JPH0445032Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is an atmosphere sintering furnace for producing molded products by heating and sintering metal powder, ceramics, etc. in a specific atmosphere such as a high-pressure gas atmosphere. This invention relates to an improved internal temperature measurement structure.

(Prior art) An atmosphere sintering furnace is one in which a metal or ceramic powder material is placed in a furnace body capable of vacuum processing or high-pressure gas supply and exhaust, and heating and sintering is performed under the above-mentioned specific atmosphere. For example, one example is the one disclosed in Japanese Utility Model Publication No. 4872/1983.

That is, what is disclosed in the same publication is a hot isostatic press (HIP press) in which metal or ceramic powder is heated in a high-pressure inert gas atmosphere and isotropically compressed to perform high-density sintering. However, the outline thereof will be explained below with reference to FIG. 2, and the conventional structure of the temperature measuring member that is the subject of the present invention will be explained with reference to FIGS. 3 and 4. In FIG. 2, the sintering furnace body 1 consists of a container body 1a that can be vacuum-processed or capable of supplying and discharging high-pressure gas, and a container lid 1b that is removably sealed to the container body 1a. constitutes a mounting table 7 for the material to be sintered and a processing space 8 for the material to be sintered placed on the table 7. Surrounding this is an electric heater 3 which is a heat source for sintering, and a heat insulator is placed outside of the sintering table 7. layer 2
By arranging these, the sintering process of the material to be sintered is performed in a vacuum atmosphere, a high-pressure inert gas atmosphere, or the like. At this time, in order to measure the internal temperature in the furnace body, it is necessary to provide a temperature measuring member inside the furnace body, and as is generally known, a thermocouple 5 as a temperature sensor and the thermocouple 5 are placed inside the furnace. Protection tube 4 for protection from the atmosphere
A temperature measuring member is formed by the above, and due to space constraints, this is placed between the mounting table 7 and the energized heater 3, or attached to the mounting table 7, and connected to the thermometer 6 outside the furnace body. (See Utility Model Publication No. 62-4872 cited above for details of the above-mentioned parts).

Although FIG. 3 shows a thermocouple 5 and a protection tube 4 for preventing its contamination and damage, the thermocouple 5 may be of either an insulator type or a sheath type as is known, and the protection tube 4 can be selected depending on conditions such as sintering temperature and furnace atmosphere, and generally the sintering temperature
It is also known that metal materials, ceramic materials, etc. are used in the temperature range of 1500°C or lower, and ceramic materials are used exclusively in the temperature range of 1500°C or higher because heat resistance is particularly required. In this type of atmosphere sintering furnace, as shown in FIG. 2, the sintering furnace body 1 is cylindrical, leaving a mounting table 7 and a space for placing the material to be sintered in the center. Since the heat insulating layer 2 and the energizing heater 3 are arranged around the periphery, the installation space for the temperature measuring member is limited between the heater 3 and the mounting table 7, and as a result, the temperature measuring member inevitably comes close to the energizing heater 3. Become. This proximity of the energizing heater 3 and the temperature measuring member causes the following problem. That is, the thermocouple 5, which is a temperature sensor, is affected by the electromagnetic field around the heater that is generated by the current and voltage applied to the energized heater 3. If such an influence occurs, the output of the thermocouple 5 will change, so
This results in temperature measurement errors. Therefore, in order to perform accurate temperature measurement, in order to eliminate the influence of the electromagnetic field of the energized heater 3, a known electromagnetic shielding structure is installed between the heater 3, which is the generating side, and the thermocouple 5, which is the disturbed side. It is necessary to intervene. In other words, it is sufficient to close off the space between the generating side and the disturbed side with a wall of zero potential, but in this case, when the sintering temperature is 1500℃ or less, metal materials, Since the protective tube 4 made of ceramic material is used, if the protective tube 4 shown in FIG. 3 is made of metal, the protective tube 4 will have an electromagnetic shielding effect as well as a protective effect for the thermocouple 5. No hindrance. However, in cases where the sintering temperature is 1500°C or higher, it is customary to use ceramic materials for the protection tube 4 from the viewpoint of heat resistance, so this ceramic protection tube 4 cannot be expected to have an electromagnetic shielding effect. .

For this reason, when adding an electromagnetic shielding structure to the thermocouple 5 under conditions of a sintering temperature of 1500°C or higher, as shown in Fig. 4, the thermocouple 5 is protected by a ceramic protective tube 4, and a double-tube structure is adopted in which the outside of the protective tube 4 is further covered with an electromagnetic shielding tube 9 having an electromagnetic shielding effect. This electromagnetic shielding tube 9 must also be heat-resistant, so it is made of heat-resistant metal materials such as tungsten and molybdenum, or carbon materials.

(Problems to be solved by the invention) In the temperature measuring member using a double tube structure in which the thermocouple 5 described above is covered by the protection tube 4 and the electromagnetic shielding tube 9, there are major problems in the following points. There is. As shown in the figure, both the protection tube 4 and the electromagnetic shielding tube 9 have a shape with one end closed, and since there is a heat insulating space 10 between the two tubes 4 and 9, the thermal response of the thermocouple 5 is This is the point at which the growth rate slows down considerably. Such poor thermal response not only takes a long time to measure the true temperature, making it difficult to quickly and accurately grasp the temperature inside the furnace, but also
As shown in the figure, there is a drawback that an unexpected overshoot phenomenon of the temperature inside the furnace occurs during the temperature raising process.
In extreme cases, the sintered product may become defective, so there is an urgent need to find a solution for those using temperature measuring members with a double tube structure.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention aims to improve the thermal response of a temperature measuring member with such a double tube structure by adding a simple structure. Specifically, in the sintering furnace, which is capable of generating a specific atmosphere, the electric heater, which is the heat source for sintering, and the furnace In a device in which a thermocouple-based temperature measuring member is disposed as an internal temperature measuring member, the thermocouple is covered by a protection tube, and the protection tube is also covered by an electromagnetic shielding tube, and the electromagnetic shielding tube has at least two The aim is to open more than one atmospheric entrance and exit.

(Function) According to the above-mentioned technical means of the present invention, as shown in FIG. It is covered with an electromagnetic shielding tube 19 made of a heat-resistant metal material or carbon material and also having one end closed, and the electromagnetic shielding tube 19 is provided with at least two atmosphere inlets and outlets 21 and 22 as shown in the figure. , whereby the space 2 existing between the protection tube 4 and the electromagnetic shielding tube 19
By making 0 an atmospheric space through which the atmosphere can flow in and out, the following effects occur. That is, the thermocouple 5, the protection tube 4, and the atmosphere inlet/outlet 2 on the circumferential side thereof.
Electromagnetic shield pipe 20 with multiple openings of 1 and 22
As previously shown in Figure 2, the temperature measuring member according to
When installed in the atmosphere sintering furnace body 1, the high temperature and high pressure gas atmosphere inside the furnace body 1 is provided through the entrance and exit port 2.
1 and 22, gas flow is caused in and out of the space 20 between the electromagnetic shielding tube 19 and the protection tube 4 as shown by the arrow in the figure, thereby significantly activating the heat transfer. Thermal responsiveness on the thermoelectric body 5 side can be improved.

As is generally known, heat transfer between a fluid and a solid tends to be much larger when the fluid is flowing than when the fluid is stationary. In contrast to the illustrated example having the heat insulation space 10 between the electromagnetic shield tube 9 and the protection tube 4, two or more atmosphere entrances and exits 21 and 22 are opened in the electromagnetic shield tube 19 as in the present invention,
By activating the flow of the atmosphere, the heat transfer performance is significantly improved, which leads to faster thermal response on the thermocouple 5 side, and together with the electromagnetic shielding effect of the electromagnetic shield tube 19, accurate Temperature measurement can be carried out quickly, and it is particularly effective in high-pressure atmospheres. In addition, for low-pressure atmospheres, the gas flow effect of the atmosphere inlets and outlets 21 and 22 is small, so the atmosphere inlets and outlets 21 and 22 are
By increasing the number of holes 1 and 22 and the opening area as much as possible, a similar effect can be obtained by improving the gas flow effect and also by using the heat transfer effect due to radiant heat passing through the entrances and exits 21 and 22. Thermal radiation heat transfer from this opening works effectively even in a vacuum atmosphere, and this improves the thermocouple's thermal response and temperature measurement accuracy, as well as improves temperature measurement during temperature rise. This makes it possible to reduce the overshoot phenomenon of the temperature inside the furnace.

(Embodiment) A suitable embodiment of the invention will be described with reference to FIG. The structure of the atmosphere sintering furnace may be exactly the same as the conventional atmosphere sintering furnace shown previously in FIG. 2, except for the temperature measuring member. The thermocouple 5 is exactly the same as a conventional thermocouple, and the protective tube 4 with one end closed to prevent contamination or damage to the thermocouple 5 is made of ceramic material such as aluminum oxide, magnesium oxide, or boron nitride. It is appropriate to use a heat-resistant metal material such as tungsten or molybdenum or a carbon material for the electromagnetic shielding tube 19, which also has one end closed and covers the protection tube 4. There are at least two atmosphere inlets and outlets 21 and 22 opened on the circumferential side of the electromagnetic shielding tube 19, and the opening positions of the atmosphere openings 21 and 22 are set in accordance with the flow of atmospheric gas in the furnace.
The position is such that it can flow smoothly into and out of the space 20 between the protective tube 4 and the protective tube 4. As an example, when the protective tube 4 is made of aluminum oxide, the electromagnetic shield tube is made of graphite, and the inside of the furnace is set to an argon gas atmosphere as the specific atmosphere, the thermal conductivity of aluminum oxide is 15 kcal/mhr℃, and the graph Aite has a thermal conductivity of 100 kcal/mhr°C, whereas argon gas has a thermal conductivity of 5×10 ^-2 kcal/mhr°C, which is extremely low. Therefore, in order to improve the thermal responsiveness of the thermocouple 5, it is necessary to increase the heat transfer in this gas layer. Atmosphere entrances and exits 21 and 22 as shown
If the flow of gas inside and outside the tube is activated, the heat transfer in the gas layer will be improved, the thermal response of the thermocouple 5 will be made faster, and the number and area of the ports 21 and 22 will be reduced. The increase in radiant heat transfer through the doorway openings can also be utilized.
This makes it possible to improve the thermoresponsiveness of the thermocouple, regardless of whether the pressure is high or low, as described above in the section on operation.

(Effects of the invention) According to the invention, in order to improve temperature measurement accuracy, a serious problem that occurs in a temperature measurement member with a double tube structure that requires an electromagnetic shield tube in addition to a protection tube, This effectively improves the thermal response deterioration of thermocouples that occurs during heating, ensures accurate and prompt thermal response of thermocouples, provides error-free temperature measurement results, and prevents overshoot of the temperature inside the furnace during temperature rise. In addition, the number and area of the atmosphere entrances and exits 21 and 22 are appropriate for the required structure.
It is also extremely advantageous in that it is simple in that it is sufficient to simply provide the electromagnetic shielding pipe 19 with a.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional front view of the main part of the embodiment of the present invention, Figure 2
The figure is a longitudinal sectional front view of one example of an atmosphere sintering furnace, Fig. 3 is a longitudinal sectional front view of the main part of a conventional single-tube type temperature measuring member, and Fig. 4 is the same front view of the same double-tube type temperature measuring member. 5
The figure is a graph diagram explaining the overshoot phenomenon. DESCRIPTION OF SYMBOLS 1... Furnace body, 2... Heat insulation layer, 3... Current heater, 5... Thermocouple, 4... Protection tube, 19... Electromagnetic shielding tube, 21, 22... Atmosphere entrance/exit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) Inside the sintering furnace which is capable of generating a specific atmosphere, an electric heater, which is a heat source for sintering, and In a device in which a thermocouple-based temperature measuring member is provided as a furnace temperature measuring member, the thermocouple is covered by a protection tube, and the protection tube is also covered by an electromagnetic shielding tube, and the electromagnetic shielding tube includes at least An atmosphere sintering furnace characterized by having two or more atmosphere entrances and exits. (2) The atmospheric sintering furnace according to claim 1, wherein the protective tube is made of heat-resistant ceramics such as aluminum oxide, magnesium oxide, boron nitride, etc. (3) The atmosphere sintering furnace according to claim 1, wherein the electromagnetic shield tube is made of a heat-resistant metal material such as tungsten or molybdenum, or a carbon material.