JP2631146B2 - Sintered metal body and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a sintered metal body and a method for producing the same, which has excellent corrosion resistance and good conformability to a mating member.
Further, it is an object of the present invention to provide a sintered metal body excellent in strength and a preferable production method thereof.

(Industrial application fields) Sintered metal bodies suitable for use as bearing materials and others, and technologies related to their manufacture.

(Prior art) It is anticipated that a sintered metal body can directly and mass-produce a target product by compacting, sintering, sizing, and the like, and that a lubricant and the like can be appropriately compounded and distributed. Therefore, it is widely adopted and widely used for bearing materials and the like. That is, for example, for sintered oil-impregnated bearings,
Household electrical appliances, as specified in B 1581-1976,
Various types of bearing materials such as cylindrical, flanged cylindrical, and spherical bearings used for audio equipment, office machines, agricultural machines, automobiles and other cargo handling equipment, etc. are specified in various ways. The materials and types are relatively wide, such as iron-copper, iron-carbon, iron-copper-carbon, iron-copper-lead, bronze, copper, and lead-bronze.

In addition, for example, in JP-A-56-51554, sintering a green compact using iron powder and brass powder has been announced,
Further, the present inventors have also proposed in Japanese Patent Application Laid-Open No. 60-200927 that iron powder, brass powder and nickel silver powder are used, and that a green compact made of a mixed powder thereof is sintered in a reducing atmosphere. I have.

Also, Japanese Patent Application Laid-Open No. 53-146203 (Japanese Patent Publication No.
In 6-4140), a compact obtained by compacting a mixture of 3 to 30% copper and a suitable lubricant with iron powder as the main component is placed in a container made of a material that can transmit atmospheric gas. And sintering in a hydrogen gas or reducing gas atmosphere furnace. That is, according to this method, zinc vapor generated by reduction of zinc oxide powder is adsorbed on copper powder and iron powder particles to form copper-zinc and iron-zinc alloys, and as the temperature increases, part of copper becomes iron particles. It is presumed that eutectic and iron-copper-zinc alloys are also formed.

(Problems to be Solved by the Invention) The above oil-impregnated bearings mainly composed of iron are excellent in skeletal strength and are preferable for high loads, but are limited in use because they are inferior in compatibility and corrosion resistance to mating members. .

On the other hand, a material mainly composed of copper or bronze has good adaptability and corrosion resistance, but is not suitable for high loads because of insufficient strength.

Iron-copper alloys (including iron-copper-lead, iron-copper-carbon, etc.) have intermediate properties between them, but are still insufficient in strength and corrosion resistance. In the case of using the iron powder and the brass powder disclosed in JP-A-56-51554 described above, the strength and the adaptability to the mating member are not sufficient, even if the corrosion resistance is favorable.

Japanese Patent Application Laid-Open No. Sho 60-200927 aims at sufficient corrosion resistance and a reduction in friction coefficient while securing strength by using nickel silver, but it does not always satisfy those characteristics. In addition, it is insufficient in conformity to a mating member such as a shaft.

Furthermore, in the above-mentioned Japanese Patent Publication No. 56-4140 (Japanese Patent Application Laid-Open No. 53-146203), even if a lead-zinc alloy (brass) is formed on the surface of the copper powder particles, it is only partially microscopic. As a result, iron-zinc alloyed particles and iron-copper-zinc alloy are mixed, that is, various alloy particles are mixed, so that the corrosion resistance, conformability, strength, and the like still tend to be insufficient.

"Constitution of the Invention" (Means for Solving the Problems) Powder in which at least 92% of the peripheral surface of the iron powder particles of 40 to 79.5 wt% is coated with the brass coating layer of 1.20.5 to 60 wt%. A sintered metal body characterized in that it is compacted and sintered with a porosity of 8 to 35 vol%.

2.19 ~ 59.7wt% of brass coating layer covers more than 38 ~ 79.2wt% iron powder particles more than 92% of the circumference of the powder, such as graphite, molybdenum disulfide, boron nitride or lead A sintered metal body containing one or more solid lubricants and having a porosity of 8 to 35 vol%, and is compacted and sintered.

3. Powder-molded copper-coated powder that covered 92% or more of the peripheral surface of iron powder particles of 45-80 wt% with a copper coating layer of 20-55 wt%, and sintered this powder compact with zinc oxide powder. A method for producing a sintered metal body.

4. Solids such as graphite, molybdenum disulfide, boron nitride, or lead in 95 to 99.5 wt parts of copper-coated powder particles, which cover at least 92% of the peripheral surface of iron powder particles of 45 to 80 wt% with a copper coating layer of 20 to 55 wt% A method for producing a sintered metal body, comprising mixing a lubricant powder in a ratio of 0.5 to 5 wt parts and sintering a green compact obtained by compacting the mixed powder with zinc oxide powder. Law.

Action 20.5-60wt% brass coating layer is 92% of the circumference of the iron powder particles
The above is covered. That is, if the brass coating layer is less than 20.5 wt%, it tends to be difficult to cover 92% or more of the peripheral surface of the iron powder particles, while if it exceeds 60 wt%, the amount of the iron powder particles does not reach 40 wt%. However, the improvement of the strength characteristics and the like of the sintered metal body provided by using the iron powder particles as nuclei becomes insufficient.

By covering at least 92% of the peripheral surface of the iron powder particles with the brass coating layer as described above, a sintered structure in the sintered alloy can be obtained substantially between single brass materials, Easy and stable compacting and sintering. Also, despite the fact that the sintered body has iron powder particles as its core, the surface of the iron powder particles is not exposed at all microscopically. It shows favorable corrosion resistance even under acidic conditions. Furthermore, since there is no exposure of the iron powder particles as described above, the conformability to the mating member is improved, the coefficient of friction is reduced, and the temperature rise during continuous rotation bearing is reduced, and the strength is improved as described above. It is excellent and can obtain the best properties as a bearing part etc. in combination with the stabilization of the sintered structure.

When the amount of the iron powder particles is 40 wt% or more, not only the strength characteristics as described above but also low cost can be obtained.

In addition, the stability of the sintered structure and the deterioration of the strength characteristics due to the blending of the solid lubricant due to the solidification are prevented, and the characteristics of the bearing material are advantageously increased.

Regarding the formation of the above-mentioned brass-like coating, one obtained by forming a copper coating on the iron powder particles by plating or the like is subjected to compacting and then using zinc oxide powder, that is, embedded in zinc oxide powder,
Alternatively, it is placed on a zinc oxide powder, and the zinc vapor generated by the reduction is adsorbed on the copper coating and brassified, thereby effectively reducing the melting point due to zinc adsorption, increasing the volume as a copper alloy, and improving wettability. Then, a stable brass coating is formed on the peripheral surface of the iron powder particles, and the pore structure at the time of compacting is densified to obtain a preferable sintered alloy body. In addition, since the brass conversion is achieved in the sintering process itself, it is particularly complicated.

By appropriately selecting the porosity of the sintered metal body in the range of 8 to 35 vol%, the strength characteristics according to each use can be obtained.

In particular, the porosity of the bearing body is 15 to 28 vol%, that is, the compact is compacted, sintered and appropriately sized to have a porosity of 15 vol% or more, so that the oil content of the bearing material is appropriate. To improve the lubrication performance. On the other hand, by ensuring that the porosity does not exceed 28 vol%, the strength is ensured, and excessive outflow and scattering of the impregnated oil lubricating oil are prevented.

Example A specific embodiment of the present invention as described above will be described. The iron according to the present invention has iron powder particles as nuclei, and the iron powder particles are coated with a brass coating layer at a coverage of 92% or more. Powder molded and sintered,
In the case of a bearing material or the like, a solid lubricant is blended to enhance the lubrication performance.

The size of the iron powder particles as a raw material used as a main or core is not particularly limited, and is generally larger than about 100 mesh or less generally used for manufacturing a pure iron-based sintered body. It is possible to adopt a material having a particle size in the range described above. In other words, even relatively fine-grained ones can be increased in diameter by copper coating at the time of production and treated in the same manner as those in the conventional general range in terms of particle size. Therefore, even a powder having a large diameter exceeding the conventional particle size range can be formed to the same or more easily by a compacting process similar to the conventional method.

The amount of the iron powder particles is generally 40 to 79.5 wt%,
Preferably it is 40 to 70 wt%, more preferably 40 to 65 wt%.

The brass coating layer formed on the iron powder particles is 20.5-60 wt.
%, Preferably 25 to 50% by weight, more preferably 30 to 50% by weight.
~ 45 wt%.

In the actual production, compacting is performed using copper-coated iron powder particles, and sintering is performed together with the zinc oxide powder, that is, embedded in the zinc oxide powder as described above, or placed on the zinc oxide powder. It is advantageous to make the vaporized Zn vapor act on the coated copper layer and alloy it to brass.
The copper coating increases in weight by 0.5 to 5 wt% and becomes brass-like due to adsorption of Zn vapor.

The above-described copper coating on the iron powder particles is formed by plating or other known coating techniques. Typically, a state in which the iron powder particles are covered by the plating method is shown in a cross-sectional and microscopic view. In the drawing, the outer peripheral surface of the iron powder particle 1 is almost completely covered with the copper layer 2 in this case in which the iron powder particle 1 of 70 wt% is covered with copper 2 of approximately 30 wt%. . However, the thickness of the coated copper layer 2 is approximately proportional to the amount of copper (wt%) relative to the amount of iron powder, and is 20 wt%.
In the above-mentioned copper-coated one, at least 85% or more, generally 92% or more of the peripheral surface of the iron powder particles is appropriately prepared as being covered with the copper coating 2. After being compacted, it is sintered together with zinc oxide powder and adsorbs Zn vapor, so that the copper coating is preferentially brassed and increased in volume, resulting in a stable and dense brass coating layer. This results in a uniformly bonded sintered metal body. That is, there is substantially no exposure of the iron powder particles.

Naturally, graphite, molybdenum disulfide, boron nitride, etc. as solid lubricants are added as powder,
Solid lubricants such as graphite have a low specific gravity with respect to the copper-coated iron powder as described above, and even if such graphite is simply mixed, it is dispersed uniformly in other raw material powders. In addition, segregation occurs due to floating of graphite powder, deviation, and the like during transportation and loading, switching to a press hopper, and compacting. Therefore, experiments have confirmed that it is effective to use a relatively coarse powder of a solid lubricant such as graphite, and to use a powder obtained by classifying and removing the fine powder. That is, the commercially available graphite powder is generally 1 to 30 μm.
m, or graphite as a solid lubricant preferred by the present inventors is 10 to 150 μm, whereas 1 to 50 μm,
In particular, it is 20-100 μm, which is a coarse powder and cuts a fine powder of 10 μm or 20 μm or less, thereby facilitating uniform dispersion and preventing occurrence of segregation during cargo handling and other handling as much as possible. obtain. 10 as above
Fine powder having a particle size of less than μm or less than 20 μm does not generate dust in a classification treatment in a liquid, and can be appropriately classified.

The sintered metal of the present invention as described above may contain a small amount of nickel, tin, or the like.

The compacting is generally performed at about ² to 3 ton / cm ² , and its porosity is generally 8 to 35 vol.
0 vol% or more, preferably 22 vol% or more. By doing so, even if sintering and oil impregnation are performed after sintering, a state in which substantially the entire peripheral surface is covered is formed, and favorable porosity is obtained. Products. A green compact having a porosity exceeding 35 vol% has a high possibility of being damaged or broken during sintering.

When sintering is performed with the zinc oxide powder described above, 750 to 950
C., especially in a reducing atmosphere at 800-1000.degree. This temperature is considerably lower than the general sintering temperature when using iron powder,
In addition, the sintering process is simpler than the case of copper powder alone, and sintering is simplified. The sintering using the zinc oxide powder as described above is carried out under the condition that the compact is compacted and buried in the zinc powder accommodated in a container made of a material through which the atmospheric gas can pass.

A specific production example of the above-described device according to the present invention will be described below.

Production Example 1. Prepare copper-coated iron powder coated with copper to a coating rate of 99.5% by plating copper to 30 wt% with respect to iron powder particles equivalent to 70 wt%, and mold the powder to a molding density ratio of 70%. %, And then compacted as a bearing body with an outer diameter of 12 mm and an inner diameter of 6 mm, then housed in an atmosphere-permeable graphite bat containing zinc oxide dust, covered with a lid of the same quality, and The sintering process was performed in a reducing atmosphere using hydrogen gas at ℃.

The end face hardness of the sintered body was HRh58, 90 sintered at 800 ° C.
0 those sintered at ° C. is HRh72, its has a preferred conformability in relation to the sintering conditions, yet radial crushing strength those 800 ° C. Sintering of 19.1kg / mm ^2, 900 ℃ sintering 24
It was confirmed that the strength was extremely high when kg / mm ² and its compacting density and sintering conditions were considered.

Production Example 2. An iron powder in which a 22 wt% copper coating layer was formed to a coverage of 98.5% and an iron powder in which a 53 wt% copper coating layer was formed to a coverage of 99.8% were prepared. The added raw material powders were compacted at 65 vol% and 75 vol%, respectively, as the same bearings as in Production Example 1 and these compacts were oxidized in the graphite vat as in Production Example 1 described above. It was housed in zinc dust and covered. The sintering temperature of each of the four types, i, b, i, and b
Eight types of sintered metal bodies sintered at 800 ° C. and 900 ° C. were obtained, and the results of measuring the surface hardness and radial crushing strength of each of these sintered metal bodies are as shown in Table 1 below. It was confirmed that the bearing was a preferable bearing in consideration of its green compacting density and sintering conditions.

In addition, these eight types of sintered metal bodies have a temperature of 60 ° C and humidity
The results of a corrosion resistance test conducted under the conditions of 80% for 120 days are shown in Table 2 below, and it was confirmed that all of them had favorable corrosion resistance.

Further, the sintered metal of No. 1 to 8 as described above was impregnated with turbine oil, that is, the air in the pores was removed under a vacuum condition of about −30 mmHg, and the oil was immersed. The rise value was determined. In this case, as a comparative material, a pure iron-based bearing having a molding density ratio of 70 vol% was blended with a conventional 1% graphite, and the bearing was No. 9, and a 1% mixture of pure iron powder and brass powder was also used. Graphite blended and molding density ratio 70vol
%, The oil-impregnated No. 10 oil was similarly employed, and the results of the same tests are also shown in Table 3 below.

That is, it was confirmed that all of Nos. 1 to 8 according to the present invention have a preferable bearing function as compared with the comparative materials (Nos. 9 and 10). The bearing characteristic values are considerably inferior.

"Effects of the Invention" According to the present invention as described above, it is excellent in any of conformability, corrosion resistance and strength with respect to a mating member, and can be applied to a conventional bearing material having the same analytical component composition. The invention provides a product whose stability is greatly improved and provides a stable product, and a preferable and advantageous production method thereof, and is industrially effective.

[Brief description of the drawings]

The drawings show the technical contents of the present invention, and FIG. 1 and FIG. 2 are cross-sectional views showing an example of a copper-coated iron powder used in the present invention in a microscopic manner. However, in this drawing, 1 indicates iron powder particles, and 2 indicates copper coating.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-189361 (JP, A) JP-A-56-51554 (JP, A) JP-A-57-169094 (JP, A) 136944 (JP, A) JP-A-53-146203 (JP, A)

Claims (4)

(57) [Claims] (1) A brassic coating layer of 20.5 to 60 wt.
A sintered metal body obtained by compacting and sintering a powder having a porosity of 8 to 35 vol% in a state in which 92% or more of a peripheral surface of 9.5 wt% iron powder particles is coated. 2. A brassic coating layer of 19 to 59.7% by weight of 38 to 7
9.2 wt% of iron powder particles covered with at least 92% of the circumference of the powder should contain one or more solid lubricants such as graphite, molybdenum disulfide, boron nitride or lead. A sintered metal body characterized by being compacted and sintered with a porosity of 8 to 35 vol%. 3. Copper powder coated with a copper coating layer of 20 to 55% by weight and covering at least 92% of the peripheral surface of iron powder particles of 45 to 80% by weight is compacted. A method for producing a sintered metal body, comprising sintering together with a powder. 4. Copper-coated powder particles of 95 to 99.5 coated with a copper coating layer of 20 to 55% by weight and covering at least 92% of the peripheral surface of the iron powder particles of 45 to 80% by weight.
wt. parts of a solid lubricant such as graphite, molybdenum disulfide, boron nitride or lead are mixed in a ratio of 0.5 to 5 wt. parts, and the resulting compact is compacted into zinc oxide. A method for producing a sintered metal body, comprising sintering together with a powder.