JP2004322143A - Method for manufacturing porous metallic body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous metallic body, a method for forming pores in an accurate shape by safely controlling a metallic material in the direction, size, porosity and structure of the pores without using a specific hydrogen gas. <P>SOLUTION: Using a hermetically sealed container 100 equipped with a heating chamber 1 that can control pressure and a solidifying chamber 2 that has a casting mold 3 capable of adjusting moisture content and a cooling section 4, a porous metallic body is manufactured which is controlled in one direction by melting, cooling and solidifying a metallic material 200 under argon gas pressurization. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a porous metal body. In particular, the inherently large surface area of a porous metal body having a unidirectional morphology, as well as applications with uniformly controlled pores and porosity. Although the application direction is wide, development is currently being progressed on heat sinks, hydrostatic bearings, filters, automobile / aircraft components, various machine tools, and the like.
[0002]
[Prior art]
In a conventional method for producing a porous metal body having one direction, the production method enables generation of bubbles and formation of bubbles under pressure of hydrogen gas, nitrogen gas, oxygen gas, or the like.
[Patent Document 1] JP-A-10-88254 [Patent Document 2] JP-A-2000-104130
[Problems to be solved by the invention]
According to the present invention, it is possible to make the metal raw material porous by using moisture for the production under the pressurization of the hydrogen gas or by using the moisture under the pressurization of the inert gas. Accordingly, it is an object of the present invention to provide a novel manufacturing method which is relatively safe and economical with respect to the prior art.
[0004]
[Means for Solving the Problems]
As a means for solving the above-mentioned problems, the present invention applies a water-containing alumina mixture to the inside of a mold as shown in FIGS. 2 (a), 2 (b) and 2 (c), and then melts the mixture. The metal raw material is cast, and further, the molten metal raw material starts cooling and solidifying by the cooling unit to form pores in one direction. In the pore formation, the water contained in the alumina mixture dissolves into the molten metal raw material and is decomposed into hydrogen and oxygen. The decomposed hydrogen becomes bubbles due to the solubility gap to form pores. The above relationship is clear from FIGS. 3 and 4 (a) and (b) and is an effective means.
[0005]
Further, by controlling the pressure of the argon gas and the amount of water in order to control the shape, pore diameter and porosity of the pores, various structures as shown in FIGS. 5A to 5D can be made porous. It is possible.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the process of heating and melting and solidifying a molten metal material in a mold by cooling and solidifying the same, the water contained in the alumina mixture applied inside the mold is dissociated into hydrogen and oxygen in the process of transforming into a solid, and the metal A porous metal body is manufactured by utilizing the property of being precipitated in a solid phase of a raw material.
[0007]
The present invention shown in FIG. 1 includes a heating chamber 1 having an induction heating coil 7, a crucible 5, a stopper rod 8 and the like as heating means, and a solidification chamber 2 having a mold 3 and a cooling unit 4 of a cooling and solidifying means below the heating chamber 1. It is a closed container 100 that is mounted and configured vertically, showing a preferred embodiment. The structure of the closed container 100 includes a heating chamber 1 and a coagulating chamber for melting the metal raw material 200 at a predetermined temperature and further cooling and solidifying under a argon gas atmosphere using a predetermined coagulation temperature and a predetermined coagulation pressure. 2 keeps the inside airtight. The mold 3 is coated with an alumina mixture 6 in which alumina powder, a sodium silicate solution, water and the like are mixed at a predetermined ratio on the inside where the molten metal raw material 200 is poured.
[0008]
When the metal raw material 200 in the crucible 5 is melted by the induction heating coil 7, argon gas is injected into the sealed container 100 from the gas injection pipe 9 and is kept under a predetermined pressure. Further, when the metal raw material 200 reaches a predetermined melting temperature, the stopper rod 8 rises, the introduction funnel 11 is opened, and the molten metal raw material 200 flows into the casting mold 3 provided in the lower solidification chamber 2.
[0009]
The inside of the coagulation chamber 2 is maintained under a predetermined coagulation pressure by argon gas, and the cooling unit 4 is cooled by cooling water using a cooling water inflow pipe 12 and a cooling water inflow pipe 13. Therefore, the metal raw material 200 introduced into the mold 3 starts to solidify rapidly from the surface in contact with the cooling surface at the bottom, and pores grow parallel to the solidification direction. The formation of pores during solidification is such that water contained in the alumina mixture 6 applied to the inside of the mold 3 dissolves into the molten metal raw material 200 and is decomposed into hydrogen and oxygen. During the solidification, the hydrogen is precipitated as bubbles due to the difference in solubility between the molten metal and the solid metal, and grows into unidirectional pores. Further, it is considered that the oxygen forms various oxides upon solidification, and these serve as heterogeneous nucleation sites. FIG. 2 shows a model of pore formation by use of moisture. Since the argon gas, which is an atmosphere gas, is an inert gas, it is not directly related to the nucleation of bubbles, but it is related to controlling the porosity and pore diameter of the growing pores.
(A) shows a state where the alumina mixture 6 is applied to the inside of the mold 3 and the molten metal raw material 200 is not yet cast. The alumina mixture 6 is obtained by drying a solution of alumina powder, sodium silicate and water. It was done.
(B) shows a state in which the molten metal material 200 has been cast into the mold 3, at which point the solidification of the molten metal raw material 200 is about to start, but the contained moisture dissolves in the molten metal 200 and is decomposed into hydrogen and oxygen. . At this time, the oxide contained therein may also dissolve.
(C) shows a state in which the molten metal raw material 200 is solidified, pores are formed, and the pore morphology continues to grow, and the decomposed hydrogen becomes bubbles due to the solubility gap and is formed in the pores. Is done. At this time, it is considered that oxides, alumina, sodium silicate, and the like in the metal have become heterogeneous nucleation sites.
If the cooling unit is not specified, a porous metal body in which spherical random distribution pores are dispersed can be produced.
【Example】
An embodiment of the present invention shown in FIGS. 5 and 6 will be described below. The formation of the pore direction, pore diameter, porosity, and the like of the porous metal body is controlled by controlling parameters such as the amount of water contained in the alumina mixture 6, the melting temperature, the rate of cooling and solidification, and the pressure of the inert gas. Can be determined.
[0010]
FIG. 5 is a photograph showing a vertical cross section of a porous metal body made of pure nickel manufactured using argon as an inert gas under a pressure of 0.3 MPa. Pure nickel uses electrolytic nickel of 99.9% purity, and argon uses 99.999% of purity and is cast at a melting temperature of 1.873K. Moisture dissolved in the molten metal raw material is obtained by applying an alumina mixture 6, an alumina powder, a sodium silicate solution, and water at a ratio of 8: 2: 5 using a molybdenum thin plate processed into a cylindrical shape. Was measured.
(A) is an example in which the nickel porous body produced under the above conditions was cut at the longitudinal center by an electric discharge machine, and the water content in the alumina mixture 6 was 0.0596 g.
(B) is an example of a nickel porous body in which the water content in the alumina mixture 6 is 0.0876 g.
(C) is an example of a nickel porous body in which the water content in the alumina mixture 6 is 1.1070 g.
(D) is an example of a nickel porous body in which the amount of water in the alumina mixture 6 is 0.1201 g.
[FIG. 6] is a cross section and a vertical cross section obtained by cutting the position of 4.5 mm from the cooling bottom surface with the electric discharge machine in the example of (c) in FIG. 5 described above, and the porosity is 44. 7% and the average pore size is 105 μm.
[0011]
The present invention is not limited to the above-described embodiments and examples, and various aspects are possible in the details of the production method and the mode of pore generation.
[0012]
【The invention's effect】
In the present invention, the hydrogen and oxygen in the water used dissociate during solidification, and the oxygen becomes a site for heterogeneous nucleation, and promotes the nucleation of bubbles in the molten metal raw material, while the hydrogen forms bubbles in the molten metal material. It is characterized in that it is formed in the pores and grows into pores to form a fine porous metal body. Therefore, a finer porous metal body can be obtained while maintaining a high porosity at a low atmospheric pressure, as compared with the conventional method performed under a gas pressure of hydrogen. In addition, as the amount of water used increases, the porosity and the pore diameter both tend to increase.In addition, when the argon atmosphere pressure is 0.3 MPa, the pore form becomes fibrous. In view of the tendency that pore generation and growth tend to be suppressed as the size increases, this manufacturing method is applied to a closed container corresponding to a sufficiently large pressure, a moisture generation and regulation system, temperature and pressure control. A system is a relatively safe and economical way to produce porous metal bodies.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating a sealed container 100 in which a heating chamber 1 and a coagulation chamber 2 are mounted as an apparatus for the method of the present invention.
FIG. 2 is a model diagram of pore formation by utilizing water in the method of the present invention.
(A) is a mold 3 made of a thin molybdenum plate mounted on the cooling unit 4, in which an alumina mixture is applied inside, and shows a state before casting.
(B) shows a state where the molten metal raw material 200 is cast.
(C) shows a state in which the cast molten metal raw material 200 is cooled and solidified.
FIG. 3 shows the change in porosity of the porous metal body shown in FIGS. 5A to 5D prepared using pure nickel as the metal raw material 200, based on the amount of water in the alumina mixture 6 and the bottom surface of the cooling unit 4. 6 is a graph showing the relationship between the distance and the distance.
FIG. 4 (a) shows the change in the pore diameter of the porous metal body shown in FIGS. 5 (a) to 5 (d) produced by using pure nickel as the metal raw material 200, with the water content in the alumina mixture 6 and the cooling. 9 is a graph showing a relationship between a distance from a bottom surface of a part 4 and a part.
5B is a graph showing the change in the pore number density of the porous metal body shown in FIGS. 5A to 5D using pure nickel as the metal raw material 200 and the water content in the alumina mixture 6 and the cooling unit 4. It is a graph showing the relationship with the distance from the bottom.
FIG. 5 is a photograph showing a longitudinal section of a porous metal body of pure nickel produced under a pressure of 0.3 MPa of argon by the method of the present invention.
In (a), the amount of water in the alumina mixture 6 is 0.0596 g.
In (b), the water content in the alumina mixture 6 is 0.0876 g.
In (c), the amount of water in the alumina mixture 6 is 0.1070 g.
In (d), the water content in the alumina mixture 6 is 0.1201 g.
FIG. 6 is an enlarged photograph of (c) of FIG. 5 and is a portion 4.5 mm from the bottom surface of the cooling unit 4;
The porosity is 44.7% and the average pore diameter is 105 μm.
(A) is a photograph of a longitudinal section.
(B) is a cross section.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating room 2 Solidification room 3 Mold 4 Cooling part 5 Crucible 6 Alumina mixture 7 Induction heating coil 8 Stopper rod 9 Gas injection pipe 10 Gas exhaust pipe 11 Introduction funnel 12 Cooling water inflow pipe 13 Cooling water outflow pipe 100 Closed vessel 200 Metal raw material

Claims (4)

A method for producing a porous metal body comprising the following steps:
(1) a step of melting a metal raw material in a closed container;
(2) A step of forming a porous metal body by cooling and solidifying the molten metal in a mold containing moisture while controlling the temperature of the molten metal in the closed container. The porosity according to claim 1, wherein the metal is selected from the group consisting of iron, copper, nickel, magnesium, titanium, chromium, cobalt, tungsten, manganese, molybdenum, beryllium, aluminum, uranium, and alloys containing at least one of these metals. Method for manufacturing a porous metal body. 3. The method according to claim 1, wherein the porous metal body is formed by melting and cooling and solidifying a metal raw material under pressure using an inert gas in the closed vessel. The method for producing a porous metal body according to claim 3, wherein the pressure of the inert gas used in the step (1) and the step (2) is in a range of 0.01 MPa to 10 MPa.

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