JPH1192894A - Composite material of iron or iron-base alloy and graphite, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To incorporate graphite in high proportion, to properly disperse graphite, and to provide high strength. SOLUTION: In the composite material of iron or iron-base alloy and graphite, fine graphite is contained by 30 to 70 vol.% in a matrix of iron or iron-base alloy and the graphite is uniformly dispersed. This composite material can be produced by adding a carbon powder by 30 to 70 vol.% to an iron or iron- base alloy powder, milling the resultant powder mixture, and carrying out sintering. A ball mill is used at the time of milling. Further, a powder of stainless steel is used as the iron-base alloy powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material of iron and graphite, or an iron alloy and graphite, and a method for producing the same, which is used for a molding material for glass molding or a high-temperature sliding material used at a high temperature. .

[0002]

2. Description of the Related Art Conventionally, cast iron is mainly used in a glass molding mold. However, there is a problem in glass wettability and mold releasability, and it is necessary to increase the amount of graphite. However, cast iron materials can only be manufactured with a graphite content of up to about 10 to 15% by volume. A material in which cast iron powder and graphite powder are mixed, molded and sintered to have a graphite content of 30% by volume cannot be used because the strength is low and the surface is rough. In view of this, the surface of the cast iron is coated with mineral oil and heated to carbonize or soot is adhered to improve the releasability.

[0003] Separately, conventionally used sliding materials for high temperature use include graphite particles or graphite powder mixed with copper alloy powder, aluminum alloy powder, iron alloy powder or the like, and then sintered after pressure molding. After sintering, rolling and the like are performed to produce a composite material having good slidability.

[0004]

However, in the former of the above-mentioned prior art, the working environment is deteriorated because soot is attached or mineral oil is carbonized, soot is not uniformly attached, and manual operation is difficult. There is such a problem. Further, in the latter, there are many pores, and graphite can be added only at about 30% by volume due to a problem in strength, and those having a large amount of graphite have low strength, have better slidability and abrasion resistance, and have high strength. Large things are required. In view of the above, an object of the present invention is to provide a high-strength composite material containing graphite at a high ratio and appropriately dispersing graphite.

[0005]

The composite material of iron or iron alloy and graphite of the present invention contains 30 to 70% by volume of fine graphite in the matrix of iron or iron alloy, and the graphite is uniformly dispersed. It is dispersed (claim 1).

[0006] The fact that fine graphite is contained in an amount of 30 to 70% by volume by this means means that graphite having less than 30% by volume is
Although there is not much difference in graphite content, releasability, and abrasion resistance from conventional graphite-containing materials, those containing 30 to 70% by volume of graphite exhibit excellent releasability and abrasion resistance, and 70% by volume of graphite. %, It is difficult for the base to be uniformly dispersed in the base, and the base is fragile. In this method, a large amount of fine graphite is dispersed in the iron or iron alloy of the base, so if it is used for a glass forming mold, it can be used as it is without attaching soot or applying mineral oil to carbonize it. In addition, it can be used as a high-temperature sliding material to have excellent slidability and good wear resistance.

When such a composite material is applied to a glass molding mold, the size of fine graphite in the matrix of iron or iron alloy is practically 100 μm or less, more preferably 50 μm or less. When applied to a high-temperature sliding material, there is no problem even if it exceeds 100 μm to some extent. When applied to a glass molding mold, the amount of graphite is preferably 30 to 70% by volume, more preferably 30 to 50% by volume. Since the glass molding mold requires sufficient strength and also requires durability, if the fine graphite exceeds 100 μm, the strength tends to be low, and if the amount of graphite exceeds 70% by volume, the strength is low. Is likely to be low, and the durability is reduced.

The method for producing a composite material of iron or iron alloy and graphite according to the present invention is characterized in that carbon powder is added to iron or iron alloy powder in an amount of 30 to 7%.
It is characterized in that after adding 0% by volume, the material is ground and then sintered (claim 2).

According to this means, the carbon powder is used without using the graphite powder, and when the powder is ground, the action of the carbon powder having less lubricity than that of the graphite powder having good lubricity causes the iron or iron to be ground. It is hard to slip between the iron alloy powder and the side where the carbon powder is ground, and the grinding efficiency is improved. By grinding iron or iron alloy powder with carbon powder added,
As the pulverization and mixing proceed, the finely divided carbon powder adheres to the surface of the fine iron or iron alloy powder particles in a film form. When this is subjected to sintering, the matrix powder particles come into contact with each other when pressed and formed as in normal sintering, and are integrated by heating, and the fine carbon powder between them is graphitized by the catalytic action of iron and Some enter C in the Fe structure. Then, C that has entered the Fe structure by cooling
Precipitates as graphite. The precipitated graphite fills the pores when there are pores in the sintered body. The sintered body has a state in which fine graphite is uniformly dispersed in the iron or iron alloy of the matrix. The matrix was made of iron or iron alloy,
This is because it has high strength and obtains the above-described graphitizing action. When the matrix is made of an iron alloy, it is possible to select and use an iron alloy suitable for the purpose of use, for example, having excellent corrosion resistance and oxidation resistance at high temperatures.

In the manufacturing method, it is preferable that a ball mill is used for the grinding. Ball mills include vibration ball mills, high energy ball mills, etc.
Any can be used. By using carbon powder instead of graphite powder as a raw material, lubrication between the steel ball and iron or iron alloy is poor, so that the grinding action is large and the time required for grinding can be shortened.

In the manufacturing method, the iron alloy powder is preferably a stainless steel powder. Since the matrix is stainless steel, it has excellent corrosion resistance and oxidation resistance at high temperatures, and also has excellent wear resistance because it produces hard carbide during sintering.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is as follows.
It is a composite material of iron and graphite, and its manufacturing method will be described. Pure iron powder (having a particle size of 150 μm or less) passing through a 100-mesh sieve and carbon black having an average particle size of 420 ° added at 30, 40, 50, and 60% by volume, respectively, were prepared. Milling was performed for 20 hours so that the particle size of the pure iron powder was 20 μm or less. In the obtained mixed powder, fine carbon powder adheres to the surface of each particle of the pure iron powder in a film form. Each of the mixed powders was filled in a graphite mold, heated to 1373 K by a high-frequency heating coil, and then press-formed to obtain a composite material.
The pressure was 150 kg / cm ² .

The structure of the composite material is ferrite and graphite. Ferrite is formed by connecting the grains of the original pure iron powder partially to each other, and graphite is a fine carbon powder grown by graphitization and filling the space where the ferrite is formed. I have. FIGS. 1A and 1B show micrographs of a composite material of iron and graphite containing 30% by volume of graphite to which 30% by volume of carbon black is added. According to this, it can be seen that fine graphite that looks black is uniformly dispersed in the ferrite of the base that looks white.

In the second embodiment, 1 is used as the iron alloy powder.
Stainless steel passing through a 00 mesh sieve (JIS S
US304) A powder obtained by adding carbon black having an average particle diameter of 420 ° to each of 30, 40, and 50% by volume to a powder is prepared, and each of them is ground by a vibrating ball mill for 20 hours to obtain a stainless steel powder having a particle diameter of 20 μm. The following was made. In the obtained mixed powder, fine carbon powder adheres to the surface of each particle of the stainless steel powder in a film-like manner as in the first embodiment. Each of the mixed powders was filled in a graphite mold, heated to 1373 K by a high-frequency heating coil, and then pressed at 150 kg / cm ² to obtain a composite material. The structure of the composite is carbide, austenite, and graphite.

The pure iron-graphite composite material of the first embodiment is:
It has a greater amount of graphite than conventional cast iron materials, and is excellent in wettability and mold releasability of molten glass, and can be used as a glass molding die. Since the graphite particles in the structure of the composite material are finely and uniformly dispersed, the surface is smooth, and the pattern due to the structure of the composite material is not transferred to the surface of the formed glass.

Table 1 shows the flexural strengths of the composite materials of the first and second embodiments and graphite as a comparative material. Conventionally, a high-C composite material could not be manufactured, but as shown in Table 1, a high-strength high-C composite material can now be manufactured. FIG.
Is a graph showing the relationship between the C content of pure iron-graphite and the bending strength in Table 1.

[0017]

[Table 1]

Table 2 shows the results of evaluating the wear resistance of the composite materials of the first and second embodiments and the graphite as a comparative material using a wear tester (Ogoshi type rapid wear tester). The opposite material is carbon steel for machine structure (JIS S45C, composition weight%
C: O. 45, Si: 0.25, Mn: 0.75,
P: 0.03 or less, S: 0.035 or less, balance Fe and unavoidable components), friction speed: 0.65 m / s, load: 6.5 kgf, friction distance 200 m, no lubrication, room temperature The test was performed. The comparative graphite was isotropic high-density graphite (bulk density: 1.77 Mg / m ³ , Shore hardness: 6)
5, a bending strength of 47 MPa) was used. As can be seen in Table 2, when the graphite content of the pure iron-graphite composite material becomes 40% by volume or more, it has the same abrasion resistance as graphite and SUS304.
-The graphite composite material has good wear resistance because hard carbide is not formed in the composite material. Figure 3 shows the SUS of Table 2
It is a graph of the relationship between the C content of 304-graphite and the specific wear.

[0019]

[Table 2]

[0020]

According to the first aspect of the present invention, since a large amount of fine graphite is dispersed in the iron or iron alloy of the base, when used in a glass molding mold, soot is attached or mineral oil is applied. Even if it is not carbonized, it can be used as it is to have good releasability, and it can be used for high-temperature sliding material to have excellent slidability and good wear resistance. To play. The invention according to claim 2 is advantageous in production because the grinding efficiency is improved by using the carbon powder without using the graphite powder, and is advantageous in sintering by using iron or iron alloy powder for the matrix. The carbon powder becomes graphitized and contains the target graphite, and also has a high strength as a matrix, so that the strength of the composite material can be ensured, and the graphite precipitated from the Fe structure fills the pores and becomes a denser structure. When an iron alloy powder is used, in addition to the above, there is an effect that the iron alloy can have properties such as corrosion resistance and oxidation resistance at high temperatures. The invention described in claim 3 has an effect that the grinding action is large and the time required for grinding can be shortened. The invention described in claim 4 has an effect of being excellent in corrosion resistance and oxidation resistance at a high temperature, and also has excellent wear resistance since a hard carbide is generated during sintering.

[Brief description of the drawings]

FIG. 1 shows a microstructure photograph of pure iron-30% by volume graphite according to a first embodiment of the present invention.
(B) is 400 times.

FIG. 2 is a graph showing the relationship between the C content and the bending strength of the pure iron-graphite composite according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a C amount and a specific wear amount of the pure iron-graphite composite material according to the first embodiment of the present invention.

Claims (4)

[Claims] 1. Fine graphite is placed in an iron or iron alloy matrix.
A composite material of iron or an iron alloy and graphite, wherein the composite material contains 0 to 70% by volume and the graphite is uniformly dispersed. 2. An iron or iron alloy powder containing 30 to 7 carbon powders.
A method for producing a composite material of iron or an iron alloy and graphite, which comprises crushing and sintering 0% by volume added. 3. The method for producing a composite material of iron or iron alloy and graphite according to claim 2, wherein a ball mill is used for said grinding. . 4. The method for producing a composite material of iron or an iron alloy and graphite according to claim 2 or 3, wherein the iron alloy powder is a stainless steel powder. Of manufacturing a composite material.