阅读说明：本技术 一种用于稀土合金烧结热处理的烧结容器及其制备方法 (Sintering container for rare earth alloy sintering heat treatment and preparation method thereof ) 是由 黄风 付松 章兆能 于光照 满超 孙国强 于 2021-08-31 设计创作，主要内容包括：本发明提供了一种用于稀土合金烧结热处理的烧结容器及其制备方法：在待处理的烧结容器中,放入含有稀土元素的稀土铁基合金,所述合金中稀土元素的质量含量为10～50wt％,加热到800～1000℃,真空度小于10～(-2)pa的真空环境下,保温4-10小时,稀土元素挥发在烧结容器的内表面上形成一层含有稀土元素的保护膜,冷却后制得所述用于稀土合金烧结热处理的烧结容器。保护膜中,稀土元素的总含量为28～90wt％。本发明提供的保护膜杜绝了稀土与烧结盒内壁不可控的反应,阻止容器元素和稀土元素相互扩散交换,也可以吸收杂质元素防止污染。由此保证了磁体的表面元素和内芯元素的一致性,提高烧结磁体的性能。(The invention provides a sintering container for rare earth alloy sintering heat treatment and a preparation method thereof, wherein the sintering container comprises the following steps: putting a rare earth iron-based alloy containing rare earth elements into a sintering container to be treated, wherein the mass content of the rare earth elements in the alloy is 10-50 wt%, heating to 800-1000 ℃, and the vacuum degree is less than 10 ‑2 pa, keeping the temperature for 4-10 hours in a vacuum environment, volatilizing the rare earth element to form a layer of protective film containing the rare earth element on the inner surface of the sintering container, and cooling to obtain the sintering container for sintering heat treatment of the rare earth alloy. In the protective film, the total content of rare earth elements is 28-90 wt%. The protective film provided by the invention prevents the uncontrollable reaction of rare earth and the inner wall of the sintering box, prevents the mutual diffusion and exchange of container elements and rare earth elements, and can absorb impurity elements to prevent pollution. Therefore, the consistency of the surface elements and the inner core elements of the magnet is ensured, and the performance of the sintered magnet is improved.)

1. A preparation method of a sintering container for rare earth alloy sintering heat treatment is characterized by comprising the following steps: putting a rare earth iron-based alloy containing rare earth elements into a sintering container to be treated, wherein the mass content of the rare earth elements in the rare earth iron-based alloy is 10-50 wt%, heating to 800-1000 ℃, and the vacuum degree is less than 10^-2pa, keeping the temperature for 4-10 hours in a vacuum environment, volatilizing the rare earth element in the rare earth iron-based alloy to form a layer of protective film containing the rare earth element on the inner surface of the sintering container, cooling, taking out the rare earth iron-based alloy, and obtaining the sintering container for sintering heat treatment of the rare earth alloy.

2. The method according to claim 1, wherein the total content of the rare earth elements in the protective film containing the rare earth elements is 28 to 90 wt%.

3. The method according to claim 1, wherein the rare earth element is one or a mixture of two or more of La, Ce, Pr, Nd, Ho, Gd, Dy and Tb.

4. The method according to claim 1, wherein the protective film has a thickness of 0.1 to 0.5 mm.

5. The method of claim 1, wherein the rare earth-iron based alloy has a composition of: 10-50 wt% of rare earth elements, 45-90 wt% of iron and 0-5 wt% of X, wherein X represents various metal elements, non-metal element components and inevitable trace impurities.

6. The method according to claim 1, wherein the rare earth iron-based alloy is used in an amount of 60 to 100% by volume in a sintering container filled with the rare earth iron-based alloy to be treated.

7. The method according to claim 1, wherein the rare earth-iron based alloy contains 15 to 35% by mass of a rare earth element.

8. The method according to claim 1, wherein the sintered container is prepared for sintering the rare earth alloy such that the protective film becomes thinner or comes off in use, and the individual area of the exposed portion of the inner surface of the sintered compact body from which the protective film comes off is larger than 1cm²Then, the sintered container with the protective film is prepared again according to the above method.

9. A sintering vessel for rare earth alloy sintering heat treatment produced by the method according to any one of claims 1 to 8, wherein the inner wall surface of the sintering vessel is covered with a protective film containing a rare earth element, and the total content of the rare earth element in the protective film is 28 to 90 wt%.

10. Use of the sintering container for rare earth alloy sintering heat treatment according to claim 9 in rare earth alloy sintering heat treatment.

Technical Field

The invention relates to the field of rare earth alloy manufacturing, in particular to a sintering heat treatment container used in sintering heat treatment and a preparation method thereof.

Background

During the sintering heat treatment process of the rare earth alloy containing rare earth elements, because rare earth is easy to volatilize and diffuse and the alloy melting point is low, the rare earth alloy is easy to react with a sintering heat treatment container (sintering heat treatment box) in the sintering heat treatment process and even can be adhered together to form an element diffusion channel, under the action of concentration gradient, the rare earth elements in the rare earth alloy can enter the sintering heat treatment container, meanwhile, elements in the sintering container, such as carbon in a graphite box and iron in an iron sheet box can also enter the rare earth alloy, so that the composition and microstructure of the alloy surface layer are changed, the performance is degraded, the surface layer needs to be removed through grinding and the like, and energy and raw materials are wasted.

Disclosure of Invention

The invention aims to solve the technical problem that the change performance of alloy components is deteriorated due to mutual diffusion of container elements and rare earth elements when a sintering container is used for sintering and heat treating rare earth alloy.

The technical scheme adopted by the invention is as follows:

a preparation method of a sintering container for rare earth alloy sintering heat treatment comprises the following steps: putting a rare earth iron-based alloy containing rare earth elements into a sintering container to be treated, wherein the mass content of the rare earth elements in the rare earth iron-based alloy is 10-50 wt%, heating to 800-1000 ℃, and the vacuum degree is less than 10^-2pa, keeping the temperature for 4-10 hours in a vacuum environment, volatilizing the rare earth element in the rare earth iron-based alloy to form a layer of protective film containing the rare earth element on the inner surface of the sintering container, cooling, taking out the rare earth iron-based alloy, and obtaining the sintering container for sintering heat treatment of the rare earth alloy.

In the rare earth element-containing protective film, the total content of rare earth elements is 28-90 wt%.

The rare earth element is one or more of La, Ce, Pr, Nd, Ho, Gd, Dy and Tb, and is preferably a mixture of Pr, Nd, Ho, Gd, Dy and Tb.

The thickness of the protective film is 0.1-0.5 mm.

The rare earth iron-based alloy comprises the following components: 10-50 wt% of rare earth elements, 45-85 wt% of iron and 0-5 wt% of X, wherein X represents various metal elements and non-metal element components and inevitable trace impurities, such as Co, Al, Cu, Ga, B, Zr, Si, Mn, Nb, Ti, Cr, Hf and the like, and 0 represents infinitely close to 0 but not 0.

Preferably, the rare earth iron-based alloy comprises the following components: 15-35 wt% of rare earth elements, 60-84 wt% of iron, 0.01-5 wt% of X,

the rare earth iron-based alloy is an alloy sheet or alloy powder, various forms are suitable for the invention, and the form of the alloy has no influence on the preparation method and the prepared protective film.

The invention can use the normally qualified rare earth iron-based alloy, and can also use defective products caused by non-component impurities in the production process of the rare earth alloy, such as sintering defective products, defective products with unqualified microstructures in melt-throwing and the like. After the used rare earth iron-based alloy is used for preparing the protective film, the rare earth iron-based alloy can be reused in the invention as long as the mass content of the rare earth element still meets the requirement of 10-50 wt%.

The rare earth iron-based alloy is generally used in an amount of 60 to 100% (preferably 60 to 80%, more preferably two thirds) by volume, and when the sintering container to be treated is a rectangular parallelepiped or a cylinder, the rare earth iron-based alloy is generally filled in the sintering container to be treated to a height of 60 to 100% (preferably 60 to 80%, more preferably two thirds).

The prepared protective film is a mixture of multiple elements including rare earth elements, iron elements, carbon elements, oxygen elements, other metal elements, non-metal elements, inevitable impurities and the like, wherein the rare earth elements exist in the form of rare earth oxides, rare earth carbides and rare earth alloy mixtures. In the protective film, the total content of the rare earth elements reaches more than 28 wt%, so that the protective effect can be achieved, and the components or contents of other elements have no influence on the protective effect of the protective film.

The total content of the rare earth elements in the protective film refers to the mass ratio of the total mass of all the rare earth elements in the mixture of the rare earth oxide, the rare earth carbide and the rare earth alloy in the protective film to the total mass of the protective film.

The invention also provides a sintering container for the rare earth alloy sintering heat treatment prepared by the method, which can be used for the rare earth alloy sintering heat treatment, and can reduce the atom exchange between the sintering container and the rare earth alloy and avoid the mutual interference between the container and the rare earth alloy when the rare earth alloy is sintered.

The inner wall surface of the sintering container is covered with a layer of protective film containing rare earth elements, and the total content of the rare earth elements in the protective film is 28-90 wt%.

After the sintering container with the protective film is used for sintering heat treatment of rare earth alloy, the protective film can be thinned or fall off after multiple times of sintering use, and when the protective film is used for sintering heat treatment of rare earth alloyThe single area of the protective film falling to the exposed position of the inner surface of the sintering box body is more than 1cm²In this case, the treatment is carried out again, i.e., the sintered container having the protective film is newly prepared by the method of the present invention. When the treatment is carried out again, the protective film may be prepared again after the inner surface is sandblasted, or the protective film may be directly prepared without treatment.

In the rare earth iron-based alloy, the mass content of the rare earth element is 10-50%, preferably 15-35%.

The content can ensure that the interior of the sintering container is covered with the protective film, the content of the rare earth element cannot be too high, and the alloy is melted due to the excessively high content of the rare earth element and is welded with the sintering container.

In addition, the temperature during treatment cannot be too high, and the excessive temperature can also cause alloy melting and welding of the sintering container, so that the sintering container cannot be used.

In the present invention, the sintering container is a container for containing an alloy material in a sintering furnace when sintering a rare earth alloy, and is generally a box made of graphite, iron, molybdenum or the like, and generally has a rectangular parallelepiped shape.

The invention uses the alloy rich in rare earth to pre-evaporate a layer of rare earth metal film on the sintering box, the rare earth content in the protective film is high, and the protective film exists in the form of oxide and carbide of rare earth metal, then the sintering box covered with the rare earth metal protective film is used for sintering and heat-treating the rare earth alloy magnet, the protective film prevents the uncontrollable reaction of rare earth and the inner wall of the sintering box, prevents the mutual diffusion and exchange of container elements and rare earth elements, and can also absorb impurity elements in the sintering environment to prevent pollution. The rare earth oxide or metal on the protective film can not oxidize to pollute the magnet, namely the rare earth oxide can not continuously oxidize rare earth, thereby ensuring the consistency of surface elements and inner core elements of the magnet and improving the performance of the sintered magnet. In addition, the protective film can be prepared by using sintering defective products in the production process of rare earth metals or defective products of microstructures during melt-throwing, raw materials do not need to be purchased additionally, the production defective products are recycled, the cost is low, the method is simple and convenient, and the industrial popularization and use are facilitated.

Detailed Description

The technical solution of the present invention is further described with specific examples, but the scope of the present invention is not limited thereto.

Example 1

Placing rare earth iron-based alloy powder with a height of 4 cm into a graphite sintering box (size 28 × 18 × 6cm), wherein the percentage content of elements in the alloy is shown in Table 1, heating to 1000 deg.C, and vacuum degree is less than 10^-2pa, keeping the temperature for 6 hours in a vacuum environment, forming a layer of protective film containing rare earth elements on the inner surface of the sintering container through volatilization of rare earth, cooling, and taking out alloy powder to obtain the treated sintering container. The ICP composition analysis and carbon oxygen analysis results of the obtained protective film are shown in table 1. The film thickness was about 0.5 mm.

Example 2

Two thirds of the volume of rare earth iron-based alloy (the source is ingot casting particles after breaking Nd-Fe-B rapid hardening belt) is put into a graphite sintering box (the size is 28 multiplied by 18 multiplied by 6cm), the percentage content of elements in the alloy is shown in Table 1, the alloy is heated to 1000 ℃, and the vacuum degree is less than 10^-2pa, keeping the temperature for 8 hours in a vacuum environment, forming a layer of protective film containing rare earth elements on the inner surface of the sintering container through volatilization of rare earth, and cooling to obtain the treated sintering container. The ICP composition analysis and carbon oxygen analysis results of the obtained protective film are shown in table 1.

TABLE 1 elemental analysis results of rare earth Fe-based alloys and rare earth volatilized internal surface protective films of sintering boxes

Example 3

(1) Preparing magnet raw materials according to the nominal composition of the magnet in the table 2, placing the magnet raw materials in a vacuum intermediate frequency rapid hardening induction furnace, vacuumizing the furnace to below 1Pa, preheating the magnet raw materials in 120kW, vacuumizing the furnace to below 1Pa, and raising the vacuum degree; argon is filled to 0.05MPa, then smelting is carried out at 1500 ℃, and the molten liquid is poured onto a cooling copper roller with a free surface cooling device to obtain an alloy sheet with the thickness of 0.3 mm; placing the alloy sheet in a hydrogen crushing furnace, and crushing the alloy sheet into alloy powder of 200 mu m through low-temperature hydrogen absorption and high-temperature dehydrogenation reaction; mixing the alloy powder evenly, grinding the alloy powder into magnetic powder through a jet mill process, and screening out the alloy powder with the average grain size of 3 mu m;

table 2 magnet formulation weight fraction (%)

PrNd	B	Fe	Al	Co	Cu	Ga	Zr
								31	0.92	66.63	0.1	0.5	0.3	0.4	0.15

(2) Uniformly mixing the magnetic powder, carrying out orientation compression molding under the condition that the magnetic field intensity is 2.0T, and carrying out vacuum packaging to obtain a green body with the density of 4.0g/cm 3;

(3) placing the green bodies in three sintering boxes respectively

1. Ordinary sand-blasting treated graphite sintering box

2. Graphite sintering Cartridge obtained in example 1

3. Example 2 the resulting graphite sintering Cartridge

Putting the sintering box into a vacuum sintering furnace, and vacuumizing for 1 multiplied by 10^-2Heating and sintering at a temperature below Pa, keeping the temperature at 300 ℃ for 1h and 600 ℃ for 2h respectively in the heating process, keeping the temperature at 850 ℃ for 4.5h, adjusting the sintering temperature to 1055 ℃, keeping the temperature for 4.5h, filling argon, and cooling by air below 150 ℃;

(3) in vacuum of 1X 10^-2Performing two-stage tempering treatment below Pa; tempering at 900 deg.C for 3h, introducing argon gas, and air cooling below 150 deg.C; tempering at 485 deg.c for 5 hr, and introducing argon to cool below 70 deg.c.

The magnet was polished by a double-ended grinding machine, the thickness of the magnet was 1mm on all six faces, the magnetic properties before and after polishing of the magnet surface were measured by NIM62000, and the carbon-oxygen contents of the skin and core (depth of 3mm below the skin) were measured by an oxygen-nitrogen analyzer and a carbon analyzer, and the results obtained are shown in Table 3 below.

TABLE 3

The comparative example is a common untreated graphite sintering box.

Table 3 the results show that the magnet sintered from the conventional graphite cartridge had poor magnetic properties and significantly deteriorated before polishing to remove the 1mm surface layer, and the magnetic properties after polishing were improved, but still not as good as the magnet sintered from the graphite cartridge with the protective film prepared in this application.

By using the sintering box of the invention, the performance change before and after the surface layer is removed is not large, and the square degree is obviously higher than that of a comparative example.

From the carbon-oxygen contents of the skin and the core, the carbon-oxygen content of the skin of the comparative example is about 1.5-2 times of that of the core, while the difference between the oxygen-carbon contents of the skin and the core of the examples 1 and 2 is small and is obviously lower than that of the comparative example 1, which shows that in the sintering process, atomic diffusion exchange occurs between the inner wall of the untreated graphite box and the magnet, so that the carbon-oxygen content of the surface of the magnet is increased, and the performance of the magnet is also deteriorated. In addition, impurities are easy to pollute products during sintering, for example, a certain amount of organic lubricant is added in the process of magnet powder and compression molding, the organic lubricant volatilizes during sintering, a part of the organic lubricant is deposited on the surface of the graphite box, and the organic lubricant reversely enters the blank again at high temperature. Some organic matters can be adsorbed in the inner lining of the sintering furnace and released at high temperature to pollute products. After the surface is covered with the protective film, the uncontrollable reaction of the rare earth and the inner wall of the sintering box is prevented, the impurity oxidation pollution can also be prevented, and the protective film can be used for sacrificial absorption of impurities and product protection. The rare earth oxide or metal of the protective film can not oxidize and pollute the magnet, the carbon and oxygen content on the surface of the magnet is well controlled, and the magnetic performance of the magnet is improved.

Example 4

After 10 uses of the graphite sintering box of example 1, it was found that a single area of the exposed point of the inner surface of the sintering box body was more than 1cm²When reprocessing is required

Upon reprocessing, a protective film was prepared in the same manner as in example 1 to obtain a processed sintered container. The ICP composition analysis and carbon oxygen analysis results of the obtained protective film are shown in table 4. The film thickness was about 0.5 mm.

TABLE 4

The magnetic properties before and after the surface grinding of the magnet, and the results of the carbon oxygen content of the skin and the core (depth of 3mm below the skin) were shown in Table 5 below.

TABLE 5

Therefore, after the protective film of the sintering box is used and falls off for many times, the protective film can be prepared again, and the protective performance of the protective film is not influenced. Namely, the protective film of the sintering box of the present invention can be repeatedly prepared.