CN114603145A

CN114603145A - Device and method for crushing/surface modification of sintered NdFeB SC cast sheet

Info

Publication number: CN114603145A
Application number: CN202110074306.1A
Authority: CN
Inventors: 永田浩; 刘仁辉; 武仁杰
Original assignee: Guorui Kechuang Rare Earth Functional Materials Ganzhou Co ltd; Jiangxi University of Science and Technology
Current assignee: Guorui Kechuang Rare Earth Functional Materials Ganzhou Co ltd; Jiangxi University of Science and Technology
Priority date: 2021-01-20
Filing date: 2021-01-20
Publication date: 2022-06-10

Abstract

The invention discloses a device and a method for crushing/surface modifying sintered NdFeB SC cast sheets. The invention provides a non-opposed type crushing device without a bottom nozzle, which can generate small-scale turbulence and vortex by changing the structure of an air flow, promote the rotation and stable collision of powder, reduce the surface distortion and lattice defects of the powder and promote the generation of spherical powder. The spheroidization of the powder improves the Hcj and Hk of the magnet, improves the degree of orientation of the powder in a magnetic field, and further improves the Br and the magnetization of the magnet. The device and the method can more stably crush the powder, have good powder orientation degree, and improve the performance and the yield of the magnet obtained by magnetic field forming and sintering.

Description

Device and method for crushing/surface modification of sintered NdFeB SC cast sheet

Technical Field

The invention relates to the technical field of metal powder processing, in particular to processing of neodymium iron boron powder.

Background

Nd-Fe-B sintered permanent magnet materials are mostly prepared from Nd-Fe-B powder through a powder metallurgy process, pressing and sintering. Nd-Fe-B powder is mostly prepared by adopting a rapid hardening sheet (also called a strip casting method, a strip throwing method and the like, and SC) and hydrogen pulverization (HD) process at present. The neodymium iron boron SC alloy cast sheet becomes very brittle and fragile after hydrogen crushing treatment, and can be further crushed and refined.

The conventional jet milling method (JM) for pulverizing Nd-Fe-B powder is to use high-speed airflow to drive powder to collide, so as to crush coarse powder and obtain micro powder. Fig. 1 to 3 show an opposite type (also called opposite type/opposite type) pulverizing apparatus belonging to a common jet mill in the prior art, which includes a powder feeder 1 ', a powder pulverizing chamber 2 ', a rotary classifier 3 ', a jet classifier 4 ' and a product powder recovery container 5 '; the powder feeder 1 'feeds powder to be pulverized into the powder pulverizing chamber 2'; the powder crushing chamber 2 'is provided with a plurality of nozzles 6', the nozzles 6 'are divided into a bottom nozzle arranged at the bottom and a side nozzle arranged on the side wall, and the high-speed airflow sprayed by the nozzles 6' drives the powder to move and collide for crushing; the rotary classifier 3 'is arranged in the powder crushing chamber 2' and positioned above the nozzle 6 ', and the crushed powder with the grain diameter meeting the requirement is sent into the air flow classifier 4'; the air classifier 4 'separates qualified and unqualified powder through air separation, and sends the qualified and unqualified powder into the product powder recovery container 5' or collects the qualified and unqualified powder and sends the collected powder back to the crushing device for crushing. In addition, the collision type (also called impact type) crushing device also comprises a powder feeder 1 ', a powder crushing chamber 2', a rotary type classifier 3 ', an air flow classifier 4' and a product powder recovery container 5 as shown in figure 4, wherein the bottom of the powder crushing chamber 2 'is provided with a nozzle 6, and the difference is that the powder crushing chamber 2' is also provided with an impact plate 7 ', the impact plate 7' can be arranged in a suspension way as shown in figure 4 or in the center of the bottom; the air flow is injected through the bottom nozzles 6 "to cause the powder to collide with the impact plate 7" and also to collide with each other, thereby increasing the pulverization efficiency. For preventing oxidation, nitrogen, argon, helium, xenon (N) is used as the pulverizing gas₂Ar, He, Xe), and the like. The pulverization gas generally contains a small amount of oxygen, water, oil, organic solvent, lubricant, antioxidant, etc. The classified gas can be recovered and pressurizedAnd then the waste water is recycled after being condensed.

The crushing force of the existing JM method is very high, but the obtained Nd-Fe-B series micro powder is often sharp in shape and has sharp corners, and the quantity of fine sharp powder is increased, so that the squareness and the magnetic performance of a magnet are deteriorated.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a device and a method for crushing/surface modifying sintered NdFeB SC cast sheets.

One of the technical schemes adopted by the invention for solving the technical problems is as follows:

the device for crushing/surface modifying the sintered NdFeB SC cast sheet comprises a crushing/surface modifying chamber, wherein the crushing/surface modifying chamber is provided with a plurality of side nozzles which are circumferentially arranged at intervals, and the side nozzles are arranged in a non-opposite mode; the inner side wall of the crushing/surface modification chamber is also provided with a plurality of first protrusions which are circumferentially arranged and protrude inwards.

One of the core points of the present invention is that, in the device for pulverizing/surface-modifying sintered nd-fe-b SC slabs according to the present invention, the plurality of side nozzles of the pulverizing/surface-modifying chamber are disposed in a non-opposing manner (which may also be referred to as non-colliding type/non-opposing type). In the opposed type pulverizing apparatus of the related art shown in fig. 1 to 3, the nozzles of the pulverizing chamber are opposed and opposed to each other, and the air flows collide with each other, and as shown in fig. 5, the nozzles are usually of 180 ° opposed type (fig. 5 (a), (b)), and the arrangement of the nozzles is usually a combination of the 180 ° opposed type (for example, a combination of a single 180 ° opposed type or a multi-layer 180 ° opposed type may be provided). Further, there are also 120 ° opposed type (fig. 5 (c) and (d)), 72 ° opposed type (fig. 5 (e) and (f)), and the like. In these cases, the powder is directly collided violently, regardless of whether the nozzles are distributed in the horizontal plane or the vertical plane, and therefore, they are not included in the present invention. Meanwhile, as shown in fig. 5, in these types of nozzles of the prior art, there is a case where powder collides within a distance of a radius r of the pulverization chamber from an outlet of a front end of the nozzle. In the collision type pulverizing apparatus shown in fig. 4 and 6, the powder collides with the wall or the impact plate strongly even in the radius r of the pulverizing chamber. The powder is likely to be crushed and damaged on the crystal surface by the violent collision, and the powder is likely to form a sharper corner, so that the magnet performance is lowered although the above-mentioned pulverizing apparatus in the prior art may achieve sufficient pulverization. Unlike the prior art, the side nozzle of the present invention is not the above-described arrangement of the prior art, but is non-opposing, non-colliding, and thus the "side nozzle is a non-opposing type" of the present invention may be defined as an arrangement that does not employ the above-described prior art nozzle structure.

In addition, the nozzles of the conventional jet mills are generally of the opposed type, and in order to generate a strong impact force, a straight-line or parallel type nozzle is used. That is, the opposing air flows are collided without dispersing the air flow as much as possible, and the powder is collided in a collision state of the strong air flows, thereby realizing the strong pulverization. The present invention relates to an apparatus for jet milling/surface modification, which avoids strong milling due to collision, and focuses more on the surface modification such as grinding, milling powder surface, and grinding powder in the flow of the whole jet. Therefore, as the non-opposing side nozzle, a diffusion nozzle (nozzle) is preferably used. By using the diffusion type nozzle, it is possible to generate a uniform air flow along the inner peripheral surface of the pulverization/surface modification chamber, thereby generating a rotating turbulent air flow along the first convex portion at the inner peripheral portion of the pulverization/surface modification chamber, and thus more effectively generating the grinding effect of the powder. In the present invention, since the gas flow ejected from the side nozzle outlet has 3-dimensional diffusion, the particle size and shape of the powder are relatively more uniform in a wide diffusion range.

In a specific embodiment, the non-opposing arrangement of the side nozzles of the pulverizing/surface modifying chamber means that: the side nozzles are arranged around a central point; as shown in fig. 7, a connecting line formed by the outlet of any side nozzle and the central point forms an included angle with the flowing direction of the air flow ejected by the side nozzle. The center point is a virtual point rather than a solid point, and may be a geometric center point of the outlets of the side nozzles, for example, a center of a circle in which the outlets of the side nozzles are located together, or a center of a sphere in which the outlets of the side nozzles are located together. Where the comminution/surface modification chamber is cylindrical, the centre point may be located on the central axis of the cylindrical comminution/surface modification chamber.

The side nozzles may be located on the same plane parallel to the ground. In this case, the outlets of the side nozzles may be located together on a circle parallel to the ground, the center of which is the center point M, as shown in fig. 7 (a) to (d).

The side nozzles may not be on the same plane, as shown in fig. 7 (e) - (f), the side nozzles may be disposed at different heights, the projections of the outlets of the side nozzles on the ground may be located on a circle, the center of the circle may be located on the central axis, the center point is also located on the central axis, and the projection of the center point on the ground may coincide with the center of the circle. The plurality of side nozzles may be divided into a plurality of groups, and the side nozzles (at least two) in each group are equidistant from the center point.

Another core point of the present invention is that the inner sidewall of the pulverizing/surface-modifying chamber is further provided with a plurality of circumferentially arranged first protrusions protruding inwardly. The shape of the first convex portion may be a semi-cylindrical shape (as shown in fig. 8), a triangular cylindrical shape (as shown in fig. 7), a quadrangular cylindrical shape, or the like.

In one embodiment, the crushing/surface modification chamber is provided with a bump at the center of the bottom. The projections extend from the bottom to the upper part of the pulverization/surface modification chamber, as shown in FIGS. 8 (a) to (f) and FIGS. 12 to 13. The shape of the convex block can be hemispherical, semi-ellipsoidal, semi-egg-shaped, square column, trapezoidal truncated cone, cylindrical or conical truncated cone, and the like.

In one embodiment, the projection is further provided with a plurality of second protrusions which are circumferentially arranged and protrude outwards. The first projection has a projection direction opposite to that of the second projection, as shown in fig. 8 (g) and fig. 14 to 15. The second convex part can be in the shape of a semi-cylinder, a triangular prism, a quadrangular prism or the like.

In the present invention, the pulverization/surface modification chamber has a cylindrical shape. The "inward" direction of the central axis of the cylindrical shape, i.e., the "inward protrusion" of the first protrusion, may be understood as protruding from the inner side wall of the pulverization/surface modification chamber toward the central axis direction, and the "outward protrusion" of the second protrusion, may be understood as protruding away from the central axis direction, i.e., from the central axis direction toward the inner side wall of the pulverization/surface modification chamber.

The purpose of providing the first projections/second projections in the present invention is to generate small-scale turbulence and vortex in the air flow rotating along the first projections/second projections in the pulverization/surface modification chamber, as shown in fig. 9, to promote rotation and smooth collision of the powder, to reduce surface distortion and lattice defects of the powder, and to promote generation of spherical powder.

The first protrusions, projections (if any), and second protrusions (if any) may be provided only in a part (e.g., lower part) of the pulverization/surface modification chamber, or may be provided in the entire pulverization/surface modification chamber. The positions of the first convex parts, the bumps (if any) and the second convex parts (if any) correspond to each other, and the pulverization/surface modification of the powder is carried out at the positions of the first convex parts, the bumps (if any) and the second convex parts (if any) in the pulverization/surface modification chamber, between the first convex parts, or between the first convex parts and the bumps, or between the first convex parts and the second convex parts.

In one embodiment, the device further comprises a powder supply machine, a rotary classifier, an airflow classifier and a product powder recovery container; the powder feeder is communicated with the crushing/surface modification chamber; the rotary classifier is arranged in the crushing/surface modification chamber and is positioned above the side nozzle and the first convex part; the rotary type classifier can provide upward movement power to the powder in the pulverization/surface modification chamber, preventing the powder from accumulating at the bottom of the pulverization/surface modification chamber. The airflow classifier is connected with the rotary classifier; the product powder recovery container is connected with the airflow classifier.

In one embodiment, the gas flow ejected from the side nozzle is an inert gas having an oxygen content of 2ppm to 800 ppm. More preferably, an oxygen content in the gas stream of 2ppm to 200ppm is effective.

The second technical scheme adopted by the invention for solving the technical problems is as follows:

the crushing/surface modification method of the sintered NdFeB SC cast sheet by utilizing the device comprises the steps of crushing the sintered NdFeB SC cast sheet into coarse powder by hydrogen, and further crushing the coarse powder in the crushing/surface modification chamber under the driving of airflow sprayed by the side nozzle to obtain micro powder with the average particle size of 1-10 mu m; the gas flow is inert gas with the oxygen content of 2 ppm-800 ppm.

The fine powder having an average particle diameter of 1 to 10 μm obtained by the above method is molded by a magnetic field molding machine and sintered in a vacuum or inert gas to obtain an Nd-Fe-B sintered permanent magnet material (also called a sintered magnet or a sintered magnet).

In one embodiment, the raw material of the sintered nd-fe-B SC cast sheet includes 5.0 at% to 5.8 at% of B. More preferably, the content of B in the raw material of the sintered NdFeB SC cast sheet is in the range of 5.2 at% to 5.6 at%.

In one embodiment, the raw material of the sintered nd-fe-b SC cast sheet contains Ga at 0.05 at% to 1.0 at%. More preferably, the Ga content in the raw material of the sintered NdFeB SC cast sheet is in the range of 0.1 at% to 0.8 at%.

More preferably, an oxygen content in the gas stream of 2ppm to 200ppm is effective.

The present invention provides a flat type (without bottom nozzle) and non-opposed type (also called non-colliding type/non-opposed type) pulverizing apparatus different from the conventional one, and it is found that the pulverization can be carried out more stably, and the performance and yield of the magnet after the magnetic field forming, sintering and heat treatment are improved. It is presumed that the composite effect of good powder orientation degree is caused by the phenomenon of powder surface damage, the reduction of powder internal deformation, the reduction of powder lattice defects, the spheroidization of powder, and the reduction of the generation of ultrafine powder.

The Nd-Fe-B sintered permanent magnet material of the present invention contains Nd, Fe, B as essential elements, 12 at% to 16 at% of Co, 3 at% or less of rare earth elements (including Y, La, Ce, Pr, Gd, Tb, Dy, Ho, etc.) mainly composed of Nd, 2 at% or less of Al, Cu, Ga, Si, Mn, Cr, Ge, Ni, 1 at% or less of Ti, Zr, Hf, W, V, Nb, Mo, Ta, Sn, Bi, Sb, at least 1 or more of the elements, 4 at% to 9 at% of B, and 1 at% or less of trace elements such as C, O, N, H, S, P. The neodymium iron boron powder is made into a sintered magnet by a powder metallurgy method, has a remanence of more than 13kGs and a coercive force of more than 10kOe, and is the magnet with the highest performance in the world.

The squareness Hk/Hcj (%) in the demagnetization curve of a magnet is an important practical index such as heat resistance and thermal demagnetization of the magnet.

After the neodymium iron boron SC alloy cast sheet is subjected to hydrogen crushing treatment, the coarse powder in a broken state is crushed in the crushing/surface modification chamber, and the crushing/surface modification chamber has a crushing effect actually. In the embodiment of the present invention, the non-opposing, non-colliding, and smooth collision between the powders reduces lattice defects on the surface of the powders and inside the powders, and has a surface modification effect of the powder shape (spheroidization: turning sharp corners into spheroidization, etc.). Thus, not only the pulverization, but also the "surface improvement" is carried out in the pulverization/surface modification chamber of the present invention.

The gas in the pulverization step is mainly an inert gas and oxygen, but may contain a small amount of unavoidable impurities such as water, oil, organic solvent, and organic polymer. The inert gas in the present invention refers to an inert gas, typically nitrogen (N)₂) Argon (Ar) and helium (He). In order to reduce the cost, the used inert gas may be recovered by filtering off residual powder, ultrafine powder, or the like.

The apparatus of the present invention has a special structure (first convex portion, projection, second convex portion) in the center of the inner wall and bottom of the pulverization/surface modification chamber. Since the material of these structures is a material that comes into contact with the powder in flow, a hard material having wear resistance is preferable. In addition, no special material is required except that the direction of the side nozzles is set to a non-opposing type. It is preferable to use SUS of ordinary gloss for piping and parts. In addition, since the side nozzle and the rotary classifier classifying wheel are easily worn, it is preferable to use a hard material. In order to control the amount of oxygen, the connection portion of the pipe and the valve are mostly made of a rubber gasket and a sealant, and high sealability is preferred. In addition, in a portion where wear is severe, it is preferable to use a wear-resistant material such as alumina or zirconia.

Preferably, the first convex portion of the inner side wall is also integrally processed at the same time when the pulverizing/surface-modifying chamber is manufactured. In addition, if the simple installation and replacement of the first convex portion are considered, the first convex portion having a semi-cylindrical shape, a triangular cylindrical shape or a quadrangular cylindrical shape may be separately processed and manufactured by embedding, screwing, bonding, welding, etc. on the inner wall of the pulverization/surface modification chamber. The first convex part is preferably made of a material having good wear resistance and using wear-resistant consumables. However, since the wear-resistant consumable material is a material that is difficult to process, it is also possible to use an iron-based material such as stainless steel or high-strength steel, and to replace the wear-resistant consumable material after it is worn.

Preferably, the projection in the center of the bottom is also integrally machined at the same time as the crushing/surface-modifying chamber is made. In addition, if the simple installation and replacement of the bump at the center of the bottom is important, the bump may be manufactured by machining a hemispherical, semi-ellipsoidal, semi-egg-shaped, cylindrical or truncated cone-shaped bump separately and then embedding, screwing, bonding, welding, etc. at the bottom of the pulverization/surface modification chamber. The material of the lug preferably has good wear resistance, and wear-resistant consumables are used. However, since the wear-resistant consumable material is a material that is difficult to process, it is also possible to use an iron-based material such as stainless steel or high-strength steel, and to replace the wear-resistant consumable material after it is worn.

Preferably, a second convex part is further arranged on the lug. In the pulverization/surface modification chamber, the air flow rotating along the outer periphery of the bump is made to generate small-scale turbulence and vortex along the second convex portion, thereby promoting the rotation and smooth collision of the powder, reducing the lattice defects of the powder, and promoting the generation of spherical powder. Preferably, the bump and the second projection are integrally processed at the same time when the pulverization/surface modification chamber is manufactured. In addition, if the simple installation and replacement of the second convex portion are important, the second convex portion having a semi-cylindrical shape, a triangular cylindrical shape or a quadrangular cylindrical shape may be separately processed and manufactured by embedding, screwing, bonding, welding, etc. on the bump. The second convex part is preferably made of a material having good wear resistance and using wear-resistant consumables. However, since the wear-resistant consumable material is a material that is difficult to process, it is also possible to use an iron-based material such as stainless steel or high-strength steel, and to replace the wear-resistant consumable material after it is worn.

The size of the pulverization/surface modification chamber according to the present invention is generally expressed by the diameter of the cylindrical pulverization/surface modification chamber, and the expression of the size of the pulverization chamber in the conventional art is referred to. The crushing/surface modification chamber according to the present invention is generally 100mm to 400mm, and is referred to as 100 type to 400 type. For example, the term "100" means a crushing chamber having a diameter of about 100mm, and the term "400" means a crushing chamber having a diameter of about 400 mm. The 100 type can be used for small amount test of 1 kg, and the 400 type can be used for large amount production of 1000 kg. In the apparatus of the present invention, the bottom surface of the pulverization/surface modification chamber is flat, and the side wall is provided with a plurality of side nozzles arranged in a non-opposing manner.

The equipment, reagents, processes, parameters and the like related to the invention are conventional equipment, reagents, processes, parameters and the like except for special description, and no embodiment is needed.

All ranges recited herein are intended to encompass all points within the range.

As used herein, "about" or "about" and the like refer to a range or value within plus or minus 20 percent of the stated range or value.

Compared with the background technology, the technical scheme has the following advantages:

1. the invention changes the direction of the side nozzles into the non-opposite direction, removes the bottom nozzles, adjusts the air flow direction in the plane parallel to the bottom surface, and makes the powder rotate in a circle drawing mode, so that the powder can be more stably crushed, the sharp powder is reduced, the corners of the powder are easy to round, the powder is close to a sphere, the generation of fine powder is reduced, the powder orientation degree is good, the magnetic conductivity is improved, the yield is improved, and the magnet performance (coercive force, squareness and magnetization intensity) is improved.

2. According to the invention, the first convex part, the convex block and the second convex part are arranged in the crushing/surface modification chamber, so that a large amount of small annular air flow is generated in the crushing process, the crushing efficiency can be further improved, and the yield and the magnet performance are improved.

3. When the content of Ga or B contained in the Nd-Fe-B SC cast sheet element is within a certain range, the edges of the powder are easier to round, the powder orientation degree is good, the magnetic permeability is improved, and the magnetic performance is further improved, presumably because most of fine 6-13-1 phase exists in the grain boundary.

4. The invention is applied to the crushing of the sintered NdFeB SC cast sheet and can also be applied to the crushing of other brittle materials.

Drawings

Fig. 1 is a schematic side view of a prior art opposed type crushing apparatus.

Fig. 2 is a perspective view of a crushing apparatus of an opposed type in the related art.

Fig. 3 is a schematic sectional view of a facing type pulverizing apparatus in the prior art.

Fig. 4 is a schematic cross-sectional view of a prior art impact type pulverizing apparatus.

Fig. 5 is a schematic view of a nozzle and an air flow of a counter type pulverizer in the related art, in which (a) is a 180 ° counter type cross-sectional view, (b) is a plan view of (a), (c) is a 120 ° counter type cross-sectional view, (d) is a plan view of (c), (e) is a 72 ° counter type cross-sectional view, and (f) is a plan view of (e). The air flow from the nozzle is indicated by the large arrows.

Fig. 6 is a schematic view of a nozzle and an air flow of a collision type pulverizer according to the prior art, in which (a) is a 180 ° opposed type sectional view, (b) is a plan view of (a), (c) is a sectional view of one of 180 ° opposed type but different in nozzle height, (d) is a plan view of (c), (e) is a sectional view of the other of 180 ° opposed type but different in nozzle height, and (f) is a plan view of (e). The air flow from the nozzle is indicated by the large arrows.

Fig. 7 is one of schematic views of a non-opposing type pulverizing/surface modifying apparatus of the present invention, side nozzles and an air flow, and a first convex portion is provided on an inner wall of a pulverizing/surface modifying chamber, wherein (a) is a sectional view in the case of two side nozzles having the same height, (b) is a plan view of (a), (c) is a sectional view in the case of four side nozzles having the same height, (d) is a plan view of (c), (e) is a sectional view in the case of two side nozzles having different heights, and (f) is a plan view of (e). The air flow from the side nozzles is indicated by the large arrows, the center point M.

Fig. 8 is a schematic view of a non-opposed type pulverizing/surface modifying apparatus of the present invention, and a second side nozzle and an air flow, wherein a first convex portion is provided on an inner wall of the pulverizing/surface modifying chamber, and a convex portion is provided at a center of a bottom of the pulverizing/surface modifying chamber, wherein (a) is a sectional view of one of two side nozzles having the same height, (b) is a plan view of (a), (c) is a sectional view of the other of two side nozzles having the same height, (d) is a plan view of (c), (e) is a sectional view of the other of the two side nozzles having the same height, and (f) is a plan view of (e), angles of the side nozzles of (a), (c), and (e) are different, and air flows jetted from the side nozzles are indicated by large arrows. (g) The top view of the case where the second convex portion is further provided on the surface of the bump.

Fig. 9 is a view for explaining the principle of the present invention in which the first protrusion/projection/second protrusion is provided so that the air flow rotating along the first protrusion/projection/second protrusion generates small-scale turbulence and vortex. The air flow is indicated by dashed lines and the powder rotation direction by dotted horizontal lines.

FIG. 10 is a schematic sectional view of a non-opposing type pulverizing/surface modifying apparatus according to example 1 of the present invention.

FIG. 11 is a schematic plan view of a non-opposing type crushing/surface modifying apparatus according to example 1 of the present invention.

FIG. 12 is a schematic sectional view of a non-opposing type pulverizing/surface modifying apparatus according to example 2 of the present invention.

FIG. 13 is a schematic plan view of a non-opposing type pulverizing/surface modifying apparatus according to example 2 of the present invention.

FIG. 14 is a schematic sectional view of a non-opposing type pulverizing/surface modifying apparatus according to example 3 of the present invention.

FIG. 15 is a schematic plan view of a non-opposing type pulverizing/surface modifying apparatus according to example 3 of the present invention.

FIG. 16 is a schematic perspective view of an apparatus for two-stage pulverization using the non-opposed pulverization/surface modification apparatus of the present invention in example 7 of the present invention.

FIG. 17 is a schematic sectional view of an apparatus for two-stage pulverization using a prior art opposed pulverization apparatus in combination with the non-opposed pulverization/surface modification apparatus of the present invention in example 7 of the present invention, wherein the pulverization/surface modification chamber is provided with first protrusions. The airflow is indicated by the dashed line.

FIG. 18 is a second cross-sectional view of an apparatus for two-stage pulverization using a prior art opposed pulverization apparatus in combination with a non-opposed pulverization/surface modification apparatus of the present invention in example 7 of the present invention, wherein the pulverization/surface modification chamber is provided with a first protrusion and a projection, and the projection is further provided with a second protrusion. The airflow is indicated by the dashed line.

FIG. 19 is a schematic sectional view of an apparatus for two-stage pulverization using a non-opposed pulverization apparatus in combination with the non-opposed pulverization/surface modification apparatus of the present invention in example 8 of the present invention, wherein the pulverization/surface modification chamber is provided with first protrusions. The airflow is indicated by the dashed line.

FIG. 20 is a second cross-sectional view of an apparatus for two-stage pulverization using a non-opposed pulverization apparatus in combination with the non-opposed pulverization/surface modification apparatus of the present invention in example 8 of the present invention, wherein the pulverization/surface modification chamber is provided with a first protrusion and a projection, and the projection is further provided with a second protrusion. The airflow is indicated by the dashed line.

Reference numerals:

the opposite type crushing device in the prior art comprises: a powder feeder 1 ', a powder pulverizing chamber 2', a rotary classifier 3 ', an air classifier 4', a product powder recovery container 5 ', and a nozzle 6';

of the colliding type crushing devices in the prior art: a powder feeder 1 ", a powder crushing chamber 2", a rotary classifier 3 ", an air classifier 4", a product powder recovery container 5 ", a nozzle 6", an impact plate 7 ";

the non-opposed type crushing/surface modification apparatus of the present invention comprises: a powder feeder 1, a pulverization/surface modification chamber 2, a rotary classifier 3, an air classifier 4, a product powder recovery container 5, a side nozzle 6, a first convex part 7, a bump 8, and a second convex part 9; the nozzle 6' ″ of the non-opposed type crushing apparatus;

a center point M.

Detailed Description

The invention is further illustrated by the following figures and examples.

Example 1

Referring to fig. 10 to 11, the device for grinding/surface modification of the sintered nd-fe-b SC cast piece of the present embodiment includes: a powder feeder 1, a pulverization/surface modification chamber 2, a rotary classifier 3, an air classifier 4, and a product powder recovery container 5; the powder feeder 1 is communicated with the crushing/surface modification chamber 2, and the powder feeder 1 can feed the powder to be crushed into the crushing/surface modification chamber 2; the crushing/surface modification chamber 2 is cylindrical and is provided with a plurality of side nozzles 6, and high-speed airflow sprayed by the side nozzles 6 drives powder to move and collide for crushing; the rotary classifier 3 is arranged in the crushing/surface modification chamber 2 and positioned above the plurality of side nozzles 6, and powder with the particle size meeting the requirement after crushing is sent into the air classifier 4; the air classifier 4 is connected with the rotary classifier 3, the product powder recovery container 5 is connected with the air classifier 4, the air classifier 4 separates qualified and unqualified powder through air flow separation, and the qualified and unqualified powder is sent into the product powder recovery container 5 or collected to be sent back to the crushing device again for crushing.

In this embodiment, the comminution/surface modification device is of the 300 type, i.e. the cylindrical comminution/surface modification chamber 2 has a diameter of about 300mm and is provided with four side nozzles 6, the four side nozzles 6 being located in a plane parallel to the ground and being arranged symmetrically about a central point, which may be understood as the centre of a circle in which the outlets of the four side nozzles 6 together lie, which may be located on the central axis of the cylindrical comminution/surface modification chamber 2. The line connecting the outlet of each side nozzle 6 and the center point forms an included angle with the flow direction of the air flow sprayed by the side nozzle 6, namely, the air flow sprayed by the side nozzle 6 does not pass through the center of the circle where the outlet of the side nozzle 6 is located. The lower part of the inner side wall of the crushing/surface modification chamber 2 is also provided with 16 first convex parts 7 which are arranged circumferentially and are convex inwards, and the first convex parts 7 are semi-cylindrical, have the radius r of 15mm and the height of 150mm and are made of SUS316 stainless steel. The first projection 7 corresponds to the position of the side nozzle 6.

The raw materials for preparing the sintered nd-fe-b SC cast sheet of the embodiment: Pr-Nd-13 at%, Tb-0.2 at%, B-5.7 at%, Ga-0.3 at%, Al-0.9 at%, Cu-0.1 at%, Co-1.0 at%, Mn-0.015 at%, Cr-0.02 at%, and the balance Fe and inevitable impurities.

600kg of raw materials are smelted by adopting a medium-frequency induction rapid hardening furnace to obtain an SC cast piece, and the average thickness of the SC cast piece is 0.4 mm. Charging SC cast sheet into hydrogen powderThe SC cast pieces were crushed in a crushing apparatus under a hydrogen atmosphere of 0.095MPa, and then subjected to a dehydrogenation treatment at a temperature of 500 ℃ for 6 hours. The hydrogen-pulverized raw material was roughly divided into 3 equal parts, and 1 part was charged into the non-opposed/non-colliding 300-type pulverizer of this example (4 side nozzles). The remaining 2 equal portions were fed into a 300-type opposed pulverizer (4 nozzles) as shown in FIGS. 1 to 3 and a 300-type colliding pulverizer (1 nozzle) as shown in FIG. 4, respectively. The nitrogen pressure of each nozzle was 5kg/cm²Respectively pulverizing to obtain fine powders.

The powders having different oxygen contents obtained by the respective pulverizing apparatuses were compacted in an oriented magnetic field of 2.4T (Tesla) of 0.2ton/cm²The pressure of (2) was pressed into a block of 30mm by 30 mm. Thereafter, each block was sintered at 980 ℃ to 1100 ℃ for 5 hours, heat-treated at 850 ℃ for 1 hour, heat-treated at 600 ℃ for 1 hour, and heat-treated at 480 ℃ for 3 hours in a vacuum sintering furnace. Then, each magnet was processed into a 10mm cube, and the magnet performance was evaluated by a BH magnet performance apparatus, and the performance of the powder obtained by each pulverizing method is shown in table 1 by comparison.

TABLE 1 comparison of the properties of the powders obtained in example 1 by the respective comminution methods

Note: FSSS particle size: average particle size evaluation by Fisher-Sub-Sieve-Sizer method.

The function is as follows: in the examples of the present invention, the magnet performance was high despite the large average particle diameter. This is the non-opposed/non-colliding type pulverizing method of the present invention, and the powder is rotated by the swirling flow generated by the action of the first convex portion 7 on the inner wall of the pulverizing/surface modifying chamber 2to which the powder is subjected during rotation, and as the pulverizing impact force on the powder is reduced, the powder is not only spheroidized but also the amount of lattice defects generated on the surface of the powder and in the powder is reduced. According to the theoretical analysis and understanding of the nucleation field of the Nd-Fe-B system sintered magnet, ideal powder particles improve the magnet properties, particularly the coercive force and squareness, of the Nd-Fe-B system sintered magnet. Further, it is also possible to analyze and understand the principle that the average grain size of the present invention is larger than the rotating magnetic moment of the magnetic field orientation, and the Br value of the magnet of the present invention having a large average grain size is larger.

Example 2

Referring to fig. 12 to 13, the device for grinding/surface modification of the sintered nd-fe-b SC cast piece of the present embodiment includes: a powder feeder 1, a pulverization/surface modification chamber 2, a rotary classifier 3, an air classifier 4, and a product powder recovery container 5; the powder feeder 1 is communicated with the crushing/surface modification chamber 2, and the powder feeder 1 can feed the powder to be crushed into the crushing/surface modification chamber 2; the crushing/surface modification chamber 2 is cylindrical and is provided with a plurality of side nozzles 6, and high-speed airflow sprayed by the side nozzles 6 drives powder to move and collide for crushing; the rotary classifier 3 is arranged in the crushing/surface modification chamber 2 and positioned above the plurality of side nozzles 6, and powder with the particle size meeting the requirement after crushing is sent into the air classifier 4; the air classifier 4 is connected with the rotary classifier 3, the product powder recovery container 5 is connected with the air classifier 4, the air classifier 4 separates qualified and unqualified powder through air flow separation, and the qualified and unqualified powder is sent into the product powder recovery container 5 or collected to be sent back to the crushing device again for crushing.

This embodiment is different from the pulverizing/surface-modifying apparatus of embodiment 1 in that a boss 8 is further fixed to the center of the bottom of the pulverizing/surface-modifying chamber 2 by a screw, and the boss 8 is cylindrical, has a diameter of 200mm and a height of 150mm, and is made of stainless steel made of SUS 316. That is, the pulverizing/surface-modifying apparatus of the present embodiment is provided with both the first protrusions 7 and the projections 8. Except for this, all the magnets were prepared by pulverizing under the same conditions as in example 1, and the properties of the prepared magnets of example 2 are shown in table 2.

TABLE 2 comparison of the properties of the powders obtained in example 2 by the respective comminution methods

The function is as follows: in example 2, since the projection 8 was provided at the center of the bottom of the pulverization/surface modification chamber 2, the swirling flow was accelerated and the spheroidization of the powder was promoted. The results show that the magnet properties, particularly the coercive force, are improved as compared with example 1 according to the nucleation field theory of the Nd-Fe-B system sintered magnet.

Example 3

Referring to fig. 14 to 15, the device for grinding/surface modification of the sintered nd-fe-b SC cast piece of the present embodiment includes: a powder feeder 1, a pulverization/surface modification chamber 2, a rotary classifier 3, an air classifier 4, and a product powder recovery container 5; the powder feeder 1 is communicated with the crushing/surface modification chamber 2, and the powder feeder 1 can feed the powder to be crushed into the crushing/surface modification chamber 2; the crushing/surface modification chamber 2 is cylindrical and is provided with a plurality of side nozzles 6, and high-speed airflow sprayed by the side nozzles 6 drives powder to move and collide for crushing; the rotary classifier 3 is arranged in the crushing/surface modification chamber 2 and positioned above the plurality of side nozzles 6, and powder with the particle size meeting the requirement after crushing is sent into the air classifier 4; the air classifier 4 is connected with the rotary classifier 3, the product powder recovery container 5 is connected with the air classifier 4, the air classifier 4 separates qualified and unqualified powder through air flow separation, and the qualified and unqualified powder is sent into the product powder recovery container 5 or collected to be sent back to the crushing device again for crushing.

In this embodiment, the comminution/surface modification device is of the 300 type, i.e. the cylindrical comminution/surface modification chamber 2 has a diameter of about 300mm and is provided with four side nozzles 6, the four side nozzles 6 being located in a plane parallel to the ground and being arranged symmetrically about a central point, which may be understood as the centre of a circle in which the outlets of the four side nozzles 6 together lie, which may be located on the central axis of the cylindrical comminution/surface modification chamber 2. The line connecting the outlet of each side nozzle 6 and the center point forms an included angle with the flow direction of the air flow sprayed by the side nozzle 6, namely, the air flow sprayed by the side nozzle 6 does not pass through the center of the circle where the outlet of the side nozzle 6 is located. The lower part of the inner side wall of the crushing/surface modification chamber 2 is also provided with 16 first convex parts 7 which are arranged circumferentially and are convex inwards, and the first convex parts 7 are semi-cylindrical, have the radius r of 15mm and the height of 150mm and are made of SUS316 stainless steel. The first projection 7 corresponds to the position of the side nozzle 6. The center of the bottom of the crushing/surface modification chamber 2 is also fixed with a projection 8 by a screw, and the projection 8 is cylindrical, has a diameter phi of 200mm and a height of 150mm, and is made of SUS316 stainless steel.

This embodiment is different from the crushing/surface-modifying apparatus of embodiment 2 in that the second convex portions 9, which are 10 semicylindrical and have a radius r of 12mm and a height of 150mm, are further fixed by screws on the outer side surfaces of the projections 8, and may be made of stainless steel made of SUS 316. That is, the pulverizing/surface-modifying apparatus of the present embodiment is provided with the first protrusions 7, the projections 8, and the second protrusions 9at the same time. Except for this, all the magnets were prepared by pulverizing under the same conditions as in example 1, and the properties of the prepared magnet of example 3 are shown in table 3.

TABLE 3 comparison of the properties of the powders obtained in example 3 by the respective comminution methods

The function is as follows: in example 3, since the second convex portion 9 is formed to protrude from the outer peripheral surface of the projection 8at the center of the bottom of the pulverization/surface modification chamber 2, the eddy component is increased, and the spheroidization of the powder is further promoted. The results show that the magnet performance, particularly the coercive force, is further improved according to the nucleation field theory of the Nd-Fe-B sintered magnet as compared with examples 1 and 2.

Example 4

The crushing/surface modification's of sintered neodymium iron boron SC cast piece device of this embodiment includes: a powder feeder 1, a pulverization/surface modification chamber 2, a rotary classifier 3, an air classifier 4, and a product powder recovery container 5; the powder feeder 1 is communicated with the crushing/surface modification chamber 2, and the powder feeder 1 can feed the powder to be crushed into the crushing/surface modification chamber 2; the crushing/surface modification chamber 2 is cylindrical and is provided with a plurality of side nozzles 6, and high-speed airflow sprayed by the side nozzles 6 drives powder to move and collide for crushing; the rotary classifier 3 is arranged in the crushing/surface modification chamber 2 and positioned above the plurality of side nozzles 6, and powder with the particle size meeting the requirement after crushing is sent into the air classifier 4; the air classifier 4 is connected with the rotary classifier 3, the product powder recovery container 5 is connected with the air classifier 4, the air classifier 4 separates qualified and unqualified powder through air flow separation, and the qualified and unqualified powder is sent into the product powder recovery container 5 or collected to be sent back to the crushing device again for crushing.

In this embodiment, the comminution/surface modification device is of the 200 type, i.e. the cylindrical comminution/surface modification chamber 2 has a diameter of about 200mm and is provided with six side nozzles 6, the six side nozzles 6 being located in a plane parallel to the ground and being arranged symmetrically about a centre point, which is understood to be the centre of a circle in which the outlets of the six side nozzles 6 together are located, the centre point being able to be located on the central axis of the cylindrical comminution/surface modification chamber 2. The line connecting the outlet of each side nozzle 6 and the center point forms an included angle with the flow direction of the air flow sprayed by the side nozzle 6, namely, the air flow sprayed by the side nozzle 6 does not pass through the center of the circle where the outlet of the side nozzle 6 is located. The lower part of the inner side wall of the crushing/surface modification chamber 2 is also provided with 30 first convex parts 7 which are circumferentially arranged and protrude inwards, and the first convex parts 7 are square columns, 10mm in side length and 150mm in height and are made of SUS316 stainless steel. The first projection 7 corresponds to the position of the side nozzle 6.

The raw materials for preparing the sintered nd-fe-b SC cast sheet of the embodiment: Pr-Nd-13 at%, B-5.6 at%, Ga-0.2 at%, Al-0.6 at%, Cu-0.4 at%, Co-2.0 at%, Mn-0.02 at%, Cr-0.05 at%, and the balance of Fe and inevitable impurities.

600kg of raw materials are smelted by adopting a medium-frequency induction rapid hardening furnace to obtain an SC cast piece, and the average thickness of the SC cast piece is 0.4 mm. The SC cast piece was charged into a hydrogen pulverizer, treated in a hydrogen atmosphere of 0.07MPa to crush the SC cast piece, and then subjected to dehydrogenation treatment at 550 ℃ for 4 hours. The hydrogen-pulverized raw material was roughly divided into 3 equal parts, and 1 was charged into the 200-type apparatus of the non-opposing/non-colliding type of this example (6 side nozzles). The remaining 2 equal parts were charged into the opposed type pulverizing apparatus (200 type, 4 nozzles) shown in fig. 1 to 3 and the opposed type pulverizing apparatus (200 type, 1 nozzle) shown in fig. 4, respectively. The nitrogen pressure of each nozzle was 7kg/cm²The nitrogen gas contained oxygen in an amount of 1ppm, 2ppm, 10ppm, 200ppm, 800ppm, 1600ppm on average, and was pulverized to obtain a fine powder.

The powders having different oxygen contents obtained by the respective pulverizing apparatuses were compacted in an oriented magnetic field of 2.4T (Tesla) at 0.25ton/cm²The pressure of (2) was pressed into a block of 30mm by 30 mm. Thereafter, each block was sintered at 1000 ℃ to 1100 ℃ for 5 hours in a vacuum sintering furnace and heat-treated at 800 ℃ for 1 hour. Heat treatment at 600 ℃ for 1 hour and 480 ℃ for 3 hours. Then, each magnet was processed into a 10mm cube, and the magnet performance was evaluated by a BH magnet performance apparatus, and the performance of the powder obtained by each pulverizing method is shown in table 4 by comparison.

Table 4 comparison of properties of powders obtained by respective pulverization methods in example 4

The function is as follows: the examples of the present invention are not limited to the average particle diameter, the magnet performance. The method is compared with a non-frontal collision and non-collision type crushing method, and along with the reduction of the crushing impact capacity to the powder, the lattice defects generated on the surface of the powder particles are reduced, so that the magnetic performance, particularly the remanence and the squareness value of the nucleation field coercive force type neodymium iron boron can be improved. In addition, the magnet of the present invention having a large average grain size has a larger Br value according to the principle of magnetic moment of magnetic field orientation.

In addition, with respect to the average oxygen content in the pulverization, the particle size and the magnet performance after the pulverization were not greatly affected in the opposed type and the colliding type of the comparative examples. This means that the impact force at the time of pulverization is very strong, and the particle diameter after pulverization actually determines the magnet performance. On the other hand, in the non-opposed and non-colliding type of the present invention, the pulverized particle size and the magnet performance are strongly affected by the average oxygen amount during pulverization, and the magnet performance is improved when the average oxygen amount is 800ppm or less. This is a novel insight of the present invention.

Further, even in the apparatus of the present invention, when the oxygen content is 1600ppm, the effect of promoting the pulverizability by the surface oxidation of the powder is reduced.

Further, it was confirmed that oxidation due to an increase in the average oxygen content in the magnet leads to a decrease in magnet performance, and no good effect was obtained.

Example 5

In this embodiment, the comminution/surface modification device is of the 400 type, i.e. the cylindrical comminution/surface modification chamber 2 has a diameter of about 400mm, 12 side nozzles 6 are provided, and 12 side nozzles 6 are arranged in a plane parallel to the ground and symmetrically around a center point, which may be understood as the center of a circle, which is common to the outlets of the 12 side nozzles 6, which may be located on the central axis of the cylindrical comminution/surface modification chamber 2. The line connecting the outlet of each side nozzle 6 and the center point forms an included angle with the flow direction of the air flow sprayed by the side nozzle 6, namely, the air flow sprayed by the side nozzle 6 does not pass through the center of the circle where the outlet of the side nozzle 6 is located. The lower part of the inner side wall of the crushing/surface modification chamber 2 is also provided with 30 first convex parts 7 which are circumferentially arranged and are inwards convex, and the first convex parts 7 are square columns, have the side length of 20mm and the height of 250mm and are made of SUS316 stainless steel. The first projection 7 corresponds to the position of the side nozzle 6.

The raw materials for preparing the sintered nd-fe-b SC cast sheet of the embodiment: nd-12.7 at%, B-4.8 at% -6.0 at% (4.8 at%, 5.0 at%, 5.2 at%, 5.4 at%, 5.6 at%, 5.8 at%, 6.0 at%), Ga-0.15 at%, Al-0.5 at%, Cu-0.1 at%, Co-2.5 at%, Mn-0.05 at%, Cr-0.03 at%, Si-0.02 at%, and the balance of Fe and unavoidable impurities.

600kg of raw materials are smelted by adopting a medium-frequency induction rapid hardening furnace to obtain an SC cast piece, and the average thickness of the SC cast piece is 0.3 mm. The SC cast piece was put into a hydrogen pulverizer, treated in a hydrogen atmosphere of 0.09MPa to crush the SC cast piece, and then subjected to dehydrogenation treatment at 600 ℃ for 4 hours. The hydrogen-pulverized raw material was roughly divided into 3 equal parts, and 1 part was charged into the non-opposing/non-colliding 400-type apparatus (12 side nozzles) of this example. The remaining two portions were fed into a counter type pulverizer (400 type, 6 nozzles) as shown in FIGS. 1 to 3 and an impact type pulverizer (400 type, 3 nozzles) as shown in FIG. 4. The nitrogen pressure of each nozzle was 4kg/cm²The nitrogen gas contains an oxygen amount of 200ppm or less on average, and is pulverized to obtain fine powder.

The powders having different oxygen contents obtained by the respective pulverizing apparatuses were compacted in an oriented magnetic field of 1.8T (Tesla) at 0.35ton/cm²Is pressed into a square of 30mm by 30 mm. Then, each square block is sintered for 3 hours at 980-1100 ℃ in a vacuum sintering furnace, 9Heat treatment at 00 ℃ for 1 hour, 600 ℃ for 1 hour, and 420 ℃ for 3 hours. Then, each magnet was processed into a 10mm cube, and the magnet performance was evaluated by a BH magnet performance apparatus, and the performance of the powder obtained by each pulverizing method is shown in table 5 by comparison.

TABLE 5 comparison of the properties of the powders obtained in example 5 by the respective comminution methods

The function is as follows: the pulverizing effect of the pulverizing apparatus according to the present invention has a great dependence on the B content in the magnet alloy. This is considered to be because the magnet alloy is easily pulverized due to the B content, and has subtle dependence. Specifically, the amount of precipitation and the state of precipitation of the 2-17 phase, the 6-13-1 phase and the Nd-rich amorphous phase other than the 2-14-1 type main phase were changed by the change in the B content in the SC alloy, and the pulverizability was greatly affected. It is considered that the B content affects the surface state and lattice defects of the powder.

The examples of the present invention are not limited to the average particle diameter, the magnet performance. This is a comparison between the non-front collision and non-collision type pulverization methods, and is a reduction in impact resistance to powder pulverization and a reduction in lattice defects occurring on the surface of powder particles, and ideal powder particles can improve the remanence and squareness of a magnet according to the nucleation field theory of an Nd-Fe-B system sintered magnet. In addition, it can be analyzed and understood that the magnet of the present invention having a large average grain size has a larger Br value than the principle of magnetic moment orientation by a magnetic field.

On the other hand, in the opposite/head-on type pulverization method, the pulverization property is not affected by the B component due to the strong impact force. The powder is affected by deterioration of properties due to lattice defects, and magnetic properties are reduced. In addition, since the powder is fine and sharp in shape, the magnetic field orientation is not sufficient, and the magnetic properties are further degraded.

Example 6

In this embodiment, the comminution/surface modification device is of the 350 type, i.e. the diameter of the cylindrical comminution/surface modification chamber 2 is approximately 350mm, 8 side nozzles 6 are provided, and the 8 side nozzles 6 are located on a plane parallel to the ground and are arranged symmetrically around a central point, which may be understood as the center of a circle on which the outlets of the 8 side nozzles 6 are located together, which may be located on the central axis of the cylindrical comminution/surface modification chamber 2. The line connecting the outlet of each side nozzle 6 and the center point forms an included angle with the flow direction of the air flow sprayed by the side nozzle 6, namely, the air flow sprayed by the side nozzle 6 does not pass through the center of the circle where the outlet of the side nozzle 6 is located. The lower part of the inner side wall of the crushing/surface modification chamber 2 is also provided with 36 first convex parts 7 which are arranged circumferentially and are convex inwards, and the first convex parts 7 are semi-cylindrical, have the radius of 22mm and the height of 250mm and are made of SUS316 stainless steel. The first projection 7 corresponds to the position of the side nozzle 6.

The raw materials for preparing the sintered nd-fe-b SC cast sheet of the embodiment: nd-12.5 at%, Dy-0.2 at%, Tb-0.15 at%, B-5.8 at%, Ga-0.02 at% -1.2 at% (0.02 at%, 0.05 at%, 0.1 at%, 0.2 at%, 0.4 at%, 0.6 at%, 0.8 at%, 1.0 at%, 1.2 at%), Al-0.3 at%, Cu-0.3 at%, Co-1.5 at%, Mn-0.03 at%, Cr-0.02 at%, Si-0.03 at%, and the balance of Fe and unavoidable impurities.

600kg of raw materials are smelted by adopting a medium-frequency induction rapid hardening furnace to obtain an SC cast piece, and the average thickness of the SC cast piece is 0.18 mm. The SC cast piece was charged into a hydrogen pulverizer, treated in a hydrogen atmosphere of 0.098MPa to crush the SC cast piece, and then subjected to dehydrogenation treatment at 500 ℃ for 4 hours. The hydrogen-pulverized raw material was roughly divided into 3 equal parts, and 1 was charged into the non-opposing/non-colliding 350-type apparatus (8 side nozzles) of this example. The remaining two were introduced into a counter type pulverizer (350 type, 4 nozzles) as shown in FIGS. 1 to 3 and an impact type pulverizer (350 type, 2 nozzles) as shown in FIG. 4. The nitrogen pressure of each nozzle was 5kg/cm²The nitrogen gas contains oxygen in an amount of 150ppm or less on average, and is pulverized to obtain fine powder.

The pulverized powder of each pulverizing apparatus was pressed at an orientation strength of 2.4T (Tesla) of 0.45ton/cm²The pressure of (3) was applied to a square of 30mm by 30 mm. Thereafter, each square was sintered at 980 ℃ to 1080 ℃ in vacuum for 3 hours, heat-treated at 850 ℃ for 1 hour, heat-treated at 580 ℃ for 1 hour, and heat-treated at 450 ℃ for 3 hours. Then, each magnet was processed into a 10mm cube, and the magnet performance was evaluated by a BH magnet performance apparatus, and the performance of the powder obtained by each pulverizing method is shown in table 6 by comparison.

TABLE 6 comparison of the properties of the powders obtained in example 6 by the respective comminution methods

The function is as follows: the pulverizing effect of the pulverizing apparatus of the present invention has a great dependence on the Ga content in the magnet alloy. This is considered to be because the magnet alloy contains a small amount of Ga, is easily pulverized, and has subtle dependence. Specifically, depending on the change in the Ga content in the SC alloy, Ga preferentially precipitates in the grain boundaries, and actively precipitates in the B-rich phase, 2-17 phase, 6-13-1 phase, and Nd-rich amorphous phase in addition to the 2-14-1 type main phase. The precipitation state of grain boundaries, which are starting points of pulverization, changes, and the pulverization performance is greatly affected by the Ga content.

The examples of the present invention are not limited to the average particle diameter, the magnet performance. This is a comparison of the non-front collision and non-collision type pulverization methods, and is a reduction in impact force upon powder pulverization and a reduction in lattice defects occurring on the surface of powder particles, and ideal powder particles can improve the remanence and squareness of a magnet according to the nucleation field theory of an Nd-Fe-B system sintered magnet. In addition, it can be analyzed and understood that the magnet of the present invention having a large average grain size has a larger Br value than the principle of magnetic moment orientation by a magnetic field.

On the other hand, in the opposite/head-on type pulverizing method, the pulverizing property is not affected by Ga component due to strong impact force. The powder is affected by deterioration in properties caused by lattice defects, and the magnet properties are reduced. In addition, since the powder is fine and sharp in shape, the magnetic field orientation is not sufficient, and the magnetic properties are further degraded.

Example 7

As shown in fig. 16 to 18, the crushing apparatus of the present invention can be used in the final crushing step of the 2 nd and 3 rd stage crushing in the prior art. In the former step, coarse pulverization is carried out by a conventional opposed type pulverizer, and final pulverization is carried out by the pulverizer of the present invention. The pulverizing apparatus of the present invention has the ability to produce a powder with few lattice defects and a high-performance powder with spheroidization, and therefore, when used in the final pulverizing stage, the best magnet performance can be obtained.

Example 8

As shown in fig. 19 to 20, the crushing apparatus of the present invention can be used in the final crushing step of the conventional 2 nd and 3 rd crushing steps. In the previous stage, coarse pulverization is carried out by a non-opposed type pulverizing apparatus (different from the opposed type pulverizing apparatus in the prior art in that the air flows of the nozzles 6' ″ are staggered and do not meet at a single point), and a combination of final pulverization by the apparatus of the present invention is also possible. The pulverizing apparatus of the present invention has a strong ability to produce a powder with few lattice defects and a high-performance powder with spheroidization, and therefore, when used in the final pulverizing stage, the best magnet performance can be obtained. The number of classifiers can be 1 or more in the system of the present apparatus. In the examples of FIGS. 19 to 20, since large particles are removed by the classifier in the upper part of the pulverizing chamber of the previous stage, even if there is no classifier in the upper part of the pulverizing/surface modifying chamber of the present invention of the 2 nd stage, it is possible to obtain a high-performance magnet having higher pulverizing performance than the conventional one. Therefore, by adding a few pulverizing/surface modifying apparatuses according to the present invention to existing manufacturing facilities, high performance can be achieved, and the apparatus has a high industrial application value.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.

Claims

1. The utility model provides a crushing/surface modification's of sintered neodymium iron boron SC casts piece device which characterized in that: the device comprises a crushing/surface modification chamber, wherein the crushing/surface modification chamber is provided with a plurality of side nozzles which are circumferentially arranged at intervals, and the side nozzles are arranged in a non-opposite manner; the inner side wall of the crushing/surface modification chamber is also provided with a plurality of first convex parts which are circumferentially arranged.

2. The apparatus of claim 1, wherein: the side nozzles are arranged around a central point; and a connecting line formed by the outlet of any one side nozzle and the central point forms an included angle with the flowing direction of the airflow sprayed by the side nozzle.

3. The apparatus of claim 1, wherein: the bottom of the crushing/surface modification chamber is provided with a bump.

4. The apparatus of claim 3, wherein: and a plurality of second convex parts which are circumferentially arranged are also arranged on the convex block.

5. The apparatus of claim 1, wherein: the first convex part is in the shape of a semi-cylinder, a triangular prism or a quadrangular prism.

6. The apparatus of claim 3, wherein: the shape of the convex block is hemispherical, semi-ellipsoidal, semi-egg-shaped, square column, trapezoid truncated cone, cylindrical or cone truncated cone.

7. The apparatus of claim 4, wherein: the second convex part is in the shape of a semi-cylinder, a triangular prism or a quadrangular prism.

8. The apparatus of claim 2, wherein: the side nozzles are positioned on the same plane, the outlets of the side nozzles are in a common circle, and the center point is coincident with the circle center of the circle.

9. The apparatus of claim 2, wherein: the heights of the side nozzles on the crushing/surface modification chamber are different, the projections of the outlets of the side nozzles on the horizontal plane are concentric, and the projection of the central point on the horizontal plane is coincident with the circle center of the circle.

10. The apparatus of claim 1, wherein: the milling/surface modification chamber is cylindrical.

11. The apparatus of claim 1, wherein: the device also comprises a powder feeder, a rotary classifier, an airflow classifier and a product powder recovery container; the powder feeder is communicated with the crushing/surface modification chamber; the rotary classifier is arranged in the crushing/surface modification chamber and is positioned above the side nozzle and the first convex part; the airflow classifier is connected with the rotary classifier; the product powder recovery container is connected with the airflow classifier.

12. The apparatus of claim 1, wherein: the side nozzle is a diffusion nozzle.

13. The apparatus of claim 1, wherein: the gas flow is inert gas with the oxygen content of 2 ppm-800 ppm.

14. A method for crushing/surface modifying sintered nd-fe-b SC cast sheet using the apparatus of any one of claims 1 to 12, characterized by: crushing the sintered NdFeB SC cast sheet into coarse powder by hydrogen, and further crushing the coarse powder in the crushing/surface modification chamber under the drive of airflow sprayed by the side nozzle to obtain micro powder with the average particle size of 1-10 microns; the gas flow is inert gas with the oxygen content of 2 ppm-800 ppm.

15. The method of claim 14, wherein: the raw material of the sintered NdFeB SC cast sheet contains 5.0at percent to 5.8at percent of B.

16. The method of claim 14, wherein: the raw material of the sintered NdFeB SC cast sheet contains Ga of 0.05at percent to 1.0at percent.