JPH05179307A - Isostatic pressing method - Google Patents

Abstract

PURPOSE:To easily obtain a densified product by sealing a body to be treated in a capsule made of specified metallic foil, subjecting the body to isostatic pressing and removing the capsule after embrittlement by oxidation or nitriding treatment. CONSTITUTION:A body 1 to be treated is sealed in a capsule 2 made of metallic foil 3 of 0.05-0.3mm thickness. The metal is Fe, Ti, Ta or Zr. The body 1 is then subjected to hot isostatic pressing and the capsule 2 is treated in an oxidizing or nitriding atmosphere. The capsule 2 embrittled by this oxidation or nitriding treatment is removed by blowing particle dispersed gas 12 or liq.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for performing sintering or diffusion bonding by encapsulating an object to be treated such as powder or powder compact or diffusion bonding material in a metal capsule and applying isotropic pressure. In particular, the present invention relates to a method for simplifying the removal of capsules after isotropic pressure treatment.

[0002]

2. Description of the Related Art Among the isotropic pressing methods, the hot isotropic pressing method (HIP method), in which a high-pressure fluid is used as a pressure medium at a high temperature, is called a hot isostatic pressing method. It is spreading as a density sintering technology or a diffusion bonding technology for metals and ceramics. Here, when performing high-density sintering or diffusion bonding by the HIP method, a container made of an airtight material (hereinafter, this container is referred to as a capsule) is covered with a container so that the pressure medium does not enter the object to be processed. After enclosing the processing body, it is necessary to perform high temperature and high pressure processing. For example, powder high speed steel billets and chromium sputtering targets are manufactured by this method.

By the way, in the HIP method using a capsule, the material and shape of the capsule are technically very important. When the HIP method is classified based on the type of capsule, a method using a coating technique such as plating,
It can be classified into a method using a glass container and a method using a metal container such as steel and copper. However, the method
Both have the following problems.

Although a thin and airtight capsule can be formed in principle by a coating method such as plating or PVD, when the object to be treated is a porous molded article, pinholes are easily generated in the coating film, which is sufficient. Airtightness cannot be secured. In addition, after the HIP treatment, it is necessary to perform pickling in order to remove the plating coating film, which is troublesome.

With glass capsules, it is easy to remove the capsules after the HIP treatment, but since glass is a brittle and fragile material, it is very difficult to pressurize and handle the HIP treatment. Since the metal capsule can secure airtightness by welding and is a strong material, it is applied to the production of powder high-speed steel and chromic sputtering target.
The metal capsule is usually composed of a metal plate or a pipe having a thickness of 1 to several mm because of the workability of welding and the ease of manufacturing the capsule itself. However, the capsule thus constructed had to be scraped off with a lathe or the like after the HIP treatment.

As a means for solving the above-mentioned problems relating to metal capsules, Japanese Patent Laid-Open No. 3-94002 proposes a method of using a metal foil having a thickness of 30 to 300 μm as a capsule. The metal foil capsule can be cut off with a metal scissors or the like without using a lathe for removing the capsule after the HIP treatment.

[0007]

However, this metal foil capsule also has a problem that it requires a great deal of labor for cutting and stripping, and that the capsule waste after removal is bulky, and the post-treatment is troublesome. .. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an isotropic pressing method that solves the problems of metal foil capsules.

[0008]

The isotropic pressing method of the present invention comprises:
In the isotropic pressurization method in which the object to be processed is enclosed in a metal capsule and isotropically pressure-treated, the capsule is oxidized or nitrided after the isotropic pressure treatment, and then converted into an oxide or a nitride. To remove. As the capsule,
It is preferable to use a metal foil containing any of iron, titanium, tantalum, and zirconium as a main component and having a thickness of 0.05 to 0.3 mm.

[0009]

The present invention is a method of isostatically pressing a metal foil made of a material that can be easily removed by oxidation or nitriding as a capsule. By using a thin-walled foil capsule, the entire capsule can be easily oxidized or nitrided. Then, the capsules used in the method of the present invention are converted into brittle oxides or nitrides by oxidation or nitriding treatment, and fine cracks are generated due to volume change due to oxidation or nitriding reaction. Such brittle, cracked capsules are easily removed.

[0010]

EXAMPLE A HIP method utilizing the method of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an object to be processed that is amenable to the HIP method, and examples thereof include powders and powder compacts that are difficult to sinter, and metals and ceramics members that are to be diffusion bonded.

First, the object 1 to be processed is housed in a capsule 2 (FIG. 1 (a)). Here, the capsule 2 is made of iron, titanium,
Two metal foils 3a, 3b containing tantalum or zirconium as a main component and having a thickness of 0.05 to 0.3 mm
Are lap-welded. It is preferable to apply a ceramic-based release agent to the inside of the capsule 2 in advance. The mold release material is the object to be processed 1 in the HIP process.
It is possible to prevent sticking and reaction between the inside of the capsule 2 and the inside of the capsule 2, and to facilitate the capsule removing step after the subsequent oxidation or nitriding. 5
Is the opening of the capsule 2.

After inserting the vacuum degassing pipe 6 into the opening 5, the opening 5 and the pipe 6 are airtightly bonded with an adhesive or the like (FIG. 1 (b)). Then, a vacuum hose is connected to the vacuum degassing pipe 6 and the inside of the capsule 2 is evacuated to evacuate the target object 1 into the capsule 2. Then, in the capsule 2, the inside of the opening 5 is slightly overlapped and welded, and then the opening 5 side is cut (FIG. 1C). In FIG. 1C, 7 is a welding line, and 9 is a cut portion. FIG. 1 shows a state after the unnecessary portion is cut, that is, a state in which encapsulation of the target object 1 into the capsule 2 is completed.
It shows in (d).

The object 1 to be processed encapsulated is HIP
It is put in an apparatus and subjected to HIP treatment (FIG. 1 (e)). HI
The conditions for the P treatment are appropriately selected depending on the type of the target object 1. After the HIP process, the capsule 1 is kept in the capsule 2 and the capsule 2 is exposed to an oxidizing or nitriding atmosphere.
Oxidation or nitriding is performed (FIG. 1 (f)). The oxidation or nitriding method is not particularly limited, but the simplest method is heating in the air or a nitrogen atmosphere (such as ammonia or a mixed gas of hydrogen and nitrogen). For example, titanium and tantalum are easily oxidized by heating to about 500 ° C. or higher in the atmosphere. In addition, nitriding can be performed at a relatively low temperature in an ammonia-based gas atmosphere.

Oxidation or nitridation of the capsule 2 by a suitable method facilitates the removal of the capsule. This is because the oxide or nitride of the constituent material of the capsule 2 is generally brittle, and moreover, minute cracks are generated due to the volume change due to the oxidation or nitriding reaction. Next, the oxidized or nitrided capsule 2 is removed. As a method of removing the capsule 2, a method of spraying and dropping a liquid such as air or water in which powder particles having an appropriate hardness are dispersed is simple and reliable.
Further, according to such a removing method, the generated capsule waste can be easily collected. FIG. 1 (g) shows an air flow 1 in which particles such as abrasive grains are dispersed by a sandblasting gun 11.
It is the figure which has sprayed 2 and has removed the capsule 2.

Since the inert gas such as argon, which is the pressure medium during the HIP treatment, often contains oxygen and nitrogen derived from the air, the capsule 2 can be treated during the HIP treatment.
HI of the above-mentioned embodiment so that the HI is not oxidized or nitrided.
It is preferable to carry out the method P by further storing the capsule 2 in a container that can be easily removed after the HIP treatment, for example, a bag made of the same material as the capsule and having a thin wall thickness.

Although the HIP method has been described in the present embodiment, the present invention is not limited to this and can be applied to the warm isotropic pressing method (WIP method).

[Specific Example] Example 1; 100 mm x 100 mm x as an object to be treated
An alternating stack of nine 0.1 mm pure copper sheets and ten stainless steel sheets was used. As a capsule,
A bag made of pure titanium foil having a thickness of 0.1 mm was used. A mold release material containing 50% alumina and 50% boron nitride was previously applied to the inner surface of the capsule.

First, after storing the object to be processed in a capsule,
A vacuum degassing pipe is airtightly attached to the opening of the capsule with an epoxy adhesive (FIG. 1 (b)), a vacuum hose is connected to the vacuum degassing pipe, and the inside of the capsule is set to 0.02.
A vacuum was drawn up to Torr (FIG. 1 (c)). After the capsule foils were brought into close contact with each other by evacuation, unnecessary portions were cut and removed by lap welding (FIG. 1 (d)).

The capsule in which the object to be treated was vacuum-sealed in this manner was subjected to HIP treatment at 1000 ° C. and 1000 kgf / cm ² for 1 hour (FIG. 1 (e)). Argon gas was used as the pressure medium. After the HIP treatment, the capsule is taken out from the HIP device and placed in an atmosphere in an electric furnace for 6 minutes.
The capsules were oxidized by heating at 50 ° C. for 30 minutes (FIG. 1 (f)). The capsule that was broken by oxidation was peeled off. The residue of the capsule attached to the object to be processed was removed by spraying corundum particles having a particle size of 30 mesh under with a sandblasting device.

The stainless steel on the surface of the object to be treated thus obtained had a matte finish and was beautiful. The joining strength between stainless steel and pure copper sheet is 8 kgf / mm.
² was almost the same as pure copper.

Example 2 As the object to be treated, it was made of alumina powder containing 30% titanium carbide and had a size of 50 × 50 × 8 m.
A molded product having m and a relative density of 70% was used. As the capsule, a bag made of 0.05 mm thick tantalum foil was used. On the inner surface of the capsule, a release material containing 50% alumina and 50% boron nitride was applied in advance to a thickness of about 0.1 mm.

As shown in FIG. 1 (a), the object to be treated is housed in a capsule, vacuum-sealed as shown in FIGS. 1 (b) to 1 (d), and then the capsule is tantalum having a thickness of 0.1 mm. It was placed in a bag and placed in a HIP device. And 1
HIP treatment was performed at 600 ° C. and 2000 kgf / cm ² for 1 hour. The tantalum bag after HIP treatment is oxidized by oxygen in the HIP pressure medium, which is argon, and turns black.
Although it was partially damaged, the internal tantalum capsule showed some oxidation coloring, but no damage or the like. The capsule was nitrided in nitrogen gas at 1200 ° C. for 20 minutes. By the nitriding treatment, the capsule turned brown and many large cracks were observed. Further, discoloration due to partial nitriding of titanium carbide was observed on the surface of the object to be treated.

When the object to be treated in such a state was sandblasted together with the capsule to remove the discolored portion on the surface of the capsule and the object to be treated, a beautiful product was obtained. The product was densified to almost true density.

Example 3 Stainless steel (SUS430) powder (average particle size 100 μm) produced by the gas atomizing method was used as the object to be treated. As a capsule, a thickness of 0.
It is a bag made of 05 mm mild steel and has a depth of 1 by bulging.
A product having a 0 mm indentation was used. Powder that is the object to be treated was filled in the depressions. The inner surface of the capsule was coated with alumina cement to a thickness of about 0.1 mm.

The capsule filled with powder is shown in FIG.
As shown in (d), after vacuum sealing, HIP
Set on the device, 1150 ℃, 1500kgf / cm ²
HIP treatment for 1 hour. After the HIP treatment, the capsule was taken out and subjected to oxidation treatment in the air at 900 ° C. for 1 hour. The oxidized capsule was in a collapsed state.

After removing the easily peelable portion, water in which zircon sand was dispersed was sprayed to remove residual deposits on the capsule and oxide film on the product surface. The obtained product was densified to the true density.

[0027]

According to the isotropic pressurizing method of the present invention, the capsule is oxidized or nitrided after the isotropic pressurizing treatment so that the capsule can be easily removed. Therefore, according to the isotropic pressing method of the present invention, the object to be processed can be easily vacuum-sealed, and the capsules can be easily removed after the isotropic pressing process.

Further, since the capsule waste generated by the removal has a small bulk, and since it is scale-like and the volume reduction process is easy, the post-treatment of the capsule waste as industrial waste is less troublesome than in the past.

[Brief description of drawings]

FIG. 1 is a process drawing showing one embodiment of the hot isostatic pressing method of the present invention.

[Explanation of symbols]

 1 Object to be treated 2 Capsules 11 Sandblasting gun

Claims (3)

[Claims] 1. An isotropic pressurization method in which an object to be processed is enclosed in a metal capsule and isotropically pressure-treated, and the capsule is oxidized or nitrided after the isotropic pressure-treatment, and thereafter,
A method for isostatic pressing, characterized in that the capsules converted into oxides or nitrides are removed. 2. A metal foil having a thickness of 0.05 to 0.3 mm and containing iron, titanium, tantalum, or zirconium as a main component as a capsule is used. Isotropic pressure method. 3. The isotropic pressurization according to claim 1 or 2, wherein the capsule after the oxidation or nitriding treatment is sprayed with a gas or liquid in which particles are dispersed to remove the capsule. Method.