Casting mold, method for producing same, use thereof, and method for producing heavy rare earth ingot

Abstract

The application discloses a casting mold, a preparation method and application thereof, and a preparation method of heavy rare earth ingot. The casting mold comprises a mold body, a transition layer and a barrier layer, the transition layer covers the inner wall of the mold body, and the barrier layer covers the transition layer; the transition layer contains one of the following element compositions: (a) Ni and Al; (b) Fe and Ni; (c) Ni, Co, Cr, Al and Y; (d) Co, Cr, Al and Y; and the barrier layer contains rare earth oxides selected from one or more of Y2O3, CeO2 and La2Ce2O7. The binding force between the coating of the casting mold and the mold body is strong, and the coating is not easy to fall off.

Description

Technical Field

[0001] This invention relates to a casting mold, its preparation method and application, and also to a method for preparing heavy rare earth ingots. Background Technology

[0002] Dysprosium / terbium targets are key materials for the vacuum deposition fabrication of high-performance grain boundary diffusion magnets. Currently, casting molds are typically made of iron, such as cast iron, carbon steel, or alloy steel. However, due to the high reactivity of dysprosium and terbium metals and the high casting temperature, the molten metal is prone to reacting and adhering to the mold during casting, resulting in lower purity of the billet and affecting its performance.

[0003] CN112725675B discloses a method for manufacturing a dysprosium / terbium target. The method involves heating an alloy mixture containing dysprosium / terbium or pure dysprosium / terbium to 1420°C or above the alloy's melting point under high vacuum or inert gas protection, followed by casting under vacuum or inert gas protection to form a billet. The billet is held at this temperature for a period of time and then slowly cooled to obtain a billet with a single hexagonal phase structure and a uniform grain structure. The billet is then deformed under inert gas or vacuum conditions. This method uses a water-cooled graphite mold as the casting mold. The purity of the target material manufactured by this method needs improvement.

[0004] CN107799253A discloses a method for manufacturing rare earth metal rotating targets, which utilizes a hydrogenation-dehydrogenation method followed by a crushing method to prepare targets with an average particle size D. 50 The rare earth metal powder has a particle size of 40–70 μm. The powder is loaded into a graphite mold in a vacuum hot-pressing sintering furnace and hot-pressed under vacuum or argon atmosphere to obtain a rare earth metal target blank. The blank is then machined and welded with a copper or stainless steel back target to obtain a rotating rare earth metal target. This method uses vacuum hot pressing to form the rare earth metal powder.

[0005] CN116121714A discloses a low surface energy, corrosion-resistant, high-entropy composite coating for a die-casting mold, comprising a gradient structure consisting of a bonding layer, a transition layer, a hardening layer, a wear-resistant layer, an aluminum melt corrosion-resistant layer, and a low surface energy aluminum-repellent layer. The bonding layer is a CrTi layer, the transition layer is a CrTiN transition metal ceramic layer, the hardening layer is a CrTiN / TiVZrNbHfCrBN high-entropy alloy nitride multilayer film, the wear-resistant layer is a TiVZrNbHfCrBN high-entropy alloy nitride layer, the aluminum melt corrosion-resistant layer is a TiVZrNbHfCrBON layer, and the low surface energy aluminum-repellent layer is a TiVZrNbHfCrBO oxide layer. This mold is a die-casting mold and is not suitable for preparing dysprosium / terbium targets. Summary of the Invention

[0006] In view of this, one object of the present invention is to provide a casting mold in which the coating has a strong bond between itself and the mold body, and the coating is not easily peeled off. Furthermore, the casting film has good heat resistance, high coating hardness, and a long service life. Even further, the casting mold can reduce impurities introduced into the heavy rare earth metals during the casting process, thereby improving the purity of the heavy rare earth ingots.

[0007] 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 adhesion between the coating and the mold body.

[0008] Another object of the present invention is to provide an application of a casting mold.

[0009] Another object of the present invention is to provide a method for preparing heavy rare earth ingots, which can improve the purity of heavy rare earth ingots.

[0010] The above objectives are achieved through the following technical solutions.

[0011] On one hand, the present invention provides a casting mold including a mold body, a transition layer and a barrier layer, wherein the transition layer covers the inner wall of the mold body and the barrier layer covers the transition layer;

[0012] The transition layer contains one of the following elemental compositions:

[0013] (a)Ni and Al;

[0014] (b)Fe and Ni;

[0015] (c) Ni, Co, Cr, Al, and Y;

[0016] (d) Co, Cr, Al, and Y;

[0017] The barrier layer contains rare earth oxides, which are selected from one or more of Y2O3, CeO2, and La2Ce2O7.

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

[0019] In elemental composition (b), the Fe content is 30–70 wt% and the Ni content is 30–70 wt%.

[0020] In the elemental composition (c), 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%.

[0021] In the elemental composition (d), 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%.

[0022] According to the casting mold of the present invention, preferably, the elemental composition (a) further contains 0.05 to 0.8 wt% Si.

[0023] 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.

[0024] According to the casting mold of the present invention, preferably, the thickness of the transition layer is 80-170 μm and the thickness of the barrier layer is 180-300 μm.

[0025] According to the casting mold of the present invention, preferably, the thickness of the transition layer is 100-150 μm and the thickness of the barrier layer is 190-250 μm.

[0026] On the other hand, the present invention provides a method for preparing the above-mentioned casting mold, comprising the following steps:

[0027] (1) The alloy raw materials are used to form a transition layer on the inner wall of the mold body by plasma spraying process;

[0028] (2) A barrier layer is formed on the transition layer by using a plasma spraying process to apply rare earth oxide raw materials.

[0029] According to the preparation method of the present invention, preferably, in step (1), the alloy raw material is spherical powder, the main gas flow rate is 1300~2200L / h, the spraying voltage is 40~80V, the spraying current is 400~800A, the spraying distance is 100~250mm, and the powder feeding rate is 0.05~1r / min;

[0030] In step (2), the rare earth oxide raw material is spherical powder, the main gas flow rate is 1500~2700L / h, the spraying voltage is 50~90V, the spraying current is 400~800A, the spraying distance is 50~200mm, and the powder feeding rate is 0.1~4r / min.

[0031] In another aspect, the present invention provides the use of the above-mentioned casting mold in the preparation of heavy rare earth ingots.

[0032] In another aspect, the present invention provides a method for preparing heavy rare earth ingots, comprising the following steps:

[0033] The molten heavy rare earth metal is poured into the casting mold mentioned above.

[0034] The coating of the casting mold of this invention has strong adhesion to the mold body, and the coating is not easily peeled off. The casting film of this invention has good heat resistance, high coating hardness, and long service life. The casting mold of this invention can reduce impurities introduced into heavy rare earth metals during the casting process and improve the purity of heavy rare earth ingots. The preparation method of this invention can improve the density of the coating and the adhesion between the coating and the mold body. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a casting mold according to the present invention.

[0036] The detailed labeling in the attached figures is as follows:

[0037] 1-Mold body; 2-Transition layer; 3-Barrier layer. Detailed Implementation

[0038] 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.

[0039] The "coating" mentioned in this invention refers to a composite coating formed by a transition layer and a barrier layer.

[0040] <Casting mold>

[0041] The casting mold of the present invention includes a mold body, a transition layer, and a barrier layer. The transition layer covers the inner wall of the mold body. The barrier layer covers the transition layer.

[0042] The material of the mold body is selected from one or more of carbon steel, cast iron, and alloy steel.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The transition layer consists of one of the following elements:

[0054] (a)Ni and Al;

[0055] (b)Fe and Ni;

[0056] (c) Ni, Co, Cr, Al, and Y;

[0057] (d) Co, Cr, Al and Y.

[0058] In elemental composition (a), the Al content is 0.5 to 10 wt%; preferably 2 to 8 wt%; more preferably 3 to 6 wt%.

[0059] In elemental composition (a), the Ni content is 85–99.5 wt%; preferably 90–98 wt%; more preferably 94–96 wt%.

[0060] 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%.

[0061] In elemental composition (b), the Fe content is 30–70 wt%; preferably 40–60 wt%; more preferably 45–55 wt%.

[0062] In elemental composition (b), the Ni content is 30–70 wt%; preferably 40–60 wt%; more preferably 45–55 wt%.

[0063] In the elemental composition (c), the Cr content is 10-25 wt%; preferably 12-22 wt%; more preferably 15-20 wt%.

[0064] In the elemental composition (c), the Al content is 5-20 wt%; preferably 8-15 wt%; more preferably 10-13 wt%.

[0065] 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%.

[0066] In the elemental composition (c), the Co content is 15-30 wt%; preferably 20-28 wt%; more preferably 23-25 ​​wt%.

[0067] In the elemental composition (c), the Ni content is 35-60 wt%; preferably 40-55 wt%; more preferably 45-50 wt%.

[0068] In the elemental composition (d), the Cr content is 20-40 wt%; preferably 25-35 wt%; more preferably 28-30 wt%.

[0069] In the elemental composition (d), the Al content is 1 to 10 wt%; preferably 3 to 8 wt%; more preferably 5 to 7 wt%.

[0070] In the elemental composition (d), the Y content is 0.1–2 wt%; preferably 0.3–1.5 wt%; more preferably 0.5–1 wt%.

[0071] In the elemental composition (d), the Co content is 55-75 wt%; preferably 60-70 wt%; more preferably 65-68 wt%.

[0072] In some implementations, the transition layer is composed of elements as shown in one of the above examples.

[0073] The thickness of the transition layer can be 80–170 μm; preferably 100–150 μm; more preferably 140–150 μm.

[0074] The barrier layer comprises rare earth oxides. In some embodiments, the barrier layer is formed of rare earth oxides. The rare earth oxides are selected from one or more of Y₂O₃, CeO₂, and La₂Ce₂O₇.

[0075] The thickness of the barrier layer can be 180–300 μm; preferably 190–250 μm. In some embodiments, the thickness of the barrier layer is 200–220 μm.

[0076] In some implementations, the transition layer and the barrier layer may be selected from a combination of one of the following:

[0077] (A) The transition layer contains Ni, Si and Al, and the barrier layer contains Y2O3.

[0078] (B) The transition layer contains Fe and Ni, and the barrier layer contains CeO2.

[0079] (C) The transition layer contains Ni, Co, Cr, Al and Y, and the barrier layer contains La2Ce2O7.

[0080] <Preparation Method of Casting Mold>

[0081] The method for preparing the casting mold of the present invention includes the following steps: (1) forming a transition layer; and (2) forming a barrier layer. In some embodiments, a pretreatment step is also included.

[0082] Steps to form a transition layer

[0083] The alloy raw materials are used to form a transition layer on the inner wall of the mold body using a plasma spraying process.

[0084] The elemental composition of the alloy raw material is determined based on the elemental composition of the transition layer. 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.

[0085] The main gas flow rate can be 1300-2200 L / h; preferably 1500-2000 L / h; more preferably 1750-1900 L / h.

[0086] The spraying voltage can be 40–80V; preferably 50–70V. In some embodiments, the spraying voltage is 55–60V.

[0087] The spraying current can be 400-800A; preferably 450-700A; more preferably 500-600A.

[0088] The spraying distance can be 100-250mm; preferably 120-200mm; more preferably 150-170mm.

[0089] 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.

[0090] Steps to form a barrier layer

[0091] A barrier layer is formed on the transition layer using a plasma spraying process on rare earth oxide raw materials. Specifically, the transition layer temperature can be below 250°C; preferably, it can be below 200°C.

[0092] The rare earth oxide raw material is determined based on the composition of the transition layer. The rare earth oxide raw material can be a powder. Specifically, the rare earth oxide raw material can be spherical powder. The particle size range of the rare earth oxide raw material is 15–53 μm.

[0093] The main gas flow rate can be 1500-2700 L / h; preferably 1700-2500 L / h; more preferably 1900-2300 L / h.

[0094] The spraying voltage can be 50–90V; preferably 60–80V. In some embodiments, the spraying voltage is 65–75V.

[0095] The spraying current can be 400-800A; preferably 500-700A; more preferably 550-650A.

[0096] The spraying distance can be 50-200mm; preferably 70-150mm; more preferably 90-120mm.

[0097] 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.

[0098] Preprocessing steps

[0099] The mold body can be a processed mold body. Specifically, the mold body is cleaned and roughened to obtain a processed mold body.

[0100] Alcohol can be used to clean the mold body, resulting in a cleaned mold. Cleaning can remove oil and impurities from the mold body.

[0101] The inner 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.

[0102] <Applications of casting molds>

[0103] The casting mold of the present invention can overcome the problems of reaction and adhesion between heavy rare earth melt and mold, reduce the introduction of impurities during casting, and facilitate the demolding of heavy rare earth ingots. Therefore, the present invention provides the use of the above-mentioned casting mold in the preparation of heavy rare earth ingots. The heavy rare earth is preferably one or more of terbium or dysprosium.

[0104] <Preparation Method of Heavy Rare Earth Ingots>

[0105] The method for preparing heavy rare earth ingots according to the present invention includes the following steps: casting molten heavy rare earth metal into a casting mold of the present invention to form a heavy rare earth ingot. The casting mold is as described above and will not be repeated here.

[0106] The heavy rare earth metal elements in the heavy rare earth metal melt can be selected from one or more of terbium or dysprosium.

[0107] The preparation method of this invention can reduce impurities introduced during the casting process, resulting in high-purity heavy rare earth ingots. These ingots can be further processed to obtain heavy rare earth targets. The testing methods are described below:

[0108] The bonding strength between the 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.

[0109] Hardness of the coating: Tested according to standard GB / T 9790-1988. Prepare a metallographic specimen, apply the specified test force, slowly and vertically press the indenter into the specimen surface and hold for 10-20 seconds. After removing the indenter, measure the diagonal length of the indentation with a microscope, calculate the hardness value, and repeat the test 10 times and take the average value.

[0110] 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.

[0111] Test methods for purity and impurity elements of dysprosium raw materials and dysprosium targets: The total rare earth content of dysprosium raw materials and dysprosium targets shall be determined in accordance with GB / T14635. The test for rare earth impurities shall be in accordance with GB / T18115, and the test for non-rare earth impurities shall be in accordance with GB / T12690.

[0112] Examples 1-3

[0113] (1) Clean the mold body with alcohol to remove oil and impurities, resulting in a cleaned mold. Roughen the inner wall of the cleaned mold body by sandblasting to obtain a treated mold body. The sand used for sandblasting is white corundum with a particle size of 24 mesh or less, and the sandblasting distance is 100 mm.

[0114] The alloy raw material is used to form a transition layer on the inner wall of the treated mold body using a plasma spraying process. The alloy raw material is a spherical powder with a particle size range of 15–53 μm.

[0115] (2) After the temperature of the transition layer is below 200℃, a barrier layer is formed on the transition layer using a plasma spraying process to obtain the casting mold. The rare earth oxide raw material is a spherical powder. The particle size range of the rare earth oxide raw material is 15~53μm.

[0116] like Figure 1 As shown, the casting molds of Examples 1-3 include a mold body 1, a transition layer 2, and a barrier layer 3. The transition layer 2 covers the inner wall of the mold body 1. The barrier layer 3 covers the transition layer 2.

[0117] The specific materials of the mold body are shown in Table 1. The specific elemental composition of the alloy raw materials is shown in Table 2, and other parameters, rare earth oxide raw material types, etc., are shown in Table 3. The performance of the casting mold is shown in Table 4.

[0118] Table 1

[0119]

[0120] Table 2

[0121] Al (wt%) Si (wt%) Ni (wt%) Fe (wt%) Co (wt%) Cr (wt%) Y(wt%) Example 1 4.5 0.35 margin — — — — Example 2 — — 50 50 — — — Example 3 12 — margin — 23 17 0.5

[0122] Table 3

[0123]

[0124] Table 4

[0125]

[0126] Examples 4-6

[0127] 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.

[0128] The purity and impurity element content of dysprosium raw materials, the casting molds used in each embodiment, and the purity and some impurity element content of dysprosium ingots are shown in Table 5.

[0129] Table 5

[0130]

[0131] Example 7

[0132] After casting 10 times using the casting mold of Example 1 according to the preparation method of Example 4, no peeling was observed on the coating of the casting mold.

[0133] Example 8

[0134] After the casting mold of Example 2 was used to perform 12 cyclic castings according to the preparation method of Example 5, the coating of the casting mold did not peel off.

[0135] Example 9

[0136] After the casting mold of Example 3 was used to perform 15 cycles of casting according to the preparation method of Example 6, the coating on the casting mold did not peel off.

[0137] 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 casting dysprosium or terbium, characterized in that, The casting mold includes a mold body, a transition layer, and a barrier layer. The transition layer covers the inner wall of the mold body, and the barrier layer covers the transition layer. The transition layer and the barrier layer are selected from one of the following combinations: (A) The transition layer contains 85–99.5 wt% Ni, 0.05–0.8 wt% Si and 0.5–10 wt% Al, and the barrier layer is Y2O3; (B) The transition layer contains 30-70 wt% Fe and 30-70 wt% Ni, and the barrier layer is CeO2; (C) The transition layer contains 35-60 wt% Ni, 15-30 wt% Co, 10-25 wt% Cr, 5-20 wt% Al and 0.1-2 wt% Y, and the barrier layer is La2Ce2O7; The material of the mold body is selected from carbon steel, cast iron, and alloy steel.

2. The casting mold according to claim 1, characterized in that: In (A), the transition layer contains 2–8 wt% Al, 90–98 wt% Ni, and 0.1–0.6 wt% Si. In (B), the transition layer contains 40–60 wt% Fe and 40–60 wt% Ni. In (C), the transition layer contains 12–22 wt% Cr, 8–15 wt% Al, 0.3–1.5 wt% Y, 20–28 wt% Co, and 40–55 wt% Ni.

3. The casting mold according to claim 1, characterized in that, The thickness of the transition layer is 80–170 μm, and the thickness of the barrier layer is 180–300 μm.

4. The casting mold according to any one of claims 1 to 3, characterized in that, The thickness of the transition layer is 100–150 μm, and the thickness of the barrier layer is 190–250 μm.

5. The method for preparing a casting mold according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) The alloy raw materials are used to form a transition layer on the inner wall of the mold body by plasma spraying process; (2) A barrier layer is formed on the transition layer by using a plasma spraying process to apply rare earth oxide raw materials.

6. The preparation method according to claim 5, characterized in that: In step (1), the alloy raw material is spherical powder, the main gas flow rate is 1300~2200L / h, the spraying voltage is 40~80V, the spraying current is 400~800A, the spraying distance is 100~250mm, and the powder feeding rate is 0.05~1r / min; In step (2), the rare earth oxide raw material is spherical powder, the main gas flow rate is 1500~2700L / h, the spraying voltage is 50~90V, the spraying current is 400~800A, the spraying distance is 50~200mm, and the powder feeding rate is 0.1~4r / min.

7. The use of the casting mold according to any one of claims 1 to 4 in the preparation of heavy rare earth ingots.

8. A method for preparing heavy rare earth ingots, characterized in that, Includes the following steps: The heavy rare earth metal molten material is poured into the casting mold as described in any one of claims 1 to 4.

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