JPH0839300A - Hot press method and hot press device - Google Patents

Abstract

PURPOSE:To prevent generation of a temp. difference in the surface layer part and central part of a sample so as to shorten soaking time and to assure quality. CONSTITUTION:Press rams 17, 18 are heated by heaters 20, 20 which are heating means within press ram chambers 14, 15 to heat the sample 16 by heat conduction from the press rams. The sample is heated from its circumference by a heater 28 which is another heating means within a sample chamber 13, by which the heat radiation to the circumference from the sample is compensated. A soaking block 19 as a soaking means having high heat conductivity in a radial direction as compared with the heat conductivity in an axial direction is interposed between the front ends of the press rams and the sample. Plural sheets of soaking plates 27 are laminated and are used as the soaking block 19. Heaters of an electric resistance heating system and heating coils of an induction heating system are usable as the heating means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot pressing method and a hot pressing apparatus for heating and pressing a sample.

[0002]

2. Description of the Related Art As is well known, hot pressing is widely applied to, for example, sintering, diffusion bonding and hot forming of ceramic materials, metal materials or composite materials thereof. FIG. 4 shows an outline of a conventional general hot press apparatus. In the figure, reference numeral 1 is a frame, 2 is a vacuum container, 3 is a heating chamber formed by a heat insulating wall, 4 is a heater, and 5 and 6 are a pair of upper and lower. The press ram 7 is a pressing cylinder, and the sample 8 is sandwiched between the press rams 5 and 6, and the sample 8 is heated to a desired temperature by the heater 4 in a vacuum state in the heating chamber 3 or in a gas atmosphere. Meanwhile, the pressing cylinder 7 is operated to press the sample 8 between the press rams 5 and 6 to perform hot pressing such as sintering or molding.

[0003]

By the way, in the above-mentioned conventional hot pressing apparatus, the sample 8 is heated by the heater 4 arranged around the sample 8 by radiation or convection of atmospheric gas. Although the surface layer of No. 8 is heated quickly, the temperature rise in the central part is delayed compared to that of the surface layer, and the sample 8 also radiates heat due to heat conduction through the press rams 5 and 6. In the process, it is unavoidable that a temperature difference occurs between the surface layer portion and the central portion of the sample 8.

When there is a temperature difference in the axial direction of the sample 8, it does not matter so much, but as described above, the hot pressing is performed while the temperature difference is generated between the surface layer portion and the central portion of the sample 8. Since the quality may be adversely affected by performing the heat treatment, it is necessary to secure a sufficient soaking time until the entire sample 8 becomes almost isothermal in the past, and accordingly, it takes a long time for the whole treatment. Met. Further, once a large temperature difference occurs between the surface layer portion and the central portion, it is difficult to reach a perfect thermal equilibrium state even if a sufficient soaking time is taken, and a temperature difference may remain to some extent. there were.

The present invention has been made in view of the above circumstances. An object of the present invention is to prevent a temperature difference between the surface layer portion and the central portion of the sample when the temperature of the sample is raised. It is to provide an effective means capable of shortening processing time and ensuring quality.

[0006]

In the hot pressing method of the present invention, a sample is heated and pressed by a pair of press rams. The press ram is heated and the sample is heated by heat conduction from the press ram. Is characterized by. In this case, it is preferable to heat the sample from its surroundings to compensate for heat dissipation from the sample to the surroundings.
Further, a heat equalizing means having a higher radial heat conductivity than the axial heat conductivity is interposed between the tip of the press ram and the sample, and the sample is heated and pressed by the press ram through the heat equalizing means. It is more preferable to use a soaking block formed by laminating a plurality of soaking plates.

Further, the hot press device of the present invention has a structure in which the sample is heated in the heating chamber and pressed by a pair of press rams, and the inside of the heating chamber is a sample chamber in which the sample is arranged by a heat insulating wall. And two press ram chambers in which the respective press rams are respectively arranged, and the tip end of each press ram is inserted into the sample chamber through the heat insulating wall and the part of the press ram located in the press ram chamber is heated. Thus, a heating means for heating the sample by heat conduction from the press ram is provided. In this case, it is preferable to provide a heating means for heating the sample from its surroundings to compensate for heat radiation from the sample to the surroundings. Further, it is more preferable that the heat equalizing means, which has a higher heat conductivity in the radial direction than the heat conductivity in the axial direction, can be interposed between each of the press rams and the sample. Further, it is conceivable that the heating means is composed of an electric resistance heating type heater provided inside the heating chamber, or an induction heating type heating coil provided outside the heating chamber.

[0008]

The hot pressing method of the present invention does not directly heat the sample from its surroundings by the heater, but indirectly heats the sample by heating the press ram and conducting heat from the press ram. By doing so, the sample is heated from the pressing surface side by both press rams, and a large temperature difference between the surface layer portion and the central portion does not occur unlike the conventional case. Then, when heat radiation to the surroundings of the sample is a problem, the heat radiation is compensated by supplementarily heating the sample from the surroundings. Further, by providing the heat equalizing means between the press ram and the sample, the heat transfer in the radial direction of the sample is made higher than the heat transfer in the axial direction, and the uniform heat distribution in the radial direction of the sample is further improved. The heat equalizing block preferably used as the heat equalizing means has a plurality of heat equalizing plates that are laminated to generate thermal resistance in the axial direction on the laminated surface, which causes the axial thermal conductivity to increase in the radial direction. It has a thermal anisotropy that naturally decreases as compared with.

Further, in the hot press apparatus of the present invention, the press ram is heated by the heating means in the press ram chamber which is insulated from the sample chamber, and the sample in the sample chamber is indirectly heated by heat conduction from the press ram. . Then, if necessary, the sample is supplementarily heated by the heating means to compensate for the heat radiation to the surroundings, and the heat equalizing means is interposed between the press ram and the sample to improve the heat transfer in the radial direction. To do. As a heating means, an electric resistance heating type heater, an induction heating type heating coil or the like can be appropriately adopted.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a hot pressing apparatus according to this embodiment, in which reference numeral 11 is a heating chamber. The heating chamber 11 is arranged inside a frame similar to the frame 1 in the conventional hot pressing apparatus shown in FIG. 4, but the frame is not shown in FIG.

The heating chamber 11 is entirely formed of a heat insulating material, and the inside of the heating chamber 11 is provided with a sample chamber 13 located at the center by heat insulating walls 12 and press ram chambers 14 and 15 connected to the upper and lower sides thereof. It is divided into Then, the sample 16 which is the object to be processed is placed in the sample chamber 13, and the press rams 17 and 18 are placed in the press ram chambers 14 and 15, respectively, and the tips of the press rams 17 and 18 have heat insulating walls 12 and 12, respectively. And is inserted into the sample chamber 13 through the sample ram 17, and at the tips of the press rams 17 and 18 through the heat equalizing blocks 19 and 19 (heat equalizing means, details will be described later).
The sample 16 is sandwiched, and a pressing cylinder (not shown) attached to the frame is operated to press the upper press ram 17, so that the sample 16 is pressed through the soaking blocks 19 and 19. In general, the so-called “upward pressing” of pressing by the upper press ram 17 as described above is generally used, but “downward pressing” by the lower press ram 18 and “double pressing” by both press rams 17 and 18 are adopted. Of course, it is also possible.

Further, in this hot pressing apparatus, by heating the press rams 17, 18, the press rams 17, 18 are heated.
The heat conduction from 18 heats the sample 16 indirectly through the soaking blocks 19 and 19. That is, the press ram 1 is installed in each press ram chamber 14, 15.
Electric resistance heating type heater 20 for heating 7, 18
The power supply device 21 is provided outside the heating chamber 11. The power supply device 21 includes an AC power supply 22, a thyristor type power regulator 23, a heater transformer 24, a thermocouple 25,
The power supply device 21 automatically controls the output of the heater 20 according to a preset heating pattern and also performs feedback control.

The press rams 17 and 18 are required to have high strength as well as excellent heat resistance and thermal conductivity. Therefore, graphite is used as the material. ing. Further, the press rams 17 and 18 are smaller in diameter than the sample 16, but the soaking block 19 is equal in diameter to the sample 16. Therefore, press ram 1
The pressing forces of 7, 18 are transmitted to the entire upper and lower surfaces of the sample 16 via the soaking blocks 19, 19, and the press ram 1
Heat conduction is performed from 7 and 18 to the entire surface of the sample 16.

The soaking block 19 has a thermal anisotropy that the heat conductivity in the radial direction is superior to the heat conductivity in the axial direction, and the sample 16 is transferred by the heat conduction from the press rams 17 and 18. When heating, the heat transfer in the radial direction of the sample 16 is made relatively higher than the heat transfer property in the axial direction to improve the uniform heat distribution in the radial direction. That is, the soaking block 19 has high strength like the press rams 17 and 18,
A plurality of (4 in the illustrated example) heat equalizing plates 27 formed of graphite, which is a material having high heat resistance and good thermal conductivity, are laminated, and each heat equalizing plate 27 itself has thermal anisotropy. However, since a plurality of the heat equalizing plates 27 are laminated, a thermal resistance against heat transfer in the axial direction is generated in the laminated surface, so that the entire heat equalizing block 19 has the above-mentioned thermal anisotropy. It has sex. Therefore, by interposing such a soaking block 19 between the press rams 17, 18 and the sample 16, the press rams 17,
When the heat is transferred from 18 to the sample 16, the heat transfer in the radial direction is relatively increased as compared with the heat transfer in the axial direction. As a result, the uniform heat distribution in the radial direction of the sample 16 is improved and the heat transfer in the radial direction is improved. Is soaked over the entire temperature range.

The sample chamber 13 also has a press ram chamber 1
A heater 28 similar to the one provided inside the heating chambers 4 and 15 is provided, and the power supply device 29 is provided outside the heating chamber 11. The power supply device 29 is composed of an AC power supply 22, a thyristor type power regulator 23, a heater transformer 24, a thermocouple 25, and a temperature controller 26, just like the power supply device 21. This sample chamber 13
The heater 28 in the press rams 17 and 18 as described above
It is for compensating the heat radiation from the sample 16 heated by the heat conduction from the to the surroundings. That is, when heat is radiated from the sample 16 to the surroundings, the temperature of the surface layer portion of the sample 16 may be lower than the temperature of the central portion thereof. By heating it to heat, the heat dissipation is prevented and the temperature drop is prevented.

FIG. 2 shows a sample 1 in this hot press machine.
6 shows a preferred example of the heating pattern of No. 6. The heating pattern shown in this drawing is such that the temperature of the press ram chambers 14 and 15 is raised in two steps as shown by the pattern P1 (shown by the solid line).

That is, the temperature of the press ram chambers 14 and 15 is increased at a predetermined temperature increasing rate to obtain a predetermined soaking temperature T1.
When the temperature reaches, the temperature is stopped and the temperature is maintained for a certain period of time, and then the temperature is further increased at a predetermined temperature increase rate to reach the final processing temperature T2, and thereafter the temperature is maintained. is there. Such heating of the press ram chambers 14, 15 by the heating pattern P1 is automatically performed by inputting the heating pattern P1 into the power supply device 21 in advance. Performs feedback control with high accuracy while measuring temperature.

When the press ram chambers 14 and 15 are heated by the heating pattern P1 as described above, the temperatures of the press rams 17 and 18 rise in a substantially similar pattern, and accordingly the heat from the press rams 17 and 18 increases. The sample 16 is heated by the conduction through the soaking blocks 19 and 19,
The sample 16 is heated in a pattern P2 (shown by a broken line) as shown in FIG.

By the way, when the temperature of the sample chamber 13 is not particularly controlled, the heat radiation from the sample 16 to the surroundings increases as the temperature of the sample 16 increases.
There is also a concern that the temperature of the surface layer portion of the sample 16 will be lower than the temperature of the central portion. Therefore, the temperature of the sample chamber 13 is also controlled to compensate for heat radiation from the sample 16 to the surroundings. That is, the temperature of the sample chamber 13 is also increased by following the increase in the temperature of the sample 16, so that these temperatures are always maintained at the same level, and thereby heat dissipation from the sample 16 to the surroundings is suppressed. In other words, the heater 28 also supplementally heats the sample 16 from its surroundings to prevent the temperature of the surface layer portion from decreasing.

Sample chamber 1 for compensating for such heat dissipation
The optimum heating pattern of No. 3 can be obtained by performing a trial run in advance, and the heating pattern P3 is set so that the temperature rise follows the heating pattern P1 of the press ram chambers 14 and 15 with a slight delay, as shown by the chain line in FIG. It will be
Then, the heating pattern P3 thus obtained in advance is input to the power supply device 29 to automatically control the output of the heater 28, and feedback control is performed while the temperature inside the sample chamber 13 is measured by the thermocouple 25. Perform high-precision temperature control.

The hot press machine having the above-mentioned structure is provided with the heater 2
The press rams 17 and 18 are heated by 0, and the sample 16 is indirectly heated by heat conduction from the press rams 17 and 18. Therefore, the sample 16 is pressed by both press rams 17 and 18 on both upper and lower surfaces. Therefore, as in the conventional general case where the sample 4 is directly heated by the heater 4 around the sample 16, a large temperature difference occurs between the surface layer part and the central part of the sample 16 during the temperature rising process. There is no such thing. Therefore, the soaking time can be shortened as compared with the conventional case, the processing time of the entire hot press processing can be shortened, and the soaking property inside the sample 16 can be improved to improve the product quality. Can contribute to.

FIG. 3 shows a hot pressing apparatus according to another embodiment of the present invention. The hot pressing apparatus of the above-mentioned embodiment uses electric resistance heaters 20 and 2 as heating means.
8, the induction heating type heating coils 30 and 31 are adopted as the heating means in the hot pressing apparatus of the present embodiment. That is, in this embodiment, induction heating coils 30 and 30 for heating the press rams 17 and 18 are provided outside the press ram chambers 14 and 15, and induction coils for auxiliary heating of the sample 16 are provided outside the sample chamber 13. Each heating coil 31 is arranged, and outside the heating chamber 11,
The power supply devices 32 and 33 are provided. The power supply devices 32 and 33 are both AC power supplies 34,
It is composed of an inverter type power regulator 35, a matching transformer 36, a thermocouple 37, and a temperature controller 38.
Even in the hot press machine configured as described above, the same operational effects as those of the above embodiment can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various applications and design changes can be considered. For example, in the above embodiment, each heating means is provided with an independent power supply device, but the power supply device is shared and the power supply output is distributed to each heater and each induction coil. You may make it simple.

The heat equalizing block used as the heat equalizing means in the above embodiment has the advantage that excellent anisotropy can be obtained only by laminating the heat equalizing plates. A suitable form as long as it has various anisotropy,
The material may be adopted.

It is also possible to stack a plurality of samples and subject them to hot pressing at one time. However, in the present invention, the samples are indirectly heated mainly by heat conduction from the press ram, so that the samples are stacked. It takes a long time to heat all the samples, and there is a concern that a relatively large temperature difference occurs in the axial direction of each sample. Therefore,
Such stacking of a plurality of samples and processing at the same time should be limited only when the processing time is not restricted and the temperature difference in the sample axis direction does not adversely affect the product quality.

Furthermore, it goes without saying that the heating patterns shown in the above embodiments are merely examples, and the optimum heating pattern may be set according to the quality required for the material of the sample and the product.

[0027]

As described above, the present invention has the following excellent effects. According to the hot pressing method of the invention of claim 1, since the sample is indirectly heated by heating the press ram and conducting heat from the press ram, the sample is heated from the pressing surface side by both press rams. Therefore, unlike the conventional case, a large temperature difference between the surface layer portion and the central portion does not occur, and as a result, the soaking time can be shortened and the processing time of the entire hot press processing can be shortened. The soaking property inside the sample can be improved, which can contribute to the improvement of product quality.

Further, in the invention of claim 2, since the heat is compensated by supplementarily heating the sample also from the periphery thereof, the uniform heat distribution in the radial direction of the sample is further improved. In the invention of claim 3, the press ram and the sample are improved. Since the soaking means is interposed between the soaking means and the soaking means, the soaking in the radial direction of the sample is further improved. In the invention of claim 4, since a soaking block in which a plurality of soaking plates are laminated is used as the soaking means. The thermal anisotropy required as a soaking means can be easily obtained.

Further, in the hot pressing apparatus according to the invention of claim 5, the press ram is heated in a press ram chamber which is insulated from the sample chamber, so that the sample in the sample chamber is indirectly heated by heat conduction from the press ram. Since it has a heating means for performing the method, it is suitable for use in carrying out the above method, and the temperature of the sample can be controlled with high accuracy.

Further, since the invention of claim 6 has a heating means for supplementarily heating the sample to compensate for heat radiation to the surroundings of the sample, the uniform heat distribution in the radial direction of the sample can be further improved. A heat equalizing means can be interposed between the press ram and the sample, so that the heat transfer in the radial direction can be further improved.
Since the invention of (1) employs an electric resistance heating type heater or an induction heating type heating coil as the heating means, any of them can efficiently heat the sample and can perform temperature control with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a hot pressing apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a heating pattern in the hot press device.

FIG. 3 is a schematic configuration diagram of a main part of a hot pressing apparatus according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a main part of a conventional general hot press device.

[Explanation of symbols]

 Reference Signs List 11 heating chamber 12 heat insulating wall 13 sample chamber 14,15 press ram chamber 16 sample 17,18 press ram 19 uniform heating block (uniform heating means) 20,28 heater (heating means) 21,29 power supply device 27 uniform heating plate 30,31 induction Heating coil (heating means) 32, 33 Power supply device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display H05B 6/44

Claims (9)

[Claims] 1. A hot pressing method in which a sample is heated and pressed by a pair of press rams, wherein the press ram is heated and the sample is heated by heat conduction from the press ram. 2. The hot pressing method according to claim 1, wherein the sample is heated from its surroundings to compensate for heat radiation from the sample to the surroundings. 3. The hot pressing method according to claim 1 or 2, wherein a soaking means having a higher radial heat transfer property than the axial heat transfer property is interposed between the tip of the press ram and the sample. A hot pressing method characterized in that a sample is heated and pressed by a press ram via the soaking means. 4. The hot pressing method according to claim 3, wherein a soaking block in which a plurality of soaking plates are laminated is used as the soaking means. 5. A hot press device configured to heat a sample in a heating chamber and press it with a pair of press rams. Inside the heating chamber, a sample chamber in which a sample is arranged by a heat insulating wall and each press ram are respectively arranged. Two
The press ram is divided into two press ram chambers, the tip of each press ram is inserted into the sample chamber through the heat insulating wall, and the portion of the press ram located inside the press ram chamber is heated to transfer heat from the press ram. A hot pressing apparatus comprising a heating means for heating a sample. 6. The hot pressing apparatus according to claim 5, further comprising heating means for heating the sample from its surroundings to compensate for heat radiation from the sample to the surroundings. Press machine. 7. The hot pressing apparatus according to claim 5 or 6, wherein heat equalizing means having a higher radial heat conductivity than the axial heat conductivity can be interposed between each press ram and the sample. A hot press device characterized by being configured. 8. The hot pressing apparatus according to claim 5, 6 or 7, wherein said heating means is constituted by an electric resistance heating type heater provided inside said heating chamber. . 9. The hot pressing apparatus according to claim 5, 6 or 7, wherein the heating means is constituted by an induction heating type heating coil provided outside the heating chamber. .