CN117524699A - Method for improving surface magnetic consistency of sintered NdFeB magnetic steel - Google Patents
Method for improving surface magnetic consistency of sintered NdFeB magnetic steel Download PDFInfo
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- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 50
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 32
- 239000010959 steel Substances 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000000843 powder Substances 0.000 claims abstract description 46
- 238000012216 screening Methods 0.000 claims abstract description 17
- 238000003723 Smelting Methods 0.000 claims abstract description 11
- 238000000465 moulding Methods 0.000 claims description 15
- 229910045601 alloy Inorganic materials 0.000 claims description 14
- 239000000956 alloy Substances 0.000 claims description 14
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 12
- 239000001257 hydrogen Substances 0.000 claims description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims description 12
- 238000007873 sieving Methods 0.000 claims description 12
- 238000005245 sintering Methods 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000000314 lubricant Substances 0.000 claims description 8
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 6
- 238000009826 distribution Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- 239000003963 antioxidant agent Substances 0.000 claims description 4
- 230000003078 antioxidant effect Effects 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 229910001004 magnetic alloy Inorganic materials 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 239000006247 magnetic powder Substances 0.000 abstract description 7
- 238000005054 agglomeration Methods 0.000 abstract description 4
- 230000002776 aggregation Effects 0.000 abstract description 4
- 239000013078 crystal Substances 0.000 abstract description 4
- 239000000696 magnetic material Substances 0.000 abstract description 4
- 229910052779 Neodymium Inorganic materials 0.000 abstract description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 abstract description 3
- 238000009827 uniform distribution Methods 0.000 abstract description 3
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 2
- 150000002910 rare earth metals Chemical class 0.000 abstract description 2
- 238000002360 preparation method Methods 0.000 description 9
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 4
- 238000006356 dehydrogenation reaction Methods 0.000 description 4
- 238000005457 optimization Methods 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- STMDPCBYJCIZOD-UHFFFAOYSA-N 2-(2,4-dinitroanilino)-4-methylpentanoic acid Chemical compound CC(C)CC(C(O)=O)NC1=CC=C([N+]([O-])=O)C=C1[N+]([O-])=O STMDPCBYJCIZOD-UHFFFAOYSA-N 0.000 description 2
- ATVJXMYDOSMEPO-UHFFFAOYSA-N 3-prop-2-enoxyprop-1-ene Chemical compound C=CCOCC=C ATVJXMYDOSMEPO-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0266—Moulding; Pressing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0573—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes obtained by reduction or by hydrogen decrepitation or embrittlement
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0576—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together pressed, e.g. hot working
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Powder Metallurgy (AREA)
- Hard Magnetic Materials (AREA)
Abstract
The invention relates to a method for improving the surface magnetic consistency of sintered NdFeB magnetic steel, belonging to the field of rare earth permanent magnetic materials. Firstly, screening out the throwing pieces with good columnar crystal tissue structure in the smelting process, and facilitating the crushing of the follow-up throwing pieces and the acquisition of magnets with neodymium-rich phase uniform distribution structures; and the powder agglomeration is reduced through the screen mesh number of 20-60 in the screening treatment, the fluidity is enhanced, the subsequent forming and orientation are facilitated, and in addition, the magnetic powder passing through the die cavity is uniformly and fully oriented through the design of the die in the forming link.
Description
Technical Field
The invention relates to a method for improving the surface magnetic consistency of sintered NdFeB magnetic steel, belonging to the field of rare earth permanent magnetic materials.
Background
The sintered NdFeB permanent magnetic material is used as the permanent magnetic material with the highest comprehensive magnetic performance in the current permanent magnetic field, is widely applied to the fields of medical treatment, new energy, digital equipment, industrial motors and the like of various national and civil affairs, and has the reputation of 'magnetic king'. The surface magnet is used as a most visual technical index for measuring magnetic performance, is widely used in downstream clients, but has a phenomenon of 'negative and positive surface' (namely, the magnetic difference between N pole and S pole of a magnetizing surface is more than 5%) due to poor consistency of partial magnetic steel products in the practical application process, so that the use of equipment after installation is influenced, for example, the stability of operation of motor equipment is influenced, and the phenomenon of machine failure occurs in the operation process.
Chinese patent application document (publication No. 108806963A) discloses a screening method for consistency of sintered NdFeB magnetic steel performance, which improves consistency of finished magnetic steel magnetic performance by screening blank size and magnetic performance after tapping, but the method does not solve the problem of consistency of product surface magnetic performance from the source, and meanwhile, a step of inspection is added.
Disclosure of Invention
Aiming at the defects in the prior art, the application provides a method for improving the surface magnetic consistency of sintered NdFeB magnetic steel by screening cast pieces, reducing powder agglomeration, enhancing powder fluidity and realizing uniform and full orientation of magnetic powder through a die cavity design.
The aim of the invention is realized by the following technical scheme:
a method for improving the surface magnetic consistency of sintered NdFeB magnetic steel comprises the following steps:
s1, screening a neodymium iron boron cast sheet obtained by smelting;
s2, carrying out hydrogen crushing treatment on the screened cast sheet to obtain alloy powder;
s3, adding an antioxidant into the alloy powder, carrying out air flow grinding under the protection of nitrogen to obtain fine powder, sequentially adding a lubricant and aviation gasoline into the fine powder, stirring, and sieving;
and S4, molding the fine powder subjected to sieving treatment by using a molding die, and finally obtaining the neodymium iron boron through sintering treatment.
Preferably, the NdFeB is [ (PrNd) 1-x (RE) x ] a (TM) b (HM) c B d Fe 100-a-b-c-d Wherein x is more than or equal to 0 and less than or equal to 1, a is more than or equal to 29.5 and less than or equal to 33.5,0 and less than or equal to 5, c is more than or equal to 0 and less than or equal to 0.8,0.85 and d is more than or equal to 1.1.
Further preferably, RE is at least one of La, ce, Y, dy, tb, ho, gd;
TM is at least one of Al, cu, ga, co, mn;
HM is at least one of Nb, zr, hf, ti, V.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the thickness of the NdFeB casting sheet obtained by smelting in the step S1 is 0.15-0.45mm.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the thickness of the NdFeB casting sheet after the screening treatment in the step S1 is 0.285-0.305mm. The neodymium iron boron cast sheet microstructure columnar crystal distribution with the thickness of 0.285-0.305mm obtained through screening has obvious advantages compared with neodymium iron boron cast sheets with other thicknesses.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the temperature in the hydrogen crushing treatment process of the step S2 is 500-580 ℃, and the hydrogen content is less than or equal to 1200ppm.
Preferably, the antioxidant is added in the step S3 in an amount of 0.05-0.15% by mass of the alloy powder.
Preferably, the antioxidant in the step S3 is at least one of glycerol, zinc stearate, silicate, silicone oil and n-octane.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the average granularity of the air flow grinding powder in the step S3 is 2.8-3.2 mu m.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the mass ratio of the lubricant to the fine powder in the step S3 is 1: (0.2-1.2), the mass ratio of the gasoline to the fine powder is 1: (0.2-5).
Preferably, the lubricant is at least one of polyethylene oxide allyl ether and polyethylene oxide allyl glycidyl ether.
The invention adds gasoline on one hand to dilute the lubricant to have the effect similar to a solvent, and on the other hand, a certain amount of gasoline can also be added to protect magnetic powder from spontaneous combustion caused by contacting air.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the number of the screen meshes in the step S3 of screening treatment is 20-60. The invention can greatly improve the consistency of the magnetic powder particle orientation by controlling the mesh number of the sieve to be 20-60, the mesh number is too small to play a role, and the accumulation phenomenon can be generated when the mesh number is too large to be sieved, so that the sieving efficiency is greatly reduced.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the step S4 forming die comprises a magnetizing pole head for orientation, a non-magnetic conductive die and a powder distribution die cavity, wherein the powder distribution die cavity is arranged at the center of the magnetizing pole head, and magnetic alloy is inlaid at two sides of the die cavity.
Preferably, for products with different specifications, the die cavity position of the invention is required to be at the center of the polar head, specifically, 1/2B is less than or equal to A and less than or equal to B;
in addition, aiming at a cylindrical product, a principle of one out is adopted when the die design is required, wherein L=blank size, shrinkage coefficient and grinding amount;
preferably, the magnetic conductive alloy inlaid at the two sides of the die cavity is at least one of Cr12 die steel and 45# steel.
The invention improves the forming die, particularly improves the uniformity of the magnetic field in the die cavity by utilizing a special die cavity, ensures the uniform and full orientation of the magnetic powder, and greatly improves the surface magnetic consistency of the sintered NdFeB magnetic steel.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the magnetic field strength H is more than 2000Gs during the step S4 forming.
In the preparation method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel, the sintering temperature is 1000-1100 ℃ and the sintering time is long in the step S46-12h, vacuum degree 5×10 -2 Pa or below.
Compared with the prior art, the application has the following advantages:
1. firstly, screening out the throwing pieces with good columnar crystal tissue structure in the smelting process, and facilitating the crushing of the follow-up throwing pieces and the acquisition of magnets with neodymium-rich phase uniform distribution structures;
2. the invention reduces powder agglomeration through the screen mesh number of 20-60 in the screening treatment, enhances fluidity, is more beneficial to subsequent molding and orientation, and ensures that the magnetic powder passing through a die cavity is uniformly and fully oriented through the design of the die in the molding link;
3. according to the invention, through optimization of the sintering process, the shrinkage of the product in each direction is more uniform in the densification process, the influence of the oxygen content of the product, especially the cylindrical product, on the surface magnetic consistency is reduced, and the surface magnetic consistency of the product is greatly improved through optimization of each link.
Drawings
Fig. 1 is a schematic structural diagram of a forming mold in embodiment 1, wherein 1 is a magnetizing pole head for orientation, 2 is a non-magnetic conductive mold, 3 is a inlaid magnetic conductive alloy, and 4 is a powder distribution mold cavity, wherein 1/2B is equal to or less than a and equal to B, and L is equal to or less than blank size.
Detailed Description
The following are specific examples of the present invention, and the technical solutions of the present invention are further described, but the present invention is not limited to these examples.
Example 1:
s1, smelting raw materials to obtain NdFeB casting sheets PrNd with the thickness of 0.15-0.45mm and the brand number of N42 23.2 Ce 7 B 0.98 Al 0.3 Nb 0.1 Zr 0.1 Co 0.2 Cu 0.2 Ga 0.1 Fe 67.97 . Screening the NdFeB cast sheet obtained by smelting to obtain a NdFeB cast sheet with the thickness of 0.285-0.305 mm;
s2, placing the screened cast sheet in a hydrogen crushing furnace, and carrying out dehydrogenation treatment to obtain alloy powder, wherein the dehydrogenation temperature is 550 ℃, and the hydrogen content of the hydrogen crushing powder is 1000ppm;
s3, adding glycerol accounting for 0.1% of the mass of the alloy powder into the alloy powder, carrying out air flow grinding under the protection of nitrogen to obtain fine powder with the average granularity of 3.0 mu m, sequentially adding polyethylene oxide allyl glycidyl ether and aviation gasoline into the fine powder for stirring treatment, and then carrying out 30-mesh sieving treatment, wherein the mass ratio of the lubricant to the fine powder is (1): 1, the mass ratio of the gasoline to the fine powder is 1:2;
s4, molding the fine powder subjected to sieving treatment by using a molding die shown in fig. 1, wherein the magnetic field strength H is 2300Gs during molding, and finally the vacuum degree is 3×10 -2 And sintering at 1050 ℃ for 8 hours to obtain NdFeB with the product specification of 14-5.
Example 2:
s1, smelting raw materials to obtain NdFeB casting sheets PrNd with the thickness of 0.15-0.45mm and the brand number of N42 23.2 Ce 7 B 0.98 Al 0.3 Nb 0.1 Zr 0.1 Co 0.2 Cu 0.2 Ga 0.1 Fe 67.97 . Screening the NdFeB cast sheet obtained by smelting to obtain a NdFeB cast sheet with the thickness of 0.285-0.305 mm;
s2, placing the screened cast sheet in a hydrogen crushing furnace, and carrying out dehydrogenation treatment to obtain alloy powder, wherein the dehydrogenation temperature is 500 ℃, and the hydrogen content of the hydrogen crushing powder is 1200ppm;
s3, zinc stearate accounting for 0.1% of the alloy powder by mass is added into the alloy powder, air flow grinding is carried out under the protection of nitrogen to obtain fine powder with the average granularity of 2.8 mu m, polyethylene oxide allyl ether and aviation gasoline are sequentially added into the fine powder for stirring treatment, and then 20-mesh sieving treatment is carried out, wherein the mass ratio of the lubricant to the fine powder is 1:0.2, the mass ratio of the gasoline to the fine powder is 1:0.2;
s4, molding the fine powder subjected to sieving treatment by using a molding die shown in fig. 1, wherein the magnetic field strength H is 2100Gs during molding, and finally the vacuum degree is 5×10 -2 And (3) sintering at the temperature of 1000 ℃ for 8 hours under Pa to obtain the NdFeB.
Example 3:
the difference from example 1 is only that the molding die is a conventional die not embedded with a magnetically conductive alloy.
Example 4:
the difference from example 1 is that the thickness of the NdFeB casting sheet obtained by the screening treatment is 0.20-0.40mm.
Example 5:
the difference from example 1 is only that the mesh number of the sieving treatment is 10.
Comparative example 1:
the difference from example 1 is only that no neodymium iron boron cast sheet screening treatment was performed.
Comparative example 2:
the difference from example 1 is only that the fine powder was stirred without sieving.
Table 1: sintered NdFeB magnetic steel prepared in examples 1-5 and comparative examples 1-2 shows magnetic consistency detection results
| Examples | N pole center meter magnet | S pole center meter magnet | Magnetic difference value of central meter |
| Example 1 | 3350Gs | 3335Gs | 15Gs |
| Example 2 | 3280Gs | 3310Gs | 30Gs |
| Example 3 | 3350Gs | 3250Gs | 100Gs |
| Example 4 | 3330Gs | 3290Gs | 40Gs |
| Example 5 | 3360Gs | 3320Gs | 40Gs |
| Comparative example 1 | 3340Gs | 3260Gs | 80Gs |
| Comparative example 2 | 3360Gs | 3290Gs | 70Gs |
In summary, the invention screens out the throwing pieces with good columnar crystal tissue structure in the smelting process, which is helpful for the crushing of the subsequent throwing pieces and the acquisition of the magnets with neodymium-rich phase uniform distribution structure; the invention enhances fluidity by reducing powder agglomeration, is more beneficial to subsequent molding and orientation, and ensures that the magnetic powder passing through a die cavity is uniformly and fully oriented by the design of the die in the molding link; according to the invention, through optimization of the sintering process, the shrinkage of the product in each direction is more uniform in the densification process, the influence of the oxygen content of the product, especially the cylindrical product, on the surface magnetic consistency is reduced, and the surface magnetic consistency of the product is greatly improved through optimization of each link.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Various modifications or additions to the described embodiments may be made by those skilled in the art to which the invention pertains or may be substituted in a similar manner without departing from the spirit of the invention or beyond the scope of the appended claims.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Claims (10)
1. The method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel is characterized by comprising the following steps of:
s1, screening a neodymium iron boron cast sheet obtained by smelting;
s2, carrying out hydrogen crushing treatment on the screened cast sheet to obtain alloy powder;
s3, adding an antioxidant into the alloy powder, carrying out air flow grinding under the protection of nitrogen to obtain fine powder, sequentially adding a lubricant and aviation gasoline into the fine powder, stirring, and sieving;
and S4, molding the fine powder subjected to sieving treatment by using a molding die, and finally obtaining the neodymium iron boron through sintering treatment.
2. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the thickness of the NdFeB cast sheet obtained by smelting in the step S1 is 0.15-0.45mm.
3. The method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel according to claim 1, wherein the thickness of the NdFeB casting sheet after the screening treatment in the step S1 is 0.285-0.305mm.
4. The method for improving the surface magnetic consistency of the sintered NdFeB magnetic steel according to claim 1, wherein the temperature in the hydrogen crushing treatment process of the step S2 is 500-580 ℃, and the hydrogen content is less than or equal to 1200ppm.
5. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the average particle size of the air stream powder in the step S3 is 2.8-3.2 μm.
6. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the mass ratio of the lubricant to the fine powder in the step S3 is 1: (0.2-1.2), the mass ratio of the gasoline to the fine powder is 1: (0.2-5).
7. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the mesh number in the sieving treatment in the step S3 is 20-60.
8. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the forming die in the step S4 comprises a magnetizing pole head for orientation, a non-magnetic conductive die and a powder distribution die cavity, wherein the powder distribution die cavity is arranged in the center of the magnetizing pole head, and magnetic alloy is inlaid at two sides of the die cavity.
9. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the magnetic field strength H is more than 2000Gs during the forming in the step S4.
10. The method for improving the surface magnetic consistency of sintered NdFeB magnetic steel according to claim 1, wherein the sintering temperature in the step S4 is 1000-1100 ℃, the sintering time is 6-12h, and the vacuum degree is 5 multiplied by 10 -2 Pa or below.
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