JP2011137186A - Method for manufacturing metal-ceramics composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal-ceramics composite material, with which filling uniformity of ceramics particles and filling rate thereof can be improved. <P>SOLUTION: In the method for manufacturing the metal-ceramics composite material which is obtains by impregnating the metal as the basic material into a preform with the ceramics particles as reinforcing materials, the method for forming the preform includes: a step of obtaining a non-fluid mixture in a stationary state by mixing the ceramics particles with a binder with water as a dispersion medium; a step of charging the mixture into a mold and vibrating it to develop fluidity, settling the ceramics particles in the mixture, and obtaining a molding including the ceramics particles, the water and a binder component; a step of freeze-hardening the molding together with the die, and then, removing the freeze-hardened molding from the die and obtaining the hardened body; and a step of firing the hardened body in the air atmosphere and obtaining the preform composed of the ceramics particles and pores. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a metal-ceramic composite material using a metal as a base material and ceramics as a reinforcing material.

Metal-ceramic composites reinforced with ceramics combine the properties of both metals and ceramics. For example, excellent properties of ceramics such as light weight, high elastic modulus, low thermal expansion, and wear resistance, and conductivity It has excellent metal properties such as high toughness and high thermal conductivity. Thus, since it has the characteristics of both ceramics and metal, it has been attracting attention as a next-generation material from the industry such as machine equipment manufacturers and is being put to practical use.

Since the characteristics of the metal-ceramic composite material can be designed within a certain range depending on the composition ratio of the base material and the reinforcing material, it is necessary to increase the composition ratio of the ceramic material in order to utilize the ceramic characteristics more. In order to increase the powder filling rate of the reinforcing material, an impregnation method is proposed in which a preform composed of ceramic fibers or particles as a reinforcing material is prepared in advance, and the metal as a base material is impregnated into the preform. Has been.

For example, Patent Document 1 describes a sedimentation molding method using water as a dispersion medium, and the powder filling rate of the preform is improved to 73% by adjusting the kind of ceramic powder and the ratio of coarse particles to fine particles. There has been proposed a method for producing a metal-ceramic composite material having the required strength and fracture toughness value by adjusting the type and amount of the binder to an optimum combination.

Patent Document 2 describes a hot press method, in which phenol resin (10% by mass) is added to a powder containing silicon carbide # 180 and # 800 in a ratio of 60:40 as a reinforcing material. A method of producing a molded body having a silicon carbide content of 70% by volume by dry-mixing, press-molding while being put into a mold and heated is disclosed.

Japanese Patent No. 4217278 JP 2008-50181 A

However, when the preform is produced by the above-described sedimentation molding method, the ceramic particle filling rate of the reinforcing material can be 70% or more, but when the raw material slurry is poured into the mold during the molding process, the coarse particles and fine particles of the ceramic particles are formed. It was easy to separate, and the grain size composition of the coarse and fine particles sometimes changed between the lower part and the upper part of the molded body. In such a case, there is a problem that the upper part containing a lot of fine particles has to be removed, and not only the raw material is wasted but also the disposal cost is high.

In addition, the filling rate is likely to be inclined in the height direction from the lower part to the upper part. For example, it may occur in a thick product having a height exceeding 50 mm. When metal is impregnated with such a heterogeneous preform with different filling rates at the upper and lower parts, the resulting metal-ceramic composite material also has a difference in thermal expansion coefficient between the upper and lower parts, causing warping and cracking. There was a problem.

On the other hand, although there is no separation of the ceramic particles due to the difference in sedimentation speed in the case of the hot press method, since it is a uniaxial press, for example, in a thick product exceeding 50 mm, the pressure distribution in the mold becomes large and the center of the compact is filled. The rate tended to be low. In addition, an expensive press machine with high-pressure specifications is required to obtain a large molded body, only a simple structure can be formed because of press molding, and a processing cost is high to add a complicated structure, etc. There was also a cost issue.

This invention is made | formed in view of such a subject, The objective is to provide the manufacturing method of the metal-ceramics composite material which can improve the uniformity and filling rate of ceramic particle filling. .

In order to solve the above problems, the present invention
In a method for producing a metal-ceramic composite material obtained by impregnating a preform of ceramic particles as a reinforcing material with a base metal,
The preform forming method comprises:
Mixing ceramic particles with a binder using water as a dispersion medium to obtain a non-flowable mixture in a stationary state;
Adding the mixture to a mold and applying vibrations to develop fluidity to precipitate ceramic particles in the mixture to obtain a molded body containing ceramic particles, water and a binder component;
A step of freeze-curing the molded body together with the mold and then demolding to obtain a cured body;
Firing the cured body in an air atmosphere to obtain a preform comprising ceramic particles, a binder, and pores;
The manufacturing method of the metal-ceramics composite material characterized by including this.

In addition, the ceramic particles of the preform include a combination of two particles of coarse particles and fine particles, and the ratio D (coarse particles / fine particles) of the average particle diameter of the coarse particles to the fine particles is 6 to 20— A method for producing a ceramic composite material is provided.

Furthermore, the manufacturing method of the metal-ceramics composite material whose ceramics / water volume ratio V of the said mixture is 1.0-2.0 is provided.

In addition, the present invention further provides a method for producing a metal-ceramic composite material in which the preform has a ceramic filling ratio of 74 to 84% by volume.

According to the present invention, since a non-flowable mixture is used in the molding of a preform in a stationary state, separation of coarse and fine particles can be suppressed, and the uniformity and filling rate of ceramic particles can be increased. it can. Therefore, waste of raw materials can be reduced and manufacturing costs such as disposal costs can be suppressed. Moreover, since the uniformity of the ceramic particle filling can be improved, the problem of warpage and cracking of the metal-ceramic composite material obtained by impregnating the preform with metal can be solved.

In addition, as described above, the non-fluid mixture is used in a stationary state, and the fluidity is expressed by applying vibration. Therefore, the uniformity and filling rate of the ceramic particles can be improved.

Further, in addition to the above, by using a combination of coarse particles and fine particles having a predetermined average particle size as ceramic particles, a metal-ceramic composite material having an increased filling rate and excellent properties such as strength can be obtained. Obtainable.

Hereinafter, the present invention will be described in more detail.

As ceramic particles of the reinforcing material, alumina (Al ₂ O ₃ ), aluminum borate (9Al ₂ O ₃ .2B ₂ O ₃ ), oxides such as silica and mullite, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride Nitrides such as silicon carbide (SiC), boron carbide (B ₄ C), carbides such as titanium carbide and boron carbide, borides such as zirconium boride and titanium boride, and the like can be used. Of these, silicon carbide, boron carbide, alumina, and aluminum borate are preferable. Silicon carbide has characteristics such as low cost, light weight, high rigidity, low coefficient of thermal expansion, and high thermal conductivity, and has high added value as a machine part, so it is suitable as a reinforcing material for metal-ceramic composite materials. Can be used. Boron carbide is lighter and more rigid than silicon carbide, and has excellent impact resistance and neutron absorption, and should be used as a reinforcing material for metal-ceramic composite materials that require these characteristics. Can do. Alumina is suitable as a general-purpose member because it is inexpensive, has high plasma resistance, and has high strength. Aluminum borate is extremely excellent in wear resistance, and a metal-ceramic composite material using this as a reinforcing material can be used for a sliding member or the like.

Of the ceramics described above, silicon carbide that is usually used as an abrasive or a raw material for a refractory can be used. If it is an abrasive | polishing material, a thing with the particle size of # 1000 or more of a specification can be used. The type of silicon carbide may be any type such as green or black. Alumina may also be used as a raw material for abrasives and refractories like silicon carbide, and any kind of alumina such as fused alumina, sintered alumina, calcined alumina, etc. can be used. Of these, fused alumina is preferable because of its high filling rate.

The ceramic particles used in the present invention are preferably those having an average particle size in the range of 10 to 300 μm. By using a combination of coarse particles and fine particles within this range, the filling rate of the ceramic particles can be improved.

The ceramic particles and water are mixed with a binder as a dispersion medium.

As the binder, an inorganic binder, a water-soluble thermosetting resin, or the like can be used. As the inorganic binder, for example, colloidal silica, alumina sol, water glass, lithium silicate, or the like can be used. As the water-soluble thermosetting resin, for example, a phenol resin, an epoxy resin, an acrylic resin, or the like can be used. The amount of binder added is preferably adjusted to 0.3 to 10.0% by volume in terms of solid content with respect to the ceramic particles. If the added amount of the binder is too small, the strength of the preform is small and a problem occurs when the composite is formed. If the amount is too large, closed pores are generated in the preform and the characteristics of the metal-ceramic composite material are lowered.

A mixture obtained by mixing ceramic particles, water and a binder has non-flowability in a stationary state. By using non-fluidity, separation of coarse particles and fine particles can be suppressed, and the uniformity and filling rate of the ceramic particles can be increased. Therefore, waste of raw materials can be reduced and manufacturing costs such as disposal costs can be suppressed. Moreover, since the uniformity of the ceramic particle filling can be improved, the problem of warpage and cracking of the metal-ceramic composite material obtained by impregnating the preform with metal can be solved. Here, the stationary state means a state left without giving vibration, and the non-fluidity means that the fluidity is high enough to hold the shape after being put into the mold without being self-leveling in the stationary state. Say nothing.

In the present invention, in addition to making the mixture non-flowable as described above, the ceramic particles include a combination of two sizes of coarse particles and fine particles, and further, a ratio D (coarse particles / fine particles) of these average particle sizes. ) Was set to 6-20.

Usually, when the fluidity of the mixture is lowered, it becomes difficult to fill the ceramic particles, so the filling rate cannot be increased. However, in the present invention, the two particle sizes are combined, and the ratio of the average particle sizes is adjusted to a predetermined range. Thus, the filling rate is improved. In the case of 6> D, the filling rate is not much different from that in the case of single particles, and the effect of combining two particle sizes cannot be obtained, and in the case of 20 <D, the separation of ceramic particles cannot be suppressed even in the method of the present invention, so It is not preferable because it becomes a preform. In addition, although this invention contains the combination of 2 particle sizes about ceramic particle | grains, as long as the effect of this invention is acquired, it does not matter as 3 particle sizes or more. In that case, the third and subsequent particle sizes are preferably smaller than the coarse particles and the fine particles.

The ceramic / water volume ratio V of the mixture is preferably 1.0 to 2.0. Separation of coarse and fine particles mainly occurs in the step of feeding the mixture from the mixer into the mold and the step of sedimentation molding by adding vibration to the mixture charged in the mold. In the present invention, the particle size blending and the water content are adjusted to predetermined values so that a non-flowable mixture can be obtained in a stationary state, so that the separation at the time of charging the mixture and the settling distance at the time of sedimentation molding are reduced. In combination with the above particle size blending, a high filling rate can be realized. Specifically, for example, the filling rate of ceramic particles can be improved to 74 to 84% by volume. From the above viewpoint, the volume ratio is more preferably 1.3 to 1.7, and further preferably 1.4 to 1.6.

The mixture obtained as described above is put into a mold. At this time, since the mixture is non-flowable in a stationary state and is difficult to separate, a stable and homogeneous preform can be obtained.

After the mixture is put into a mold, it is molded by vibration. By applying vibration, the mixture can be fluidized and the ceramic particles can be highly filled. The solvent water reduces the friction between the particles that impede the filling of the ceramic particles, and the vibration serves to promote a high filling. As a method of applying vibration, it is sufficient to place a mold on a vibration table and apply vibration. The vibration strength may be such that a vibration of about 10 to 30 m / s ² is transmitted to the entire formed body formed by sedimentation and filling of ceramic particles. The material of the mold used for molding may be metal such as aluminum or iron, plastic, rubber or the like, but rubber is particularly preferable in view of ease of demolding.

In the present invention, since the separation of the ceramic particles is suppressed, a portion containing a large amount of fine particles is not formed on the upper portion of the formed body, so that the removal of the upper portion can be reduced. Therefore, the removal amount of the upper part may be determined in consideration of leveling accuracy during vibration of the mixture, and can be suppressed to 5% or less with respect to the thickness of the molded body, for example.

Next, the molded body is freeze-cured together with the mold. Since the molded body contains water, it can be cured by freezing. The reason why the molded body is frozen together with the mold is to maintain the shape when the mold is removed. When the freezing is gradually performed, the binder component dispersed in the water is concentrated and segregation occurs. Therefore, it is necessary to perform the freezing rapidly, and it is preferably performed at a temperature of −25 ° C. or lower. The water contained in the molded body is the remaining water from which the supernatant formed on the upper part of the molded body has been removed after molding.

The cured product obtained by demolding is fired in an air atmosphere. Firing is preferably adjusted to a temperature condition at which the binder is sufficiently solidified.

Next, the obtained preform is impregnated with metal by pressure impregnation or non-pressure impregnation to obtain a metal-ceramic composite material.

The pressure impregnation is a method for forcibly impregnating pores of the preform with aluminum or the like melted by pressurization. It is preferable to use aluminum or an aluminum alloy as the metal that penetrates the preform. Specifically, for example, pure aluminum having a purity of 99.0% or more, a metal casting, AC3A used for sand casting, AC12A used for die casting, ADC12 for die casting, and the like can be used.

The pressure during impregnation is preferably 5 to 100 MPa, and more preferably 10 to 80 MPa. If the pressure is lower than this, aluminum or an aluminum alloy does not sufficiently permeate into the pores of the preform, and there is a risk that sufficient properties such as Young's modulus may not be obtained. Since the preform obtained by the present invention has a high filling rate and excellent strength, a large pressure can be applied. Accordingly, fine pores can be impregnated, and a denser and higher strength metal-ceramic composite material can be obtained. The melting temperature of aluminum or aluminum alloy may be any temperature as long as it is not lower than the melting point and sufficiently penetrates. Specifically, a melting temperature of 650 to 800 ° C. can be employed.

When non-pressure impregnation is used, in addition to aluminum or an aluminum alloy, Si, an Si—Al alloy containing 0 to 40% by volume of Al, or the like can be impregnated. When impregnating with aluminum or an aluminum alloy, a metal-ceramic composite material is obtained by impregnating the preform with an Al—Si—Mg based or Al—Mg based aluminum alloy at a temperature of 700 to 1000 ° C. in a nitrogen stream. be able to. When impregnating Si or an Al-Si alloy containing 0 to 40% by volume of Al, after melting the binder by carbonizing a preform using an organic binder in a vacuum or non-oxidizing atmosphere, the melting point A method in which Si that has been heated and melted at the above temperature or Si-Al alloy containing 0 to 40% by volume of Al is brought into contact with the preform can be employed.

Hereinafter, the present invention will be described in more detail with specific test examples of the present invention.

[blend]
With respect to commercially available ceramic particles having a predetermined ratio of coarse particles and fine particles, a predetermined amount of ceramic / water volume ratio is obtained together with 10% by mass of binder colloidal silica liquid (solid content: 2.0% by mass, solvent: water). Ion exchange water was added and mixed to obtain a mixture. In the present invention, the median diameter (D50) determined by laser diffraction particle size distribution measurement is used as the average particle diameter.

[Molding]
The mixture was put into a rubber mold and vibrations (acceleration 30 m / s ² ) were applied to settle the ceramic particles to obtain a molded body (width 100 × depth 100 × thickness 100 mm).

[Freeze curing]
The molded body was freeze-cured together with the mold at −30 ° C. and then demolded to obtain a cured body.

[Baking]
The cured body was heated to 1100 ° C. at a rate of 1 ° C./min in the air atmosphere, held for 3 hours, and then cooled to room temperature at a rate of 1 ° C./min to obtain a preform.

[Evaluation]
The bulk density of the preform was measured by the Archimedes method, and the filling rate of the ceramic particles was determined. In addition, the measurement was performed by collecting five samples in the thickness direction of the preform, and the average filling rate was calculated. Furthermore, the percentage of the value obtained by dividing the difference between the maximum and minimum filling rates by the average was calculated as the slope of the filling rate. The results are shown in Table 1. In the column of “Coarse Grain” and “Fine Grain” in Table 1, the average particle diameter of each is shown, and “Coarse / Fine” indicates coarse / fine grain.

Test No. In 2-6, 9-12, 15-19, and 22-25, the non-flowable mixture was obtained in the stationary state. By visual observation, a layer containing a large amount of fine particles was not observed on the upper part of the compact. These preforms had a filling rate of 74 to 84% by volume and an inclination of 2.5% or less, and a highly filled and extremely small filling inclination was obtained.

On the other hand, test no. The mixture of Nos. 8 and 21 had fluidity in a stationary state, and a layer containing a lot of fine particles was visually observed at the upper part of the obtained molded body. These preforms had a low filling rate and a large slope. In addition, Test No. Although the mixture of Nos. 13 and 26 did not exhibit fluidity in a stationary state, the ceramic / water volume ratio V was too high, so that it did not flow even under vibration and the filling rate was low. Test No. Nos. 1 and 14 have a small average particle diameter ratio D, so the filling rate does not increase. Nos. 7 and 20 were too high in inclination because the ratio D of the average particle diameters was too large to prevent the separation of fine particles.

Claims (4)

In a method for producing a metal-ceramic composite material obtained by impregnating a preform of ceramic particles as a reinforcing material with a base metal,
The preform forming method comprises:
Mixing ceramic particles with a binder using water as a dispersion medium to obtain a non-flowable mixture in a stationary state;
Adding the mixture to a mold and applying vibrations to develop fluidity to precipitate ceramic particles in the mixture to obtain a molded body containing ceramic particles, water and a binder component;
A step of freeze-curing the molded body together with the mold and then demolding to obtain a cured body;
Firing the cured body in an air atmosphere to obtain a preform comprising ceramic particles, a binder, and pores;
A method for producing a metal-ceramic composite material comprising The ceramic particles of the preform include a combination of two particle sizes of coarse particles and fine particles, and the ratio D (coarse particles / fine particles) of the average particle diameter of the coarse particles to the fine particles is 6 to 20. Method for producing metal-ceramic composite material The method for producing a metal-ceramic composite material according to claim 1 or 2, wherein the mixture has a ceramic / water volume ratio V of 1.0 to 2.0. The method for producing a metal-ceramic composite material according to claim 1, wherein the preform has a ceramic filling ratio of 74 to 84% by volume.