JPH0132917B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a hot isostatic press device (hereinafter referred to as a HIP device) for sintering metal powder, ceramics, or a mixture thereof in a high-temperature, high-pressure gas atmosphere, particularly in a high-pressure chamber. This relates to the configuration of the heat insulating layer to be placed.

In recent years, the demand for processing various materials under high temperature and high pressure has increased, and HIP equipment has been attracting attention as a device for this purpose.

According to this HIP equipment, powder materials such as metal powders and ceramic powders can be sintered under high pressure, and they have higher density and strength than those sintered under atmospheric pressure or vacuum. It has many advantages such as high It is also possible to subject ordinary products to high-temperature, high-pressure treatment; these products generally have many microscopic pores inside them, and sometimes large pores that can be observed with the naked eye, but high-temperature, high-pressure treatment It is possible to completely refine or reduce these pores to the extent that they are not supported in practice, and as a result, it is possible to improve the strength, which plays a major role in eliminating casting defects and improving quality. .

These HIP devices basically consist of a high-pressure container that can tightly seal high-pressure gas, a heat insulating layer placed inside the container, and a heating device placed inside the heat insulating layer. The furnace chamber that houses the processing body is constructed, and among these components, the important one that basically controls the performance of the HIP equipment is the heat insulation layer, which is usually not used because it is under special conditions of high pressure. This requires a different insulation layer configuration from that of high-temperature furnaces. That is, in this type of device, argon gas (hereinafter abbreviated as Ar gas) is usually used as the pressure medium.
However, the viscosity of Ar gas under high temperature and high pressure is, for example, 2000 Kg/cm ² at 1450°C, only about 3.8 times that at normal temperature and normal pressure, but the heat capacity is more than 240 times higher. Although it has an extremely large heat capacity, it is highly fluid, so the amount of heat transferred by convection is extremely large.Therefore, as a heat insulating layer, it effectively prevents the high temperature gas inside the furnace chamber from flowing out of the furnace chamber. A device that suppresses heat loss is desired, and a device as shown in FIG. 1 is generally used.

That is, in the same figure, a high pressure chamber 4 is defined by a high pressure cylinder 1, an upper plug 2 and a lower plug 3 that protrude into the upper and lower openings of the cylinder to seal them, and a cylindrical heat insulating layer is provided in the high pressure chamber 4. 5 and a heating device 6 arranged inside the furnace chamber 7.
The object to be processed 13 is placed on a heat insulating seat 12 that is integrally attached to the lower plug 3, and subjected to HIP treatment in a high temperature and high pressure atmosphere within the furnace chamber 7.

In the above device, the heat insulating layer consists of two or more layers made of a material that does not have air permeability or has low air permeability, such as a stainless steel plate or a molybdenum plate, so that the gas in the furnace chamber 7 as a whole does not pass through to the outside of the furnace chamber. It is composed of an inverted top 8, 8' or a cylinder and a heat insulating material 9 such as ceramic felt for convection and radiation suppression filled between them, and is suspended in the high pressure chamber 4 by a holding member 14 on the upper plug 2. As a result, the furnace chamber and the outside of the furnace chamber are communicated only through the space surrounding the heat insulating seat 12 at the bottom of the furnace chamber, and the high temperature gas inside the furnace chamber is prevented from flowing out to the outside of the furnace chamber due to convection. It is structured as follows.

However, the heat insulating layer as described above generally has the following drawbacks.

(1) Pressure-resistant members such as high-pressure cylinders are very expensive, so it is preferable to effectively utilize the internal volume of the high-pressure chamber to improve economic efficiency, and for this purpose, it is better to make the insulation layer as thin as possible. However, there is a limit to how thin the heat insulating layer of the above structure can be made.

(2) The properties of insulation materials such as ceramic felt change over time, and their thermal insulation properties deteriorate when used for a long period of time.

(3) When processing objects containing relatively active elements such as Ti alloys and superalloys, the atmosphere inside the furnace must be clean. Insulating materials such as ceramic felt absorb water etc. at low temperatures,
It is released at high temperatures and damages the atmosphere inside the furnace.

Therefore, in order to compensate for the drawbacks of such a heat insulating layer structure, we have previously proposed Japanese Patent Application No. 55-176102 (Japanese Unexamined Patent Publication No.
No. 57-101601) has been proposed, which describes a heat insulating layer consisting of alternating layers of sheets without gas permeability and netting made of heat-resistant wire.

However, although this heat insulating layer confines high-pressure Ar gas in a narrow space to prevent convection, and stacks these layers in multiple layers to form a heat insulating layer with excellent thermal insulation, the results of subsequent studies revealed the following: It was found that there were some shortcomings such as:

That is, when using a flexible graphite sheet, the net material is preferably ceramic fiber or carbon fiber from the viewpoint of chemical stability, and carbon fiber is particularly recommended. However, these fibers are usually extremely small in diameter and are used as bundles or twisted threads, so when processing them into netting materials, it is difficult to manufacture ones with large excess mesh, and care must be taken when handling them afterwards. It takes. On the other hand, if a material with a fine mesh is used, heat loss due to heat conduction will increase, and the original purpose of heat insulation will be impaired.

Thus, the present invention focuses on the above-mentioned drawbacks when using flexible graphite sheets, and aims to improve them by confining the high-pressure Ar gas proposed above in a narrow space so as not to cause convection. By stacking these in multiple layers, we will take advantage of the advantage of obtaining a heat insulating layer with excellent thermal insulation properties, and we will also improve the heat insulating layer structure of the flexible graphite sheet to obtain an even more practical heat insulating layer. This is the purpose.

Therefore, the present invention is characterized in that an inverted cup-shaped or cylindrical heat insulating layer is placed inside a high-pressure container that encloses high-pressure gas, and a heating device is housed inside the heat insulating layer. In a hot isostatic pressing device, the heat insulating layer includes a cylindrical portion in which flexible graphite sheets are laminated in multiple layers, and the cylindrical portion is made of flexible graphite sheets having holes or holes in every other layer. A sheet and a flexible graphite sheet without holes or holes are arranged in a laminated manner, and the flexible graphite sheets without holes or holes on both sides sandwiching the flexible graphite sheet with holes or holes are in direct contact with each other. The point lies in the fact that it is assembled and configured without any problems.

Here, the sheet forming the main cylindrical part of the present invention is made of the same flexible graphite sheet as previously proposed, and the thickness of the insulation layer can be reduced in order to effectively utilize the internal volume of the furnace inside the insulation layer. Its thickness from the point of view is 0.1
~1.0mm is usually used. and,
The cylindrical portion of the present invention is constructed by arranging this in multiple layers, but unlike the net material, this cylindrical portion is a flexible graphite sheet having holes or pores (hereinafter simply referred to as holes). is interposed in every other layer, and is formed by alternately arranging flexible graphite sheets without holes and flexible graphite sheets with holes.

In this case, it is preferable that the holes of the flexible graphite sheet with holes arranged in every other layer have an average number of holes over the entire surface of the sheet,
As shown in Figures 7 and 8, the hole shape may be circular, square, or any other shape, or may be large or small, or may be a mixture of shapes. However, the area ratio occupied by the hole is determined by A preferable area ratio is selected because it is related to the insulation effect of the gap.

Regarding this point, in order to find a suitable area ratio, the hole area was varied and experimental analysis was attempted, and it was confirmed that 70 to 95% is suitable.

Figure 9 shows the results of this experiment. That is,
The figure shows the comparison results between the area ratio of each hole and the internal temperature of the high-pressure vessel when the furnace chamber internal temperature is 1900℃, the pressure is 2000Kg/cm ² , and the high-pressure vessel external temperature is 30℃. The internal temperature of the high-pressure container when rolled up is 120℃, but holes are made in every other layer.
And if the hole area ratio is gradually increased, approximately 70
The insulation effect due to the gap becomes noticeable from about %,
At about 80%, the temperature inside the high-pressure vessel becomes 100℃.

This means that it is better to make the area occupied by the holes as large as possible.However, as mentioned above, the sheet is thin at 0.1 to 1.0 mm, so it is difficult to manufacture it with such holes. is extremely difficult.

Therefore, it is appropriate that the upper limit is at most 95%, and as mentioned above, the preferred range is 70 to 95%.

Note that the cylindrical part made of alternating layers of flexible graphite sheets with holes and flexible graphite sheets without holes is created by using a long flexible graphite sheet without holes and a flexible graphite sheet with holes. The easiest and most common method is to overlap long flexible graphite sheets and simultaneously wind them.

However, in order to improve the roundness of the cylindrical part and the overall mechanical strength, a cylindrical core material made of graphite or carbon-carbon fiber composite material may be placed inside the cylindrical part. The superimposed flexible graphite sheet is spirally wound to form a material.

Formation of the cylindrical part by polymerization and winding in this manner is not limited to the width of the flexible graphite sheet, and has the advantage of producing a long-axis cylindrical heat insulating layer. Moreover,
The shape of these cylindrical parts can be easily stabilized by binding the outermost periphery with bundles of carbon fibers.

Of course, the cylindrical part may form the entire structure of the heat insulating layer, but it may also be incorporated into a part of the heat insulating layer, or the cylindrical part arranged in multiple layers may be divided in the radial direction, Alternatively, it is also possible to stack them vertically in multiple stages to form a cylindrical or inverted cup-shaped heat insulating layer.

Further, as a means for forming holes in the flexible graphite sheet, known perforation means such as punching and cutting can be used as appropriate, and a suitable means may be used depending on the shape of the hole. To provide holes in a long flexible graphite sheet, a large number of holes are punched at intervals of πD (where D is the diameter of the outermost surface of the cylindrical portion) and used for winding.
(See Figures 7 and 8) The above description relates to the cylindrical part and the case where the heat insulating layer communicates with the high pressure chamber at the top or bottom end of the cylinder. In this case, the upper end of the cylindrical heat insulating layer is covered by the upper lid part.

In this case, it is also desirable to use a heat insulating layer in the upper lid part that is made up of alternately laminated flexible graphite sheets with holes similar to those in the cylindrical part and flexible graphite sheets without holes. It is.

Thus, in the cylindrical part mentioned above, each gap in the flexible graphite sheet is maintained at the required gap by the perforated sheet arranged every other layer, and each gap is filled with a pressure medium gas, for example, Ar gas. It will be done. Usually, Ar
Although gas has an extremely large heat capacity, its viscosity is extremely low, so the amount of heat transferred by convection is large.
Therefore, the structure of the heat insulating layer must be able to efficiently suppress heat dissipation due to radiation as well as convection transfer.

However, the heat transfer coefficient of high-pressure Ar gas itself is
Extremely small, e.g. 1.24 at 1000Kg/cm ² and 400℃
×10 ^-4 cal/cm・sec°C, which is only 1/60 of the heat transfer coefficient in the thickness direction of a flexible graphite sheet.

Therefore, it is extremely effective to confine high-pressure Ar gas in a narrow space so as not to cause convection, and then stack multiple layers of this in order to obtain a heat insulating layer with excellent thermal insulation properties.

The amount of heat transfer due to the convection of Ar gas in the gap between the two sheets is determined by the gap distance, the temperature difference between the inner and outer sheets, and the physical properties of Ar gas such as thermal conductivity, thermal expansion coefficient, density, and viscosity, but it can be determined arbitrarily. pressure,
By setting the gap interval to a certain value or less with respect to the temperature difference between the inner and outer sheets, convection virtually does not occur, and heat transfer between the inner and outer sheets is only through the thermal conductivity of Ar gas and radiant heat. In this respect, the heat insulating layer of the present invention, in which the distance between the inner and outer sheets is kept to the sheet thickness of 1 mm or less, can obtain sufficient thermal insulation.

Furthermore, if a flexible graphite sheet with holes and the same sheet without holes are stacked one on top of the other, the top and bottom ends will be open, and Ar gas will flow from the bottom to the top, resulting in sufficient thermal insulation. In some cases, this may not be possible, or the upper end of the cylindrical portion may reach a high temperature, causing the upper part of the high-pressure cylinder to rise in temperature. Therefore, in order to avoid this, it is very effective to take measures such as airtightly connecting the upper end through a ring or the like, or opening the upper end and making the lower end airtight.

Hereinafter, embodiments of the present invention will be described with further reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to these examples, and can be modified as appropriate without departing from the purpose.

FIG. 2 shows a cross section of one heat insulating layer in the present invention, and FIG. 3 is an enlarged view of the main part (part A).

In these figures, a high pressure cylinder 1, an upper plug 2,
Inside the high-pressure chamber 4 of the high-pressure container defined by the lower plug 3, a cylindrical heat-insulating layer 16 including the cylindrical portion, which is a main part of the present invention, is air-tight by an upper lid portion 9' filled with a heat-insulating material 17 and a connecting member 20. and is suspended from the upper plug 2 via a metal fitting 14.

Here, the details of the cylindrical heat insulating layer 16 are as follows.
As shown in the figure, a flexible graphite sheet 21,
The cylindrical portion consists of flexible graphite sheets 22 with window-shaped holes arranged alternately, with one layer between each layer.
A void 23 is formed in each layer.

Generally, as mentioned above, the heat transfer coefficient within the heat insulating layer used in a HIP device is a complex one in which the heat conduction of the sheet material, the heat radiation between the sheet materials, and the convection of the pressurized gas overlap. The heat insulating layer having the structure shown in FIGS. 2 and 3 has the effect of sufficiently suppressing heat transfer.

That is, regarding heat conduction, the thermal conductivity of the flexible graphite sheet in the direction perpendicular to the surface is 0.00872 cal/cm.
Since the temperature is about sec° C., which is very small compared to normal graphite material, the amount of heat that escapes through the third sheet polymerization portion 24 by conduction is small. On the other hand, thermal radiation can be suppressed very efficiently by stacking multiple layers, since the emissivity of flexible graphite sheets is as low as 0.6 even at high temperatures of about 1700°C.

In addition, the natural convection of the pressure medium gas causes the gap 23 to
By making the gap extremely narrow (1.0 mm), it is possible to suppress most of the heat, and the amount of heat dissipated is comparable to the heat conduction of the pressure gas itself.

Moreover, the structure of the example illustrated above also exhibits the following advantages. That is, since the flexible graphite sheet has an extremely small coefficient of thermal expansion in the plane direction of about 1×10 ^-6 /°C, the temperature difference between the innermost part and the outermost part of the cylindrical heat insulating layer 16 occurs. The amount of deformation is small.
In addition, since the coefficient of friction is small, slippage occurs between each layer, so the entire structure does not deform significantly.

In this way, each of the above-mentioned effects is brought about by the cylindrical part made of a multilayer structure of flexible graphite sheets, and because it does not have a mesh material such as a heat-resistant wire material, it is difficult to handle.
There is no need to worry about increased heat loss, and the industrial benefits are enormous.

FIG. 4 shows a modification of the heat insulating layer shown in FIG. 2, in which the heat insulating layer is divided into three cylindrical blocks in the radial direction.

This configuration has the effect of further suppressing the overall deformation due to temperature differences between inside and outside, and also increases the cooling rate during cooling by removing the inner block as appropriate when the operating temperature is low. This makes it possible to shorten cycle time.

Furthermore, in FIGS. 5 and 6, a cylinder 25 made of graphite or a carbon-carbon fiber composite material is arranged as a core material inside a cylinder made of a flexible graphite sheet, and this arrangement improves roundness. , and the overall mechanical strength can of course be improved.

In particular, Figure 5 shows that the heat insulating cylindrical layer itself is
The same structure as shown in the figure is adopted, but in addition, the upper lid part 9' at the top of the cylindrical part is also made by alternately laminating ring-shaped flexible graphite sheets with holes and ring-shaped flexible graphite sheets without holes. A multilayer structure is applied, which efficiently suppresses heat dissipating upward from the upper lid portion 9' in the high pressure chamber 4, making the heat insulation effect more effective.

Further, in this case, when the insulation material is filled with a general ceramic fiber, there is an advantage that it can be used stably for a long time without aging due to crystallization of the material.

Note that the laminated structure of the ring-shaped flexible graphite sheets described above can be similarly applied to the heat insulating seat 12 shown in FIG.

On the other hand, in the example shown in FIG. 6, the cylindrical portions 25' are stacked in two layers, upper and lower, and a graphite ring 26 is interposed between them. In each of the above embodiments, the gap 23 communicates with the high pressure chamber 4 at the upper end or lower end of the cylindrical part, but this is done so that the pressure medium gas in the gap 23 enters and exits during pressurization and depressurization. This is to prevent damage to the cylindrical heat insulating layer due to pressure difference.

If it is limited to either the upper end or the lower end, there is no risk of loss of thermal insulation.

Each of the embodiments has been described above, but in each of the above examples, due to the heat insulating layer structure consisting of multiple layers of flexible graphite sheets, not only the conventional heat insulating layer but also
It is also possible to form a heat insulating layer structure with higher practical effects even when a flexible graphite sheet and a net material are combined.

As described above, the device of the present invention is a sheet in which a cylindrical portion constituting a heat insulating layer is formed by arranging multiple layers of flexible graphite sheets, and holes are formed in every other layer of the flexible graphite sheet. Therefore, it is easy to add sheets if the width or length is insufficient, and the contact area between adjacent sheets is small, so there is no reduction in insulation properties due to heat conduction. By using a sheet with holes, there is no direct contact between the sheets on both sides, which makes it easy for gas to flow in and out, and there is no pressure difference between the inside and outside of the insulation layer, so there is no risk of deformation or destruction of the insulation layer, etc. In addition, the thin flexible graphite sheet has excellent thermal insulation properties, and an extremely thin heat insulating layer can be obtained, making the equipment more compact, making effective use of the internal volume of the high pressure chamber, and reducing the diameter of the high pressure vessel. In addition, since it does not use ceramic fibers that deteriorate significantly over time, the atmosphere inside the furnace is kept clean, and the layers are easy to slip and are less likely to deform due to differences in thermal expansion, increasing durability through long-term stable use. This method is expected to bring great benefits to future processing by increasing the industrial applicability of HIP equipment, including the processing of materials containing active elements.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view showing a conventional HIP device, Figure 2
The figure is a partially omitted vertical sectional view of the internal structure of an example of the HIP device according to the present invention, FIG. 3 is an enlarged view of section A in FIG. 2, and FIGS. 4 to 6 are modifications of the device of the present invention. Figure 2 is a vertical cross-sectional view with the same internal structure partially omitted, Figures 7 and 8 are explanatory diagrams of sheets with holes, and Figure 9 shows the heat insulation effect due to changes in the area ratio of the sheet holes. This is a diagram representing 1...High pressure cylinder, 2...Upper plug, 3...
...Lower plug, 4...High pressure chamber, 5...Insulation layer, 6
... Heating device, 9' ... Upper lid part, 16 ... Heat insulation layer,
21... Flexible graphite sheet without holes, 22...
... Flexible graphite sheet with holes, 23 ... voids,
25... Core material cylinder.

Claims (1)

[Claims] 1. A hot isostatic press device in which an inverted cup-shaped or cylindrical heat insulating layer is arranged in a high-pressure container that encloses high-pressure gas, and a heating device is housed inside the heat insulating layer, At least the heat insulating layer includes a cylindrical part in which flexible graphite sheets are arranged in multiple layers, and the cylindrical part has a structure in which the flexible sheets have holes or holes in every other layer, and A hot isostatic press apparatus characterized in that flexible graphite sheets on both sides sandwiching the flexible graphite sheet having the holes or holes are assembled without directly contacting each other. 2. The hot isostatic press apparatus according to claim 1, wherein the cylindrical part in which flexible graphite sheets are arranged in multiple layers is divided into a plurality of parts in the radial direction. 3. The cylindrical part in which flexible graphite sheets are arranged in multiple layers overlaps a long flexible graphite sheet with no holes or holes and a long flexible graphite sheet with holes or holes, and simultaneously A hot isostatic press device according to claim 1 or 2, which is formed by winding. 4 Claims 1, 2, or 3, in which the outermost surface of a cylindrical portion made of multilayered flexible graphite sheets is fixed by binding with a bundle of carbon fibers.
The hot isostatic press apparatus described in . 5. Claims 1 to 4, wherein a cylinder made of graphite or a carbon-carbon fiber composite material is disposed as a core material inside a heat insulating layer including a cylindrical part made of multiple layers of flexible graphite sheets. A hot isostatic press apparatus according to any one of the following items. 6 Among flexible graphite sheets, the area of holes or holes in sheets with holes or holes is 70 to 95% per layer.
A hot isostatic press apparatus according to any one of claims 1 to 5. 7. The hot isostatic press apparatus according to any one of claims 1 to 6, wherein the flexible graphite sheet has a thickness of 0.1 to 1.0 mm. 8. The heat insulating layer is arranged in an inverted cup shape, and the upper lid part thereof, like the cylindrical part, alternately laminates flexible graphite sheets with holes or holes and flexible graphite sheets without holes or holes. A hot isostatic press apparatus according to any one of claims 1 to 7, having an inverted pot-shaped heat insulating layer formed by.