JP2017105707A - Porous body, porous bonded body, filtration filter for molten metals, jig for firing, and method for producing porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous body that is excellent in thermal shock resistance and high temperature strength, and a porous bonded body, a filtration filter for molten metals, a jig for firing, and a method for producing a porous body.SOLUTION: A porous body according to one embodiment of the present invention contains silicon carbide aggregates having an average particle diameter of 800 μm or more and 4 mm or less, and a silicon carbide binder which binds the aggregates. In the porous body, an average pore diameter is 200 μm or more, a porosity is 30 vol.% or more, and the content of metal silicon and boron is 1 mass% or less.SELECTED DRAWING: Figure 1B

Description

  Embodiments disclosed herein relate to a porous body, a porous joined body, a filter for molten metal, a firing jig, and a method for producing a porous body.

  Conventionally, a filtration filter which is an example of a porous body made of silicon carbide for removing particles contained in a high-temperature gas such as exhaust gas is known (see, for example, Patent Documents 1 and 2).

  However, the above filter cannot be used as a molten metal filter for removing inclusions contained in a molten metal in which a metal such as an aluminum alloy is dissolved. Moreover, the above filtration filter has room for improvement in terms of thermal shock resistance and high temperature strength.

  Conventionally, a firing jig made of silicon carbide for firing a ceramic member such as sanitary ware is known (see, for example, Patent Document 3).

JP 60-255671 A Japanese Patent Laid-Open No. 2-180612 Japanese Patent Laid-Open No. 62-021762

  In recent years, kiln tools for firing electronic components have become mainstream with rapid firing as electronic components become smaller, so firing made of silicon carbide with good thermal conductivity that can cope with further rapid heating and rapid cooling during firing. A jig is used. However, since the porosity of the firing jig made of silicon carbide cannot increase the porosity, uniform binder removal processing cannot be performed in the firing process of the electronic component, which causes a problem in quality control. Further, such a firing jig has room for improvement in durability in terms of thermal shock resistance and high temperature strength.

  One aspect of the embodiments has been made in view of the above, and is a porous body, a porous joined body, a molten metal filter filter, a firing jig, and a porous body that are excellent in thermal shock resistance and high-temperature strength. It aims at providing the manufacturing method of.

  The porous body according to one aspect of the embodiment includes a silicon carbide aggregate having an average particle diameter of 800 μm or more and 4 mm or less, and a silicon carbide binder that bonds the aggregate. The porous body has an average pore diameter of 200 μm or more, a porosity of 30% by volume or more, and a content of metal silicon and boron of 1% by mass or less.

  According to one embodiment of the present invention, it is possible to provide a porous body excellent in thermal shock resistance and high-temperature strength, a porous joined body, a filter for molten metal, a firing jig, and a method for producing a porous body. .

Drawing 1A is an explanatory view explaining an outline of a manufacturing method of a porous body concerning an embodiment. Drawing 1B is an explanatory view explaining an outline of a manufacturing method of a porous body concerning an embodiment. Drawing 2A is an explanatory view explaining an outline of a filtration filter for molten metal concerning an embodiment. 2B is a cross-sectional view taken along the line A-A ′ of FIG. 2A. FIG. 3 is a flowchart illustrating an example of a method for manufacturing a porous body according to the embodiment. FIG. 4 is a flowchart illustrating a first modification of the method for manufacturing a porous body according to the embodiment. Drawing 5 is an explanatory view explaining an outline of a manufacturing method of a porous body concerning an embodiment. FIG. 6 is a flowchart showing a second modification of the method for manufacturing a porous body according to the embodiment. FIG. 7 is an explanatory diagram for explaining the outline of the method for producing a porous body according to the embodiment. FIG. 8A is an explanatory diagram illustrating an outline of a firing jig according to the embodiment. FIG. 8B is a B-B ′ cross-sectional view of FIG. 8A. FIG. 9 is a cross-sectional view for explaining the outline of the porous joined body according to the embodiment. FIG. 10A is a perspective view illustrating an outline of a porous joined body according to an embodiment. FIG. 10B is a top view of FIG. 10A. 10C is a cross-sectional view taken along the line C-C ′ of FIG. 10B.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a porous body, a porous joined body, a molten metal filter filter, a firing jig, and a porous body manufacturing method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  Drawing 1A and Drawing 1B are explanatory views explaining an outline of a manufacturing method of a porous body concerning an embodiment. The manufacturing method of the porous body which concerns on embodiment includes each process of granulation, shaping | molding, drying, and baking.

  First, a granulation process is demonstrated using FIG. 1A. A granulation process is a process of preparing a granulation body from the mixture of the raw material for manufacturing the porous body which concerns on embodiment. Specifically, the binder particles 3 including the first binder particles 1 and the second binder particles 2 are sprayed with a solution obtained by dissolving a binder in a liquid medium (liquid medium) at high speed. The granulated body 4 is prepared by stirring the mixture. The granulated body 4 is granulated in a state where the first binder particles 1 and the second binder particles 2 are uniformly dispersed.

  Here, silicon carbide can be applied to both the first binder particles 1 and the second binder particles 2 constituting the binder particles 3. Moreover, the average particle diameter of the 1st binder particle | grains 1 becomes like this. Preferably they are 0.2 micrometer or more and 250 micrometers or less, More preferably, they are 1 micrometer or more and 100 micrometers or less.

  The average particle diameter of the second binder particles 2 can be larger than the average particle diameter of the first binder particles 1. Specifically, the average particle diameter of the second binder particles 2 is preferably 0.4 μm or more and 500 μm or less, and more preferably 2 μm or more and 200 μm or less. Thus, by defining the average particle diameter of the first binder particles 1 and the second binder particles 2, the size of the granulated body 4 described later can be controlled appropriately. Here, the “average particle diameter” refers to a median diameter (d50) obtained based on a volume-based particle size distribution converted to a sphere equivalent diameter in a laser diffraction particle size distribution measuring apparatus (wet method).

  Moreover, the compounding ratio of the 1st binder particle | grains 1 and the 2nd binder particle | grains 2 in the granulated body 4 can be 10: 90-90: 10 in conversion of mass, for example. Thus, the granulated body 4 can be made suitable for actual use by prescribing the blending ratio of the first binder particles 1 and the second binder particles 2.

  In addition, a liquid medium having a relatively high volatility is applied to the liquid medium constituting the solution sprayed on the binder particles 3 stirred by the high speed mixer / granulator. Specific examples include water, methanol, ethanol, isopropyl alcohol, acetone, and ethyl acetate, but are not limited thereto. In addition, as the binder to be dissolved in the liquid medium, one or more kinds depending on the type of the liquid medium are applied. Specific examples include, but are not limited to, organic binders such as polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and acrylic resins.

  Moreover, the average particle diameter of the granulated body 4 is preferably 10 μm or more and 500 μm or less, and more preferably 15 μm or more and 300 μm or less. Thus, by defining the average particle diameter of the granulated body 4, the thermal shock resistance and high temperature strength of the porous body according to the embodiment can be improved.

  In the above-described embodiment, the binding material particle 3 is described as including both the first binding material particle 1 and the second binding material particle 2. However, the first binding material particle 1 and the second binding material are described. Only one of the particles 2 may be used.

  Next, each process of shaping | molding, drying, and baking is demonstrated in order using FIG. 1B. First, the molding process will be described. The molding step is a step of producing the molded body 6 by putting the aggregate particles 5 together with the above-described granulated body 4 into a mold and pressurizing and compressing. Specifically, when the granulated body 4 and the aggregate particles 5 are mixed so as to have a predetermined ratio, and then an appropriate amount of a polysaccharide binder such as dextrin and glucose and water are added and kneaded, aggregate particles are obtained. The granule 4 surrounds the periphery of 5 and is dispersed. And after putting the mixture (kneaded material) containing the granulated body 4 and the aggregate particle 5 into a type | mold (not shown) and applying a predetermined pressure and press-molding, as shown in the middle stage of FIG. 1B A molded body 6 including voids 7 corresponding to the size and bulk specific gravity of the aggregate particles 5 is obtained.

  Here, as the aggregate particles 5, for example, silicon carbide having an average pore diameter of 200 μm or more can be applied. Preferably, the purity of silicon carbide can be 95% or more, but is not limited thereto. Moreover, the average particle diameter of the aggregate particles 5 is preferably 200 μm or more and 5 mm or less, more preferably 300 μm or more and 4 mm or less. By defining the average particle diameter of the aggregate particles 5 in this way, the average pore diameter and porosity can be made suitable for actual use as a porous body.

  Moreover, the compounding ratio of the aggregate particle 5 and the granulated body 4 in the molded body 6 can be, for example, 95: 5 to 70:30 in terms of mass. Thus, by defining the blending ratio of the aggregate particles 5 and the granulated body 4, the average pore diameter and the porosity can be made suitable for actual use as a porous body.

  Next, the drying process will be described. A drying process is a process of drying the molded object 6 obtained by the above-mentioned shaping | molding process. Water is removed from the molded body 6 by this drying step. In addition, you may abbreviate | omit this drying process depending on the shape and moisture content of the molded object 6. FIG.

  Finally, the firing process will be described. A baking process is a process of baking the molded object 6 from which the water | moisture content was removed in the above-mentioned drying process with the baking apparatus which is not shown in figure. In this step, the molded body 6 is embedded in a mixed powder of carbon powder and silica powder, and the embedded molded body 6 is heated and fired to produce a fired body 11 shown in the lower part of FIG. 1B. Specifically, the fired body 11 is recrystallized silicon carbide (RSiC). Such a fired body 11 is a porous body (hereinafter also referred to as “porous body 11”) subjected to end processing or the like as necessary, such as a metal melt filter or a firing jig described later. Used for applications.

  In the molded body 6, a neck 10 that joins the aggregate particles 5 is formed by the diffusion of silicon carbide contained in the granulated body 4 when firing. In FIG. 1B, for ease of understanding, the binding material 9 and the neck 10 are shown as separate bodies. However, they may be integrated so as not to be identified by SEM observation.

  Moreover, in this embodiment, since the molded object 6 was embedded in carbon powder and the carbon source was added, evaporation of the silicon carbide powder at the time of sintering can be accelerated | stimulated. Moreover, in this embodiment, the growth of the neck 10 can be promoted by embedding the molded body 6 in carbon powder and silica powder and firing it.

  Furthermore, since the three kinds of particles of the first binder particle 1, the second binder particle 2 and the aggregate particle 5 are present in the above-described ratio and size, firing proceeds appropriately. The firing of each particle containing silicon carbide and the formation of the neck 10 can be promoted.

  Here, the molded body 6 is fired at a firing temperature in a firing apparatus of, for example, 2000 ° C. or higher, preferably 2000 ° C. to 2500 ° C. Thereby, the molded object 6 can be baked appropriately. At this time, for example, it is preferable that the firing is performed in an inert gas atmosphere such as argon or nitrogen.

  Thus, according to the method for manufacturing the porous body 11 according to the embodiment, the aggregate body 8 includes the aggregate 8 corresponding to the size of the aggregate particle 5, includes the pores 12 corresponding to the void 7, and is granulated. The porous body 11 in which the binder 9 and the neck 10 according to the composition and size of 4 are formed is obtained. By appropriately forming the neck 10, the porous body 11 having excellent thermal shock resistance and high temperature strength as compared with the average pore diameter and porosity can be obtained.

  Next, the porous body 11 according to the embodiment will be described. The porous body 11 includes a silicon carbide aggregate 8 having an average particle diameter of 200 μm or more. Here, the average particle diameter of the aggregate 8 is specifically, for example, a SEM (Scanning Electron Microscope) image of a cross section of the porous body 11 is taken, and the particle diameter of the aggregate 8 is obtained from the SEM image by an intercept method. To determine the particle size distribution.

  As a specific particle diameter measurement procedure, an arbitrary line is drawn on the SEM image, and the major axis and minor axis of the aggregate 8 intersecting with the line are measured. Next, the particle shape is an ellipse, and the average value of the major axis and the minor axis is the particle diameter of the aggregate 8. Then, a plurality of SEM images of different fields of view are also imaged, the above measurement is repeated using the captured plurality of SEM images, and the particle diameters of 500 or more aggregates 8 are measured, and then statistically processed. Thus, the average particle diameter of the aggregate 8 in the cross-sectional structure of the porous body 11 is obtained.

  The porous body 11 includes a silicon carbide binder 9 that bonds the aggregate 8. Here, from the SEM image of the cross section of the porous body 11 described above, the difference can be confirmed that the binder 9 is a tissue different from the aggregate 8.

  The porous body 11 has an average pore diameter of 200 μm or more, preferably 300 μm or more and 2000 μm or less. If the average pore diameter of the porous body 11 is less than 200 μm, it is not suitable for use as, for example, a metal melt filtration filter described later, and may become clogged. Further, if the average pore diameter of the porous body 11 is less than 200 μm, it is not suitable for use as a firing jig described later, for example, and the object placed on the firing jig by causing temperature unevenness in the furnace. The fired product may not be fired efficiently, or the binder removal may not be performed efficiently, resulting in firing failure. Here, the “average pore diameter” means that in a mercury porosimeter, pressure is applied to intrude mercury into the fine pores of the powder using the large surface tension of mercury, and the pressure and the amount of mercury inserted It refers to the median diameter (d50) obtained based on the pore diameter distribution obtained when the pores 12 are approximated to a cylinder.

  Further, the porous body 11 has a porosity of 30% by volume or more, and preferably 40% by volume or more and 70% by volume or less. If the porosity is less than 30% by volume, it is not suitable for actual use as the porous body 11. Here, the “porosity” is obtained by calculating the density based on the size and mass of the sample using the porous body 11 or a part of the porous body 11 and calculating the ratio to the theoretical density of silicon carbide. Say.

  Moreover, the bulk specific gravity of the porous body 11 is preferably 1.5 or more and 2.3 or less, and more preferably 1.6 or more and 2.0 or less. By setting the bulk specific gravity within the above-described range, the average pore diameter and the porosity are likely to fall within an appropriate range suitable for the application, and are suitable for actual use as the porous body 11. Here, “bulk specific gravity” refers to a value calculated based on the size and mass of a test piece obtained by processing the porous body 11 or a part of the porous body 11.

  In addition, the porous body 11 preferably has a metal silicon and boron content of 1% by mass or less, more preferably 0.5% by mass or less. By making content of metal silicon and boron into the above-mentioned range, the fall of the high temperature bending strength mentioned later can be suppressed. Moreover, when utilizing this porous body 11 as a filtration filter for molten metal mentioned later, the leakage of the impurity to the molten metal after filtration can be further prevented. Here, the contents of metallic silicon and boron refer to values obtained by fluorescent X-ray analysis.

  Further, the porous body 11 preferably has a silicon carbide content of 95% by mass or more, more preferably 99% or more. By making content of silicon carbide into the above-mentioned range, the fall of the high temperature bending strength mentioned later can be suppressed. Moreover, when utilizing this porous body 11 as a filtration filter for molten metal mentioned later, the leakage of the impurity to the molten metal after filtration can be further prevented. Here, “content of silicon carbide” refers to a value obtained based on the results of X-ray fluorescence analysis, TC (total carbon) analysis, and FC (free carbon) analysis. There is no problem even if the content of silicon carbide is 99.999% or more, but it is not preferable because the purity of silicon carbide in each raw material to be used needs to be increased and the cost is increased.

  The thermal conductivity of the porous body 11 is practically preferably 10 W / (m · K) or more and 80 W / (m · K) or less, more preferably 15 W / (m · K) or more and 50 W / ( m · K) or less, and more preferably 18 W / (m · K) or more and 40 W / (m · K) or less. When the thermal conductivity is in the above-described range, when the porous body 11 is used as, for example, a metal melt filtration filter to be described later, it is possible to suppress a temperature drop of the metal melt before and after passing the molten metal. Further, when such a porous body 11 is used as, for example, a firing jig described later, temperature unevenness in the kiln can be reduced and firing can be performed efficiently. Here, the “thermal conductivity” refers to a value obtained based on the thermal conductivity measurement by the heat flow method defined in JIS R2616: 1995.

  Below, the specific application example of the porous body 11 is demonstrated using FIG. 2A and FIG. 2B. FIG. 2A is an explanatory view for explaining the outline of a filter for molten metal that is an example of the porous body 11 according to the embodiment, and FIG.

  As shown in FIGS. 2A and 2B, the molten metal filter 110 according to the embodiment is formed as a cylindrical member configured to have an outer peripheral surface 113 and an inner peripheral surface 114. Inclusions in the molten metal are collected while the molten metal flows from the outer peripheral surface 113 toward the inner peripheral surface 114. Then, the cleaned molten metal is discharged from the hollow portion surrounded by the inner peripheral surface 114 to the outside.

  The molten metal filtration filter 110 according to the embodiment includes an aggregate 8 of silicon carbide having an average particle diameter of preferably 600 μm or more, more preferably 800 μm or more and 4 mm or less. In order for the aggregate 8 to have the above-described average particle diameter, for example, the average particle diameter of the aggregate particles 5 is preferably 600 μm or more, more preferably 800 μm or more and 4 mm or less.

  In addition, the bending strength of the molten metal filtration filter 110 is preferably 2 MPa or more and 15 MPa or less, more preferably 3 MPa or more and 14 MPa or less. Here, “bending strength” refers to a value measured at room temperature (5-35 ° C.) based on a three-point bending test specified in JIS R1601: 2008. More specifically, a three-point bending test was performed at a span length of 30 mm and evaluated using a sample obtained by processing the molten metal filter 110 into a cuboid of 20 mm × 10 mm × 50 mm.

  Further, the high-temperature bending strength at 1500 ° C. or less of the molten metal filtration filter 110 is preferably 2 MPa or more and 15 MPa or less, and more preferably 3 MPa or more and 14 MPa or less. By setting the high-temperature bending strength in the above-described range, it can be used as the molten metal filter filter 110 even under relatively high temperature conditions exceeding 1500 ° C., for example. Here, “high-temperature bending strength at 1500 ° C. or lower” means a value measured at a high temperature (1000 to 1500 ° C.) based on a three-point bending test specified in JIS R1604: 2008. More specifically, a three-point bending test was carried out at a span length of 90 mm in an air atmosphere at 1500 ° C. using a sample obtained by processing a filter for metal melt 110 into a 20 mm × 10 mm × 120 mm rectangular parallelepiped. It is a thing.

  Further, the thickness t1 of the molten metal filter 110 is preferably 15 mm or more and 100 mm or less, more preferably 20 mm or more and 60 mm or less. If the thickness t1 is less than 15 mm, for example, deformation is likely to occur, and the service life may be shortened. Furthermore, when the thickness t1 is less than 15 mm, the filtration function cannot be sufficiently exhibited, and inclusions to be filtered reach the inner peripheral surface 114 without being captured, and are discharged into the hollow portion together with the molten metal. is there. Moreover, when thickness t1 exceeds 100 mm, the physique of the filtration apparatus (not shown) containing the filter 110 for metal melts will become large, for example, and may not be suitable for actual use.

  Next, another application example of the porous body 11 according to the embodiment will be described with reference to FIGS. 8A and 8B. FIG. 8A is an explanatory diagram for explaining an outline of a firing jig as an example of the porous body 11 according to the embodiment, and FIG. 8B is a cross-sectional view taken along the line B-B ′ of FIG. 8A.

  As shown in FIGS. 8A and 8B, the firing jig 210 according to the embodiment includes a flat plate-like firing shelf 213 having an upper surface 211 and a lower surface 212 and having a substantially rectangular shape when viewed from above. The firing jig 210 is supported by a plurality of columns (not shown) so that the upper surface 211 of the firing shelf 213 is substantially horizontal. And the to-be-fired bodies 50 and 52 are mounted on the upper surface 211 of the baking shelf 213.

  The firing jig 210 including such a firing shelf 213 is disposed in a kiln furnace (not shown) in a state where the firing objects 50 and 52 are placed on the upper surface 211 of the firing shelf 213, and fired. Firing of the objects 50 and 52 is performed.

  Here, the objects to be fired 50 and 52 are electronic parts such as a multilayer ceramic capacitor or a honeycomb structure for purifying automobile exhaust gas. That is, the above-described firing jig 210 can be used for firing electronic components and honeycomb structures. In addition, although the to-be-fired products 50 and 52 are the laminated ceramic capacitor and the honeycomb structure in the above, this is an example and is not limited. That is, the objects to be fired 50 and 52 may be of any kind as long as they are parts to be fired, such as a chip inductor and a semiconductor substrate.

  The firing jig 210 according to the embodiment includes the silicon carbide aggregate 8 having an average particle diameter of preferably 3 mm or less, more preferably 600 μm or more and 1.8 mm or less. In order for the aggregate 8 to have the above-described average particle diameter, for example, the average particle diameter of the aggregate particles 5 is preferably 3 mm or less, more preferably 600 μm to 1.8 mm.

  Further, the bending strength of the firing jig 210 is preferably 7 MPa or more and 30 MPa or less, more preferably 10 MPa or more and 25 MPa or less.

  Further, the high temperature bending strength at 1500 ° C. or less of the firing jig 210 is preferably 7 MPa or more and 30 MPa or less, and more preferably 10 MPa or more and 25 MPa or less. By setting the high-temperature bending strength in the above-described range, it can be appropriately used even under relatively high temperature conditions exceeding 1500 ° C., for example.

  The thickness t2 of the firing jig 210 is preferably 5 mm or more and 30 mm or less, and more preferably 7 mm or more and 15 mm or less. If the thickness t2 is less than 5 mm, for example, deformation at a high temperature is likely to occur, and the service life may be shortened. On the other hand, if the thickness t2 exceeds 30 mm, for example, the physique of the firing jig 210 becomes large and may not be suitable for actual use.

  8A and 8B show an example in which the baking jig 210 according to the embodiment includes one baking shelf 213, but two or more baking shelves 213 supported by a support column are shown. You may use it simultaneously. 8A and 8B show an example in which two baking objects 50 and 52 are placed on one baking shelf 213, but one or three or more baking objects are fired on one sheet. It may be placed on the shelf board 213. 8A and 8B have been described on the assumption that the firing jig 210 is the porous body 11, the present invention is not limited thereto. Among the members constituting the firing jig 210, at least a part of the firing jig 210 is composed of the porous body 11, for example, only the firing shelf 213 is composed of the porous body 11. It only has to be. Furthermore, in FIGS. 8A and 8B, the shape of the baking shelf 213 is substantially rectangular when viewed from above, but is not limited thereto. In other words, the shape of the baking shelf 213 viewed from the top may be, for example, a polygon such as a square or a triangle, or another shape such as a circle or an ellipse.

  In the above-described embodiment, the simple-shaped porous body 11 configured by a single structure has been described. However, the present invention is not limited to this. That is, the plurality of porous bodies 11 obtained as described above are joined using a joining material, and this is used in place of the porous body 11 for the molten metal filter 110, the firing jig 210, and the like. May be. This point will be described with reference to FIGS. 9 to 10C. First, an example of a porous joined body formed by joining a plurality of porous bodies 11 will be described with reference to FIG.

  FIG. 9 is a cross-sectional view for explaining the outline of the porous joined body according to the embodiment. As shown in FIG. 9, the porous joined body 310 according to the embodiment includes a first member 311, a second member 312, and a joining layer 313. The first member 311 and the second member 312 are each composed of a porous body 11 having a simple shape. The bonding layer 313 is disposed so as to be sandwiched between the first member 311 and the second member 312, and the first member 311 and the second member 312 formed of the porous body 11 are connected to each other. A porous bonded body 310 having a complicated shape is formed. The porous joined body 310 having such a configuration is manufactured as follows, for example.

  The bonding layer 313 is formed by firing a bonding material for bonding the first member 311 and the second member 312. That is, when the bonding material is held so as to be sandwiched between the first member 311 and the second member 312, and fired together with the first member 311 and the second member 312, the porous bonded body 310 including the bonding layer 313 is obtained. can get. Thereby, the porous joined body 310 having a complex shape can be formed by combining a plurality of porous bodies 11 having a simple shape. At this time, it is preferable that the bonding material contains silicon carbide powder, since generation of cracks and peeling at the bonded portion is suppressed, and an integrated porous bonded body 310 having high strength and high heat resistance can be obtained. .

  Here, the porous joined body 310 will be further described. In the porous joined body 310, the average particle diameter of the aggregate made of silicon carbide is preferably 200 μm to 5 mm, more preferably 300 μm to 4 mm. By setting the average particle diameter of the aggregate within the above-described range, performance equivalent to that of the above-described porous body 11 can be ensured. Here, the average particle diameter of the aggregate in the porous joined body 310 can be measured in the same manner as described above. That is, a porous bonded body 310 including a bonding layer 313 is prepared, a SEM (Scanning Electron Microscope) image of the cross section is taken, the particle size of the aggregate is measured from the SEM image by the intercept method, and the particle size distribution is obtained. .

  Further, the porosity, average pore diameter, bending strength, high temperature bending strength, thermal conductivity, thermal shock resistance and thermal temperature of the porous joined body 310 can be obtained from a porous metal filtration filter 110, a firing jig 210, etc. It is preferable to have performance according to the application applied as an alternative to the mass 11. Here, the porosity, average pore diameter, bending strength, high temperature bending strength, thermal conductivity, thermal shock resistance and thermal temperature of the porous bonded body 310 are single layer porous except that the bonding layer 313 is included in the center. Using the samples prepared to have the same dimensions as the mass 11, the same measurements as the bending strength, high-temperature bending strength, thermal conductivity, thermal shock resistance and thermal resistance in the single-layer porous body 11 are performed, The result can be a measured value. For the bending strength and the high temperature bending strength, the bonding layer 313 is included in the center in the length direction, and the maximum bending load is applied in the vicinity of the bonding layer 313.

  Next, the bonding layer 313 will be further described. Bonding layer 313 includes a silicon carbide powder having an average particle diameter of preferably 500 μm or less, more preferably 50 μm or more and 300 μm or less. In order for the silicon carbide powder to have the above average particle size, for example, the average particle size of the silicon carbide powder contained in the bonding material is preferably 500 μm or less, more preferably 50 μm or more and 300 μm or less. By setting the average particle diameter of the silicon carbide powder within the above-described range, it is possible to suppress the occurrence of cracking and peeling at the bonded portion, and to obtain an integrated porous bonded body 310 having high strength and high heat resistance. it can. A specific blending example of the bonding material will be described later.

  The porosity of the bonding layer 313 is preferably 10% by volume or more and 40% by volume or less. By setting the porosity of the bonding layer 313 in the above-described range, communication with the porous body 11 in contact with the bonding layer 313 can be ensured, for example, degassing property when used as a firing jig is improved, The presence of appropriate pores may improve the thermal shock resistance.

  The bulk specific gravity of the bonding layer 313 is preferably 1.9 or more and 2.9 or less. By setting the bulk specific gravity of the bonding layer 313 in the above-described range, the porosity can easily fall within an appropriate range suitable for the application, and the porous bonded body 310 suitable for actual use can be easily formed.

  In addition, the bonding layer 313 has a silicon carbide content of preferably 95% by mass or more, and more preferably 99% or more. By making content of silicon carbide into the above-mentioned range, the fall of the high temperature bending strength mentioned later can be suppressed.

  The thickness of the bonding layer 313 is preferably 500 μm or more and 3 mm or less. By setting the thickness of the bonding layer 313 in the above-described range, the occurrence of cracks at the bonded portion and peeling at the bonded interface is suppressed. The average particle diameter of the silicon carbide powder in the bonding layer 313 can be measured by the same method as the average particle diameter of the aggregate 8 in the single-layer porous body 11. Further, the thickness of the bonding layer 313 can be measured based on an SEM image obtained by imaging a cross section. Further, the porosity of the bonding layer 313 and the bulk specific gravity of the bonding layer 313 can be measured by the same method as the measurement of the porosity and bulk specific gravity of the single-layer porous body 11.

  Next, a bonding material applied for forming the bonding layer 313 will be described. Specifically, the bonding material is, for example, 30 to 70% by mass of silicon carbide powder A having an average particle size of 160 to 240 μm and 5 to 15% by mass of silicon carbide powder B having an average particle size of 8 to 12 μm. In addition, silicon carbide powder C having an average particle diameter of 1 to 5 μm is 30 to 50% by mass, graphite having an average particle diameter of 0.3 to 0.7 μm is 0.3 to 0.8% by mass, It contains 3 to 7% by mass of dextrin and 0.02 to 0.5% by mass of cellulose and 10 to 20% by mass of water, which are saccharide binders. Thus, it is preferable to apply as a bonding material a combination of a plurality of silicon carbide powders having different average particle diameters. These materials are put into a mixing container and uniformly mixed using a mixing stirrer to obtain the above-described bonding material.

  The porous bonded body 310 having a complicated shape and bonded using the bonding material thus obtained has the same strength and thermal shock resistance as the porous body 11 which is a single structure. That is, there is no occurrence of cracking or peeling at the bonding interface. The bonding material is not necessarily limited to the above-described composition and blending ratio, and may be any composition and blending ratio as long as the porous bonded body 310 having the required strength and thermal shock resistance can be obtained. .

  Next, another example of the porous joined body formed by joining a plurality of porous bodies 11 will be described with reference to FIGS. 10A to 10C. FIG. 10A is a perspective view illustrating an outline of a porous joined body according to an embodiment. 10B is a top view of FIG. 10A, and FIG. 10C is a cross-sectional view taken along the line C-C ′ of FIG. 10B.

  As shown in FIGS. 10A to 10C, the porous bonded body 410 according to the embodiment includes side plates 411, 412, 413 and 414 and a bottom plate 415. Each of the side plates 411 to 414 and the bottom plate 415 is composed of a flat plate-like porous body 11, and the porous bonded body 410 has a box shape in which an upper portion of the bottom plate 415 is opened.

  In the porous joined body 410, adjacent members are joined together through a joining layer and integrated. Specifically, as shown in FIG. 10C, the side plates 413, 414 and the bottom plate 415 are joined together via a joining layer 416 formed by firing of a joining material. Moreover, although illustration description is abbreviate | omitted, the side plates 411 and 412 and the bottom plate 415 are joined through the joining layer 416, respectively. Further, although detailed description is omitted, the side plates 411 to 414 are also joined to each other through the bonding layer 416. Here, as the bonding layer 416, a layer having the same performance as the above-described bonding layer 313 can be used.

  Such a porous bonded body 410 can be used, for example, as a so-called box filter (hereinafter also referred to as “box filter 410”) for storing the molten metal that has been removed by removing inclusions contained in the molten metal.

  An example of a method for removing inclusions contained in the molten metal using the box filter 410 will be described below. First, the box filter 410 is disposed so that a part of the outer wall surface of the side plates 411, 412, 413 and 414 is immersed in the molten metal such as aluminum from the outside of the bottom plate 415, that is, from the lower side. The molten metal flows inward from the outer wall surfaces of the side plates 411, 412, 413 and 414, the bottom plate 415 and the bonding layer 416, and the inclusions in the molten metal include the side plates 411, 412, 413 and 414, the bottom plate 415 and It is collected by the bonding layer 416. The purified metal melt is stored inside the box filter 410.

  The molten metal stored in the box filter 410 is used as, for example, a die casting or other molding material. The shape and configuration of the box filter 410 are not limited to those shown in FIGS. 10A to 10C, and may be any shape.

  Next, a method for manufacturing the porous body 11 according to the embodiment will be described in detail with reference to FIG. FIG. 3 is a flowchart showing a processing procedure for manufacturing the porous body 11 according to the embodiment.

  As shown in FIG. 3, first, the binder particles 3 including the first binder particles 1 and the second binder particles 2 having an average particle diameter larger than that of the first binder particles 1 are mixed ( Step S11). Next, the binder particles 3 mixed in step S11 are sprayed with a solution containing a liquid medium and a binder, and mixed to granulate (step S12).

  Subsequently, the silicon carbide granule 4 obtained in step S12 is mixed with the silicon carbide aggregate particles 5 (step S13). Next, the mixture containing the granulated body 4 and the aggregate particles 5 produced in step S13 is kneaded, put into a mold having a shape corresponding to the application, and molded by press molding (step S14).

  Further, the molded body 6 obtained by molding is dried (step S15), and then the molded body 6 is fired in a state of being embedded in silica powder and carbon powder (step S16). Through the above steps, the production of the series of porous bodies 11 according to the embodiment is completed.

  In the above-described embodiment, the example of producing the granulated body 4 to which the stirring granulation method is applied as step S12 has been described. However, the method is not limited thereto as long as the same granulated body 4 can be produced. For example, a tumbling granulation method, a spray drying method, or the like may be applied.

  In the above-described embodiment, an example of producing the molded body 6 to which the press molding method is applied as step S14 has been described. However, any method that can press and mold the mixture placed in the mold in the same manner will be used. For example, an isostatic pressing method may be applied.

  Furthermore, the manufacturing method of the porous body which concerns on embodiment is not limited to an above-described thing. Below, the 1st modification of the method of manufacturing the porous body which concerns on embodiment is demonstrated using FIG. 4, FIG.

  FIG. 4 is a flowchart showing a processing procedure for manufacturing the porous body according to the embodiment, and FIG. 5 is an explanatory diagram for explaining the outline of the method for manufacturing the porous body according to the embodiment.

  As shown in FIG. 4, first, the binder particles and the dispersion medium are mixed (step S21). Here, the same binder particles as those described above can be applied to the binder particles. That is, the binder particles may include both the first binder particles 1 and the second binder particles 2 described above, or only one of them may be applied.

  In addition, a liquid medium having a relatively high volatility is applied as the dispersion medium. Specific examples include water, methanol, ethanol, isopropyl alcohol, acetone, and ethyl acetate, but are not limited thereto. Moreover, you may apply as a dispersion medium what melt | dissolved 1 or 2 or more types of organic binders according to the kind of liquid medium. Specific examples of such an organic binder include, but are not limited to, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and acrylic resin.

  Next, the slurry 16 obtained in step S21 is poured into the aggregate particles 15 and shaped (step S22). Specifically, as shown in the upper part of FIG. 5, the silicon carbide aggregate particles 15 are spread in a mold (not shown), the slurry 16 is poured into the mold, and the remaining slurry 16 is removed from the mold. Let it drain. On the surface of the aggregate particles 15, a layer of the slurry 16 having a substantially uniform thickness is formed according to the properties such as the viscosity of the slurry 16, while the adjacent aggregate particles 15 are in contact with or close to each other. Then, according to the surface tension which the dispersion medium contained in the slurry 16 has, the slurry 16 adheres to the film thickness more than other portions (see the middle stage in FIG. 5). Thus, the molded object 18 provided with the aggregate particles 15 and the binder particles contained in the slurry 16 and having the voids 17 formed at locations where the slurry 16 is not filled is obtained. Here, the aggregate particles 15 may be the same as the aggregate particles 5 described above, and detailed description thereof is omitted.

  Further, the molded body 18 obtained by molding is dried (step S23), and then the molded body 18 is fired in a state of being embedded in silica powder and carbon powder (step S24). The manufacturing of the fired body (porous body) 21 shown in the lower part of FIG.

  As described above, according to the method for manufacturing the porous body 21 according to the embodiment, the aggregate 19 according to the size of the aggregate particle 15 and the binder 20 according to the composition of the slurry 16 are included, and the void 17 The porous body 21 including the corresponding pores 22 is obtained. The porous body 21 has a thermal shock resistance as compared with the average pore diameter and the porosity because the binder particles remaining densely between the adjacent aggregate particles 15 appropriately assist the bonding of the aggregate particles 15. And high temperature strength.

  In the lower part of FIG. 5, the porous body 21 in which the binding material 20 is disposed only in the vicinity of the adjacent aggregate 19 is illustrated, but the binding is performed so as to cover a part or the whole of the aggregate 19. A material 20 may be further arranged.

  Next, the 2nd modification of the method to manufacture the porous body which concerns on embodiment is demonstrated using FIG. 6, FIG.

  FIG. 6 is a flowchart showing a processing procedure for manufacturing the porous body according to the embodiment, and FIG. 7 is an explanatory diagram for explaining the outline of the method for manufacturing the porous body according to the embodiment.

  As shown in FIG. 6, first, binder particles, a solidifying agent, and a dispersion medium are mixed (step S31). Here, the same binder particles as those used in the slurry 16 are applied. That is, the binder particles may include both the first binder particles 1 and the second binder particles 2 described above, or only one of them may be applied.

  As the solidifying agent, for example, one or two or more types known as a gelling agent and a curing agent are applied. Specific examples include, but are not limited to, epoxy resins, phenol resins, urea resins, and polyamine curing agents.

  As the dispersion medium, a liquid medium similar to that used in the slurry 16 is applied. Specific examples include water, methanol, ethanol, isopropyl alcohol, acetone, and ethyl acetate, but are not limited thereto.

  Next, the slurry 26 obtained in step S31 is adhered to the aggregate particles 25 (step S32). Specifically, for example, when the slurry 26 and the aggregate particles 25 are mixed at an appropriate ratio, the surface of the aggregate particles 25 has a substantially uniform thickness according to the properties such as the viscosity of the slurry 26. Slurry 26 adheres. Here, the aggregate particles 25 can be the same as the aggregate particles 5 and 15 described above, and detailed description thereof is omitted. Moreover, the compounding ratio of the slurry 26 and the aggregate particle 25 can be set to, for example, 10:90 to 30:70 in terms of mass. By defining the blending ratio of the slurry 26 and the aggregate particles 25 in this way, the average pore diameter and porosity can be made suitable for actual use as a porous body.

  Next, the aggregate particles 25 to which the slurry 26 is adhered are put into a mold and molded (step S33). In the above-described molded body 24, the dispersion medium contained in the slurry 26 has a portion in contact with or close to the adjacent aggregate particle 25 so that the binder particles in the slurry 26 adhere more than other portions. Move according to surface tension. Thereby, the molded object 24 in which the space | gap 27 was formed between the aggregate particle 25 to which the slurry 26 was adhered is obtained (refer the upper stage of FIG. 7).

  Subsequently, the slurry 26 in the molded body 24 obtained by molding is cured (step S34). Specifically, depending on the type of the solidifying agent contained in the slurry 26, it is caused to act by an appropriate operation such as natural drying, heating, or light irradiation, and thereby between the adjacent aggregate particles 25 and the aggregate particles. Cured slurry 28 is formed on the outer periphery of 25 (see the middle stage of FIG. 7).

  Further, the molded body 24 on which the slurry 26 is cured and the cured slurry 28 is formed is degreased (step S35). Specifically, a process of decomposing and removing organic components such as a solidifying agent is performed under a predetermined temperature condition according to the type of the aggregate particles 25 and the binder particles. In addition, in this step S35 or above-mentioned step S34, you may perform the drying process which removes the water | moisture content in the molded object 24 as needed. Further, depending on the type and blending amount of the organic component such as the solidifying agent, step S35 may be omitted.

  Finally, the molded body 24 is fired while being embedded in silica powder and carbon powder (step S36). Through the above steps, the manufacture of the fired body (porous body) 31 shown in the lower part of FIG. 7 is completed.

  Thus, according to the manufacturing method of the porous body 31 according to the embodiment, the aggregate 29 according to the size of the aggregate particles 25 and the binder 30 according to the composition of the slurry 26 are included, and the void 27 A fired body 31 including the corresponding pores 32 is obtained. The fired body 31 has a thermal shock resistance as compared with the average pore diameter and porosity by the binder particles remaining densely between the adjacent aggregate particles 25 appropriately assisting the bonding of the aggregate particles 25. In addition, it is excellent in high temperature strength.

  In the lower part of FIG. 7, the fired body 31 in which the binding material 30 is disposed only in the vicinity of the adjacent aggregate 29 is illustrated, but the binding material is covered so as to cover a part or the whole of the aggregate 29. 30 may be further arranged.

  In FIG. 9, the first member 311 and the second member 312 are both described as being the porous body 11, but one or both of the first member 311 and the second member 312 are porous. The mass 21 may be sufficient, and the porous body 31 may be sufficient.

  In the above-described embodiment, the fired porous body 11 (21, 31) is applied as the first member 311 and the second member 312, and these are bonded with a bonding material to form the porous bonded body 310. Although described as forming, the method for producing the porous bonded body 310 is not limited to this. For example, the porous bonded body 310 may be formed by holding and holding the bonding material between the molded body 6 before firing corresponding to the first member 311 and the second member 312 and firing them. Good.

  As described above, the porous body according to the embodiment includes a silicon carbide aggregate having an average particle diameter of 800 μm or more and 4 mm or less and a silicon carbide binder for bonding the aggregate. The average pore diameter is 200 μm or more, the porosity is 30% by volume or more, and the contents of metallic silicon and boron are 1% by mass or less.

  Therefore, according to the porous body which concerns on embodiment, the porous body excellent in the thermal shock resistance and high temperature strength can be provided.

Example 1
Silicon carbide powder with an average particle size of 4 μm (SiC content 99 mass% or more, corresponding to “first binder particle 1”) 65 mass% and silicon carbide powder with an average particle size of 10 μm (SiC content 99 mass) 15% by mass, corresponding to “second binder particle 2”), 2% by mass of organic binder (PVA), and 18% by mass of water are mixed and granulated by a high-speed mixing / granulating machine. A granulated body 4 having an average particle diameter of 50 μm was obtained.

Silicon carbide powder having an average particle diameter of 2 mm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) 75% by mass, the obtained granule 4 15% by mass, a polysaccharide binder ( Dextrin) 5 mass% and water 5 mass% were stirred using a mixing stirrer to obtain a mixture. Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. Then, the molded body 6 was fired in an argon atmosphere with a sintering temperature of 2300 ° C. in a state of being embedded in carbon powder and silica powder, to obtain a porous body 11 (a metal melt filter filter 110) having a thickness t1 of 25 mm. .

(Example 2)
Silicon carbide powder having an average particle size of 4 μm (SiC content 99% by mass or more, corresponding to “binding material particle 3”) 80% by mass, organic binder (PVA) 2% by mass, water 18% by mass, Mixing and granulating were carried out with a mixing and granulating machine to obtain a granulated body 4 having an average particle diameter of 40 μm.

Silicon carbide powder having an average particle diameter of 2 mm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) 75% by mass, the obtained granule 4 15% by mass, a polysaccharide binder ( Dextrin) 5 mass% and water 5 mass% were stirred using a mixing stirrer to obtain a mixture. Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. Then, the compact 6 was fired in an argon atmosphere with a sintering temperature of 2350 ° C. in a state where the compact 6 was embedded in carbon powder and silica powder to obtain a porous body 11 (a metal melt filter filter 110) having a thickness t1 of 70 mm. .

(Example 3)
Silicon carbide powder with an average particle size of 4 μm (SiC content 99 mass% or more, corresponding to “first binder particle 1”) 65 mass% and silicon carbide powder with an average particle size of 10 μm (SiC content 99 mass) 15% by mass, corresponding to “second binder particle 2”), 2% by mass of organic binder (PVA), and 18% by mass of water are mixed and granulated by a high-speed mixing / granulating machine. A granulated body 4 having an average particle diameter of 55 μm was obtained.

Silicon carbide powder having an average particle diameter of 2 mm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) 60% by mass, the obtained granulated body 4 by 30% by mass, a polysaccharide binder ( Dextrin) 5 mass% and water 5 mass% were stirred using a mixing stirrer to obtain a mixture. Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. Then, the molded body 6 was fired in an argon atmosphere with a sintering temperature of 2450 ° C. in a state of being embedded in carbon powder and silica powder, to obtain a porous body 11 (a metal melt filter filter 110) having a thickness t1 of 18 mm. .

Example 4
In a ball mill, silicon carbide powder having an average particle size of 4 μm (SiC content 99% by mass or more, corresponding to “binder particles”) 60% by mass, organic binder (PVA) 2% by mass, and water 38% by mass By mixing, slurry 16 was obtained.

  Silicon carbide powder having an average particle diameter of 2 mm (SiC content of 99% by mass or more, corresponding to “aggregate particles 15”) is placed in a mold placed on a metal mesh. The 50 mass% slurry 16 obtained by the above procedure is poured into the aggregate particles 15 spread on the mold, and the remaining slurry 16 is discharged from the mold on the metal mesh, so that the 80 mass% aggregate particles 15 are discharged. And the molded object 18 containing 20 mass% slurry 16 was obtained. The obtained molded body 18 was dried and then fired in an argon atmosphere with a sintering temperature of 2250 ° C. in a state of being embedded in carbon and silica, and the porous body 21 having a thickness t1 of 30 mm (the filter filter 110 for molten metal). )

(Example 5)
Silicon carbide powder with an average particle size of 4 μm (SiC content 99% by mass or more, corresponding to “binding material particles”) 75% by mass, gelling agent (epoxy resin) 1% by mass as a solidifying agent and curing agent (polyamine) (System hardening agent) 1% by mass and 23% by mass of water were mixed in a ball mill to obtain slurry 26.

  Next, 25 mass% of the obtained slurry 26 and 75 mass% of silicon carbide powder having an average particle diameter of 2 mm (SiC content of 99 mass% or more, corresponding to “aggregate particle 25”) were mixed using a mixing stirrer. Then, the slurry 26 was adhered to the surface of the aggregate particles 25.

  Aggregate particles 25 to which the slurry 26 was adhered were placed in a mold to obtain a molded body 24. The obtained molded body 24 was dried and the slurry 26 was cured at 80 ° C., and then fired in an argon atmosphere at 2300 ° C. in a state of being embedded in carbon and silica, and a porous body 31 (thickness t 1 of 25 mm) ( A molten metal filtration filter 110) was obtained.

(Example 6)
A porous body 11 (firing jig 210) having a thickness t2 of 12 mm was obtained in the same manner as in Example 1 except that the shape of the molded body 6 was changed.

(Example 7)
Except that the shape of the molded body 6 was changed, a porous body 11 (firing jig 210) having a thickness t2 of 30 mm was obtained in the same manner as in Example 2.

(Example 8)
A porous body 11 (firing jig 210) having a thickness t2 of 6 mm was obtained in the same manner as in Example 3 except that the shape of the molded body 6 was changed.

Example 9
A porous body 21 (firing jig 210) having a thickness t2 of 16 mm was obtained in the same manner as in Example 4 except that the shape of the molded body 18 was changed.

(Example 10)
Except that the shape of the molded body 24 was changed, a porous body 31 (firing jig 210) having a thickness t2 of 10 mm was obtained in the same manner as in Example 5.

(Example 11)
50% by mass of silicon carbide powder having an average particle size of 200 μm, 10% by mass of silicon carbide powder having an average particle size of 10 μm, 40% by mass of silicon carbide powder having an average particle size of 5 μm, and 0.5% of graphite having an average particle size of 0.5 μm 2% by mass of dextrin and 2% by mass of dextrin and 0.1% by mass of cellulose and 20% by mass of water were mixed using a mixing stirrer to obtain a bonding material.

  Next, two plate-like porous bodies 11 (corresponding to the firing jig 210 produced in Example 6) are prepared in advance, and the obtained bonding material is applied to the surface of one porous body 11 with a brush. The surface to which the bonding material was applied was applied to the surface of the other porous body 11 and pressed. Next, the two porous bodies 11 with the bonding material sandwiched between them are baked in an argon atmosphere with a sintering temperature of 2300 ° C. while being embedded in carbon powder and silica powder, and the two porous bodies 11 ( A porous joined body 310 having a structure in which the first member 311 and the second member 312 are joined to each other was obtained.

(Comparative Example 1)
Silicon carbide powder with an average particle size of 150 μm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) and 75% by mass of silicon carbide powder with an average particle size of 4 μm (SiC content 99% by mass or more, (Corresponding to “first binder particle 1”) 10% by mass, silicon carbide powder having an average particle diameter of 10 μm (SiC content 99% by mass or more, corresponding to “second binder particle 2”) 5% by mass And 5 mass% of organic binders (dextrin) and 5 mass% of water were stirred using the mixing stirrer, and the mixture was obtained.

Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. Then, the molded body 6 was fired in an argon atmosphere with a sintering temperature of 2300 ° C. in a state of being embedded in carbon powder and silica powder to obtain a fired body (filter for molten metal) having a thickness t1 of 30 mm.

(Comparative Example 2)
Silicon carbide powder with an average particle size of 150 μm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) and 75% by mass of silicon carbide powder with an average particle size of 4 μm (SiC content 99% by mass or more, (Corresponding to “first binder particle 1”) 10% by mass, silicon carbide powder having an average particle diameter of 10 μm (SiC content 99% by mass or more, corresponding to “second binder particle 2”) 5% by mass And 5 mass% of organic binders (dextrin) and 5 mass% of water were stirred using the mixing stirrer, and the mixture was obtained.

Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. And the molded object 6 was baked in the argon atmosphere with a sintering temperature of 2400 degreeC in the state which embedded carbon powder and the silica powder, and the sintered compact (filtration filter for molten metal) whose thickness t1 is 40 mm was obtained.

(Comparative Example 3)
Silicon carbide powder with an average particle size of 4 μm (SiC content 99 mass% or more, corresponding to “first binder particle 1”) and silicon carbide powder with an average particle size of 10 μm (SiC content 99 mass) 10% by weight, 40% by weight of metal silicon having an average particle size of 2 μm, 2% by weight of organic binder (PVA), and 18% by weight of water. Then, they were mixed and granulated with a high-speed mixing / granulating machine to obtain a granulated body 4 having an average particle diameter of 50 μm.

Silicon carbide powder with an average particle size of 150 μm (SiC content 99% by mass or more, corresponding to “aggregate particle 5”) 80% by mass, the obtained granule 4 10% by mass, a polysaccharide binder ( Dextrin) 5 mass% and water 5 mass% were stirred using a mixing stirrer to obtain a mixture. Next, the obtained mixture was press-molded at a pressure of 0.05 ton / cm ² or more to obtain a molded body 6. And the molded object 6 was baked in argon atmosphere with a sintering temperature of 2250 degreeC in the state embedded in the carbon powder and the silica powder, and the sintered compact (filtration filter for molten metal) whose thickness t1 is 20 mm was obtained.

(Comparative Example 4)
A fired body (firing jig) having a thickness t2 of 10 mm was obtained by the same method as in Comparative Example 1 except that the shape of the molded body 6 was changed.

(Comparative Example 5)
A fired body (firing jig) having a thickness t2 of 30 mm was obtained in the same manner as in Comparative Example 2 except that the shape of the molded body 6 was changed.

(Comparative Example 6)
A fired body (firing jig) having a thickness t2 of 15 mm was obtained in the same manner as in Comparative Example 3 except that the shape of the molded body 6 was changed.

  Aggregate average particle diameter, porosity of porous body (fired body), average pore diameter, bulk specific gravity, bending strength, high temperature bending strength (1500 ° C.), metallic silicon and boron content in each example and comparative example Table 1 summarizes the SiC content, thermal conductivity, thermal shock resistance and thermal temperature. Here, “thermal shock resistance” was measured as follows.

  First, a sample was produced by firing and processing the porous body so as to have a size of 400 mm × 400 mm × thickness 30 mm. Next, this sample is placed on a brick setter of the same size via pillars placed at the four corners, heated at a high temperature in an electric furnace and maintained at a desired temperature for 1 hour or more, and then quickly from the electric furnace. The sample was taken out and exposed to room temperature air, and the presence or absence of cracking of the sample was evaluated with the naked eye. Sequential evaluation was performed while increasing the set temperature from 300 ° C. to 550 ° C. by 50 ° C., and the upper limit of the temperature at which cracking did not occur was defined as the value of “thermal shock resistance”.

  The “heat-resistant temperature” was measured as follows. First, a sample was prepared by firing and processing the porous body so as to have a size of 20 mm × 10 mm × thickness 120 mm. A jig with a span length of 90 mm was placed in an electric furnace, and a sample was placed on the jig. Next, a load corresponding to 50% of the normal temperature bending strength was applied to the center of the sample, heated at a high temperature and maintained at a desired set temperature for 4 hours or more, then the temperature was lowered to room temperature, and the sample was checked for deflection. To confirm the deflection, a straight scale was applied in the length direction of the sample, and the gap between the straight scale and the sample was evaluated with a gap gauge. Sequential evaluation was performed while increasing the set temperature from 800 ° C. to 1700 ° C. by 50 ° C., and the temperature when the sample was damaged or bent 3 mm or more was defined as the value of “heat resistance temperature”.

  Further, for Example 11, the average particle diameter of the silicon carbide powder in the bonding layer 313, the thickness of the bonding layer 313, the porosity of the bonding layer 313, and the bulk specific gravity of the bonding layer 313 are the porous bonding including the bonding layer 313. Aggregate average particle diameter, porosity, average pore diameter, bending strength, mode of fracture, high temperature bending strength (1500 ° C.), mode of fracture at high temperature, thermal conductivity, thermal shock resistance and thermal temperature The results are shown in Table 2.

  The mode of fracture of the porous bonded body 310 is evaluated by classifying the fractured specimen into three groups by observing the tensile surface of the fractured sample after evaluating the bending strength. Specifically, the case where the fracture occurs from the base material, that is, the first and second members 311, 312 is evaluated as the base material crack, the case where the fracture occurs from the joint interface, and the case where the fracture occurs from the joint layer 313 is evaluated as the joint layer crack. did. The fracture mode of the porous joined body 310 at a high temperature is obtained by evaluating the observation result in the same manner as the fracture mode of the porous joined body 310 described above after the evaluation of the high temperature bending strength.

  In addition, although description was abbreviate | omitted, about Examples 6-10 and Comparative Examples 4-6 from which Examples 1-5 and Comparative Examples 1-3 differ only in a shape, above-mentioned Examples 1-5 and Comparative Examples 1-6. Measurement results similar to those of No. 3 were obtained.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 1st binder particle 2 2nd binder particle 3 Binder particle 4 Granulated body 5,15,25 Aggregate particle 6,18,24 Molded body 7,17,27 Space | gap 8,19,29 Aggregate 9, 20, 30 Binder 10 Neck 11, 21, 31 Porous body (fired body)
12, 22, 32 Pore 16, 26 Slurry 28 Cured slurry 110 Filtration filter 113 for molten metal Outer peripheral surface 114 Inner peripheral surface 210 Firing jig 213 Firing shelf 310 Porous bonded body 410 Porous bonded body (box filter)

Claims (23)

An aggregate of silicon carbide having an average particle diameter of 800 μm or more and 4 mm or less;
A silicon carbide binder for bonding the aggregate,
A porous body having an average pore diameter of 200 μm or more, a porosity of 30% by volume or more, and a content of metal silicon and boron of 1% by mass or less.   The porous body according to claim 1, wherein the bulk specific gravity is 1.5 or more and 2.3 or less.   The porous body according to claim 1 or 2, wherein the content of silicon carbide is 95 mass% or more.   The porous body according to any one of claims 1 to 3, wherein the thermal conductivity is 10 W / (m · K) or more and 80 W / (m · K) or less. A plurality of porous bodies;
A bonding layer for bonding the plurality of porous bodies,
Each of the plurality of porous bodies is a porous joined body which is the porous body according to any one of claims 1 to 4.   The filter for molten metal containing the porous body as described in any one of Claims 1-4.   A filter for molten metal including the porous joined body according to claim 5.   The filter for molten metal according to claim 6 or 7, wherein the bending strength is 2 MPa or more and 15 MPa or less.   The filter for molten metal according to any one of claims 6 to 8, wherein a high-temperature bending strength at 1500 ° C or lower is 2 MPa or more and 15 MPa or less.   The filter for molten metal according to any one of claims 6 to 9, having a thickness of 15 mm or more and 100 mm or less.   A firing jig comprising the porous body according to claim 1.   A firing jig comprising the porous joined body according to claim 5.   The firing jig according to claim 11 or 12, wherein the bending strength is 7 MPa or more and 30 MPa or less.   The firing jig according to any one of claims 11 to 13, wherein a high-temperature bending strength at 1500 ° C or less is 7 MPa or more and 30 MPa or less.   The firing jig according to any one of claims 11 to 14, which has a thickness of 5 mm to 30 mm.   The firing jig according to any one of claims 11 to 15, wherein an average particle diameter of the aggregate is 3 mm or less. A granulation step of granulating a mixture containing binder particles;
A molding step of molding a mixture of a granulated body of silicon carbide having an average particle size of 10 μm or more obtained by the granulation step and an aggregate particle of silicon carbide having an average particle size of 800 μm or more and 4 mm or less;
The manufacturing method of the porous body as described in any one of Claims 1-4 including the baking process which bakes the molded object obtained by the said shaping | molding process. A mixing step of mixing the binder particles and the dispersion medium;
A molding step in which the slurry obtained by the mixing step is poured into an aggregate particle of silicon carbide having an average particle diameter of 800 μm or more and 4 mm or less;
The manufacturing method of the porous body as described in any one of Claims 1-4 including the baking process which bakes the molded object obtained by the said shaping | molding process. A mixing step of mixing the binder particles, the solidifying agent, and the dispersion medium;
An attaching step of attaching the slurry obtained by the mixing step to an aggregate particle of silicon carbide having an average particle diameter of 800 μm or more and 4 mm or less;
A molding process in which the aggregate particles to which the slurry is attached are put into a mold and molded;
A curing step of curing the slurry in the molded body obtained by the molding step;
The manufacturing method of the porous body as described in any one of Claims 1-4 including the baking process which bakes the molded object which hardened the slurry.   20. The binder material according to any one of claims 17 to 19, wherein the binder particles include first binder particles and second binder particles having an average particle diameter larger than that of the first binder particles. A method for producing a porous body.   The method for producing a porous body according to any one of claims 17 to 20, wherein the porous body is a filter for molten metal.   The manufacturing method of the porous body as described in any one of Claims 17-20 whose said porous body is a jig | tool for baking.   The method for producing a porous body according to claim 22, wherein an average particle diameter of the aggregate particles is 3 mm or less.

Images