CN1165055C - High-performance dual-phase rare earth permanent magnet material and preparation method thereof - Google Patents

Abstract

The present invention discloses a high-performance bi-phase permanent-magnet rare-earth material and a preparing method thereof. The high-performance bi-phase permanent-magnet rare-earth material comprises: 6.2 to 12.0 at% of rare-earth elements, 0.5 to 4.5 at% of nitrogen elements and 2.5 to 6.0 at% of metalloid elements using B as a main component, and the rest is transition group metal using Fe as the main component. The preparing method comprises: firstly, alloy is prepared in a vacuum melting method; then, alloy powder is prepared by using a rapid quenching method or a mechanical alloying method and combining a suitable heat treatment process; finally, alloy magnets are prepared by using a bonding, a cold pressing, a hot pressing or a warm deforming method. Magnetic powder and magnets produced by using the present invention have the advantages of better comprehensive permanent-magnet performance, higher working temperature or better resistance to corrosion and low rare-earth content. The magnet preparation method, equipment and processes of the present invention are simple.

Description

High-performance dual-phase rare earth permanent magnet material and preparation method thereof

Technical field

The invention relates to a high-performance dual-phase rare earth permanent magnet material and a preparation method thereof.

Background technique

Rare earth bonded magnet is a magnetic material made of magnetic rare earth alloy powder bonded with organic or soft metal binder. Rare earth bonded magnets have a high performance-price ratio, can be directly formed or processed into components with complex shapes, have high toughness, are not easy to break, crack, and have small deviations in magnetic properties, which meet the high performance requirements of magnetic materials in recent years. Therefore, its total sales have grown rapidly, with an average annual growth rate of 35%. The magnetic properties of rare earth bonded magnets are affected by the properties of the magnetic powder and the bonding density, among which the magnetic properties of the powder are considered to be the first factor. However, the comprehensive magnetic properties of the most commonly used isotropic Nd-Fe-B rare earth permanent magnet powder are not satisfactory, and the typical technical properties are: B _r =0.55-0.80T, _i H _c =350-600kA /m, (BH) _max = -64-96 kJ/m ³ .

For this reason, people have developed a nano-two-phase rare earth permanent magnet material, which is composed of a nanocrystalline hard magnetic phase and a soft magnetic phase. The hard magnetic phase has a high intrinsic coercive force, and the soft magnetic phase has a high saturation magnetization. , There is a magnetic exchange coupling effect at the interface of the two phases, so that the material has a high saturation magnetization of the soft magnetic phase and a high coercive force of the hard magnetic phase at the same time, thus having a high magnetic energy product. The theoretical magnetic energy product of nano-duplex permanent magnets can reach 1000kJ/m ³ , which is nearly twice as high as that of sintered NdFeB magnets. Moreover, the rare earth content of the nano-two-phase permanent magnet material is low, and the price is cheap, so it has potential development and application prospects.

At present, the typical nano two-phase permanent magnet materials are: Nd ₂ Fe ₁₄ B/α-Fe type and Nd ₂ Fe ₁₄ B/Fe ₃ B type. Although the addition of the soft magnetic phase α-Fe and Fe ₃ B increases the residual magnetization of the nano-two-phase permanent magnet, the coercive force also decreases with the addition of the soft magnetic phase, which is generally less than 450kA/m. Such a value affects the Its application at higher temperatures, especially when the magnets are thinner. Moreover, due to the limitations of current scientific research methods, the crystal structure of magnetic powder is difficult to achieve the microstructure required in the theoretical model: the two-phase crystals are continuous, the size is about 10nm, there is no non-magnetic phase between the two phases, and they are completely coupled. Therefore, the magnetic properties of the material are not very ideal. Generally, the maximum magnetic energy product can only reach 158kJ/m ^-3 , which is far from the theoretical value, and cannot meet the requirements of high-performance magnets. All these lead to the failure of this material to be widely used.

Contents of Invention

The purpose of the present invention is to provide a high-performance dual-phase rare earth permanent magnet material and a preparation method thereof.

The composition formula of the high-performance dual-phase rare earth permanent magnet material is R _x TM _100-xyz M _y N _z , where R is a rare earth element, TM is a transition metal, M is a metalloid and N is a nitrogen element, and x is 6.2 to 12.0 at%, y is 2.5-6.0 at%, and z is 0.5-4.5 at%. It has a two-phase structure composed of base phase R ₂ TM ₁₄ MN _ζ and second phase TM _δ N, wherein ζ is 0.1-0.8 at%, and δ is 2-8 at%.

The steps of a preparation method of a high-performance dual-phase rare earth permanent magnet material are as follows:

1) First prepare an ingot with the composition R _x TM _100-xy M _y , where x is 7.2 to 14.0 at%, and y is 3.5 to 7.5 at%, and the ingot is melted in an electric arc furnace, an induction furnace or a magnetic levitation melting furnace , Melting is carried out under vacuum or protective atmosphere.

2) Under the protection of high-purity nitrogen, the ingot is crushed to 50-110 microns, and iron powder with a purity of more than 99.5% and a particle size of less than 15 microns is mixed.

3) Under the high-purity nitrogen atmosphere, the mixed powder is high-energy ball milled for 35-50 hours.

4) Put the ball-milled product into a vacuum furnace, evacuate to 10 ^-5 ~ 10 ^-6 Pa, pass in argon gas with a purity of 99.9%, heat to 600 ~ 780 ° C, keep it warm for 10 ~ 30 minutes, and it will be released quickly cold.

5) The obtained powder is shaped by bonding, cold pressing, hot pressing or warm deformation.

The steps of the preparation method of another high-performance dual-phase rare earth permanent magnet material are as follows:

1) First prepare an ingot whose composition is R _x TM _100-xy M _y , where x is 6.5-13.0 at%, y is 2.5-7.0 at%, and the ingot can be cast in an electric arc furnace, an induction furnace or a magnetic levitation melting furnace Melting, smelting is carried out under vacuum or protective atmosphere.

2) Put the cast ingot into a vacuum belt throwing machine, melt it in vacuum or under the protection of high-purity argon, and then quench it with a single roll.

3) Under the atmosphere of high-purity nitrogen, the quick-quenching alloy is broken into particles of 15-30 microns.

4) Put the quick-quenching powder into the vacuum furnace, evacuate to 10 ^-5 ~ 10 ^-6 Pa, pass in the mixed gas of NH ₃ and H ₂ at 1×10 ⁵ ~ 1.5×10 ⁵ Pa, and heat to 400~ 500°C, keep warm for 20-50 minutes, take out the oven and cool quickly.

5) The obtained powder is shaped by bonding, cold pressing, hot pressing or warm deformation.

The advantages of the present invention are:

1) The magnetic powder and bonded magnet obtained in the present invention, due to the exchange coupling effect of nanocrystalline R ₂ TM ₁₄ MN _ζ phase and TM _δ N phase, the material can simultaneously have high saturation magnetization of TM _δ N phase and R ₂ TM ₁₄ The high coercive force of the MN _ζ phase results in a better comprehensive permanent magnetism than traditional dual-phase rare earth permanent magnet materials.

2) The magnetic powder and bonded magnet obtained in the present invention have a higher working temperature or better corrosion resistance than traditional two-phase rare earth permanent magnets.

3) The magnetic powder and the bonded magnet obtained in the present invention require less rare earth element content, so the cost is low.

4) The magnet preparation method of the present invention: the equipment and process are simple, easy to operate, and the process consumption is low.

Detailed ways

Describe in detail below in conjunction with embodiment.

1) Material composition: the present invention is a novel nano-two-phase rare earth permanent magnet material, and its composition formula is: R _x TM _100-xyz M _y N _z . In the formula, TM is a transition metal, mainly Fe, the content of Fe is not less than 75 at% of the total amount of TM, and the rest can be replaced by Co, and the content of Co is less than 25 at% of the total amount of TM. In addition, TM may contain a small amount of IVB or VB group transition metal elements, such as one or more elements such as Ti, Zr, Cr and Nb, whose content does not exceed 5 at% of the total amount of TM; where M is mainly B, B The content is not less than 90at% of the total amount of M; in the formula, R is one or more than one rare earth element, at least one of which is Nd, Pr or NdPr alloy, and its content is not less than 70at% of the total amount of R. In the formula, x=6.2-12.0at%, y=2.5-6.0at%,. z = 0.5-4.5 at%.

2) Phase composition: the novel permanent magnet disclosed in the present invention is a two-phase structure, the base phase is R ₂ TM ₁₄ MN _ζ phase, and the second phase is TM _δ N, where ζ=0.1-0.8at%, δ=2 -8at%. Compared with Nd ₂ Fe ₁₄ B phase, R ₂ TM ₁₄ MN _{ζ phase} has higher Curie temperature (750K) and larger room temperature magnetocrystalline anisotropy field (8.5T). The TM _δN phase alone has a higher saturation magnetization value than that of the α-Fe phase, and its highest saturation magnetization can reach 2.9T, while that of α-Fe is only 2.15T. When the R ₂ TM ₁₄ MN _ζ phase and the TM _δ N phase are exchange-coupled, the material has the high saturation magnetization of the TM _δ N phase and the high coercive force of the R ₂ TM ₁₄ MN _ζ phase at the same time, thus obtaining a higher than the traditional dual Phase rare earth permanent magnet materials have better comprehensive permanent magnetism. Since the exchange coupling of the two phases can only be exerted in the short range, the grain size of the two phases should not exceed 80nm.

According to the above description, R in the composition formula can be Pr, Sm, Nd, Dy and other rare earth elements, but only Nd ₂ Fe ₁₄ BN _ζ and Pr ₂ Fe ₁₄ BN _ζ phases have high saturation magnetization and high coercive force Combination, in order to further improve the temperature characteristics or coercive force value, some other rare earth elements can be used to replace Pr and Nd, but it should not be too much, otherwise it will affect the comprehensive magnetic properties, so at least one of R is required to choose Nd, Pr or PrNd alloy, and The content is not less than 70at% of the total amount of R.

N is an indispensable element in the formation of R ₂ TM ₁₄ MN _ζ phase and TM _δ N phase in the nano-two-phase rare earth permanent magnet material provided by the present invention, and its role is that nitrogen can occupy R ₂ TM ₁₄ in the form of interstitial solid-solution atoms The interstitial position of the M lattice changes its lattice constant, resulting in an increase in the intrinsic coercive force and Curie temperature, and N can react with Fe to form TM _δ N phase, which has a higher saturation magnetization value than α-Fe And corrosion resistance, so that the magnetic material reaches a level of practical significance.

In the present invention, a part of Fe in TM can be replaced by Co, which does not impair the magnetism of the permanent magnet material, and can also improve the temperature characteristics of the material, but if the replacement amount of Co exceeds 25 at% of the total amount of TM, the magnetism will be weakened.

In the permanent magnet material of the present invention, except that Fe can be substituted by Co, TM can contain one or more than one or more of Ti, Zr, Cr and Nb, etc. not greater than 5 at% of the total amount of TM, and M can also contain less than 5 at% of the total amount of TM. One or more than one Si, C, etc. of 10at% of the total amount of M, these elements are either intentionally added, or mixed in as impurities from raw materials, which do not affect the magnetic properties of the permanent magnet material of the present invention.

3) Preparation method:

One method is to use Fe, Nd, Dy, Co, Zr, Cr and industrial ferroboron with a purity greater than 99.6% as raw materials, and prepare them according to the ratio of R _x TM _100-xy M _y , where x is 7.2-14.0at%, y is 3.5-7.5at%, put into induction furnace, electric arc furnace or magnetic levitation melting furnace, vacuumize to 10 ^-5 Pa or above, and then pass through 0.8×10 ⁵ -1.2×10 ⁵ Pa High-purity argon, under the protection of argon, repeated smelting 3-4 times to ensure the ingot with uniform composition; under the protection of high-purity nitrogen, use a crusher or ball mill to break the ingot, and then sieve the particle diameter less than 110 The micron ingot powder is prepared for high-energy ball milling, and the particle diameter is preferably 50-90 microns; under a protective atmosphere, the sieved ingot powder and iron powder (purity greater than 99.5%, particle size less than 15 microns) are mixed evenly, The volume percentage of iron powder is 10%-40%; under the nitrogen atmosphere with a purity of 99.9%, the above-mentioned mixed powder is high-energy ball milled for 35-50 hours; then, the product after high-energy ball milling is put into a vacuum furnace , evacuate to 10 ^-5 -10 ^-6 Pa, pass in argon gas with a purity of 99.9%, heat to 600-780°C, keep it warm for 10-30 minutes, and quickly cool it out of the furnace; finally, the obtained powder is bonded, cold-pressed , hot pressing or warm deformation to shape.

Another method is to use Fe, Nd, Dy, Co, Zr, Cr and industrial ferroboron with a purity greater than 99.6% as raw materials, and prepare them according to the ratio of R _x TM _100-xy M _y , where x 6.5-13.0at%, y is 2.5-7.0at%, put it into induction furnace, electric arc furnace or magnetic levitation melting furnace, vacuumize to 10 ^-5 Pa or above, and then pass through 0.8×10 ⁵ -1.2×10 ⁵ Pa high-purity argon, repeated smelting 3-4 times under the protection of argon to ensure the ingot with uniform composition; then, put the ingot into the vacuum belt throwing machine, after melting in vacuum or under the protection of argon Single-roll rapid quenching, the surface speed of the molybdenum roller is 15m/s-35m/s; the obtained rapid-quenching alloy is crushed into 15-30 micron particles in a crusher or a ball mill under the protection of high-purity nitrogen; then, Put it into a vacuum furnace, evacuate to 10 ^-5 -10 ^-6 Pa, feed a mixed gas of NH ₃ and H ₂ at 1×10 ⁵ -1.5×10 ⁵ Pa, heat it to 400-500°C, and keep it warm for 20- After 60 minutes, it is quickly cooled out of the oven; finally, the obtained powder is shaped by bonding, cold pressing, hot pressing or warm deformation.

Example 1

Using Fe, Nd, Co, Cr, Al and 16wt% B-Fe alloy with a purity of 99.9% as raw materials, according to the ratio of Nd _12.3 Fe _67.8 Co _10.8 Al _0.8 Cr _2.3 B ₆ , put it into a magnetic levitation melting furnace, pump Vacuum to 10 ^-5 Pa, then pass high-purity argon gas of 1.2×10 ⁵ Pa, and smelt repeatedly 3 times under the protection of argon gas to ensure that the ingot with uniform composition is obtained. In order to ensure that the composition of the ingot basically meets the design composition , we must pay attention to the loss of rare earth elements in the smelting process. Under the protection of high-purity nitrogen, crush the ingot with a crusher, and then sieve the ingot powder with a particle diameter of less than 110 microns for high-energy ball milling. Under protective atmosphere, the sieved ingot powder and iron powder (99.9% in purity, particle size less than 15 microns) were evenly mixed, wherein the volume percentage of iron powder was 38%. Under a nitrogen atmosphere with a purity of 99.9%, the above-mentioned mixed powder was high-energy ball milled for 45 hours, and then the product after high-energy ball milling was put into a vacuum furnace, vacuumed to 10 ^-5 Pa, and argon with a purity of 99.9% was introduced. Air, heat to 670°C, keep warm for 30 minutes, take out of the oven and cool quickly. Then, the obtained magnetic powder was mixed with 2.5wt% epoxy resin, press-molded under a pressure of 20 MPa, and then the green compact was kept at 140°C for 1 hour to be cured to obtain a bonded magnet. Using a vibrating sample magnetometer, the results of measuring the magnetic properties of the magnetic powder are as follows: B _r = 1.26T, _i H _c = 845kA/m, (BH) _max = 242kJ/m ³ ; the results of measuring the magnetic properties of the bonded magnet are as follows: B _r =1.15T, _i H _c =680kA/m, (BH) _max =192kJ/m ₃ .

Example 2

Using Fe, Nd, Dy, 16wt% B-Fe alloy with a purity of 99.9% as raw materials, according to the ratio of Nd _8.5 Dy _1.2 Fe _84.3 B ₆ , put it into a magnetic levitation melting furnace, vacuumize to 10 ^-5 Pa, and then Introduce high-purity argon gas of 1.2×10 ⁵ Pa, and smelt repeatedly 3 times under the protection of argon gas to ensure that the ingot with uniform composition is obtained. loss in . Next, put the alloy ingot into a quartz tube with a small hole at the bottom and place it in the strip machine. The vacuum degree in the cavity of the strip machine is ^10-5 Pa, and the distance between the lower end of the quartz tube and the molybdenum roller surface is 0.5mm. , the diameter of the nozzle at the lower end of the quartz tube is 0.4mm, the injection pressure difference is 6.5×10 ³ Pa, and the heating voltage of the high-frequency heating coil is 3.2kV. After the ingot is melted under the protection of high-purity argon, it is sprayed to the On a molybdenum roll with a surface speed of 25m/s, a rapidly quenched alloy was obtained. Under the protection of high-purity nitrogen, the obtained quick-quenching alloy is crushed into 15-30 micron particles in a ball mill, then put into a vacuum furnace, evacuated to 10 ^-5 Pa, and 1.5×10 ⁵ Pa of NH ₃ and H ₂ mixed gas, the volume percentage of ammonia in the mixed gas is 30%, heated to 450°C, kept warm for 40 minutes, and quickly cooled after being out of the furnace. Then, the obtained magnetic powder was mixed with 2.5wt% epoxy resin, press-molded under a pressure of 20 MPa, and then the green compact was kept at 140° C. for 1 hour to be cured to obtain a bonded magnet. Using a vibrating sample magnetometer, the results of measuring the magnetic properties of the magnetic powder are as follows: B _r = 1.28T, _i H _c = 760kA/m, (BH) _max = 212kJ/m ³ ; the results of measuring the magnetic properties of the bonded magnet are as follows: B _r =1.15T, _i H _c =615kA/m, (BH) _max =175kJ/m ³ .

Claims (7)

1. a high-performance dual-phase permaneng-magnet rare-earth material is characterized in that empirical formula is R _xTM _100-x-y-zM _yN _z, wherein R is that rare earth element, TM are that magnesium-yttrium-transition metal, M are that metalloid and N are the nitrogen element, and x is 6.2～12.0at%, and y is 2.5～6.0at%, and z is 0.5～4.5at%.It has basic phase R ₂TM ₁₄MN _ζWith second TM mutually _δThe two phase structure that N constituted, wherein ζ is 0.1～0.8at%, δ is 2～8at%.

2. a kind of high-performance dual-phase permaneng-magnet rare-earth material according to claim 1 is characterized in that: said rare-earth element R is Nd or Pr or Nd, Pr alloy, and its content is no less than the 70at% of R total amount.

3. a kind of high-performance dual-phase permaneng-magnet rare-earth material according to claim 1, it is characterized in that: said magnesium-yttrium-transition metal TM mainly is Fe, the content of Fe is not less than the 75at% of TM total amount, contain the Co that accounts for TM total amount 0～25at%, and contain among metal Ti, Zr, Cr and the Nb that accounts for TM total amount 0～5at% one or more.

4. a kind of high-performance dual-phase permaneng-magnet rare-earth material according to claim 1 is characterized in that: said metalloid M mainly is B, and B content is not less than the 90at% of M total amount.

5. the preparation method of a high-performance dual-phase permaneng-magnet rare-earth material is characterized in that its step is:

1) at first prepared composition is R _xTM _100-x-yM _yIngot casting, x is 7.2～14.0at% in the formula, y is 3.5～7.5at%, ingot casting melting in arc furnace, induction furnace or magnetic levitation melting stove, melting is carried out under vacuum or protective atmosphere;

2) under high pure nitrogen protection, ingot casting is crushed to 50～110 microns, sneaks into purity more than 99.5%, particle size is less than 15 microns iron powder, and the volumn concentration of iron powder is 10%～40%;

3) under high pure nitrogen atmosphere, with mixed-powder high-energy ball milling 35～50 hours;

4) product behind the ball milling is packed in the vacuum furnace, be evacuated to 10 ^-5～10 ^-6Pa, feeding purity is 99.9% argon gas, is heated to 600～780 ℃, is incubated 10～30 minutes, it is cold soon to come out of the stove;

5) the gained powder by bonding, cold pressing or hot pressing comes moulding.

6. the preparation method of a high-performance dual-phase permaneng-magnet rare-earth material is characterized in that its step is:

1) at first prepared composition is R _xTM _100-x-yM _yIngot casting, x is 6.5～13.0at% in the formula, y is 2.5～7.0at%, ingot casting can melting in arc furnace, induction furnace or magnetic levitation melting stove, melting is carried out under vacuum or protective atmosphere;

2) ingot casting is put into vacuum and got rid of the band machine, in a vacuum or high-purity argon gas protection fusing back single roller rapid quenching down;

3) under high pure nitrogen atmosphere, fast quenched alloy is broken into 15～30 microns particle;

4) the fast quenching powder is packed in the vacuum furnace, be evacuated to 10 ^-5～10 ^-6Pa feeds 1 * 10 ⁵～1.5 * 10 ⁵The NH of Pa ₃And H ₂Mist, be heated to 400～500 ℃, be incubated 20～50 minutes, it is cold soon to come out of the stove;

5) the gained powder by bonding, cold pressing or hot pressing comes moulding.

7. the preparation method of a kind of high-performance dual-phase permaneng-magnet rare-earth material according to claim 6, it is characterized in that: during the ingot casting fast melt-quenching, the linear resonance surface velocity of molybdenum roller is 15m/s～35m/s.