JPS5933656B2 - The best way to do this is to get the best results. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a silver-based composite material reinforced with silicon carbide continuous fibers.

In particular, the present invention provides a strong fiber made by tightly bonding continuous silicon carbide fibers with extremely excellent hardness, high-temperature mechanical strength, abrasion resistance, heat resistance, oxidation resistance, and corrosion resistance to a base material mainly made of silver. The present invention relates to a method for manufacturing a silver-based composite material reinforced with continuous silicon carbide fibers, which are aggregates of silicon carbide.

Silver has a density of 10.5g/cTn'5, and a melting point of 960'C.
Although it is a metal element, it has the highest thermal and electrical conductivity among metal elements, and has the second highest ductility and malleability after gold, making it excellent in processability. equipment materials, various switch materials, relay materials,
It is widely used as sliding material, bus bar material, etc.

It is also stable against water, oxygen, hydrochloric acid, alkali hydroxide, etc., so it is used in pipes and siphons for producing drinking water, cocks and valves for producing acetate fibers, and containers for strong alkalis. Furthermore, since it is the best conductor of heat, it is also used as a bearing alloy material for airplane engines and various cladding materials. Silver and silver alloys are used in a wide variety of ways, including as additives to coins, silverware, jewelry, dental materials, silver wax, photographic materials, silver plating, and alloys. However, among the above-mentioned uses, when silver is used as an electrical material, chemical equipment material, or structural material, hardness and mechanical strength are often required in addition to the above-mentioned properties of silver. , silver has a Brinell hardness of 2.5 and a tensile strength of 13-16 kg/m77l.
Since it is relatively small at 2, its range of use is quite limited. In particular, electrical materials are required to have excellent wear resistance and mechanical properties at high temperatures.
Not only silver alone, but also alloys of silver with tungsten, molybdenum, iron, nickel, copper, cadmium, etc., or cermet type or particle dispersion type of silver and carbon, cadmium oxide, lead oxide, tungsten carbide, molybdenum sulfide, etc. Conventionally, the development and manufacture of mixture composites of However, although the silver alloy has improved abrasion resistance, it has the disadvantage of being oxidized in air and a significant decrease in mechanical strength at high temperatures, and therefore its use is wide. Limited. Also, silver and carbon, cadmium oxide,
Mixture complexes with non-alloying materials such as lead oxide and tungsten carbide generally result in decreased electrical conductivity or
In addition to condensing and coarsening the non-alloying substances mentioned above at high temperatures and causing product deterioration due to chemical reactions with silver, systems containing cadmium and lead are difficult to handle in terms of safety management related to pollution problems. The use and manufacture of these silver mixture composites is severely limited. By improving the various drawbacks of conventional silver or silver-based materials as described above, we have developed a material that has high electrical conductivity, high thermal conductivity, high hardness, oxidation resistance,
By developing and manufacturing new materials with excellent high-temperature mechanical properties, these materials can withstand the high pressures, high temperatures, cryogenic temperatures, corrosive environments, and large currents that are particularly required in recent years.
There has been a desire for it to be widely used as an electrical material, structural material, or chemical equipment material that can withstand use under extreme conditions such as high voltage. As a new material with the above-mentioned high properties, fiber-reinforced silver matrix composite materials have long been considered promising, and in this fiber-reinforced composite method, the amount of base material is reduced compared to other types of composite materials. In addition to having the advantage of being able to maintain the properties and fiber properties almost independently,
In particular, it is possible to obtain a composite with excellent high-temperature mechanical properties, so it is expected that by finding an appropriate reinforcing fiber, it will be possible to produce a high-performance composite material.

This fiber-reinforced composite material has already been developed using alumina (A
Silver matrix composites reinforced with 12O3) whiskers or silicon carbide (SlC) whiskers have been investigated. However, composite materials using these whiskers are extremely expensive due to the complicated manufacturing process of the whiskers, and it is difficult to obtain whiskers of uniform quality. Not only can the entire composite be reinforced only piecemeal, but shear stress concentrates at the ends of the whiskers in the composite, resulting in a considerably low overall strength. The above-mentioned whisker-reinforced silver-based composite material has not yet become a substantial material because of various drawbacks such as the difficulty of mass-producing the composite due to the extremely complicated construction process. An object of the present invention is to provide a novel method for producing a silver-based composite material that eliminates the drawbacks of the above-mentioned composite materials.

In the present invention, the manufacturing method is simple, the price is relatively low, and by manufacturing a fiber-reinforced silver matrix composite using homogeneous long continuous SiC fibers, the above-mentioned other silver matrix composite materials have The object of the present invention is to provide a silver-based composite material having excellent properties that have improved various drawbacks.

In other words, the present invention combines the high thermal and electrical conductivity of silver with the high hardness of SiC fibers, as well as high-temperature mechanical strength with excellent abrasion resistance, heat resistance, oxidation resistance, and corrosion resistance. A method for obtaining a SiC continuous fiber reinforced Ag-based composite material is provided. Further, in the present invention,
SlC fibers have good wettability with Ag, and do not cause chemical reactions even when immersed in molten Ag, and their mechanical properties, oxidation resistance, and other properties decrease in the temperature range up to 960°C, which is the melting point of silver. are significantly less. Further, in the present invention, continuous fibers mainly made of silicon carbide obtained by firing spun fibers mainly made of an organic silicon compound are used as composite reinforcing fibers, but this SlC fiber is relatively simple and easy to use, as will be described in detail later. It can be produced at low cost and can be made homogeneous with arbitrary thickness and length, and its strength and elastic modulus are extremely superior compared to other conventionally known SlC continuous fibers. . Conventional SlC continuous fibers include: (1) W/B fibers with a tungsten core coated with boron, coated with SlC produced by vapor phase decomposition of organosilicon compounds and hydrogen or silicon chlorides and hydrocarbons; What you get.

(2) A tow made of about 10,000 rayon filaments is hydrated, then immersed in silicon chloride, and then thermally decomposed and carbonized.

(3) Continuous fibers made of a homogeneous mixture of SlC and S1 nitride by chemically treating a silazane-containing material made of halogenosilane and ammonia to make it spinnable, and heating the resulting spinning in an inert atmosphere. obtained as.
However, since the fiber (1) contains a W core, its diameter is as thick as 100 μm or more, its density is as large as 109/CTn3 or more, and it has poor flexibility, and its strength and elastic modulus also depend on that of the core's w. Therefore, the specific strength and specific modulus of S used in the present invention are quite small.
In addition to being significantly lower than that of 1C continuous fibers, the vapor phase decomposition method has the disadvantage that the process is complicated and the cost of the fibers is also high.

In addition, the manufacturing process for the fiber (2) involves the use of silicon tetrachloride and hydrochloric acid generated during the process, which not only complicates the process itself but also poses many problems in terms of safety management. Furthermore, since this manufacturing method starts from a bundle of rayon, it is extremely difficult to extract each fiber individually.Furthermore, the strength and elastic modulus of this fiber are lower than that of the SlC continuous fiber used in the present invention. Because of the small Z-Z, it is extremely disadvantageous to use the fiber (2) for composite reinforcement. Next, the continuous fiber (3) has a complicated manufacturing process until it is spun, so its manufacturing cost is high, and the tensile strength of this fiber is 60 to 115 kg/M7! L2, the elastic modulus is (9
~10)×103k9/TLT! L2, which is smaller than that of the fiber used in the present invention by Z to Z, so it is extremely disadvantageous to use this fiber for composite reinforcement. On the other hand, as will be described in detail later, the SiC continuous fiber used in the present invention has a simple manufacturing process and low manufacturing cost compared to the other fibers mentioned above, and is a homogeneous fiber having an arbitrary diameter and length. This fiber has the advantage of being able to be manufactured as a continuous fiber with extremely high strength and elastic modulus, making it ideal as a composite reinforcing fiber. , which is the most important feature of the present invention. Furthermore, the composite base material that can be used in the present invention includes not only Ag alone but also
As mentioned above, a silver alloy that uses a high melting point, hard metal such as Ag (5W.M0) to improve wear resistance, arc resistance and mechanical strength while maintaining high electrical conductivity as an alloy, Ag and 1-15 wt% carbon, 5-10 wt?Cul, 5-50 wt?NillO, Cdl below wt%
lO ~ 40 weight? A silver alloy that is made into an alloy using each of Fe, etc. or a composite thereof, and aims to improve low contact resistance, fusion resistance, toughness, and mechanical strength while maintaining high electrical conductivity, Ag-Cd, Ag-Mg, Ag-
Internal oxidation of alloys such as Pb to produce Ag-CdO, Ag-Mg
A particle-dispersed silver composite that maintains high electrical conductivity as a composite of O, Ag-PbO, etc., and has wear resistance, fusion resistance, and low contact resistance.A composite of Ag with WC and TlC. Silver-based cermet with the purpose of withstanding high voltage and high current, silver alloy for electrical contacts with the purpose of preventing surface staining as much as possible by alloying with Ag (5Au, Pd, Pt, etc.), carbon with Ag Silver alloys and silver composites in which other metals and compounds are added to silver are known, such as silver composites as sliding brush materials made of composites of MOS2 and MOS2. It is further advantageous to use SlC as a composite base material in the present invention, especially in terms of mechanical properties, abrasion resistance, etc., compared to composites using only silver as a base material. A fiber-reinforced Ag-based composite can be obtained.

Next, the method of the present invention will be explained in detail.

The reinforcing fibers used in the present invention are high-strength continuous fibers mainly made of silicon carbide obtained by firing spun fibers mainly made of organosilicon compounds, and the fibers are closely bonded with silver or an alloy or mixture mainly composed of silver. By bonding, a bonded high strength SlC-Ag composite material can be obtained. The silicon carbide continuous fiber described above has already been invented and patented by the present inventors, in Japanese Patent Application No. 50-50223.
Japanese Patent Application No. 50-52471, Japanese Patent Application No. 52472, Japanese Patent Application No. 58033, Japanese Patent Application No. 58034.
No., Patent Application No. 1983-70302, Patent Application No. 1983-7030
No. 3, Special Application No. 1983-JMo V219, Special Application No. 1979-799
It can be produced by the production method described in the specifications of No. 72 and Japanese Patent Application No. 50107371, using organosilicon compounds as shown in the following (1) to (5) as starting materials. It can be manufactured using

(1) A compound containing only Si-C bonds. (2) S
A compound that contains Si-H bonds in addition to i-C bonds. (3
) A compound having an S1-Hal bond.

(4) Compound having Sl-N bond. (5) Si-
A compound having an 0R (R-alkyl, aryl) bond.

(6) Compound having Sl-0H bond.

(7) Compounds containing Sl-Sl bonds.

(8) A compound containing an S1-0-Sl bond.

(9) Organosilicon esters. (3) Organosilicon peroxide.

Silicon and carbon are mainly produced by a polycondensation reaction using at least one of irradiation, heating, and addition of a polycondensation catalyst from at least one organosilicon low molecular weight compound belonging to the types (1) to σ0) above. An organosilicon polymer compound as a skeleton component, for example, a compound having the following molecular structure is produced.

(d) A substance containing the skeleton components described in (a) to (c) above as at least one partial structure of a chain or three-dimensional structure, or a mixture of (i), (C]), and (c).

If necessary, a small amount of an organometallic compound, a metal complex, and at least one organic polymer other than the above two types of compounds may be added to the organosilicon high molecular weight compound containing one or more of the above (a) to (d). Spun fibers of various lengths and uniform thickness can be obtained from a spinning dope mainly consisting of an organosilicon compound, which is a mixture formed by addition and mixing, or one or more compounds formed by addition and combination. .
After heating this spinning yarn at a low temperature in an oxidizing atmosphere in a temperature range of 50 to 400°C, it is heated in a vacuum with an inert gas excluding nitrogen (
Pre-calcined silicon carbide continuous fibers can be obtained by pre-calcining at a temperature range of 600 to 1000°C in an atmosphere of at least one selected from CO gas, hydrocarbon gas, organosilicon compound gas, and hydrogen gas. can. however,
Oxidizing gas, nitriding gas, carbonizing gas,
Even if one or more of the hydrogen gases is present at a partial pressure of 10 mmHg or less, there is no problem in carrying out the pre-firing. The pre-fired fibers can be further processed in vacuum, in air, oxygen gas, inert gas, CO gas, CO2 gas,
100% in an atmosphere of at least one selected from hydrocarbon gas, organosilicon compound gas, and hydrogen gas.
Silicon carbide continuous fibers can be obtained by heating in the temperature range of 0 to 2000°C. The properties are shown in Table 1.

The silicon carbide fiber obtained by firing the spun yarn mainly made of an organosilicon compound usually has a weight of 0.01 to 10% by weight. The above free carbon remains, and the remaining amount varies depending on conditions such as firing temperature, firing time, and firing atmosphere.

This free carbon reacts locally by diffusion or wetting of silver at a high temperature of 850° C. or higher, and forms a very small amount of solid solution or Ag2C2 at the interface between the SiC fiber and silver. Therefore, the bond between the SlC fiber and silver is not only the adhesion caused by mere wetting and mutual diffusion, but also the adhesion caused by the local chemical reaction caused by free carbon at the interface, making it even stronger. Free carbon is SiC-A of the present invention
It plays an extremely useful role in complexes aimed at g-bonds. Furthermore, as shown in Table 1, the SiC fiber of the present invention has a crystal grain size of several tens of lambda, so the number of microscopic irregularities on the fiber surface is extremely large per unit area. One of the great features of the present invention is that silver in a molten or softened state penetrates into the irregularities, thereby making the adhesion between the fibers and silver very strong through wetting and mutual diffusion. As described above, it has been discovered that the fibers and silver used in the present invention are intended to produce a high-strength silver-based composite material due to strong adhesion. As a method for combining SiC fibers with silver or an alloy or mixture mainly composed of silver, which can be used in the present invention, various methods normally used for manufacturing metal-fiber composite materials can be applied. Preferably, it is advantageous to use one of the following four methods.

(in vacuum or inert gas atmosphere) a. A method in which molten base metal is infiltrated into the gaps between aligned bundles of fibers.

mouth. A method of bonding an aggregate consisting of a base metal and fibers by sintering, hot pressing, etc. 〇C. A method of diffusion bonding by hot pressing or hot rolling a regular stack of base metal foils or thin plates and fibers.

two.

A method in which each fiber is coated with a base metal or sprayed with plasma, etc., and then hot pressed together. By using the above method, pores and voids are less likely to be created at the boundary between the fiber and the metal.
A homogeneous and strong composite material can be obtained.

Next, the S of the present invention! The content of SiC fibers in the C-Ag composite material is preferably from 5% to 70%** by weight.

If it is less than 5%, the effect of reinforcing fibers is substantially poor;
On the other hand, if it exceeds 90%, it is not preferable because it is not possible to maintain the property of being a good electrical and thermal conductor, which is a characteristic of silver or alloys and mixtures containing silver as a main component, and the workability of the product becomes extremely poor.

Next, examples of the present invention will be described.

Example 1 Vine composite materials having five different weight ratios as shown in Table 2 below were manufactured.

Only silver was used as the base metal, and the SlC fiber was 1400
A piece with a thickness of 10 to 201 t obtained by firing at ℃ and a length of 5
The pieces cut into 0mm pieces were made into a bundle and set in an alumina crucible (12φ x 50L1~). This crucible was suspended above a vacuum heating container evacuated to 1×, 10 −3 mnHg. An alumina tank containing molten silver was placed in the lower part of the container, and the tank was heated from the outside to bring the silver in the tank into a molten state at about 1000°C. Next, the crucible was lowered, immersed in the tank, held in O for 1 minute, and then pulled out.
The SiC-Ag composite material obtained in this way was
It was machined into a rod shape of x40L1Li to provide a test piece for measuring various properties. Table 2 shows the properties of these composite materials. In addition to having high hardness and strength, the decrease in thermal and electrical conductivity due to the decrease in silver content is relatively small, so this composite has excellent properties as an electrical material, chemical equipment material, and structural material. It is a composite body with a wide range of practical applications.

In addition, these composites were cut and examined using a microscope.
When the adhesion between the C fiber and silver was observed, no pores or voids were found at the interface between the two, but an extremely thin layered structure was observed on the fiber surface. This thin layer is caused by a local chemical reaction between the free carbon contained in the fibers and silver, producing a very small amount of Ag2C2, and this reaction product improves the adhesion between SiC and Ag. The mechanical properties of this composite are improved because the adhesion is further strengthened in addition to the adhesion caused by mere wetting and mutual diffusion. Example 2 A silver alloy consisting of 80% silver and 20% molybdenum was made into a powder of 325 mesh or more, and 14
10-20 μm thick (7) Si obtained by firing at 00°C
A prismatic powder compact of 10 x 10 x 40 mm3 in which bundles of C fibers (in units of 10 to 15 fibers) are buried in a unidirectional manner so as to be uniformly distributed, and the weight ratio of alloy and fibers is 30:70. was produced by applying a pressure of 300 kg/CWL using a mold press.

The fibers were set to be unidirectionally arranged in the length direction of the powder compact. This green compact was heated to 90'C in an Ar atmosphere of 1 atm.
Sintering was performed for 2 hours to obtain a composite. The density of this composite is 8.17, the average hardness is 7 (Mohs), the electrical resistance is 2.1 x 10-5 Ωα, and the thermal conductivity is 0.
15Ca1/CfrL. sec. It was deg. When this composite was tested as an electrical contact material, the contact resistance was almost the same as that of pure silver, and the fusion phenomenon and mass transfer due to arcing when large currents and voltages were applied were extremely small. The temperature rise and amount of wear at the contacts were also significantly lower, and the life of the contacts was approximately 30 to 50 times longer than that of contacts made of pure copper. That is, the silver-based composite produced by powder metallurgy as in this example is extremely useful as an electrical material such as an electrical contact material, a sliding material, and various switch materials. Also, the mechanical properties of the composite according to this example are determined by the fiber weight in Table 2. showed almost the same value as that of 30%. Furthermore, microscopic observation of this composite revealed that there were very few internal pores, voids, etc.
In addition to its application as the electrical material, this composite can also be used satisfactorily as a structural material or chemical equipment material. Example 3 Silver 80 weight? , Tsukeru 29 weight? A square foil of 30 x 30 mm with a thickness of 0.05 m of silver alloy made of
SIC fibers obtained by firing at 0°C with a thickness of 10 to 20 μm were cut into 301 m long pieces and arranged in one direction.
The SiC fiber content is 15% by weight. Total thickness of 2W! 1! A laminate was produced.

This laminate was heated at 3°C below the melting point of silver, 960°C, in an Ar atmosphere.
At a heating temperature of 930℃, which is 0℃ lower, the pressure is 200kg/CI
Hot pressing of L was carried out for 30 minutes to obtain a SiC-Ag alloy composite. The thickness of this material was reduced to about 1.511, the density was 9.09/CTrL3, and the average hardness was 6 Mohs. Moreover, the mechanical properties of this product were almost the same as those of the product with a fiber content of 20% in Table 2. According to the composite method of this example, it is possible to obtain a composite in the form of a thin plate, resulting in a SlC fiber-reinforced Ag-based composite material that can be bent and die-cut, and can be used as an electrical material,
Can be used as chemical equipment material and structural material. Example 4 SiC fibers obtained by firing at 1300°C with an average thickness of 20 μm
The pieces were cut to a length of 30 CTrL and arranged in a flat shape, and then plasma sprayed with silver.

When this spray was applied three times to each side of a flat fiber, the thickness of a single SiC+Ag fiber was 0.1 to 0.5J! I became I. After 10 sheets of these flat fibers were laid out in a graphite die, they were hot pressed in an Ar atmosphere for 1 hour at 930 C while applying a pressure of about 200 kg/Cd.
The proportion of SiC fibers in the obtained silver-based composite material is about 50% by weight? and its properties are as shown in Table 2, fiber weight 50
It was almost the same as that of %. Also, almost no pores were found in this composite. This composite material has the same various uses as those mentioned above. still,
In the above examples, we have shown some typical shapes that can be obtained as silicon carbide continuous fiber-reinforced silver-based composite materials and some examples of their composite methods, but various shapes can also be obtained by various methods other than these. Composite materials can be obtained.

Claims (1)

[Claims] 1. A continuous silicon carbide characterized by tightly bonding continuous fibers mainly made of silicon carbide obtained by firing a spun yarn mainly made of an organosilicon polymer compound and a base material mainly made of silver to form an aggregate. A method for producing a silver-based composite material reinforced with fibers.