JPH09137201A - Production of metallic porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a metallic porous body useful for plane burner, filter, catalyst carrier, insulating material, sound insulating material, high damping material, and forming die member, etc. SOLUTION: A capsule is filled with metal powder and an opening for introducing a hydrostatic pressure medium into the capsule is provided at a part of the capsule. Then, hot isostatic pressing treatment is carried out and the metal powder is sintered under the action of the controlled pressurizing force of the hydrostatic pressure medium infiltrating into the spacing among the metal powder grains in the capsule. It is desirable that sintering treatment is performed under a pressure of 0.5-150MPa at 0.5-0.99mpK [where mpK is the melting point of the metal powder and also is the melting point (absolute temp.) of a low-melting metal powder when the capsule is filled with metal powders of dissimilar materials in a laminated state]. If necessary, heat treatment for strengthening the intergranular bonding of a sintered compact is applied at a temp. of 0.5-0.99mpK.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metallic porous body having improved pore distribution characteristics and the like by hot isostatic pressing.

[0002]

2. Description of the Related Art A porous metal body produced by sintering metal powder is used as a molding die for a resin thermoforming die, a non-ferrous metal casting die, a filter, a catalyst carrier, and a heat insulating material. It is useful as a soundproofing material, a vibration damping material, etc. As its manufacturing method, a method in which metal powder or a mixture of metal powder and metal fibers is used as a raw material, and after pressure molding into a required shape, the powder compact is heat-sintered in a vacuum or a reducing atmosphere, or A method is used in which an appropriate amount of a binder, a solvent or the like is added to a raw material powder to prepare a slurry, which is then subjected to preliminary firing to evaporate the binder or the solvent and then a sintering treatment.

[0003]

SUMMARY OF THE INVENTION In the conventional manufacturing method,
It is difficult to control the pore size, porosity, etc. of the obtained porous metal body, and the uniformity of pore distribution is poor. These problems become more significant as the product shape becomes larger and more complex. When the raw material powder is difficult to sinter, it is difficult to secure mechanical strength. A uniaxial press, a cold isostatic pressing method (CIP method) or the like is applied to the pressure molding of the raw material powder, but as the raw material powder, one having a large particle size or a shape close to a sphere is used. When used, it is extremely difficult to produce a metal porous body having a large pore diameter and a high porosity. The present invention provides an improved method for producing a porous metal body, which solves the above-mentioned problems relating to the production of a porous metal body, and enables expansion and diversification of engineering applications of the porous metal body.

[0004]

The method for producing a porous metal body of the present invention is one in which hot isostatic pressing treatment is applied to the sintering treatment. An opening for introducing a hydraulic medium is provided in a part of the capsule and subjected to hot isotropic pressure treatment, and under the action of a controlled pressurizing force of the hydrostatic medium that enters the particle gap of the metal powder in the capsule. It is characterized in that the metal powder is sintered.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The hot isostatic pressing treatment of metal powder in a capsule provided with an opening for introducing a hydrostatic medium (hereinafter referred to as "H
In the “IP treatment”), the pressing force of the hydrostatic medium (inert fluid such as argon and nitrogen gas) acts on the outer surface of the capsule and at the same time, on the particle surface in the powder packed bed. The pressing force of the hydrostatic medium against the packed state in which the particles of the metal powder are simply in contact with each other does not substantially contribute as a compressive force that strengthens the bond between the particles, but it does not contribute to the diffusion reaction by heating. When the contact interfaces between the particles are bound together, they act as a compressive force that promotes the binding between the particles. Further, the pressure action of the hydrostatic medium that has entered the particle gap prevents and prevents the reduction of the pore diameter and open pores. The sintering reaction proceeds under the pressure action of such a hydrostatic medium to form a porous metal body having improved pore distribution and mechanical properties.

[0006] The HIP treatment performed by filling capsules with metal powder is known as an industrial production method for sintered alloy products, but it is intended for highly dense products close to true density. In the HIP process, powder filling into the capsule is vacuum-sealed in order to highly compress and densify the raw material powder. The present invention is such a conventional HIP.
Different from the treatment, the conventional HIP treatment in which an opening is provided in the capsule so that the inside and the outside are in communication with each other and the sintering reaction is performed in the state where the pressure force of the hydrostatic medium acts on the particle gap of the powder filling layer Adopts a completely different processing form, and as a result, it is possible to provide the improved pore distribution and mechanical properties desired for various structural members and functional members.

The metal powder is obtained by uniformly filling a capsule (for example, made of mild steel) with a single-grade powder, and if desired,
For the purpose of producing a metal porous body having a laminated structure, a plurality of types of powders having different material types and / or particle sizes are laminated and filled. A stacked filling mode of a plurality of kinds of metal powders is optional,
A vertically stacked structure, a concentric stacked structure, and the like are provided. The layer-filling operation uses a sheet material (paper, plastic sheet, thin metal plate, etc.) as a separator as needed. For example, when two types of metal powder are concentrically layered and packed in a cylindrical capsule, the capsule is filled with the separator. The inside of the main body may be divided into concentric circles, each space portion may be filled with a predetermined metal powder, and then the separator may be removed. If the opening for introducing the hydrostatic medium into the capsule is provided, for example, in the lid member that covers the capsule body, the filling operation of the powder is not hindered and the filling state is not impaired.

The treatment temperature of the HIP treatment of the metal powder filled in the capsule is preferably set in the range of 0.5 to 0.99 mpK [for example, when the melting point of the metal powder is 1700K, 0.5 × 1700 to 0.99]. × 1700K (= 850 to 1683K)
]. If the temperature is lower than 0.5 mpK, it takes a long time for the sintering reaction. It is preferably 0.70 mpK or more. Further, by limiting the treatment temperature to 0.99 mpK or less, melting and excessive adhesion of particles can be avoided, and the porosity of the sintered body can be maintained. As a raw material powder, the HIP treatment temperature when a plurality of kinds of metal powders are stacked and filled in a capsule is
The lowest melting point among them may be set as a reference. The pressure of the hydrostatic medium for HIP treatment is 0.5 to 15
A range of 0 MPa is suitable. When the applied pressure is lower than 0.5 MPa, the effect of enhancing the interparticle bonding force is small. It is preferably 80 MPa or more. The higher the pressurizing force, the more the effect increases, but up to 150 MPa is sufficient, and there is no advantage in applying a higher pressure. The HIP treatment is achieved by maintaining the temperature and pressure for a suitable time (for example, 1 to 5 hours).

If desired, the sintered body (metal porous body) obtained by the HIP treatment may be subjected to a heat treatment (strengthening heat treatment) for strengthening the interparticle bond without substantially changing the pore distribution. Is given. The heat treatment is performed at a temperature of 0.
Appropriate time (for example, 1-1 in the temperature range of 5-0.99mpK)
0 Hr) is held. By setting the treatment temperature to about 0.5 mpK or more, it is possible to efficiently perform the bond strengthening by diffusion bonding between particles.
By setting the upper limit to, melting / adhesion of particles and accompanying deterioration of pore distribution characteristics can be avoided. When the metal porous body has a laminated structure composed of a plurality of kinds of metals, the heat treatment temperature may be set on the basis of the lowest melting point of those metal material types, similarly to the temperature setting in the HIP treatment.

The above heat treatment can be carried out in the HIP device as a series of steps subsequent to the HIP process, or the capsule is taken out from the HIP device and left as it is (in a state where the sintered body is still encapsulated in the capsule) or The capsules may be removed by machining and then placed in a heat treatment furnace for execution. Since the raw material powder is a material that is difficult to sinter, and the sintered body (porous body) is fragile, the sintered body may be missing or collapsed during the machining process when taking it out from the capsule or the handling process after taking it out. When there is a possibility that the above problem may occur, the heat treatment may be performed in a state of being encapsulated in a capsule. The heat treatment when carried out in the HIP device may be carried out under the pressure of the hydrostatic medium, and is performed while releasing the pressurizing action (it usually takes several hours to restore the normal state). You may

The grade of the metal powder used in the production of the porous metal body of the present invention is arbitrary, and stainless steel (for example, S
US304, SUS630), tool steel (for example, SKD
61, SKD11), maraging steel (for example, 18
Ni-based, 20Ni-based, high speed steel (eg SKH5
1, SKH55), non-ferrous metals (for example, titanium or its alloys, nickel or its alloys, aluminum or its alloys, copper or its alloys), etc., depending on the intended use of the porous metal body and the required material properties. Used by choice.

The grain size of the raw material powder is not particularly limited and, for example, a grain size of 250 to 500 μm is used. If a porous metal product with a particularly large pore size or porosity is desired as the product porous body, use a relatively coarse powder, and if the metal porous body has high mechanical strength, use a relatively fine powder. Good to do.
As shown in Examples below, the pore distribution and mechanical properties of the obtained metal porous body can be controlled in a wide range by the particle size of the raw material powder, the temperature of the HIP treatment, the pressure applied, and the like.

[0013]

【Example】

[Raw material powder] A: Atomized powder of stainless steel (JIS G4303 SUS316L equivalent material) B: Atomized powder of stainless steel (JIS G4303 SUS630 equivalent material) C: Atomized powder of Inconel 625 (Ni-Cr-Fe alloy) Binding and Heat Treatment] (Examples 1 to 8) Raw material powder is filled in a mild steel capsule (cylindrical container), covered with a lid material (through holes having a hole diameter of 10 mm are dispersedly formed on the plate surface), HIP-treated, and HIPed. After treatment, heat-treated or not heat-treated, porous sintered body (diameter 70 x length
150, mm). In Examples 1 to 6, one kind of raw material powder was used, and in Examples 7 and 8, two kinds of raw material powder were stacked and packed into upper and lower two layers (the thickness of each sintered body was 75 mm). Further, in Example 2, after the HIP treatment, the sintered body was taken out from the capsule and subjected to the strengthening heat treatment in the vacuum heat treatment furnace. In Example 8, after the HIP treatment, the hydrostatic pressure medium was applied in the HIP device. The heat treatment was carried out while releasing the heat treatment for 5 hours. (Comparative example) Uniaxial pressing of raw material powder (pressing force: 2000 kgf / cm
² ) to obtain a cylindrical powder compact, which is then sintered under normal pressure (temperature: 1200 ℃, time: 4 Hr, atmospheric pressure: 1 × 10 ^-3 Torr)
To obtain a cylindrical sintered body.

Table 1 shows the production conditions of each example and various characteristics of the obtained porous metal body. In the table, the numerical value in the "gas release property" column indicates the test piece cut out from the porous metal body (thickness: 3 m
m) Air pressure required for permeation of air (kgf / cm ² ),
The “Tensile strength” column shows the results of tensile tests in accordance with JIS Z2241. The gas permeation test pieces of the metal porous bodies of Examples 7 and 8 (two-layer lamination structure) were prepared so that the lamination interface was orthogonal to the gas permeation direction. It was prepared in the direction orthogonal to the direction.

As described above, the porous metal body obtained as a sintered body according to the present invention can control the pore distribution characteristics, mechanical strength and the like in a wide range by the raw material powder particle size, HIP treatment conditions, strengthening heat treatment and the like. Recognize. Example 1,
The high porosity and high permeability of sintered bodies such as 2,4,5 and the like cannot be obtained by conventional manufacturing methods. Moreover, the heat treatment after the HIP treatment makes it possible to increase the mechanical strength while maintaining relatively high porosity. Although the porous metal bodies of Examples 1 and 5 have remarkable porosity as described above, they have poor mechanical strength, but they are used as clad materials in combination with other members (casting materials, forging materials, etc.). As a result, it becomes possible to apply to applications requiring high porosity and higher mechanical strength.

[0016]

[Table 1]

[0017]

According to the present invention, it is possible to obtain a porous metal body in which the pore diameter and the porosity are arbitrarily controlled to be high or low. This enhances the functions of the filter material, the catalyst carrier, the heat insulating material, the soundproofing material, the vibration damping material, and the molding die material by the porous metal body, and the application of the porous metal body as the flat burner becomes possible.
It is intended to expand and diversify the industrial use of porous metal and to greatly enhance its practical value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryutaro Motoki 1-1-1, Nakamiya Oike, Hirakata City, Osaka Prefecture Kubota Hirakata Factory

Claims (5)

[Claims] 1. A capsule is filled with metal powder, and an opening for introducing a hydrostatic medium into the capsule is provided in a part of the capsule and subjected to hot isostatic press treatment. A method for producing a metal porous body, comprising: sintering a metal powder under the action of a controlled pressurizing force of a hydrostatic medium penetrating into a particle gap. 2. The method for producing a metal porous body according to claim 1, wherein a plurality of kinds of metal powders having different particle sizes and / or grades are stacked and filled in a capsule. 3. The hot isotropic pressure treatment is applied at a pressure of 0.5 to
150 MPa, temperature: 0.5-0.99 mpK [however, mp
K is the melting point of the metal powder, or the melting point (absolute temperature) of the low-melting metal powder when the metal powders of different materials are stacked and filled]. The metal according to claim 1 or claim 2. Method for manufacturing porous body. 4. After the hot isostatic pressing treatment, a heat treatment for strengthening the interparticle bond of the sintered body is performed while the sintered body is encapsulated in the capsule or taken out from the capsule. The method for producing a porous metal body according to any one of claims 1 to 3. 5. Heat treatment, temperature: 0.5-0.99mpK
The method for producing a porous metal body according to claim 4, wherein