters).

  Specifically, the diameter of the punch 2 (2A, 2B) (specifically, the diameter of the first columnar portion 21 disposed inside the cylinder 1) is slightly smaller than the diameter of the hollow portion of the cylinder 1. A small degree is preferred. For example, the size is preferably 99.8% or less and more preferably 99.6% or less with respect to the diameter of the hollow portion of the cylinder 1. On the other hand, the diameter of the punch 2 is preferably 99.3% or more and more preferably 99.5% or more with respect to the diameter of the hollow portion of the cylinder 1.

  Further, the similarity ratio (second columnar portion / first columnar portion) in the similar shape of the second columnar portion 22 with respect to the first columnar portion 21 is not particularly limited, but is 0.5 or more, for example. Is preferably 0.55 or more, and more preferably 0.6 or more. When the similarity ratio (second columnar portion / first columnar portion) is 0.5 or more, the contact area between the second columnar portion 22 and the spacer 5 is increased, and local voltage and pressure are applied. Suppressing and preventing destruction of the spacer. On the other hand, the similarity ratio (second columnar portion / first columnar portion) in the similar shape of the second columnar portion 22 with respect to the first columnar portion 21 is not particularly limited. Preferably, it is 0.88 or less, and more preferably 0.8 or less. When the similarity ratio (second columnar portion / first columnar portion) is 0.9 or less, even if the portion of the second columnar portion 22 expands, the cylinder 1 is pressurized by the expansion. Can be suppressed.

The ratio (h ₂ / h ₁ ) of the height (h ₂ ) of the second columnar part 22 to the height (h ₁ ) of the _first columnar part 21 is not particularly limited. It is preferable from the viewpoint of mechanical strength and the like that it is 3 or more and 0.7 or less. The height ratio (h ₂ / h ₁ ) is more preferably 0.35 or more and 0.65 or less, and further preferably 0.4 or more and 0.6 or less.

  Like the cylinder 1, the punch 2 (2A, 2B) is preferably made of a conductive material. Specifically, it is preferably composed of silicon carbide from the viewpoint of efficiently performing discharge plasma sintering.

  As shown in FIG. 2, the interval between the punches 2 (2A, 2B) varies depending on the amount of the molding material M, and the lengths thereof vary. In this case, it is necessary to adjust according to the length as appropriate. On the other hand, in mass production, punches 2 (2A, 2B) suitable for mass-produced varieties are prepared, and during mass production, the same punch 2 (2A, 2B) can be used.

  In addition, when the punch 2 (2A, 2B) is composed of a molding material M and a chemically active material under a high temperature condition, a reaction occurs between the punch 2 (2A, 2B) and the molding material M. Preventive materials can be provided. As the reaction inhibitor, for example, a metal plate or carbon paper can be used.

  Here, as shown in FIG. 2, in the discharge plasma sintering mold 10 (see FIG. 2) provided with a pair of punches 2 (2 </ b> A, 2 </ b> B), from one end portion to the hollow portion of the cylinder 1. The punch 2A is inserted, and then the molding material M is charged into the hollow portion from the other end of the cylinder 1. Thereafter, the other punch 2B is inserted from the end on the side where the molding material M is inserted, so that a state in which pressure is applied to the molding material M by the punches 2A and 2B is set. The discharge plasma sintering mold 10 in which the molding material M is charged in this way is placed in the discharge plasma sintering apparatus 100 (see FIG. 1), and pressure is applied to the molding material M.

  In addition, although the aspect provided with the cylindrical cylinder 1 and a pair of column-shaped punch 2 (2A, 2B) was illustrated as the shaping | molding die 10 for discharge plasma sintering, it is not limited to this. For example, one of the openings of the cylinder 1 can be sealed, and the punch can be inserted only from the other opening.

3. Discharge Plasma Sintering Method The discharge plasma sintering method according to the present embodiment performs discharge plasma sintering using the above-described discharge plasma sintering apparatus.

  According to such a discharge plasma sintering method, the punch 2 (2A, 2B) is expanded by repeated sintering, and a cylinder is applied by applying pressure on the contact surface of the expanded portion of the punch 2 (2A, 2B). 1 destruction can be effectively suppressed. This is because the punch 2 (2A, 2B) is preliminarily provided with a columnar body having a first columnar portion 21 having a relatively large cross-sectional area perpendicular to the axis and a second columnar portion 22 having a relatively small cross-sectional area. The cross-sectional shape of the 1st and 2nd columnar parts 21 and 22 is comprised so that it may be a substantially similar shape mutually. By this, destruction of the cylinder 1 and the silicon carbide spacer 5 can be prevented. As a result, defective sintering can be prevented, and the discharge plasma sintering can be stably repeated, thereby improving the yield.

  The treatment conditions of the discharge plasma sintering method are not particularly limited. For example, the treatment may be performed by applying a pressure of 100 MPa to 1 GPa under atmospheric conditions at a temperature condition (attainment temperature) of 1000 ° C. to 2000 ° C. it can.

  After the sintering is completed, the punch 2 (2A, 2B) is inserted into the cylinder 1 and moved to the SPS apparatus, the punch 2 (2A, 2B) is removed from the cylinder 1 and the sintered molding material M is taken out. . However, since the cylinder 1 and the punch 2 (2A, 2B) are fixed at high temperature during sintering, the cylinder 1 with the punch 2 (2A, 2B) still inserted after the temperature is lowered is moved out of the apparatus. 7, after placing the cylinder on the receiving jig 7, the punch 2 (2 </ b> A, 2 </ b> B) is loaded in the direction of the arrow, and the molding material M is taken out in the manner of punching. The weight is usually several to several tens kg although it depends on the degree of fixation.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to a following example at all.

(Example)
According to the cylinder 1 shown in FIG. 3, a pair of discharge plasma sintering punches 2 (2A, 2B) of the present invention shown in FIGS. 3 and 4 (a) and FIG. 4 (b), the structure of the discharge plasma sintering mold 10 shown in FIG. 2, using the cylinder 1 and the punch 2 (2A, 2B), that is, FIG. A discharge plasma sintering test was performed using punches 2 (2A, 2B) having a step with coaxial steps of different diameters shown in (a) and (b).

  In addition, 2.5 g of alumina powder was used as the molding material M. The temperature was raised to 1200 ° C. at a rate of 100 ° C./min, held there for 10 minutes, and then lowered to room temperature. Finally, with the punch 2 (2A, 2B) inserted, the cylinder 1 was taken out of the apparatus, and FIG. The punch 2 (2A, 2B) and the molding material M were taken out by the method shown. In this method, the sintering test was repeated 50 times using the same cylinder 1 and punch 2 (2A, 2B). However, the cylinder 1 was not broken when the molding material M was taken out after sintering.

(Comparative example)
As a comparative example, a test using a cylindrical punch 2 'according to the prior art shown in FIGS. 5 (a) and 5 (b) was performed. The sintering conditions were the same as in the example, and the molding material M was taken out by punching out the punch 2 'by the method shown in FIG. As a result, the interference with the cylinder 1 started by the expansion of the punch 2 'from the third sintering test, and the cylinder 1 was destroyed at the fifth time.

1 cylinder 2 punch (discharge plasma sintering punch)
2A One punch 2B The other punch 2 'Conventional punch 3 Pressure ram 4 Metal spacer 5 Silicon carbide spacer 6 Receiving jig 10 Discharge plasma sintering mold 10' Conventional discharge plasma sintering mold 21 First columnar part 22 Second columnar part 100 Discharge plasma sintering apparatus 100 'Conventional discharge plasma sintering apparatus

Claims (9)

A punch used for spark plasma sintering,
A columnar body coaxially having a first columnar portion having a relatively large cross-sectional area perpendicular to the axis and a second columnar portion having a relatively small cross-sectional area;
The cross section of the first and second columnar portions is a discharge plasma sintering punch that is substantially similar to each other.   2. The discharge according to claim 1, wherein a similarity ratio (second columnar portion / first columnar portion) in a similar shape of the second columnar portion with respect to the first columnar portion is 0.5 or more and 0.9 or less. Punch for plasma sintering.   3. The spark plasma sintering punch according to claim 1, wherein cross-sectional shapes of the first and second columnar portions are each a circle. The ratio (h ₂ / h ₁ ) of the height (h ₂ ) of the second columnar part to the height (h ₁ ) of the first columnar part is 0.3 or more and 0.7 or less. The punch for spark plasma sintering of any one of 1-3.   The discharge plasma sintering punch according to any one of claims 1 to 4, wherein the first and second columnar portions are made of a conductive material.   6. The discharge plasma sintering punch according to claim 5, wherein the first and second columnar parts are made of silicon carbide. A discharge plasma sintering mold that performs discharge plasma sintering by applying a voltage while pressing a molding material,
A cylinder having a hollow portion and the discharge plasma sintering punch according to any one of claims 1 to 6, wherein the first columnar portion is hollow in the cylinder. And the second columnar portion is positioned outside the hollow portion of the cylinder, and at least the entire first columnar portion is positioned inside the hollow portion of the cylinder. A discharge plasma sintering mold disposed in the hollow portion of the cylinder.   The discharge plasma sintering apparatus provided with the shaping | molding die for discharge plasma sintering of Claim 7.   A discharge plasma sintering method for sintering a sintering raw material by discharge plasma sintering using the discharge plasma sintering apparatus according to claim 8.

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