Casting mold, method of manufacturing the same, use thereof, and method of manufacturing metal ingot

Abstract

The application discloses a casting mold, a manufacturing method and application thereof, and a preparation method of a metal ingot. The casting mold comprises a mold body, a bottom layer, a gradient layer and a top layer, the gradient layer is located between the bottom layer and the top layer, and the bottom layer covers the outer wall of the mold body; the bottom layer contains one of the following element compositions: (a) Ni and Al; (b) Ni, Co, Cr, Al and Y; (c) Co, Cr, Al and Y; the top layer contains an oxide selected from one of (i) and (ii): (i) a composite oxide of Y2O3 and ZrO2; (ii) Re2Zr2O7; the gradient layer comprises first to fifth gradient layers which are sequentially attached, the first gradient layer is close to the bottom layer, and the fifth gradient layer is close to the top layer; the content of the chemical composition gradually increases from the first gradient layer to the top layer. The binding force between the composite coating of the casting mold and the mold body is strong, and the generation of shrinkage holes can be reduced.

Description

Technical Field

[0001] This invention relates to a casting mold, its manufacturing method and uses, and also to a method for preparing metal ingots. Background Technology

[0002] Dy and Tb targets are key materials for the vacuum deposition fabrication of high-performance grain boundary diffusion magnets. Currently, Dy and Tb targets are typically prepared using vacuum induction melting and casting methods, with casting molds usually made of cast iron, carbon steel, or alloy steel. During the cooling process, the molten metal near the mold wall cools rapidly, resulting in poor fluidity and insufficient feeding capacity, leading to shrinkage cavities in the metal ingot.

[0003] CN112725675B discloses a method for manufacturing a dysprosium / terbium target. The method involves casting a dysprosium / terbium-containing alloy mix or a pure dysprosium / terbium molten metal into a water-cooled graphite mold under vacuum or inert gas protection to form a cast billet. The billet is then held at a certain temperature and cooled to obtain a cast billet with a specific grain structure. The billet is then subjected to deformation processing. This method uses a water-cooled graphite mold as the casting mold, which accelerates the cooling rate of the molten metal near the mold wall.

[0004] CN116121714A discloses a low surface energy, corrosion-resistant, high-entropy composite coating for die-casting molds, comprising a gradient structure consisting of a bonding layer, a gradient layer, a hardening layer, a wear-resistant layer, an anti-aluminum melt corrosion layer, and a low surface energy aluminum-repellent layer. This mold is a die-casting mold, exhibiting good corrosion resistance but weak heat insulation. Summary of the Invention

[0005] In view of this, one object of the present invention is to provide a casting mold in which the composite coating has a strong bond between itself and the mold body, thereby reducing shrinkage cavities generated during the solidification process of the ingot. Furthermore, the composite coating of the casting mold is not easily detached or cracked after heating. Another object of the present invention is to provide a method for preparing the above-mentioned casting mold. This method can improve the density of the coating and the bond between it and the mold body. A further object of the present invention is to provide an application of the casting mold. Yet another object of the present invention is to provide a method for preparing a metal ingot that can reduce the generation of shrinkage cavities.

[0006] On one hand, the present invention provides a casting mold comprising a mold body, a bottom layer, a gradient layer and a top layer, wherein the gradient layer is located between the bottom layer and the top layer, and the bottom layer covers the outer wall of the mold body;

[0007] The underlying layer contains one of the following elements:

[0008] (a) Ni and Al;

[0009] (b) Ni, Co, Cr, Al and Y;

[0010] (c) Co, Cr, Al, and Y;

[0011] The top layer contains an oxide, which is selected from one of (i) to (ii):

[0012] (i) A composite oxide of Y₂O₃ and ZrO₂;

[0013] (ii) Re₂Zr₂O₇; wherein Re is selected from one or more of La, Gd, and Dy;

[0014] The gradient layer includes a first gradient layer, a second gradient layer, a third gradient layer, a fourth gradient layer, and a fifth gradient layer that are sequentially attached to each other, with the first gradient layer being closer to the bottom layer and the fifth gradient layer being closer to the top layer;

[0015] The gradient layer contains bottom chemical components and top chemical components, and the content of top chemical components gradually increases from the first gradient layer to the fifth gradient layer.

[0016] According to the casting mold of the present invention, preferably, in the first gradient layer, the chemical composition of the bottom layer accounts for 80-95 at%; in the second gradient layer, the chemical composition of the bottom layer accounts for 60-80 at%; in the third gradient layer, the chemical composition of the bottom layer accounts for 40-60 at%; in the fourth gradient layer, the chemical composition of the bottom layer accounts for 20-40 at%; and in the fifth gradient layer, the chemical composition of the bottom layer accounts for 3-20 at%.

[0017] According to the casting mold of the present invention, preferably, the composite oxide of Y2O3 and ZrO2 is a solid solution formed by Y2O3 and ZrO2, and the molar ratio of Y2O3 to ZrO2 is (0.05~0.12):0.92.

[0018] According to the casting mold of the present invention, preferably, in the elemental composition (a), based on the total mass of each element in the elemental composition (a), the Al content is 0.5 to 10 wt% and the Ni content is 85 to 99.5 wt%.

[0019] In elemental composition (b), based on the total mass of each element in elemental composition (b), the Cr content is 10–25 wt%, the Al content is 5–20 wt%, the Y content is 0.1–2 wt%, the Co content is 15–30 wt%, and the Ni content is 35–60 wt%.

[0020] In the elemental composition (c), based on the total mass of each element in the elemental composition (c), the Cr content is 20-40 wt%, the Al content is 1-10 wt%, the Y content is 0.1-2 wt%, and the Co content is 55-75 wt%.

[0021] According to the casting mold of the present invention, preferably, based on the total mass of each element in elemental composition (a), elemental composition (a) also contains 0.05 to 0.8 wt% Si.

[0022] According to the casting mold of the present invention, preferably, the material of the mold body is selected from carbon steel, cast iron, and alloy steel.

[0023] According to the casting mold of the present invention, preferably, the thickness of the bottom layer is 80-170 μm, the thickness of the gradient layer is 750-1150 μm, and the thickness of the top layer is 130-200 μm.

[0024] On the other hand, the present invention provides a method for preparing the above-mentioned casting mold, comprising the following steps:

[0025] (1) The alloy raw materials are used to form a base layer on the outer wall of the mold body by plasma spraying process;

[0026] (2) The alloy raw materials and oxide raw materials are used to form the first to fifth gradient layers on the bottom layer by plasma spraying process;

[0027] (3) The oxide raw material is formed on the fifth gradient layer by plasma spraying process.

[0028] In another aspect, the present invention provides the use of the above-mentioned casting mold in the preparation of metal ingots.

[0029] In another aspect, the present invention provides a method for preparing a metal ingot, comprising the following steps: casting molten metal into the casting mold.

[0030] The composite coating of the casting mold of the present invention has strong adhesion to the mold body, which can reduce shrinkage cavities generated during the solidification process of the ingot. Furthermore, the composite coating of the casting mold is not easily peeled off or cracked after heating. The preparation method of the present invention can improve the density of the coating and the adhesion between the coating and the mold body. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a casting mold according to the present invention.

[0032] The detailed labeling in the attached figures is as follows:

[0033] 1-Mold body; 2-Bottom layer; 3-Gradient layer; 4-Top layer. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] The "composite coating" mentioned in this invention refers to a composite coating consisting of a bottom layer, a gradient layer, and a top layer.

[0036] <Casting mold>

[0037] The casting mold of the present invention includes a mold body, a bottom layer, a gradient layer, and a top layer. The gradient layer is located between the bottom layer and the top layer. The bottom layer covers the outer wall of the mold body. The gradient layer covers the outer wall of the bottom layer. The top layer covers the outer wall of the gradient layer.

[0038] The material of the mold body is selected from one or more of carbon steel, cast iron, and alloy steel.

[0039] In some embodiments, the mold body contains Fe, C, and Si elements. In some embodiments, it also contains Mn and / or Cr. Preferably, it also contains one or more of Ni, Cu, and Mo.

[0040] The Fe content can be 85 to 99.5 parts by weight; preferably 90 to 99 parts by weight. In some embodiments, the Fe content is 95 to 98 parts by weight.

[0041] The content of C can be 0.2 to 5 parts by weight; preferably 0.3 to 3 parts by weight. In some embodiments, the content of C is 0.4 to 0.6 parts by weight.

[0042] The Si content can be 0.05 to 3 parts by weight; preferably 0.1 to 2 parts by weight. In some embodiments, the Si content is 0.15 to 0.3 parts by weight.

[0043] The Mn content can be 0.3 to 2 parts by weight; preferably 0.5 to 1.5 parts by weight; more preferably 0.7 to 1 part by weight.

[0044] The Cr content can be 0.05 to 4 parts by weight; preferably 0.1 to 2.5 parts by weight. In some embodiments, the Cr content is 0.3 to 0.8 parts by weight.

[0045] The Ni content can be less than or equal to 4 parts by weight. In some embodiments, the Ni content is 1 to 2.5 parts by weight. In other embodiments, the Ni content is less than or equal to 0.3 parts by weight. In still other embodiments, the Ni content is less than or equal to 0.05 parts by weight.

[0046] The Cu content can be less than or equal to 0.8 parts by weight. In some embodiments, the Cu content is 0.1 to 0.5 parts by weight. In other embodiments, the Cu content is less than or equal to 0.5 parts by weight. In still other embodiments, the Cu content is less than or equal to 0.05 parts by weight.

[0047] The content of Mo can be 0.05 to 1.5 parts by weight; preferably 0.1 to 1 part by weight; more preferably 0.5 to 0.8 parts by weight.

[0048] The mold body may contain small amounts of phosphorus (P) and sulfur (S). The content of P is ≤0.1 parts by weight; preferably, the content of P is ≤0.06 parts by weight; more preferably, the content of P is ≤0.03 parts by weight. The content of S is ≤0.1 parts by weight; preferably, the content of S is ≤0.05 parts by weight; more preferably, the content of S is ≤0.03 parts by weight.

[0049] The underlying layer consists of one of the following elements:

[0050] (a) Ni and Al;

[0051] (b) Ni, Co, Cr, Al and Y;

[0052] (c) Co, Cr, Al and Y.

[0053] In elemental composition (a), the Al content is 0.5 to 10 wt%; preferably 2 to 8 wt%; more preferably 3 to 6 wt%.

[0054] In elemental composition (a), the Ni content is 85–99.5 wt%; preferably 90–98 wt%; more preferably 94–96 wt%.

[0055] The elemental composition (a) may also include Si. The Si content is 0.05 to 0.8 wt%; preferably 0.1 to 0.6 wt%; more preferably 0.3 to 0.5 wt%.

[0056] In elemental composition (b), the Cr content is 10–25 wt%; preferably 12–22 wt%; more preferably 15–20 wt%.

[0057] In elemental composition (b), the Al content is 5–20 wt%; preferably 8–15 wt%; more preferably 10–13 wt%.

[0058] In elemental composition (b), the Y content is 0.1–2 wt%; preferably 0.3–1.5 wt%; more preferably 0.5–1 wt%.

[0059] In elemental composition (b), the Co content is 15-30 wt%; preferably 20-28 wt%; more preferably 23-25 ​​wt%.

[0060] In elemental composition (b), the Ni content is 35–60 wt%; preferably 40–55 wt%; more preferably 45–50 wt%.

[0061] In the elemental composition (c), the Cr content is 20-40 wt%; preferably 25-35 wt%; more preferably 28-30 wt%.

[0062] In the elemental composition (c), the Al content is 1 to 10 wt%; preferably 3 to 8 wt%; more preferably 5 to 7 wt%.

[0063] In the elemental composition (c), the Y content is 0.1–2 wt%; preferably 0.3–1.5 wt%; more preferably 0.5–1 wt%.

[0064] In the elemental composition (c), the Co content is 55-75 wt%; preferably 60-70 wt%; more preferably 65-68 wt%.

[0065] In some implementations, the underlying layer is composed of elements as shown in one of the above examples.

[0066] The thickness of the bottom layer can be 80–170 μm; preferably 100–150 μm; more preferably 120–130 μm.

[0067] The top layer contains an oxide. In some embodiments, the top layer is formed of an oxide. The oxide is selected from one of (i) to (ii):

[0068] (i) A composite oxide of Y₂O₃ and ZrO₂;

[0069] (ii) Re₂Zr₂O₇; wherein Re is selected from one or more of La, Gd, and Dy. In some embodiments, Re is La. In other embodiments, Re is Gd.

[0070] In the composite oxide of Y₂O₃ and ZrO₂, the molar ratio of Y₂O₃ to ZrO₂ is (0.05–0.12):0.92; preferably (0.06–0.1):0.92; more preferably (0.08–0.09):0.92. The composite oxide of Y₂O₃ and ZrO₂ is a solid solution formed by Y₂O₃ and ZrO₂.

[0071] The thickness of the top layer can be 130–200 μm; preferably 150–180 μm. In some embodiments, the thickness of the top layer is 160–170 μm.

[0072] In some implementations, the bottom layer and the top layer can be selected from a combination of one of the following:

[0073] (A) The bottom layer contains Ni, Si and Al, and the top layer contains Y2O3 and ZrO2.

[0074] (B) The bottom layer contains Ni, Co, Cr, Al and Y, and the top layer contains La2Zr2O7.

[0075] (C) The bottom layer contains Co, Cr, Al and Y, and the top layer contains Gd2Zr2O7.

[0076] The gradient layer consists of a first gradient layer, a second gradient layer, a third gradient layer, a fourth gradient layer, and a fifth gradient layer, which are bonded together in sequence. The first gradient layer is bonded to the bottom layer. The fifth gradient layer is bonded to the top layer.

[0077] The gradient layer contains both bottom-layer and top-layer chemical components. In some embodiments, the gradient layer contains only bottom-layer and top-layer chemical components. The chemical components of the top layer gradually increase from the first gradient layer to the fifth gradient layer. The chemical components of the bottom layer gradually decrease from the first gradient layer to the fifth gradient layer.

[0078] In the first gradient layer, the chemical composition of the bottom layer accounts for 80-95 at%; preferably, 85-90 at%. The chemical composition of the top layer accounts for 5-20 at%; preferably, 10-15 at%.

[0079] The thickness of the first gradient layer can be 100–150 μm; preferably 110–140 μm. In some embodiments, the thickness of the first gradient layer is 120–130 μm.

[0080] In the second gradient layer, the bottom layer contains 60–80 at% of chemical components; preferably, 70–75 at%. The top layer contains 20–40 at% of chemical components; preferably, 25–30 at%.

[0081] The thickness of the second gradient layer can be 120–180 μm; preferably 150–170 μm. In some embodiments, the thickness of the second gradient layer is 160–170 μm.

[0082] In the third gradient layer, the chemical composition of the bottom layer accounts for 40–60 at%; preferably, 50–55 at%. The chemical composition of the top layer accounts for 40–60 at%; preferably, 45–50 at%.

[0083] The thickness of the third gradient layer can be 150–230 μm; preferably 170–210 μm. In some embodiments, the thickness of the third gradient layer is 180–200 μm.

[0084] In the fourth gradient layer, the bottom layer contains 20–40 at% of chemical components; preferably, 30–45 at%. The top layer contains 60–80 at% of chemical components; preferably, 55–70 at%.

[0085] The thickness of the fourth gradient layer can be 180–260 μm; preferably 200–240 μm. In some embodiments, the thickness of the fourth gradient layer is 210–220 μm.

[0086] In the fifth gradient layer, the bottom layer contains 3–20 at% of chemical components; preferably, 10–15 at%. The top layer contains 80–97 at% of chemical components; preferably, 85–90 at%.

[0087] The thickness of the fifth gradient layer can be 250–330 μm; preferably 270–310 μm. In some embodiments, the thickness of the fifth gradient layer is 280–300 μm.

[0088] <Preparation method of casting mold>

[0089] The method for preparing the casting mold of the present invention includes the following steps: (1) forming a bottom layer; (2) forming a gradient layer; and (3) forming a top layer. In some embodiments, a pretreatment step is also included.

[0090] Steps to form the bottom layer

[0091] The alloy raw materials are applied to the outer wall of the mold body using a plasma spraying process to form a base layer.

[0092] The elemental composition of the alloy raw material is determined based on the elemental composition of the underlying material. The alloy raw material can be a powder. Specifically, the alloy raw material can be spherical powder. The particle size range of the alloy raw material is 15–53 μm.

[0093] The main gas flow rate can be 1300-2200 L / h; preferably 1500-2000 L / h; more preferably 1750-1900 L / h.

[0094] The spraying voltage can be 40–80V; preferably 50–70V. In some embodiments, the spraying voltage is 55–60V.

[0095] The spraying current can be 400-800A; preferably 450-700A; more preferably 500-600A.

[0096] The spraying distance can be 100-250mm; preferably 120-200mm; more preferably 150-170mm.

[0097] The powder feeding rate can be 0.05 to 1 r / min; preferably 0.1 to 0.8 r / min; more preferably 0.4 to 0.6 r / min.

[0098] Steps to form a gradient layer

[0099] The alloy raw materials and oxide raw materials are used to form the first to fifth gradient layers on the bottom layer using a plasma spraying process.

[0100] The alloy raw material is the same as that used in the step of forming the bottom layer. The oxide raw material is the same as that used in the step of forming the top layer.

[0101] The ratio of alloy raw materials to oxide raw materials is determined based on the chemical composition of the gradient layer.

[0102] Specifically, after the temperature of the bottom layer drops below 250°C; preferably below 200°C, the alloy raw materials and oxide raw materials are applied to the bottom layer using a plasma spraying process to form a first gradient layer. After the temperature of the first gradient layer drops below 250°C; preferably below 200°C, the alloy raw materials and oxide raw materials are applied to the first gradient layer using a plasma spraying process to form a second gradient layer. After the temperature of the second gradient layer drops below 250°C; preferably below 200°C, the alloy raw materials and oxide raw materials are applied to the second gradient layer using a plasma spraying process to form a third gradient layer. After the temperature of the third gradient layer drops below 250°C; preferably below 200°C, the alloy raw materials and oxide raw materials are applied to the third gradient layer using a plasma spraying process to form a fourth gradient layer. After the temperature of the fourth gradient layer drops below 250°C; preferably below 200°C, the alloy raw materials and oxide raw materials are applied to the fourth gradient layer using a plasma spraying process to form a fifth gradient layer.

[0103] The parameters used to form the first to fifth gradient layers, such as main gas flow rate, spraying voltage, spraying current, spraying distance, and powder feeding rate, can be the same or different. In some embodiments, the above parameters are within the following ranges.

[0104] The main gas flow rate can be 1500-2200 L / h; preferably 1700-2000 L / h; more preferably 1900-1950 L / h.

[0105] The spraying voltage can be 50–90V; preferably 60–80V. In some embodiments, the spraying voltage is 65–70V.

[0106] The spraying current can be 400-800A; preferably 450-700A; more preferably 500-600A.

[0107] The spraying distance can be 80-200mm; preferably 100-150mm; more preferably 120-130mm.

[0108] The powder feeding rate can be 0.05 to 2 r / min; preferably 0.1 to 1.5 r / min; more preferably 0.4 to 0.6 r / min.

[0109] Steps to form the top layer

[0110] The oxide raw material is formed as the top layer on the fifth gradient layer using a plasma spraying process. Specifically, the top layer can be formed on the fifth gradient layer using a plasma spraying process after the temperature of the fifth gradient layer has dropped below 250°C; preferably, it can be formed after the temperature has dropped below 200°C.

[0111] The oxide raw material is determined based on the composition of the top layer. The oxide raw material can be a powder. Specifically, the oxide raw material can be a spherical powder. The particle size range of the oxide raw material is 15–53 μm.

[0112] The main gas flow rate can be 1500-2700 L / h; preferably 1700-2500 L / h; more preferably 2100-2300 L / h.

[0113] The spraying voltage can be 50–90V; preferably 60–80V. In some embodiments, the spraying voltage is 65–75V.

[0114] The spraying current can be 400-800A; preferably 500-700A; more preferably 600-650A.

[0115] The spraying distance can be 50-200mm; preferably 70-150mm; more preferably 90-120mm.

[0116] The powder feeding rate can be 0.1 to 4 r / min; preferably 0.3 to 0.3 r / min; more preferably 0.5 to 2 r / min.

[0117] Preprocessing steps

[0118] The mold body can be a processed mold body. Specifically, the mold body is cleaned and roughened to obtain a processed mold body.

[0119] Alcohol can be used to clean the mold body, resulting in a cleaned mold. Cleaning can remove oil and impurities from the mold body.

[0120] The outer wall of the mold body can be roughened by sandblasting. The sand used for sandblasting can be white corundum with a particle size of 24 mesh or less. The sandblasting distance can be 50-200 mm; preferably 70-150 mm.

[0121] <Applications of casting molds>

[0122] The casting mold of the present invention can reduce shrinkage cavities generated in metal ingots during the casting process. Therefore, the present invention provides the use of the above-described casting mold in the preparation of metal ingots. The metal ingot is preferably a heavy rare earth metal ingot. The heavy rare earth elements are preferably terbium and / or dysprosium.

[0123] <Metal Ingot Preparation Methods>

[0124] The method for preparing the metal ingot of the present invention includes the following steps: pouring molten metal into the casting mold of the present invention to form a metal ingot. The casting mold is as described above and will not be repeated here.

[0125] The metal melt is preferably a heavy rare earth metal melt. The heavy rare earth elements are preferably terbium and / or dysprosium.

[0126] The preparation method of the present invention can reduce shrinkage cavities in metal ingots during solidification and improve the quality of metal ingots.

[0127] The testing method is described below:

[0128] The bonding strength between the composite coating and the mold body: tested according to standard MH / T 3027-2013. The prepared specimen is placed in the upper and lower clamps of a universal testing machine and aligned, so that the bonded surface of the specimen is subjected to a vertical and uniform tensile force. The clamps are pulled apart at a certain speed until failure. The bonding strength of the coating is calculated by the load value of the specimen pull apart and the cross-sectional area of ​​the specimen coated with the tested coating.

[0129] Thermal cycling performance: Tested according to standard ISO14188:2012. A high and low temperature thermal cycling test chamber was used to test the coating samples at a specified temperature for 5 to 10 minutes, followed by air cooling and water cycling tests. The number of cycles in which the coating peeled off or cracked was recorded to evaluate the thermal cycling performance of the coating.

[0130] Shrinkage depth: The shrinkage depth is measured using a flaw detector.

[0131] Preparation Examples 1-3

[0132] The mold body (internal cavity dimensions φ110mm×80mm) was cleaned with alcohol to remove oil and impurities, resulting in a cleaned mold. The outer wall of the cleaned mold body was then roughened by sandblasting to obtain a treated mold body. The sandblasting abrasive was white corundum with a particle size of 24 mesh or less, and the blasting distance was 100mm.

[0133] The specific materials of the mold body are shown in Table 1.

[0134] Table 1

[0135]

[0136] Examples 1-3

[0137] (1) The alloy raw material is plasma sprayed to form a base layer on the outer wall of the treated mold body. The alloy raw material is spherical powder. The particle size range of the alloy raw material is 15-53 μm.

[0138] (2) After the bottom layer temperature is below 200℃, the alloy raw materials and oxide raw materials are applied to the bottom layer using a plasma spraying process to form the first gradient layer. In the first gradient layer, the chemical composition of the bottom layer accounts for 90 at%, and the chemical composition of the top layer accounts for 10 at%.

[0139] After the temperature of the first gradient layer drops below 200℃, the alloy raw materials and oxide raw materials are applied to the first gradient layer using a plasma spraying process to form a second gradient layer. In the second gradient layer, the bottom layer accounts for 70 at% of the chemical composition, and the top layer accounts for 30 at%.

[0140] After the temperature of the second gradient layer drops below 200℃, the alloy raw materials and oxide raw materials are applied to the second gradient layer using a plasma spraying process to form the third gradient layer. In the third gradient layer, the chemical composition of the bottom layer accounts for 50 at%, and the chemical composition of the top layer accounts for 50 at%.

[0141] After the temperature of the third gradient layer drops below 200℃, the alloy raw materials and oxide raw materials are applied to the third gradient layer using a plasma spraying process to form the fourth gradient layer. In the fourth gradient layer, the bottom layer accounts for 30 at% of the chemical composition, and the top layer accounts for 70 at%.

[0142] After the temperature of the fourth gradient layer drops below 200℃, the alloy raw materials and oxide raw materials are applied to the fourth gradient layer using a plasma spraying process to form the fifth gradient layer. In the fifth gradient layer, the bottom layer accounts for 10 at% of the chemical composition, and the top layer accounts for 90 at%.

[0143] The main gas flow rate, spraying voltage, spraying current, spraying distance, and powder feeding rate used to form the first to fifth gradient layers are the same. The alloy raw materials used in this step are the same as those in step (1), and the oxides used are the same as those in step (3).

[0144] (3) After the temperature of the fifth gradient layer is below 200℃, the oxide raw material is applied to the fifth gradient layer using a plasma spraying process to form the top layer, thus obtaining the casting mold. The oxide raw material is a spherical powder. The particle size range of the oxide raw material is 15~53μm.

[0145] like Figure 1 As shown, the casting molds of Examples 1-3 include a mold body 1, a bottom layer 2, a gradient layer 3, and a top layer 4. The gradient layer 3 is located between the bottom layer 2 and the top layer 4. The bottom layer 2 covers the outer wall of the mold body 1. The first gradient layer (not shown) is close to the bottom layer 2 and adheres to it. The fifth gradient layer (not shown) is close to the top layer 4 and adheres to it.

[0146] The elemental composition of the alloy raw materials is shown in Table 2, and other parameters and types of oxide raw materials are shown in Table 3. The properties of the casting mold are shown in Table 4.

[0147] Table 2

[0148] Al (wt%) Si (wt%) Ni (wt%) Fe (wt%) Co (wt%) Cr (wt%) Y(wt%) Example 1 4.5 0.35 margin — — — — Example 2 12 — margin — 23 17 0.5 Example 3 5 — — — margin 28 0.5

[0149] Table 3

[0150]

[0151]

[0152] Table 4

[0153]

[0154] Examples 4-6

[0155] Dysprosium raw material was melted in a vacuum induction melting furnace under an argon atmosphere and a pressure of 4.5 Pa to obtain molten dysprosium. The melting power was 25 kW, and the melting time was 4 min. The molten dysprosium was then poured into a casting mold to obtain dysprosium ingots.

[0156] The specific casting molds used are shown in Table 5. The shrinkage cavity depth of the metal ingots is shown in Table 5.

[0157] Table 5

[0158]

[0159] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A casting mold for a metal terbium and / or dysprosium ingot, characterized by, The casting mold comprises a mold body, a bottom layer, a gradient layer and a top layer, the gradient layer is located between the bottom layer and the top layer, and the bottom layer covers the outer wall of the mold body; The bottom layer is composed of elements as shown in the following formula: 55-75wt% Co, 20-40wt% Cr, 1-10wt% Al and 0.1-2wt% Y; The top layer is Gd2Zr2O7; The gradient layer comprises a first gradient layer, a second gradient layer, a third gradient layer, a fourth gradient layer and a fifth gradient layer which are sequentially attached, the first gradient layer is close to the bottom layer, and the fifth gradient layer is close to the top layer; The gradient layer contains the chemical composition of the bottom layer and the chemical composition of the top layer, and the content of the chemical composition of the top layer gradually increases from the first gradient layer to the fifth gradient layer; In the first gradient layer, the chemical composition of the bottom layer accounts for 80-95at%; in the second gradient layer, the chemical composition of the bottom layer accounts for 60-80at%; in the third gradient layer, the chemical composition of the bottom layer accounts for 40-60at%; in the fourth gradient layer, the chemical composition of the bottom layer accounts for 20-40at%; and in the fifth gradient layer, the chemical composition of the bottom layer accounts for 3-20at%.

2. The casting mold according to claim 1, wherein In the bottom layer, the content of Cr is 25-35wt%, the content of Al is 3-8wt%, the content of Y is 0.3-1.5wt%, and the content of Co is 60-70wt%.

3. The casting mold according to claim 1, characterized by The material of the mold body is selected from one of carbon steel, cast iron and alloy steel.

4. The casting mold according to claim 1, characterized by The thickness of the bottom layer is 80-170μm, the thickness of the gradient layer is 750-1150μm, and the thickness of the top layer is 130-200μm.

5. The method of producing a casting mold according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) forming the bottom layer on the outer wall of the mold body by using plasma spraying process on alloy raw materials; (2) forming the first to fifth gradient layers on the bottom layer by using plasma spraying process on alloy raw materials and oxide raw materials; (3) forming the top layer on the fifth gradient layer by using plasma spraying process on oxide raw materials.

6. Use of the casting mold according to any one of claims 1-4 in the preparation of metal ingots.

7. A method of producing a metal ingot, characterized by, The method comprises the following steps: casting a metal melt into the casting mold according to any one of claims 1-4.

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