JPH0252982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal expansion/contraction measuring device suitable for use in a hot press device, which uses a high-temperature, high-pressure gas as an internal atmosphere gas.

In recent years, ceramics and fine ceramics have been in the spotlight as various mechanical materials or electrical and electronic materials.
After being molded by various molding methods such as injection molding and extrusion molding, it is sintered to increase its strength.

When this sintering is performed, the volume of the ceramic generally shrinks more than before firing, and this shrinkage becomes even larger when pressure sintering is performed using a hot press.

Ceramics, in particular, as a material for machinery, has strict dimensional accuracy required for its use, so in the case of large firing shrinkage, the characteristics of the raw materials and the firing conditions (e.g. heating rate, holding temperature, firing time and atmosphere)
It is necessary to check the shrinkage rate by changing the

Furthermore, in ceramics after sintering, it may be necessary to check in advance the temperature-dependent expansion coefficient depending on the use.

In addition, ceramics to date generally have a relatively low vapor pressure even at their melting point, with the exception of some nitrides that easily sublimate. When attempting to obtain ceramics containing volatile components by the hot pressing method, it is necessary to use the physical property that the vapor pressure of such volatile components increases exponentially as the temperature increases. It is urgently necessary to suppress the evaporation of volatile components.

By the way, conventional hot press equipment generally uses a hydraulic press as the pressurizing mechanism, but as mentioned above, in order to suppress the evaporation of volatile components, it is possible to create a high-pressure inert gas atmosphere inside the furnace. , a large amount of pressure is required to push out the piston against this internal pressure, which makes the device bulky, and
A problem arose in that oil adhering to the piston disturbed the composition of the internal atmospheric gas.

The present invention has been made in view of the above, and its object is to provide a thermal expansion/contraction measuring device that is particularly suitable for application to hot press equipment that uses high-temperature, high-pressure inert gas. .

The present invention will be described in detail below based on an embodiment shown in the drawings. Supports 3, 3 are fixed to a foundation concrete 2 in which a groove 1 is provided.
An electric furnace body 4 made of, for example, stainless steel and having a heat-resistant and pressure-resistant structure is attached to the pillars 3, 3, and is equipped with a high-pressure joint 4a. Inside the electric furnace body 4,
A two-part heating element 5 made of, for example, graphite is erected, and an upper punch rod 6 made of, for example, stainless steel and graphite is inserted into the interior of this heating element 5, which is fixed to the furnace top 4b.

An upper cylinder 7 is connected to the furnace bottom 4c in a sealed manner and communicates with the furnace body 4, and a known take-out valve 9 is connected in a sealed manner to a mounting flange 8 of the upper cylinder 7. The lower connecting flange (not shown) of the take-out valve 9 and the upper connecting flange (not shown) of the intermediate cylinder 10 are
The intermediate cylinder 10 is securely and removably connected by a known split fastening ring 11.
The other lower connecting flange 10a is connected to the upper connecting flange 12a of the pressurizing cylinder 12 through an insulating material 13, such as Teflon, as shown in FIG.
Connected confidentially by. Also between the mounting bolts 10b, 10b and the lower flange 10a, an insulator 14, such as bake, is interposed, so that the pressurizing cylinder 12 and the electric furnace body 4 are electrically insulated from each other.

A guide cylinder 15 screwed to the lower connecting flange 12b is inserted through the pressurizing cylinder 12 in the internal axial direction.
A hollow piston tube 16 that acts as a piston rod is housed inside the pressurizing cylinder 12 so as to be movable in the axial direction. Then, this piston pipe 16 and the pressurizing cylinder 12
A sealing member 1 is provided between the upper flange 12a and the upper flange 12a.
7 is provided to seal between the piston pipe 16 and the pressurizing cylinder 12. At the same time, this seal member 17 seals between the inside of the furnace and the third pressure chamber 12c between the pressurizing cylinder 12 and the piston pipe 16. A piston 18 is provided at the bottom of the piston tube 16, and the piston 18 seals between the piston tube 16 and the guide cylinder 15 and between the piston tube 16 and the pressurizing cylinder 12.

High-pressure joints 19 and 20 are attached to the upper flange 12a of the pressurizing cylinder 12, and passages 21 and 22 are provided from the high-pressure joints 19 and 20. The passage 21 opens at the upper part of the sealing member 17 and connects the electric furnace. The passage 22 communicates with the inside of the body 4 and opens at the lower part of the sealing member 17 to form a third pressure chamber 12c between the pressurizing cylinder 12 and the piston pipe 16.
It communicates with

On the other hand, the lower flange 12 of the pressurized cylinder 12
Similarly, high-pressure joints 23 and 24 are attached to b, and from these high-pressure joints 23 and 24 there is a passage 2.
5 and 26, the passage 25 opens into a first pressure chamber 27 provided in communication with the guide cylinder 15, and the passage 26 opens into a second pressure chamber 27 provided following the lower end of the pressurizing cylinder 12. It is connected to 28. As particularly shown in FIG. 1, the high pressure joints 19 and 24 are communicated with each other through a valve 29 and a communication pipe 30 such as a pressure hose.

Lower connecting flange 12b of lower cylinder 12
The mounting flange 31a of the storage case 31 of the measuring instrument with a pressure-resistant mechanism is securely attached in communication with the pressurizing cylinder 12, and this storage case 3
A cylindrical measuring device 32 such as a differential transformer, for example, is housed inside the measuring device 1 . This measuring device 3
A measuring needle 33, which is biased upward by a spring or the like, protrudes from the upper part of the measuring needle 2, and the closed lower end of the guide pipe 34 contacts the tip of the measuring needle 33.
This measuring needle 33 stops when the weight of the guide pipe 34 is balanced by the elasticity of the spring, and when the guide pipe 34 rises from this point, it also rises, and when the raised guide pipe 34 becomes free. , and is configured to descend until it balances with the weight of the guide pipe 34. The guide pipe 34 is connected to the pressure cylinder 1
It extends so as to be movable upward in the guide cylinder 15 inside the pressure cylinder 12 via a bearing 35 provided on the lower connecting flange 12b of 2. A measuring rod 36 provided with a locking portion 36a that engages with the tip of the measuring rod 34 is inserted. The tip of this measuring rod 36 is screwed onto the inner top of the piston tube 16, and the electric furnace body 4 and housing case 31 side are connected to the power source 37 and the signal detector 3.
It is electrically connected via 8. Next, to explain how to use it, loosen the fastening ring 11, remove the lower flange of the take-out valve 9 and the upper connecting flange of the intermediate cylinder 10, and move the intermediate cylinder 10 and the pressure cylinder 12 downward. The press mold 40 containing the molded sample A is placed on the upper end of the lower punch rod 39 made of stainless steel and graphite exposed at the upper part of the rod, and the press mold 40 is moved and the clamping ring 1 is inserted again.
1, after connecting the lower flange of the take-out valve 9 and the upper connecting flange of the intermediate cylinder 10 in a confidential manner from the axial direction, the take-out valve 9 is opened and the inside is evacuated several times via the high-pressure joint 4a.
Thereafter, when a high pressure inert gas such as A _r or N ₂ is introduced, the area from the inside of the electric furnace body 4 to the intermediate cylinder 10 is filled with high pressure inert gas. Then, the piston tube 16 is pushed downward via the lower punch rod 39 by the internal pressure of this inert gas, but the valve 29 is opened as shown in FIG. When the inert gas is introduced to the second pressurizing chamber 28 through the communication pipe 30, the second pressurizing chamber becomes at the same pressure as the inside of the electric furnace body 4. Therefore, the pressure inside the electric furnace body 4 is P, the pressure receiving area on the upper end side of the piston pipe 16 is A, and the pressure receiving area on the lower end side is B, and the relational expression A×P<B×P is obtained. If we make it true, the internal pressure of the inert gas inside the electric furnace body 4 is high, for example 100 atmospheres, so
Even if the weight of the piston tube 16 is taken into consideration, the piston tube 16 will automatically move toward the electric furnace body 4 due to the difference in pressure receiving area between the upper end and the lower end of the piston tube 16. In this embodiment, A× The relational expression P≧B×P was made to hold true. Therefore, the high pressure joint 23
When more gas is introduced, the pressing force from the electric furnace body 4 side of the piston pipe 16 is caused by the pressure inside the electric furnace body 4 already being applied to the lower end of the piston pipe 16 via the communication pipe 30 as described above. Since the pressure is offset by the pressure, it is possible to move the piston pipe 16 toward the electric furnace body 4 at a relatively low pressure. This also means that when entering the pressing process, the pressing force can be calculated without directly pulling the internal pressure.

Incidentally, when the piston pipe 16 rises, the gas in the third pressure chamber 12c between the pressurizing cylinder 12 and the piston pipe 16 is discharged to the outside from the high pressure joint 20 via the passage 22.

In this way, the piston tube 16 rises against the high pressure inside the furnace, and when the press mold comes into contact with the upper punch rod 6, the circuit is electrically closed and the detector 38
detects the touch signal and notifies you of this. At this time, the measuring rod 36, which has risen together with the piston pipe 16, locks the engaging part 34a at the upper end of the guide pipe 34 with its locking part 36a, as shown in FIG. The mutual lengths are selected so as to lift the measuring needle 33, and the measuring needle 33 slides slightly upward as the guide pipe 34 rises.

Around this time, the heating element 5 starts heating, and when the thermocouple embedded in the upper punch rod 6 detects the desired temperature, high pressure gas is further introduced from the high pressure joint 23 to start hot pressing. . At this time, the evaporation of volatile components exhibiting vapor pressure proportional to temperature is suppressed by the high-pressure inert gas. When the hot press starts, the molded sample A contracts, so the lower punch rod 39 rises slightly,
At this time, the pressurizing force is applied to the first pressure chamber 2 from the high pressure joint 23.
It is measured by the gas pressure introduced into 7. Then, as the sample A contracts as pressure is applied by the piston tube 16, the measuring rod 36 also rises.
Pull up the guide pipe 34 that is locked by the locking portion 36a. Then, the measuring needle 33 in contact with the lower end of the measuring needle 33 rises by that amount due to the elasticity of a spring (not shown), and thereby the contraction width can be detected. A meter or digital display is displayed on a control panel (not shown).

The apparatus according to the present invention is capable of conducting experiments on these matters by changing the characteristics of the materials constituting the sample and the firing conditions such as temperature and atmospheric gas.

If the sample is already sintered ceramics and you want to know its expansion rate, move the press die 40 containing the sintered ceramic sample placed on the lower punch rod 39 to the upper punch rod 6. When heated without applying pressure with the punch rod, the expanded sample lowers the lower punch rod 39 through the punch stopper, and at the same time the piston tube 1
6 and the measuring rod 34 descends, the guide pipe 34 descends due to its weight and pushes down the measuring needle 33, which is displayed on a meter or the like. That is, the measuring needle 33 is initially stopped at a position where the weight of the guide pipe 34 is balanced by a spring (not shown), and the guide pipe 33 is stopped at a position where the press mold 40 contacts the upper punch rod 6. 34 is configured to be locked to the measuring rod 36 and lifted slightly, so that when the sample expands and the lower punch rod 39 lowers, and at the same time the piston tube 16 descends, the measuring rod 36 also descends. The guide pipe 34, which is freed by shifting its locking position, uses its weight to push the measuring needle 33 downward by the amount that the measuring rod 36 has descended, resisting the elasticity of the spring, causing it to expand. can be measured.

Furthermore, from the above explanation, it goes without saying that the shrinkage rate when molded ceramics are sintered under normal pressure can also be measured by the apparatus according to the present invention.

Next, when the hot press or the measurement of contraction and expansion is completed, high pressure gas is removed from the high pressure joint 23 and high pressure gas is introduced from the other high pressure joint 20, and the high pressure gas passes through the passage 22. It enters the third pressure chamber 12c and pushes the piston 18 to lower the piston pipe 16, so after lowering it to the lowest position, the take-out valve 9 is closed, the fastening ring 11 is loosened, and the piston pipe together with the intermediate cylinder 10 is lowered. 16 and below, press die 40.
The sample is taken out from the

Although the above description has been made for the case where a high-pressure inert gas is used, the device according to the present invention can also be applied to a hot press device that uses normal pressure, and can also be applied to a device other than a hot press device in which a piston pipe is used as a mere contact. It is applicable.

As explained in detail above, the present invention can be applied to a hot pressing device that uses high pressure inert gas at high temperature to measure the shrinkage rate of ceramics and other materials. This method has the advantage of being able to measure the expansion and contraction of ceramics.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a front view of a hot press device embodying the invention, FIG. 2 is an enlarged cross-sectional view of the device according to the invention, and FIG. 3 shows a press mold with an upper punch rod. FIG. 4 is an enlarged sectional view showing the state in which the measuring rod and the guide pipe are in contact with each other; FIG. A...sample, 4...electric furnace body, 5...heating element,
6... Upper punch rod, 10... Middle cylinder,
11...Tightening ring, 12...Pressure cylinder,
15... Guide cylinder, 16... Piston pipe, 18... Piston, 27... First pressure chamber, 2
8... Second pressure chamber, 30... Communication pipe, 31... Storage case, 32... Measuring device, 33... Measuring needle, 3
4...Guide pipe, 34a...Engaging portion, 36
...Measuring rod, 36a...Locking part, 39...
Lower punch rod.

Claims (1)

[Claims] 1 In a hot press device that uses high-temperature, high-pressure inert gas as an atmospheric gas, an upper punch rod is fixed to the upper part of the furnace body, and a lower punch is moved up and down by a pressurized cylinder using gas at the lower part of the furnace body. A rod is provided movably and the sample is placed on the upper part of the rod, and a storage case is installed in a confidential manner in communication with each other in the axial direction of the lower part of the pressurizing cylinder, and a container is placed inside the storage case. For example, a measuring device such as a differential transformer is housed, and a measuring needle that is slidably biased in one direction and can be expanded and contracted from the measuring device is provided to protrude upward in the axial direction, and the expansion and contraction width of this measuring needle is is detected by the measuring device, and the piston rod of the pressurizing cylinder is formed into a hollow piston pipe, into which a guide pipe is movably inserted, and the closed lower end of the guide pipe is inserted. The measuring rod is placed on the measuring needle so that the measuring needle is compressed by a predetermined distance due to its weight, and a measuring rod is movably inserted into the guide pipe, and its upper end is inserted into the hollow hole. A thermal expansion/contraction measuring device, characterized in that it is fixed to the inner upper part of a piston pipe, and a locking part provided at a lower end thereof engages with an engaging part of the guide pipe at a predetermined position. .