KR0169882B1 - The process of rare earth permanent magnetic and alloy powder by hydrogenation and hot deformation - Google Patents

Abstract

The present invention relates to a novel process for the preparation of rare earth permanent magnets and alloy powders by hot deformation during dehydrogenation and recombination after hydrogenation (Hydrogenatin), by improving the conventional HDDR method, such as Co, Zr, Ga, Nb The present invention relates to a method for producing anisotropic metal powders used for relatively high energy resin magnets without the addition of an alloying element. The process of desorption and initial release of hydrogen in the manufacture of rare earth permanent magnets using hydrogen Strong anisotropic rare earth magnet characterized by applying hot deformation such as hot-pressing and die-upsetting to the alloy during recombination back to the crystal structure Or a method for producing an alloy powder.

Description

Manufacturing method of rare earth permanent magnet and alloy powder by hydrogenation and hot deformation

1 is a process schematic diagram illustrating a method for producing a rare earth alloy powder using hydrogen.

2 is a crystal structure of the rare earth-based alloy powder of the present invention.

3 is an embodiment of a hot pressing device for making a permanent magnet of high energy using the rare earth-based alloy powder of the present invention.

* Explanation of symbols for main parts of the drawings

10: rare earth alloy 20: mold (MOLD)

30: punch 40: heating device

50: chamber

The present invention relates to a method for producing a rare earth alloy powder using hydrogenation and dehydrogenation reactions, which are attracting attention as a novel process for rare earth permanent magnets (particularly, Nd-Fe-B magnets).

In general, the preparation of rare earth-based alloys using hydrogenation and dehydrogenation is called HDDR process (Hydrogenation-Disproportionation-Desorptionecombination PROCESS), and this HDDR process is composed of four steps. Referring to the ternary alloy of as an example as shown in FIG.

That is, when the Nd-Fe-B alloy is exposed to hydrogen at low temperature, it reacts with the Nd ₂ Fe ₁₄ B phase and hydrogen in the alloy to form Nd ₂ Fe ₁₄ BH _2.7 and NdH _2.7 phase, respectively. At this time, hydrogen in each phase exists as an invasive element, and its amount increases with reaction temperature or pressure. At temperatures above 700 ° C., the Nd ₂ Fe ₁₄ B phase is separated into Fe, Fe ₂ B and NdH _2.2 phases, and the Nd-rich phase becomes NdH _2.2 (Disproportionation).

By this alloy as a separate heat treatment in the temperature and vacuum over 85 ℃ while emitting the absorbed hydrogen Nd ₂ Fe ₁₄ B is on the nucleus is generated and recombined into a fine crystal phase Nd ₂ Fe ₁₄ B (Recombination).

The Nd-Fe-B-based alloy obtained in this manner can easily obtain a high coercive powder due to very fine grains and cracks generated during hydrogen absorption. In the case of the Nd-Fe-B alloy system, the anisotropy of the powder produced by the above HDDR method in the Nd-Fe-B three-dimensional alloy is very poor, but Co, Zr, Ga, Nb, etc. The powder is made anisotropic by the addition of the anisotropic coarsening element, thereby making it possible to manufacture a high-energy resin magnet.

However, the conventional HDDR method, which is an anisotropic powder manufacturing method using hydrogen, is mainly used as a method for producing an isotropic or anisotropic alloy powder for resin magnets. At this time, after the HDDR process, a manufacturing process such as pulverization, resin compounding, curing, etc. for powder production is additionally required. In addition, a high energy magnet may be manufactured by hot deformation and sintering after grinding, in which case a series of hot deformation or sintering processes are required in addition to the HDDR process. Therefore, the HDDR body alone cannot directly produce high energy anisotropic bulk magnets, and the manufacture of rare earth magnets by HDDR is complicated and difficult to manage, which is relatively difficult compared to the conventional sintering and quench solidification methods. Uneconomical

In addition, in the case of Nd-Fe-B-based alloys, anisotropic alloy powders are obtained by adding anisotropic coarse alloying elements, such as Co, Zr, Ga, and Nb, during the production of anisotropic powders. Therefore, an expensive alloying element is required and the manufacturing process is complicated and the manufacturing cost is high, such as the amount must be adjusted appropriately. In addition, the degree of anisotropy is determined by the composition of the alloy, there was a disadvantage that the alloy system capable of obtaining anisotropic powder by the HDDR method is an extremely limited alloy system containing some anisotropic element.

The present invention relates to the Nd-Fe-B-based alloy in the process of releasing hydrogen at high temperature during the manufacture of the rare earth alloy powder using hydrogen (Desorption) and returning to the initial composition and crystal structure (Recombination). Hot deformation is applied by applying hot deformation such as hot-pressing and die-upsetting, and at this stage, high-energy magnets are directly manufactured.

In addition, according to the present invention, it is possible to produce an anisotropic alloy powder for use in a relatively high energy resin magnet without adding an alloy element that promotes anisotropy. FIG. 3 shows hydrogen can be injected into a hot pressing apparatus that can be used in the present invention, and hot pressing can be performed in a vacuum atmosphere.

Referring to the present invention, an Nd-Fe-B magnet is described as follows.

The magnetic properties of Nd-Fe-B magnets are due to the presence of the Nd ₂ Fe ₁₄ B phase, which is a ternary intermetallic compound. As shown in FIG. 2, the crystal structure of the Nd ₂ Fe ₁₄ B phase is composed of 68 elements per unit lattice, and has four unit units per unit lattice. Nd ₂ Fe ₁₄ B phase has a tetragonal structure and has an easy magnetization axis that is easily magnetized to the c-axis. In the Nd ₂ Fe ₁₄ B phase, Nd and Fe are concentrated on a surface perpendicular to the c-axis, and the surfaces are stacked in the c-axis direction.

Therefore, when the compressive stress is applied in the nucleation and grain growth phase of the Nd ₂ Fe ₁₄ B phase, it is energy stable that the c-axis is aligned in this direction. Therefore, a driving force is generated to align the c-axis in the compressive stress direction, and the nucleation and growth of grains close to the compressive direction of the c-axis of the crystal dominate. Therefore, an Nd-Fe-B based alloy having a biaxial axis for magnetization, that is, anisotropy in the direction in which the compressive stress is applied can be obtained. On the contrary, when tensile stress is applied, compressive stress occurs in proportion to the Poisson ratio in the vertical direction to which tensile stress is applied, and it becomes energy stable that the c-axis is aligned in this direction. In addition to the Nd-Fe-B-based rare earth magnets, rare earth magnets such as Sm-Co have a large anisotropy in their crystal structure, and thus anisotropic rare earth alloy powder can be produced by applying the same principle.

Hot deformation during HDD release and recombination of the initial crystal structure and composition has the following effects.

First, the present invention releases hydrogen during the HDDR process and hot deformation such as hot-pressing and die-upsetting in the process of returning to the initial crystal structure. By directly applying high magnetic force and high energy anisotropic magnets by deformation, the manufacturing process is extremely simple and the manufacturing cost is very low.

Second, in the HDDR, which is a conventional rare earth alloy production method using hydrogen, in the case of Nd-Fe-B alloy, the anisotropy of powder is obtained by adding alloying elements that promote anisotropy such as Zr, Ga, Co, Ga lost. However, in the present invention, since the crystal structure of the rare earth-based alloy is used, there is no limitation in the composition of the applied alloy, and even in the Nd-Fe-B ternary alloy where a powder having a large anisotropy cannot be obtained by a conventional HDDR processor, the anisotropic alloy is used. Powder can be prepared, and thirdly, alloy powder with high anisotropy can be produced without adding expensive alloying elements, so that the process is simple and the manufacturing cost is low, and fourthly, the present invention is based on Nd-Fe-B system. Main phase crystal structures such as Sm-Co magnets as well as rare earth magnets can be applied to all rare earth magnets and magnets having anisotropy.

Claims (4)

Hot-pressing and die-upsetting of alloys in the process of releasing hydrogen and recombination into the initial crystal structure when manufacturing rare earth permanent magnets using hydrogen Rare-earth permanent magnet by hot-deformation during desorption and recombination after hydrogenation to directly manufacture magnets with strong anisotropy by applying hot-deformation such as Manufacturing method. The composition of claim 1, wherein the rare earth permanent magnet is composed of one or more rare earth elements, one or more transition metals, or the composition contains one or more of boron, carbon, and nitrogen. Method for producing a rare earth permanent magnet by hydrogenation and hot deformation. The method for producing a rare earth permanent magnet by hydrogenation and hot deformation according to claim 1, wherein the temperature range of the providing tablet such as hydrogenation reaction, dehydrogenation reaction and hot deformation is 700 to 1000 ° C. Hydrogenation to produce anisotropic alloy powders by applying hot deformation such as hot pressing and die-up setting to the alloy during the process of releasing hydrogen and recombination to return to the initial crystal structure when manufacturing rare earth permanent magnet using hydrogen After, dehydration and recombination method for producing rare earth alloy powder by hot deformation.