JP2014129593A - Self-lubricating metal composite material and self-lubricating metal-based composite material each excellent in terms of strength, lubricity, and abrasion resistance and methods for manufacturing the self-lubricating metal composite material and self-lubricating metal-based composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-lubricating metal composite material and a self-lubricating metal-based composite material each having, while sustaining the strength of a metal matrix, a solid lubricant particle distribution suitable for improving the lubricating performance and abrasion resistance.SOLUTION: The provided metal composite material and metal-based composite material each comprise solid lubricant particles at a ratio of 1% to 10% with respect to the volume of a metal matrix. The metal composite material is manufactured by a mixed powder method using a centrifugal force in which a molten matrix is flowed into a mixed powder consisting of a matrix metal powder and solid lubricant particles, and the self-lubricating metal-based composite material of the present invention is manufactured by a mixed powder method using a centrifugal force in which a molten matrix is flowed into a mixed powder consisting of a matrix metal powder, hard particles, and solid lubricant particles.

Description

The present invention relates to a method for producing a composite material with a metal excellent in lubricity and wear resistance and used in a bearing or the like.

One of the components in a bearing is a bearing cage. Examples of the material used for the bearing cage include plastic and high-strength brass excellent in compatibility with bearing steel. Here, high-strength brass is a material in which Cu and Zn are the main components and about 1% Fe, Al, and Mn are added therein, and it has higher strength than brass with only Cu and Zn as components. It has a material.

Currently, high-strength brass bearing cages are manufactured by machining a centrifugal cast material. Here, centrifugal casting is a technology that can produce a casting material free of casting defects such as a nest by applying centrifugal force to a mold having a shape such as a cylinder and pouring molten metal into the mold. It is. Bearing cages made of this high-strength brass have been applied to fields that require excellent wear characteristics. In particular, high-strength brass used as a material for bearing cages is required to have higher wear resistance than existing materials because of the difficulty of replacement in bearings for wind power generators.

One means for improving the wear resistance and lubricity of a metal material or metal matrix composite material is a method of compounding a solid lubricant such as graphite or molybdenum disulfide. Here, the metal material refers to a metal material that does not include hard particles, and the metal matrix composite refers to a material that includes hard particles in a metal base material. Solid lubricant particles such as graphite and molybdenum disulfide have high lubricity because they have a hexagonal layered crystal structure. Therefore, by combining these solid lubricant particles with a metal base material, the friction coefficient is reduced in the frictional wear between the metal material and the dissimilar material as the counterpart material, thereby improving the wear resistance of the metal material. It is possible to make it.

Examples of means for producing a self-lubricating metal composite material in which a solid lubricant is compounded in such a metal base material include the sintering methods disclosed in Patent Document 1 and Patent Document 2. The self-lubricating metal composite material proposed in Patent Document 1 contains 20% to 40% Ni, 0.1% to 0.9% P, 1% to 8% C, and 5% by mass. It is a graphite-dispersed Cu-based sintered alloy having a porosity of ˜25%. Furthermore, the invention of Patent Document 2 is a self-lubricating sintered body containing 0.01% to 40% solid lubricant particles in mass% in a metal base material. However, this sintering method has a drawback that it is difficult to manufacture a large member. Furthermore, it has the disadvantage of low strength due to the presence of vacancies inside the material.

  One of the methods for compositing fine solid phase particles in a metal base material is a centrifugal force mixed powder method disclosed in Patent Document 3. In this technique, first, a mixed powder 1 is prepared by mixing solid phase particles to be combined with a base metal powder (see FIG. 1). Then, after the mixed powder 1 is put into the cylindrical mold 2, a centrifugal force is applied to the mixed powder 1 by rotating the cylindrical mold 2, and the mother melted in the melting furnace through the runner 3. The molten metal 4 is poured (see FIG. 2). After solidification, the fine solid phase particles are firmly fixed to the base metal, and a cast material in which the fine solid phase particles are uniformly or obliquely dispersed in the base metal can be obtained (see FIG. 3). Since the size of the product according to the present technology depends on the size of the mold, a large member can be easily manufactured. In addition, since the vacancies inside the material can be reduced, application of this technique can be expected to solve the above problems.

  However, the strength of many solid lubricating particles such as graphite is often lower than that of a metal material. Therefore, it is conceivable that the material strength decreases when a large amount of solid lubricant particles are compounded in a metal base material as in Patent Document 2. Therefore, it is necessary to find an appropriate distribution of solid lubricant particles in a metal material that improves the lubrication characteristics and wear resistance without reducing the strength of the metal matrix, but has not yet been found.

  On the other hand, Non-Patent Document 1 proposes a method of changing the distribution of hard particles as a method of improving the wear resistance of the metal matrix composite material. However, this method can improve strength and wear resistance, but it is difficult to improve lubrication characteristics such as a coefficient of friction. Therefore, a metal matrix composite material is also required to have a material design that achieves both strength, wear resistance and lubrication characteristics.

JP 2002-180162 A JP-A-11-241129 JP2008-284589

H. Sato, E .; Miura-Fujiwara and Y.M. Watanabe: Japan Journal of Applied Physics, Vol. 51 (2012) 01AK01 (6 pages)

  In view of the above points, an object of the present invention is to provide a self-lubricating metal composite material and a self-lubricating material having a solid lubricant particle distribution suitable for improving lubrication characteristics and wear resistance while maintaining the strength of the metal base material. It is to provide a metal matrix composite.

The present inventors have found that the above problem can be solved by compounding solid lubricant particles into a metal such as Cu or a metal base matrix at an appropriate volume ratio by a centrifugal force mixing powder method and combining them. It was. That is, according to the present invention, there are provided the following self-lubricating metal composite material and self-lubricating metal-based composite material, and methods for producing these metal composite material and metal-based composite material.

[1] A metal composite material and a metal matrix composite material in which the solid lubricant particles with respect to the metal base material are 1 vol% to 10 vol% in volume ratio.

[2] The metal composite material and metal matrix composite material according to [1], wherein the metal base material is Cu or a Cu alloy, and the solid lubricant particles are graphite.

[3] The metal matrix composite material according to [1] or [2], wherein the metal matrix composite material includes hard particles.

[4] The metal composite material and metal matrix composite material according to any one of [1] to [3], wherein the solid lubricant particles are more inclined and dispersed near the sliding surface.

[5] A base metal powder and a solid lubricant are mixed to prepare a mixed powder, and after the mixed powder is put into a mold, the mold is rotated and a centrifugal force is applied to the mixed powder. Production of a metal composite material in which a solid lubricant is dispersed in a metal base material, in which a base metal molten metal melted in a melting furnace for casting is poured, and the base metal powder is melted and solidified by heat of the base metal molten metal. Method.

[6] A method for producing a metal matrix composite material, wherein the mixed powder according to [5] further contains hard particles.

It is the figure which drawn typically the method of throwing the mixed powder of the base metal metal powder and solid phase particle powder in the rotating cylindrical mold in the centrifugal powder mixing method. It is the figure which drawn typically the method of pouring the base metal molten metal in the rotating cylindrical shape metal mold | die in the centrifugal force mixed powder method. It is the figure which drew typically the cylindrical composite material produced with the centrifugal force mixed powder method. FIG. 3 is a diagram schematically illustrating a self-lubricating metal composite material in which more solid lubricant particles are inclined and dispersed in the vicinity of a sliding surface. FIG. 3 is a diagram schematically illustrating a self-lubricating metal-based composite material in which more solid lubricant particles are inclined and dispersed in the vicinity of a sliding surface. It is the figure which drawn typically the vacuum centrifugal casting apparatus used when producing a rod-shaped composite material with centrifugal force. In 1st Example of this invention, it is a secondary electron image of the scanning electron microscope of the cross section of Cu composite material comprised by Cu and a graphite particle manufactured by the centrifugal force mixed powder method. In 1st Example of this invention, it is a reflection electron composition image of the scanning electron microscope of the cross section of Cu composite material comprised by Cu and a graphite particle manufactured by the centrifugal force mixed powder method. In 1st Example of this invention, it is the graph which showed the change of the friction coefficient in the friction wear test of Cu composite material and the pure Cu casting material which are comprised by Cu and a graphite particle manufactured by the centrifugal force mixed powder method. In 1st Example of this invention, it is the optical microscope picture which showed the abrasion trace surface after the friction abrasion test of Cu composite material and the pure Cu casting material which consist of Cu and a graphite particle manufactured by the centrifugal force mixed powder method . In 1st Example of this invention, it is a graph which shows the relationship between the average friction coefficient of Cu composite material, and the base material volume ratio of a graphite particle. In 1st Example of this invention, it is a graph which shows the relationship between the wear trace cross-sectional area of Cu composite material which arose by friction abrasion, and the base material volume ratio of a graphite particle. In 2nd Example of this invention, it is the figure which drawn typically the structure | tissue of the Cu group composite material produced with the centrifugal force mixed powder method. In the second embodiment of the present invention, a cross-sectional microstructure in a Cu-based composite material in which SiC particles having a base material volume ratio of 15% and graphite particles having a base material volume ratio of 2% are combined in a pure Cu base material is shown. It is an electron micrograph. In 2nd Example of this invention, it is a graph which shows the relationship between the average friction coefficient of Cu base composite material, and the base material volume ratio of a graphite particle. In 2nd Example of this invention, it is a graph which shows the relationship between the volume of the Cu base composite material lost by friction abrasion, and the base material volume ratio of a graphite particle. The second embodiment of the present invention shows the relationship between the 0.2% proof stress of the Cu-based composite material using SiC particles having an average particle diameter of 150 μm and the base material volume ratio of the graphite particles.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

In the metal composite material and the metal matrix composite material of the present invention, the solid lubricating particles with respect to the metal base material are preferably 1% to 15% by volume, more preferably 1% to 10% by volume. The metal base material is preferably Cu or a Cu alloy. The solid lubricating particles are preferably graphite or molybdenum disulfide, and more preferably graphite. The metal matrix composite material includes hard particles in addition to the metal base material and solid lubricant particles, and the hard particles are preferably SiC, TiC, CBN, AlN, diamond, etc., but SiC is particularly preferable. The average particle diameter of SiC is preferably 50 μm or less. The volume ratio of SiC to the base metal is preferably 1 to 30%. In the metal composite material and the metal matrix composite material of the present invention, it is preferable that the solid lubricant particles are more inclined and dispersed near the sliding surface (see FIGS. 4 and 5). The metal composite material of the present invention is preferably produced by a mixed powder method using centrifugal force by pouring a molten metal into a mixed powder composed of a base metal powder and solid lubricating particles. In addition, the metal matrix composite material of the present invention is preferably produced by a mixed powder method using centrifugal force by pouring a molten metal into a mixed powder composed of a base metal powder, hard particles and solid lubricant particles.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Example 1: Preparation and evaluation of self-lubricating metal composite material)
A Cu composite material in which graphite particles are combined in a pure Cu base material is manufactured. A mixed powder is prepared by adding 25% to 55% of graphite powder having an average particle diameter of 50 microns (μm) to the pure Cu powder as the base metal powder in a volume ratio (graphite powder / pure Cu powder). The powder was put into a casting mold 10 of a vacuum centrifugal casting apparatus shown in FIG. In addition, 120 g of pure Cu ingot which is the base metal 11 is loaded into the crucible of the vacuum centrifugal casting apparatus, and the pure Cu ingot is heated to a melting temperature of 1150 ° C. to 1190 ° C. in a vacuum to thereby melt the base material molten pure Cu. It was. Then, the casting mold and the base material molten pure Cu are rotated and a centrifugal force of gravity multiple 32G (gravity multiple 1G corresponds to the gravitational field) is applied, so that the base material molten pure Cu is applied to the casting mold 10. Poured. By this manufacturing process, a Cu composite material in which the graphite particles 14 are inclined and dispersed in the centrifugal force direction was obtained. As a result, graphite particles are dispersed in a volume ratio of 0% to 24% and compounded at the tip in the centrifugal force direction of the Cu composite material. A mixed powder composed of 7.58 g of pure Cu powder and 1.03 g of graphite powder having an average particle diameter of 50 μm was prepared (volume ratio of graphite powder to pure Cu powder was 54%), and 120 g of pure Cu ingot was added to the mixed powder. When the molten pure Cu is poured by applying a centrifugal force of gravity multiple of 32G (gravity multiple of 1G corresponds to the gravitational field) by heating to ° C, the graphite particles are dispersed in the pure Cu matrix. A structured Cu composite material was obtained. FIG. 7 is a secondary electron image of a cross-sectional scanning electron microscope in the Cu composite material (volume ratio of graphite particles to pure Cu base material is 24%). Graphite particles are composited with a pure Cu base phase. You can see how it is. FIG. 8 is a reflection electron composition image of a scanning electron microscope in a cross section of a Cu-based cast material, and it can be seen from this photograph that graphite particles are combined with a pure Cu matrix. From the above results, it can be seen that the present technology can produce a Cu composite material in which graphite particles are dispersed in a pure Cu matrix.

The Cu composite material and a pure Cu cast material obtained by melting a pure Cu ingot using the same vacuum centrifugal casting apparatus were subjected to a friction wear test using a ball-on-disk type friction wear tester. The mating material used in the friction and wear test was spherical bearing steel (JIS: SUJ2), and the load was 800 g. FIG. 9 is a graph showing changes in the coefficient of friction during the friction and wear test. The friction coefficient of the Cu composite material is smaller than that of the pure Cu casting material. Furthermore, it was also found that the sound generated during the frictional wear test of the Cu composite material was smaller than that of the pure Cu cast material. FIG. 10 is an optical micrograph showing the structures of the wear scar surface of the Cu composite material and the wear scar surface of the pure Cu cast material. From this, it was also found that the wear scar width of the Cu composite material is smaller than the wear scar width of the pure Cu cast material, and that the wear resistance is improved by combining with the graphite particles.

Next, the relationship of the volume ratio of the graphite particles to the pure Cu base material was examined with respect to the average friction coefficient. The result is shown in FIG. By adding the graphite particles, the average friction coefficient of the Cu composite material is lowered. Furthermore, when the volume ratio of the graphite particles to the Cu base material exceeds 15%, the average friction coefficient does not change. FIG. 12 is a graph showing the relationship between the cross-sectional area of wear marks generated in the Cu composite material by frictional wear and the volume ratio of the graphite particles to the Cu base material. In this graph, an increase in the cross-sectional area of the wear scar means a decrease in wear resistance. The wear resistance of the Cu composite material is improved by adding graphite particles, but does not change when the volume ratio of the graphite particles to the Cu base material exceeds 15%. Since graphite has a lower strength than pure Cu, in this example, the volume ratio of the graphite particles to the Cu base material suitable for achieving both strength, lubricating properties and wear resistance is 1% to 15%. 1% to 10% is more preferable.

(Example 2: Production and evaluation of self-lubricating metal matrix composite)
A Cu-based composite material in which SiC particles as hard particles and graphite particles as solid lubricant particles were combined in a pure Cu base material was produced by a centrifugal mixed powder method. A pure Cu powder, which is a base metal powder, is a graphite powder having an average particle diameter of 50 μm in a volume ratio of 5% to 20%, and two types of SiC powders having an average particle diameter of 150 μm and 40 μm in the same volume ratio. % Mixed powder was prepared, and the mixed powder was put into a casting mold 10 of a vacuum centrifugal casting apparatus shown in FIG. In addition, 100 g of pure Cu ingot which is the base metal 11 is loaded into the crucible of the vacuum centrifugal casting apparatus, and then the pure Cu ingot is heated at a melting temperature of 1250 ° C. to 1300 ° C. in a vacuum to melt the base material. Pure Cu was used. Then, the casting mold 10 and the base material molten pure Cu are rotated and a centrifugal force having a gravity multiple of 35 G is applied to flow the base material molten pure Cu into the casting mold 10, as shown in the schematic diagram of FIG. 13. Thus, a Cu-based composite material in which graphite particles 14 and SiC particles 16 were inclined and dispersed in the direction of centrifugal force was obtained. When SiC particles having an average particle diameter of 150 μm are used, SiC particles having a base material volume ratio of 15% to 19% and graphite particles having a base material volume ratio of 1% to 5% are combined in a pure Cu base material. A Cu-based composite material was obtained. On the other hand, when produced using SiC particles having an average particle size of 40 μm, SiC particles having a volume ratio of 6% to 10% and graphite particles having a volume ratio of 1% to 3% in a pure Cu matrix. A Cu-based composite material having a composite was obtained. FIG. 14 shows a scanning electron microscope of a cross-sectional structure of a Cu-based composite material in which SiC particles (average particle diameter 150 μm) and 2% graphite particles are combined in a pure Cu base material in a volume ratio of 15%. It is a reflection electron composition image. Thus, both SiC particles and graphite particles are combined in the Cu base material by the centrifugal force mixed powder method.

The Cu-based composite material was subjected to a frictional wear test in the same manner as in Example 1 using a ball-on-disk frictional wear tester. The counterpart material used in the frictional wear test was spherical bearing steel (JIS: SUJ2), and the load was 800 g. FIG. 15 is a graph showing the relationship between the average friction coefficient of the Cu-based composite material and the base material volume ratio of the graphite particles. When SiC particles having an average particle diameter of 150 μm are used, the average friction coefficient of the Cu-based composite material does not decrease until the addition of graphite particles exceeds 1% of the base material volume ratio. This is because the average particle size of SiC particles is larger than the average particle size of graphite particles. On the other hand, in the Cu-based composite material using SiC particles having an average particle diameter of 40 μm smaller than the graphite particles, the average friction coefficient of the Cu-based composite material was reduced by adding the graphite particles. Further, in the Cu-based composite material using SiC particles having an average particle diameter of 40 μm, the average friction coefficient does not change when the base material volume ratio of the graphite particles exceeds 1%. FIG. 16 is a graph showing the relationship between the volume of the Cu-based composite material lost due to frictional wear and the base material volume ratio of graphite particles. An increase in volume lost due to frictional wear means poor wear resistance. From this graph, until the volume ratio of the graphite particles reaches 1%, the wear resistance of the Cu-based composite material is improved as the volume ratio of the graphite particles increases. However, the wear resistance of the Cu-based composite material is saturated when the base material volume ratio of the graphite particles exceeds 1%. FIG. 17 shows the relationship between the 0.2% proof stress of the Cu-based composite material using SiC particles having an average particle diameter of 150 μm and the base material volume ratio of the graphite particles. The 0.2% yield strength of the Cu-based composite material decreases with an increase in the volume fraction of the graphite particles, but decreases more significantly when the base material volume ratio of the graphite particles exceeds 2%. Therefore, in the present Cu-based composite material, the base material volume ratio of the graphite particles is preferably 1% to 3% and more preferably 1% to 2% in order to achieve both strength, wear resistance, and lubrication characteristics.

INDUSTRIAL APPLICABILITY The present invention can be used for a machine part having a sliding part such as a bearing, a metal bond grindstone having high durability and capable of processing with a low thrust force.

Claims (6)

A metal composite material and a metal matrix composite material, wherein the solid lubricant particles relative to the metal base material are 1 vol% to 10 vol% in volume ratio. The metal composite material and the metal matrix composite material according to claim 1, wherein the metal base material is Cu or a Cu alloy, and the solid lubricant particles are graphite. The metal matrix composite material according to claim 1, wherein the metal matrix composite material includes hard particles. The metal composite material and the metal matrix composite material according to any one of claims 1 to 3, wherein the solid lubricant particles are more inclined and dispersed near the sliding surface. A base metal powder and a solid lubricant are mixed to prepare a mixed powder. After the mixed powder is put into a mold, the mold is rotated and centrifugal force is applied to the mixed powder to dissolve for casting. A method for producing a metal composite material in which a solid lubricant is dispersed in a metal base material, in which a base metal molten metal melted in a furnace is poured, and the base metal powder is melted and solidified by heat of the base metal melt. The method for producing a metal matrix composite material, wherein the mixed powder according to claim 5 further contains hard particles.