Disclosure of Invention
Aiming at the prior art, heavy rare earth elements are added for improving the coercive force of a neodymium iron boron magnet; or the process for preparing the NdFeB-SmFeN composite magnet is complex, the requirements for equipment are strict, and the cost is high. The sintered neodymium iron boron containing SmFeN or SmFeC has high coercive force, high temperature resistance and high resistance, the coercive force is increased greatly before and after grain boundary diffusion treatment, and the preparation method has simple operation and low cost.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of sintered neodymium iron boron containing SmFeN or SmFeC, which comprises the following steps:
s1, forming Sm on the surface of the neodymium iron boron sintered body2Fe17-xMxPerforming grain boundary diffusion treatment on the coating which is a diffusion source;
s2, performing nitriding treatment or carbonizing treatment; wherein Sm is contained in the resulting alloy powder after nitriding treatment2Fe17-xMxNySintering neodymium iron boron; when carbonized, Sm-containing compounds are obtained2Fe17-xMxCySintering neodymium iron boron;
wherein M is one or more of Co, Mo, Cu, Zr, Ti and Al, and x is 0-2; y is 1 to 5.
In the present invention, the neodymium iron boron sintered body may be conventional in the art.
Preferably, the raw materials of the neodymium iron boron sintered body comprise: r: 28-32%; fe: 65.5-70%; b: 0.90-1.2%; m: 0 to 5 percent; wherein the percentage is the mass percentage of the element in the total amount of the element; the R comprises Nd, Pr, La, Ce, Sm and RH, and the RH is a heavy rare earth element; and M is one or more of Cu, Co, Al, Ti, Nb, Zn, Hf, Zr and Ga.
In a preferred embodiment of the present invention, the raw materials of the neodymium iron boron sintered body include: PrNd: 29.7%, Ho: 1.5 percent; fe: 65.6 percent; b: 0.95 percent; cu: 0.2 percent; co: 1.2 percent; al: 0.6 percent; zr: 0.15 percent; ga: 0.1 percent, wherein the percentage of the element accounts for the mass percentage of the total mass.
Preferably, the neodymium iron boron sintered body is prepared by smelting, casting, hydrogen crushing, powder forming, magnetic field compression molding and sintering raw materials of the neodymium iron boron sintered body.
The smelting and casting equipment can be conventional in the field, and is generally a medium-frequency vacuum smelting furnace, such as a medium-frequency vacuum induction rapid hardening melt-spinning furnace.
The smelting temperature can be conventional in the art, and is preferably 1300-1700 ℃, and more preferably 1450-1550 ℃, for example 1450, 1500 or 1550 ℃.
The casting temperature may be conventional in the art, and is more preferably 1200-1600 ℃, and is preferably 1350-1500 ℃, for example 1350, 1400 or 1500 ℃.
The operation and conditions of the hydrogen-broken powder can be conventional in the field, and generally comprise a hydrogen breaking process and a jet milling process which are sequentially carried out.
Wherein the shaping may be conventional in the art. More preferably, the magnetic field is oriented vertically or parallel pressed, and the magnetic field strength during orientation pressing is 1.5T or more, for example, 1.8T.
The operation and conditions of the sintering may be conventional in the art, among others. More preferably, the sintering is performed under a vacuum of less than 0.05 Pa.
Wherein the sintering temperature is preferably 1000-1200 deg.C, such as 1000, 1050, 1080 or 1090 deg.C.
The sintering time is preferably 0.5-10 hours, such as 0.5, 5 or 10 hours.
Preferably, the thickness of the neodymium iron boron sintered body in the orientation direction is 0.1 to 10mm, more preferably 1 to 3mm, such as 1, 2 or 3 mm.
In a preferred embodiment of the present invention, it is known to those skilled in the art that in order to obtain a sheet-shaped sintered nd-fe-b body with an orientation thickness of 0.1 to 10mm, the sheet-shaped sintered nd-fe-b body (the orientation thickness is generally 5 to 70mm, more preferably 10 to 50mm, for example, 15, 30 or 45mm) needs to be sliced. After the sheet neodymium iron boron sintered body is obtained, in order to remove an oxide layer and a surface degradation layer on the surface of the sintered body and create conditions for the adhesion of a diffusion layer during subsequent grain boundary diffusion, the sheet neodymium iron boron sintered body is pretreated, and the pretreatment can be conventional in the field. Preferably, the neodymium iron boron sintered body is ground, sand-blasted and acid-washed for standby.
In a preferred embodiment of the invention, the inert gas and H are2Under the condition, the activity of the surface layer of the neodymium iron boron sintered body can be further excited by adopting a low-temperature hydrogen activation method. The activated Nd-Fe-B sintered body can absorb H2H is permeated by high temperature and inert gas pressure during subsequent grain boundary diffusion treatment2Sm is a rapidly escaping substance when heated2Fe17-xMxThe diffusion source provides more diffusion channels, the grain boundary diffusion speed and the grain boundary diffusion depth are increased, the coercivity of the neodymium iron boron magnet is further improved, and the neodymium iron boron magnet with more uniform overall coercivity is obtained through preparation.
Preferably, the neodymium iron boron sintered body is firstly put in inert gas and H2Sm is formed on the surface of the activated neodymium iron boron sintered body after being activated under the condition2Fe17-xMxIs a coating of a diffusion source.
More preferably, the inert gas is one or more of helium, neon, argon, krypton, xenon, and radon, such as argon.
Wherein, more preferably, the inert gas and H2The pressure of (A) is 0.01 to 1MPa, for example 0.05MPa, and said H2The mass percentage of the neodymium iron boron sintered body is 0.03-0.1%, for example 0.05%.
Wherein the activation temperature is more preferably 200-300 ℃, preferably 200-260 ℃, for example 200, 240 or 260 ℃.
Wherein the activation time is more preferably 0.1-2 h, preferably 0.2-0.8 h, such as 0.2, 0.4 or 0.8 h.
In the invention, the method of grain boundary diffusion is adopted, and Sm is adopted2Fe17-xMx(M is one or more of Co, Mo, Cu, Zr, Ti and Al, and x is 0-2) as a diffusion source. In the process of grain boundary diffusion, Sm2Fe17-xMxThe coating is dispersed along NdFeB crystal boundary, distributed along the crystal boundary in neodymium-rich phase, and dispersed Sm2Fe17-xMxSm is formed by subsequent nitriding or carbonizing treatment2Fe17-xMxNyOr Sm2Fe17-xMxCyAnd (5) structure. The prepared composite magnet has the advantages of high coercive force, good high-temperature performance, high resistance, high remanence and excellent comprehensive performance.
In the present invention, Sm is mentioned above2Fe17-xMxThe preparation process of (b) may be conventional in the art.
Preferably, Sm is the same as above2Fe17-xMxThe preparation method of (3) may comprise the steps of: will be Sm according to the nominal composition2Fe17- xMxThe raw materials are subjected to vacuum melting, casting, annealing, jaw crushing and jet milling to prepare the material.
Wherein, preferably, the smelting is carried out by adopting a melt rapid quenching method, and the prepared product has Th2Zn17Sm of structure2Fe17-xMxA master alloy.
The smelting and casting equipment can be conventional in the field, and is generally a medium-frequency vacuum smelting furnace, such as a medium-frequency vacuum induction rapid hardening melt-spinning furnace. The frequency of the medium frequency vacuum melting furnace can be conventional in the art, and is more preferably 1500-2500 Hz, such as 1500, 2000 or 2500 Hz.
The thickness of the alloy sheet obtained by melting is more preferably 0.1 to 0.6mm, preferably 0.2 to 0.4mm, for example 0.2, 0.3 or 0.4 mm.
The smelting temperature can be conventional in the art, and is preferably 1300-2000 ℃, more preferably 1500-1750 ℃, for example 1500, 1600 or 1750 ℃.
Wherein the casting temperature can be conventional in the art, more preferably 1200-1900 ℃, preferably 1450-1600 ℃, for example 1450, 1500 or 1600 ℃.
Preferably, the annealing is to place the alloy sheet obtained by smelting in a vacuum furnace at 400-600 ℃, for example, 400, 500 or 600 ℃; the heating time of the annealing is more preferably 1 to 10 hours, preferably 3 to 5 hours, for example 3, 4 or 5 hours, so that the components of the alloy sheet are more uniform and the stress of the alloy sheet is eliminated.
Wherein the jaw crushing is generally carried out in a jaw crusher. More preferably, the jaw is broken to yield Sm 0.2 to 2mm D50, e.g. 0.2, 1 or 2mm D502Fe17-xMxAnd (3) powder.
Wherein, the jet mill can be conventional in the field, and is preferably carried out under the condition of 0.1-2 MPa, preferably 0.5-0.7 MPa.
The gas flow in the jet mill is preferably an inert gas, including one or more of helium, neon, argon, krypton, xenon, and radon, such as argon.
More preferably, Sm 2 with a D50 of 2.0 to 5.0 μm, e.g., a D50 of 2.0, 3.0 or 5.0 μm is obtained after the jet milling2Fe17-xMxAnd (3) fine powder.
Wherein more preferably Sm is obtained after said jet milling2Fe17-xMxThe fine powder and Sm are respectively2Fe17-xMx0.5 to 1.5 weight percent of antioxidant and 0.8 to 1.2 weight percent of lubricant which are based on the mass of the fine powder are uniformly mixed, wherein the antioxidant and the lubricant are conventional in the field, and are preferably special antioxidant and lubricant for magnetic materials produced by new Tianjin Yuesheng material research institute.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.631 percent; fe: 89.369 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 89.264 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 11.052 percent; fe: 88.948 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 88.264 percent; mo: 1 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 87.564 percent; co: 0.1 percent; mo: 1 percent; cu: 0.1 percent; zr: 0.2 percent; ti: 0.1 percent; al: 0.2 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 88.564 percent; co: 0.1 percent; cu: 0.1 percent; zr: 0.2 percent; ti: 0.1 percent; al: 0.2 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In the present invention, the grain boundary diffusion treatment may be conventional in the art.
Wherein preferably Sm is formed on the surface of the activated neodymium iron boron sintered body by adopting a thermal spraying method, a coating method or a vapor deposition method2Fe17-xMxIs a coating of a diffusion source.
The thickness of the coating is preferably 0.1 to 5mm, more preferably 0.5 to 2mm, such as 0.5, 1 or 2 mm.
The temperature of the grain boundary diffusion treatment is preferably 800 to 1000 ℃, for example 800, 900 or 1000 ℃.
The time of the grain boundary diffusion treatment is preferably 4 to 20 hours, more preferably 6 to 15 hours, such as 6, 8 or 15 hours.
Preferably, before the grain boundary diffusion treatment, the furnace is vacuumized until the degree of vacuum in the furnace is lower than 0.05Pa, and then an inert gas, such as argon, is introduced, wherein the pressure of the grain boundary diffusion treatment is 0.01 to 0.1MPa, such as 0.01, 0.04, or 0.1 MPa.
In the invention, the Nd-Fe-B sintered body after the grain boundary diffusion treatment is subjected to nitriding treatment or carbonizing treatment to form Sm with high coercivity, good high-temperature performance, high resistance and high remanence2Fe17-xMxNyOr Sm2Fe17-xMxCyRealization of NdFeB magnet and Sm2Fe17-xMxNyOr Sm2Fe17-xMxCyThe composition of the magnet can also solve Sm2Fe17-xMxNyOr Sm2Fe17-xMxCyMagnet at high temperature>Easy decomposition at 600 ℃, can improve the comprehensive magnetic property of the base material NdFeB, does not need to add heavy rare earth Dy or Tb, and has simple preparation process and low cost.
Wherein the nitriding treatment is preferably performed in a rotary nitriding furnace.
Wherein the carbonization treatment is preferably performed in a rotary carbonization furnace.
The temperature of the nitriding treatment or the carbonizing treatment is preferably 400 to 600 ℃, more preferably 480 to 580 ℃, for example 550 ℃.
The time of the nitriding treatment or the carbonizing treatment is preferably 1 to 10 hours, more preferably 3 to 6 hours, such as 3, 5 or 6 hours.
The invention also provides sintered neodymium iron boron containing SmFeN or SmFeC, which is prepared by the preparation method.
The invention also relates toProvides a kind of Sm2Fe17-xMxA powder comprising, as raw materials: sm: 10-11.5%; fe: 87-90%, M: 0-2%; the percentage is the atomic percentage of the element in the total amount of the element; m is one or more of Co, Mo, Cu, Zr, Ti and Al, and x is 0-2.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.631 percent; fe: 89.369 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 89.264 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 11.052 percent; fe: 88.948 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 88.264 percent; mo: 1 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 87.564 percent; co: 0.1 percent; mo: 1 percent; cu: 0.1 percent; zr: 0.2 percent; ti: 0.1 percent; al: 0.2 percent; the percentage is the atomic percentage of the element in the total amount of the element.
In a preferred embodiment of the present invention, Sm is mentioned2Fe17-xMxComprises the following raw materials: sm: 10.736 percent; fe: 88.564 percent; co: 0.1 percent; cu: 0.1 percent; zr: 0.2 percent; ti: 0.1 percent; al: 0.2 percent; the percentage is the atomic percentage of the element in the total amount of the element.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows: the NdFeB-SmFeN or NdFeB-SmFeC composite magnet structure with high temperature resistance, high resistance and high coercivity is prepared by nitriding or carbonizing the NdFeB-SmFe composite magnet and improving the matrix performance. The coercive force of the sintered neodymium iron boron is improved, and the problem that SmFeN or alloy SmFeC is easy to decompose at the temperature of over 600 ℃ can be avoided. The resistance and the high temperature resistance of the neodymium iron boron product are improved, and the application range of the neodymium iron boron magnet is widened.
Example 8
Except for optional Sm2Fe17-xMxThe raw materials have different formula component contents (shown in table 1), and the parameters in the steps 1-3 and 5-6 are the same as the preparation process of the example 1 except that the step 4 is not performed.
Comparative examples 9 to 10
Except for optional Sm2Fe17-xMxThe raw materials have different formula component contents (such asTable 1), the parameters in the remaining preparation process were the same as those of example 1.
Comparative example 11
Except for optional Sm2Fe17-xMxThe raw materials have different formula component contents (as shown in table 1), and the parameters in the steps 1-2 are the same as the preparation process of the example 1.
And step 3: mixing Sm2Fe17-xMxPutting the fine powder into a rotary nitriding furnace, and performing nitriding treatment at 550 ℃ for 5 hours to obtain Sm2Fe17-xMxNyAnd (5) fine powder for later use.
And 4, step 4: adding raw materials of a neodymium iron boron sintered body (the raw materials comprise 29.7 percent of PrNd, 1.5 percent of Ho, 65.6 percent of Fe, 0.95 percent of B, 0.2 percent of Cu, 1.2 percent of Co, 0.6 percent of Al, 0.15 percent of Zr and 0.1 percent of Ga according to the mass percent of the elements) into a medium-frequency vacuum induction rapid hardening melt-spun furnace for smelting and casting, wherein the smelting temperature is 1500 ℃, and the casting temperature is 1400 ℃; then hydrogen crushing powder (hydrogen crushing process and airflow milling process which are sequentially carried out) is carried out; then, the magnetic field is oriented and vertically pressed for forming, and the magnetic field intensity is 1.8T during orientation pressing; sintering under the condition that the vacuum degree is lower than 0.05Pa, wherein the sintering temperature is 1080 ℃ and the sintering time is 5 h; cutting the obtained neodymium iron boron sintered body into sheet neodymium iron boron sintered body with the orientation thickness of 2mm, and carrying out pretreatment, namely, grinding, sand blasting, acid washing and other procedures for standby application;
and 5: putting the pretreated sheet neodymium iron boron sintered body in a diffusion furnace, introducing Ar gas, heating to 240 ℃, and introducing hydrogen, Ar and H, which are 0.05 percent of the weight of the charged neodymium iron boron sheet material2The pressure of the sheet neodymium iron boron sintered body is 0.05MPa), and the sheet neodymium iron boron sintered body is activated at low temperature for 0.4 h;
step 6: after the low-temperature hydrogen activation is finished, vacuumizing the diffusion furnace until the vacuum degree is below 0.05Pa, refilling a certain amount of Ar gas, wherein the pressure in the furnace is 0.04MPa, and heating to 900 ℃ under the Ar gas. Then Sm is prepared by the step 32Fe17-xMxNyThe fine powder is evenly sprayed to the flaky neodymium iron boron for sintering under the condition of the thermal spraying processThe surface of the body is coated with 1mm of coating thickness, and the grain boundary diffusion treatment is carried out for 8h at the temperature.
TABLE 1 Sm2Fe17-xMxThe formula component content of the raw material
Comparative example 12
The sample in this comparative example is the sheet-like sintered nd-fe-b body prepared in step 3 of example 1.
Comparative example 13
The sample in this comparative example was a 42UH brand performance blank purchased from fujian province, changtian, jinlong rare earth ltd, containing more than 5 wt% Dy.
Effects of the embodiment
Table 2 shows the magnetic properties and resistivity of examples 1 to 7 and comparative examples 8 to 10.
TABLE 2 comparison of magnetic and resistivity of examples and comparative examples
From the above table it can be seen that:
the sintered neodymium iron boron containing SmFeN or SmFeC has high coercive force, the coercive force increase amplitude before and after grain boundary diffusion treatment is large (compared with the comparative example 11 in the embodiments 1-7), and the preparation method is simple to operate and low in cost.
Comparative example 10 Sm for example 1 to 72Fe17-xMxThe raw materials are prepared according to the ratio of 2:17, Sm loss is generated in the processes of smelting, jet milling and the like, and the component ratio of the obtained product is lower than 2:17, so that the Hcj of the product is greatly influenced.
Compared with the examples 1-8, the performance equivalent to that of the invention can be achieved only by adding more than 5 wt% of heavy rare earth element Dy into the neodymium iron boron magnet, and the cost is higher.