JP4168356B2 - Sintering equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sintering apparatus that sinters ceramics and conductive raw material powder filled in a sintering mold by energization.
[0002]
[Prior art]
A raw material powder of a conductive object such as ceramics, metal, carbide, or nitride is filled in a sintering mold, heated, and pressed with a pair of opposing punches to produce a sintered body. Sintering apparatuses for manufacturing this sintered body are classified into several systems depending on the heating system. In the indirect heating method using a heater, a heater such as a resistance heater is disposed around the sintering mold, the sintering mold is heated from the surface, and the raw material powder therein is indirectly heated. This method is applicable to the sintering of both ceramics and conductive materials and is widely used.
[0003]
The induction heating method is a heating method in which the sintered mold is directly heated by electromagnetic induction. Therefore, the heating rate of the sintered body is faster than that of the resistance heating method. The energization method is a method in which an electrode and a punch are directly energized and heated. The energization method is disclosed in Japanese Patent Laid-Open Nos. 64-55303, 5-70804, and 5-117707.
[0004]
FIG. 6 shows a conventional example in which a punch is the main heating element in the energization method. Hereinafter, the hook punch is referred to as a punch heating element. As shown in this figure, in the conventional energization type sintering apparatus, the raw material powder 3 is put into the sintering mold 1 and the electrodes 5a and 5b are pressurized 6 through the punch heating elements 4a and 4b, so that the punch is mainly used. The raw material powder 3 is heated and sintered by the heat generated by the heating elements 4a and 4b. In this case, the punch heating elements 4a and 4b are made of a heating element (a substance having a large electrical resistance) that generates heat when energized, and heat is transferred from the heated punch heating elements 4a and 4b to the raw material powder 3 to heat it.
[0005]
[Problems to be solved by the invention]
However, the conventional sintering apparatus using the punch heating element described above has the following problems.
1. In the case of a peeled material (solid, solid) having no defect in the cross section of the hole, when the diameter of the raw material powder 3 is increased, the resistance of the heating element (punch heating elements 4a and 4b) is decreased in inverse proportion to the sectional area. Therefore, the punch heating elements 4a and 4b need to be lengthened in order to maintain the same electric resistance (the wrinkle resistance is inversely proportional to the cross-sectional area).
For example, when the diameters of the punch heating elements 4a and 4b are doubled, the cross-sectional area is quadrupled, and when the thickness of the raw material powder 3 is the same, the volume of the raw material powder 3 is quadrupled. Therefore, in order to obtain the same calorific value (electric resistance) per unit volume of the raw material powder 3, the length of the punch heat generating elements 4a and 4b needs to be 16 times (4 × 4 = 16) as shown in FIG. . For this reason, the punch heating elements 4a, 4b are likely to be misaligned, and if the parallelism of the upper and lower surfaces is not good, the pressurization to the raw material powder 3 is likely to be unstable and unevenly biased to one side, In some cases, the punch heating elements 4a and 4b may be damaged.
[0006]
2. Further, as shown in FIG. 7, when the punch heating elements 4 a and 4 b become longer, it becomes difficult to transfer heat to the raw material powder 3. In addition, heat loss increases.
3. Even if the sintering space 2 and the raw material powder 3 become large, if the solid punch heating elements 4a and 4b remain small, a thick spacer is provided between the punch heating elements 4a and 4b and the raw material powder 3 as shown in FIG. 11 must be inserted so that the pressure 6 is evenly applied to the raw material powder 3 through the punch heating elements 4a and 4b.
However, since the punch heating elements 4a and 4b are not in direct contact with the raw material powder 3 and the thick spacer 11 is inserted in the middle, the heat loss is large and the heat transfer efficiency is poor. Moreover, the raw material powder 3 is unlikely to have a uniform temperature.
[0007]
The present invention has been developed to solve the above-described problems. That is, the object of the present invention is to increase the outer shape of the punch heating element and to keep the height low even if the cross-sectional area of the raw material powder is increased, thereby enabling stable operation. It is in providing a tying device.
[0008]
[Means for Solving the Problems]
According to the present invention, there is provided a sintering apparatus that pressurizes and energizes a pair of punch heating elements and electrodes arranged to face each other and the raw material powder filled in a sintering space of a sintering mold, In the sintering apparatus, wherein the punch heating element is composed of a conductor that generates heat when energized between electrodes, the punch heating element has at least one hole extending in the pressing direction. Provided. According to the configuration of the present invention, since the punch heating element has at least one hole extending in the pressing direction , the cross-sectional area is reduced by the amount of the missing portion of the cross section due to the cavity, and the electrical resistance is increased accordingly. The amount of heat generated by resistance increases and can be heated effectively.
[0009]
In addition, the resistance heating value can be increased uniformly by reducing the cross-sectional area uniformly over the entire length of the hole. The number of holes is preferably plural, but may be one.
[0010]
In addition, according to the present invention, there is provided a sintering apparatus in which the raw material powder filled in the sintering space of the sintering mold is pressed by a pair of punch heating elements and electrodes arranged opposite to each other and energized and sintered. In the sintering apparatus, the punch heating element is composed of a conductor that generates heat when energized between the electrodes, and the punch heating element is composed of a plurality of flat plates stacked on each other, and each flat plate has a through hole. There is provided a sintering apparatus characterized by comprising: With this configuration, since the electrical contact resistance is increased on the laminated surface of the flat plates, the heat generation amount can be increased even if the outer dimensions are the same.
[0011]
Furthermore, each through hole of the flat plate is provided at a position different from the through-hole of the adjacent flat, it is preferable. With this configuration, since the hole position is shifted, the current path is increased, the resistance is increased, and the heat generation amount can be further increased.
[0012]
In addition, according to the present invention, there is provided a sintering apparatus in which the raw material powder filled in the sintering space of the sintering mold is pressed by a pair of punch heating elements and electrodes arranged opposite to each other and energized and sintered. Te, the punch heating element in the sintering apparatus is composed of a conductive material which generates heat by energization between the electrodes, the punch heating element, characterized by having a large number of closed cells provided in foamed A sintering apparatus is provided. With this configuration, the cross-sectional area is reduced and the current path is increased due to a large number of closed cells, so that the heat generation amount can be increased and the raw material powder can be heated effectively.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.
[0014]
FIG. 1 is a configuration diagram showing a first embodiment of a sintering apparatus of the present invention. The sintering die 1 is formed in a hollow cylindrical shape, and an inner center is a sintering space 2 filled with the raw material powder 3. Punch heating elements 4a and 4b configured in a cylindrical shape are slidably fitted on the upper and lower sides of the sintering die 1. Electrodes 5a and 5b are provided above and below the punch heating elements 4a and 4b. The electrodes 5a and 5b press the punch heating elements 4a and 4b and energize the punch heating elements 4a and 4b. The heating die side of the sintered mold 1, punch heating elements 4a and 4b, and electrodes 5a and 5b is surrounded by a heat insulating wall 7 to maintain heat insulation.
[0015]
A hydraulic device (not shown) is connected to the upper and lower ends of the electrodes 5a and 5b so as to pressurize the punch heating elements 4a and 4b. The power source 8 uses a commercial power source such as 50 or 60 Hz. The electric power from the power source 8 is controlled by a thyristor and stepped down by a transformer, and then the electrodes 5a and 5b are energized. A temperature sensor 10 is provided on the inner surface or outer surface of the sintering mold 1 and measures the temperature of the sintered body. The control unit 9 controls the current by controlling the thyristor based on the measurement value of the temperature sensor 10. In the above description, both the upper and lower electrodes 5a and 5b and the punch heating elements 4a and 4b are pressed from above and below with a hydraulic device. However, only one of the upper and lower electrodes 5 and the punch heating element 4 is pressed. May be fixed. The above description can be similarly applied to other embodiments described below.
[0016]
As described above, in the sintering apparatus of the present invention, the raw material powder 3 is put into the sintering mold 1, the electrodes 5a and 5b are pressurized 6 through the punch heating elements 4a and 4b, and the punch heating element 4a, The raw material powder 3 is heated and sintered by the heat generated by 4b. In this case, the punch heating elements 4a and 4b are made of a heating element (a substance having a large electrical resistance) that generates heat when energized, and heat is conducted from the punch heating elements 4a and 4b to the raw material powder 3 to heat the raw material powder 3.
[0017]
2 is a configuration diagram of the punch heating element of FIG. 1, (A) is a plan view seen from directly above, and (B) is a perspective view. FIG. 3 is a configuration diagram similar to FIG. 2 of the punch heating element showing the second embodiment of the present invention, and FIG. 4 is a configuration diagram similar to the third embodiment. Furthermore, FIG. 5 is a block diagram of the punch heating element of the fourth embodiment of the present invention.
[0018]
As shown in FIGS. 2 to 4, the outer shapes of the punch heating elements 4 a and 4 b are the same as the inner diameter of the sintering mold 1 (the outer diameter of the raw material powder 3), and at least one cavity 12 is provided in the punch heating elements 4 a and 4 b. Provide. That is, in the example of FIGS. 2 to 4, a hole is made in the punch heating elements 4a and 4b to reduce the cross-sectional area. It is better to make many small holes evenly distributed than to make a few large holes.
[0019]
In FIG. 2, the whole is a single body, and a hole passes from one end to the other end. When the cross-sectional area of the hole is small and the cross-sectional area is constant, the electrical resistance increases and the resistance heat generation amount increases as compared with the case where there is no hole. In FIG. 2B, the upper side is the electrode 5a side, the lower side is the raw material powder side, and the raw material powder side has no holes so that the raw material powder 3 does not leak. Although this figure shows the punch heating element 4a, the punch heating element 4b has a shape opposite to that of 4a.
[0020]
FIG. 3 shows a case where the integrated body of FIG. This example shows a punch heating element 4a, and the punch heating element 4b is the opposite. In FIG. 3B, the upper side is the electrode 5a side, and the lower side is the raw material powder side.
3 increases the electrical contact resistance between the respective layer plates, so that the same outer diameter, the same length, and the same cross-sectional defect rate as those in the case of the single unit shown in FIG. The total electrical resistance is further increased, and the resistance heating value is correspondingly increased. It should be noted that the raw material powder 3 side of the punch heating elements 4a and 4b has no holes so that the raw material powder 3 does not spill, and is in a “peeled” state.
[0021]
FIG. 4 shows a case where the holes of the upper and lower layer plates in FIG. 3 are shifted. Other configurations are the same as those in the example of FIG. In this case, at the boundary between each layer, the current flowing through the bulk of the layer (the part that is not a hole) flows into the next layer, so the bulk part of the next layer is not completely underneath, Since it is necessary to flow in the direction perpendicular to the axial direction of the electrodes 5a and 5b and then to the bulk portion of the next layer, the current path increases and resistance (heat generation) increases, or the boundary area decreases and resistance (heat generation) ) And the raw material powder 3 can be heated more effectively.
[0022]
In FIG. 5, the cavity 12 of the punch heating element is a large number of closed cells provided in a foam shape. That is, in this example, since the entire punch heating elements 4a and 4b are in the form of foam, the resistance (heat generation) increases due to the reduction in the cross-sectional area from the bulk, and the path length increases due to the current path not being straight. The raw material powder 3 can be heated more effectively by increasing the resistance (heat generation).
[0023]
In any case, when the cavities 12, that is, the holes or the bubbles are made fine and uniformly distributed and pressed through the electrodes 5a and 5b, the raw material powder 3 is uniformly pressed over the entire cross section. Be loaded.
[0024]
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0025]
【The invention's effect】
With the configuration described above, in the present invention, if the holes are provided as shown in FIG. 2 and the cross-sectional area is the same as the initial one, the punch heating elements 4a and 4b can be obtained even if the diameters of the punch heating elements 4a and 4b are doubled. The length may be 4 times, which can be significantly shorter than the conventional 16 times, and the conventional problems are eliminated.
Further, when the cross-sectional area and the cross-sectional area of the hole are small and the length is constant, the electric resistance is increased and the resistance heating value is increased as compared with the case where there is no hole, and heating can be effectively performed.
[0026]
In addition, when the monolithic structure is a multilayer board laminated structure, the electrical contact resistance increases between each laminar board, so the same outer diameter, the same length, and the same cross-sectional defect rate than the monolithic one in FIG. Even if there is, the total electric resistance is further increased, and the resistance heating value is also increased correspondingly. On the contrary, in order to obtain the same electric resistance (heat generation amount), the lengths of the punch heating elements 4a and 4b can be shortened compared to the case of FIG.
[0027]
In addition, by shifting the holes in the upper and lower layer plates, the current flowing through the bulk (non-hole portion) of a certain layer at the boundary between each layer flows into the next layer immediately below the next layer. Since there is no complete bulk portion, it is necessary to flow in the direction perpendicular to the axial direction of the electrodes 5a and 5b and then to the bulk portion of the next layer, so the current path increases and resistance (heat generation) increases, The area is reduced, the resistance (heat generation) is increased, and the raw material powder 3 can be heated more effectively.
Further, by making the punch heating elements 4a and 4b into a foam shape, the resistance (heat generation) increases due to the reduction of the cross-sectional area from the bulk, and the resistance (heat generation) due to the increase in the path length due to the non-straight current path. The raw material powder 3 can be heated more effectively due to the increase in.
[0028]
In any case, when the holes or bubbles are made fine and distributed uniformly throughout and pressurized 6 through the electrodes 5a and 5b, the raw material powder 3 is uniformly pressed over the entire cross section.
Furthermore, in the configuration of the present invention, since the punch heating elements 4a and 4b are in direct contact with the raw material powder 3 without the spacer 11, the heat loss is small and the temperature is uniform.
[0029]
As described above, the sintering apparatus of the present invention can increase the outer shape of the punch heating element and keep the height low, even if the cross-sectional area of the raw material powder is increased, thereby stabilizing. It has excellent effects such as being able to operate.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a sintering apparatus of the present invention.
FIG. 2 is a configuration diagram of the punch heating element of FIG. 1;
FIG. 3 is a configuration diagram of a punch heating element according to a second embodiment of the present invention.
FIG. 4 is a configuration diagram of a punch heating element according to a third embodiment of the present invention.
FIG. 5 is a configuration diagram of a punch heating element according to a fourth embodiment of the present invention.
FIG. 6 is a configuration diagram of a conventional sintering apparatus.
FIG. 7 is another configuration diagram of a conventional sintering apparatus.
FIG. 8 is still another configuration diagram of a conventional sintering apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sintering mold 2 Sintering space 3 Raw material powder 4a, 4b Punch heating element 5a, 5b Electrode 6 Pressurization 7 Heat insulation wall 8 Power supply 9 Control part 10 Temperature sensor 11 Spacer 12 Cavity (hole, bubble)

Claims (4)

A sintering device that pressurizes and energizes a pair of punch heating elements and electrodes facing raw powder filled in a sintering space of a sintering mold, and the punch heating element includes: A sintering apparatus comprising a conductor that generates heat when energized between electrodes, wherein the punch heating element has at least one hole extending in a pressurizing direction . A sintering device that pressurizes and energizes a pair of punch heating elements and electrodes facing raw powder filled in a sintering space of a sintering mold, and the punch heating element includes: In the sintering apparatus composed of a conductor that generates heat by energization between the electrodes, the punch heating element is composed of a plurality of flat plates stacked on each other, and each flat plate has a through hole penetrating in the pressurizing direction . A sintering apparatus characterized by that. Sintering apparatus of claim 2, each of the through holes of the flat plate is provided in different and the through hole of the adjacent flat position, it is characterized. A sintering device that pressurizes and energizes a pair of punch heating elements and electrodes facing raw powder filled in a sintering space of a sintering mold, and the punch heating element includes: in the sintering apparatus is composed of a conductive material which generates heat by energization between the electrodes, the punch heating element, sintering apparatus characterized by having a large number of closed cells provided in foamed.

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