JPS5938343A - Porous metallic material and its production - Google Patents

Abstract

PURPOSE:To obtain an air-permeable metallic material having high porosity, by sintering and molding a solvent-soluble inorg. compd., preheating the same to a specific temp. of the m.p. thereof or below, forcing molten metal or alloy into the voids and solidifying the same, then eluting the inorg. compd. with a solvent. CONSTITUTION:A solvent-soluble inorg. compd. is sintered and molded to a prescribed shape. The sintered body is preheated to the m.p. thereof or below and the temp. range expressed by the equation. In the equation, TP; the preheating temp. of the sintered body ( deg.C), TC: critical preheating temp. ( deg.C), TM, HM, DM; respectively the solidification point ( deg.C), latent heat of solidification (Cal/g) and density (g/cm<2>) of the molten metal or alloy, VP, CP, DP; respectively the packing rate occupying the spaces among the solvent soluble inorg. compd. particles, specific heat (Cal/g/ deg.C) and density (g/cm<3>). The molten metal or alloy is forced into the voids of the sintered body and is solidified and the sintered body is treated with a solvent to elute the inorg. compd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous porous metal material having extremely high porosity and a method for manufacturing the same.

In general, porous metals are divided into independent pore types and continuous pore types depending on the form of the pores contained therein.Independent pore types have no air permeability, while in continuous pore types, the pores are open to the outside air. Therefore, it has breathability.

This continuous pore type porous metal is a highly functional material.
For example, oil-impregnated bearings, filters, heat exchangers, electrodes, catalysts,
It is widely used for storing special substances.

By the way, when a continuous pore type porous metal material is used for the above-mentioned purpose, the higher the porosity, the higher the value of the material.Therefore, attempts have been made to manufacture materials with high porosity; Since this method has no choice but to use the powder metal method, there is a limit to the porosity that can be obtained naturally.
It was not possible to obtain a continuous porous metal material with a porosity of 40 cm or more.

As a result of extensive research in order to develop a high porosity (interconnected) porous metal material, the present inventors sintered an aggregate of inorganic compound particles that could be dissolved in an appropriate solvent into a predetermined shape. Next, molten metal is press-fitted into the voids of the sintered body, and after cooling and solidifying the molten metal, the inorganic compounds are dissolved and removed.
It was discovered that a continuous porous metal with a high porosity that could not be obtained using conventional methods with a porosity of 0.0 or more could be obtained, and based on this knowledge, an inventive invention was made.

In other words, the non-inventive feature is that the pores communicating with the outside account for 5 of the total volume.
A porous metal material consisting of a metal or alloy with a three-dimensional network structure occupying more than 0.0 mm and a solvent-soluble inorganic compound are molded into a predetermined shape and sintered, and then melted into the voids of the sintered body. The present invention provides a method for producing a porous metal material, which comprises press-fitting a metal or alloy, solidifying it, and then treating it with a solvent to elute the inorganic compound.

The material for the porous metal material of the present invention can be arbitrarily selected from metals or alloys that are commonly used for metal materials. Examples of such materials include cast iron,
Mention may be made of lead, zinc, tin, aluminum, gold, copper, copper and alloys thereof.

Furthermore, as the solvent-soluble inorganic compound used in producing the porous metal material of the present invention, an inorganic compound that can be dissolved in a suitable solvent such as water, alkali, acid, alconopacetone, dimethylformamide, etc. is used. However, particularly preferred are water-soluble inorganic salts.

Next, a preferred embodiment of the method for producing an air-permeable high-porosity metal of the present invention will be described. First, an alkali metal salt such as sodium chloride or potassium chloride, or an alkaline earth metal salt such as barium chloride is dissolved, The mixture is poured into a mold to obtain an ingot, which is crushed and classified to obtain the metal salt particles.

Next, metal salt particles having a predetermined size depending on the purpose of use are placed in a heat-resistant container having a predetermined shape, and heat-treated in the atmosphere for several hours just below the melting point of the metal salt to form a sintered body of the metal salt. obtain. FIG. 1 is a schematic diagram of the microstructure of metal salt particles 1 and voids 2 before sintering, and FIG. 2 is a schematic diagram of the microstructures of metal salt particles 1' and voids 2 after sintering, As can be seen from these figures, the particles l that were in point contact before sintering changed to surface contact after sintering. In this case, the longer the heat treatment time, the more the contact area ratio between each particle increases, but if the heat treatment time is too long, independent voids begin to form, a so-called oversintered state, and the molten metal 1 Since it cannot be press-fitted from the outside, care must be taken to avoid over-sintering.
The lower limit of the porosity in the metal salt sintered body is 1
Therefore, the heat treatment time is adjusted; C. Therefore, the porosity of the sintered body is controlled to be in the range of 15 to 50%.

It should be noted that the voids appear to be independent when viewed at tC°C in Figure 2, but this is because they are shown two-dimensionally, and the voids are continuous in the vertical direction of the page. It is something that exists.

Next (・Fig. 3 is a cross-sectional explanatory diagram of the D outlet casting apparatus, in which the metal salt sintered body obtained as described above is loaded into the mold 3 of the pressure casting apparatus, and the electric or The desired molten metal 4, which has been preheated to a predetermined temperature with gas, is poured onto the top of the sintered body 5, and subjected to pressure using a force-pressing bunch 6 to infiltrate the molten metal into the voids of the sintered body.In this case, The press-in pressure needs to be greater than the flow resistance of the molten metal flowing through the voids in the sintered body, but a pressure of 30 to 14 or higher is usually sufficient.The preheating temperature is determined by the following formula: tp
The above should be selected below the freezing point of the press-fit metal.

Here, door is the freezing point of the molten metal (Cc), H" is the latent heat of solidification of the molten metal (cal/&), and moromi is the density of the molten metal (9, I
c center, ■1 is the volume ratio or filling rate that the metal salt particles occupy in the space, dp is the density of the metal salt particles (, rA, i), Cp
is the specific heat of metal salt particles (ca1/g/C)'l: indicates.

Next, the composite consisting of the metal salt and the metal thus obtained by heating at 5 K is washed with water, and only the metal salt is eluted to obtain the desired porous metal. In this case, since the metal salt has a relatively high solubility in water, running water alone is sufficient, but finishing by ultrasonic cleaning is more effective. FIGS. 4 and 5 are schematic diagrams of the microstructure of the porous metal obtained in this way, showing metal parts 7, 7' and void parts 8, 8.
It consists of '. Figure 4 shows a porous metal material obtained from metal salt particles that are in point contact, and has a structure in which the material in Figure 1 and the voids are all replaced, and Figure 5 shows a porous metal material that is made from metal salt particles that are in point contact. It is a porous metal material obtained from salt particles, and has a fixed structure by replacing the material and voids in Figure 2. That is, if ordinary sintered metal is considered positive, the porous metal body of the present invention is equivalent to negative, and this is also the reason why the product of the present invention has a high porosity of 50 to 85 inches.

Note that if the metal salt particles are in point contact as shown in Figure 1,
In the process of eluting metal salts, it takes a long time to elute, but according to the method of the present invention, since the metal salt particles are in surface contact, the elution time can be shortened.

However, as this surface contact progresses, the porosity decreases, so if you do not want to lower the porosity too much depending on the purpose of use, you can reduce the surface contact ratio.

Preferred examples of the alkali metal salts or alkaline earth metal salts used in the present invention include sodium chloride, sodium nitrite, or barium chloride, and the injection metals include metals with a melting point of about 1150°C or less and All alloys are applicable.

According to the method of the present invention, it is possible to extremely easily obtain a high-porosity, air-permeable metal with a porosity that is two to three times higher than that of conventional sintered metals. Furthermore, the method of the present invention has the following features. That is, (1) since the metal salt particles can be easily sized, the pore diameter of the finally obtained porous metal can be easily controlled. (2) By controlling the shape of the metal salt particles in advance, the shape of the pores in the porous metal can be controlled. (3) Holes can be drilled or cut into the metal salt sintered body. Of course, prepared rods, pipes, partition plates, etc. can also be fused with metal salt particles and sintered.

(4) When obtaining a low-melting porous metal, the energy required for sintering can be saved by using a low-melting metal salt. (5) Metal salts can be easily eluted and recycled. (6) By using a metal salt with a high melting point, it is also possible to produce foamed cast iron.

The breathable high porosity metal of the present invention has a porosity of 50 to 8.
5, which is extremely high compared to conventional products, and therefore has an extremely large surface area.It is particularly suitable for applications that require a large surface area, such as heat exchangers, filters, and catalysts.

Next, the present invention will be explained in more detail using an example ψ1j.

Example 1 Nitrous Acid IJum was melted, solidified, and then crushed and classified to obtain sodium nitrite particles of 350 to 590 microns. These particles were placed in a graphite container with an inner diameter of 25 mm and a height of 30 mm, and heat-treated at 270°C for 5 hours in the air.
An IJium sintered body was obtained.

This sintered body was placed in a cast iron mold with an inner diameter of 30 mm and a height of 50 mm, and preheated to 150° C. in an electric furnace. Pure tin with a melting point of 232°C was poured into the upper part of the mold, and the bath molten tin was pressurized with a punch at a pressure of 30 kg/2 J. The composite of sodium nitrite and tin thus obtained by V-filtering was washed with water to obtain air-permeable porous tin having a porosity of 74.

Example 2 Sodium chloride particles of 1,190 to 1,680 μm were prepared in the same manner as in Example 1, and the particles were placed in a mold with an inner diameter of 30 m and a height of 100 m.
After heating the tap light in a graphite container of
A sintered body of IJium was obtained. This was placed in a cast iron mold with an inner diameter of 3.0 mm and a height of 120 mm, and after preheating to 480°C, 12% 5
The i-A1 alloy was press-fitted in the same manner as in Example 91J1.

The thus obtained composite was washed with water and subjected to an ultrasonic cleaner to obtain an air permeable porous aluminum alloy having a porosity of 60%.

Example 3 Sintered chloride particles f obtained by the same method as Example 2: After preheating to 950°C, pure I particles were press-fitted in the same manner as Example 2, and the diameter was 29 mm and the height was A piece of breathable porous pure copper of 90 mm was obtained. The porosity of this material was 69%.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the microstructure of metal salt particles before sintering, Figure 2
The figure is a schematic diagram of the microstructure of metal salt particles after sintering, Figure 3 is a schematic diagram of a 710 pressure casting apparatus, and Figure 4 is a schematic diagram of the microstructure of a porous metal obtained from metal salt particles in point contact. figure,
FIG. 5 is a schematic diagram of the microstructure of a porous metal obtained from metal salt particles in surface contact. In the figure, symbols l and 1' are metal salts, 2, 2', 8, and 8' are hole parts, 3 is a mold, 4 is molten metal, 5 is a metal salt sintered body, 6 is a pressurizing punch, 7. 7' is metal. Procedural amendment December 9, 1982 28 Name of the invention Porous metal materials and their manufacturing method 3 Relationship with the case Patent applicant 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo (114) Industrial Technology Director Makoto Ishizaka -4, Number of inventions increased by 6 amendments voluntarily by designated agent 0 7, Subject of amendment Full text of amended specification 11 Title of invention Method for producing breathable metal material 2, Claim 1 Solvent soluble 2. The method according to claim 1, wherein the inorganic compound is completely press-fitted into the voids of the fired body in a predetermined shape, and the solvent-soluble inorganic compound is a water-soluble inorganic salt. 3. The method according to claim 2, wherein the bathable inorganic salt is an alkali metal salt or an alkaline earth metal salt. 3. Detailed Description of the Invention The present invention relates to a method for producing a breathable metal material, and more specifically, by sintering a sintered body of a solvent-free 1-11 compound, it is possible to obtain excellent properties as a functional material. The present invention relates to a method for producing a highly porous, breathable metallic material having a high porosity. In general, porous metals are divided into independent pore types and continuous pore types depending on the form of the pores contained therein.The closed pore type has no air permeability, but the continuous pore type has air permeability because the pores are open to the outside air. It has a sexual nature. This open-pore, air-permeable metal is widely used as a highly functional material, such as oil-impregnated bearings, filters, heat exchangers, electrodes, catalysts, and storage of special substances. Conventionally, breathable metal materials mainly consist of metal powder particles r(3)
It has been manufactured by sintering. However, it has been found from Ichikawa that in this sintering method, the porosity of the obtained air-permeable metal material is approximately determined by the filling ratio of the metal powder particles, so it is a low value of around 40 coefficients. If the material is cut and subjected to MIJ processing or plastic processing, it will inevitably become clogged and impair air permeability. By the way, as a method of obtaining a breathable metal material with high porosity, a mold is filled with sodium chloride powder, and a molten metal of a low melting point metal is poured onto the mold. A method in which a metal-sodium chloride particle composite is produced by pressurizing the molten metal into the interstices of IJum powder and solidifying it, and then dissolving the sodium chloride particles in this composite in water (Japanese Patent Publication No. 39-36
No. 52) has been proposed. However, in this method, the low melting point metal used is a metal with a melting point lower than the melting point of sodium chloride (<801 °C), and the shape of the resulting shredded product is such that the compaction of the IJium particles Since this is a prerequisite, there are problems such as the inability to obtain products with complex shapes or large-sized dyed products. Furthermore, in the Kome 1 method, the sodium chloride particles are preheated to a temperature below the freezing point of the molten metal to be press-injected, but as will be clear from the reasons described below, this is not practical when fully press-fitting the molten metal. This is a fatal flaw in the manufacturing process, and it is also the reason why breathable metals made using the M manufacturing method have not been put into practical use, even though about 20 years have passed since the patent application was filed. When producing a metal-inorganic salt particle composite by the zero-pressure SOI method, in order for the molten metal to flow through the narrow gaps between the particle layers, it is necessary to prevent it from coagulating. This is why the invention maintains the preheating temperature of the particle layer above the freezing point of the incoming molten metal. However, under these preheating temperature conditions, the following problems cannot be solved. In other words, the molten metal is subjected to hydrostatic pressure of several tens of kg/ca or more and ages, so the mold and punch clearer/
ii) The particles are violently dispersed from the air vent, pressurized further, and the punch continues to descend until the particle layer 1 begins to compress, causing particle destruction and plastic deformation. Ru. In order to avoid this kind of phenomenon, it is necessary to stop applying pressure at the same time, but if you stop applying pressure, the effect of pressurized coagulation will not be obtained, and the inside of the composite material will be damaged. Shrinkage cavities occur and good material cannot be obtained. Furthermore, forced cooling from the outer surface of the mold is required for solidification, which significantly impedes workability. A method to solve the above problems all at once is to keep the temperature of the particle layer below the freezing point of the molten metal and use the particle layer and mold as a heat sink (heat escape). However, if the temperature is too low, the molten metal will solidify first and cannot be press-fitted as described above. When producing a metal-inorganic salt particle composite by the pressure casting method in this way, it is necessary and sufficient that the preheating temperature of the particle layer is in the range above a certain temperature (critical temperature) and below the freezing point of the molten metal. be. In view of these circumstances, the present inventors created a metal-inorganic compound particle composite by a pressure casting method, and then treated the inorganic compound particles in the composite with a solvent to dissolve them and close the pores. As a result of intensive research into methods for manufacturing highly breathable metal materials, we first created a sintered body of an inorganic compound that can be dissolved in a suitable solvent, and then used this sintered body as a molten metal. The molten metal is preheated to 70 degrees below the freezing point of the sintered body, and then the molten metal is compressed into the voids of the sintered body, and after cooling and solidifying for 1 hour, the -warm compounds are dissolved and removed. , 50
It is possible to economically and safely obtain a breathable metal material with a high porosity of less than 2%, which cannot be obtained by conventional sintering methods, and also to manufacture products with complex shapes or large shapes. The present invention was completed based on this finding. That is, the present invention involves molding a solvent-soluble inorganic compound into a predetermined shape and sintering it, and then converting the resulting sintered body into a sintered body having a temperature below its melting point and expressed by the formula % formula % (1), where TP is sintered. The preheating temperature of the solid body (°C), Tc is the critical preheating temperature (°C), TMlHM and DM are the freezing point of the molten metal or alloy (°C), and the latent heat of solidification (,:ni/y), respectively.
and density (f/era), v P ,
c P and D2 are respectively the volume proportion or filling rate occupying the space of the solvent-soluble inorganic compound particles, the specific heat (, 1y / ° C.) and density (f / ~) of the particles] Preheating to a temperature range expressed by Next, after compressing the molten metal or alloy into the voids of the sintered body and solidifying it,
The present invention provides a method for producing an air-permeable metal material, characterized in that the inorganic compound is eluted by treatment with a solvent. The breathable metal material and raw material of the present invention can be arbitrarily selected from metals or alloys used in ordinary metal materials. Examples of such things are cast iron, lead,
Examples include zinc, tin, aluminum, gold, silver, copper, nickel, and alloys thereof. The solvent i='l soluble inorganic compound used in producing the breathable metal material of the present invention may be any suitable solvent such as water, alkali, acid alcohol, acetone, dimethylformamide, etc. Although the above compounds can be used, preferred are (b) water-soluble inorganic salts;
Particularly suitable are prucari metal salts or alkaline earth metal salts. . Next, a preferred embodiment of the method for producing the aerated high-porosity metal material of the present invention will be described. First, an alkali metal salt such as sodium chloride or potassium chloride, or an alkaline earth metal such as barium chloride The salt is dissolved and poured into a mold to obtain an ingot, which is crushed and classified to contain the metal salt particles. Next, metal salt particles having a predetermined size depending on the purpose of use are filled into a heat-resistant container having a predetermined shape. Get a body. FIG. 1 is a schematic diagram of the microstructure of metal salt particles 1 and voids 2 before sintering, and FIG. 2 is a schematic diagram of the microstructures of metal salt particles 1' and voids 2' after sintering. As can be seen from these drawing forces, each particle was in point contact before sintering, but after sintering, the point contact changed to surface contact. In this case, the longer the heat treatment time, the higher the contact surface ratio between each particle, but if the heat treatment time is too long, independent voids will begin to form, a so-called oversintered state, and the molten metal will be used in the next step. Since it cannot be press-fitted from the outside, care must be taken to avoid over-sintering. The lower limit of the porosity of the metal salt sintered body to avoid oversintering is 15%, and therefore, the porosity of the sintered body is controlled within the range of 15 to 50% by adjusting the heat treatment time. Although the voids appear to be independent in FIG. 2, this is because they are shown two-dimensionally, and the voids are continuous in the vertical direction of the page. Next, FIG. 3 is a cross-sectional explanatory diagram of a pressure casting apparatus, in which the metal salt sintered body obtained as described above is loaded into the mold 3 of the pressure casting apparatus, and a predetermined shape is set by electricity or gas. After preheating to a temperature of 5. In this case, the press-in pressure needs to be greater than the flow resistance of the molten metal or alloy flowing through the gap in the sintered nail, but is usually 30 K.
9. /cr! The following pressure is sufficient for the first one. Thermal temperature TP, 1@ below the melting point of the sintered body, and selected within the unidirectional range expressed by the following formula (1)5, TI'>TP>T' (1
) where TL is the critical preheating temperature (c), TM, HM and D
M are the freezing point (°C), latent heat of solidification (7/f), and density (9/crd) of the molten metal or alloy, respectively, and vr'
, cP and DP are the volume proportion or filling rate occupying the space of the metal salt particle, and the specific heat of the particle (J/Y/℃)
and density (g/crtl). Next, the thus obtained composite consisting of the metal salt and the metal is washed with water, and only the metal salt is eluted to obtain the desired air-permeable metal material. In this case, since the metal salt has a relatively high solubility in water, running water alone is sufficient, but ultrasonic cleaning ξ1 is even more effective. FIGS. 4 and 5 are schematic diagrams of the microstructure of the breathable metal material obtained in this manner, which consists of metal parts 7, 7' and void parts 8, 8'. The fourth tooth is a breathable metal material obtained from metal salt particles that are in point contact, and has a structure in which the material and voids in Fig. 1 are replaced, and the groove is the fifth tooth.
The figure shows an air-permeable metal material obtained from metal salt particles that are in surface contact, and has a structure in which the material and voids in Figure 2 are replaced. That is, if ordinary sintered metals are considered positive, the breathable metal body of the present invention is equivalent to a negative, and this is also the reason why the product of the present invention has a high porosity of 50 to 85%. Note that if the metal salt particles are in point contact as shown in Figure 1,
In the process of eluting metal salts, it takes a long time to elute, but according to the method of the present invention, since the metal salt particles are in surface contact, the elution time can be shortened. However, as this surface contact progresses, the porosity decreases, so if you do not want to lower the porosity too much depending on the purpose of use, you can reduce the surface contact ratio. As the solvent-soluble inorganic compound used in the present invention, alkali metal salts or alkaline earth metal salts are preferable. For example, sodium chloride, sodium nitrite, and barium chloride for mushrooms are preferable. is about 150
All metals and alloys below 0°C are suitable. For example, the table shows the relationship between the filling ratio of barium chloride particles and the critical preheating temperature for various metals when barium chloride, which has the highest melting point (962° C.) as a metal chloride, is used. The critical preheating temperature must be lower than the melting point of the metal salt,
Therefore, as can be seen from the table, when barium chloride is used as the metal salt, it is possible to produce breathable nickel with a porosity of up to 60%. Note that the critical preheating temperature of the part m in () in the table is higher than the melting point of barium chloride, so it cannot be manufactured using barium chloride. An air permeable metal material with a high porosity of 2 to 3 times or more can be obtained very easily.Furthermore, the method of the present invention has the following features: (1) sizing of metal salt particles; (2) The shape of the pores in the breathable metal material can be controlled by controlling the shape of the metal salt particles in advance. (3) Drilling holes or making cuts in the metal salt sintered body can have the same effect as casting rods, pipes, partition plates, etc. into the final product.
have a blockage. . Of course, in advance, light the M rod, pipe, two-parted river root, wire mesh, etc. with metal salt particles;
May be sintered. (4) When obtaining a low-melting point permeable old metal material, the energy required for sintering can be saved by using a low-melting point metal salt. (5) Metal salts can be easily eluted and recycled. (6) By using a metal salt with a high melting point, it is also possible to produce porous cast iron. (7) Breathable aluminum and breathable magnesium, which are difficult to obtain by powder metallurgy, can be easily produced. The breathable high porosity metal material of the present invention has a porosity of 50
It is an epoch-making breathable material with a surface area of ~85%, which is extremely high compared to conventional products, and therefore has an extremely large surface area, and is particularly suitable for applications that require a large surface area, such as heat exchangers, filters, and catalysts. Next, the present invention will be explained in more detail with reference to Examples. Stream side 1 Sodium nitrite was melted, solidified, and then crushed and classified to obtain sodium nitrite particles of 350 to 590 μm. The particles were tap-filled into a graphite container with an inner diameter of 25 M and a height of 30 mm, and heat treated in the air at 270° C. for 5 hours to obtain a sintered ram body. This sintered body was placed in a cast iron mold with an inner diameter of 30mm and a height of 50mm, and preheated to 150°C in an electric furnace (critical preheating temperature 1
35℃). Pure tin with a melting point of 232° C. was poured into the upper part of the mold, and the molten tin was pressed in bunches at a pressure of 30 Kg/crd. The nitrate obtained in this way) IJ
The aluminum and tin composite was washed with water to obtain air-permeable porous tin with a porosity of 74%. Example 2 Sodium chloride particles of 1190-1680 μm were prepared in the same manner as in Example 1, and the inner diameter was 30 wl1 and the height was 10 μl.
After tap filling into a graphite container with zero vapor, heat at 800℃ for 3
A sintered body of IJium was obtained. This was placed in a cast iron mold with an inner diameter of 30 mm and a height of 120 mm, and after preheating to 480° C. (critical preheating temperature 410° C.), a 12% Si-A1 alloy was press-fitted in the same manner as in Example 1. The thus obtained composite was washed with water and further subjected to an ultrasonic cleaner to obtain an air-permeable porous aluminum alloy having a porosity of 60%. Example 3 After preheating the barium chloride particle sintered body obtained by the same method as Example 2 to 950°C (critical preheating temperature 803
°C), pure copper was press-fitted in the same manner as in Example 2 to obtain breathable porous pure copper having a diameter of 29 mm and a height of 90 TMI. The porosity of this material was 69%. 4. Brief explanation of the drawings Figure 1 is a schematic diagram of the microstructure of metal salt particles before sintering, Figure 2 is a schematic diagram of the microstructure of metal salt particles before sintering.
The figure is a schematic diagram of the microstructure of metal salt particles after sintering, Figure 3 is a schematic diagram of a pressure casting apparatus, and Figure 4 is the microstructure of an air-permeable metal material obtained from metal salt particles in point contact. Pattern diagram,
FIG. 5 is a schematic diagram of the microstructure of an air-permeable metal material obtained from metal salt particles in surface contact. In the figure, 1.1' is a metal salt, 2, 2', 8.8' are holes, 3 is a mold, 4 is a molten metal, 5 is a metal salt sintered body, 6 is a processing punch, 7, 7' is metal.

Claims (1)

[Scope of Claims] 1. A porous metal material made of a metal or alloy having a three-dimensional network structure in which pores communicating with the outside occupy 50 parts or more of the total volume. 2. A solvent-soluble inorganic compound is molded into a predetermined shape and sintered, then a molten metal or alloy is press-fitted into the voids of this sintered body, solidified, and then treated with a solvent to sinter the inorganic compound. A method for producing a porous metal material, characterized by elution. 5. The method according to claim 2, wherein the cutting-soluble inorganic compound is a water-soluble inorganic salt. 4. The method according to claim 3, wherein the water-soluble inorganic salt is an alkali metal salt or an alkaline earth metal salt.