JP2004043937A - Porous metal and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous metal having a size of voids of ≤1 mm and a void fraction of ≥60% for which only limited production methods were available in the conventional technique, and to provide the method of producing the same. <P>SOLUTION: Metal powder comprising one or more components is sealed together with a gas of a pressure equal to or greater than the atmospheric pressure into the inside of a metallic vessel which can be plastically worked. The metallic vessel is pressurized at a high temperature to sinter the metal powder and to compress the gas. Next, the sintered compact comprising the high pressure gas is heated to a solid-liquid two phase state, and the volume of the gas in a solid-liquid two phase state is expanded to form voids. Thus, the porous metal comprising voids of ≤1 mm and having a void fraction of ≥60% is produced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low-density porous metal containing a large amount of voids and a method for producing the same, and more specifically, for example, to produce a porous metal sheet having a void size of 1 mm or less and a porosity of 60% or more. The present invention relates to a method for manufacturing a porous metal and a product thereof. The porous metal of the present invention has low density, excellent sound absorption properties, high energy absorption characteristics, and the like, and is therefore useful as a construction material, a material for automobiles, and the like.
[0002]
[Prior art]
The porous metal is a metal material in which fine voids are positively introduced inside the dense body. When the porosity (= {1- (apparent density of the porous metal / density of the metal dense material)} × 100%) of the porous metal is 60% or more, low density, excellent sound absorption, and high energy absorption are obtained. Because of its properties, it is used for construction materials, automotive materials and the like. In addition, porous metal is a material that is expected to increase in demand as a lightweight material excellent in recyclability because it is ultralight and excellent in metal-specific recyclability.
[0003]
As a conventional method for producing a porous metal, for example, a precision casting method for producing a porous metal (for example, Y. Yamada et al., J. of.) Mat. Sci. Lett., 18 (1999), P. 1277.), a plating method for producing a porous metal by plating a metal on a porous resin or the like (for example: M. Otsuka et al. Proc. 3rd. Japan Int.). SAMPE Symp, Dec. 7-10, 1993, P. 887), a foaming agent is added to a molten metal, and the molten metal is solidified in a state of generating a gas to produce a porous metal. Miyoshi et al., Adv. Eng. Mater., 2 (2000), P. 179.). .
[0004]
Further, a solid foaming method for producing a porous metal by releasing a gas from a foaming agent as a solid (for example, JP-A-2001-342503), heating a metal containing a small amount of high-pressure gas to a high temperature to expand the gas. For example, there is a gas expansion method for producing a porous metal (for example, DT Queheilalt et al., Metal. Mater. Trans. A, 31A (2000), P. 261.). Powder metallurgy (for example, CE Wen et al., Scripta. Mater. 45 (2001), P. 1147.) produced by compressing and sintering a metal powder and a binder powder; Metal sintering method (for example, Kiyoshi Suzuki, Industrial Materials, 30 (1980), No. 10, P. 104.) for depositing and sintering metal, There is a cutting waste sintering method (for example: Japanese Patent Application No. 2001-293301).
[0005]
However, in the case of the precision casting method, the plating method, the molten metal foaming method, and the metal swarf sintering method, a porous metal having a high porosity of 60% can be produced, but the average diameter of the voids is 1 mm or more and the minute diameter of 1 mm or less. There is a problem that it is difficult to produce a porous metal having a large void. On the other hand, in the case of the solid foaming method and the gas expansion method, a porous metal containing minute voids of 1 mm or less can be produced, but the porosity is 60% or less, and the high porosity of 60% or more is high. There is a problem that it is difficult to manufacture metal. In the case of the powder metallurgy method or the short metal fiber method, it is possible to make the porosity 60% or more while keeping the diameter of the voids at 1 mm or less. However, the use of powdered and short metal fibers is effective for products that are produced in large quantities and small quantities, but leads to high costs for products that require small-scale mass production such as automobile shock absorbers. Therefore, there is a problem that application is difficult.
[0006]
[Problems to be solved by the invention]
Under these circumstances, the present inventors have conducted intensive studies in view of the above-described conventional technology with the aim of developing a new porous metal manufacturing technology capable of solving the problems of the conventional technology. As a result of the superposition, it was found that the intended purpose could be achieved by expanding the high-pressure inert gas confined in the solid of the metal powder sintered body in a solid-liquid two-phase state. It was completed.
An object of the present invention is to provide a porous metal having a void size of 1 mm or less and a porosity of 60% or more and a method of manufacturing the porous metal, the production method of which has been limited in the prior art.
Further, the present invention provides a method for manufacturing a porous metal molded body having fine voids of 1 mm or less, a porosity of 60% or more, and a porous thin plate having a thickness of several mm and a molded body thereof. The purpose is to provide.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems includes the following technical means.
(1) A metal powder containing one or more components is sealed in a metal container capable of plastic working together with a gas of 1 atm or more, and the metal powder is sintered at a high temperature by pressurizing the metal powder. The porous body is characterized in that the sintered body containing the high-pressure gas is heated to a solid-liquid two-phase state and the volume of the gas is expanded in the solid-liquid two-phase state to generate voids. Metal manufacturing method.
(2) The porous metal according to (1), wherein the main component of the metal powder is aluminum, iron, titanium, copper, magnesium, tin, zinc, nickel, cobalt, tungsten, or molybdenum. Method.
(3) The main component of the metal container enclosing the metal powder is aluminum, iron, titanium, copper, magnesium, tin, zinc, nickel, cobalt, tungsten, or molybdenum, as described in (1) above. Production method of porous metal.
(4) The method for producing a porous metal according to (1), wherein the main component of the gas sealed in the metal container is any one of nitrogen, argon, and helium.
(5) The method for producing a porous metal as described in (1) above, wherein the metal container is subjected to hot extrusion, pressing, forging, isostatic pressing, drawing, or rolling to a high temperature.
(6) The method for producing a porous metal according to the above (1), wherein a sintered body containing a high-pressure gas is inserted into a mold and heated to a solid-liquid two-phase state to form a molded body.
(7) The method for producing a porous metal according to the above (1), wherein the sintered body containing the high-pressure gas is rolled and then heated to a solid-liquid two-phase state to obtain a formed body.
(8) The method for producing a porous metal according to any one of (1) to (7), wherein the average diameter of the pores is 50 μm to 500 μm, and the porosity is 60% or more.
(9) A porous metal produced by the production method according to any one of (1) to (8), having a void of 1 mm or less, and having a porosity of 60% or more.
(10) The porous metal according to (9), wherein the porous metal is a molded body.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention expands a high-pressure inert gas confined in a sintered metal powder solid in a solid-liquid two-phase state (a state in which a solid and a liquid are mixed) to have a void of 1 mm or less, and a porosity of 1 mm or less. It is characterized in that a porous metal of 60% or more is produced. In the present invention, in order to produce a porous metal having a void size of 1 mm or less and a porosity of 60% or more, expanding an inert gas in a solid metal in a solid-liquid two-phase state, specifically, an inert gas And a metal powder are sintered under pressure to introduce a high-pressure inert gas into the solid metal, and expand the solid metal introduced with the high-pressure gas in a solid-liquid two-phase state to produce a porous metal.
[0009]
The present invention is applied to various metals in which a solid-liquid two-phase state can exist. Examples of these metals include, but are not limited to, aluminum, iron, titanium, copper, magnesium, tin, zinc, nickel, cobalt, tungsten, and alloys mainly containing molybdenum. The process of the present invention can produce a porous metal in any alloy having a solid-liquid coexisting phase.
[0010]
Hereinafter, the present invention will be described using an aluminum alloy as an example. In the method of the present invention, first, an aluminum alloy powder is put into a pure aluminum container, and then the container is filled with a high-pressure gas of 1 atm or more and sealed. After sealing, the powder is sintered by hot extruding an aluminum (alloy) container. At this time, the gas is reduced by the pressure of the extrusion and is confined in the bulk as a high-pressure gas. After the extrusion, when heated and held to form a solid-liquid two-phase state, the reduced gas expands, and a porous alloy round bar containing a large amount of voids is produced. The above process is schematically shown in FIG. In this process, the gas expands preferentially in the liquid phase, but the expansion of the gas is suppressed by the surrounding solid, so that the size of the void can be reduced to 1 mm or less.
[0011]
In another method of the present invention, an aluminum (alloy) container is charged with aluminum alloy powder, and then the container is filled with a high-pressure gas of 1 atm or more and sealed. After the encapsulation, hot pressing (or forging, isostatic pressing) is performed to sinter the powder. When this sintered material is inserted into a mold and then heated to a solid-liquid two-phase state, the sintered material expands inside the mold, and a porous alloy molded article having a complicated shape is manufactured. The above process is schematically shown in FIG.
[0012]
In another method of the present invention, an aluminum (alloy) container is charged with aluminum alloy powder, and then the container is filled with a high-pressure gas of 1 atm or more and sealed. After the encapsulation, hot pressing (or forging, isostatic pressing) is performed to sinter the powder. After cutting this sintered material into a plate shape, a thin plate is produced by rolling. When the sheet is heated to a solid-liquid two-phase state, the sheet expands and a porous alloy sheet is produced. The above process is schematically shown in FIG.
[0013]
In another method of the present invention, an aluminum (alloy) container is charged with aluminum alloy powder, and then the container is filled with a high-pressure gas of 1 atm or more and sealed. After encapsulation, the powder is sintered by hot drawing the aluminum container. At this time, the gas is reduced by the withdrawal pressure and is confined in the bulk as a high-pressure gas. After drawing, if heated and held to form a solid-liquid two-phase state, the reduced gas expands, and a porous alloy fine wire containing a large amount of voids is produced. The above process is schematically shown in FIG.
[0014]
In the present invention, the type of the metal container into which the metal powder is injected, which is used in the above-described porous metal production process, has a moderate ductility, and is subjected to a series of plastic working (rolling, extrusion, drawing, forging, pressing, pressing, and the like). Those which do not break under water pressure) are desirable. Ideally, it is desirable to use a can made of the same material as the metal powder, but it is also possible to substitute a material having ductility and strength close to that of the metal powder.
[0015]
As the type of the high-pressure gas used in the above-described porous metal production process, an inert gas that does not react with the metal powder is desirable, and examples thereof include an argon gas, a nitrogen gas, and a gas mainly containing a helium gas. However, the present invention is not limited to these.
[0016]
In the above process, if the amount of the liquid phase is too small, the expansion of the gas is slow, and the size of the voids is 1 mm or less, but the porosity is 60% or less. On the other hand, if the amount of the liquid phase is too large, the effect of suppressing the expansion due to the solid is reduced, and the porosity becomes 60% or more, but the size of the void becomes 1 mm or more. In order to produce a porous material having a void size of 1 mm or less and a porosity of 60% or more, a sintered body containing a high-pressure gas is heated to a solid-liquid two-phase state, and the volume of the gas is expanded in the solid-liquid two-phase state. It is required that the amount of the liquid phase at the time of generating the void is appropriate. For example, taking an aluminum alloy (7075 alloy) as an example, it is desirable to expand the gas inside the metal container at a temperature about 100 ° C. to 160 ° C. higher than the solidus temperature (479 ° C.). These heating and holding temperatures can be set according to the type of metal used and the purpose of use.
[0017]
When various porous metals produced by the process of the present invention are used, a large number of voids can be provided in a small compact of about several mm, and the porous metal can be used for various uses. For example, in order to produce a thin plate having a thickness of about several mm from porous metal, it is necessary to form a large number of voids of 1 mm or less inside the plate. The porous metal thin plate according to the present invention is a material capable of simultaneously realizing ultra-lightweight, easy processability, and easy recyclability, and is used as a substitute for a resin material or the like for parts of an automobile or the like that is required to be reduced in weight. It is possible. The process of the present invention is useful as a basic technique for producing a porous metal sheet.
[0018]
[Action]
The present invention expands a high-pressure inert gas confined in a sintered metal powder solid in a solid-liquid two-phase state (a state in which a solid and a liquid are mixed) to have a void of 1 mm or less, and a porosity of 1 mm or less. It is characterized in that a porous metal of 60% or more is produced. In the present invention, a molded article of any form can be produced by inserting a sintered body containing a high-pressure gas into a mold and heating it to a solid-liquid two-phase state. In addition, a thin plate can be produced by rolling the sintered body and then heating it to a solid-liquid two-phase state. By utilizing the method for producing a porous metal of the present invention, it is possible to provide a large number of voids in a fine member of about several mm, and in particular, it is possible to produce a porous thin plate having a thickness of several mm. It is a low-cost and simple method, and is useful as a basic technology for producing metal shock absorbers, ultralight-weight thin plates, easily recyclable thin plates, and the like.
[0019]
【Example】
Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.
Example 1
In this embodiment, as an example, a porous metal was manufactured using an aluminum alloy (7075 alloy).
(1) Production of Porous Metal A commercially available 7075 aluminum alloy powder (Al-5.5 mass% -2.5 mass% Mg-1.5 mass% Cu alloy aluminum powder) was placed in a pure aluminum container shown in FIG. After filling to / 3, the vessel was filled with 10 atm of argon gas and sealed. The particle size of the aluminum alloy powder used in this example was 50 μm or less. After the encapsulation, the aluminum container was extruded hot under the conditions of a temperature of 400 ° C. and an extrusion ratio of 8, to produce a round bar having a diameter of 14 mm. The extruded rod was heated and maintained at 630 ° C. for 72 hours to produce a porous aluminum alloy. As a result of differential thermal analysis, the solidus temperature of the present 7075 aluminum alloy was 479 ° C.
[0020]
(2) Results FIG. 6 shows the internal structure (a) of the porous aluminum alloy before heating and holding and the internal structure (b) of the porous aluminum alloy after heating and holding, respectively. The porosity of the extruded rod before heating and holding was 5%. On the other hand, the porosity of the extruded rod after heating and holding was improved to 74%. Next, FIG. 7 shows the result of measuring the cell size of the produced porous aluminum alloy by image analysis. It can be seen that the void size is concentrated at 50 to 400 μm. That is, from the results of FIGS. 6 and 7, it is understood that a porous metal having a void of 1 mm or less and a porosity of 60% or more can be manufactured according to the present invention.
[0021]
Example 2
After filling a commercially available 7075 aluminum alloy powder (Al-5.5 mass% -2.5 mass% Mg-1.5 mass% Cu alloy aluminum powder) into the pure aluminum container shown in FIG. 5 to 2/3 of the container volume, The vessel was filled with 10 atm of argon gas and sealed. After sealing, the aluminum container was hot-extruded under the conditions of a temperature of 400 ° C. and an extrusion ratio of 6, to produce a round bar having a diameter of 6 mm. The particle size of the aluminum alloy powder used in this example was 50 μm or less. The extruded rod was heated and maintained at 460 ° C. and 630 ° C. for 72 hours to produce a porous aluminum alloy. As a result of differential thermal analysis, the solidus temperature of the present 7075 aluminum alloy was 479 ° C. FIG. 8 shows the internal structure (a) of the porous aluminum alloy after heating and holding at 460 ° C. and the internal structure (b) after heating and holding at 630 ° C., respectively. As a result of the density measurement, the porosity was 9% and 74%, respectively. From the results shown in FIG. 8, it can be confirmed that an appropriate amount of liquid phase is required for producing a porous metal according to the present invention.
[0022]
【The invention's effect】
As described above in detail, the present invention relates to a porous metal and a method for manufacturing the same. According to the present invention, 1) a porous metal having a void size of 1 mm or less and a porosity of 60% or more can be produced. 2) The obtained porous metal is lightweight, has excellent energy absorption and vibration absorption, and has excellent recyclability unique to the metal. 3) The present invention relates to a conventional porous metal. It is possible to produce a porous metal having fine voids of 1 mm or less, which was difficult by the production method (precision casting method, plating method, molten metal foaming method, etc.), by a relatively easy method. 5) Therefore, the present invention has an extraordinary effect that its industrial significance and industrial applicability are very large.
[Brief description of the drawings]
FIG. 1 shows a process for producing a porous metal rod according to the invention.
FIG. 2 shows a process for producing a complex-shaped porous metal molding according to the present invention.
FIG. 3 shows a process for producing a porous sheet metal according to the present invention.
FIG. 4 shows a process for producing a porous fine metal wire according to the present invention.
FIG. 5 is an explanatory view of a pure aluminum metal container used in the present invention, an aluminum alloy powder and an inert gas sealed therein.
FIG. 6 shows the internal structure (a) of the extruded material before heating and holding, and the internal structure (b) of the extruded material after heating and holding at 630 ° C. for 72 hours.
FIG. 7 shows a pore size distribution per unit area of a porous aluminum alloy produced by the method of the present invention.
FIG. 8 shows the internal structure (a) of the extruded material after heating and holding at 460 ° C. for 24 hours and the internal structure (b) of the extruded material after heating and holding at 630 ° C. for 72 hours.

Claims (10)

A metal powder containing one or more types of components is sealed in a metal container capable of plastic working together with a gas of 1 atm or more. Producing a porous metal characterized by reducing the size and then heating the sintered body containing the high-pressure gas to a solid-liquid two-phase state and expanding the volume of the gas in the solid-liquid two-phase state to generate voids. Method. The method for producing a porous metal according to claim 1, wherein the main component of the metal powder is aluminum, iron, titanium, copper, magnesium, tin, zinc, nickel, cobalt, tungsten, or molybdenum. The porous metal according to claim 1, wherein the main component of the metal container for enclosing the metal powder is aluminum, iron, titanium, copper, magnesium, tin, zinc, nickel, cobalt, tungsten, or molybdenum. Production method. The method for producing a porous metal according to claim 1, wherein a main component of the gas sealed in the metal container is any of nitrogen, argon, and helium. The method for producing a porous metal according to claim 1, wherein the metal container is subjected to hot extrusion, hot pressing, forging, isostatic pressing, drawing, or rolling. The method for producing a porous metal according to claim 1, wherein a sintered body containing a high-pressure gas is inserted into a mold and heated to a solid-liquid two-phase state to form a molded body. The method for producing a porous metal according to claim 1, wherein the sintered body containing the high-pressure gas is rolled and then heated to a solid-liquid two-phase state to obtain a formed body. The method for producing a porous metal according to any one of claims 1 to 7, wherein the average diameter of the pores is 50 µm to 500 µm, and the porosity is 60% or more. A porous metal produced by the production method according to any one of claims 1 to 8, having a void of 1 mm or less, and having a porosity of 60% or more. The porous metal according to claim 9, wherein the porous metal is a molded body.

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