The present invention relates to a container which can accommodates an object such as liquid, for example, a container which can accommodate a molten metal such as a metal or an alloy of the metals such as aluminum, magnesium, and zinc inside the container.
1. Background Art
A casting process has a feature in which a shape can be easily given to a product. The casting process is a basic technology in manufacturing many mechanical components for an automobile or the like. An ordinary casting process includes steps of melting a casting material (raw material), filling a container with a molten material (molten metal), carrying the container to a casting apparatus, and casting the molten metal with the casting apparatus.
Ordinarily, a container used for delivering the molten metal constantly has a problem of a dissipative heat loss. Heat of the molten metal filling the container is externally dissipated via a wall constituting the container. Therefore, the temperature of the molten metal inside the container decreases while the container is carried, and the molten metal having a predetermined temperature is not obtainable after starting casting. In view of the energy loss, the dissipative heat loss greatly affects an entire casting process. In this case, when casting is started, it is necessary to raise the temperature of the molten metal filling the container to be an excessively high temperature in advance in order to obtain a molten metal having a predetermined temperature. With this, energy consumed in an entire process greatly increases.
In order to suppress a dissipative heat loss, there is an example that a cavity causing a reduced pressure is provided on a wall surface constituting a container (Patent Document 1).
2. Related Art
However, a container disclosed in Patent Document 1 has a problem that a relationship between a contact area in contact with a heat source and heat transmission inside the container is not considered.
Generally speaking, heat may be transferred more easily as the area in contact with the heat source increases. Therefore, a dissipative heat loss is apt to be generated. However, the contact area of the container of Patent Document 1 is relatively large inside an internal space of the container. Therefore, an effect of suppressing dissipative heat transfer is insufficient in the container.
The present invention is described under the background. The object of the present invention is to provide a container for accommodating a liquid which can suppress a dissipative heat loss.
Accordingly, a mode of the present invention may provide a container which can accommodate an object inside an internal space shaped by an inner surface of the container, wherein the inner surface substantially has shapes of a sphere, a semiregular polyhedron or a dual polyhedron of a semiregular polyhedron, and the inner surfaces are formed by a plurality of segmented members made of a refractory material.
The refractory material of the container may be a refractory metal or a refractory alloy.
Another mode of the present invention may provide a container which can accommodate an object inside an internal space shaped by an inner surface, wherein the inner surface substantially has a shape of sphere, a semiregular polyhedron, or a dual polyhedron of semiregular polyhedron, and the inner surface is formed by a plurality of segmented members made of a ceramic.
It is preferable in the container to cause a value of S/V (m) to be lower than 7.7 m−1 wherein a value of S/V (m) is lower than 7.7 m−1 where a volume of the internal space is V (m3) and a surface area of the inner surface is S (m2).
The semiregular polyhedron may be substantially configured by a combination of an equilateral triangle and an equilateral pentagon.
The dual polyhedron of the semiregular polyhedron may be a pentagonal hexecontahedron, a deltoidal hexecontahedron, or a hexakis icosahedron.
The segmented members may have a first main surface of a curved face and a second main surface of a curved face, the first and second main surfaces being substantially parallel each other.
The segmented members may have a cavity.
The ceramic forming the segmented member may be made of one or more materials selected from a group of aluminum titanate silicon nitride, cordierite, spodumene, alumina, silicon carbide, zirconia, sialon, mullite, and boron compound.
The ceramic forming the segmented member may be a refractory brick including one or more materials selected from a group of alumina, magnesia, chromia, silica, and calcia.
A first inorganic filler may be set between the segmented members in the container.
A sheet material including an inorganic fiber may be provided between the segmented members of the container.
The inorganic fiber included in the sheet member may include alumina.
The container of the present invention further includes a casing covering the inner surface, and a second inorganic filler may be supplied between the casing and the inner surface.
The container further includes a casing surrounding the segmented member, and a sheet material including the inorganic fiber may be installed between the casing and the segmented member.
Alumina may be contained in the inorganic fiber of the sheet material.
The container may be used to accommodate the molten metal.
A material different from a material forming the segmented member may be installed on at least one surface of the segmented members in the container.
A ceramic may be installed on at least one surface of the refractory materials in the container.
The internal space may be a space substantially hermetically-closed in the container.
In the container, an introduction spout for introducing an object into the internal space and a discharge spout for discharging the object from the internal space may be the same.
According to the present invention, it is possible to provide a container for accommodating a liquid which can suppress a dissipative heat loss.
A description is given below, with reference to
The container 100 has a casing 105 formed by a metal such as stainless steel. Plural segment members 110 to be described in detail later are arranged on an inside of the casing. An inner surface 130 of the container 100 is formed by the segmented members 110. The inner surface 130 of the container 100 forms the internal space 135 of the container and is directly in contact with molten metal accommodated in the container 100. The casing 105 is not directly in contact with the molten metal because of the existence of the segmented members 110 and the inorganic filler 107. The segmented members 110 may be made of a ceramic. Alternatively, the segmented members 110 may be formed by a refractory metal, a refractory alloy, or the like.
In the present invention, the terminology “ceramic” is a broad concept including all inorganic materials excluding metallic materials and organic materials; said differently, fine ceramics, composite materials including inorganic materials, refractory brick and so on.
Although it is not illustrated in figures, another coating such as an inorganic fiber coating may be provided between the casing 105 and the inorganic filler 107 and/or between the inorganic filler 107 and the segmented member 110. However, a description of the coating is omitted because the coating is known.
As a feature which is not essential for the present invention, the container 100 includes a top lid 150. The molten metal can be supplied in an internal space 135 of the container 100 by opening the top lid 150. The top lid 150 is formed by a casing 105, an inorganic filler 107 and a segmented member 110 in a manner similar to other parts of the container 100. The top lid 150 can be freely opened and closed by, for example, a known hinge mechanism 152. When the top lid is closed, the internal space 135 is hermetically closed. Said differently, when the top lid 150 is closed, the inner surface 130 of the container is continuously formed. A discharge spout 160 is provided at an appropriate portion of the container 100 to enable outwardly ejecting the molten metal. Referring to
The container 100 has a feature in which the inner surface 130 of the container 100 has a relatively small surface area in comparison with the volume of the container 100.
Generally speaking, the following relationship may be established between a surface area of a member in contact with a heat source (high temperature fluid) and a heat quantity (amount of heat transmission) which is transmitted via the member.
Q=hA(θf−θw) (1)
, where Q designates the amount of heat transmission, A designates the surface area of the member, θw designates the temperature of the member, and θf designates the temperature of the heat source (high temperature fluid). Further, h designates the coefficient of heat transfer, the unit of which is W/m2·K(kcal/m·h·° C.). It is possible to know that the smaller the surface area A of the member, the smaller the amount of heat transmission Q.
The inventors of the present invention have found that this principle can be used in forming the container 100. According to the present invention, it becomes possible to significantly restrict dissipation loss in the container in comparison with a conventional container. As described later, in comparison with the conventional container having a similar volume, the inner surface area 130 of the container of the present invention may have a smaller surface area.
In order to form the inner surface 130 of the container having the small surface area, plural segmented members 110 are put together to cause the inner surface to be shaped substantially like a sphere, a semiregular polyhedron, or a dual polyhedron of a semiregular polyhedron. These shapes are adopted to reduce the surface area relative to the volume of the container. The reason for using the plural segmented members 110 instead of a single member for forming the inner surface 130 is to avoid extreme difficulty in manufacturing the member having a complicated surface with a single ceramic. Even if it is possible to manufacture with the single ceramic, a manufacturing cost for this becomes extremely high.
The “semiregular polyhedron” is ordinarily called “Archimedean solid”. The surfaces of the “Archimedean solid” are formed by plural types of semiregular polyhedrons having the same structure of vertices (totally 13 types). The “semiregular polyhedron” is a “snub dodecahedron” formed by putting together equilateral pentagons (twelve faces) and equilateral triangle (eighty faces) as the faces of the “semiregular polyhedron”, a “truncated icosahedron” (so-called soccer ball shape) formed by putting together equilateral pentagons (twelve faces) and regular hexagons (twenty faces) as the faces of the “semiregular polyhedron”, or the like. The “dual polyhedron of semiregular polyhedron” is called “Archimedean dual”, which is geometry formed by changing between the number of the vertices of the semiregular polyhedron and the number of the faces of the semiregular polyhedron. For example, “Archimedean dual” is a hexakis icosahedron (dual polyhedron of rhombitruncated icosidodecahedron), a deltoidal hexecontahedron (dual polyhedron of rhombicosidodecahedron), and a pentagonal hexecontahedron (dual polyhedron of snub dodecahedron) (See “Solving regular polyhedrons” by Hitotsumatsu Shin, Tokai University Press, in more detail).
Hereinafter, an example of the shape of the segmented member forming the inner surface 130 of the container 100 is described in detail.
As illustrated in
The main surfaces 11a and 112a do not necessarily have the curved shapes and may have flat shapes. It is significant that the main surface, especially the main surface 112a, has the curved face as illustrated in
By lengthwise and crosswise arranging as many as sixty of these segmented members 110a, it is possible to form the inner surface 130 of the container having a substantially sphere-like surface. When the main surfaces 111a and 112a of the segmented members 110a have flat faces which are not curved faces, the inner surface 130 of the container is formed to be a substantial pentagonal hexecontahedron as illustrated in
A sheet material including inorganic fiber may be provided in gaps between the casing 105 and the segmented members 110a and/or gaps among the segmented members 110a in place of the inorganic filler 107. The sheet material including the inorganic fiber is generally bulky and flexible. Therefore, when this sheet material is used, the segmented member 110a can be mechanically in contact with or engaged with the seat member by pressing the segmented member 110a on the seat member. When the segmented member 110a is broken, the broken segmented member can be easily removed by drawing the broken segmented member out from the seat member. Therefore, it becomes possible to change the segmented member more easily in comparison with a case of using the inorganic filler 107 in the gaps. When sufficient adhesiveness is not obtainable while the segmented member 110a is being pressed on the seat member, an inorganic adhesive may be used between the segmented member 110a and the seat member.
The material of the inorganic fiber contained in the seat member is not specifically limited and may be alumina, silica or a mixture of these. The mode of the seat member is not specifically limited and May be various such as a mode of mat formed by an inorganic fiber and a mode of unwoven fabric.
The shape of the segmented member used for forming the inner surface 130 is not limited to those illustrated in
Referring to
Referring to
Referring to
As described, in the present invention, by putting together plural segments, it is possible to form the container substantially having the inner surfaces of the sphere, the semiregular polyhedron, and the dual polyhedron of semiregular polyhedron.
Hereinafter, reviewed is a relationship between the volume V of the inner spaces and the surface area S of the inner surfaces of a container having a cylindrical inner surface (hereinafter, simply referred to as a cylindrical container) and a container having an inner surface which is shaped substantially like a sphere, a semiregular polyhedron, and a dual polyhedron of semiregular polyhedron (hereinafter, simply referred to as a spherical container).
For example, a container which can accommodate molten metal of about 1 ton inside the internal space of the container is examplified. In this case, the necessary volume V of the internal space is about 0.37 m3 because the specific gravity of aluminum is about 2.7 g/cm3.
In case of the “cylindrical container”, if the volume of the internal space is constantly V (0.37 m3), the surface area S1 changes along with changes of the radius r1 and the height H of the circle on the bottom surface of the “cylindrical container”. When the radius r1 of the circle on the bottom surface of the “cylindrical container” is changed, the heights H are determined respectively for the radii r1 of the circle, and the surface areas S1 are determined for the radii r1.
Referring to
Referring to
Change rate P(%)={(S1−S2)/S1}×100
Referring to
As described, in the container of the present invention, the inner surface is substantially formed to be a sphere, a semiregular polyhedron or a dual polyhedron of a semiregular polyhedron. Therefore, it is possible to significantly restrict a dissipative heat loss from the container.
It is preferable that the segmented members 110 made of ceramic have a cavity.
Ordinarily, a thermal flux q flowing from one space (e.g. internal space) to the other space (e.g. external space) via a wall composed of plural members 1, 2, . . . , i is represented by the following formula.
, where θf1 designates a temperature of an internal space and θf2 designates a temperature of an external space.
Here, an inverse number of k is called thermal resistance. Further, h1 designates a coefficient of heat transfer of an internal space of the wall, h2 designates a coefficient of heat transfer of an external space of the wall, δi designates the thicknesses of coatings forming the wall constituted by plural members, and λi designates the thermal conductivities of the coatings.
Next, a case where the wall is formed by only the ceramic member (e.g. silicon nitride) and a case where the wall has two layered structure including the ceramic member (e.g. silicon nitride) and an air coating is considered. The thermal conductivity λ of air is about 0.03 W/m·K and the thermal conductivity λ of silicon nitride is about 30 W/m·K. Therefore, referring to Formula (2) and Formula (3), when the wall has the two-layered structure, k becomes even smaller in comparison with a case where the wall has the single coating of ceramic. Therefore, by providing the air coating, the thermal flux q becomes even smaller and the thermal resistance of the wall is improved.
Therefore, in the present invention, when the segmented member 110 made of ceramic has a cavity, it becomes possible to further restrict dissipative heat loss from the container. When the segmented member 110 having the cavity is used, it is possible to restrict the entire weight of the container. Therefore, handling and delivery of the container becomes easy to thereby more easily carry out the delivery. Air may be supplied in the cavities of the segmented members. The cavity may be instead depressurized or evacuated as practiced by one ordinarily skilled in art.
The segmented member may be preferably formed by a chemically stable material when the segmented member is in contact with molten metal. With this, it is possible to restrict a problem that the quality of the molten metal is degraded by impurities mixed into the molten metal with a cross reaction between the molten metal and the segmented member. Further, it is possible to diminish a problem such as breakage of the container caused by chemical deterioration.
When the above segmented member has the cavity, the wall thickness of the member is preferably as thin as possible from a viewpoint of thermal shock resistance.
For example, when the strength of a material is σf and thermal stress is σth, destruction caused by the thermal stress occurs when a relationship of σf=σth is established. Therefore, a critical temperature difference ΔTc at which the material can endure may be determined by the following formula.
, where ν designates a Poisson's ratio, E designates a Young's modulus, α designates a coefficient of thermal expansion, and β designates a Blot coefficient. The blot coefficient is a dimensionless number expressed by the following formula (5), where λ designates the thermal conductivity of the material, δ designates the thickness of the material, and h designates the coefficient of heat transfer.
β=Δh/λ (5)
It is known from the formula (5) that the smaller thickness of the material is, the smaller β is and the larger ΔTc is.
On the other hand, extreme thinning of the wall of the segmented member having the cavity may cause a problem because the mechanical strength of the segmented member is lowered. Therefore, in a case of the segmented member having the cavity, the wall thickness may be preferably in a range of about 1 mm to 10 mm, more preferably about 3 mm to 8 mm.
The ceramic material of the segmented member may be aluminum titanate, silicon nitride, cordierite, spodumene, alumina, silicon carbide, zirconia, sialon, mullite, and boron compound (hereinafter, these ceramics are referred to as “ceramic of non-refractory brick”). Especially, because aluminium titanate and silicon nitride are stable to an aluminum molten metal, it is preferable to use aluminium titanate or silicon nitride when the container is used for accommodating the aluminum molten metal.
The ceramic material forming the segmented member may be a refractory brick including one or more materials selected from a group of alumina, magnesia, chromia, silica, and calcia. However, even when the refractory brick is used, it is preferable to use “ceramic of non-refractory brick” for at least the main surface forming the inner surface 130 of the container. Generally speaking, a refractory brick has low strength and is apt to produce a partial crack. However, by employing the above structure of using “ceramic of non-refractory brick” for at least the main surface forming the inner surface 130, the strength of the segmented member becomes high and it is possible to avoid contamination of a liquid accommodated in the internal space of the container.
Further, when the segmented member is made of a metal or an alloy, the material of the segmented member may be an alloy containing Cr and/or Ni such as stainless steel (SUS304, SUS316(L), SUS310S or the like), nickel-based alloy, or the like. In the case of using the segmented member made of the metal or the alloy, in order to restrict a cross reaction between the segmented member and an object such as a liquid accommodated inside the container, it is preferable to install the “ceramic of non-refractory brick” on at least the main surface 112a forming the inner surface 130 of the container.
The above description has not described well other members forming the container, such as the casing 105 and the inorganic filler 107. However, these members are obviously used in various modes. For example, the outer shape of the casing is not limited to a sphere shape illustrated in
However, in the second container 1000, a discharge spout corresponding to the discharge spout 160 of
In comparison with the container having the discharge spout 160 illustrated in
In the second container 1000, the inorganic filler 1007 may be replaced by a sheet material including an inorganic fiber as described above.
Next, the effects of the embodiments of the present invention are described in detail.
A silicon nitride powder (the average particle diameter of about 1 μm), an alumina powder (the average particle diameter of about 1 μm) and an yttria powder (the average particle diameter of about 1 μm) were measured to have a weight ratio of 92:3:5, and these powders were sufficiently mixed. Acrylic binder of 0.5 wt % for the weight of the mixed powders and water of 140 wt % for the weight of the mixed powders (without the acrylic binder) were mixed with the mixed powders. These mixed powders, acrylic binder, and water were mixed by a ball mill.
The obtained slurry was poured into a gypsum mold. The gypsum mold had a top lid and an inner surface of an upper, lower, right and left surfaces were determined so that molded bodies having shapes illustrated in
After drying the molded body, the molded body was burned for 3 hours at a maximum temperature of 1800° C. under a nitrogen atmosphere of 0.93 MPa. Thus, the segmented member having a shape illustrated in
When the obtained segmented members were observed by eyes, there was no abnormality such as a crack.
An aluminum titanate powder (the average particle diameter of about 1 μm), an acrylic binder of 1 wt % for the weight of the powder, and water of 160 wt % for the weight of the powder (without the acrylic binder) were mixed by a ball mill. The obtained slurry was poured into a gypsum mold. With this process, a molded body having a cavity was obtained.
After drying the molded body, the molded body was burned for 2 hours at a maximum temperature of 1400° C. under an air atmosphere. Thus, a sintered compact was obtained. The dimensions of the sides are similar to those in Embodiment 1. A sample having a thickness of 1 mm and a diameter of 10 mm was cut out from the sintered compact. This sample was used to determine its thermal conductivity by using a laser flash measurement (measuring, equipment: TC-7000 manufactured by ULVAC-RIKO Inc.) It was known that the thermal conductivity of the sample is about 1 W/m·k which was sufficiently small. As a result of the experiment, the sample is hardly wetted by an aluminum molten metal.
A silicon nitride powder (the average particle diameter of about 1 μm), an acrylic binder of 1 wt % for the weight of the powder, and water of 160 wt % for the weight of the powder were mixed by a ball mill. A molded body was formed from the obtained slurry by a method described in Embodiment 1. After drying the molded body, the molded body was burned for 5 hours at a maximum temperature of 1400° C. under a nitrogen atmosphere. Thus, the segmented member having a shape illustrated in
An alumina powder AL-160SG4 (the average particle diameter of about 1 μm) of a weight of 100, a dispersed material A6114 of a weight of 0.75, and water of a weight of 160 were mixed. An acrylic binder of 1 wt % was added to the above mixture. After mixing with a ball mill for 16 hours, a process of ejecting bubbles was applied to the mixture. A molded body was formed using the obtained slurry in a similar manner to that of Embodiment 1. After drying the molded body, the molded body burned for 2 hours at a maximum temperature of 1600° C. under a nitrogen atmosphere. Thus, the segmented member having a shape illustrated in
Segmented members are made of sialon, silicon carbide, silica, cordierite, spodumene, and boron nitride respectively with a similar manner to the above. All these segmented members were wetted by an aluminum molten metal to thereby prove chemical stability of the these segmented members to the aluminum molten metal.
A container having a substantially spherical shape was made. An outside of the container (i.e. casing) was made of stainless steel (SUS304) having a thickness of 8 mm. The casing was made of two pieces. The dimensions of the assembled stainless steel casing are 940 mm in the outer diameter and 924 mm in the inner diameter. Inside the casing, the segmented members made of the silicon nitride obtained in Embodiment 1 were arranged by interposing an inorganic filler (castable material) having a major component of alumina-silica in a shape illustrated in
In a similar manner to Embodiment 5, a container having a substantially spherical shape was made. With Embodiment 6, the segmented members made of aluminium titanate according to Embodiment 2 were used.
An alumina brick (CWK-3 manufactured by AGC Ceramics Co., Ltd.) mainly made of a commercially available electro-fused material of corundum mullite type was cut and processed to manufacture the segmented member having the shape illustrated in
A sample having a thickness of 1 mm and a diameter of 10 mm is cut out from the alumina brick. This sample is used to determine the thermal conductivity by using a laser flash measurement (measuring equipment: TC-7000 manufactured by ULVAC-RIKO Inc.). The thermal conductivity of the sample is about 1.2 W/m·K.
A magnesia-chrome brick (NSX-750 manufactured by AGC Ceramics Co., Ltd.) was cut and processed to manufacture the segmented member having the shape illustrated in
A sample having a thickness of 1 mm and a diameter of 10 mm was cut out from the magnesia-chrome brick. This sample was used to determine the thermal conductivity by using a laser flash measurement (measuring equipment: TC-7000 manufactured by ULVAC-RIKO Inc.) The thermal conductivity of the sample is about 1.0 W/m·K.
After pouring an alumina cement into a gypsum mold, the alumina cement was solidified at room temperature to thereby form the segmented member having the shape illustrated in
A commercially available FeCrNi alloy 32Cr-43Ni (KHR45A manufactured by Kubota Corporation) was cut and processed to make the segmented member having the shape illustrated in
In a similar manner to Embodiment 5, a container having a substantially spherical shape was made. With Embodiment 11, the segmented members made of aluminium titanate according to Embodiment 7 were used.
In a similar manner to Embodiment 5, a container having a substantially spherical shape was made. With Embodiment 12, the segmented members made of alumina cement using the plate made of silicon nitride according to Embodiment 9 were used.
In a similar manner to Embodiment 5, a container having a substantially spherical shape was made. With Embodiment 13, the segmented members made of alumina cement using the plate made of silicon nitride according to Embodiment 10 were used.
A container having a cylindrical internal space was made. A schematic cross-sectional view is illustrated in
The thermal resistance of the containers of Embodiments 5 and 6 and Comparative Example 1 were evaluated. The evaluation was done by measuring the temperatures of corresponding aluminum molten metal materials after a passage of a predetermined time (one hour) from a state in which the aluminum molten metal materials having an initial temperature of 750° C. of about one ton are poured into internal spaces of the containers and the internal spaces are hermetically closed. The results are illustrated in Table 1.
From Table 1, it is known that the temperature of the molten metal material in the container of Comparative Example 1 decreases down to 675° C. after one hour. In comparison, the temperatures of the aluminum molten metal materials in the containers of Embodiments 5 and 6 are maintained to be 722° C. and 734° C., respectively. It was confirmed that dissipative heat loss is significantly restricted in comparison with the conventional container.
Table 2 illustrates evaluation results of the thermal resistance of the containers of Embodiments 11, 12 and 13. In a similar manner to the above, the evaluation was done by measuring the temperature of aluminum molten metal materials after a passage of a predetermined time (one hour) from a state in which the aluminum molten metal materials having an initial temperature of 750° C. of about one ton were poured into internal spaces of the containers and the internal spaces were hermetically closed.
In comparison, the temperatures of the aluminum molten metal materials in the containers of Embodiments 11 and 13 are maintained to be within a range of between 708° C. and 721° C. It is confirmed that dissipative heat loss is significantly restricted in comparison with the conventional container.
The present invention may be applicable to a container for accommodating a metal such as aluminum, magnesium, and zinc and alloys of these metals. The present invention is applicable to not only the molten metal but also a container for accommodating a high temperature powder, pellets or the like.
This patent application is based on Japanese Priority Patent Application No. 2008-214409 filed on Aug. 22, 2008, the entire contents of which are hereby incorporated herein by reference.
Number | Date | Country | Kind |
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2008-214409 | Aug 2008 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2009/061213 | 6/19/2009 | WO | 00 | 2/2/2011 |