JP2724617B2 - Porous metal material - Google Patents

Description

The present invention relates to a porous metal material, and particularly relates to a cushion material, a sound absorbing material, a heat insulating material, a filtering material, a permeable material, an electrode material at a high temperature. The present invention relates to a porous metal material having a high porosity useful as a catalyst or a carrier thereof.

(Prior art) Conventionally, porous metal materials such as copper-based, nickel-based, and stainless steel-based materials are mainly produced by sintering powdery raw metal, but the porous metal materials thus produced are porous. The porosity is limited, and it is particularly difficult to obtain a material having a porosity of 80% or more with a thickness of 1 mm or more.

Therefore, in recent years, a method of sintering a metal fiber to obtain a material having a porosity of about 90 to 95% has been studied.

(Problems to be Solved by the Invention) However, the properties of a porous metal material obtained by sintering a conventional metal fiber greatly differ between a direction on a plane including a fiber direction and a direction perpendicular to the plane. Further, there is a drawback that the fiber becomes an obstacle to make processing such as cutting and bending difficult.

Further, both powdered metal and metal fiber are sintered at a high temperature. In particular, sintering of stainless steel is performed at a high temperature of about 1200 ° C., and it is desired to lower the sintering temperature as much as possible.

The present inventors have solved the above drawbacks and have studied diligently to satisfy the above requirements. As a result, as shown in FIG. 1, the present invention has a specific fiber form in which the thickness at the center is larger than the thickness at the protruding end. The aggregate of the curled short metal fibers, when sintered, has a high porosity and isotropic, and has the advantages of the powder sintered product and the conventional fiber sintered product. In addition, the aggregate of such curled metal short fibers is easier to sinter than other fibers and powders of the same kind of metal, and can be formed without preforming and / or sintering prior to sintering. They have found that they can be sintered, and have reached the present invention.

That is, an object of the present invention is to provide an isotropic porous metal material having a high porosity and to obtain such a porous metal material in an industrially advantageous manner.

(Means for Solving the Problems) However, the object of the present invention is to make the thickness of the protruding end portion less than 0.
5-80 μm, center thickness 5-1000 μm, outer diameter 250-
Within the range of 1500μm, the thickness at the center is greater than the tip,
It can be achieved by a porous metal material obtained by sintering an aggregate of curled metal short fibers having a fine metal fiber shape curled into a semicircle or more.

(Operation) Hereinafter, the present invention will be described in detail.

The aggregate of the curled metal short fibers used as a raw material in the present invention is substantially in the range of about 1 to about a level generally classified as short fibers.
1.5 cm or less, preferably about 0.5 cm or less, more preferably about
This is a minute metal fiber having a length of 1 mm or less, preferably curled into a semicircle or more, and in an aggregate of other short metal fibers of this length, which is usually innumerable, Most of the metal fibers are unlikely to be curlable to any appreciable extent, and in this respect the aggregate of curled metal short fibers and the aggregate of other metal fibers can be clearly distinguished. .

Further, such a curled metal short fiber is also distinguished from other metal fibers in the production method, and a step having some action of curling the produced metal short fiber preferably into a semicircle or more is performed. It is included during the manufacturing process.

To give a specific example, under a non-oxidizing atmosphere, iron,
Copper, aluminum, lead, zinc, tin, nickel, chromium,
There is a method in which a rotating abrasive material having abrasive grains fixed thereto is pressed against the surface of a soft metal such as gold, silver, platinum, magnesium, an alloy thereof, or stainless steel to scrape short metal fibers from the surface. Here, the non-oxidizing atmosphere is nitrogen, argon, flowing an inert gas such as helium into the atmosphere, or cooling the metal surface with a solvent such as water, water-soluble grinding oil, and inert grinding oil. It refers to a state where it is not oxidized, and the grinding conditions may be any conditions as long as the metal fiber can be cut out, but the peripheral speed of the grinding material is 500 to 2000 m / min, and the metal surface to be ground is applied to the grinding material. On the other hand, it is preferable to move at a speed of 3 to 30 m / min.

FIG. 1 is a schematic view for explaining the shape of a curled metal short fiber obtained by using a method of scraping a metal fiber from a metal surface with the above-mentioned abrasive, wherein 1 and 2 in the figure are respectively the same. The point and the center of the curled metal short fiber, and 3 represents the outer diameter of the curled metal short fiber. The curled metal staple fibers produced by the above method include the rotational speed of the abrasive in the manufacturing process, the strength of pressing the abrasive against the metal surface, the diameter of the abrasive grains, the depth of cut, the type of metal to be ground, etc. Depending on the size and shape, the inner thickness of the point is about 0.5
~ 80μm, center thickness about 5-1000μm, outer diameter about 25
The thickness can vary in the range of 0 to 1500 μm, but in any case, it is characterized in that the thickness at the center is larger than that at the tip.

Such curled metal short fibers, especially minute ones, are so small that they can be seen as powder in appearance, are easier to sinter than other fibers or powders of the same kind of metal, and have lower temperatures and lower temperatures. It can be sintered under pressure. For example, in the case of a curled short metal fiber of stainless steel, the sintering temperature is preferably around 1000 to 1100 ° C. At around 1200 ° C, which is the sintering temperature of the conventional powder sintering method, the shrinkage becomes large and the porosity is rather increased. It may be difficult to keep large.

It is considered that the ease of sintering of the curled metal short fibers is due to the fact that an excessive force was applied in the manufacturing process, so that the compressive stress was different at various points of the fibers, and the Dislocation Kink (bending of dislocations) was increased. .

The porous metal material of the present invention can include any porous metal material obtained by sintering an aggregate of curled metal short fibers, regardless of the manufacturing process, and naturally includes conventional powders. Method used in the manufacturing process of sintered products of metal-like metal and / or other fibers, for example, pressure molding using a mold,
It includes a porous metal material produced by a method of preforming into a sheet or bulk by a method such as a papermaking or defibrating nonwoven fabric method and then firing. Papermaking is an application of the paper manufacturing method almost directly to sheeting of powdered metal or metal fiber. In the case of the porous metal material of the present invention, organic fiber such as cellulose fiber and CMC ( From the dispersion media such as carboxymethylcellulose), PVA (polyvinyl alcohol) and PEO (polyethylene oxide), select a combination as shown in Table 1 below and mix it with the aggregate of curled metal short fibers to form a paper. In this case, a thin and uniform product having a porosity of about 50 to 95% is obtained, and continuous production is also possible. At that time, it is preferable to appropriately adjust the viscosity according to the thickness of the porous metal material to be manufactured.

The pressure molding of curled metal short fibers can be performed in exactly the same way as the conventional pressure molding of powdered metal, but the pressure during molding may be smaller than that of powdered metal, for example, pressing of powdered stainless steel. Where the molding requires ⁶ to 8 ton / cm ² , the pressure of about 1 ton / cm ² or less is sufficient for pressure molding of curled stainless steel short fibers. This is because curled metal short fibers are more easily entangled with each other than powder or other fibers due to their shape, and have good moldability.

In the defibrated nonwoven fabric method, a curled metal short fiber is defibrated, formed into a web, and laminated to form a nonwoven fabric. This can be achieved by directly applying a method conventionally performed with other fibers or long metal fibers. Good.

In addition, as a method that has not been used in the production of conventional powdered metal or metal fiber sintered products, an adhesive such as PVA or CMC or an organic binder such as melamine resin or acrylic resin is used without applying pressure. It is possible to adopt a method in which the curled short metal fibers in the mold are solidified and pre-molded and fired, or a method in which the aggregate of curled short metal fibers is directly loaded into the sintering container and sintered without pre-forming. According to these methods, a product having a porosity of 50 to 98% can be produced very easily.

The porous metal of the present invention may be manufactured by sintering using any conventionally used jig such as ceramics and graphite, but it has excellent thermal shock resistance and adversely affects the material to be sintered. Since it gives little impurities and has high thermal conductivity, it can be used in multiple layers and has excellent durability. Zirconium silicate is used as a main component in places where the material to be sintered can contact. Jigs having a coating to be formed, in particular, (a) tetraalkoxysilane in which the alkoxyl group has 1 to 5 carbon atoms, a hydrolyzate of the tetraalkoxysilane, and a partial polycondensate of the hydrolyzate; At least one silane compound selected from the group consisting of: (b) a zirconium tetraalkoxide in which the alkoxyl group has 1 to 5 carbon atoms, a hydrolyzate of the zirconium tetraalkoxide, and the hydrolyzate. A suspension containing at least one zirconium compound selected from the group consisting of partial polycondensates of the pulverized product, (c) an organic solvent and (d) zirconium silicate powder is applied or impregnated to a graphite molded body, and dried. It is preferable to use a graphite jig made of, particularly when the porous metal material to be manufactured is made of stainless steel, since there may be severe sintering conditions that other sintering jigs cannot endure. It is particularly preferable to use a graphite jig coated with zircon.

The form and use of the jig used for sintering may be selected according to the type and shape of the material to be sintered. For example, the jig and use shown in FIGS.

2 to 8 are vertical cross-sectional views of a jig which can be used for sintering curled metal short fibers and a method of using the same. In each of the drawings, reference numeral 4 denotes an aggregate of curled metal short fibers; Denotes a sintered container, 6 denotes an upper lid, 7 denotes a load plate, 8 denotes a sintered plate, 9 denotes a spacer, and 10 denotes a thickness adjusting plate.

Due to the good sinterability of the aggregate of the curled short metal fibers, even if they are sprayed and loaded without pressure into a tray type sintering vessel 5 as shown in FIG. Although it is possible to sinter, in order to improve the strength of the obtained porous metal material, at the time of the sintering, as shown in FIG. It is preferable to sinter the assembly of short fibers by applying light pressure. Of course, it may be mechanically pressurized.

Using these sintering jigs and sintering methods, when using a sufficiently heavy load plate 7 and upper lid 6 or when sufficiently sintering the material to be sintered by mechanical pressing, the As shown in FIG. 4, the thickness of the porous metal material to be
The thickness of the gap between the upper lid 6 and the bottom of the sintering vessel 5 remaining when completely fitted into the sintering vessel 5 becomes equal to the thickness of the aggregate of curled metal short fibers to be loaded in the sintering vessel. The porosity of the resulting porous metal material can be easily adjusted by adjusting the amount of the sintering material such as the preform.

Further, as shown in FIG. 5 for explaining a sintering jig for thick products and its use, if another thickness adjusting plate 10 is inserted between the upper lid 6 and the sintering object 4, Thickness adjustment plate 10 to be used
By changing the thickness of the porous metal material, the thickness of the porous metal material can be changed without changing the sintering vessel 5 or the upper lid 6.

In the case where a plurality of porous metal plates are manufactured at the same time, as shown in FIG. 7, the sintered containers 5 each having a bottom portion formed smaller than the upper opening portion may be stacked and used. Is a sintering base plate 8 as a sintering jig as shown in FIG.
It is convenient to adjust the thickness of the product by using the spacer 9 and the thickness of the spacer 9 to be used. It is also relatively easy to obtain an irregular shaped product as the porous metal material of the present invention. As an example, FIG. 6 shows a sintering jig for a hollow cylinder and its use.

The sintering conditions may be lower in temperature and pressure than in the conventional sintering of powdered metal or other metal fibers.For example, in the case of stainless steel, the temperature is around 1100 ° C, and the pressure for pressurization depends on the required porosity. a ~1ton / cm ² or so, lower temperatures in this manner, to be more sintering-manufacturable at low pressure, which is the greatest feature of the present invention the porous metal material.

The porous metal material of the present invention thus obtained can freely produce products having various properties in terms of porosity and pore diameter, and since it is a metal material, it also has heat resistance. Products that endure considerable high temperatures and have excellent corrosion resistance can be obtained, and can be easily processed by cutting, cutting, polishing, electric discharge machining, water jet, laser processing, etc. Various uses can be considered by taking advantage of the characteristics.

For example, as applications that make use of the small pore size and air permeability, dust filters, gas filters such as air filters, or filtration of water, aqueous solutions, vegetable oils, mineral oils, synthetic resins as raw materials for film and spinning, etc. Alternatively, a filtering material such as a liquid filter for separating a synthetic intermediate may be used. Further, when the porous metal material of the present invention is used for a part of or a whole material of a molding die such as a resin or an elastomer, that is, a mold such as a molding die, casting, injection, etc., the pore diameter is small and the air permeability is low. Due to its properties, the resin or elastomer in the molten state does not leak and can be molded without separately providing a hole for venting, and it is easy to produce a deformed mold.

The porous metal material of the present invention has a great effect as a high sound component of an exhaust system of an automobile or an industrial internal combustion engine, particularly as a vibration / thermal expansion buffer material and a sound absorbing material. Among them, the stainless steel product of the present invention is particularly excellent in heat insulation, heat resistance, and corrosion resistance, and is expected to be widely used in this field.

In addition, applications utilizing the surface area of the present invention include applications for electrode materials and catalyst carriers. The porous metal material of the present invention made of nickel can be suitably used for an electrode connection terminal for a high-temperature fuel cell or a porous electrode for a nickel-cadmium battery, and the product of the present invention is suitable as a catalyst carrier.

 Hereinafter, the present invention will be described in more detail with reference to examples.

(Example) A set of curled metal short fibers having a shape as shown in FIG. 1 of JIS standard 304 of stainless steel, and an average thickness of a tip shown as 1 in FIG. An aggregate having a bulk density of 0.3 to 0.4 g / cm ² of a curled metal short fiber having an average outer diameter of 5 to 30 μm in the central portion shown by 2 and a curl diameter of 250 to 350 μm shown by 3 is solved. The fibers are spread and charged in a graphite container having a coating containing zirconium silicate as a main component at a place where the material to be sintered can come into contact with, and stacked as shown in FIG. 7 at 1100 ° C. in a reducing atmosphere. After sintering for 1 hour at a dew point of -40 ° C, a thickness of 10 mm and a width of 100 m
m, a porous metal material having a length of 300 mm was obtained. The properties of the porous metal material were as shown in Table 2.

(Example 2) 1 part by weight of pulp was added to 46 parts by weight of water, and 25 g of beaten pulp obtained by beating with a beater was mixed with 10 g of water and 2 g of polyethylene oxide. 500 g of the fiber aggregate was added and stirred for 60 minutes. One-fifth of the paper was made with a sheet machine, drained with a roll, drained, dried and dried to a thickness of 2 mm, a width of 300 mm, and a length of 50
A 0 mm curled short metal fiber composite paper was obtained. Incidentally, as a binder for papermaking, 10 g of polyvinyl alcohol was added just before the end of the dehydration step using a sheet machine.

The composite paper was stacked by the method shown in FIG. 8 and sintered in the same manner as in Example 1. As a result, a sheet having the properties shown in Table 2 and having a thickness of 1.5 mm, a width of 300 mm and a length of 500 mm was obtained. A porous metal material was obtained.

(Example 3) The same aggregate of curled metal short fibers as used in Example 1 was loaded into a compacting mold slightly smaller than the following sintering container, and a surface pressure of 1.0 t / h was applied by a hydraulic press. Pressed in cm ² and thickness 60
5 mm, width 200 mm, length 300 mm, and a porosity of 40% were obtained. The preform was made of zirconium silicate as a main component at a place where the sintered body having a shape represented by 5 in FIG. This is a graphite sintering vessel with a coating formed, width 200 mm, length 3
1100 ° C, dew point -40 ° C in a reducing atmosphere in a 00mm sintering vessel
After sintering for 1 hour, a plate-shaped porous metal material having the properties shown in Table 2 and having a thickness of 60 mm, a width of 200 mm, and a length of 300 mm was obtained.

(Example 4) The same aggregate of the curled short metal fibers used in Example 1 was placed in the same sintering container as used in Example 3, the upper lid and the load plate were stacked, and the weight per unit surface area was measured. Sintering was started under an initial load of 0.1 kg / cm ² , and sintering was performed for 1 hour under the same conditions as in Example 3. The sintering had the properties shown in Table 2 and had a thickness of 60 mm and a width of 200 mm. A plate-shaped porous metal material having a thickness of 300 mm was obtained.

(Examples 5 and 6) Except for using curled short metal fibers of copper instead of stainless steel as the raw material, and setting the temperature and dew point during sintering to 800 ° C. and −35 ° C., respectively, completely as in Examples 1 and 2, respectively. In the same manner, plate-shaped porous metals having the same dimensions as those of Examples 1 and 2 and having the properties shown in Table 2 were obtained.

(Examples 7 and 8) As a raw material, a curled short metal fiber of nickel was used in place of stainless steel, and the temperature and dew point at the time of sintering were set to 10 respectively.
Except that the temperature was changed to 00 ° C. and −35 ° C., it was made exactly the same as in Examples 1 and 2, respectively, and had the same dimensions as Examples 1 and 2, respectively, and had the properties shown in Table 2 A metal material was obtained.

(Effects) The porous metal material of the present invention combines the advantages of other conventional sintered products of metal fibers and sintered products of isotropic powdered metal, and has a high porosity and air permeability. Excellent processing, heat insulation, workability, various processing methods such as cutting, cutting, polishing, electric discharge machining, water jet, laser machining, etc. are applicable.
Compared to conventional porous metal materials, it can be manufactured under low temperature and low processing, the porosity can be easily adjusted, and its use is wide and offers great industrial benefits.

[Brief description of the drawings]

FIG. 1 is an example of a curled metal short fiber used as a raw material of a porous metal material of the present invention, and is a schematic diagram of a curled metal short fiber produced by a method of scratching a metal block with an abrasive. 2 to 8 are longitudinal sectional explanatory views of a sintering jig used for manufacturing the porous metal material of the present invention. 1 ... pointed end of curled metal short fiber, 2 ... center of curled metal short fiber, 3 ... outer diameter of curled metal short fiber,
4 ... an assembly of curled metal short fibers, 5 ... a sintered container,
6 ... top lid, 7 ... load plate, 8 ... sintered plate, 9 ... spacer, 10 ... thickness adjustment plate.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B01J 23/86 B01J 32/00 32/00 35/02 D 35/02 F01N 1/24 A F01N 1 / 24 3/28 Q 3/28 H01M 4/80 A H01M 4/80 8/02 Z 8/02 B30B 15/34 A // B30B 15/34 B01J 23/74 321A

Claims (1)

(57) [Claims] 1. The thickness of the central part is larger than the semicircle within a range of 0.5 to 80 μm, the thickness of the central part is 5 to 1000 μm, and the outer diameter is 250 to 1500 μm. A porous metal material obtained by sintering an aggregate of curled metal short fibers having a fine metal fiber shape curled into a shape.