JPH06345545A - Production of capsule for hot isostatic pressing - Google Patents

Abstract

PURPOSE:To obtain a capsule for hot isostatic pressing excellent in airtightness by placing a body to be treated consisting essentially of a ceramic in tantalum foils having a specified thickness and diffusion-joining the inlet with a seam welding means using a specified electrode. CONSTITUTION:The powder material consisting essentially of a ceramic or a powder compact 8 is placed into a bag 5 consisting of tantalum foils 6 having 30-300mum thickness from its inlet 7. The bag 5 is then evacuated, and the two tantalum foils 6, 6 are clamped by electrode rolls 9, 9 made of a metallic material contg. >=90% of at least one between molybdenum and tungsten. The bag is pressed and energized, the rolls 9, 9 are moved in direction of the arrow, hence the inlet 7 is seam-welded, and a capsule 10 for hot isostatic pressing is produced. Consequently, the capsule 10 excellent in airtightness is produced, and hot isostatic pressing is conducted at a high temp. of >=1400 deg.C and a high pressure by using this capsule 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to hot isostatic pressing (HI).
P) The present invention relates to a method for producing a capsule used for treatment, and particularly relates to a method for producing a capsule for HIP treatment performed at a high temperature of 1400 ° C. or higher, such as production of a thin plate-shaped sintered member such as a cutting tool and a sputtering target material. .

[0002]

2. Description of the Related Art In recent years, as a cutting tool, a sputtering target material, etc., a ceramic material or a composite material thereof has been used more and more. In order to sufficiently sinter the ceramic-based member or the composite material thereof with high density, it is necessary to carry out HIP treatment at high temperature and high pressure.

The HIP treatment is a method of encapsulating an object to be treated such as a powder or a powder compact in a capsule and applying a high fluid pressure at a high temperature to sinter the object to high density. In the case of the HIP method, 1000-2000 kgf /
It is possible to apply a large pressure such as cm ² . As a HIP method capable of efficiently manufacturing even thin plate-shaped members and small parts without being deformed into a distorted shape, Japanese Patent Application Laid-Open No. Hei 3
-94002 and JP-A-4-99207,
A method of using a foil capsule formed by forming a metal foil having a thickness of 30 to 300 μm in a bag shape has been proposed. The foil capsule is a bag-like body in which three sides of two metal foils such as stainless steel, titanium, and tantalum are joined by YAG laser welding, TIG welding, or seam welding means, and the remaining one side corresponds to the opening. After being formed, the powder or powder molded product as the object to be processed is housed in the bag-shaped body, the inside is deaerated in vacuum, and the opening is joined and sealed by the welding means. The HIP method using a foil capsule has an advantage that the isotropic pressure treatment can be effectively performed on the object to be processed because the rigidity of the capsule itself is very small.

[0004]

However, when stainless steel or titanium is used as the material of the foil capsule, the melting point of these materials is as low as 1400 ° C. or lower, so that it cannot be used for HIP treatment at 1500 ° C. or higher. Tantalum can be used because it has a high melting point of about 3000 ° C., but there are the following problems with respect to the joining of tantalum foils that is performed when manufacturing capsules.

That is, in YAG laser welding, since it is necessary to press the foil without a gap, the structure of the apparatus becomes complicated, and it is generally difficult to press the foil evenly over the entire length of the metal foil with a thickness of 100 μm or less. In addition to the above problem, there is also a problem that the laser is reflected due to the light reflectivity of tantalum and welding cannot be performed well. Further, TIG welding is a method in which an arc is generated between the foil and the electrode while flowing an inert gas to perform welding, but since tantalum is easily oxidized, the TIG welding is performed in an inert gas atmosphere, but the arc is used. Oxidation of tantalum foil due to irradiation cannot be sufficiently prevented. Furthermore, it is difficult to weld a thin foil of 30 to 300 μm in an airtight manner. Therefore, it is difficult to manufacture a tantalum foil capsule having excellent airtightness by TIG welding.

On the other hand, seam resistance welding is a method of welding by energizing two tantalum foils 2 and 2 with a disc electrode 1 while applying pressure, as shown in FIG. Heat is generated due to the contact resistance when energized and the resistance of the tantalum foil 2 itself, the joining surface is melted to form a nugget, and the current is continued while rotating the disc electrode 1, so that the nuggets are overlapped over the entire length. To be joined. The seam welding means for joining in this manner is not affected by the oxidizable property of tantalum and the light reflectivity. However, since a roll made of a copper alloy is generally used for the disc electrode 1, there are the following problems. That is, since tantalum generally has a property of being easily alloyed with copper, copper used in the electrode is alloyed with the tantalum foil, and it becomes difficult to wind the tantalum foil 2 around the electrode 1 and continue welding. Even if welding can be done without winding, the copper alloy that is a component of the electrode 1 adheres to the surface of the tantalum foil 2 in contact with the electrode 1, and the adhered part melts during HIP treatment at 1100 ° C or higher, causing capsule damage. Cause of. For this reason, even if a capsule can be produced by seam welding using a copper electrode, it is necessary to produce a ceramic-based sintered member.
At present, it cannot be used for HIP treatment at 00 ° C. or higher.

The present invention has been made in view of the above technical background, and an object of the present invention is to solve the problems existing in producing a tantalum foil capsule and to provide a ceramic-based object to be processed. HIP processing conditions required for sintering and joining, that is, HI of 1400 ° C or higher
It is to provide a method of manufacturing a foil capsule that can withstand P treatment.

[0008]

A method of manufacturing a capsule for hot isostatic pressing according to claim 1, wherein a powder raw material or a powder compact containing ceramic as a main component is processed into
A first step of housing in a tantalum foil having a thickness of 0 to 300 μm; a second step of producing a capsule by encapsulating the object to be treated in the tantalum foil by bonding the tantalum foil, and a second step; The joining is performed by diffusion joining by seam welding means using an electrode made of a metal containing 90% or more of at least one of molybdenum and tungsten.

According to a second aspect of the present invention, there is provided a method of manufacturing a capsule for hot isostatic pressing, in which an object to be treated such as a powder raw material or a powder compact containing ceramic as a main component is tantalum having a thickness of 30 to 300 μm. A first step of accommodating in a foil; a second step of producing the capsule by encapsulating the object to be treated in the tantalum foil by joining the tantalum foil, and
The joining is characterized in that the metal foil containing 90% or more of at least one of molybdenum and tungsten is interposed between the tantalum foil and the electrode to perform diffusion joining by seam welding means.

[0010]

Function: Molybdenum and tungsten are high-conductivity and high-melting-point metals. When an electrode of the seam welding means is made of a metal material containing 90% or more of at least one of molybdenum and tungsten, and when electricity is applied to the electrode,
The electrodes do not melt or alloy with the tantalum foil even when the temperature of the joint becomes high due to resistance heating. Therefore, in the method of the first aspect, since seam welding is performed using the electrode made of such a metal, the joint portion of the tantalum foil can be pressed at high temperature without alloying with the tantalum foil. Since the two tantalum foils are diffusion-bonded at high temperature and high pressure, it is possible to manufacture a capsule having excellent airtightness.

According to the second aspect of the present invention, even if a copper electrode is used, the metal foil composed of the above metal interposed between the tantalum foil and the electrode is an alloy of the tantalum foil and the copper electrode. Of carbonization and adhesion of tantalum foil to copper electrodes. Therefore, the joint portion of the tantalum foil can be brought to a high temperature and high pressure state, and a highly airtight capsule can be manufactured by diffusion joining.

By using a tantalum foil capsule having a high airtightness and a high melting point metal, it is possible to carry out a high temperature and high pressure HIP treatment which could not be performed with a conventional stainless steel foil or the like.

[0013]

The present invention has solved the problem of joining means that occurs during the production of tantalum foil capsules by utilizing the property of tantalum that facilitates diffusion joining, and has completed the present invention. Hereinafter, a method for producing the hot isostatic pressing capsule of the present invention will be described with reference to FIG.

In FIG. 1 (a), 5 is a bag-like body for producing a metal capsule for HIP processing, in which two rectangular tantalum foils 6, 6 leave a bag inlet 7 on one side, The remaining three sides are joined to each other by seam welding means described below. In the bag-shaped body 5 as described above, the object 8 to be processed is placed in the bag inlet 7
Store more. After that, the bag-shaped body is vacuum-degassed (see FIG. 1).
(See (b)) Two tantalum foils 6 and 6 are sandwiched between electrode rolls 9 and 9 and are energized while being pressurized, and the rolls 9 and 9 are moved in the direction of the arrow to form a bag as an opening. The inlet 7 is seam welded (see FIG. 1 (c)). Figure 1
(D) shows the foil capsule 10 thus airtightly manufactured.

The tantalum foil 6 used in the present invention has a thickness of 30 to 300 μm, and is appropriately selected within the above range from the flexibility, plastic deformability and cutting strength of the foil material.
If the thickness is less than 30 μm, the welded portion is likely to have a defect, and it is difficult to weld hermetically. On the other hand, the thickness is 3
This is because if it exceeds 00 μm, the capsule will be distorted during HIP processing, and it will be difficult to efficiently collect the object 8 to be processed.

It should be noted that it is preferable to apply a ceramic-based release material such as boron nitride to the inside of the capsules of the tantalum foils 6, 6. This prevents the target object 8 and the capsule 10 from adhering to each other during the HIP process, and
This has the effect of facilitating the removal of the capsule 10 after IP treatment. The three sides of the bag-shaped body 1 and the bag inlet 7 are joined using seam welding means as follows.

As a method for joining the electrodes 9 and 9 and the tantalum foils 6 and 6 without alloying them, the electrode 9 is made of a material which is difficult to alloy with the tantalum foil 6, or the electrode 9 is used. There is a method according to claim 2, in which a metal foil made of a high-melting point material which is difficult to alloy with the tantalum foil 6 is interposed between and the tantalum foil 6.
Hereinafter, the metal foil used for interposition is referred to as "intervening metal foil".

In the method of claim 1, as the electrode 9, a material having a high conductivity so as to generate sufficient resistance heat and a material which does not alloy with the tantalum foil, specifically, at least one of molybdenum and tungsten is used. An electrode composed of a pure metal material or an alloy material containing 90% or more is used.
This is because the melting point of the above material used for the electrode is as high as 2000 ° C. or higher and the conductivity is as high as about 30%. Other materials may be contained as long as the content of molybdenum and / or tungsten is in the above range. As another material, a material that does not extremely reduce the conductivity of molybdenum or tungsten, for example, titanium, zirconium, carbon, or the like can be contained.

In the method of claim 2, that is, in the method of joining by using the metal foil for inclusions, the electrode material may be any material capable of generating sufficient resistance heat. Therefore, it is possible to use chromium copper, pure copper, or the like, which is a conventional electrode material having a high dielectric constant. Examples of the metal used for the intervening metal foil include refractory metals that are difficult to alloy with both the electrode and the tantalum foil, such as tungsten and molybdenum. The thickness of the intervening metal foil is sufficient as long as it can prevent direct contact between the electrode and the tantalum foil.
0-100 μm is preferably used.

FIG. 2 shows a method of seam welding using an intervening metal foil. A tungsten foil is sandwiched between the tantalum foil 6 and the copper electrode roll 9 as an intervening metal foil 11. The tungsten foil 11 prevents alloying between the copper electrode 9 and the tantalum foil 6, and generates heat due to the contact resistance between the electrodes 9 and 9 and the tantalum foil 6 and the inclusions 10.

In any of the above methods, the electrodes 9, 9
When electricity is applied to the space, the temperature of the joint becomes high and the tantalum foil 6 is being pressed by the pair of upper and lower electrode rolls 9, 9. Under such high temperature and high pressure, the tantalum foil, which is easily diffusion-bonded, is diffusion-bonded without melting at the bonding surface. In any case, the seam welding operation is preferably performed under vacuum or in an inert gas atmosphere from the viewpoint of preventing the oxidation of tantalum.

The foil capsule 1 manufactured as described above
In No. 0, since the bonding portion is diffusion bonded, high airtightness is ensured and it is possible to withstand HIP treatment at high temperature and high pressure. Therefore, by using the capsule 10 manufactured by the method of the present invention, it is possible to manufacture a sintered member that must be HIP processed at a high temperature of 1400 ° C. or higher. Therefore, as the object 8 to be processed, non-oxide ceramics such as silicon nitride and silicon carbide, composite ceramics of non-oxide ceramics and oxide ceramics such as alumina,
It is also possible to use a powder or a powder compact made of a non-oxide ceramics or a composite material obtained by composite-reinforced non-oxide ceramics with a whisker such as metal or non-metal.

The HIP processing conditions when the capsule 10 manufactured according to the present invention is used can be appropriately selected within the following range. The HIP processing temperature can be as high as 2200 ° C., and within the temperature range, the object to be processed 8
Can be appropriately selected depending on the type. For example, a suitable HIP treatment temperature is about 1400 to 1600 ° C. for alumina system and about 1700 to 2000 ° C. for silicon nitride and silicon carbide system. HIP processing pressure is also 1000-2000 kgf / cm
^It can be appropriately selected within the range of ² depending on the type of the object 8 to be processed.
The holding time is appropriately selected depending on the size of the object to be processed and the thermal conductivity, but is usually 1 to 5 hours.

In the case of the object 8 to be treated, which has a large amount of adsorbed gas and is likely to generate this adsorbed gas during the HIP process, a titanium foil and a zirconium foil together with the object 8 to be treated are encapsulated.
It is preferable to put in 0 and encapsulate. The titanium foil and the zirconium foil react with the gas generated from the object to be treated 8 to prevent the gas generated from reacting with the tantalum foil 2, and the tantalum foil 2 loses its ductility due to carbonization, oxidation, etc. This is because it can be prevented from functioning as. For the same reason, it is preferable to wrap a titanium foil or a zirconium foil outside the capsule 10 to prevent the reaction between impurities and the like in the pressure medium gas at the time of HIP treatment and the tantalum foil.

After the HIP process, the capsule 10 taken out of the HIP device is fragile even if recrystallized due to the HIP process, so it can be removed by tapping it lightly with a hammer or the like, and the object 8 to be processed can be taken out easily. be able to. [Specific Examples] Example 1; Alumina-silicon carbide composite ceramic powder was molded into a shape of 30 mm x 30 mm x 5 mm at a molding pressure of 1 ton / cm ^{2 as} a target object, and then pre-baked. A ceramic molded body from which the binder was removed by binding was used.

Two 50 μm-thick tantalum foils were cut into a 100 mm square shape, and three sides of the foils were overlap-bonded by seam welding to form a bag.
As the seam welding conditions, an electrode made of pure molybdenum under vacuum is used, the electrode pressure is 12.5 to 14 kg, and the welding current is 27.
The welding speed was 50 A and the welding speed was 1.5 m / min. Then, the ceramic molded body was inserted together with the zirconium foil into the opening of the bag-shaped body. After the bag-shaped body was deaerated, the opening was diffusion-bonded using the seam welding means under the same conditions as above, and the object was vacuum-sealed to produce a capsule.

FIG. 3 shows 50 times (FIG. 3 (a)) and 100 times (FIG. 3) the tantalum foil joint portion of the prepared capsule.
The optical microscope photograph of (b)) is shown. From these photos,
It can be seen that in the polished state (no etching), the two tantalum foils are joined together without a gap. This tantalum foil capsule was converted into H ₂ SO ₄ : HNO ₃ : HF: H ₂ O = 3: 2:
Immersion treatment was performed in an etching solution prepared by mixing at a ratio of 4:10. 4A and 4B are 50 × and 100 × optical micrographs of the tantalum foil joint portion after etching.
Shown in. As can be seen from FIG. 4, no metal melt structure was observed at the joint. There is a slight gap between the upper and lower two metal foils, but this is because the oxide film on the foil surface was removed by the etching process, and it does not indicate that there is any hindrance to the bonding state. .
Other parts of the foil showed similar cross sections. From this, it was confirmed that the bonded portion was in a favorable diffusion bonding state.

Then, the foil capsule prepared as described above is placed in a HIP device, and the temperature is 1500 ° C. and 2000 kgf / c.
HIP treatment was performed at m ² for 1 hour. After the HIP treatment, the capsules were removed and the object to be treated was taken out. As a result, it was possible to obtain a ceramics sintered body that was sintered to a substantially true density without density unevenness.

[0029]

According to the capsule manufacturing method of the present invention, it is possible to manufacture a capsule having excellent airtightness, which is joined without any gap using tantalum foil which is a high melting point material. Therefore, by using the capsule manufactured by the method of the present invention, it becomes possible to perform HIP treatment at a high temperature and pressure of 1400 ° C. or higher, which is not possible with conventional capsules such as stainless steel, and it is possible to perform non-oxide ceramics and whiskers It is possible to manufacture a thin plate-shaped sintered body made of a composite material or the like with ceramics. Therefore, by using the capsule manufactured by the method of the present invention, it is possible to manufacture a sputtering target, a blade-shaped tool, a grindstone, etc., which is a thin plate-shaped sintered member made of ceramics, which has been in increasing demand in recent years. Become.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a capsule manufacturing method of the present invention.

FIG. 2 is a drawing for explaining the manufacturing method according to claim 2;

FIG. 3 is a micrograph showing a metal structure of a joint portion of the capsule manufactured in Example 1.

FIG. 4 is a micrograph showing a metal structure of a joint portion of the capsule manufactured in Example 1 after etching.

FIG. 5 is a diagram for explaining seam welding means.

[Explanation of symbols]

 5 Bag-shaped body 6 Tantalum foil 8 Object to be treated 9 Electrode 10 Capsule 11 Metal foil for interposition

Claims (2)

[Claims] 1. A first step of accommodating an object to be treated such as a powder raw material or a powder compact having ceramics as a main component in a tantalum foil having a thickness of 30 to 300 μm; the object to be treated in the tantalum foil. And a second step of producing a capsule by encapsulating the tantalum foil by joining, and the joining is an electrode made of a metal material containing 90% or more of at least one of molybdenum and tungsten. A method for producing a capsule for hot isostatic pressing, characterized in that diffusion bonding is performed by seam welding means using. 2. A first step of accommodating an object to be treated such as a powder raw material or a powder compact containing ceramics as a main component in a tantalum foil having a thickness of 30 to 300 μm; the object to be treated in the tantalum foil. And a second step of manufacturing by encapsulating the tantalum foil by bonding to form a capsule; and the bonding is performed by applying 90% or more of at least one of molybdenum and tungsten between the tantalum foil and the electrode. A method for producing a capsule for hot isostatic pressing, characterized in that diffusion bonding is performed by seam welding means with a metal foil contained therein interposed.