JPH0283272A - Glass capsule hip method of ceramic molded article - Google Patents

Abstract

PURPOSE:To obtain high-density sintered compact by wrapping a ceramic molded article with low-melting point glass in a crucible, covering the crucible with high- melting point glass and subjecting the molded article to hot isostatic pressing. CONSTITUTION:A seal material 2 such as graphite foil is provided on the inside of a graphite crucible 1. A low-melting point glass plate 3 is put thereon and compact 4 to be calcined such as silicon nitride to be treated is installed thereon. Then a low- melting point powder 5 is packed around the compact 4 to be calcined and then a low-melting point glass plate 6 is put on the compact 4 to be calcined and low-melting glass power 5. High-melting point glass plate 7 is further installed thereon. Then when the crucible 1 in which the compact 4 to be calcined is loaded in a hot isostatic press(HIP) apparatus to carry out HIP treatment, the low-melting point glass plates 3 and 6 and low-melting point powder 5 are melted and the compact 4 to be calcined is raised though the glass 9. Since the high-melting point glass plate 7 is not melted in this state, gas-tight state is maintained. When HIP treatment proceeds further, the high-melting point glass plate 7 is melted, but the compact to be calcined is descended through the melt since density of the compact 4 to be calcined becomes about 3.0 and gas-tight state is maintained until the treatment is finished.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention describes a method for obtaining a high-density sintered body by immersing a ceramic molded body in a glass bath and subjecting it to hot isostatic pressing. , the glass capsule HIP method).

(Prior Art) As is conventionally known, in the glass capsule HIP method, after covering the entire surface of a ceramic molded body to be sintered with a gas-impermeable glass film, a film of usually 10
A high-density ceramic sintered body is obtained by applying hot hydrostatic pressure of 0 to 3000 atm and 1000 to 2300 t. At this time, the ampoule method, the sintered glass method, and the glass bath method are known as glass encapsulation methods.

Conventionally, an example of glass encapsulation using the glass bath method is:
There is a method disclosed in Japanese Patent Publication No. 62-22954. As an example of this method is shown in FIGS. 4(a) and 4(b), a workpiece 22 such as a ceramic molded body is placed in a crucible 21 with glass plates 23, 23' above and below it, and glass plates 23 and 23' in between. It is surrounded and housed by glass powder 24. Crucible 21, their processed objects 22 and glass 2
3.23', 24, an air-impermeable and flexible graphite foil or sheet 25 is provided, surrounding the entire surface of the object 22 and the glass 23.23', 24. There is. Further, on the upper surface thereof, a weight 26 is freely movably placed to prevent the workpiece 22 from floating when the glass is melted during HIP.

As these glasses 23, 23' and 24, low melting point glass such as Pyrex (trade name) glass or high melting point glass such as silica glass or Vycor (trade name) glass is used.

(Problem to be Solved by the Invention) In the above-described configuration, the glasses 23, 23', 24
When a low melting point glass such as Pyrex glass is used as a ceramic molded object, the problem is that the glass melts at a low temperature where the density of the object to be processed 22 is low, and the object to be processed 22 floats in the molten glass. was there. Processed object 2
The levitation of 2 can be suppressed to some extent due to the weight 26, but
Depending on the position of the weight 26, the object 22 to be treated may be tilted and protrude from the surface of the melt, making it impossible to achieve good encapsulation.

In addition, when high melting point glass such as Vycor glass is used as the glasses 23, 23' and 24, the temperature is 1500°C.
Since it does not melt until the temperature reaches the above temperature, the glass seal is not effective until then, and there is also the problem that hydrostatic pressure cannot be applied to the object 22 to be treated.

The purpose of the present invention is to solve the above-mentioned problems, to be able to apply hydrostatic pressure from a low temperature stage until it reaches a high temperature, and to prevent protrusion from the surface of a workpiece such as a ceramic molded object even if it floats. The present invention aims to provide a glass capsule HIP method for ceramic molded bodies that can completely prevent the above.

(Means for Solving the Problems) The glass capsule HIP method of a ceramic molded body of the present invention is a glass capsule HIP method in which a ceramic molded body is immersed in a glass bath and subjected to hot isostatic pressing. It is characterized by hot isostatic pressing with the body wrapped in low-melting glass and the crucible covered with high-melting glass.

(Function) In the above-mentioned configuration, a low melting point glass is arranged in the crucible around the object to be processed such as a ceramic molded body, and a high melting point glass is placed on top of the low melting point glass in the crucible when the lid of the crucible is closed. Due to the placement of the lid, good glass encapsulation can be achieved as explained below.

i.e. glass (e.g. for Pyrex glass)
When the temperature exceeds 820° C., the low melting point glass starts to soften, and a force acting on the ceramic molded body therein causes it to rise. However, low melting point glass is in a highly viscous state and requires a considerable amount of time to float. When the glass temperature exceeds 1220° C., the viscosity becomes low enough for the ceramic molded body to easily float in the Pyrex glass. However, even if the ceramic molded body floats in the Pyrex glass bath at this temperature, a glass coating is still formed on its upper surface, and the ceramic molded body is surrounded by a gas-tight film.

When the temperature further rises to about 1500° C., the Pyrex glass coating on the upper surface of the ceramic molded body becomes so fluid that it runs off.

At this point, the Vycor glass placed on top begins to soften and acts to replace the Pyrex glass coating.

When the temperature reaches about 1700° C., Vycor glass also reaches a state where it is extremely easy to flow, but at this time the ceramic molded body has already reached the completion stage of sintering and has a density close to 3.0. Therefore, the ceramic molded body slowly sinks into the glass, making it possible to perform HIP of a glass capsule while being surrounded by a gas-tight film from beginning to end.

For reference, Figure 1 shows sintering aids! ,Ig
A sintering curve of silicon nitride containing 1 wt% O is shown.

(Example) FIGS. 2(a), 2(b), and 2(C) are diagrams each showing a state in which the glass capsule HIP method of the present invention is actually implemented. FIG. 2(a) is a diagram showing the state before being attached to the HIP device. In this embodiment, a sealing material 2 such as a graphite foil, a molybdenum plate, or a molybdenum foil is provided inside the graphite crucible 1.

A low melting point glass plate 3 such as Pyrex glass is placed thereon, and a fired object 4 such as silicon nitride to be processed is further placed thereon. Next, after filling a low melting point glass powder 5 such as Pyrex glass around the object to be fired 4, a low melting point glass plate 6 such as Pyrex glass is placed on the object to be fired 4 and the low melting point glass powder 5. Further, a high melting point glass plate 7 such as Vycor glass or silica glass is placed thereon, and preparations before mounting on the HIP device are completed.

When the crucible 1 with the object to be fired 4 placed inside the structure described above is mounted on a conventionally known HIP device and HIP processing is performed, the temperature exceeds 1220°C, as explained in the section of the above-mentioned operation. At this temperature, the low melting point glass plates 3 and 6 and the low melting point glass powder 5 melt, and the object to be fired 4 floats in the molten glass 9. This state is shown in FIG. 2(b). In this state, the low melting point glass melts, but the high melting point glass plate 7 does not melt, so a gas tight state can be maintained.

As the HIP process further progresses, the high melting point glass plate 7 melts as shown in FIG. Since it becomes higher than that, it descends in the glass melt, and the gas-tight state is maintained until the end of the HIP process.

FIGS. 3(a) to 3(d) are diagrams showing other examples of states when implementing the glass capsule HIP method of the present invention, respectively. In the examples shown in FIGS. 3(a) to 3(d), the same members as in the examples shown in FIGS. 2(a) to (C) are given the same reference numerals, and their explanations will be omitted. In the example shown in FIGS. 3(a) to 3(d), by further providing a high melting point glass plate 8 such as Vycor glass or silica glass in the center of the Pyrex glass bath, the time for the object to be fired 4 to float is further lengthened. This makes the glass capsule HIP described above even more reliable.

The present invention is not limited to the embodiments described above, but can be modified and changed in many ways. For example, in the embodiments described above, the examples shown as low melting point glass and high melting point glass are just examples, and the present invention can be applied to other combinations of materials if the above low melting point glass and high melting point glass are used. Needless to say, this can be achieved. Moreover, although silicon nitride is shown as an example of the object to be fired, it goes without saying that the present invention can be suitably applied to other materials as well.

(Effects of the Invention) As is clear from the above explanation, according to the glass capsule HIP method for ceramic molded bodies of the present invention, in the crucible before installation in the HIP apparatus, around the object to be processed such as the ceramic molded body. By placing low melting point glass and placing a high melting point glass lid on top of the low melting point glass in the crucible as the lid of the crucible, it is possible to achieve good glass encapsulation even in the glass bath method without using weights etc. can be achieved, and as a result, a high-density sintered body can be obtained.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between temperature and density in silicon nitride, Figures 2 (a) to (C) are diagrams showing the conditions when actually implementing the glass capsule HIP method of the present invention, and Figure 3 is a graph showing the relationship between temperature and density in silicon nitride.
Figures (a) to (d) are glass capsules H of the present invention, respectively.
Figures 4(a) and 4(b) are diagrams showing examples of the conventional glass capsule HIP method, respectively. 1...Graphite crucible 2...Sealing material 3.6.
...Low melting point glass plate 4...Object to be fired 5...Low melting point glass powder 7, Death...High melting point glass plate 9... Molten glass

Claims (1)

[Claims] 1. In a glass capsule HIP method in which a ceramic molded body is immersed in a glass bath and subjected to hot isostatic pressing,
The ceramic molded body is wrapped in low-melting glass in a crucible, and the crucible is covered with high-melting glass.
A glass capsule HIP method for a ceramic molded body, which is characterized by hot isostatic pressing.