JPH0692606B2 - Method for producing iron porous body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for producing a three-dimensional mesh-like iron porous body. A three-dimensional mesh-shaped porous body of iron is preferable, for example, as a structural material or a heat exchange material.

[Prior Art] JP-A-55-125202 is a method of producing a porous metal body by coating a porous resin core body with a paste composed of a metal powder and an organic binder and firing it. In this publication, an example of carbonyl nickel powder is described as the metal powder.
According to the findings of the present inventors, it is important to use extremely fine metal powder in this method. Since the metal powder by the carbonyl method is extremely fine, it is preferable as the metal powder used in this method, but since it is extremely expensive, the metal porous body produced also becomes extremely expensive.

As a raw material for normal (not porous) powder sintered steel,
Generally, atomized iron powder and carbonyl iron powder are used. In the method of crushing iron in a ball mill in the air, deformation occurs in low carbon steel and does not become powder, and in high carbon iron (cast iron, pig iron), crushing is possible, but the particle size of iron powder becomes fine. Then, the oxidation reaction becomes active on the surface of the iron particles, and there is a risk of ignition and explosion.

When cast iron or pig iron is crushed in water, iron can be finely crushed without the risk of ignition or explosion, but since iron oxide particles form a film such as oxides on the surface of iron particles, it is conventionally used for iron burning. It has not been neglected as an iron powder for the production of ingredients.

[Problems to be Solved by the Invention] The present invention discloses a method for completely and inexpensively producing a three-dimensional mesh-like iron porous body.

[Means and Actions for Solving the Problems] In the present invention, iron containing 2.0 to 4.5% by weight of C is used as a raw material for producing fine iron powder. Since iron containing 2.0% by weight or more of C is brittle and easy to crush, the crushing energy can be saved. C is also contained as a reducing agent for reducing oxides and the like formed on the surface of iron fine powder particles in the reduction sintering step described later. To make this reduction sufficiently, C is 2.
Include 0 wt% or more.

Iron containing an excessive amount of C is troublesome to handle because C crystallizes when the molten iron solidifies. Further, in the present invention, a C content of 4.5% or less as a reducing agent is sufficient.

Therefore, in the present invention, the C content of the raw material for producing the iron fine powder is 2.0 to 4.5%.

In the present invention, elements other than C are not particularly limited. Ordinary blast furnace pig iron contains 2.0 to 4.5% C and contains a small amount of Si.
Although it also contains Mn, P, etc., it can be used as a raw material for producing the iron fine powder of the present invention. Further, for example, when producing a porous body of iron having good oxidation resistance, iron further containing an alloying element such as Ni or Cr can be used. Therefore, the iron fine powder of the present invention is Si, Mn, P, Cr, Ni, Al, C for adjusting the components of the iron porous body.
Includes fine iron powder containing alloying elements such as u or powders thereof.

In the present invention, iron is a fine powder having an average particle size of 50 μm or less. When the average particle size is 50μ or more, when it is kneaded with a binder and applied to the skeleton of a porous polymer resin, the applied thickness becomes uneven, and pressing at high pressure like general powder sintered steel As a result, since the sintered binding force after sintering is weak, a homogeneous iron porous body cannot be obtained.
When the average particle size is 50 μm or less, preferably 5 to 20 μm, the kneaded product is viscous and a homogeneous iron porous body is obtained.

There are various wet pulverization methods, but it is easiest and desirable to pulverize them in water to obtain fine powder having an average particle size of 50 μm or less. When the average particle size is about 50 μm or more, the surface of iron particles is slowly oxidized and there is no risk of ignition or explosion. Therefore, crushing may be performed in the atmosphere. However, further pulverization into fine powder is performed in water. For example, iron powder pulverized in the atmosphere to an average particle size of 100μ can be easily pulverized into a fine powder having an average particle size of 50μ or less without fear of ignition or explosion by an underwater ball mill or the like.

FIG. 1 is a diagram showing the oxygen content of iron fine powder produced by this method. As shown in FIG. 1, the iron fine powder of the present invention contains 1 to 20% of oxygen due to the formation of a film such as an oxide on the surface of iron fine particles, but this film is not As it prevents oxidation of iron particles inside, it can prevent ignition and explosives.

The iron fine powder produced by the present invention is kneaded with a solution in which a binder is dissolved in water and applied onto the skeleton of a porous polymer resin.

As the binder, for example, CMC, polyacrylic, water glass or the like can be used. Kneading iron fine powder, water and binder,
The kneaded product is applied to the skeleton of the porous polymer resin by a method such as spraying or dipping.

As the porous polymer resin, for example, polyurethane foam can be used.

As shown in FIG. 1, when the average particle size of iron fine powder is small, the oxygen content thereof increases. When the oxygen content of the iron fine powder is large and the amount of the reducing agent is insufficient only with C contained in the iron fine powder, C is added when the iron fine powder and the binder are kneaded.
As the C to be added, for example, ground electrode powder or oil soot is used.
These are suitable as reducing agents because of their small particle size and good reactivity.

After applying the kneaded material, a degreasing process for removing the skeleton of the polymer resin is performed. In this degreasing process, the porous polymer resin coated with the kneaded material is heated to 300 to 350 ° C in a nitrogen atmosphere, for example,
Heat for ~ 3 hours.

The reduction sintering process of the present invention is performed at 800 ° C to 120 ° C after the degreasing process.
The heating is performed at 0 ° C. for about 60 minutes, for example.

In this step, C contained in the iron fine powder and C added during kneading reduce oxygen in the iron fine powder, and at the same time, sintering proceeds. In this reduction sintering step, the fine iron powder is arranged along the skeleton of the porous polymer resin, so that the gas generated by the reduction reaction can be smoothly desorbed and the heat transfer is also good. In the present invention, the oxygen contained in the iron fine powder is removed by C contained in the iron fine powder or C in the kneaded product, so that it is not necessary to make the sintering atmosphere reductive and an inert atmosphere is sufficient.

As described above, the present invention uses fine iron powder having an average particle size of 50 μ or less, fine iron powder is produced by crushing in water and contains 1 to 20% oxygen, and fine iron powder contains C 2.0-4.5%
It is remarkably different from the conventional technique in that it is made by using the contained iron and that oxygen of iron fine powder is reduced by C in the sintering process. That is, a normal (non-porous) powder sintered steel is sintered after being molded by a high pressure press or the like. Therefore, a sintered body can be obtained by using iron powder having a large particle size. Since the present invention does not perform the treatment by the high pressure press or the like, it is necessary to use fine iron powder having an average particle size of 50 μm or less in order to obtain a sound sintered body.

In ordinary (non-porous) powder sintered steel, when iron fine powder containing oxygen is used, the material deteriorates and cracks occur in the sintered body, so iron powder with very little oxygen is used. There is. Further, the above-mentioned Japanese Patent Laid-Open No. 55-125202 is not a technique using metal powder containing oxygen.

Since the surface of iron is easily oxidized, iron fine powder having an average particle size of 50 μm or less and containing no oxygen is extremely expensive. In the present invention, iron fine powder containing 1 to 20% of oxygen is used, but oxygen is reduced by C and the material is sound, and since the sintered body is a three-dimensional mesh-like porous body, the sintered body is cracked. No flaws will occur. Iron fine powder containing 1 to 20% oxygen has an average particle size of 50
Those of μ or less can be manufactured at low cost.

JP-A-55-125202 is not a technique for incorporating carbon into a metal powder or a paste composed of a metal powder and a binder. In the present invention, C is used for facilitating the pulverization of the iron fine powder and for reducing the oxygen contained in the iron fine powder, which makes it possible to inexpensively produce the porous iron body.

[Examples] (1) Molten iron having the following components was melted in an electric furnace.

C: 3.5%, Mn: 0.8%, Si: 0.1%, P: 0.01%, S: 0.01%, solute is dropped into the water stream to make quenched iron granules, then 50μ in a ball mill
To a mean particle size of 15 using wet grinding.
The value was μ, and iron fine powder having an oxidized surface (oxygen content 4.5%) was used. This was kneaded with iron fine powder: water: polyacrylic acid = 74: 25: 1 and applied onto a porous resin foam (200 mm × 200 mm × 30 mm) four times by a spray method. In a nitrogen atmosphere furnace
After being dried at 100 ° C. for 1 hour, it was treated at 300 ° C. × 1 Hr, 1100 ° C. × 1 Hr, and a heating rate of 50 ° C./hour to obtain a porous iron body having a sound appearance as shown in FIG.

The obtained iron porous body had the following analysis values, and oxygen contained in the iron fine powder was reduced.

C: 0.13%, Mn: 0.75%, Si: Trace%, P: 0.01%, S: 0.01%, O:
0.02% (2) Blast furnace hot metal was desiliconized and dephosphorized, and ferrochrome was added to this to obtain molten iron having the following structure.

C: 4.2%, Mn: 0.5%, Si: 0.01%, P: 0.005%, S: 0.005%, Cr:
0.30%. This molten iron was subjected to a mold cooling treatment, and subsequently a wet milling method was used to obtain iron fine powder (oxygen content 8%) having an average particle diameter of 10 μm or less and the surface of which was oxidized. This, iron fine powder: water: C
MC: Fine powder C = 73: 26: 0.2: 1: 5 was blended to make a kneaded product. Porous resin foam (200 mm x 200 mm x 10 mm) was dipped in this kneaded product and kneaded by the dipping method. Is applied to a porous resin foam and dried, and then degreased in a nitrogen atmosphere: 350 ° C x 1H
r, Reduction sintering: 1200 ° C. × 0.5 Hr was performed, and a healthy porous iron body similar to that shown in FIG. 2 was obtained. FIG. 3 is a schematic view of a cross section of the iron skeleton.

The obtained iron porous body had the following analysis values, and oxygen contained in the iron fine powder was removed.

C: 0.5%, Mn: 0.47%, Si: Trace, P: 0.005%, S: 0.005%, Cr:
0.29%, O: 0.03% [Effect of the Invention] According to the present invention, a three-dimensional mesh-like iron porous body can be manufactured safely and at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing the oxygen content of iron fine powder by the method of the present invention, FIG. 2 is a diagram showing an example of the appearance of the porous iron body of Example 1, and FIG. 3 is an iron skeleton of the porous iron body. FIG. 4 is a diagram showing an example of a cross section of FIG.

Front Page Continuation (72) Inventor Norio Mikami 2-6-3 Otemachi, Chiyoda-ku, Tokyo Within Nippon Steel Corporation (72) Inventor Masaru Meguro 5-3 Tokai-cho, Tokai City, Aichi Prefecture Steel stock company Nagoya Steel Works (72) Inventor Toshihide Masuda 1-1 Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Kurosaki Ceramics Co., Ltd. (72) Hiroshi Horiguchi 1-11 Maeda, Hachimanto-ku, Kitakyushu, Fukuoka (56) References JP-A-58-204137 (JP, A) JP-B-50-13206 (JP, B1)

Claims (2)

[Claims] 1. A step of pulverizing iron containing 2.0 to 4.5% of C in water to obtain fine powder having an average particle size of 50 μ or less, and kneading the fine powder with a binder to form a skeleton of a porous polymer resin. The step of applying, the degreasing step of heat-treating the applied material to remove the skeleton of the polymeric resin, and the heating of the material from which the skeleton of the polymeric resin has been removed causes the fine powder to contain oxides on the surface of the fine powder. A reduction and sintering step of reducing and sintering with carbon, and characterized by having an empty path of a skeleton where the porous polymer resin has disappeared,
Method for producing iron porous body 2. A step of pulverizing iron containing 2.0 to 4.5% of C in water to obtain fine powder having an average particle diameter of 50 μm or less, and kneading the fine powder with carbon powder and a binder to form a porous polymer. The step of applying the skeleton of the resin, the degreasing step of heat-treating the applied skeleton to remove the skeleton of the polymer resin, and the heating of the skeleton of the polymer resin to remove the oxide on the surface of the fine powder A reduction sintering step of reducing and sintering the carbon contained in the fine powder and the carbon powder kneaded with the fine powder, and having an empty path of the skeleton where the porous polymer resin has disappeared And a method for producing a porous body of iron