JPH02305904A - Method for sintering material to be sintered and hot pressing apparatus using to this - Google Patents

Abstract

PURPOSE:To eliminate dispersion of the property in a sintered material and to facilitate taking-out of the sintered material by heating and pressurizing the material to be sintered packed in a mold while applying vibration. CONSTITUTION:To the material to be sintered packed in the mold 1, the sintering is executed by heating while applying the vibration with an automatic generator 8, etc., attached to a pushing bar 6 or a pushing table 7 and pressurizing to uni-axial direction. As the actual hot pressing condition, it is effective that this is pressed while applying the vibration of about 50Hz from the point of time when the temp. of the material to be sintered reaches the softening temp. thereof. By this method, the sintered material having complicate shape can be uniformly manufactured.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for sintering ceramics, metals, composite materials thereof, etc. to be sintered and crimped under high temperature and high pressure, and a method for sintering objects to be sintered, and uses thereof. Place in hot press equipment.

(Prior technology) Hot press equipment is widely used to pressurize and sinter powders or temporary compacts of ceramics, metals, composite materials, etc., and is used to obtain various sintered bodies with higher functionality than before. There has been a desire for a highly productive hot press device that can increase press pressure and perform continuous production.

As shown in Fig. 1, one of the conventional examples of the furnace core of this hot press equipment includes a cylindrical carbon mold (1) filled with the material to be sintered (4), a heating element (induction heating Coil, heater for resistance heating) (2), insulation material (3), punch (upper bunch, lower punch) (5), push rod (6), push stand (7)
).

Then, the mold (1) is filled with the material to be sintered (4), and while being heated, the push rod (6) and the push stand (7) are passed through the punch (5).
The material to be sintered (4) is sintered by applying pressure.

However, when such a conventional hot press apparatus is used, there are the following problems.

- Due to uniaxial pressure, filling and pressure propagation of the material to be sintered, which is the raw material powder, cannot be performed sufficiently in the complex-shaped carbon mold.
Therefore, it is not possible to obtain a sintered body having a complex shape and having uniform physical properties.

■The carbon mold and the object to be sintered are shrink-fitted due to the difference in thermal expansion coefficient, and the carbon mold is plastically deformed at the part where it comes into contact with the object to be sintered when pressurized.
It takes time to take out the sintered body.

In contrast, a method using a hot isostatic press (HIP) has recently been considered as a means of obtaining sintered bodies with complex shapes, but this requires a lot of preparation and leads to extremely high costs. Additionally, there are unresolved problems in the development of HIP's unique seal that does not cause uneven molding, so it is currently not sufficiently effective.

Furthermore, the sintered body after hot pressing cannot be taken out from the mold without the use of a separate sintered body removal device that combines a jack or the like, which hinders the improvement of productivity.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and even when sintering is progressed while applying uniaxial pressure using a hot press device, uniform physical properties can be achieved. It is possible to easily obtain a sintered compact with a complex shape, and at the same time, the sintered compact can be easily taken out without using a separate device or requiring a lot of manpower to take out the sintered compact from a mold. The present invention aims to provide a method for sintering a sintered product and a hot pressing device.

(Means for Solving the Problems) That is, the method for sintering the object to be sintered according to claim 1 includes heating and pressing the object to be sintered filled in a mold in a uniaxial direction. A method for sintering a mold, which is characterized by heating and pressurizing the object to be sintered while applying vibration, and the hot press device according to claim 2 has an upper punch and a lower punch at the upper and lower parts of the mold. In a hot press device for sintering, which is equipped with a press stand and a push rod for placing punches and pressing one of these punches, vibration is applied to the object to be sintered filled in the mold on the press stand or the push rod. It is characterized by being equipped with a vibration generator.
′ As a vibration generator, it is preferable to use an air-type vibrator that generates vibrations by rotating a ball using the force of compressed air, or a motor-type vibrator that uses high frequency as they are robust and less likely to break down. The vibration generator (8) may be mounted directly on one end of the push rod (6) or on the push stand as shown in Figs. 2 to 4, and there are no particular limitations. It can be used by being attached to the tips of both push rods or directly to the push stand.

In addition, in order to efficiently transmit the vibration to the object to be sintered (4), the structure disclosed in Japanese Patent Application No. 63-304763 previously filed by the present applicant, that is, the push stand (7) and push rod (6) It is effective that at least one of the pressing surfaces of the jumper or the pressing surface between the push rod (6) and the punch (5) has a spherical shape.

The shape of the punch, push rod, and push stand in the direction of the pressing axis is generally cylindrical, but depending on the shape of the object to be hot pressed, it may be polygonal such as a square prism or hexagonal prism, or other free shapes. There may be.

In addition to carbon, the materials for the mold of the hot press machine equipped with a vibration generator, as well as the punch, push rod, and push stand, include oxide ceramics such as alumina, zirconia, and calcia, and nitride materials such as silicon nitride and boron nitride. material ceramics,
Examples include carbide ceramics such as silicon carbide and boron carbide, and heat-resistant metals. In addition, fiber-reinforced composite materials using carbon fibers, silicon carbide fibers, etc., C/C composites, or particle-dispersed composite materials with improved vibration resistance using the above materials as base materials are used. can do.

Note that carbon materials are preferable as the material in view of conditions such as heat resistance, workability, lubricity, and large size. In particular, among carbon materials, isotropic graphite materials have almost the same physical properties in all directions, so they are convenient in terms of material selection and strength design.

When performing hot pressing, a mold with a complex shape that matches the shape of the object to be sintered is used, or a mold with a simple shape is used in which the object to be sintered is temporarily formed into a complex shape and filled with a powdered secondary pressure medium. Can be used.

The powder for the secondary pressure medium may be selected based on conditions such as good fluidity, no reaction with the object to be sintered or the mold, and ease of removal after hot pressing. Heat-resistant materials such as graphite, aluminum oxide, silicon carbide, and boron nitride can be used alone or in an appropriate mixture. The shape of the secondary pressure medium powder is preferably spherical so that pressure can be propagated more isotropically.

Next, as for actual hot pressing conditions, it is effective to press while applying vibrations of 50 Hz or more when the temperature of the object to be sintered reaches its softening temperature. Of course, vibration may be applied at the same time as heating the object to be sintered. In this case, it is preferable to apply vibration when the filling is insufficient and there is a large amount of decomposed gas or residual air in the object to be sintered. When the final target temperature is reached, press pressure and vibration are applied while maintaining the temperature level until the thickness of the sintered object no longer decreases. When the press pressure is released and the cooling stage begins, the vibration applied is 5
It is preferable to set the frequency to 0 Hz or less, and it is sufficient to apply vibration only from a push stand, a push rod, or a punch on one side of the upper and lower sides.

The vibration applied in the temperature range from the softening temperature to the final target temperature is
50) (The reason why z or more is preferable is that if the 50 Hz is not used, the softened powder to be sintered will not be sufficiently disturbed within a short period of time, and the effect of the vibration propagation will be transmitted to all parts of the complex shape. This is because it takes a long time to cross.Also,
When the press pressure is released and the cooling stage begins, the objective is to remove the shrink fit caused by mismatch in the coefficient of thermal expansion between the mold and the sintered body, and to remove the secondary pressure medium. A frequency of 50 Hz or lower, which tends to cause interfacial peeling such as fitting, is effective.

(Function of the Invention) In the method for sintering the object to be sintered according to claim 1, the filling of the object to be sintered into the mold can be sufficiently progressed by the vibration applied to the object to be sintered, and the sintering object can be sintered. It is possible to eliminate variations in physical properties of the body.

Further, the hot press apparatus according to the second aspect of the present invention has the following effects by providing a vibration generator on the push stand or the push rod.

■The vibrations applied by the vibration generator are transmitted to the powder object to be sintered via the push rod, press stand, and punch, causing the object to be sintered to be disturbed and vibrated as it begins to soften due to heating and pressure. In addition, it is possible to uniformly and completely fill all parts of a complex-shaped mold with the material to be sintered, and to accelerate sintering in a heated and pressurized state.

■By-product gas generated during sintering of the object to be sintered is agitated by vibration, which improves gas release.

■Increases the packing density of the object to be sintered before sintering.

■Shrink-fit conditions caused by mismatch in thermal expansion coefficients during cooling of the mold and sintered body are eliminated.

(Example) Next, the present invention will be specifically explained using examples.

As shown in FIG. 2, a complex-shaped silicon nitride was sintered using a hot press machine equipped with a pneumatic ball vibrator as a vibration generator on the upper press. Continue to operate the vibrator at a frequency of 500Hz from 1600℃ to 170℃.
After holding at 0°C for 40 minutes, the pressure was released. After releasing the pressure, the frequency was set to 50 Hz, and the vibrator was operated until cooling was completed.

On the other hand, as a comparative example, the same silicon nitride was sintered in the same manner under all the same conditions except that no vibration was applied using a conventional hot press apparatus without a vibration generator.

As a result, the variation in physical properties of the silicon nitride sintered body obtained using the vibration-applied apparatus of Example 1 was 1/1 compared to that of the comparative example.
It decreased to 5. In addition, in the comparative example, when the sintered body was removed from the mold, both the sintered body and the mold were tightly shrink-fitted, and a removal jig was required, but in Example 1, the sintered body was The body and mold were completely separated, and no jig was required to take out the sintered body.

As shown in Figure 3, complex-shaped silicon alloys are manufactured using a hot press machine equipped with a vibrator, which is a set of motors that generate vibrations through eccentric movement caused by motor rotation, as a vibration generator on the lower press stand. was sintered. Continue to operate the vibrator at a frequency of 100Hz from 1200℃, and then raise the temperature to 1400℃.
After holding for 35 minutes, the pressure was released. After releasing the pressure, the frequency was set to 50 Hz, and the vibrator was operated until cooling was completed.

On the other hand, as a comparative example, the same silicon alloy was sintered using a conventional hot press apparatus without a vibration generator under all the same conditions except that no vibration was applied.

As a result, the variation in physical properties of the silicon alloy sintered body obtained using the vibrating apparatus of Example 2 was 1/1 compared to that of the comparative example.
decreased to 0. In addition, in the comparative example, when the sintered body was removed from the mold, both the sintered body and the mold were firmly shrink-fitted, and a removal jig was required, but in Example 2, the sintered body was removed from the mold. The body and mold were completely separated, and no jig was required to take out the sintered body.

As shown in FIG. 4, complex-shaped aluminum oxide was sintered using a hot press machine equipped with pneumatic ball vibrators as vibration generators on the upper and lower presses, respectively. From 1650℃, the upper and lower vibrators were operated at a frequency of 500Hz, and the temperature was increased to 1800℃.
After holding for 20 minutes, the pressure was released. After the pressure was released, the frequency was set to 50 Hz, and only the vibrator attached to the lower press was operated until cooling was completed.

On the other hand, as a comparative example, the same aluminum oxide was sintered in the same manner under all the same conditions except that no vibration was applied using a conventional hot press apparatus without a vibration generator.

As a result, the variation in physical properties of the aluminum oxide sintered body obtained using the vibrating apparatus of Example 3 was reduced to 1/20 compared to that of the comparative example. In addition, in the comparative example, when the sintered body was removed from the mold, both the sintered body and the mold were tightly shrink-fitted, and a removal jig was required, but in Example 3, the sintered body was removed from the mold. The mold was completely peeled off, and no jig was required to remove the sintered body.

(Effects of the Invention) As explained above, by using the method for sintering a material to be sintered according to claim 1 and the hot press apparatus according to claim 2, it is possible to produce a material that cannot be produced using a conventional hot press apparatus. It is possible to uniformly produce sintered bodies with complicated shapes, which previously could not be produced, with extremely little variation in physical properties, and at the same time, the sintered bodies can be easily removed from the mold, thereby improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of the furnace core of a conventional hot press device, and FIGS. 2 to 4 are sectional views showing an embodiment of the hot press device according to claim 2. Explanation of symbols 1... Carbon mold, 2... Induction heating coil, 3...
・・Insulating material, 4・Sintered object, 5・Punch, 6・
... Push rod, 7... Push stand, 8... Vibration generator. that's all

Claims (1)

[Claims] 1). A method of sintering a material filled in a mold by applying pressure in a uniaxial direction while heating the material, which is characterized by heating and pressurizing the material while applying vibrations to the material. Method for sintering objects to be sintered. 2). In a hot press device, which is equipped with an upper punch and a lower punch arranged at the upper and lower parts of the mold, and a press stand and a push rod for pressing either of these punches, the press stand or the push rod is provided with a material filled in the mold. A hot press device characterized by being equipped with a vibration generator that applies vibration to a sintered product.