JP2001146485A - Tray for firing powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tray not to be substantially reacted with a sintering auxiliary in producing various kinds of members made of metal by powder metallurgy. SOLUTION: This tray for firing powder comprises a Sin-CTC composite material which is composed of silicon carbide, a carbon fiber and a carbon component except the carbon fiber and has a structure constituted of a skeleton part and a matrix formed around the circumference of the skeleton part. At least 50% of the silicon carbide is β type, the skeleton part is composed of the carbon fiber and the carbon component except the carbon fiber, the silicon carbide may exist in a part of the skeleton part. The matrix is constituted of the silicon carbide, the matrix and the skeleton part are integrally formed and the composite material comprises a composite material having 0.5% to 5% porosity and a two-peak type average pore diameter distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tray for firing powder of a metal member, and more particularly to a tray used in a furnace for firing using a reducing gas called RX gas.

[0002]

2. Description of the Related Art A tray for firing powder of a metal member, in particular,
As a tray used in a furnace for firing using a reducing gas called RX gas, it is currently made of carbon, graphite, or ceramics because of its light weight and excellent heat resistance. Things are used. by the way,
Various firing aids are used depending on the characteristics of the metal material used, the shape of the member to be molded, and the like. It is known that, depending on the type of baking aid used, the baking aid reacts with the tray during baking to cause a so-called build-up phenomenon in which the tray surface is roughened or deposited on the tray surface. Since the surface accuracy / shape of the tray affects the accuracy of the fired parts, it cannot be used if the surface accuracy and build-up exceed a certain standard, and the surface must be polished or replaced with a new one. Is the current situation,
Therefore, the frequency of replacement is high, and the proportion of the cost of various members manufactured by this method cannot be ignored. Also, when the tray is transported by a robot or the like, it may be broken by impact or thermal shock during the baking process,
A tray excellent in impact resistance is desired.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a firing aid for manufacturing various metallic members by powder firing. And does not substantially react with
It is to provide a tray with a long life.

[0004]

Means for Solving the Problems The present inventors have conducted various studies in view of the above-mentioned current situation, and as a result, have been made of silicon carbide, carbon fiber, and a carbon component other than carbon fiber, and have a skeleton portion and a skeleton portion. A SiC—C / C composite composite material having a structure formed around and around
At least 50% of the silicon carbide is β-type, and the skeleton is formed of carbon fibers and carbon components other than carbon fibers.
Silicon carbide may be present in a part of the skeleton, the matrix is formed of silicon carbide, and the matrix and the skeleton are integrally formed,
In addition, the present invention has been found to achieve the above object by using a composite material having a porosity of 0.5% to 5% and a two-peaked average pore diameter distribution. It has been completed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A tray according to the present invention uses a raw material mainly composed of carbon fibers as its base material. As the carbon fiber used in the present invention, any carbon fiber can be used irrespective of its production method and raw materials. In manufacturing a tray, carbon fibers are first formed into a predetermined shape using a binder or the like. In this case, the following C / C composite is preferable from the viewpoint of durability.

[0006] In the present specification, a C / C composite is a powdery binder that acts as a matrix of a bundle of carbon fibers, and pitch and coke that become free carbon with respect to the bundle of carbon fibers after firing. And further, if necessary, by containing a phenol resin powder or the like, thereby preparing a carbon fiber bundle, forming a flexible film made of a plastic such as a thermoplastic resin around the carbon fiber bundle, To obtain a preformed yarn as a functional intermediate material. This preformed yarn is disclosed in
After forming a sheet or a woven fabric by the method described in JP-A-0639, laminating a required amount, and then molding by hot pressing, or a fired body obtained by firing this molded body, Say. That is, in the present invention, C /
The C composite is composed of carbon fiber and carbon other than carbon fiber, and the carbon fiber has a laminated structure composed of a specific number of carbonized fiber bundles. A composite material having a structure in which a matrix is formed and filled in a gap between the structure and the laminated structure, the composite material comprising a specific laminated structure and a matrix structure.

As a C / C composite used as a basic material, carbon fibers having a diameter of about 10 μm are usually bundled to form a fiber bundle (yarn) by bundling hundreds to tens of thousands of carbon fibers.
This fiber bundle is coated with a thermoplastic resin to obtain a flexible thread-like intermediate material, which is formed into a sheet by the method described in Japanese Patent Application Laid-Open No. 2-80639. Alternatively, a preformed body (fiber preform) having a predetermined shape is formed by arranging in a three-dimensional direction to form a unidirectional sheet (UD sheet) or various cloths, or by laminating the sheets or cloths. It is only necessary to use a material obtained by baking a film of a thermoplastic resin or the like made of an organic substance formed on the outer periphery of the fiber bundle of the preform and removing the film by carbonization. In this specification, the description of Japanese Patent Application Laid-Open No. 2-80639 is cited for reference. In the C / C composite used in the present invention, the carbon component other than the carbon fiber in the yarn is preferably a carbon powder, particularly preferably a graphitized carbon powder.

In the present invention, the SiC-based composite material, which is a raw material used in manufacturing the tray, is composed of silicon carbide, carbon fiber, and a carbon component other than carbon fiber, and is formed around the skeleton and the skeleton. A SiC-C / C composite composite material having a structure consisting of a matrix and a matrix, wherein at least 50% of the silicon carbide is β-type, and the skeleton is formed of carbon fibers and carbon components other than carbon fibers; Silicon carbide may be present in a part of the skeleton, the matrix is formed by silicon carbide,
The matrix and the skeleton are integrally formed, and the composite material is a composite material having a porosity of 0.5% to 5% and a distribution of an average pore diameter of a double peak.

Therefore, this SiC-based composite material uses, as a skeleton, a C / C composite in which each carbon fiber is composed of a carbon fiber bundle. Therefore, even if SiC is partially formed, Since each carbon fiber has a structure as a carbon fiber, which is maintained without being broken, the carbon fiber does not become short due to silicon carbide. Therefore, a machine having a C / C composite as a raw material is used. The main feature is that the mechanical strength is almost maintained or increases due to silicon carbide. Moreover, the yarn assembly has a composite structure in which a matrix made of a SiC-based material is formed between adjacent yarns. In addition,
This material can be manufactured by the method disclosed in Japanese Patent Application No. 11-31979 filed on Feb. 9, 1999. Therefore, the contents of Japanese Patent Application No. 11-31979 are cited here.

In the present invention, the SiC-based material refers to a material containing silicon carbide having a different degree of bonding with carbon. In producing the SiC-based composite material, the C / C composite is impregnated with metallic silicon. At this time, the metallic silicon remains on the carbon atoms constituting the carbon fibers and / or the surface of the carbon fibers in the composite. Since it reacts with free carbon atoms and is partially carbonized, partially carbonized silicon is produced between the outermost surface of the C / C composite and the yarns composed of carbon fibers, and thus the above-mentioned silicon is produced. A matrix made of silicon carbide is formed between the yarns.

In this matrix, a very small amount of silicon and carbon are bonded, but may contain several different phases from a silicon carbide phase to a pure silicon carbide crystal phase. However, this matrix contains only metallic silicon below the detection limit (0.3% by weight) by X-rays. That is, although this matrix is typically made of a silicon carbide phase, the silicon carbide phase may include a SiC-based phase in which the content of silicon is inclined. Therefore, SiC
The system material refers to a concentration of carbon of at least 0.01 mol% or more and 50 m or more in such an SiC-based phase.
It is a general term for materials contained within the range up to ol%. In order to control the carbon concentration to less than 0.01 mol%, it is necessary to strictly measure the amount of metallic silicon to be added in relation to the amount of free carbon in the C / C composite. It is not practical because the temperature control in the process becomes complicated. Therefore, theoretically, the carbon concentration is set to 0.001 mo.
It is possible to control to about 1%. It is to be noted that the remaining metallic silicon is required to be strictly controlled since powder metallurgy causes a reaction with the metal constituting the member to be molded, which affects the reliability of the member. The acceptable amount of metallic silicon is less than 0.1% as measured by EPMA. Thus, in order to strictly control the remaining metal silicon, it is important to control the temperature in the metal silicon impregnation step.

The Si-based composite material will be further described with reference to the drawings. The skeleton of this SiC-based composite material is basically the same as that shown in FIG. FIG. 2 is a sectional view when the SiC-based composite material according to the present invention is cut along the line IIa-IIa in FIG.
FIG. 2B is a cross-sectional view taken along line IIb-IIb in FIG. 1A. FIG. 3 is a partial cross-sectional view schematically showing the state of formation of the small projections. The skeleton of the SiC-based composite material 17 is constituted by the yarn aggregate 16, similarly to the skeleton of the Si—SiC-based composite material 7. The yarn aggregate 16 is the yarn array 1
1A, 11B, 11C, 11D, 11E, and 11F are vertically stacked. In each yarn array, the yarns 13 are two-dimensionally arranged, and the longitudinal directions of the yarns are substantially parallel. The longitudinal direction of each yarn in each vertically arranged yarn array is orthogonal. That is, the longitudinal direction of each yarn 12A of each of the yarn arrays 11A, 11C and 11E is parallel to each other, and is orthogonal to the longitudinal direction of each of the yarns 12B of each of the yarn arrays 11B, 11D and 11F. Each yarn is composed of a fiber bundle 13 composed of carbon fibers and carbon components other than carbon fibers. The yarn assembly 16 having a three-dimensional lattice shape is formed by stacking the yarn arrays. Each yarn is crushed during the pressing process as described below,
It is slightly elliptical.

Each yarn array 11A, 11C, 11E
In, the gap between adjacent yarns is filled with a matrix 18A, and each matrix 18A extends along and parallel to the surface of the yarn 12A. In each of the yarn arrangements 11B, 11D, 11F, the gap between adjacent yarns is filled with a matrix 18B, and each matrix 18B extends along the surface of the yarn 12B and parallel thereto. As shown in FIGS. 2A and 2B, the matrices 18A and 18B
Represents a silicon carbide phase 1 covering the surface of each yarn.
It consists of four. A part of the silicon carbide phase is
As shown in FIG. 3, it may project to the surface of the carbon fiber layer inside the composite member. Inside such small projections, pores (voids: 15) having a median diameter of about 100 μm are formed. It should be noted that most of the small projections 19 are made of C
/ C composites are formed along the traces of the matrix composed of carbon components other than carbon fibers. Therefore, by appropriately selecting the distance between yarns and / or the distance between yarn arrays and yarn arrays, the unit It is possible to adjust the density and size of the small projections 19 per area. As a tray, when observed and measured under an electron microscope, the size of the small projections was 10 μm at the maximum height.
m or less, and the density per 1 cm ² is preferably 9 or less. If it is out of this range, the surface shape of the tray is transferred to the fired component, which is not preferable as a tray for precise member firing. Adjacent yarn 12A
Silicon carbide phase 14 may also be formed between and 12B.

Each matrix 18A and 18B is elongated, preferably linear, along the surface of the yarn, respectively, and each matrix 18A and 18B is orthogonal to each other. Then, the yarn arrays 11A, 11
The matrix 18A in C and 11E and the matrix 18B in the yarn arrays 11B, 11D and 11F orthogonal thereto are continuous at the gap between the yarns 12A and 12B, respectively. As a result, matrix 1
8A and 18B form a three-dimensional lattice as a whole.

The setter is usually a flat plate. As the setter, the thickness, the size of the furnace, the size of the member to be molded, and the thickness capable of sufficiently maintaining the strength required when the inside and outside of the furnace are taken in and out, and the carrying, etc. The shape may be determined in consideration of the number of products manufactured for each lot. For example, in the case of a gear or the like as an automobile part, 400 mm × 300 mm × 7
mm is sufficient. That is, it may be appropriately selected according to the application. The shape is well known to those skilled in the art.

[0016]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist.

(Production Example) A powdery binder pitch which acts as a matrix of carbon fiber bundles and finally becomes free carbon for the carbon fiber bundles is aligned in one direction of the fibers. After being included in the carbon fiber, a carbon fiber bundle was prepared by further incorporating a phenol resin powder or the like. Around the carbon fiber bundle thus prepared,
A flexible film made of a plastic such as a thermoplastic resin was formed to obtain a preformed yarn as a flexible intermediate material. This preformed yarn has a size of 5 after firing.
A sheet is formed by a method described in Japanese Patent Application Laid-Open No. 2-80639 so that the required amount becomes 00 mm × 400 mm × 10 mm, and the necessary amount is laminated so that the directions of the carbon fibers are orthogonal to each other. , 10kg / c
The resin was cured at m ^2. Then in nitrogen at 2000 ° C
Then, a C / C composite having a size of 400 mm × 300 mm × 7 mm was obtained. The density of the obtained C / C composite is 1.6 g / cm ³ and the open porosity is 20%.
Met.

Next, the obtained C / C composite is
Purity 99. consisting of an amount sufficient to give a porosity of 3%.
It was erected in a carbon crucible filled with 8% metallic silicon powder having an average particle size of 1 mm. Next, the carbon crucible was moved into the firing furnace. After the temperature in the firing furnace was 1300 ° C., the flow rate of argon gas as an inert gas was 20 NL / min, the pressure in the firing furnace was 1 hPa, and the holding time was 4 hours, the pressure in the firing furnace was maintained as it was. By raising the temperature to 1600 ° C., the C / C composite is impregnated with metallic silicon to form a 3% porosity SiC—C / C.
A composite composite was produced. Also, the maximum height of the small projections of the obtained material is 8 μm,
In addition, the density per cm ² was 7 pieces. This was processed peripherally to produce a tray for firing metal powder.
When this was used as a powder firing tray in a furnace for firing metal powder, it was subjected to firing 100 times, but no build-up was observed. The service life was 5 times or more as compared with the conventional one.

[0019]

As is clear from the above test results,
The tray according to the present invention exerts an effect that it can be stably used for powder firing without substantially forming build-up for a long period of time even when used repeatedly.

[Brief description of the drawings]

FIG. 1 shows S used as a tray material according to the present invention.
It is a perspective view which shows typically the structure of the yarn assembly which forms the basic structure of an iC type composite material.

FIG. 2 (a) shows a SiC-based composite material IIa of FIG. 1;
FIG. 2B is a cross-sectional view taken along line IIa, and FIG.
It is sectional drawing at the time of cutting | disconnecting the same material along the IIb-IIb line of FIG.

FIG. 3 is a partial cross-sectional view schematically showing a formation state of a small projection.

[Explanation of symbols]

1A, 1B, 1C, 1D, 1E and 1F ... yarn arrangement, 2A ... yarn, 2B ... yarn, 3 ... fiber bundle (yarn), 4A ... silicon carbide phase, 4B ... silicon carbide phase, 4C ... silicon carbide phase, 5A ... Si-SiC material phase, 5B ... Si-
SiC-based material phase, 5C: Si-SiC-based material phase, 6: Yarn aggregate, 7: Fiber composite material, 8A: Matrix,
8B ... matrix, 11A, 11B, 11C, 11
D, 11E and 11F ... yarn arrangement, 12A ... yarn, 12B ... yarn, 13 ... fiber bundle (yarn), 14 ...
Silicon carbide phase, 15 ... voids, 16 ... yarn aggregate, 17 ...
Fiber composite material, 18A matrix, 18B matrix, 19 small projections.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA60 BA62 BA78 BA86 BB22 BB60 BB86 BC32 BC34 BC47 BC54 BD01 BD37 BE03 BE33 BE34 4K055 AA05 HA08 HA27

Claims (1)

[Claims] An SiC-C / C comprising silicon carbide, carbon fiber, and a carbon component other than carbon fiber, having a structure comprising a skeleton and a matrix formed around the skeleton.
A composite composite material, wherein at least 50% of silicon carbide is β-type, a skeleton is formed of carbon fibers and carbon components other than carbon fibers, and silicon carbide is present in a part of the skeleton. The matrix may be formed of silicon carbide, the matrix and the skeleton may be integrally formed, and the composite material may have a porosity of 0.5% to 5% and a double peak shape. A powder firing tray comprising a composite material having an average pore size distribution.