JP2017091980A - Discharge plasma sintering device and continuous type discharge plasma sintering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge plasma sintering device and a continuous type discharge plasma sintering device, capable of obtaining sintered articles whose characteristic deviation is small without flowing excessive pulse current.SOLUTION: A discharge plasma sintering device includes: discharge plasma sintering means for arranging a cartridge 11 composed of a molding die and upper/lower punches inserted into the molding die in a sintering room 13 by including a chamber 12 and the cylindrical sintering room 13 constructed by a thermal insulation material installed in the chamber, compressing a raw material in the molding die using the upper/lower punches, and sintering the raw material by flowing pulse-shaped current between the upper/lower punches; and means for performing high-frequency induction heating of the molding die or the raw material outside of the sintering room 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sintering apparatus that sinters a powdery raw material, and more particularly to a discharge plasma sintering apparatus and a continuous discharge plasma sintering apparatus using a discharge plasma sintering means.

  In the discharge plasma sintering, a discharge plasma generated instantaneously by a discharge phenomenon when a pulsed large current is passed between compressed powder particles is applied to the sintering. Compared to a conventional sintering method using only pressurization and heating, it has a feature that it can be sintered at a temperature as low as 200 to 500 ° C. and in a short time of about several minutes. Since rapid temperature rise by heat generation only on the particle surface is possible, grain growth of the starting material can be suppressed, and a dense sintered body can be obtained in a short time. Since it can prevent the destruction of the powder, it can be applied to materials that are difficult to obtain by conventional general sintering methods, and it is beginning to be used in thermoelectric materials and magnetic materials.

  In the conventional spark plasma sintering apparatus, a cartridge composed of a forming die and an upper punch and a lower punch inserted in the forming die is arranged in a vacuum chamber, and the powder raw material in the forming die is several tons by upper and lower punches. The powder raw material is sintered by compressing it by applying pressure and passing a pulsed current through the upper and lower punches and the forming die. An example of a conventional spark plasma sintering apparatus is described in Patent Document 1.

JP 2001-348277 A

  In a conventional spark plasma sintering apparatus, when a pulse current is applied, there is a current flowing from the upper punch to the lower punch via the powder raw material and a current flowing from the upper punch to the lower punch via the forming die. . The current passing through the raw material directly contributes to the discharge plasma sintering, and the current passing through the forming die serves to raise the raw material temperature. The ratio of the current passing through the raw material and the current passing through the forming die is determined by the resistivity of the powder raw material and the shape of the forming die and punch, but the resistivity of the powder raw material varies depending on the pressed state, and the shape of the tip of the punch is the raw material Deformation over time due to damage due to reaction with. For this reason, it is difficult to stably perform both temperature control and discharge plasma control in the conventional method in which both functions of discharge plasma sintering and heating are realized only by pulse energization, resulting in variations in quality. It was.

  In addition, since the conventional vacuum chamber does not have a heat retaining function, extra power is required to compensate for the heat escaping from the servo press shaft via the punch and the heat radiating from the forming die. Necessary. Furthermore, when sintering at high temperatures for a long time, the temperature does not rise only for the punch, the forming die, and the sintering raw material, but the temperature rises in all parts where the pulse current flows. A large cooling system is required to hold down.

  Accordingly, the present invention has been made to solve such a problem, and a discharge plasma sintering apparatus and a continuous apparatus capable of obtaining a good sintered body with little characteristic variation without flowing an excessive pulse current. An object of the present invention is to provide a type discharge plasma sintering apparatus.

  In order to solve the above-mentioned problem, in a first aspect, the discharge plasma sintering apparatus of the present invention includes a chamber and a cylindrical sintering chamber constituted by a heat insulating material installed in the chamber, and a molding die. And a cartridge composed of an upper punch and a lower punch inserted into the molding die are disposed in the sintering chamber, and the raw material in the molding die is compressed using the upper and lower punches, and between the upper and lower punches. A discharge plasma sintering means for causing a pulsed current to flow through and sintering means, and a means for high-frequency induction heating the forming die or the raw material outside the sintering chamber. In this way, heat insulation performance is improved by using a cylindrical sintering chamber made of a heat insulating material, and pulse current is minimized by high-frequency induction heating in addition to heating by pulse energization. Thus, the pulse power supply can be reduced in size. Further, by using the high frequency induction heating together, it becomes possible to increase the temperature intensively only at a necessary portion, and it is possible to suppress abnormal heat generation at the boundary between the punch and the powder raw material and suppress damage to the punch tip. As an example of the heat insulating material, a molded heat insulating material made of carbon felt or the like can be used. Note that the above-described chamber needs functions of evacuation and water cooling. For example, a water-cooled chamber made of stainless steel can be used. Quartz chambers are also conceivable, but metal is easier to obtain confidential performance and easier to manufacture. The raw material to be inserted into the molding die is a powder raw material or a raw material pellet produced by molding and pressing the powder raw material.

  According to a second aspect, in the plasma sintering apparatus of the first aspect, the present invention is characterized in that the forming die has a layered portion made of an insulator or a high-resistance body at the center in the vertical direction. In the case of sintering conductive powder raw material, it is possible to energize the powder raw material almost concentrated, and sintering with much less pulse current than when the molding die is energized also for heating. Can be obtained.

  In a third aspect, the present invention relates to the plasma sintering apparatus according to the first or second aspect, wherein the press apparatus includes a press shaft that presses the upper punch or the lower punch of the cartridge mounted in the sintering chamber. Is installed above or below the sintering chamber, and a press stand for holding the lower punch or the upper punch of the cartridge is installed below or above the sintering chamber facing the press shaft across the cartridge, The material of the portion in contact with the upper punch or the lower punch at the tip of the press shaft and the portion in contact with the lower punch or the upper punch of the press table is carbon. In the invention of this aspect, the cartridge is pressed between the press shaft and the press stand of the press device. In this case, the press shaft may be pushed from above or from below. Moreover, the carbon material is used for the contact part with a press shaft and the upper and lower punches of a press stand. Thereby, compared with the case where a press shaft and a press stand are all comprised with a metal material, the damage by the heat | fever of a cartridge can be prevented. On the other hand, although carbon is a conductive material, a metal is desirable for facilitating the flow of current. In the invention of this aspect, a combination of two materials can be used. In addition, as a press apparatus, a hydraulic press apparatus, a servo press apparatus, etc. can be used.

  In a fourth aspect, the present invention comprises a chamber and a cylindrical sintering chamber constituted by a heat insulating material installed in the chamber, and includes a molding die, an upper punch and a lower punch inserted into the molding die. Discharge plasma sintering in which a cartridge comprising the above is placed in the sintering chamber, the powder raw material in the forming die is compressed using the upper and lower punches, and a pulsed current is passed between the upper and lower punches. And a means for high-frequency induction heating the forming die or the powder raw material outside the sintering chamber, and a preliminary chamber for storing a cartridge before sintering, and a cartridge after sintering for cooling. A cooling chamber and at least one mounting chamber, the mounting chamber including at least two cartridge storage portions for storing the cartridge before or after sintering, and the cartridge storage portion; The cartridge storage unit moving mechanism that moves the unsintered cartridge from the unloading position from the preliminary chamber to the unloading position to the sintering chamber or the uncooled cartridge from the unloading position from the sintering chamber. At least one of a cartridge storage unit moving mechanism that moves to a loading position into the chamber, and the chamber, the mounting chamber, the spare chamber, and the cooling chamber can be evacuated independently, A continuous type comprising a shutter that can be opened and closed while maintaining a vacuum state between the mounting chamber, between the mounting chamber and the chamber, and between the mounting chamber and the cooling chamber. A spark plasma sintering apparatus is provided.

  When performing the sintering operation using the plasma discharge sintering apparatus according to the first to third aspects, after the cartridge containing the powder raw material is carried into the sintering chamber in the chamber, the chamber is evacuated and sintered. When the cartridge is taken out after sintering, it is necessary to sufficiently cool the cartridge in a vacuum state and take it out to the atmosphere. Therefore, when performing a continuous sintering operation, an operation time required for evacuation of the chamber and an operation time required for cooling after sintering are required for each sintering operation. It takes a lot of time other than time.

  The invention of this aspect makes it possible to greatly reduce the time required for such a continuous sintering operation. According to the invention of this aspect, the cartridge containing the powder raw material is first carried into the spare chamber, and after the carry-in, the spare chamber is evacuated. After that, the shutter of the mounting chamber kept in a vacuum state is opened and loaded into the cartridge housing portion therein, and the shutter of the mounting chamber is closed. Thereafter, the cartridge storage unit moving mechanism moves to a loading position into the sintering chamber, the chamber shutter is opened, and the chamber shutter is loaded into the sintering chamber, and the chamber shutter is closed. During the loading operation, the mounting chamber and the chamber are both kept in a vacuum state, so that evacuation is not required every time the chamber cartridge is loaded. Further, the unloading to the mounting chamber after sintering is performed in a state where the vacuum state is maintained, and thereafter, the unloading is carried into the cooling chamber in the vacuum state and cooled there. In other words, the cooling of the cartridge after sintering and the sintering operation of the next cartridge can be performed simultaneously. Also, a new cartridge can be carried into the spare chamber at the same time. As a result, the time required for the continuous sintering operation can be greatly reduced. In addition, a mounting chamber for carrying the cartridge from the preliminary chamber into the sintering chamber in the chamber and a mounting chamber for carrying the sintered cartridge from the sintering chamber to the cooling chamber are provided separately above and below the sintering chamber. Alternatively, one mounting chamber may be provided on one of the upper and lower sides of the sintering chamber, and both the above loading and unloading may be performed therein.

  In a fifth aspect, the present invention provides the continuous discharge plasma sintering apparatus according to the fourth aspect, wherein the forming die has a layered portion made of an insulator or a high-resistance body at the center in the vertical direction. And In the case of sintering conductive powder raw material, it is possible to energize the powder raw material almost concentrated, and sintering with much less pulse current than when the molding die is energized also for heating. Can be obtained.

  According to a sixth aspect, the present invention provides the continuous discharge plasma sintering apparatus according to the fourth or fifth aspect, wherein the mounting chamber has one mounting chamber, and the mounting chamber includes the cartridge housing portion and the sintering chamber. The cartridge before unloading moves from the unloading position from the preliminary chamber to the loading position into the sintering chamber, and the unloading position of the cartridge after sintering from the sintering chamber to the cooling chamber. A pressing device having a press shaft that presses the upper punch of the cartridge mounted in the sintering chamber is provided above the sintering chamber, and is provided below the sintering chamber. A press stand for holding the lower punch of the cartridge, and the press stand has a press stand moving mechanism capable of moving the cartridge between the sintering chamber and the mounting chamber under control. And wherein the door.

  In the invention of this aspect, there is one mounting chamber, the upper punch is pressed by the press shaft of the press device while the lower punch is supported by the press stand, the powder raw material is compressed and sintered by the discharge plasma, and sintered. The rear press table can be moved up and down to return the sintered cartridge to the mounting chamber. When the mounting chamber is arranged above the incineration chamber, it is carried in and out from above, and when the mounting chamber is arranged below the incineration chamber, it is carried in and out from below.

  In a seventh aspect, the present invention provides the continuous discharge plasma sintering apparatus according to the sixth aspect, wherein the mounting chamber is disposed above the sintering chamber, and the preliminary chamber is disposed above the mounting chamber. The cooling chamber is arranged below the mounting chamber. In the invention of this aspect, for example, an arrangement for performing the following sintering operation is possible. First, a cartridge containing raw materials is inserted into the spare chamber from above, and the spare chamber is evacuated. From the position, the shutter is opened and moved to the cartridge storage section in the mounting chamber immediately below, and the shutter is closed. Then, the cartridge housing is moved directly above the sintering chamber, the shutter is opened, and the cartridge is moved into the sintering chamber. After sintering, the cartridge is moved to the cartridge storage section in the mounting chamber directly above the sintering chamber, and the cartridge storage section is moved to the loading position directly above the cooling chamber and stored in another cartridge storage section. The cartridge containing the new raw material is moved directly above the incineration chamber. Thereafter, the cartridge after sintering is carried into the cooling chamber, the cartridge before sintering is carried into the sintering chamber, and the shutter is closed.

  In an eighth aspect, the present invention provides the continuous discharge plasma sintering apparatus according to the seventh aspect, wherein the cartridge housing portion moving mechanism is a rotating mechanism, and the at least two cartridge housing portions are the rotating mechanism. It is arrange | positioned at the object on the rotating shaft. For example, a preliminary chamber and a cooling chamber are arranged above and below the mounting chamber, two cartridge storage portions are provided at positions 180 degrees symmetrical to the rotation axis, and one cartridge storage portion is directly above the sintering chamber. In some cases, the other cartridge housing can be located between the reserve chamber and the cooling chamber.

  In a ninth aspect, the present invention provides the continuous discharge plasma sintering apparatus according to the eighth aspect, wherein the mounting chamber includes at least four cartridge storage portions. In the invention of this aspect, it is possible to perform a plurality of cartridge loading / unloading operations between the preliminary chamber and the cooling chamber by providing four or more cartridge storage portions and moving them by sequentially rotating them. Since it is not necessary to carry out each time of sintering, a more efficient continuous sintering operation becomes possible. Note that the number of cartridge storage units can be arbitrarily set within a range in which the shape of the apparatus is allowed, such as 6, 8, 10, and the like.

  As described above, according to the present invention, there can be obtained a discharge plasma sintering apparatus and a continuous discharge plasma sintering apparatus capable of obtaining a good sintered body with little characteristic variation without flowing an excessive pulse current.

1 is a schematic cross-sectional view showing an outline of a sintering furnace of a discharge plasma sintering apparatus according to Example 1. FIG. Sectional drawing which shows the structure of a cartridge. Sectional drawing which shows the structure of the cartridge which consists of a shaping | molding die which provided the insulator layer in the center. FIG. 4 is a schematic cross-sectional view showing an outline of a sintering furnace of a continuous discharge plasma sintering apparatus according to Example 2. The top view which shows arrangement | positioning of a cartridge accommodating part. The typical sectional view showing the outline of the sintering furnace of the state where the cartridge which put the next raw material into the preliminary chamber was moved simultaneously with the sintering operation. The typical sectional view showing the outline of the sintering furnace in the state where the next cartridge was moved onto the sintering chamber after the end of the sintering operation. The typical top view which shows the outline of the modification of the sintering furnace of a continuous type discharge plasma sintering apparatus.

  Hereinafter, the discharge plasma sintering apparatus and continuous discharge plasma sintering apparatus of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof is omitted.

  1 is a schematic cross-sectional view showing an outline of a sintering furnace of a discharge plasma sintering apparatus according to Example 1. FIG. The discharge plasma sintering apparatus according to this embodiment includes an electric control panel and a sintering furnace 1, and FIG. 1 shows the sintering furnace 1. The sintering furnace 1 includes both discharge plasma sintering means and high-frequency induction heating means, and the electric control panel includes an inverter-controlled pulse power source that generates a pulse current for discharge plasma sintering, and a high-frequency for high-frequency induction heating. It is composed of an oscillator power supply and a servo press power supply. The sintering furnace 1 is for applying pressure to a chamber 12 and a cylindrical sintering chamber 13 constituted by a heat insulating material installed in the chamber 12 and a cartridge 11 holding a raw material inserted into the chamber 12. Although not shown, the servo press 16 provided with the shaft 17, the vacuum pump 18 for discharging the gas in the chamber 12, and an argon gas introduction unit and a flow meter are provided. Moreover, the induction heating coil 19 for high frequency induction heating is provided. The chamber 12 has a structure that can maintain a vacuum state in both the state where the shaft 17 is inserted into the chamber 12 and the state where the shaft 17 is pulled up. A press table 20 that supports pressure is disposed below the cartridge 11, and the press table 20 is coupled to a press table moving mechanism 22 that moves the press table 20 up and down via a press table shaft 21. After the sintering, the press stand 20 is moved upward to take out the sintered body from the upper part of the chamber 12. As the heat insulating material for the sintering chamber 13, a molded heat insulating material made of carbon felt or the like is used.

  The shaft lower end portion 23 in contact with the upper punch at the tip of the shaft 17 and the press table upper end portion 24 in contact with the lower punch in the press table are made of carbon. The other parts of the shaft and press stand are metal such as stainless steel.

  FIG. 2 is a cross-sectional view showing the configuration of the cartridge 11. The cartridge 11 includes a forming die 41 and an upper punch 42 and a lower punch 43 that are inserted into the forming die 41. In the spark plasma sintering, the powder raw material 44 in the molding die 41 is compressed by applying pressure between the upper and lower punches 42 and 43 by the shaft 17 of the servo press 16, and then a pulsed current is passed between the upper and lower punches 42 and 43. And sinter.

Next, the case where Mg ₂ Si (magnesium silicide) is sintered using the sintering apparatus of the present embodiment will be described in detail. In this case, the cartridge 11 is integrally formed of a carbon material with a forming die 41 having an outer diameter of 50 mm, an inner diameter of 20 mm, and a height of 60 mm, and a distal end portion having an outer diameter of 20 mm and a height of 35 mm and a base portion having an outer diameter of 75 mm and a height of 8 mm. The upper punch 42 and the same lower punch 43 are used.

  3 g of powdered Mg (magnesium) and Si (silicon) were weighed at a predetermined ratio, and this powder raw material was filled in the forming die 41 of the cartridge 11 and sintered by this apparatus.

First, the cartridge 11 filled with the powder raw material 44 is set in the sintering furnace 1 of the main sintering apparatus, evacuated to 1 Pa or less by the vacuum pump 18, and then replaced with Ar gas. With Ar gas flowing at 5 l / min, the servo press 16 was used to maintain the compression pressure at 20 MPa / cm ² . In this state, a high frequency induction heating power source was turned on and heated at 4 KW for 30 seconds to raise the temperature to 450 ° C. Thereafter, the output of the high frequency induction heating power supply is set to 3 kW, and the pulse energization of the discharge plasma sintering is increased to 850 ° C. by repeating the ON state with a current of 1300 A and a pulse width of 150 msec and the OFF state of a current of 0 A and a pulse width of 10 msec. Held for 3 minutes. Thereafter, the pressure was released and the power was turned off.

An Mg ₂ Si sintered body having an outer diameter of 20 mm and a height of 5 mm was obtained by the above-described pulse energization and sintering by high-frequency induction heating. The obtained sintered body had a density of 96% or more. Under the same conditions, when the discharge plasma sintering was carried out only by pulse energization, the density of the obtained sintered body was 92%, and the density of the sintered body was only about 80% by high frequency induction heating alone. . As a result, the effect of the present invention using both pulse energization and high frequency induction heating was confirmed.

  In the present embodiment, a cartridge using a molding die having a layered portion made of an insulator or a high-resistance material at the center in the vertical direction can be used. FIG. 3 is a cross-sectional view showing the structure of the cartridge composed of the forming die 46 having the insulating layer 45 provided at the center in this way. When the conductive powder raw material is sintered, the cartridge 11a shown in FIG. 3 can be used so that the powder raw material can be energized in a concentrated manner, much more than when the molding die is energized also for heating. Sintering can be obtained with a small pulse current.

It will be described in detail for the case of sintering the Al 2 _O 3 _(aluminum oxide) with a discharge plasma sintering apparatus of the present embodiment. In this case, the cartridge 11 is integrally formed of a carbon material with a molding die 41 having an outer diameter of 39 mm, an inner diameter of 20 mm, and a height of 68 mm, and a tip portion having an outer diameter of 20 mm and a height of 35 mm and a base portion of an outer diameter of 50 mm and a height of 8 mm. The upper punch 42 and the lower punch 43 are configured.

  3 g of cutting powdery Al (aluminum) was weighed, and this powder raw material was filled in the forming die 41 of the cartridge 11 and sintered in this apparatus.

First, the cartridge 11 filled with the powder raw material 44 is set in the sintering furnace 1 of the main sintering apparatus and placed in the high-frequency induction heating portion, evacuated to 1 Pa or less by the vacuum pump 18 and then replaced with Ar gas. With Ar gas flowing at 5 l / min, the servo press 16 was used to maintain the compression pressure at 20 MPa / cm ² . In this state, a high frequency induction heating power source was turned on and heated at 4 KW for 30 seconds to raise the temperature to 450 ° C. Thereafter, the output of the high frequency induction heating power source is set to 4 kW, and the pulse energization of the discharge plasma sintering is raised to 1200 ° C. by repeating the ON state with a current of 1700 A and a pulse width of 150 msec and the OFF state of a current of 0 A and a pulse width of 10 msec. Held for 3 minutes. Thereafter, the pressure was released and the power was turned off.

An Al ₂ O ₃ sintered body having an outer diameter of 20 mm and a height of 3 mm was obtained by the above-described pulse energization and sintering by high-frequency induction heating. The obtained sintered body has a density of 77%, which is higher than the density of the sintered body sintered only by pulsed current of discharge plasma sintering and the density of the sintered body sintered only by high frequency induction heating. was gotten.

  FIG. 4 is a schematic cross-sectional view showing an outline of a sintering furnace of a continuous discharge plasma sintering apparatus according to Embodiment 2 of the present invention. The continuous type discharge plasma sintering apparatus of the present embodiment is composed of an electric control panel and the like and the sintering furnace 2 as in the first embodiment, and FIG. The basic configuration of the portion for sintering in the continuous discharge plasma sintering apparatus of the present embodiment is the same as that of the first embodiment. That is, the sintering furnace 2 of the present embodiment also has a cylindrical sintering chamber 13 constituted by the chamber 12 and a heat insulating material installed in the chamber 12, and a cartridge holding the raw material inserted into the chamber 12. The servo press provided with the shaft 17 for applying a pressure, the vacuum pump for discharging | emitting the gas in the chamber 12, etc. are provided. Moreover, the induction heating coil 19 for high frequency induction heating is provided. The chamber 12 has a structure that can maintain a vacuum state in both the state where the shaft 17 is inserted into the chamber 12 and the state where the shaft 17 is pulled up. A press table 20 that supports pressure is disposed below the cartridge, and the press table 20 is coupled to a press table moving mechanism that moves the press table 20 up and down via a press table shaft 21. After the sintering, the press stand 20 is moved upward to take out the sintered body from the upper part of the chamber 12.

  However, in this embodiment, as shown in FIG. 4, the sintering furnace 2 includes a preliminary chamber 31 for storing the cartridge 11 before sintering, a cooling chamber 32 for storing and cooling the cartridge after sintering, The mounting chamber 33 includes eight cartridge storage portions 34a to 34h for storing the cartridges before and after sintering, and the cartridge storage portions for the cartridges before sintering. A cartridge storage unit that moves from the carry-out position from the preliminary chamber 31 to the carry-in position to the sintering chamber 13 and moves from the carry-out position of the sintered cartridge from the sintering chamber 13 to the carry-in position to the cooling chamber 32. A moving mechanism is provided. As shown in FIG. 4, the mounting chamber 33 is disposed above the sintering chamber 13, the spare chamber 31 is disposed above the mounting chamber 33, and the cooling chamber 32 is disposed below the mounting chamber 33. . The cartridge storage portion moving mechanism is a rotation mechanism, and eight cartridge storage portions 34 a to 34 h are arranged with respect to the rotation shaft 36 of the rotation motor 35. FIG. 5 is a top view showing the arrangement of the cartridge storage portion. 4 and 5 show a case where the cartridge 11 is stored in the cartridge storage portion 34a at the position where the cartridge 11 is unloaded from the preliminary chamber 31. FIG.

  The chamber 12, the mounting chamber 33, the preliminary chamber 31, and the cooling chamber 32 are connected to a vacuum pump, and can be evacuated independently by opening and closing a vacuum valve between the chamber 12 and the vacuum chamber. Is set. A shutter 26 is provided between the preliminary chamber 31 and the mounting chamber 33, a shutter 27 is provided between the mounting chamber 33 and the chamber 12, and a shutter 28 is provided between the mounting chamber 33 and the cooling chamber 32. Is a shutter that can be opened and closed while maintaining the vacuum state of each room.

  Next, a case where the sintering operation is continuously performed by the continuous discharge plasma sintering apparatus of the present embodiment will be described. First, the cartridge 11 a containing the powder raw material is set in the external holder 38 provided on the preliminary chamber 31, the shutter 25 provided on the upper portion of the preliminary chamber 31 is opened, and the cartridge 11 a is inserted into the internal holder 39 of the preliminary chamber 31. Move in. Next, the preliminary chamber 31 is evacuated to the same degree as the degree of vacuum of the mounting chamber 31, the shutter 26 is opened with the mounting chamber 31, and the cartridge 11 a is stored in the cartridge in the mounting chamber 33 directly below the internal holder 39. It moves to the part 34a and closes the shutter 26 between the mounting chambers 31. FIG. 3 shows the state at this time.

  Next, the rotation motor 35 of the cartridge storage unit moving mechanism is rotated 180 degrees so that the cartridge storage unit 34e is located at a position symmetrical to the rotation axis 37 and is carried into the sintering chamber 13. Move to the desired position. Thereafter, the shutter 27 between the mounting chamber 33 and the chamber 12 is opened, the press table 20 is moved upward, the cartridge 11a is placed on the press table 20, and the cartridge is placed at a predetermined position where the incineration chamber 13 is sintered. The press table 20 is moved downward so that 11a is arranged. Next, the shaft 17 is lowered from above and inserted into the incineration chamber 13 through the cartridge housing portion 34a, and a predetermined pressure is applied to the powder raw material between the upper and lower punches of the cartridge 11a. Simultaneously with this operation, the shutter 26 between the preliminary chamber 31 is opened, and the cartridge 11b containing the next raw material is moved to the cartridge storage portion in the mounting chamber 33.

  FIG. 6 is a schematic cross-sectional view showing the outline of the sintering furnace in a state where the cartridge containing the next raw material is moved to the preliminary chamber simultaneously with the sintering operation as described above. Also in this example, if the configuration and shape of the sintering chamber 13, the chamber 12, and the cartridge are set in the same manner as in Example 1, introduction of Ar gas and pressure setting during sintering, setting of conditions for high-frequency induction heating, It is possible to perform sintering by setting all the conditions such as the pressure and electric current of the discharge plasma sintering to the same conditions as in the first embodiment.

  After the completion of sintering, the shaft 17 is raised and the press table 20 is raised to store the sintered cartridge 11a in the original cartridge storage portion 34a in the mounting chamber 33. Next, the rotation of the rotation motor 35 of the cartridge storage unit moving mechanism is rotated 180 degrees so that the cartridge storage unit 34a storing the sintered cartridge 11a is located symmetrically with respect to the rotation shaft 37 from the unloading position from the sintering chamber 13 Then, it moves to the carry-in position to the cooling chamber 32 disposed below the mounting chamber 33. At this time, the cartridge 11b containing the next raw material moves to the carrying-in position to the sintering chamber 13 at the same time. Thereafter, the shutter 28 between the cooling chamber 32 and the mounting chamber 33 evacuated to the same degree as the mounting chamber 33 is opened, the sintered cartridge 11a is carried into the cooling chamber 32, and the shutter 28 is closed. Next, the shutter 26 between the preparatory chamber 31 and the mounting chamber 33 evacuated to the same degree as the degree of vacuum of the mounting chamber 33 is opened, and the cartridge 11c containing the next raw material is placed in the mounting chamber 31 directly below the same. And the shutter 26 between the mounting chamber 33 is closed. FIG. 7 is a schematic cross-sectional view showing an outline of the sintering furnace in a state where the next cartridge is moved onto the sintering chamber after the sintering operation is completed as described above. Thereafter, the cartridge 11b is carried into the sintering chamber 13 and sintered by the above-described sintering operation similar to that of the cartridge 11a. The cartridge in the cooling chamber 32 is cooled for a predetermined time, and then the shutter 29 under the cooling chamber 32 is opened and carried into the collection box 37.

  In the continuous discharge plasma sintering apparatus of the present embodiment, by repeating the above operation, the cartridge after sintering is cooled, the next cartridge is sintered, and a new cartridge is carried into the preliminary chamber. This makes it possible to significantly reduce the time required for continuous sintering operations.

  In the present embodiment, all of the eight cartridge storage portions 34a to 34h can be used effectively. The spare chamber 31 is set to store eight cartridges, and when the shutter 26 between the mounting chamber 33 is opened, the cartridges are sequentially stored in the cartridge storage portions while rotating the cartridge storage portions 34a to 34h. Thus, the cartridge containing eight raw materials is stored in the cartridge storage section. Next, one is placed at a predetermined position in the sintering chamber 13 to perform a sintering operation, and after the sintering, it is returned to the original cartridge storage portion and stored. Next, the rotation motor 35 of the cartridge storage unit moving mechanism is rotated by 1/8, and the next cartridge is put into the sintering chamber 13 and sintered. By repeating this sequentially, the sintering of the eight cartridges is completed, and then the shutter 28 between the cooling chamber 32 is opened and the eight cartridges are carried into the cooling chamber 32. Through such a process, the eight cartridges can be carried into the mounting chamber 33 and carried out into the cooling chamber 32 by opening and closing the shutter once, and the work efficiency can be further improved. Alternatively, the cartridges may be stored in all of the eight cartridge storage units, and the cartridges may be loaded into the mounting chamber 33 and discharged into the cooling chamber 32 one by one for each sintering.

  In this embodiment, the external holder 38, the spare chamber 31 and the internal holder 39 of the cooling chamber 32 can be constituted by a cylindrical case or the like, and the downward movement of the cartridge within the holder can be performed manually or electrically. It can be performed using a mechanism or the like. The movement of the cartridge from the spare chamber 31 into the mounting chamber 33 and the movement of the cartridge from the mounting chamber 33 into the cooling chamber 32 can be similarly performed using a manual or electric moving mechanism.

Next, the case where Mg ₂ Si (magnesium silicide) is sintered using the continuous discharge plasma sintering apparatus of the present embodiment will be described in detail. The forming die has an outer diameter of 50 mm, an inner diameter of 22 mm, and a height of 60 mm. The upper and lower punches each had an outer diameter of 22 mm and a height of 35 mm, and were made of a carbon material.

  It is difficult to charge the powder raw material, and it may be crushed in the lateral direction at the time of molding and clogged in the molding die. Therefore, 3 g of powdered Mg and Si are weighed at a predetermined ratio, and this powder raw material is graphite. Prepare raw material pellets that have been pre-pressed to form a shape with an outer diameter of 21 mm and a thickness of about 7 mm when covered with a sheet, fill the space between the upper and lower punches in the molding die, configure the cartridge, and sinter with this device went.

First, the first cartridge filled with the raw material pellets is set in the sintering furnace 2 of the main sintering apparatus, evacuated to 1 Pa or less with a vacuum pump, and then replaced with Ar gas. In a state of flowing Ar gas at 5 l / min, pressurization was performed with a servo press, and the compression pressure was maintained at 20 MPa / cm ² . In this state, a high frequency induction heating power source was turned on and heated at 4 KW for 30 seconds to raise the temperature to 450 ° C. Thereafter, the output of the high frequency induction heating power supply is set to 3 kW, and the pulse energization of the discharge plasma sintering is raised to 850 ° C. by repeating the ON state with a current of 800 A and a pulse width of 150 msec and the OFF state of a current of 0 A and a pulse width of 10 msec. Held for 3 minutes. Thereafter, the pressure was released and the power supply was turned off to finish the first sintering.

  Next, the shaft 17 is removed from the sintering chamber 13, the press table 20 is moved, the sintered cartridge is returned to the cartridge storage section in the mounting chamber 33, the cartridge storage section moving mechanism is rotated, and the raw material pellets are sandwiched. The next cartridge was inserted into the sintering chamber 13. This was repeated and the eight cartridges housed in the mounting chamber were sintered under the same conditions.

  By the above continuous sintering operation, eight sintered bodies having an outer diameter of 20 mm and a height of 5 mm were obtained, and the density of all the obtained eight sintered bodies was 96% or more.

(Modification)
FIG. 8 is a schematic plan view showing an outline of a modification of the sintering furnace of the continuous discharge plasma sintering apparatus according to Embodiment 2 of the present invention. The sintering furnace 3 shown in FIG. 8 has the same configuration as the sintering furnace 2 shown in FIG. 4 such as the chamber and the sintering chamber, but is equipped with a mounting chamber, a spare chamber, a cooling chamber, and a cartridge storage unit moving mechanism. The number of cartridge storage units is different. In FIG. 7, a preliminary chamber 51 and a cooling chamber 52 are arranged on both sides of the chamber 50, and a mounting chamber 53 having a shape that covers the carry-in ports of both cartridges is arranged. Although the mounting chamber 53 is disposed above the chamber 50, the preliminary chamber 51 and the cooling chamber 52 may be disposed either above or below the mounting chamber 53. The cartridge storage portion moving mechanism 55 that holds the two cartridge storage portions 54a and 54b moves in parallel in the horizontal direction, and when the cartridge storage portion 54a is at the outlet of the cartridge from the spare chamber 51, the cartridge storage portion 54b is in the sintering chamber. When the cartridge storage portion 54a is moved to the entrance to the sintering chamber, the cartridge storage portion 54b is set to be positioned at the entrance to the cooling chamber 52.

  The cartridge containing the raw material is carried from the spare chamber 51 to the cartridge housing portion 54a, and at the same time, the sintered cartridge is carried from the sintering chamber to the cartridge housing portion 54b, and then the cartridge housing portion moving mechanism 55 is moved to the left. The cartridge after sintering is carried into the cooling chamber, and a new cartridge is carried into the sintering chamber. Thereafter, the shaft of the servo press is lowered through the cartridge housing portion 54a and inserted into the sintering chamber to perform the sintering operation. After the sintering, the shaft is raised, the cartridge accommodating portion moving mechanism 55 is moved to the right to return to the arrangement shown in FIG. 8, and the sintered cartridge is carried out and a new cartridge is carried in as described above. Continuous sintering can be performed by repeating the above operations.

  Needless to say, the present invention is not limited to the above-described embodiments, and can be changed according to the type and shape of the intended sintered body. For example, as the heat insulating material constituting the sintering chamber, a molded heat insulating material such as glass fiber, alumina felt, zirconia felt or the like can be used in addition to the carbon felt. The structure, shape, material, and the like of each part of the sintering apparatus can be changed according to the type and shape of the target sintered body. Further, it is desirable to optimize the sintering conditions such as the temperature depending on the kind of the sintered body and the structure and shape of each part of the sintering apparatus to be used.

1, 2 Sintering furnace 11, 11a, 11b, 11c Cartridge 12, 50 Chamber 13 Sintering chamber 16 Servo press 17 Shaft 18 Vacuum pump 19 Induction heating coil 20 Press stand 21 Press stand shaft 22 Press stand moving mechanism 23 Lower end portion of shaft 24 Press stand upper end portion 25, 26, 27, 28 Shutter 31, 51 Preliminary chamber 32, 52 Cooling chamber 33, 53 Mounting chamber 34a-34h, 54a, 54b Cartridge storage unit 35 Motor 36 Rotating shaft 37 Collection box 38 External holder 39 Inner holders 41 and 46 Molding die 42 Upper punch 43 Lower punch 44 Powder raw material 45 Insulating layer 55 Cartridge housing part moving mechanism

Claims (9)

  A chamber and a cylindrical sintering chamber constituted by a heat insulating material installed in the chamber are provided, and a cartridge comprising a molding die and an upper punch and a lower punch inserted in the molding die is disposed in the sintering chamber. And a discharge plasma sintering means for compressing the raw material in the forming die using the upper and lower punches and passing a pulsed current between the upper and lower punches to sinter, and on the outside of the sintering chamber. A discharge plasma sintering apparatus comprising: a means for high-frequency induction heating the forming die or the raw material.   2. The discharge plasma sintering apparatus according to claim 1, wherein the forming die has a layered portion made of an insulator or a high-resistance material at a central portion in a vertical direction.   A press apparatus having a press shaft that presses an upper punch or a lower punch of the cartridge mounted in the sintering chamber is installed above or below the sintering chamber, and faces the press shaft across the cartridge. A press stand for holding the lower punch or the upper punch of the cartridge is installed below or above the sintering chamber, and a portion in contact with the upper punch or the lower punch at the tip of the press shaft and the lower punch or the upper punch of the press stand; The discharge plasma sintering apparatus according to claim 1 or 2, wherein the material of the contacting portion is carbon.   A chamber and a cylindrical sintering chamber constituted by a heat insulating material installed in the chamber are provided, and a cartridge comprising a molding die and an upper punch and a lower punch inserted in the molding die is disposed in the sintering chamber. And a discharge plasma sintering means for compressing the raw material in the forming die using the upper and lower punches and passing a pulsed current between the upper and lower punches to sinter, and on the outside of the sintering chamber. Means for high-frequency induction heating of the forming die or the raw material, and includes a preliminary chamber for storing a cartridge before sintering, a cooling chamber for storing and cooling the cartridge after sintering, and at least one mounting chamber. The mounting chamber includes at least two cartridge storage portions for storing the pre-sintered and post-sintered cartridges, and the cartridge storage portion is used as the spare for the cartridge before the sintering. Cartridge storage part moving mechanism for moving from the unloading position to the sintering chamber from the unloading position or the cartridge housing for moving the sintered cartridge from the unloading position from the sintering chamber to the unloading position to the cooling chamber The chamber, the mounting chamber, the spare chamber, and the cooling chamber can be evacuated independently, and the mounting chamber is provided between the spare chamber and the mounting chamber. A continuous discharge plasma sintering apparatus comprising a shutter that can be opened and closed while maintaining a vacuum state between the chamber and the chamber, and between the mounting chamber and the cooling chamber.   5. The continuous discharge plasma sintering apparatus according to claim 4, wherein the forming die has a layered portion made of an insulator or a high-resistance material at a central portion in a vertical direction.   One mounting chamber, and the mounting chamber moves the cartridge housing portion from the unloading position of the pre-sintering cartridge from the preliminary chamber to the loading position of the sintering chamber; and A press that presses the upper punch of the cartridge mounted in the sintering chamber, and includes a cartridge storage unit moving mechanism that moves the cartridge after sintering from a position where the cartridge is unloaded from the sintering chamber to a position where it is loaded into the cooling chamber. A press apparatus having a shaft is installed above the sintering chamber, and a press stand for holding a lower punch of the cartridge is installed below the sintering chamber, and the press stand is attached to the sintering chamber by control. 6. The continuous discharge plasma sintering apparatus according to claim 4, further comprising a press table moving mechanism capable of moving the cartridge between chambers.   The mounting chamber is disposed above the sintering chamber, the preliminary chamber is disposed above the mounting chamber, and the cooling chamber is disposed below the mounting chamber. The continuous discharge plasma sintering apparatus as described.   8. The continuous discharge plasma sintering according to claim 7, wherein the cartridge housing part moving mechanism is a rotating mechanism, and the at least two cartridge housing parts are arranged on a rotating shaft of the rotating mechanism. Bonding device.   The continuous discharge plasma sintering apparatus according to claim 8, wherein the mounting chamber includes at least four cartridge storage units.

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