JPH02175803A - Porous metal material - Google Patents

Abstract

PURPOSE:To enable sintering without preforming and/or pressurizing at the time of sintering and to obtain a porous metal material having high porosity and isotropy by sintering an aggregate of curled metal short fibers. CONSTITUTION:This porous metal material is formed by sintering the aggregate of the curled metal fibers desirably curled to more than semicircle. The above porous metal material is easily sintered without preforming preceding to the sintering and/or pressurizing at the time of sintering. Then, the obtd. porous metal material is used for cushion material at high temp., sound absorbing material, heat insulating material, filtering material, etc.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to porous metal materials, particularly cushioning materials at high temperatures, sound absorbing materials, heat insulating materials, filtration materials, breathable mold materials, electrode materials, The present invention relates to a porous metal material with high porosity useful as a catalyst or its carrier, and a method for producing the same.

(Prior art) Conventionally, porous metal materials such as copper-based, nickel-based, or stainless steel-based materials have been mainly manufactured by sintering powdered raw material metals. In particular, it is difficult to obtain a material with a porosity of 80% or more at a thickness of 1M or more.

So in recent years, gold r/! , the porosity is 90-95 by sintering the fibers.
% of the material is being researched.

(Problems to be Solved by the Invention) However, the porous metal material made by sintering conventional metal fibers has greatly different properties between the direction on the plane including the fiber direction and the direction perpendicular to the core. Furthermore, there is a drawback that processing such as cutting and bending becomes difficult due to the fibers becoming an obstacle.

In addition, both powdered metal and metal fiber are sintered at high temperatures,
In particular, stainless steel is sintered at a high temperature of around 1200''C, and it is desired to lower the degree of sintering as much as possible.

The inventors of the present invention have made extensive studies to solve these drawbacks and satisfy the above requirements. As a result, as shown in Figure 1, an aggregate of curled short metal fibers has a high porosity and a high porosity when sintered. It has been discovered that it is isotropic and has the advantages of the above-mentioned powder sintered crystals and conventional fiber sintered crystals, and that the aggregate of such curled short metal fibers is similar to other fibers of the same type of metal. The present invention has been achieved based on the discovery that sintering is easier than powder and can be sintered without preforming prior to sintering and/or without pressurization during sintering.

That is, an object of the present invention is to provide a porous metal material with high porosity and isotropy, and to obtain such a porous metal material with industrial advantage.

(Means for Solving the Problems) Therefore, the object of the present invention can be easily achieved by a porous metal material formed by sintering an aggregate of curled short metal fibers.

(for production) The present invention will be explained in detail below.

The aggregate of curled short metal fibers used as a raw material in the present invention is substantially about 1 to 1
．． 5 cm or less, preferably about 0.5 cra or less, more preferably about 1M or less, and preferably curled into a semicircle or more, minute metal fibers, usually other than this length. In an aggregate of short metal fibers, it is possible that most of the countless metal fibers that make up the aggregate are curled to a clearly recognizable extent. It can be clearly distinguished from other metal fiber aggregates.

In addition, such curled short metal fibers are distinguished from other metal fibers in terms of their manufacturing method, and the process that has the effect of curling the manufactured short metal fibers into a semicircle or more is preferably used. It is included during the manufacturing process.

To give a specific example, in a non-oxidizing atmosphere, the surface of soft metals such as iron, copper, aluminum, lead, zinc, tin, nickel, chromium, gold, silver, platinum, magnesium, alloys thereof, or stainless steel. Another method involves pressing a rotating abrasive material to which abrasive grains are fixed, and scraping off short metal fibers from the core surface. Here, the non-oxidizing atmosphere is nitrogen, argon,
Refers to the state in which an inert gas such as helium is flowed into the atmosphere, or the metal surface is cooled with a solvent such as water, water-soluble grinding oil, or inert grinding oil to prevent oxidation, and the grinding conditions Any conditions may be used as long as the metal fibers can be cut out, but the peripheral speed of the abrasive material should be 500 to 2000 m/min,
The metal surface to be ground is 3 to 30 m/
It is preferable to move at min.

FIG. 1 is a schematic diagram for explaining the shape of curled metal short fibers obtained by using the method of scraping metal fibers from a metal surface with the above-mentioned abrasive, and 1 and 2 in the figure are respectively 3 represents the tip and center portions of the curled metal short fibers, and 3 represents the outer diameter of the curled metal short fibers. The curled metal short fibers produced by the above method are determined by the rotational speed of the abrasive material in the manufacturing process, the strength of the pressure of the abrasive material on the metal surface, the diameter of the abrasive grains,
Its dimensions and shape vary depending on the depth of cut and the type of metal to be ground, etc., and the wall thickness of the tip is approximately 0.5 to 8 mm.
0 μm, the wall thickness at the center is about 5 to 1000 μm, and the outer diameter can vary in the range from about 250 to 1500 μm, but each is characterized in that the wall thickness at the center is larger than at the tip.

These curled short metal fibers, especially those so minute, may look like powder in appearance, and they are easier to sinter than other fibers or powders of the same type of metal, and can be heated at lower temperatures. Can be sintered under pressure. For example, in the case of stainless steel curled short metal fibers, the sintering temperature is preferably around 1000 to 1100°C, and the sintering temperature is 1200°C, which is the sintering temperature of the conventional powder sintering method.
Around "C", the shrinkage becomes large and it may be difficult to maintain the porosity rather thickly.

The ease of sintering of this curled short metal fiber is due to the fact that compressive stress differs in each part of the fiber due to the excessive force applied during the manufacturing process.
This is thought to be due to an increase in the bending of dislocations.

The porous metal material of the present invention can include any porous metal material formed by sintering an aggregate of curled short metal fibers, regardless of its manufacturing process, and of course includes conventional powder powder. pre-formed into a sheet or bulk shape by a method used in the production process of fired crystals of shaped metals and/or other fibers, such as pressure molding using a mold, paper making, or a defibrated nonwoven fabric method. Includes porous metal materials manufactured by post-firing methods. Among these, papermaking is a method that applies almost the same paper manufacturing method to sheeting powdered metal or metal fibers. In the case of the porous metal material of the present invention, organic fibers such as cellulose fibers and CMC ( carboxymethylcellulose), PVA (polyvinyl alcohol) and PE
Among dispersion media such as O (polyethylene oxide),
It is preferable to select a combination as shown in Table 1 below and mix this with an aggregate of curled short metal fibers to form paper.
In this case, a smooth and uniform product with a porosity of about 50 to 95% can be obtained, and continuous production is also possible. At this time, it is preferable to adjust the viscosity appropriately depending on the thickness of the porous metal material to be manufactured.

Table 1 Pressure molding of curled short metal fibers can be performed in exactly the same way as conventional pressure molding of powdered metals, but the pressure during molding may be lower than that for powdered metals (for example, Pressure molding of stainless steel requires 6 to 13 tons/ci, but pressure molding of curled stainless steel short fibers requires 1 ton/ci.
/crl! A pressure of about 100 ml or less is sufficient. This is because curled short metal fibers are easier to entangle with each other than powder or other fibers due to their shape, and have good moldability.

The defibrated non-woven fabric method involves defibrating curled short metal fibers, forming a web, and laminating them to form a non-woven fabric. good.

In addition, as a method that has not been used in the conventional production of powdered metal or sintered crystals of metal fibers, there is a method that does not apply pressure.
A method of solidifying curled short metal fibers in a mold with an adhesive such as PVA or CMC or an organic binder such as melamine resin or acrylic resin, and firing after preforming, and an aggregate of curly short metal fibers without preforming. It is possible to adopt a method in which the material is directly loaded into a sintering container and sintered, and according to these methods, a product with a porosity of 50 to 98% can be easily produced.

The porous metal material of the present invention may be manufactured by sintering using any conventionally used jig such as ceramic or graphite, but it has excellent thermal shock resistance and has no adverse effect on the object to be sintered. It is possible to use silicic acid in places where it can come into contact with the sintered material, because it has a low generation of impurities that cause sintering, has high thermal conductivity, can be used in multiple layers, and has excellent durability. A graphite jig having a coating mainly composed of zirconium, especially (a) a tetraalkoxysilane whose alkoxyl group has 1 to 5 carbon atoms, a hydrolyzate of the tetraalkoxysilane, and a hydrolyzate of the tetraalkoxysilane; at least one silane compound selected from the group consisting of partial polycondensates; (b) zirconium tetraalkoxide whose alkoxyl group has 1 to 5 carbon atoms; a hydrolyzate of the zirconium tetraalkoxide; and a hydrolyzate of the zirconium tetraalkoxide. A graphite molded body is coated with or impregnated with a suspension containing at least one zirconium compound selected from the group consisting of partial polycondensates, (C) an organic solvent, and ((1) zirconium silicate powder, and dried. It is preferable to use a graphite jig. Sometimes, when the porous metal material to be manufactured is made of stainless steel, there may be harsh sintering conditions that other sintering jigs cannot withstand. It is particularly preferable to use a graphite jig made of graphite.

Furthermore, the form of the jig used for sintering and its usage may be selected depending on the type and shape of the object to be sintered (for example, jigs and usage as shown in FIGS. 2 to 8 can be considered).

2 to 8 are longitudinal cross-sectional explanatory diagrams of a jig that can be used for sintering curled short metal fibers and its usage. In each figure, 4 is an aggregate of curled short metal fibers, and 5 is an aggregate of curled short metal fibers. sintered container,
6 is an upper lid, 7 is a load plate, 8 is a sintered plate, 9 is a spacer, 1
0 represents the thickness adjustment plate.

Because of its good sinterability, aggregates of curled short metal fibers are
Although sintering is possible by scattering and loading the tray-shaped sintering container 5 as shown in Fig. 2 without applying pressure and firing without applying pressure, in order to improve the strength of the resulting porous metal material, As shown in FIG.
It is preferable to sinter the aggregate of curled short metal fibers, which is the object to be sintered, by applying light pressure using a sintering material. Of course, mechanical pressure may also be applied.

If these sintering jigs and sintering methods are used, and the load plate 7 and top lid 6 are sufficiently heavy, or the object to be sintered is sintered with sufficient mechanical pressure, The thickness of the porous metal material is equal to the thickness of the gap remaining between the top lid 6 and the bottom of the sintered container 5 when the upper M6 is completely fitted into the container 5, as shown in FIG. On the other hand, the porosity of the resulting porous metal material can be easily adjusted by adjusting the amount of the material to be sintered, such as an aggregate of curled short metal fibers or a preformed product thereof, loaded into the sintering container.

Furthermore, Section 5 explains the sintering jig for thick-walled products and its usage.
As shown in the figure, there is a different thickness v between the upper lid 6 and the object to be sintered 4.
If the four-section plate 10 is inserted, the thickness of the porous metal material obtained can be changed simply by changing the thickness of the thickness adjustment plate 10 used, without changing the sintered container 5 or the top lid 6.

In addition, when manufacturing a plurality of porous metal plates at the same time, as shown in FIG. As shown in FIG. 8, it is convenient to use a sintering base plate 8 and a spacer 9 as a sintering jig, and to adjust the thickness of the product depending on the thickness of the spacer 9 used. Furthermore, it is relatively easy to obtain irregularly shaped products using the porous metal material of the present invention. As an example, FIG. 6 shows a sintering jig for a hollow cylindrical shape and its usage.

The sintering conditions may be lower than those for 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 of pressurization depends on the required porosity. The most important feature of the porous metal material of the present invention is that it can be sintered and manufactured at a lower temperature and under lower pressure.

The thus obtained porous metal material of the present invention can be freely manufactured into products having various properties in terms of porosity and pore diameter, and since it is a metal material, it is heat resistant, and if the metal is selected as the material, A product that can withstand considerable high temperatures and has excellent corrosion resistance can be obtained, and can be used for cutting, machining, grinding, electrical discharge machining, water treatment, etc.
It can be easily processed by jet, laser processing, etc., and irregularly shaped products can also be manufactured easily, and a variety of uses can be considered by taking advantage of these excellent properties.

For example, applications that take advantage of the small pore size and breathability include dust collection, gas filters such as air filters, and filtration of water, aqueous solutions, vegetable oils, mineral oils, and synthetic resins used as raw materials for films and spinning. Alternatively, filtration materials such as liquid filters for separating synthetic intermediates can be mentioned. In addition, a mold for molding resin or elastomer, that is, a mold,
When the porous metal material of the present invention is used as a material for part or all of a mold for casting, injection, etc., the molten resin or elastomer will not leak due to its small pore diameter and breathability, and additional air venting will be required. It can be molded without making any holes, and it is easy to make irregularly shaped molds.

The porous metal material of the present invention is highly effective as a high-temperature component in the exhaust system of an automobile or 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 has particularly excellent heat insulation, heat resistance, and corrosion resistance, and can be used in a wide range of fields.

In addition, applications utilizing the large surface area of the present invention include applications for electric rod materials and catalyst carriers. The porous metal material of the present invention made of nickel can be suitably used as a single rod connection terminal for high-temperature fuel cells or a porous electric scraper for a Nirakadomi pond, and the product of the present invention is also suitable as a catalyst carrier.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example) An aggregate of curled short metal fibers having a shape as shown in FIG. 1 of stainless steel J I 'J grade 304,
The average wire diameter of the end indicated as 1 in Figure 1 is 1 to 5 μm.
, the bulk density of the curled short metal fibers having an average wire diameter of 5 to 30 μm at the center, indicated by 2, and an average curl diameter of 200 to 350 μm, indicated by 3, 0.3 to 0.4 g/cIf
The aggregate of i was defibrated and sprayed into a graphite container in which a film containing zirconium silicate as a main component was formed on the parts that could come into contact with the object to be sintered, and these were stacked as shown in Fig. 7.
When sintered for 1 hour at 1100°C, dew point -40°C in a reducing atmosphere, the thickness was 10 marks, the width was 100-1, the length was 30
A porous metal material of 0.0 cm was obtained. The properties of the nuclear porous metal material were as shown in Table 2.

(Example 2) 1 part by weight of bulb was added to 46 parts by weight of water and beaten in a beating machine. To 25 g of beaten bulb, 10 f of water, 2 g of polyethylene oxide, and the same curled metal shorts as used in Example 1 were added. After adding 500 g of each fiber aggregate and stirring for 60 minutes, one-fifth of it was made into paper using a sheet machine, drained with a roll, applied to a drain press, and dried to a thickness of 2M and a width of 300 mm.

A curled short metal fiber composite paper with a length of 500M was obtained.

In addition, polyvinyl alcohol 10 is used as a binder for papermaking.
g was added just before the end of the dehydration process using the sheet machine.

When the composite paper was stacked as shown in FIG. 8 and sintered in the same manner as in Example 1, it had a thickness of 1.5 mm, a width of 300 mm, and a length of 50 mm, having the properties shown in Table 2.
A plate-shaped porous metal material of 0 mm was obtained.

(Example 3) The same aggregate of curled short metal fibers used in Example 1 was loaded into a compacting mold slightly smaller than the sintering container described below, and a surface pressure of 1. Press with Ot, /C(,
A preformed product with a thickness of 60 mm, a medium diameter of 200 mm, a length of 300 mm and a porosity of 40% was obtained, and this was placed on a part of the object to be sintered having the shape indicated by 5 in FIG. A graphite sintered container with a coating formed thereon, which was sintered in a reducing atmosphere at 1100°C and a dew point of -40°C for 1 hour in a sintered container with a diameter of 200 mm and a length of 300 mm. A plate-like porous metal material having properties as shown in Table 2 and having a thickness of 60 plates and a length of 200 mm and a length of 300 mm was obtained.

(Example 4) The same aggregate of curled short metal fibers used in Example 1 was charged into the same sintering container used in Example 3, and the upper lid and load plate were stacked on top of each other, and the 0.1kg/cff
Sintering was started with an initial load of 200 m and 300 m long, having the properties shown in Table 2 under the same conditions as in Example 3.
A plate-like porous metal material was obtained.

(Examples 5 and 6) Curled copper short metal fibers were used instead of stainless steel as raw materials, and the temperature and dew point during sintering were 800°C.
The same procedure as in Examples 1 and 2 was carried out except that the temperatures were set at -35°C and -35°C, respectively, and a plate-like porous metal having the same dimensions as in Examples 1 and 2 and the properties shown in Table 2 was obtained. was gotten.

(Examples 7 and 8) Using nickel curled short metal fibers instead of stainless steel as raw materials, the temperature and dew point during sintering were set to 10
Example 1 except that the temperatures were 00°C and -35°C, respectively.
By carrying out exactly the same procedures as in Examples 1 and 2, plate-shaped porous metal materials having the same dimensions as in Examples 1 and 2 and properties shown in Table 2 were obtained.

Table 2 (Effects) The porous metal material of the present invention combines the advantages of other conventional sintered metal fiber products and isotropic powder metal sintered products, and has a high porosity. , has excellent breathability, heat insulation, and processability.
Cutting, machining, polishing, electrical discharge machining, water jet,
Various processing methods such as laser processing can be applied, and it can be manufactured at a lower temperature and pressure than conventional porous metal materials, and the porosity can be easily adjusted.It has a wide range of uses and has great industrial benefits. This is what we provide.

[Brief explanation of the drawing]

FIG. 1 is an example of curled short metal fibers used as a raw material for the porous metal material of the present invention, and is a schematic diagram of curled short metal fibers produced by a method of scratching a metal block with an abrasive. 2 to 8 are explanatory longitudinal cross-sectional views of the sintering jig used for manufacturing the porous metal material of the present invention. DESCRIPTION OF SYMBOLS 1... Tip part of curled short metal fibers, 2... Center part of curled short metal fibers, 3... Outer diameter of curled short metal fibers, 4... Collection of curled short metal fibers. Body, 5...
Sintering container, 6... Top lid, 7... Load plate, 8... Sintering base plate, 9... Spacer, 0... Thickness adjustment plate. Applicant: Toyo Carbon Co., Ltd.

Claims (1)

[Claims] (1) A porous metal material made by sintering an aggregate of curled short metal fibers.