CN1424165A

CN1424165A - Method for producing Sm-Fe-N permanent magnet alloy powder by reduction diffusion

Info

Publication number: CN1424165A
Application number: CN 02159665
Authority: CN
Inventors: 孙光飞; 陈菊芳
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2002-12-30
Filing date: 2002-12-30
Publication date: 2003-06-18
Anticipated expiration: 2022-12-30
Also published as: CN1254338C

Abstract

A process for preparing permanent-magnet Sm-Fe-N alloy powder by reduction-diffusion method includes such steps as choosing and pretreating raw materials, proportioning, mixing, thermal reducing and diffusion alloying at 760-860 deg.C by use of Ca and CaH2 as reducer to obtain Sm-Fe alloy and by-products, chemical separating, dewatering Sm-Fe alloy powder, nitrizing, and preparing anisotropic Sm-Fe-N magnet. Its advantages are low reaction temp, less loss of Sm and high performance.

Description

Method for manufacturing Sm-Fe-N permanent magnet alloy powder by reduction diffusion method

The technical field is as follows:

the invention belongs to the field of magnetic materials, and particularly provides a method for manufacturing Sm-Fe-N permanent magnet alloy powder.

Background art:

the Sm-Fe-N alloy is a rare earth permanent magnet material with excellent performance, and in the aspect of basic magnetic characteristics, the saturation magnetization intensity is equivalent to that of R-Fe-B system, and the anisotropy field and Curie temperature are higher than those of R-Fe-B system. Since Sm-Fe-N decomposes above 600 deg.C, it is used primarily in the manufacture of bonded magnets whose magnetic properties are determined primarily by the magnetic properties of the Sm-Fe-N powder. At present, mechanical ingot crushing, also known as a conventional method, is used for preparing Sm-Fe-N magnetic powder (IEEE. trans. Mag.1993 (29): 2815); HDDR method (Physical Statuas Solidi A1995 (147): 229); rapid quenching (J.appl.Phys.1991.70 (6): 3188) and reductive diffusion (IEEE.Transs.Mag.35 (5) 1999: 3322).

Mechanical ingot crushing: high-purity Sm and Fe are smelted into Sm-Fe alloy ingot in vacuum, mechanically crushed and ground into fine powder, and nitrided to obtain Sm-Fe-N magnetic powder. HDDR (hydrogenation-disproportionation-dehydrogenation-recombination) process: after obtaining the Sm-Fe alloy ingot casting, crushing the Sm-Fe alloy ingot casting into coarse particles with the particle size of about 50 mu m, placing the Sm-Fe alloy ingot casting into a hydrogen treatment furnace, preparing Sm-Fe alloy fine powder through processes of different temperatures, hydrogen pressures and negative pressures, and then preparing Sm-Fe-N magnetic powder through nitriding treatment. A rapid quenching method: and remelting the Sm-Fe alloy ingot, spraying the melt onto a water-cooled copper roller rotating at a high speed by high-pressure inert gas flow to quickly solidify into belt scraps, crushing the belt scraps into alloy powder, and nitriding the alloy powder to prepare the Sm-Fe-N magnetic powder. The developed reduction diffusion method takes samarium oxide as a raw material, metal samarium is extracted by metal calcium thermal reduction, then Sm-Fe alloy is formed by diffusion between rare earth samarium and alloy element iron, and Sm-Fe-N magnetic powder is prepared by nitriding alloy powder.

The conventional method, the HDDR method and the rapid quenching method have the following common points: the rare earth metal samarium purified by a complex distillation process is adopted, then the Sm-Fe alloy ingot is smelted, and mechanically crushed to prepare Sm-Fe alloy powder. The developed reduction diffusion method for preparing Sm-Fe-N alloy adopts samarium oxide as a raw material, omits a special rare earth distillation and purification process, and has the advantages. Sm however₂O₃The melting point of Sm is higher, namely 2325 ℃, while the vapor pressure of Sm is higher, and the volatilization is more serious at higher temperature. In general, higher temperatures are often used to accelerate the reductive diffusion process, and are just detrimental to the diffusion alloying between Sm and Fe.

The invention content is as follows:

the invention aims to provide a method for preparing SmCl with low melting point (678℃)₃As a raw material, byThe Sm-Fe-N alloy powder with controllable granularity is prepared by the metallothermic reduction and diffusion alloying method, and is beneficial to diffusion alloying between Sm and Fe.

The technological process for preparing the Sm-Fe-N alloy powder comprises the following steps: raw material selection and pretreatment → proportioning of reactants → mixing of reactants → thermal reduction and diffusion alloying of metal → chemical separation of reaction products → dehydration drying of metal powder → nitriding treatment of powder → manufacture of anisotropic bonded Sm-Fe-N magnets. The process is described below.

1. Selecting raw materials: using SmCl₃The alloy elements are pure iron powder, and the granularity of the pure iron powder is controlled to be 300-800 meshes; iron oxides may also be selected as the starting material.

When preparing a multi-element Sm-Fe (M) -N alloy system, M is a transition metal and comprises Co, Cr, V and Zr.

The reducing agent is selected from Ca and CaH₂. The granularity of the material is controlled to be 3-5 mm.

2. Pretreatment of raw materials: SmCl₃And carrying out negative pressure dehydration treatment at 250-400 ℃.

3. The preparation of raw materials: the calculation of raw materials and the adjustment of the actual blending amount are carried out according to the basic reaction formula (1) by combining different reduction-diffusion reaction conditions.

(1)

SmCl₃The addition amount of the reducing agent exceeds 3-5% of the chemical amount, and the chemical amount of the reducing agent is 5-20% of the chemical amount required by the basic chemical reaction equation.

The transition metal in the multi-element alloy element may be added alone or in combination. The amount of Co substituted for Fe is in the range of 0-5%, and the amount of other transition group elements substituted for Fe is in the range of 0-3%, and exceeding this range affects the magnetic properties of the alloy.

4. Reduction and diffusion reaction: mixing the reactants after proportioning, carrying out thermal reduction reaction and diffusion alloying, wherein the reaction temperature is controlled to be 760-860 ℃, and Sm-Fe alloy powder and a byproduct CaCl are obtained after the reaction is finished₂And (5) carrying out water washing chemical separation. And dehydrating and drying to obtain the required Sm-Fe alloy powder.

5. Nitriding treatment of Sm-Fe alloy powder: application of Sm-Fe alloy powder in high-purity nitrogen or NH₄Or NH₄And H₂The pressure is 0.1-1.0 Mpa at 400-500 deg.C.

The invention has the advantages that: what is needed isThe method for preparing the Sm-Fe-N alloy powder adopts SmCl₃The method is used as a raw material, and extracts the metal samarium through metallothermic reduction, thereby saving the complex extraction process of high-purity rare earth metal, having lower temperature range of reduction diffusion reaction, reducing the volatilization loss of the metal samarium and being beneficial to diffusion alloying. By-product of reduction reaction CaCl₂Is soluble in water and therefore allows easy isolation of the reaction product. By selectively controlling the particle size of the iron powder of the reactant alloy element and because the solid diffusion reaction temperature is lower, the raw material can be effectively controlledComposition Sm₂Fe₁₇The granularity of the alloy powder is beneficial to improving the powder magnetism after nitriding, and the Sm-Fe-N magnet with high performance and anisotropy is obtained.

Example 1

The raw material adopts SmCl₃Fe powder (500 mesh), the chemical dose of each reactant, SmCl, was calculated according to equation (1)₃The addition amount is 103% of chemical dose, the particle size of metal Ca is 3mm, the addition amount is 15% of super chemical dose, and SmCl₃Vacuum dehydration treatment at 360 ℃. And (3) carrying out reduction diffusion reaction under the protection of argon, keeping the temperature at 820 ℃ for 2 hours, naturally powdering the reaction block in water, filtering out powder, and drying in vacuum. NH of alloy powder under the pressure of 0.1Mpa₄The Sm-Fe-N alloy powder is processed for 1 hour at 450 ℃ in the atmosphere, and the magnetic property of the prepared Sm-Fe-N alloy powder is as follows: br is 9.8kGs, and,_MHc＝8kOe，(BH)m＝18MGOe。

example 2

The raw material adopts SmCl₃Fe powder (500 mesh) and Co powder (500 mesh), the chemical dose of each reactant, SmCl, was calculated according to the formula (1)₃The amount of the added metal Ca is 105 percent of the chemical dose, the amount of the Co substituted Fe powder is 5 percent, the particle size of the metal Ca is 3mm, and the amount of the added metal Ca is 120 percent of the chemical dose. SmCl₃Vacuum dehydration treatment at 360 ℃. And (3) carrying out reduction diffusion reaction under the protection of argon, keeping the temperature of 850 ℃ for 2 hours, naturally powdering the reaction block in water, filtering out powder, and drying in vacuum. NH of alloy powder under the pressure of 0.2Mpa₄And H₂(7.5: 2.5) for 1 hour at 450 ℃, and the magnetic property of the prepared Sm-Fe-N alloy powder is as follows: br ═ 11.2kGs，_MHc＝9.8kOe，(BH)m＝26MGOe。

Claims

1. A method for manufacturing Sm-Fe-N permanent magnet alloy powder by a reduction diffusion method comprises the following process flows: raw material selection and pretreatment → mixture of reactants → metal thermal reduction and diffusion alloying → chemical separation of reaction products → dehydration and drying of metal powder → powder nitriding treatment → manufacture of anisotropic bonded Sm-Fe-N magnet; the method is characterized in that:

a. selecting raw materials: using SmCl₃The alloy is prepared from pure iron powder with the granularity of 300-800 meshes; the reducing agent is selected from Ca and CaH₂The granularity is controlled to be 3-5 mm;

b. pretreatment of raw materials: SmCl₃Performing negative pressure dehydration treatment at 250-400 ℃;

c. the preparation of raw materials: calculating raw materials and adjusting the actual addition amount according to the basic reaction formula (1) by combining different reduction diffusion reaction conditions;

(1)

SmCl₃the addition amount of the reducing agent exceeds 3-5% of the chemical amount, and the addition amount of the reducing agent exceeds 5-30% of the chemical amount required by a basic chemical reaction equation;

d. reduction and diffusion reaction: mixing the reactants after proportioning, carrying out thermal reduction reaction and diffusion alloying, controlling the reaction temperature to 760-860 ℃, and after the reaction is finished, obtaining Sm-Fe alloy powder and a byproduct CaCl₂Carrying out water washing chemical separation, and then carrying out vacuum drying to obtain the required Sm-Fe alloy powder;

nitriding treatment of Sm-Fe alloy powder: application of Sm-Fe alloy powder in high-purity nitrogen or NH₄Or NH₄And H₂The pressure is 0.1-1.0 Mpa, the temperature is 400-500 ℃, and the anisotropic Sm-Fe-N permanent magnet alloy powder with required components and granularity requirements is directly obtained.

2. According to claimThe method for manufacturing Sm-Fe-N permanent magnet alloy powder by a reduction diffusion process, as recited in claim 1, is characterized by: the base alloy element raw material can also be iron oxide with the granularity of 300-800 meshes; fe in the Sm-Fe-N alloy can be partially replaced by M, M is transition group metal, including Co, Cr, V and Zr, which can be added independently or jointly, the Fe replacing amount of Co ranges from 0% to 5%, and the Fe replacing amount of other transition group elements ranges from 0% to 3%; nitriding treatment of Sm-Fe alloy powder: the Sm-Fe alloy powder may also be in NH₄Or NH₄And H₂The pressure is 0.0-1.0 Mpa at 400-500 deg.C.