Solid containing metal, method for producing solid containing metal, method for melting metal, and method for producing cast metal

Abstract

Provided is a solid containing a metal, the solid having a fusion-bonded portion of the metal and a diffusion-bonded portion of the metal in a cross section. Provided is a solid containing a metal, the solid having a high-density layer with a small number of voids on the surface side in a cross-section, and a low-density layer with a large number of voids surrounded by the high-density layer in the cross-section.

Description

Metal-containing solid, method for manufacturing metal-containing solid, method for melting metal, and method for manufacturing metal casting

[0001] The present invention relates to a metal-containing solid, a method for producing a metal-containing solid, a method for melting a metal, and a method for producing a metal casting.

[0002] There is a demand for metal solids that have structures and mechanical properties suited to their intended use.

[0003] International Publication No. 2022 / 196681

[0004] An object of the present invention is to provide a metallic solid having a novel structure.

[0005] [1] A solid containing a metal, the solid having a fusion bonded portion of the metal and a diffusion bonded portion of the metal in cross section.

[0006] [2] The solid according to [1], having a portion where different crystal structures are separated at at least one of a fusion bonded portion and a diffusion bonded portion.

[0007] [3] The solid according to [1] or [2], wherein the area surrounded by at least one of the fusion bonded portion and the diffusion bonded portion contains metal crystal grains.

[0008] [4] The solid according to any one of [1] to [3], wherein the region surrounded by at least one of the fusion bonded portion and the diffusion bonded portion contains columnar crystals of metal.

[0009] [5] The solid according to any one of [1] to [4], wherein the region surrounded by at least one of the fusion bonded portion and the diffusion bonded portion contains equiaxed crystals of the metal.

[0010] [6] The solid according to [5], wherein the equiaxed crystal has at least one of a dendritic structure and a eutectic structure.

[0011] [7] The solid according to any one of [1] to [6], wherein the region surrounded by at least one of the fusion bonded portion and the diffusion bonded portion includes at least two selected from a region containing metal crystal grains, a region containing metal columnar crystals, and a region containing metal equiaxed crystals.

[0012] [8] The solid according to [7], wherein the equiaxed crystal has at least one of a dendritic structure and a eutectic structure.

[0013] [9] A solid according to any one of [1] to [8], having a eutectic structure of metal in the fusion joint.

[0014]

[10] The solid according to any one of [1] to [9], wherein the interface is not connected to other interfaces in the fusion joint.

[0015]

[11] The solid according to any one of [1] to

[10] , having an interface at the diffusion bonded portion.

[0016]

[12] The solid according to any one of [1] to

[11] , having voids in the diffusion bonded portion.

[0017]

[13] The solid according to any one of [1] to

[12] , wherein the metal comprises a plurality of metal species.

[0018]

[14] The solid according to any one of [1] to

[13] , wherein at least one of the fusion bonded portion and the diffusion bonded portion is free of oxides.

[0019]

[15] The solid according to any one of [1] to

[13] , wherein an oxide is present in at least one of the fusion bonded portion and the diffusion bonded portion.

[0020]

[16] The solid according to any one of [1] to

[15] , wherein at least one of the fusion bonded portion and the diffusion bonded portion is free of oil.

[0021]

[17] The solid according to any one of [1] to

[15] , wherein oil is present in at least one of the fusion bonded portion and the diffusion bonded portion.

[0022]

[18] The solid according to any one of [1] to

[17] , wherein at least one of the fusion bonded portion and the diffusion bonded portion does not contain a release agent.

[0023]

[19] The solid according to any one of [1] to

[17] , wherein a release agent is present in at least one of the fusion bonded portion and the diffusion bonded portion.

[0024]

[20] The solid according to any one of [1] to

[19] , further having a tight bond in the cross section that is different from the fusion bond and the diffusion bond.

[0025]

[21] The solid according to any one of [1] to

[20] , which is porous.

[0026]

[22] The solid according to any one of [1] to

[21] , which is flexible.

[0027]

[23] The solid according to any one of [1] to

[22] , further comprising a non-metal.

[0028]

[24] The solid according to any one of [1] to

[23] , wherein the solid does not have an oxide film on the surface thereof.

[0029]

[25] The solid according to any one of [1] to

[24] for dissolving in a molten metal.

[0030]

[26] A solid containing a metal, the solid having a high-density layer with few voids on the surface side in a cross section, and a low-density layer with many voids surrounded by the high-density layer in a cross section, wherein the metal may be aluminum.

[0031]

[27] The solid according to

[26] , having a metal fusion bond and a metal diffusion bond in cross section.

[0032]

[28] The solid according to

[26] or

[27] , which is porous.

[0033]

[29] The solid according to any one of

[26] to

[28] , which is flexible.

[0034]

[30] The solid according to any one of

[26] to

[29] , which does not have an oxide film on the surface of the solid.

[0035]

[31] The solid according to any one of

[26] to

[30] for dissolving in a molten metal.

[0036]

[32] A method for producing a metal-containing solid, comprising irradiating a plurality of metal materials with microwaves to form a metal-containing solid, the metal-containing solid having a fused metal joint and a diffusion metal joint in a cross section. The metal-containing solid may be the solid described in any one of [1] to

[31] .

[0037]

[33] The method for producing a metal-containing solid according to

[32] , wherein each of the plurality of metal materials has one of two or more different crystal structures.

[0038]

[34] A method for producing a metal-containing solid according to

[32] or

[33] , in which oxides contained in a plurality of metal materials are reduced by irradiating the metal materials with microwaves.

[0039]

[35] A method for producing a metal-containing solid according to any one of

[32] to

[34] , which comprises irradiating a plurality of metal materials with microwaves to reduce non-metals mixed with the plurality of metal materials.

[0040]

[36] A method for melting a metal, comprising: preparing a metal-containing solid having a metal fusion-bonded portion and a metal diffusion-bonded portion in a cross section; and dissolving the metal-containing solid in a molten metal. The metal-containing solid may be the solid described in any one of [1] to

[31] .

[0041]

[37] The method for dissolving a metal according to

[36] , wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

[0042]

[38] A method for melting metals according to

[37] , wherein each of the plurality of metal materials has one of two or more different crystal structures.

[0043]

[39] A method for dissolving metals according to

[37] or

[38] , in which oxides contained in a plurality of metal materials are reduced by irradiating the metal materials with microwaves.

[0044]

[40] A method for melting metals according to any one of

[37] to

[39] , in which non-metals mixed with a plurality of metal materials are reduced by irradiating the plurality of metal materials with microwaves.

[0045]

[41] The method for melting a metal according to any one of

[36] to

[40] , further comprising heating the metal-containing solid at a temperature lower than the melting point of the metal before dissolving the metal-containing solid in the molten metal.

[0046]

[42] A method for melting a metal, comprising: preparing a metal-containing solid, the metal-containing solid having a high-density layer with few voids on the surface side in a cross section, and a low-density layer with many voids surrounded by the high-density layer in a cross section; and dissolving the metal-containing solid in a molten metal. The metal-containing solid may be a solid according to any one of [1] to

[31] .

[0047]

[43] The method for dissolving a metal according to

[42] , wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

[0048]

[44] A method for melting metals according to

[43] , wherein each of the plurality of metal materials has one of two or more different crystal structures.

[0049]

[45] A method for dissolving metals according to

[43] or

[44] , in which oxides contained in a plurality of metal materials are reduced by irradiating the metal materials with microwaves.

[0050]

[46] A method for melting metals according to any one of

[43] to

[45] , in which non-metals mixed with a plurality of metal materials are reduced by irradiating the plurality of metal materials with microwaves.

[0051]

[47] The method for melting a metal according to any one of

[42] to

[46] , further comprising heating the metal-containing solid at a temperature lower than the melting point of the metal before dissolving the metal-containing solid in the molten metal.

[0052]

[48] ​​A method for manufacturing a metal casting, comprising: preparing a metal-containing solid, the metal-containing solid having a metal fusion bonded portion and a metal diffusion bonded portion in a cross section; dissolving the metal-containing solid in a molten metal; pouring the molten metal containing the metal-containing solid into a mold; and solidifying the molten metal in the mold.

[0053]

[49] The method for producing a metal casting according to

[48] , wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

[0054]

[50] A method for producing a metal casting according to

[49] , wherein each of the plurality of metal materials has one of two or more different crystal structures.

[0055]

[51] A method for producing a metal casting according to

[49] or

[50] , in which oxides contained in a plurality of metal materials are reduced by irradiating the metal materials with microwaves.

[0056]

[52] A method for manufacturing a metal casting according to any one of

[49] to

[51] , in which non-metals mixed with a plurality of metal materials are reduced by irradiating the plurality of metal materials with microwaves.

[0057]

[53] The method for producing a metal casting according to any one of

[48] to

[52] , further comprising heating the metal-containing solid at a temperature lower than the melting point of the metal before dissolving the metal-containing solid in the molten metal.

[0058]

[54] A method for manufacturing a metal casting, comprising: preparing a metal-containing solid, the metal-containing solid having a high-density layer with few voids on the surface side in a cross section, and a low-density layer with many voids surrounded by the high-density layer in a cross section; dissolving the metal-containing solid in molten metal; pouring the molten metal containing the dissolved metal into a mold; and solidifying the molten metal in the mold.

[0059]

[55] The method for producing a metal casting according to

[54] , wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

[0060]

[56] A method for producing a metal casting according to

[55] , wherein each of the plurality of metal materials has one of two or more different crystal structures.

[0061]

[57] A method for producing a metal casting according to

[55] or

[56] , in which oxides contained in a plurality of metal materials are reduced by irradiating the metal materials with microwaves.

[0062]

[58] A method for manufacturing a metal casting according to any one of

[55] to

[57] , in which non-metals mixed with a plurality of metal materials are reduced by irradiating the plurality of metal materials with microwaves.

[0063]

[59] The method for producing a metal casting according to any one of

[54] to

[58] , further comprising heating the metal-containing solid at a temperature lower than the melting point of the metal before dissolving the metal-containing solid in the molten metal.

[0064] According to the present invention, it is possible to provide a metallic solid having a novel structure.

[0065] FIG. 1 is a cross-sectional micrograph of an A6061 metal solid according to Example 1. FIG. 2 is a cross-sectional micrograph of an ADC12 metal solid according to Example 2. FIG. 3 is a cross-sectional micrograph of an oxygen-free copper metal solid according to Example 3. FIG. 4 is a cross-sectional micrograph of an ADC12 ingot according to Comparative Example 1. FIG. 5 is a cross-sectional micrograph of a metal solid according to Example 4 and Comparative Example 2. FIG. 6 is a cross-sectional SEM photograph of a metal solid according to Example 4 and Comparative Example 2. FIG. 7 is a graph showing the results of SEM-EDX analysis of a metal solid according to Example 4 and Comparative Example 2. FIG. 8 is a CT scan image of a metal solid according to Example 4 and Comparative Example 2. FIG. 9 is a photograph showing a compression test of a metal solid according to Example 5 and Comparative Examples 3 and 4. FIG. 10 is a graph showing the results of a compression test of a metal solid according to Example 5 and Comparative Examples 3 and 4. FIG. 11 is a photograph showing a load test of a metal solid according to Example 5 and Comparative Example 3. FIG. 12 is a photograph showing a load test of a metal solid according to Example 5 and Comparative Example 3. Fig. 13 is a photograph of the metallic solids according to Example 5 and Comparative Example 3 when they are poured into molten metal. Fig. 14 is a photograph of the metallic solid according to Comparative Example 5 when it is poured into molten metal. Fig. 15 is a photograph of the metallic solid according to Example 7. Fig. 16 is a photograph of a cross section of the metallic solid according to Example 7. Fig. 17 is a photograph of a cross section of the metallic solid according to Example 8. Fig. 18 is a conceptual diagram of another embodiment.

[0066] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the drawings are schematic. Therefore, specific dimensions and the like should be determined in light of the following description. Furthermore, it goes without saying that the dimensional relationships and ratios between the drawings may differ.

[0067] A metal-containing solid according to an embodiment has a metal fusion bonded portion and a metal diffusion bonded portion in a cross section. The metal-containing solid according to an embodiment also has a high-density layer with few voids on the surface side in the cross section, and a low-density layer with many voids surrounded by the high-density layer in the cross section. The metal-containing solid according to an embodiment also has a metal fusion bonded portion and a metal diffusion bonded portion in the cross section, and also has a high-density layer with few voids on the surface side in the cross section, and a low-density layer with many voids surrounded by the high-density layer in the cross section.

[0068] The metal-containing solid according to the embodiment is produced, for example, by irradiating a plurality of metal materials with microwaves to heat the plurality of metal materials and sintering or melting and solidifying the plurality of metal materials. The microwaves are, for example, electromagnetic waves with a frequency of 300 MHz or more and 30 GHz or less. The temperature of the entire metal heated by the microwaves is not limited, but is, for example, below the melting point of the metal. However, the surface of the metal material may be locally heated to a temperature above the melting point.

[0069] The shape and size of the metal material are not limited. The metal material is, for example, a metal piece. The metal piece may be, for example, a metal slice, a metal fragment, a metal chip, a metal shavings, or a metal powder. The multiple metal materials may be a mixture of multiple large metal materials and multiple small metal materials. When the metal material is large, the voids in the produced solid tend to be large. When the metal material is small, the voids in the produced solid tend to be small. Therefore, by adjusting the size of the metal material, it is possible to adjust the size of the voids in the produced solid.

[0070] The metal materials irradiated with microwaves may be in the form of a molded body. For example, a molded body made of the metal materials may be produced by filling a mold with the metal materials and applying pressure to the metal materials. The molded body may be a briquette. The molded body may be disk-shaped, but is not limited to this. The molded body may be coil-shaped. The pressure applied to the metal materials is not limited to, but is, for example, 1 MPa or more, 100 MPa or more, or 200 MPa or more, and 2000 MPa or less, 1900 MPa or less, or 1800 MPa or less. By applying pressure, the produced metal solid tends to become dense. Examples of pressurizing methods include uniaxial molding, cold isostatic pressing (CIP) molding, hot isostatic pressing (HIP) molding, and roller pressing.

[0071] The metal material may include an elemental metal or a metal compound such as an alloy. The metal may be a conductive metal, a magnetic metal, or a metal that absorbs microwaves. Examples of metals include iron (Fe), nickel (Ni), copper (Cu), gold (Au), silver (Ag), aluminum (Al), cobalt (Co), tungsten (W), titanium (Ti), chromium (Cr), molybdenum (Mo), beryllium (Be), magnesium (Mg), tin (Sn), cerium (Ce), lead (Pb), mercury (Hg), sodium (Na), bismuth (Bi), gallium (Ga), lithium (Li), zinc (Zn), silicon (Si), niobium (Nb), and scandium (Sc).

[0072] The sintering temperature of iron (Fe) is, for example, 1200°C. The melting point of iron (Fe) is 1538°C. The sintering temperature of nickel (Ni) is, for example, 1200°C. The melting point of nickel (Ni) is 1495°C. The sintering temperature of copper (Cu) is, for example, 800°C. The melting point of copper (Cu) is 1085°C. The sintering temperature of gold (Au) is, for example, 800°C. The melting point of gold (Au) is 1064°C. The sintering temperature of silver (Ag) is, for example, 750°C. The melting point of silver (Ag) is 962°C. The sintering temperature of aluminum (Al) is, for example, 500°C. The melting point of aluminum (Al) is 660°C. The sintering temperature of cobalt (Co) is, for example, 1100°C. The melting point of cobalt (Co) is 1455°C.

[0073] The metallic material may contain one type of metal or multiple types of metals. Examples of metal compounds include, but are not limited to, alloys of multiple metal elements, alloys of metal elements and non-metal elements, metal oxides, metal hydroxides, metal chlorides, metal carbides, metal borides, and metal sulfides. The metallic material may contain, as alloy components, for example, silicon (Si), manganese (Mn), chromium (Cr), nickel (Ni), carbon (C), boron (B), copper (Cu), aluminum (Al), titanium (Ti), niobium (Nb), vanadium (V), zinc (Zn), antimony (Sb), palladium (Pd), lanthanum (La), gold (Au), potassium (K), cadmium (Cd), indium (In), molybdenum (Mo), and sulfur (S).

[0074] Each of the multiple metallic materials may have one of two or more different crystalline structures. The multiple metallic materials may be a mixture of metallic materials with different crystalline structures. For example, the metallic material may be obtained by cutting a die-cast casting. The die-cast casting has a chill layer consisting of fine crystal grains, a columnar crystal zone consisting of elongated columnar crystals, and an equiaxed crystal zone consisting of equiaxed crystals with isotropic crystal grain orientation. The equiaxed crystals may have at least one of a dendritic structure and a eutectic structure. Therefore, metallic materials may include metallic materials having fine crystal grains derived from the chill layer as a crystalline structure, metallic materials having columnar crystals derived from the columnar crystal zone as a crystalline structure, and metallic materials having equiaxed crystals derived from the equiaxed crystal zone as a crystalline structure. When a metallic material is irradiated with microwaves, the surface vicinity is heated preferentially over the interior. Therefore, even when a metallic material is irradiated with microwaves, the crystalline structure within the metallic material tends to be maintained. However, when a metallic material is irradiated with strong microwaves, the metallic material may recrystallize.

[0075] The metal material may be mixed with non-metals such as a mold release agent, coolant, oil, and water. In this disclosure, "mixing" includes adhesion due to mixing and adjacent materials without adhesion due to mixing. In this disclosure, "mixing" also includes a state in which a different material is contained within a certain material. The same applies below. Non-metals may be silicon, oxygen, and fluorine. Non-metals are vaporized and removed by irradiating microwaves. However, if it is desired to leave non-metals, it is possible to leave them by adjusting the microwave energy. When the microwave energy is high, non-metals tend not to remain. When the microwave energy is low, non-metals tend to remain.

[0076] Metallic materials may have oxides such as oxide films formed on them. When metallic materials are cut, the surface becomes hot, and an oxide film tends to form on the surface. The oxides are vaporized and removed by irradiating microwaves. However, if it is desired to leave the oxides, it is possible to leave them by adjusting the microwave energy. If the microwave energy is high, the oxides tend not to remain. If the microwave energy is low, the oxides tend to remain.

[0077] The metal material may contain hydrogen. Hydrogen is vaporized and removed by microwave irradiation. However, if it is desired to retain hydrogen, it is possible to do so by adjusting the microwave energy. If the microwave energy is high, hydrogen tends not to remain. If the microwave energy is low, hydrogen tends to remain.

[0078] When the metal material is heated by microwaves, the metal material may be placed in a mold. Heating the metal material by microwaves may be performed in an inert gas atmosphere. Examples of the inert gas include argon (Ar) and helium (He). Heating the metal material by microwaves may also be performed in a neutral gas atmosphere. Examples of the neutral gas include nitrogen (N ２ ), dry hydrogen (H ２ ), and ammonia (NH ３ The metal contained in the metal raw material may be reacted with the gas. For example, when the metal raw material contains aluminum (Al), aluminum reacts with nitrogen (N ２ ) to form aluminum nitride (AlN).

[0079] The heating of the metal material with microwaves may be carried out in a reducing atmosphere. The reducing gas that provides the reducing atmosphere may be hydrogen (H ２ ), carbon monoxide (CO), and hydrocarbon gases (CH ４ , C ３ H ８ , C ４ H １０Heating a metal material with microwaves may be carried out in a vacuum. When it is desired to oxidize a metal material, the metal material may be heated with microwaves in an oxygen gas atmosphere. For example, when the metal raw material contains aluminum (Al), the aluminum is oxidized to form Al. ２ O ３ The gas generated when the metal material is heated by microwaves may be removed by suction from around the metal material.

[0080] The metal may be alloyed by heating a metal material mixed with alloying components with microwaves. Furthermore, when heating a metal material with microwaves, an additive such as carbon (C) may be added to the metal to compound the metal and the additive. Light elements mixed in the metal may be removed by heating the metal material with microwaves.

[0081] The produced metal-containing solid may or may not have an oxide film on the surface of the solid. When the energy of microwaves irradiated to the metal material is high, the produced metal-containing solid tends to have no oxide film on the surface. When the microwave energy is low, the produced metal-containing solid tends to have an oxide film on the surface. For example, when the metal-containing solid is used to be introduced into a molten metal, it is preferable that the surface does not have an oxide film.

[0082] Pressure may be applied to the metal materials or the solid containing the produced metal at least one of before, during, and after microwave irradiation. The pressure is not limited, but may be, for example, 1 MPa or more, 100 MPa or more, or 200 MPa or more, and 2000 MPa or less, 1900 MPa or less, or 1800 MPa or less. By applying pressure, the produced metal solid tends to become dense. Examples of pressure application methods include uniaxial molding, cold isostatic pressing (CIP) molding, hot isostatic pressing (HIP) molding, and roller pressing.

[0083] According to an embodiment, a fusion bonded portion in a cross section of a metal-containing solid is a portion where metals are melted and bonded together. According to an embodiment, a diffusion bonded portion in a cross section of a metal-containing solid is a portion where metals are bonded together by diffusion bonding. As described above, each of the plurality of metal materials may originate from at least one of a chill layer, a columnar crystal zone, and an equiaxed crystal zone. Therefore, a region surrounded by at least one of a fusion bonded portion and a diffusion bonded portion in a metal-containing solid may contain metal crystal grains. Furthermore, a region surrounded by at least one of a fusion bonded portion and a diffusion bonded portion in a metal-containing solid may contain metal columnar crystals. Furthermore, a region surrounded by at least one of a fusion bonded portion and a diffusion bonded portion in a metal-containing solid may contain metal equiaxed crystals. A region surrounded by at least one of a fusion bonded portion and a diffusion bonded portion in a metal-containing solid may include at least two selected from a region containing metal crystal grains, a region containing metal columnar crystals, and a region containing metal equiaxed crystals.

[0084] A metal-containing solid may have a eutectic structure at the fusion joint. The interface at the fusion joint may be interrupted and not connected to other interfaces. The fusion joint may not have an interface. Even if there is no interface, when regions of different crystal structures are adjacent, a fusion joint exists between the adjacent regions. For example, even if there is no interface, a fusion joint exists between a region containing metal crystal grains and a region containing metal columnar crystals, between a region containing metal crystal grains and a region containing metal equiaxed crystals, and between a region containing metal columnar crystals and a region containing metal equiaxed crystals. The fusion joint may be oxide-free or may contain oxides. Furthermore, the fusion joint may be non-metal-free or may contain non-metals. For example, when a metal-containing solid is used to be introduced into a molten metal, it is preferable that the fusion joint be oxide-free and non-metal-free. For example, when a metal-containing solid is used as an elastic material, it is preferable that a non-metal, such as a resin, is present in the fusion joint.

[0085] The metal-containing solid may have an interface at the diffusion bonded portion. The metal-containing solid may have voids at the diffusion bonded portion. The diffusion bonded portion may, for example, be oxide-free or may contain oxides. The diffusion bonded portion may, for example, be non-metal-free or may contain non-metals. For example, when the metal-containing solid is used to be introduced into a molten metal, it is preferable that the diffusion bonded portion be oxide-free and non-metal-free. For example, when the metal-containing solid is used as an elastic material, it is preferable that the diffusion bonded portion contain a non-metal such as a resin.

[0086] The metal-containing solid may have a portion where different crystalline structures are separated at at least one of the fusion bonded portion and the diffusion bonded portion. The fusion bonded portion and the diffusion bonded portion formed by the interface between the metal materials may be mesh-like. In a cross section of the metal-containing solid, each of a plurality of regions separated by the mesh-like fusion bonded portion and the diffusion bonded portion may have any of two or more different crystalline structures. The metal-containing solid may have a plurality of regions in a cross section, and each of the plurality of regions may have any of two or more different crystalline structures. A metal-containing solid produced by joining metal materials by microwave irradiation has mechanical strength and is therefore less likely to break during transportation.

[0087] A solid containing a metal may further have a contact joint in its cross section that is different from the fusion joint and the diffusion joint. In the contact joint, for example, metals are in close contact with each other due to pressure from the surroundings. For example, when molded bodies containing multiple metal materials are stacked and irradiated with microwaves, the interfaces between the molded bodies may form a contact joint. However, the interfaces between the molded bodies may also form a fusion joint and a diffusion joint. The joint formed by the interfaces between the molded bodies may be linear.

[0088] In a metal-containing solid produced by irradiating a plurality of metal materials with microwaves, voids are generated in the portions where the metal materials are not bonded. Therefore, the metal-containing solid according to the embodiment may be porous, containing voids inside. In a metal-containing solid produced by irradiating a plurality of metal materials with microwaves, a high-density layer with few voids tends to be formed on the surface side in a cross section. Furthermore, in a metal-containing solid, a low-density layer with many voids surrounded by a high-density layer tends to be formed in a cross section. In a metal-containing solid produced without microwave irradiation, the density of voids tends to be uniform.

[0089] The volume fraction of voids in the metal-containing solid according to the embodiment may be, for example, 0% to 50%, 15% to 45%, or 30% to 40%. The metal-containing solid according to the embodiment may be flexible. As described above, the size of the voids can be adjusted by the size of the metal slices irradiated with microwaves. Therefore, the volume fraction of voids in the metal-containing solid is adjustable. When the volume fraction of voids in the metal-containing solid is large, the flexibility of the metal-containing solid tends to be high. When the volume fraction of voids in the metal-containing solid is small, the flexibility of the metal-containing solid tends to be low. Flexible metal-containing solids can be used as materials that are resistant to pressure and vibration. The metal-containing solid according to the embodiment may not have an oxide film on the internal surface of the solid that contacts the voids, or may have an oxide film on the internal surface of the solid that contacts the voids. When the energy of the microwaves irradiated to the metal material is high, the surface of the metal-containing solid that contacts the voids tends to be free of an oxide film. When the microwave energy is low, an oxide film tends to be formed on the surface adjacent to the voids inside the solid containing the metal to be produced. For example, when the solid containing the metal is used to be poured into a molten metal, it is preferable that there is no oxide film on the surface adjacent to the voids inside the solid.

[0090] The metal-containing solid according to the embodiment may be used for melting in a molten metal. The molten metal contains a metal. Preferably, at least a portion of the metal contained in the molten metal is the same as at least a portion of the metal contained in the metal-containing solid according to the embodiment. For example, the specific gravity of the metal-containing solid according to the embodiment is greater than that of the molten metal. A metal casting may be produced by pouring the molten metal containing the metal-containing solid according to the embodiment into a mold and solidifying the molten metal in the mold. A metal-containing solid that is free of oxides and nonmetals on its surface and interior, or has low oxides and nonmetals, can suppress the generation of gas, steam explosions, fires, slag, and blisters even when poured into the molten metal. Furthermore, a metal-containing solid that is free of oxides or has low oxides on its surface and interior has high wettability with the molten metal and therefore easily sinks in the molten metal. Therefore, compared to solids that do not easily sink in the molten metal, a solid that easily sinks in the molten metal has a faster melting rate due to easier heat transfer within the interior.

[0091] Therefore, the metal-containing solid according to the embodiment can lower the heating temperature before being poured into the molten metal and shorten the time required for dissolving in the high-temperature molten metal, thereby reducing the energy required for heating and the amount of carbon dioxide (CO ) that accompanies heating. ２ In addition, since recycled products can be used as the metal material that becomes the metal-containing solid material according to the embodiment, it is possible to reduce the production of new metals.

[0092] The use of the metal-containing solid according to the embodiment is not limited to dissolving it in a molten metal and recycling it. The metal-containing solid according to the embodiment can be used for various applications. For example, the metal-containing solid according to the embodiment can be used as a fertilizer, a tool, an additive for material preparation, a fungicide, and a sterilant. Furthermore, the metal-containing solid according to the embodiment may contain carbon or resin by leaving the carbon or resin when manufactured by irradiating microwaves. The metal may be compounded with a non-metal such as carbon or resin. The metal-containing solid containing carbon or resin can be used as a sound-absorbing member, a sound-absorbing tool, a vibration-damping member, and a vibration-damping tool. An example of a vibration-damping tool is a vibration-damping hammer. Furthermore, the metal-containing solid according to the embodiment may contain a catalyst by adding a catalyst to a metal material and leaving the catalyst when manufactured by irradiating microwaves. The metal-containing solid containing a catalyst can be used as a functional member.

[0093] Example 1: A cylindrical mold with a diameter of 80 mm and a depth of 100 mm was prepared. Metal powder (hereinafter referred to as "A6061 metal powder") made of aluminum alloy A6061 was also prepared. The metal powder had a long side of 15 mm, a short side of 0.5 mm, and a thickness of 0.1 mm. The A6061 metal powder was obtained by cutting a die-cast casting. The die-cast casting had a chill layer consisting of fine crystal grains, a columnar crystal zone consisting of elongated columnar crystals, and an equiaxed crystal zone consisting of equiaxed crystals with isotropic crystal grain orientation. Therefore, the A6061 metal powder included metal powder consisting of fine crystal grains derived from the chill layer, metal powder consisting of columnar crystals derived from the columnar crystal zone, and metal powder consisting of equiaxed crystals derived from the equiaxed crystal zone. Coolant, oil, and water were attached to the metal powder. A6061 metal powder was placed in a mold, and a pressure of 80 MPa was applied to produce a briquette made of aluminum alloy A6061 (hereinafter referred to as "A6061 briquette"). The same method was repeated to produce multiple A6061 briquettes.

[0094] A plurality of A6061 briquettes were stacked, and the stacked A6061 briquettes were irradiated with 1.5 kW microwaves for 2500 seconds to heat the stacked A6061 briquettes to 400° C. This resulted in a metal solid made of aluminum alloy A6061 in which the stacked A6061 briquettes were integrated (hereinafter referred to as an “A6061 metal solid”).

[0095] Figure 1 shows a photograph of the A6061 solid metal, which was cut with a band saw and polished, taken with an optical microscope. In the cross section of the A6061 solid metal, tightly bonded joints where A6061 briquettes were tightly bonded together were observed. The tightly bonded joints were straight and were observed at equal intervals corresponding to the thickness of the A6061 briquettes. Furthermore, in the cross section of the A6061 solid metal, diffusion-bonded joints and fusion-bonded joints where A6061 metal powder particles were bonded together were observed.

[0096] An interface was observed at the diffusion bonded joint. Voids were also observed at the interface of the diffusion bonded joint. In some diffusion bonded joints, no voids were observed. The opposing regions on either side of the diffusion bonded joint included either a region where both were made of fine crystal grains, a region where both were made of columnar crystals, a region where both were made of equiaxed crystals, a region where one was made of fine crystal grains and the other was made of columnar crystals, a region where one was made of fine crystal grains and the other was made of equiaxed crystals, or a region where one was made of fine columnar crystals and the other was made of equiaxed crystals.

[0097] The fusion bonded joint had some areas with interfaces and some without. Some of the interfaces in the fusion bonded joint were disconnected and not connected to other interfaces. Furthermore, no voids were observed in the fusion bonded joint. The opposing regions across the fusion bonded joint included either a region consisting of both fine crystal grains, a region consisting of both columnar crystals, a region consisting of both equiaxed crystals, a region consisting of one fine crystal grain and the other columnar crystals, a region consisting of one fine crystal grain and the other equiaxed crystals, or a region consisting of one fine columnar crystal and the other equiaxed crystals. Even without an interface, the areas between a region consisting of one fine crystal grain and a region consisting of columnar crystals, a region consisting of one fine crystal grain and a region consisting of equiaxed crystals, and a region consisting of one fine columnar crystal and the other equiaxed crystals were determined to be fusion bonded joints.

[0098] Example 2 A cylindrical die with a diameter of 50 mm and a depth of 5 mm was prepared. Metal powder (hereinafter referred to as "ADC12 metal powder") made of aluminum alloy ADC12 was also prepared. The metal powder had a long side of 10 mm, a short side of 3 mm, and a thickness of 0.3 mm. The ADC12 metal powder was obtained by cutting a die-cast casting. The ADC12 metal powder included metal powder made of fine crystal grains derived from the chill layer, metal powder made of columnar crystals derived from the columnar crystal zone, and metal powder made of equiaxed crystals derived from the equiaxed crystal zone. Coolant, oil, and water were attached to the metal powder. The ADC12 metal powder was placed in the die, and a pressure of 80 MPa was applied to produce briquettes made of aluminum alloy ADC12 (hereinafter referred to as "ADC12 briquettes"). The same method was repeated to produce multiple ADC12 briquettes.

[0099] A plurality of ADC12 briquettes were stacked, and the stacked ADC12 briquettes were irradiated with 1.5 kW microwaves for 900 seconds to heat the stacked ADC12 briquettes to 400° C. This resulted in a metal solid made of aluminum alloy ADC12 in which the stacked ADC12 briquettes were integrated (hereinafter referred to as an “ADC12 metal solid”).

[0100] A photograph of the ADC12 solid metal, which was cut with a band saw and the exposed cross section polished, taken with an optical microscope, is shown in Figure 2. Similar to the cross section of the A6061 solid metal, adhesive joints where ADC12 briquettes were adhesively joined together, and diffusion joints and fusion joints where ADC12 metal powder particles were joined together were observed in the cross section of the ADC12 solid metal. The characteristics of the adhesive joints, diffusion joints, and fusion joints in the cross section of the ADC12 solid metal were similar to those of the adhesive joints, diffusion joints, and fusion joints in the cross section of the A6061 solid metal.

[0101] Example 3 A cylindrical die with a diameter of 30 mm and a depth of 30 mm was prepared. Metal scrap made of oxygen-free copper (hereinafter referred to as "oxygen-free copper scrap") was also prepared. The metal scrap had a diameter of 2 mm and a length of 5 mm. Oxygen-free copper metal powder was obtained by cutting a die-cast casting. The oxygen-free copper metal scrap included metal scrap made of fine crystal grains derived from the chill layer, metal scrap made of columnar crystals derived from the columnar crystal zone, and metal scrap made of equiaxed crystals derived from the equiaxed crystal zone. Coolant liquid, oil, and water were attached to the metal powder. The oxygen-free copper metal scrap was placed in the die, and a pressure of 347 MPa was applied to produce briquettes made of oxygen-free copper (hereinafter referred to as "oxygen-free copper briquettes"). The same method was repeated to produce multiple oxygen-free copper briquettes.

[0102] A plurality of oxygen-free copper briquettes were stacked, and the stacked oxygen-free copper briquettes were irradiated with 1.5 kW microwaves for 3000 seconds while applying a pressure of 10 MPa to heat the stacked oxygen-free copper briquettes to 700° C. This resulted in a metal solid made of oxygen-free copper in which the stacked oxygen-free copper briquettes were integrated (hereinafter referred to as an “oxygen-free copper metal solid”).

[0103] An oxygen-free copper metal solid was cut with a band saw, the exposed cross section was polished, and a photograph taken with an optical microscope is shown in Figure 3. In the cross section of the oxygen-free copper metal solid, similar to the cross section of the A6061 metal solid, a tightly bonded joint where oxygen-free copper briquettes were tightly bonded to each other, and a diffusion-bonded joint and a fusion-bonded joint where oxygen-free copper metal powders were bonded to each other were observed. The characteristics of the tightly bonded joint, diffusion-bonded joint, and fusion-bonded joint in the cross section of the oxygen-free copper metal solid were similar to those of the tightly bonded joint, diffusion-bonded joint, and fusion-bonded joint in the cross section of the A6061 metal solid.

[0104] Comparative Example 1 A photograph taken with an optical microscope of a cross section exposed by cutting an ingot made of aluminum alloy ADC12 produced by casting (hereinafter referred to as "ADC12 ingot") is shown in Fig. 4. In the cross section of the ADC12 ingot, the entire ingot was melted and then solidified, and no joint indicating an interface was observed, with only an acicular crystal structure being observed.

[0105] (Example 4, Comparative Example 2) The ADC12 metal solid according to Example 4 was prepared in the same manner as in Example 2. Furthermore, the ADC12 metal solid according to Comparative Example 2 was prepared by heating the ADC12 briquettes on a hot plate at 500°C for 1000 seconds without irradiating them with microwaves. The briquettes of the ADC12 metal solid material according to Example 4 and the ADC12 metal solid material according to Comparative Example 2 were identical in composition, weight, etc. As shown in FIG. 5 , the ADC12 metal solid according to Example 4 and the ADC12 metal solid according to Comparative Example 2 were each cut, and the ADC12 metal solid according to Example 4 and the ADC12 metal solid according to Comparative Example 2 were embedded in epoxy resin so that the cut surfaces were exposed. The cut surfaces were polished using waterproof abrasive paper containing silicon carbide (SiC) abrasive grains, and further lapped using diamond abrasive grains and a lubricant containing alcohol and ethylene glycol. As a result, the ADC12 metal solid according to Comparative Example 2 was brittle to polishing, and chipping occurred, especially near the periphery. In contrast, the ADC12 metal solid according to Example 4 was resistant to polishing and did not chip. It was also observed that the ADC12 metal solid according to Example 4 had a smaller cross-sectional area of ​​voids and a higher metal density than the ADC12 metal solid according to Comparative Example 2.

[0106] Furthermore, the cross sections of the ADC12 metallic solid according to Example 4 and the ADC12 metallic solid according to Comparative Example 2 were observed with a scanning electron microscope (SEM). As a result, as shown in FIG. 6, a white layer was observed at the metal interface facing the voids in the ADC12 metallic solid according to Comparative Example 2. On the other hand, no white layer was observed at the metal interface facing the voids in the ADC12 metallic solid according to Example 4. As shown in FIG. 7, nine locations, 1-1 to 1-9, on the cross section of the ADC12 metallic solid according to Comparative Example 2 were analyzed with scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX). As a result, silicon (Si), oxygen (O), and fluorine (F) were observed in greater amounts at locations 1-5 to 1-7 of the metal interface facing the voids, compared to locations 1-1 to 1-4, 1-8, and 1-9 inside the metallic solid that were not in contact with the interface. Therefore, it was shown that a metal oxide film, a release agent, and processing oil remained at the metal interface facing the voids in the ADC12 metal solid in Comparative Example 2, which was not irradiated with microwaves.

[0107] Next, as shown in Figure 8, the ADC12 metal solid according to Example 4 and the ADC12 metal solid according to Comparative Example 2 were each analyzed using a computed tomography (CT) scanner. When the total volume of the ADC12 metal solid according to Comparative Example 2 was taken as 100%, the total volume of the ADC12 metal solid according to Example 4 was 97%. Furthermore, compared with the volume of voids in the ADC12 metal solid according to Comparative Example 2, the volume of voids in the ADC12 metal solid according to Example 4 was reduced by 20%. It was observed that the ADC12 metal solid according to Example 4 had a high-density layer with few voids on the surface side in cross section, and a low-density layer with many voids surrounded by the high-density layer in cross section.

[0108] (Example 5, Comparative Examples 3 and 4) A cylindrical die with a diameter of 80 mm and a depth of 100 mm was prepared. ADC12 metal powder was also prepared. The metal powder had a long side of 10 mm, a short side of 3 mm, and a thickness of 0.3 mm. The ADC12 metal powder was obtained by cutting a die-cast casting. The ADC12 metal powder included metal powder composed of fine crystal grains derived from the chill layer, metal powder composed of columnar crystals derived from the columnar crystal zone, and metal powder composed of equiaxed crystals derived from the equiaxed crystal zone. Coolant, oil, and water were attached to the metal powder. The ADC12 metal powder was placed in the die, and a pressure of 80 MPa was applied to produce ADC12 briquettes. The same method was repeated to produce multiple ADC12 briquettes.

[0109] A plurality of ADC12 briquettes were stacked, and the stacked ADC12 briquettes were irradiated with microwaves of 6.0 kW for 15 minutes to heat the stacked ADC12 briquettes to 600° C. As a result, a metal solid made of aluminum alloy ADC12 in which the stacked ADC12 briquettes were integrated (hereinafter referred to as the “ADC12 metal solid according to Example 5”) was obtained.

[0110] Furthermore, the stacked ADC12 briquettes were heated at 500°C for 80 minutes in an electric furnace without being irradiated with microwaves to obtain an ADC12 metal solid according to Comparative Example 3. Furthermore, the stacked ADC12 briquettes were not heated at all, and only a pressure of 80 MPa was applied to obtain an ADC12 metal solid according to Comparative Example 4.

[0111] 9 and 10 , a force was applied parallel to the diameter direction of the cross section to the side surfaces of each of the ADC12 solid metal samples according to Example 5, Comparative Example 3, and Comparative Example 4, and the press was moved by a stroke of 10 mm. As a result, a strong compressive force was applied to the ADC12 solid metal samples according to Comparative Example 3 and Comparative Example 4, causing them to lose their shape. In contrast, no strong compressive force was applied to the ADC12 solid metal sample according to Example 5, and it did not lose its shape, demonstrating that the ADC12 solid metal sample according to Example 5 is flexible.

[0112] Next, as shown in Fig. 11 , the ADC12 metal solid according to Example 5 and the ADC12 metal solid according to Comparative Example 3 were each held at two points on the back surface, and force was applied to one point in the center of the front surface, thereby fracturing the ADC12 metal solid according to Example 5 and the ADC12 metal solid according to Comparative Example 3. As shown in Fig. 12 , when the fracture surfaces of the ADC12 metal solid according to Example 5 and the ADC12 metal solid according to Comparative Example 3 were observed, only brittle fracture was found to have occurred on the fracture surface of the ADC12 metal solid according to Comparative Example 3. In contrast, ductile fracture was found to have occurred on the fracture surface of the ADC12 metal solid according to Example 5.

[0113] Next, the ADC12 metal solid according to Example 5 and the ADC12 metal solid according to Comparative Example 3 were each heated to 400°C and placed on the surface of molten aluminum at 750°C. The state after 1 minute was observed. As a result, as shown in FIG. 13 , the ADC12 metal solid according to Comparative Example 3 did not sink into the molten aluminum. This indicated that an oxide film was present on the surface of the ADC12 metal solid according to Comparative Example 3, resulting in poor wettability. Furthermore, the surface of the ADC12 metal solid according to Comparative Example 3 was swollen. This indicated that the release agent, processing oil, etc. remained inside the ADC12 metal solid according to Comparative Example 3 and had vaporized and expanded.

[0114] The ADC12 metal solid according to Example 5 sank into the molten metal after 1 minute. This indicated that the surface of the ADC12 metal solid according to Example 5 was free of an oxide film and had good wettability. Furthermore, the surface of the ADC12 metal solid according to Example 5 was depressed before sinking. This indicated that no release agent, processing oil, etc. remained inside the ADC12 metal solid according to Example 5 and that dissolution was progressing from the back surface.

[0115] Furthermore, the time required for the ADC12 metal solid in Example 5 to completely dissolve was shorter than the time required for the ADC12 metal solid in Comparative Example 3 to completely dissolve.

[0116] (Example 6, Comparative Example 5) A cylindrical die with a diameter of 30 mm and a depth of 30 mm was prepared. ADC12 metal powder was also prepared. The metal powder had a long side of 10 mm, a short side of 3 mm, and a thickness of 0.3 mm. The ADC12 metal powder was obtained by cutting a die-cast casting. The ADC12 metal powder included metal powder composed of fine crystal grains derived from the chill layer, metal powder composed of columnar crystals derived from the columnar crystal zone, and metal powder composed of equiaxed crystals derived from the equiaxed crystal zone. Coolant, oil, and water were attached to the metal powder. The ADC12 metal powder was placed in the die, and a pressure of 80 MPa was applied to produce ADC12 briquettes. The same method was repeated to produce multiple ADC12 briquettes.

[0117] A plurality of ADC12 briquettes were stacked, and the stacked ADC12 briquettes were irradiated with 1.2 kW microwaves for 2 minutes while applying a pressure of 80 MPa to heat the stacked ADC12 briquettes to 450° C. This resulted in a metal solid made of aluminum alloy ADC12 in which the stacked ADC12 briquettes were integrated (hereinafter referred to as the “ADC12 metal solid according to Example 6”).

[0118] Furthermore, the stacked ADC12 briquettes were not heated at all, and only a pressure of 80 MPa was applied to obtain an ADC12 metal solid according to Comparative Example 5.

[0119] Next, the ADC12 metal solid according to Example 6 and the ADC12 metal solid according to Comparative Example 5 were each heated to 500°C and poured into molten aluminum at 680°C. As shown in FIG. 14 , gas was generated for approximately 45 seconds after the ADC12 metal solid according to Comparative Example 5 was poured into the molten aluminum, and then flames were generated for approximately 35 seconds. This indicated that the release agent, processing oil, etc. remained inside the ADC12 metal solid according to Comparative Example 5 and vaporized and ignited. On the other hand, the ADC12 metal solid according to Example 6 did not generate gas or flames when poured into the molten aluminum. This indicated that the release agent, processing oil, etc. did not remain inside the ADC12 metal solid according to Example 6.

[0120] Example 7 A cylindrical mold with a diameter of 30 mm and a depth of 10 mm was prepared. Copper (Cu) powder (hereinafter referred to as "large-size copper powder") derived from copper scrap and having a diameter of 2 mm and a length of 5 mm and copper (Cu) powder (hereinafter referred to as "small-size copper powder") derived from copper scrap and having a diameter of 0.1 mm and a length of 7 mm were also prepared. Next, mixed powders were prepared by mixing the large-size copper powder and the small-size copper powder in ratios of 10:0, 9:1, and 5:5. The mixed powders were placed in a mold and heated to 800°C in a microwave while applying a pressure of 10 MPa to produce copper briquettes. As a result, as shown in Figures 15 and 16 , it was observed that when the proportion of large-size copper powder in the mixed powder was high, the voids in the cross section of the copper briquette became large, and when the proportion of small-size copper powder increased, the interior of the copper briquette became dense.

[0121] Example 8: A cylindrical mold with a diameter of 30 mm and a depth of 30 mm was prepared. The same large-sized copper powder as in Example 7 was also prepared. The large-sized copper powder was placed in the mold, and a pressure of 346 MPa was applied to fabricate copper briquettes. The copper briquettes had a diameter of 30 mm and a thickness of 10.8 mm. The density was 87.48%. Next, the copper briquettes were irradiated with 1.3 kW microwaves for 5,400 seconds while applying a pressure of 10 MPa, and heated to 800°C over 90 minutes. After reaching 800°C, the copper briquettes were cooled in a microwave irradiation device. The temperature was measured with a thermocouple. The copper briquettes were then cut with a band saw, and the exposed cross section was polished. A photograph taken with an optical microscope is shown in Figure 17. Diffusion-bonded areas where copper powder particles were bonded and fusion-bonded areas (dendrites) were observed in the cross section of the copper briquette.

[0122] Although the present invention has been described above by way of embodiments and examples, the description and drawings that form part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. For example, as shown in FIG. 18 , microwaves may be irradiated onto a metal material containing multiple different metal species, and molten metals refined for each metal species may be recovered by utilizing the differences in melting points of the metal species. For example, when microwaves are irradiated onto a metal material containing multiple different metal species, the metal species with the lowest melting point may melt first, and the molten metal species with the lowest melting point may be extruded from a filter and recovered. Next, the metal species with the second lowest melting point may melt, and the molten metal species with the second lowest melting point may be extruded from a filter and recovered. Hereinafter, where n is a natural number, the metal species with the nth lowest melting point may melt, and the molten metal species with the nth lowest melting point may be extruded from a filter and recovered. It should be understood that the present invention encompasses various embodiments not described herein.

Claims

1. A solid comprising a metal, the solid having, in cross section, a fusion bond portion of the metal and a diffusion bond portion of the metal.

2. The solid according to claim 1, wherein at least one of the fusion joint and the diffusion joint has a portion where different crystal structures are separated.

3. The solid according to claim 1, wherein the area surrounded by at least one of the fusion bond and the diffusion bond contains crystal grains of the metal.

4. The solid according to claim 1, wherein a region surrounded by at least one of the fusion bond and the diffusion bond contains columnar crystals of the metal.

5. The solid of claim 1, wherein the area surrounded by at least one of the fusion bond and the diffusion bond contains equiaxed grains of the metal.

6. The solid according to claim 5, wherein said equiaxed crystals have at least one of a dendritic structure and a eutectic structure.

7. The solid according to claim 1, wherein the region surrounded by at least one of the molten bond and the diffusion bond includes at least two selected from a region containing crystal grains of the metal, a region containing columnar crystals of the metal, and a region containing equiaxed crystals of the metal.

8. The solid of claim 7, wherein the equiaxed crystals have at least one of a dendritic structure and a eutectic structure.

9. The solid of claim 1 having a eutectic structure of said metals in said fusion joint.

10. The solid of claim 1, wherein at said fusion joint, no interface is connected to any other interface.

11. The solid of claim 1 having an interface at said diffusion bond.

12. The solid of claim 1 having voids in said diffusion bond.

13. The solid of claim 1, wherein the metal comprises multiple metal species.

14. The solid of claim 1, wherein at least one of said fusion bond and said diffusion bond is oxide free.

15. The solid of claim 1, wherein at least one of the fusion bond and the diffusion bond has an oxide.

16. The solid of claim 1, wherein at least one of said fusion joint and said diffusion joint is free of oil.

17. The solid of claim 1, wherein at least one of the fusion joint and the diffusion joint has oil present.

18. The solid of claim 1, wherein at least one of said fusion bond and said diffusion bond is free of a release agent.

19. The solid of claim 1, wherein at least one of the fusion bond and the diffusion bond has a release agent.

20. The solid of claim 1, further comprising a bonded joint in said cross section distinct from said fusion joint and said diffusion joint.

21. The solid of claim 1, which is porous.

22. The solid of claim 1, which is flexible.

23. The solid of claim 1, further comprising a nonmetal.

24. The solid of claim 1, having no oxide film on the surface of said solid.

25. A solid according to claim 1 for dissolution in a molten metal.

26. A solid containing a metal, comprising: a high density layer having few voids on the surface side in a cross section; and a low density layer having many voids surrounded by the high density layer in the cross section.

27. The solid of claim 26, having a fusion bond of said metal and a diffusion bond of said metal in said cross section.

28. The solid of claim 26, which is porous.

29. The solid of claim 26, which is flexible.

30. The solid of claim 26, having no oxide film on the surface of said solid.

31. The solid of claim 26 for dissolution in a molten metal.

32. A method for producing a solid containing metal, comprising: irradiating a plurality of metal materials with microwaves to form a solid containing metal, wherein the solid containing metal has, in a cross section, a fused joint portion of the metal and a diffusion joint portion of the metal.

33. The method for producing a metal-containing solid as set forth in claim 32, wherein each of the plurality of metallic materials has one of two or more different crystal structures.

34. The method for producing a metal-containing solid according to claim 32, further comprising the step of reducing oxides contained in the plurality of metal materials by irradiating the plurality of metal materials with the microwaves.

35. The method for producing a metal-containing solid according to claim 32, further comprising the step of reducing non-metals mixed with the plurality of metal materials by irradiating the plurality of metal materials with the microwaves.

36. A method for melting a metal, comprising: preparing a solid containing a metal, the solid having a fused joint portion of the metal and a diffusion joint portion of the metal in a cross section; and dissolving the solid containing a metal in a molten metal.

37. The method for melting metals according to claim 36, wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

38. The method for melting metals as set forth in claim 37, wherein each of the plurality of metallic materials has one of two or more different crystal structures.

39. The method for melting metals according to claim 37, further comprising the step of reducing oxides contained in the plurality of metal materials by irradiating the plurality of metal materials with the microwaves.

40. The method for melting metals as set forth in claim 37, further comprising the step of reducing non-metals mixed with said plurality of metallic materials by irradiating said plurality of metallic materials with said microwaves.

41. The method of melting a metal as set forth in claim 36, further comprising heating the metal-containing solid at a temperature below the melting point of the metal prior to dissolving the metal-containing solid in the molten metal.

42. A method for melting a metal, comprising: preparing a metal-containing solid, the metal-containing solid having a high-density layer with few voids on the surface side in a cross section, and a low-density layer with many voids surrounded by the high-density layer in the cross section; and dissolving the metal-containing solid in a molten metal.

43. The method for melting metals according to claim 42, wherein the metal-containing solid is formed by irradiating a plurality of metal materials with microwaves.

44. The method for melting metals as set forth in claim 43, wherein each of the plurality of metallic materials has one of two or more different crystal structures.

45. A method for melting metals as set forth in claim 43, further comprising the step of reducing oxides contained in said plurality of metal materials by irradiating said plurality of metal materials with said microwaves.

46. ​​A method for melting metals as set forth in claim 43, further comprising the step of reducing non-metals mixed with said plurality of metallic materials by irradiating said plurality of metallic materials with said microwaves.

47. The method of melting a metal as described in claim 42, further comprising heating the metal-containing solid at a temperature below the melting point of the metal prior to dissolving the metal-containing solid in the molten metal.

48. A method for manufacturing a metal casting, comprising: preparing a solid containing metal, the solid having a fused joint portion of the metal and a diffusion joint portion of the metal in a cross section; dissolving the solid containing metal in a molten metal; pouring the molten metal in which the solid containing metal is dissolved into a mold; and solidifying the molten metal in the mold.

49. The method for producing a metal casting according to claim 48, wherein the metal-containing solid is formed by irradiating a plurality of metallic materials with microwaves.

50. The method of claim 49, wherein each of the plurality of metallic materials has one of two or more different crystal structures.

51. The method for producing a metal casting as set forth in claim 49, further comprising the step of reducing oxides contained in said plurality of metallic materials by irradiating said plurality of metallic materials with said microwaves.

52. The method for producing a metal casting as set forth in claim 49, further comprising reducing non-metallic components mixed with said plurality of metallic materials by irradiating said plurality of metallic materials with said microwaves.

53. The method of producing a metal casting as set forth in claim 48, further comprising heating the metal-containing solid below the melting point of the metal prior to dissolving the metal-containing solid in the molten metal.

54. A method for manufacturing a metal casting, comprising: preparing a metal-containing solid having a high-density layer with few voids on the surface side in a cross section, and a low-density layer with many voids surrounded by the high-density layer in the cross section; dissolving the metal-containing solid in molten metal; pouring the molten metal in which the metal-containing solid is dissolved into a casting mold; and solidifying the molten metal in the casting mold.

55. The method of producing a metal casting according to claim 54, wherein the metal-containing solid is formed by irradiating a plurality of metallic materials with microwaves.

56. The method of producing a metal casting as recited in claim 55, wherein each of the plurality of metallic materials has one of two or more different crystal structures.

57. The method for producing a metal casting as set forth in claim 55, further comprising irradiating the plurality of metal materials with the microwaves to reduce oxides contained in the plurality of metal materials.

58. The method for producing a metal casting as set forth in claim 55, further comprising reducing non-metallic components mixed with said plurality of metallic materials by irradiating said plurality of metallic materials with said microwaves.

59. The method of claim 54, further comprising heating the metal-containing solid below the melting point of the metal prior to dissolving the metal-containing solid in the molten metal.

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