CN114891953B - Method for improving sintering NdFeB material yield - Google Patents

Method for improving sintering NdFeB material yield Download PDF

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Publication number
CN114891953B
CN114891953B CN202210327793.2A CN202210327793A CN114891953B CN 114891953 B CN114891953 B CN 114891953B CN 202210327793 A CN202210327793 A CN 202210327793A CN 114891953 B CN114891953 B CN 114891953B
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crucible
alloy liquid
metal
slag
active metal
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CN114891953A (en
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周保平
马春茹
范立忠
吴亚平
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Baotou INST Magnetic New Material Co Ltd
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Baotou INST Magnetic New Material Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C21C7/0645—Agents used for dephosphorising or desulfurising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The utility model provides a method for improving the yield of sintered NdFeB, which relates to the field of sintered NdFeB magnet preparation and solves the problems of low smelting yield and high oxygen and sulfur content of cast sheet alloy in the prior art, and the method comprises the steps of sequentially carrying out raw material treatment, weighing and loading into a crucible in a smelting furnace, melting raw materials in the crucible under a vacuum state to obtain alloy liquid, adding metal fluoride into the alloy liquid in the crucible, and adding active metal onto slag on the surface layer of the alloy liquid in the crucible; immediately closing the crucible opening after the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible is completed so as to ensure that the gasified active metal reduces the slag in the crucible; the reducibility of the metal element in the active metal and the metal fluoride is stronger than that of the neodymium element. The utility model can improve the smelting yield and reduce the oxygen and sulfur content of the cast sheet alloy.

Description

Method for improving sintering NdFeB material yield
Technical Field
The utility model relates to the field of sintered NdFeB magnet preparation, in particular to a method for improving the yield of sintered NdFeB magnets.
Background
Sintered NdFeB is the permanent magnet material with the highest magnetic energy product at present, ndFeB is developed from Zuo-Pian of Japanese Sumitomo special metal and universal automobile company in USA in 1983, is a third-generation rare earth permanent magnet material, and has been widely applied to the fields of new energy automobiles, energy-saving household appliances, wind power generation, consumer electronics and the like after development for nearly 40 years. China's rare earth reserve accounts for 23% of the world's weight, supplies 70% of the world's market, and China has become the biggest production place of neodymium iron boron worldwide. About 30% of the neodymium iron boron components are rare earth elements, wherein the neodymium iron boron components mainly contain praseodymium, neodymium, dysprosium, terbium, holmium and other rare earth elements, the rare earth elements have lower reserves than other transition metals, the domestic rare earth reserves are smaller and smaller along with the annual exploitation, the production flow of the neodymium iron boron is more complex, and each process has different ratio loss, so the improvement of the yield of the neodymium iron boron is the direction of the efforts in the industry all the time.
The existing technology for preparing the NdFeB blank mainly comprises the following steps: (1) batching, (2) smelting, (3) crushing, (4) air-flow grinding, (5) compression molding, (6) isostatic pressing, (7) sintering, (8) heat treatment, (9) processing and (10) surface protection. The yield of the smelting process is only 95% -98%, wherein 2% -5% of the yield is mainly slag. The utilization rate of the material is greatly reduced, and the control of the formula of the neodymium iron boron material is not facilitated. As the price of the rare earth is continuously increased, the yield of the smelting process is improved, the cost is reduced, and the method is an effective method for saving the rare earth consumption. Secondly, as the requirements of sintered NdFeB on performance are higher and higher, the requirements of the sintered NdFeB magnet on low oxygen content and low sulfur content are also higher and higher, and the low oxygen content and sulfur content are an important basis for preparing the high-performance sintered NdFeB magnet.
The conventional preparation method mainly improves the yield of the smelting process and reduces the oxygen content and the sulfur content of the cast sheet alloy by surface treatment of raw materials and improvement of the leakage rate of a smelting furnace. However, the conventional method is limited, and the problems of low yield, high oxygen content and high sulfur content cannot be fundamentally solved.
Disclosure of Invention
The utility model aims to design a method for improving the yield of sintered NdFeB, which can fundamentally solve the problems of low smelting yield, high oxygen content and high sulfur content, can improve the smelting yield and reduce the oxygen and sulfur content of cast sheet alloy.
The utility model is realized by the following technical scheme:
a method for improving the sintering NdFeB material yield adopts a vacuum smelting furnace, and comprises the steps of sequentially carrying out treatment and weighing of raw materials, loading the raw materials into a crucible in the smelting furnace, melting the raw materials in the crucible in a vacuum state to obtain alloy liquid, adding metal fluoride into the alloy liquid in the crucible after the alloy liquid is obtained and before the casting step, and adding active metal onto slag on the surface layer of the alloy liquid in the crucible; immediately closing the crucible opening after the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible is completed so as to ensure that the gasified active metal reduces the slag in the crucible; the reducibility of the metal element in the active metal and the metal fluoride is stronger than that of the neodymium element.
Further to better realize the utility model: after the step of adding the metal fluoride into the alloy liquid in the crucible is completed, adding the active metal into the slag on the surface layer of the alloy liquid in the crucible after the slag is not floated on the alloy liquid.
Further to better realize the utility model: after the crucible opening is closed, the crucible opening is unsealed after waiting for 3-20 minutes, and then the casting step is carried out.
Further to better realize the utility model: in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, the action of adding the metal fluoride to the alloy liquid in the crucible, the action of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, and the actions of closing and unsealing the crucible opening are performed using a special feeding device; the special feeding device comprises first telescopic equipment, a crucible cover plate, a screw conveyor and second telescopic equipment; one end of the crucible cover plate is hinged to the position of the crucible opening of the crucible, and two ends of the first telescopic equipment are respectively hinged to the crucible and the crucible cover plate, and the opening and closing of the crucible cover plate are controlled through telescopic adjustment to realize the actions of closing and unsealing the crucible opening; the screw conveyor is integrally arranged in the smelting furnace and positioned above the crucible side, the screw conveyor is movably connected to the smelting furnace, two ends of the second telescopic equipment are respectively connected with the smelting furnace and the screw conveyor, and the second telescopic equipment can control a discharge hole of the screw conveyor to move to the position above the crucible through telescopic adjustment; the metal fluoride and the active metal are integrally filled in a material conveying channel of the screw conveyor in a layered manner, and the metal fluoride is integrally filled closer to a discharge port of the material conveying channel than the active metal; the first telescoping device, the second telescoping device, and the screw conveyor are connected with a console to have functions that are remotely or automatically controlled to perform related actions.
Further: the screw conveyor comprises driving equipment, a hopper and screw conveying blades, wherein the screw conveying blades are installed in the hopper, the extending ends of the screw conveying blades are connected with the driving equipment, and one end of the second telescopic equipment is connected with the hopper.
Further to better realize the utility model: the discharge gate downward sloping setting of hopper, the one end of second telescopic equipment articulates the hopper is used for can control through flexible regulation the discharge gate of hopper removes to the inclination of hopper is adjusted to the top position of crucible simultaneously, so that in the step of adding metal fluoride into the alloy liquid in the crucible and the step of adding active metal onto the slag on the alloy liquid top layer in the crucible can control the charge angle of adding metal fluoride with active metal.
Further to better realize the utility model: the driving device is provided as a servo motor so that the feeding rates of the metal fluoride and the active metal can be controlled in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible.
Further to better realize the utility model: the screw conveyor and the second telescopic device are detachably connected to the smelting furnace.
Further: after the step of processing and weighing the raw materials and then loading them into the crucible inside the melting furnace, and before the step of melting the raw materials in the crucible under vacuum to obtain an alloy liquid, a preceding step of installing the screw conveyor and the second telescopic device inside the melting furnace is also included.
Further: the metal elements in the active metal and the metal fluoride are potassium or calcium or sodium or magnesium.
The utility model has the following advantages and beneficial effects:
in the process of preparing cast sheet alloy by smelting process, after raw materials in a crucible in a smelting furnace are melted, metal fluoride is added into alloy liquid to reduce the melting point of refractory substances, promote slag flow, enable slag and metal to be well separated, desulfurization and dephosphorization can be carried out in the smelting process, the floating of slag is promoted, the proportion of oxidized impurities in the cast sheet alloy is reduced, the processing property and mechanical properties of a magnet are improved, such as three-point bending resistance, and the like. Therefore, the yield of the neodymium iron boron alloy can be obviously improved, and the oxygen content and the sulfur content of the neodymium iron boron alloy sheet can be obviously reduced by adopting the method.
Drawings
In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic view of an arrangement of a specialized feeding apparatus in combination with a crucible;
marked in the figure as:
1. a crucible; 2. a heating coil; 3. alloy liquid; 4. a first telescopic device; 5. a crucible cover plate; 6. a driving device; 7. a hopper; 8. spiral conveying blades; 9. a second telescopic device; 10. a metal fluoride; 11. an active metal.
Detailed Description
In order to make the objects, technical solutions and advantages of the present utility model more apparent, the technical solutions of the present utility model will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the utility model. All other embodiments, based on the examples herein, which are within the scope of the utility model as defined by the claims, will be within the scope of the utility model as defined by the claims.
In the description of the present utility model, it is to be noted that, unless otherwise indicated, the meaning of "plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," and the like are used as an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the utility model and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the utility model. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present utility model, it should also be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present utility model can be understood as appropriate by those of ordinary skill in the art.
Example 1:
the method for improving the yield of sintered NdFeB can fundamentally solve the problems of low smelting yield, high oxygen content and high sulfur content, can improve the smelting yield and reduce the oxygen and sulfur contents of cast sheet alloy:
the method adopts a vacuum smelting furnace, and comprises the steps of sequentially carrying out raw material treatment, weighing and loading the raw materials into a crucible in the smelting furnace, melting the raw materials in the crucible in a vacuum state to obtain alloy liquid, and adding metal fluoride into the alloy liquid in the crucible after the alloy liquid is obtained and before the casting step, and adding active metal onto slag on the surface layer of the alloy liquid in the crucible; immediately closing the crucible opening after the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible is completed so as to ensure that the gasified active metal reduces the slag in the crucible; the metal element in the active metal and the metal fluoride has stronger reducibility than that of neodymium element, and the metal element can be potassium or calcium or sodium or magnesium.
In this embodiment, in order to make it possible to more conveniently add the metal fluoride and the active metal better, the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible are performed by using a medium specific feeding device, the actions of adding the metal fluoride to the alloy liquid in the crucible, the actions of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, and the actions of closing and unsealing the opening of the crucible.
As shown in fig. 1, this special charging device comprises a first telescopic device 4, a crucible cover 5, a screw conveyor and a second telescopic device 9.
The first telescopic device 4 and the second telescopic device 9 can be hydraulic cylinders.
The screw conveyer is wholly arranged in the smelting furnace and is positioned at the position above the side of the crucible 1, the screw conveyer comprises a driving device 6, a hopper 7 and screw conveying blades 8, the screw conveying blades 8 are rotatably arranged in the hopper 7, the extending ends of the screw conveying blades 8 are connected with the driving device 6, two ends of a second telescopic device 9 are respectively connected with the hopper 7 and the smelting furnace, the hopper 7 of the screw conveyer can be connected with the smelting furnace through a hanging rod or a sliding rail or other feasible connecting structures so as to enable the hopper 7 to move towards or away from the crucible opening in the smelting furnace, and the second telescopic device 9 can control the discharge opening of the screw conveyer to move to the position above the crucible 1 through telescopic adjustment. The metal fluoride 10 and the active metal 11 are integrally packed in layers in a material conveying channel of the screw conveyor, and the metal fluoride 10 is integrally packed closer to a material outlet of the material conveying channel than the active metal 11, namely the active metal 11 is integrally located on the upper layer of the metal fluoride 10.
In order to control the feed rates of the metal fluoride 10 and the active metal 11 in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, the driving apparatus 6 is preferably provided as a servo motor.
In order to control the feeding angle of the metal fluoride 10 and the active metal 11 in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, the hopper 7 is preferably set in a posture in which the discharge port is inclined downward, while one end of the second telescopic device 9 is hinged to the melting furnace and the other end is hinged to the hopper 7, the second telescopic device 9 adjusts the inclination angle of the hopper 7 so that the discharge port of the hopper 7 can be controlled to move to the upper position of the crucible 1 by telescopic adjustment.
The crucible cover plate 5 is made of metal molybdenum or other high-temperature resistant materials, one end of the crucible cover plate 5 is hinged to the left side of a crucible opening of the crucible 1, two ends of the first telescopic device 4 are respectively hinged to the left side of the outer wall of the crucible 1 and the left edge of the crucible cover plate 5, and the first telescopic device 4 controls the opening and closing of the crucible cover plate 5 through telescopic adjustment to realize the actions of closing and unsealing the crucible opening.
The first telescopic device 4, the second telescopic device 9 and the screw conveyor are typically connected to a console to have functions controlled remotely or automatically to perform the relevant actions.
For the purpose of detachably connecting the screw conveyor and the second telescopic device 9 to the smelting furnace. The purpose of the screw conveyor being removable from the furnace is to enable the screw conveyor to be selectively used, and to be removed from the furnace when not required so as not to interfere with other functions of the furnace.
In this embodiment, when the vacuum melting furnace is an existing apparatus without such a special charging device, the special charging device needs to be designed and manufactured in advance, and specifically includes the following steps:
step one, designing a special feeding device.
Step two, raw material treatment and weighing, wherein the raw materials are treated and weighed according to the formula and the technological requirements in a conventional manner, the oxidation layer on the surface of the raw materials is removed by adopting equipment such as a shot blasting machine, a reinforcing steel bar machine and the like in the raw material treatment process, and the raw material formula after weighing treatment is prepared according to the following weight percentages: nd+Pr (30%), dy (0.3%), fe (67.3%), co (0.5%), B (0.95%), ga (0.2%), cu (0.2%), AL (0.3%), zr (0.25%).
And step three, loading the treated and weighed raw materials into a crucible of a 600kg vacuum induction casting furnace (smelting furnace).
And step four, installing a screw conveyer and a second telescopic device of the special feeding device into the 600kg type vacuum induction casting furnace.
Covering a furnace cover of the 600kg vacuum induction casting furnace, installing a crucible cover plate 5 and a first telescopic device 4 on the crucible, and checking the actions and sealing effects of the crucible cover plate 5 and the first telescopic device 4, wherein the crucible cover plate 5 and the first telescopic device4 are located above the heating coil 2. Calcium fluoride (CaF) 2 ) And calcium metal (Ca) are added to the screw conveyor in several steps to make calcium fluoride (CaF) 2 ) In the feed channel at a position below the calcium metal (Ca), wherein calcium fluoride (CaF 2 ) The amount of the added calcium metal (Ca) was 0.2kg and the amount of the added calcium metal (Ca) was 1kg.
And step six, closing the furnace door to start vacuumizing after the furnace is completely filled, and starting to heat the furnace after the vacuum degree reaches below 10pa and the heating power is 150kw so as to dry the water vapor adsorbed on the raw materials in the crucible.
And step seven, after the vacuum degree is lower than 3pa, closing the heating and stopping the baking furnace, and starting to charge argon or helium gas, so that the internal pressure reaches 30kpa after charging.
And step eight, after filling inert gas, heating the heating coil 2 to melt raw materials, wherein in the process, the power is gradually increased to 500kw, alloy liquid is obtained after the raw materials are completely melted, the power is reduced to 300kw and is kept still for 5-10min (keeping the power to run for 5-10 min), and all slag floats to the surface layer of the alloy liquid.
Step nine, after the rest is finished, starting the second telescopic device 9 to push the discharge hole of the hopper 7 to the crucible hole and align with the alloy liquid level, and then starting the driving device 6 to drive the spiral conveying blade 8 to drive the lower layer of calcium fluoride (CaF) 2 ) Slowly scattering the molten alloy into the molten alloy at one time, then withdrawing the hopper 7 through the second telescopic device 9, and standing for 5-10min until no slag floats on the molten alloy.
Step ten, after the second telescopic device 9 is started again to push the discharge hole of the hopper 7 to the crucible opening and align with the alloy liquid level, the driving device 6 is started to drive the spiral conveying blade 8 to scatter metal calcium (Ca) on the slag on the surface of the alloy liquid, then the hopper 7 is immediately and rapidly retracted through the second telescopic device 9, the first telescopic device 4 is started to drive the crucible cover plate 5 to seal the crucible opening so as to ensure that gasified active metal reduces the slag in the crucible, and after the crucible is stationary for 3-20min, the first telescopic device 4 is started again to open the crucible cover plate 5 to unseal the crucible opening.
And step eleven, starting casting, wherein the casting process is the same as the conventional mode, and cooling the cast sheet alloy after casting for 2 hours and discharging.
And twelve, cooling, wherein the step is the same as the conventional operation mode, namely loading the cast sheet alloy into a hydrogen crushing furnace, vacuumizing until the vacuum degree is below 5pa, charging hydrogen to start hydrogen absorption, controlling the hydrogen absorption pressure to be 150kPa, heating to 590+/-5 ℃ after the hydrogen absorption is saturated for dehydrogenation, charging argon or helium to replace hydrogen after the dehydrogenation is finished, starting a fan for cooling after the argon or helium is charged to 75-80kPa, and discharging to prepare coarse powder.
And thirteenth, adding 400 airflow grinding powder into coarse powder, setting the rotating speed of a grinding sorting wheel to 3000 revolutions, and filling the ground fine powder into a charging bucket for nitrogen protection.
Fourteen, weighing 200kg of fine powder in a charging bucket, performing orientation pressing by adopting a 350-type press, setting the magnetic field strength to be 2T, setting the pressing pressure to be 4Mpa, and obtaining a pressed product with the size of 50mm 40mm 30mm to obtain the density of 4.0g/cm 3 Is formed into a green compact.
Fifteen, placing the pressed compact into a vacuum sintering furnace, sintering at 1075 ℃ for 5 hours, and discharging after tempering. And (5) after discharging, checking the appearance qualification rate, performance and microscopic metallographic phase of the product.
The method comprises melting raw materials in a crucible in a smelting furnace, and adopting a special feeding device to feed calcium fluoride (CaF) 2 ) Adding into alloy liquid to reduce melting point of refractory material, promote slag flow, separate slag from metal, desulphurize, dephosphorize, promote slag floating, reduce oxidation impurity proportion in cast sheet alloy, avoid slag (rare earth oxide) inclusion in alloy, improve magnetic processing and mechanical properties such as three-point bending resistance, and add calcium fluoride (CaF 2 ) After the slag is promoted to float upwards, adding metal calcium (Ca) to the slag on the surface layer of the alloy liquid, rapidly covering and sealing the crucible mouth, and starting to gasify the metal calcium (Ca) after encountering high temperature, wherein the gasified metal calcium (Ca) reacts with the slag on the surface layer of the alloy liquid, and the activity of the metal calcium (Ca) is far higher than that of the neodymium iron boron material, so that the metal calcium (Ca) can be deprived of the slag after being gasifiedOxygen and sulfur are reduced to obtain rare earth metal, and the formed metal oxide floats to the surface of the alloy liquid in the form of slag, so that the aim of improving the smelting yield is fulfilled, and the yield of the NdFeB alloy can be obviously improved. And due to metallic calcium (Ca) and calcium fluoride (CaF) 2 ) The method has the effect of reducing the oxygen content and the sulfur content in the alloy liquid, can obviously reduce the oxygen content and the sulfur content of the neodymium-iron-boron alloy sheet, provides a good basis for preparing a high-performance magnet, and obviously improves the coercive force of the magnet. Besides participating in the reduction reaction, the metal calcium (Ca) can also form an alloy with other metal elements, and the magnetic body prepared by adding the alloy of the calcium element has improved mechanical property toughness and bending strength, and solves the problems of poor processing property, weak bending resistance and the like of the magnetic body to a certain extent. The impurity removal effect of the calcium fluoride also obviously improves the yield of finished products. The method is suitable for the production of all neodymium iron boron blanks, has obvious economy, accords with the development trend of industry, has relatively simple operation mode, and is also suitable for other fields such as rare earth smelting.
Example 2:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, calcium fluoride (CaF 2 ) The amount of added calcium metal (Ca) was 0.5kg and the amount of added calcium metal (Ca) was 1kg.
Example 3:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, calcium fluoride (CaF 2 ) The amount of added calcium metal (Ca) was 0.2kg, and the amount of added calcium metal (Ca) was 2kg.
Example 4:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, calcium fluoride (CaF 2 ) The amount of added calcium metal (Ca) was 0.2kg and the amount of added calcium metal (Ca) was 4kg.
Example 5:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, calcium fluoride (CaF 2 ) The amount of added calcium metal (Ca) was 0.2kg and the amount of added calcium metal (Ca) was 8kg.
Example 6:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, calcium fluoride (CaF 2 ) The amount of added (C) was 0.2kg, and no calcium metal (Ca) was added in this step.
Example 7:
this example was identical to example 1 in steps one through four and steps six through fifteen using the same batch of starting materials, the same recipe and the same specialized feeding set.
In the fifth step of this embodiment, however, no calcium fluoride (CaF 2 ) The amount of calcium metal (Ca) added was 4kg.
In addition, the utility model also provides two comparative examples:
comparative example 1:
the comparative example uses the same batch of raw materials as in example 1, the same formulation, no special feeding device, and no addition of calcium fluoride (CaF) to the alloy liquid by conventional process 2 ) And calcium (Ca) or other active metals or metal fluorides, all of which are the same as the essential steps of example 1.
Comparative example 2:
this comparative example was identical to example 1 in steps two through three using the same batch of starting materials, the same recipe, and no special feeding apparatus.
In the fifth step of this comparative example, however, calcium fluoride (CaF 2 ) The amount of added calcium metal (Ca) was 0.2kg and the amount of added calcium metal (Ca) was 4kg. In the comparative example, the calcium fluoride (CaF) was directly fed to the reactor without using a special feeding device in step nine 2 ) And calcium metal (Ca) are added to the alloy liquid together at one time.
The remaining necessary steps were the same as in example 1.
Specifically, the following tables can be obtained by the products of comparative examples 1 to 7 and comparative examples 1 and 2:
table 1: cast sheet alloy yield controls of examples 1-7 and comparative examples 1, 2
Table 2: cast sheet alloy compositions of examples 1 to 7 and comparative examples 1 and 2
Table 3: examples 1-7 and comparative examples 1, 2 were compared with the cast sheet alloys of oxygen content and sulfur content
Table 4: magnet performance controls of examples 1-7 and comparative examples 1, 2
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Table 5: examples 1-7 and comparative examples 1, 2 were finished three-point bending control
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Table 6: comparative examples 1-7 and comparative examples 1, 2 were compared with the finished trachoma ratio
As can be seen from the comparison of the parameters of examples 1-7 and comparative examples 1 and 2, the sintered NdFeB magnet obtained by the method of the present utility model has the following advantages:
(1) As can be seen from comparison of Table 1, with increasing weight of calcium metal (Ca), the yield of cast sheet alloy was gradually increased by up to 1.26 percentage points, corresponding to an increase of 7.56kg per furnace product. This data fully demonstrates the feasibility and effect of this approach, which is a significant savings for mass produced NdFeB.
(2) As is clear from Table 2, the method does not significantly increase the residual amount of calcium metal (Ca) in the alloy, and the calcium metal (Ca) is more involved in the reduction of other metals.
(3) As can be seen from a comparison of Table 3, calcium fluoride (CaF 2 ) And calcium metal (Ca) can greatly reduce the oxygen content and sulfur content of the cast sheet alloy. The oxygen content can be reduced from 400ppm to about 100ppm, and the sulfur content can be reduced from about 20ppm to below 10 ppm.
(4) As can be seen from a comparison of Table 4, by the addition of the method, a suitable amount of calcium fluoride (CaF 2 ) And the metal calcium (Ca) can obviously improve the intrinsic coercivity of the magnet and can improve the intrinsic coercivity by about 1000 Oe.
(5) As can be seen from comparison of Table 5, the calcium fluoride (CaF 2 ) And the addition of the metal calcium (Ca) can obviously improve the maximum three-point bending resistance force of the finished magnet product, and most obviously, the deformation of the three-point bending resistance is obviously increased. Description of calcium fluoride (CaF) 2 ) Oxidized impurity particles in the magnet can be reduced, defects in a finished product are reduced, and on the other hand, the added metal calcium (Ca) remarkably improves the toughness of the NdFeB magnet.
(6) As can be seen from comparison of Table 6, the addition of calcium fluoride (CaF 2 ) The method can obviously reduce oxidized impurities in the magnet, promote the separation of alloy liquid and oxidized impurities, reduce the defect proportion of the finished product and improve the yield of the finished product.
The method has the beneficial effects that:
(1) The special feeding device is additionally arranged on the smelting furnace, does not greatly change the main structure of the smelting furnace, and does not influence the normal and routine operation of vacuum smelting.
(2) Adding calcium fluoride (CaF) 2 ) After that, slag and NdFeB alloy liquid after metal melting can be effectively separated, so that the impurity oxide impurities in the cast sheet alloy are reduced, and the quality is obviously improved.
(3) Adding calcium fluoride (CaF) 2 ) After that, the oxygen content and the sulfur content of the cast sheet alloy can be obviously reduced.
(4) The utility model adopts the method that after metal is melted, slag floats up to the surface layer of the liquid level, then metal calcium (Ca) is added, and after the metal calcium (Ca) forms a gas state, the metal calcium reacts with slag on the surface layer to remove oxygen in neodymium iron boron slag, and rare earth elements such as metal Pr, nd, dy, tb, ce, ho are replaced, thereby achieving the effect of improving the utilization rate of rare earth.
(5) The neodymium-iron-boron alloy sheet contains an oxidized rare earth compound, the oxidized rare earth compound can inhibit the performance improvement of the neodymium-iron-boron magnet, and because calcium (Ca) has high affinity to oxygen and sulfur, oxygen elements in the rare earth oxide can be removed.
(6) By using the method, the proportion of oxidized impurities in the neodymium-iron-boron alloy sheet can be reduced, so that the mechanical properties of the neodymium-iron-boron magnet such as three-point bending resistance and the like are improved, the qualification rate of electroplating can be improved, and the generation of defects such as sand holes and the like in the electroplating process is reduced.
(7) By applying the method, trace calcium element in the neodymium-iron-boron alloy enters the alloy after the metal calcium (Ca) is added, so that the corrosion resistance of the neodymium-iron-boron magnet is improved.
The foregoing is merely illustrative of the present utility model, and the present utility model is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present utility model.

Claims (10)

1. A method for improving the material yield of sintered NdFeB is characterized by comprising the following steps: the method adopts a vacuum smelting furnace, and comprises the steps of sequentially carrying out raw material treatment, weighing and loading the raw materials into a crucible in the smelting furnace, melting the raw materials in the crucible in a vacuum state to obtain alloy liquid, and adding metal fluoride into the alloy liquid in the crucible after the alloy liquid is obtained and before the casting step, and adding active metal onto slag on the surface layer of the alloy liquid in the crucible; immediately closing the crucible opening after the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible is completed so as to ensure that the gasified active metal reduces the slag in the crucible;
the reducibility of the metal element in the active metal and the metal fluoride is stronger than that of the neodymium element.
2. The method for improving the yield of sintered NdFeB according to claim 1, wherein the method comprises the following steps: after the step of adding the metal fluoride into the alloy liquid in the crucible is completed, adding the active metal into the slag on the surface layer of the alloy liquid in the crucible after the slag is not floated on the alloy liquid.
3. The method for improving the yield of sintered NdFeB according to claim 2, wherein the method comprises the following steps: after the crucible opening is closed, the crucible opening is unsealed after waiting for 3-20 minutes, and then the casting step is carried out.
4. A method for increasing the yield of sintered neodymium iron boron according to claim 1, 2 or 3, wherein: in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, the action of adding the metal fluoride to the alloy liquid in the crucible, the action of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible, and the actions of closing and unsealing the crucible opening are performed using a special feeding device;
the special feeding device comprises a first telescopic device (4), a crucible cover plate (5), a screw conveyor and a second telescopic device (9); one end of the crucible cover plate (5) is hinged to the position of a crucible opening of the crucible (1), two ends of the first telescopic equipment (4) are respectively hinged to the crucible (1) and the crucible cover plate (5), and the opening and closing of the crucible cover plate (5) are controlled through telescopic adjustment to realize the actions of closing and unsealing the crucible opening; the screw conveyor is integrally arranged in the smelting furnace and positioned at a position above the side of the crucible (1), the screw conveyor is movably connected to the smelting furnace, two ends of the second telescopic equipment (9) are respectively connected with the smelting furnace and the screw conveyor, and the second telescopic equipment (9) can control a discharge hole of the screw conveyor to move to a position above the crucible (1) through telescopic adjustment; the metal fluoride (10) and the active metal (11) are integrally and hierarchically filled in a material conveying channel of the screw conveyor, and the metal fluoride (10) is integrally filled closer to a discharge hole of the material conveying channel than the active metal (11); the first telescopic device (4), the second telescopic device (9) and the screw conveyor are connected with a console to have functions controlled remotely or automatically to perform the relevant actions.
5. The method for improving the yield of sintered NdFeB according to claim 4, wherein the method comprises the following steps: screw conveyer includes driving device (6), hopper (7) and screw conveying blade (8), screw conveying blade (8) install in hopper (7), the extension end of screw conveying blade (8) is connected driving device (6), the one end of second telescopic device (9) is connected hopper (7).
6. The method for improving the yield of sintered NdFeB according to claim 5, wherein the method comprises the following steps: the discharge gate downward sloping setting of hopper (7), the one end of second telescopic equipment (9) articulates hopper (7) is used for can control through flexible regulation the discharge gate of hopper (7) removes to the inclination of hopper (7) is adjusted in the top position of crucible (1) to can control in the step of adding metal fluoride into the alloy liquid in the crucible and the step of adding active metal onto the slag on the alloy liquid top layer in the crucible, add metal fluoride (10) with the charging angle of active metal (11).
7. The method for improving the yield of sintered NdFeB according to claim 5, wherein the method comprises the following steps: the driving device (6) is provided as a servo motor to control the feed rates of the metal fluoride (10) and the active metal (11) in the step of adding the metal fluoride to the alloy liquid in the crucible and the step of adding the active metal to the slag on the surface layer of the alloy liquid in the crucible.
8. The method for improving the yield of sintered NdFeB according to claim 4, wherein the method comprises the following steps: the screw conveyor and the second telescopic device (9) are detachably connected to the smelting furnace.
9. The method for improving the yield of sintered NdFeB according to claim 8, wherein the method comprises the following steps: after the step of handling and weighing the raw material and then loading it into a crucible inside the melting furnace, and before the step of melting the raw material in the crucible under vacuum to obtain an alloy liquid, there is also included a preceding step of installing the screw conveyor and the second telescopic device (9) inside the melting furnace.
10. The method for improving the yield of sintered NdFeB according to claim 1, wherein the method comprises the following steps: the metal elements in the active metal and the metal fluoride are potassium or calcium or sodium or magnesium.
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2460334A1 (en) * 1979-07-04 1981-01-23 Roechling Burbach Gmbh Stahl Electroslag remelting of steel and alloys for turbine rotors - using alkaline earth metal to deoxidise fluorspar contg. slag to obtain very low aluminium content
US4636353A (en) * 1983-07-05 1987-01-13 Rhone-Poulenc Specialites Chimiques Novel neodymium/iron alloys
CN87105177A (en) * 1986-07-21 1988-03-09 日立金属株式会社 Produce the method for neodymium-iron-boron permanent magnet
CN101562068A (en) * 2009-01-20 2009-10-21 内蒙古科技大学 Method for manufacturing neodymium iron boron permanent-magnet material by neodymium iron boron powder scrap
CN103484604A (en) * 2013-09-10 2014-01-01 韩盛伟 Refining method of neodymium iron boron permanent magnet material
CN203893673U (en) * 2014-06-13 2014-10-22 邻水县薪宇机械制造有限公司 Automatic feeding port of aluminum alloy smelting furnace
CN208765504U (en) * 2018-09-11 2019-04-19 唐山国丰钢铁有限公司 Charging device for iron-smelting furnace

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2460334A1 (en) * 1979-07-04 1981-01-23 Roechling Burbach Gmbh Stahl Electroslag remelting of steel and alloys for turbine rotors - using alkaline earth metal to deoxidise fluorspar contg. slag to obtain very low aluminium content
US4636353A (en) * 1983-07-05 1987-01-13 Rhone-Poulenc Specialites Chimiques Novel neodymium/iron alloys
CN87105177A (en) * 1986-07-21 1988-03-09 日立金属株式会社 Produce the method for neodymium-iron-boron permanent magnet
CN101562068A (en) * 2009-01-20 2009-10-21 内蒙古科技大学 Method for manufacturing neodymium iron boron permanent-magnet material by neodymium iron boron powder scrap
CN103484604A (en) * 2013-09-10 2014-01-01 韩盛伟 Refining method of neodymium iron boron permanent magnet material
CN203893673U (en) * 2014-06-13 2014-10-22 邻水县薪宇机械制造有限公司 Automatic feeding port of aluminum alloy smelting furnace
CN208765504U (en) * 2018-09-11 2019-04-19 唐山国丰钢铁有限公司 Charging device for iron-smelting furnace

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