CN109935463B - Method for reducing oxygen content of rare earth neodymium iron boron - Google Patents
Method for reducing oxygen content of rare earth neodymium iron boron Download PDFInfo
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Abstract
The invention relates to the field of permanent magnet materials, and discloses a method for reducing the oxygen content of rare earth neodymium iron boron, wherein S1: weighing neodymium iron boron raw materials and an additive with the oxygen affinity higher than that of iron; placing the obtained material in a vacuum rapid hardening furnace for vacuumizing; s2: preheating the materials and removing water vapor; s3: after the preheating is finished, heating and melting the materials; s4: removing oxides floating on the surface of the melt, and casting; cooling the cast sheet and discharging; s5: hydrogen crushing the cast sheet; s6: carrying out airflow milling on the materials to prepare powder; s7: and forming and sintering the powder to obtain the neodymium iron boron magnet. According to the invention, the alloy additive is added into the neodymium iron boron raw material to reduce the oxygen content in the neodymium iron boron, the method can effectively reduce the usage amount of heavy rare earth elements, and a foundation is provided for producing the rare earth neodymium iron boron magnet with low cost and high performance.
Description
Technical Field
The invention relates to the field of permanent magnet materials, in particular to a method for reducing the oxygen content of rare earth neodymium iron boron.
Background
The sintered Nd-Fe-B magnet is a permanent magnet material with the strongest comprehensive magnetic performance in the world, is widely applied to the fields of energy, transportation, machinery, medical treatment, computers, household appliances and the like by virtue of the excellent characteristics and cost performance of the sintered Nd-Fe-B magnet material over the traditional permanent magnet material, and plays an important role in national economy.
Among the technical indexes of magnetic materials, the magnetic energy product is the most important. The magnetic energy product represents the amount of energy per unit volume of the magnet that generates the external magnetic field. The high magnetic energy product means that a smaller magnet can be used to output more power on the motor. Neodymium iron boron is an important rare earth permanent magnet material, has the characteristics of high magnetic energy product, high coercivity, light weight, low cost and the like, is a magnet with the highest cost performance so far, and is reputed as 'magical king'. The emergence of neodymium iron boron makes the magnetic device develop towards high efficiency, miniaturization and light weight.
In the prior art, heavy rare earth elements Dy, Tb and Ho and other non-metal elements are mainly added in a compounding manner in order to obtain high-performance sintered neodymium iron boron, but the heavy rare earth elements Dy, Tb and Ho have higher cost, and more seriously, the heavy rare earth elements have been proved to have very limited reserves. At the present consumption rate, people will face the dilemma of scarcity of heavy rare earth elements in the near future. Therefore, it is an urgent strategy to develop a preparation technology of high performance sintered nd-fe-b with low content of heavy rare earth such as Dy, Tb, Ho, etc. However, the oxygen content in the ndfeb magnet has a great influence on the magnetic performance in actual production.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for reducing the oxygen content of rare earth neodymium iron boron.
The specific technical scheme of the invention is as follows: a method for reducing the oxygen content of rare earth neodymium iron boron comprises the following steps:
s1: weighing neodymium iron boron raw materials and an additive with the oxygen affinity higher than that of iron; the additive amount is 0.02-0.2wt% of the total amount; and placing the obtained material in a crucible of a vacuum rapid hardening furnace, and vacuumizing the vacuum rapid hardening furnace.
S2: preheating the materials and removing the water vapor of the materials.
S3: after the preheating is finished, the material is further heated to reach the temperature of 1400 ℃ to 1500 ℃.
S4: removing oxides floating on the surface of the melt obtained in the step S4, and casting to obtain a cast sheet; and cooling the cast sheet in an inert gas atmosphere and discharging.
S5: the cast piece obtained in S4 was subjected to hydrogen crushing.
S6: and (3) carrying out airflow milling on the hydrogen-crushed material to obtain powder.
S7: and (4) molding and sintering the powder obtained in the step S6 to obtain the neodymium iron boron magnet.
The invention directly adds elements with stronger affinity with oxygen than that of iron in neodymium iron boron into the ingredients in the forms of iron alloy or metal blocks, etc., and generates a precipitate MxOy which is insoluble in molten steel with oxygen during smelting, wherein the density of the MxOy is generally less than that of the molten steel, and the MxOy can float upwards and be removed during casting. The neodymium iron boron prepared by the invention has simple process, reduces the oxygen content in the cast sheet, improves the magnetic property of the magnet, reduces the dosage of heavy rare earth and reduces the material cost.
Preferably, in S1, the additive is at least one of silicon-manganese alloy, silicon-iron, ferromanganese, ferroaluminum, and calcium silico-aluminum.
In the present invention, the additive has a higher affinity for oxygen than iron, and thus can deprive the raw materials of oxygen in the oxide after melting, and when the additive forms an oxide, the additive floats up because of its lower specific gravity than other elements, and at this time, the oxygen content in the raw materials can be effectively reduced by removing the floating matter.
In addition, the content of the additive in the method of the present invention needs to be strictly controlled, and the additive amount of the present invention needs to be the amount of the additive in the method of the present invention to achieve a good technical effect. If the additive is excessively added, the comprehensive magnetic property of the neodymium iron boron is obviously reduced; if the addition amount is too small, the deoxidation effect is not obvious, and the reduction range of the oxygen content in the cast sheet is not obvious.
Preferably, in S1, the neodymium iron boron is prepared from the following raw materials: raFe100-a-b-cBbMc(ii) a The mass percentage is 35 percent or more and more than or equal to a and more than or equal to 20 percent, 1.2 percent or more than or equal to b and more than or equal to 0.9 percent, 6 percent or more than or equal to c and more than or equal to 0 percent, and R is one or more of Nd, Pr, Dy, Tb, Gd and Ho; m is one or more of Co, Ga, Al, Cu, Nb, Zr and Mn.
Preferably, in S1, materials are added according to the melting point from high to low, and the vacuum is pumped to less than or equal to 8 Pa.
The sequence of adding raw materials is strictly controlled during melting, and materials are added according to the melting point from high to low, because: the high-melting-point raw material can be preferentially contacted with molten steel for melting in the melting process, so that the risk that the high-melting-point raw material is not completely fused is reduced, and if the low-melting-point raw material is preferentially contacted with the molten steel, such as light rare earth PrNd, the burning loss of low-melting-point metal can be caused, and the final magnetic performance is seriously influenced.
Preferably, in S2, the preheating power is 120-200 kW.
Preferably, in S3, the heating power is 350-550kW, and the heating time is 7-15 min.
Preferably, in S4, the casting is carried out at a copper roll speed of 35-45r/min, and the average thickness of the obtained cast sheet is 0.2-0.4 mm.
Preferably, in S4, the inert gas is argon, and the cooling is performed for 120-150 min.
Preferably, in S5, the specific process of hydrogen fragmentation is: and putting the cast piece into a hydrogen crushing furnace, vacuumizing to less than or equal to 10Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 60-210min, vacuumizing and heating to 500-plus-one temperature of 600 ℃ for dehydrogenation, the dehydrogenation time is 240-plus-one time of 420min, opening the furnace after the dehydrogenation is finished, spraying and cooling the furnace body to less than or equal to 60 ℃, and taking out the furnace to obtain the neodymium iron boron fine powder.
Preferably, in S7, the specific process of molding and sintering is as follows: placing the powder subjected to the jet milling into a press with a magnetic field of more than or equal to 1.4T for molding, placing the molded green body into a sintering furnace, and vacuumizing to 5.0 multiplied by 10-1Heating to 350-450 ℃ at the temperature of 5-10 ℃/min below Pa, and preserving heat for 40-80min to carry out glue discharging treatment; heating to 850-class 950 ℃ at a heating rate of 3-5 ℃/min, preserving heat for 240min, heating to 1060-class 1080 ℃ at a heating rate of 2-4 ℃/min, preserving heat for 360min, performing final densification on the magnet, and then filling argon and air-cooling to below 150 ℃ to obtain a sintered magnet; heating the sintered magnet to 880-920 ℃ at the heating rate of 5-8 ℃/min, preserving heat for 90-180 min, then air-cooling to below 150 ℃ to finish the first stage aging treatment, heating to 450-550 ℃ at the heating rate of 5-8 ℃/min, preserving heat for 180-300 min, air-cooling to below 60 ℃, discharging and finishing the second stage aging treatment.
The hydrogen crushing vacuum pumping is carried out until the pressure is less than or equal to 10Pa, which is mainly used for ensuring the vacuum degree in the furnace to prevent the magnetic property reduction caused by the over-high oxygen content of the powder in the hydrogen absorption process, the hydrogen absorption time is 60-210min to ensure that the powder is effectively crushed, the dehydrogenation temperature is over 600 ℃ to easily cause incomplete dehydrogenation, the disproportionation reaction of the powder can be caused when the temperature is over to influence the performance of a magnet, the dehydrogenation time is 240-420min to ensure that the powder is completely dehydrogenated, and the cooling temperature is less than or equal to 60 ℃ to prevent the over-high oxygen content of the powder when the powder is taken out of the.
Sintering vacuum degree of 5.0X 10-1The Pa below is to ensure the vacuum degree in the furnace to prevent the oxidation of the green body, and the temperature is raised to 350-450 ℃ at the speed of 5-10 ℃/min and is kept for 40-80min to rapidly raise the temperature to remove impurity gas in the magnetDischarging the body and the glue, heating to 850-950 ℃ at a heating speed of 3-5 ℃/min, preserving heat for 120-240min, slowly heating to prevent the product from subfissure caused by overlarge temperature difference, discharging residual hydrogen in the magnet, and finally heating to 1060-1080 ℃ at a heating speed of 2-4 ℃/min, wherein the heat preservation is also used for preventing the product from subfissure caused by overhigh temperature rise and the heat preservation is used for magnet densification; the intrinsic coercive force of the magnet can be rapidly improved by the first section of aging and the second section of aging.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, the alloy additive is added into the neodymium iron boron raw material to reduce the oxygen content in the neodymium iron boron, the method can effectively reduce the usage amount of heavy rare earth elements, and a foundation is provided for producing the rare earth neodymium iron boron magnet with low cost and high performance. The oxygen content of the finally obtained neodymium iron boron cast sheet can be controlled to be lower than 121ppm, and the method makes remarkable progress compared with the prior art.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A method for reducing the oxygen content of rare earth neodymium iron boron comprises the following steps:
s1: weighing neodymium iron boron raw materials and an additive with the oxygen affinity higher than that of iron; the additive amount is 0.02-0.2wt% of the total amount; placing the obtained material in a crucible of a vacuum rapid hardening furnace from high melting point to low melting point, and vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8P.
S2: the materials are preheated at the temperature of 120-200kW, and the water vapor of the materials is removed.
S3: after the preheating is finished, the material is further heated for 7-15min under 350-550kW, so that the temperature reaches 1400-1500 ℃.
S4: removing oxides floating on the surface of the melt obtained in S4, and casting at the copper roller rotating speed of 35-45r/min to obtain a cast sheet (the average thickness is 0.2-0.4 mm); and cooling the cast piece in an inert gas (preferably argon) atmosphere for 120-150min and discharging.
S5: the cast piece obtained in S4 was subjected to hydrogen crushing.
S6: and (3) carrying out airflow milling on the hydrogen-crushed material to obtain powder.
S7: and (4) molding and sintering the powder obtained in the step S6 to obtain the neodymium iron boron magnet.
Preferably, in S1, the additive is at least one of silicon-manganese alloy, silicon-iron, ferromanganese, ferroaluminum, and calcium silico-aluminum.
Preferably, in S1, the neodymium iron boron is prepared from the following raw materials: raFe100-a-b-cBbMc(ii) a The mass percentage is 35 percent or more and more than or equal to a and more than or equal to 20 percent, 1.2 percent or more than or equal to b and more than or equal to 0.9 percent, 6 percent or more than or equal to c and more than or equal to 0 percent, and R is one or more of Nd, Pr, Dy, Tb, Gd and Ho; m is one or more of Co, Ga, Al, Cu, Nb, Zr and Mn.
Preferably, in S5, the specific process of hydrogen fragmentation is: and putting the cast piece into a hydrogen crushing furnace, vacuumizing to less than or equal to 10Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 60-210min, vacuumizing and heating to 500-plus-one temperature of 600 ℃ for dehydrogenation, the dehydrogenation time is 240-plus-one time of 420min, opening the furnace after the dehydrogenation is finished, spraying and cooling the furnace body to less than or equal to 60 ℃, and taking out the furnace to obtain the neodymium iron boron fine powder.
Preferably, in S7, the specific process of molding and sintering is as follows: placing the powder subjected to the jet milling into a press with a magnetic field of more than or equal to 1.4T for molding, placing the molded green body into a sintering furnace, and vacuumizing to 5.0 multiplied by 10-1Heating to 350-450 ℃ at the temperature of 5-10 ℃/min below Pa, and preserving heat for 40-80min to carry out glue discharging treatment; heating to 850-class 950 ℃ at a heating rate of 3-5 ℃/min, preserving heat for 240min, heating to 1060-class 1080 ℃ at a heating rate of 2-4 ℃/min, preserving heat for 360min, performing final densification on the magnet, and then filling argon and air-cooling to below 150 ℃ to obtain a sintered magnet; heating the sintered magnet to 880-920 ℃ at the heating rate of 5-8 ℃/min, preserving heat for 90-180 min, then air-cooling to below 150 ℃ to finish the first stage aging treatment, heating to 450-550 ℃ at the heating rate of 5-8 ℃/min, preserving heat for 180-300 min, air-cooling to below 60 ℃, discharging and finishing the second stage aging treatment.
Example 1
According to the proportion (Nd, Pr)28.8Dy0.8Gd1Co1.5Cu0.2Al1Nb0.4Fe residueB0.97(wt%) mixing, and adding 0.1% ferromanganese as additive A according to mass ratio; marking as B without adding additives, placing A, B rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 150kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 520kW for 12 minutes after preheating is finished, then carrying out casting with the temperature of 1460 ℃ and the rotating speed of a copper roller set to 40r/min, wherein the average thickness of cast pieces is 0.28mm, and cooling the cast pieces in an argon atmosphere for 120 minutes to take out of the furnace; and (3) putting the A, B cast sheet into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after the hydrogen absorption is finished, and dehydrogenating, wherein the dehydrogenation time is 380min, opening a heating furnace after the dehydrogenation is finished, spraying and cooling the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After airflow milling, the powder particle size of the fine powder A is 3.05-3.15um consistent with that of the fine powder B. A. B powder is pressed in an oriented magnetic field of more than or equal to 1.6T to form a square blank of 55 multiplied by 40 multiplied by 31(mm), the blank is placed in a sintering furnace and vacuumized to 5.0 multiplied by 10-1pa is heated to 400 ℃ at the temperature rising rate of 8 ℃/min, and the temperature is kept for 60min for discharging the rubber; heating to 900 deg.C at a heating rate of 3 deg.C/min, maintaining for 180min, heating to 1060 deg.C at a heating rate of 2 deg.C/min, maintaining for 330min to obtain final densified magnet, and air-cooling to 150 deg.C or below to obtain sintered magnet; and heating the sintered magnet to 900 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 500 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃ and discharging to finish the second stage aging treatment to obtain the sintered magnet. The cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 1
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| A | 120 | 12.58 | 20.85 | 38.12 |
| B | 189 | 12.63 | 20.13 | 38.53 |
From the results of Table 1, it can be seen that the oxygen content in cast piece A was much lower than that in cast piece B, while the magnetic properties of the magnet HcJ produced by cast piece A were higher than that produced by cast piece B.
Example 2
According to the proportion (Nd, Pr)28.8Dy1.5Co1.5Cu0.15Al0.35Nb0.3Fe and B0.96(wt%) mixing, and adding 0.15% ferrosilicon as additive by mass ratio and recording as C; marking as D without adding additives, placing C, D rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of a melting point from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 170kW for preheating to ensure removal of water vapor and the like of raw materials, setting the power to 500kW for 13 minutes after preheating is finished, then measuring temperature to 1450 ℃, and setting the rotating speed of a copper roller to be 13 minutesSetting the speed to be 38r/min for casting, wherein the average thickness of the cast piece is 0.29mm, and cooling the cast piece in an argon atmosphere for 120 minutes to discharge; placing C, D cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After the airflow milling, the powder particle size of the fine powder C is consistent with that of the fine powder D and is 3.00-3.10 um. C. D, pressing and molding the powder material into a square blank of 60 multiplied by 45 multiplied by 32(mm) in an oriented magnetic field of more than or equal to 1.6T, placing the blank into a sintering furnace, and vacuumizing to 5.0 multiplied by 10-1Heating to 400 ℃ below Pa according to the heating degree of 8 ℃/min, and keeping the temperature for 60min to carry out rubber discharge treatment; heating to 900 deg.C at a heating rate of 4 deg.C/min, maintaining for 180min, heating to 1060 deg.C at a heating rate of 3 deg.C/min, maintaining for 300min to obtain final densified magnet, and filling argon and air cooling to below 150 deg.C to obtain sintered magnet; heating the sintered magnet to 900 ℃ at a heating rate of 7 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 500 ℃ at a heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 2
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| C | 112 | 13.48 | 19.73 | 44.39 |
| D | 191 | 13.51 | 18.61 | 44.62 |
From the results of Table 2, it can be seen that the oxygen content in cast piece C was much lower than that in cast piece D, while the magnetic properties of the magnet produced by cast piece C, HcJ, were higher than that produced by cast piece D.
Example 3
According to the proportion (Nd, Pr)26.5Dy4.5Co1.5Cu0.2Al0.6Nb0.3Fe and B0.96(wt%) mixing, adding 0.12% of silicon-manganese alloy as additive and marking as E; marking as F without adding additives, placing E, F rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 160kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 530kW for 12 minutes after preheating is finished, then carrying out casting with the temperature of 1460 ℃ and the rotation speed of a copper roller set to 36r/min, wherein the average thickness of cast pieces is 0.27mm, and cooling the cast pieces in an argon atmosphere for 120 minutes to take out of the furnace; placing E, F cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After the air flow is milled, the mixture is subjected to air flow milling,the powder particle size of the fine powder E is 2.95-3.15um as compared with that of the fine powder F. E. Pressing the F powder in an oriented magnetic field of more than or equal to 1.6T to form a square blank of 63 multiplied by 39 multiplied by 33(mm), placing the blank in a sintering furnace, and vacuumizing to 5.0 multiplied by 10-1Heating to 400 ℃ below Pa according to the heating degree of 8 ℃/min, and keeping the temperature for 60min to carry out rubber discharge treatment; heating to 890 ℃ at a heating rate of 3 ℃/min, preserving heat for 180min, heating to 1065 ℃ at a heating rate of 2 ℃/min, preserving heat for 330min, performing final densification of the magnet, and then filling argon and air cooling to below 150 ℃ to obtain a sintered magnet; heating the sintered magnet to 895 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 510 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 3
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| E | 108 | 12.48 | 26.95 | 38.15 |
| F | 193 | 12.52 | 26.03 | 38.27 |
From the results of Table 3, it can be seen that the oxygen content in cast piece E was much lower than that in cast piece F, while the magnetic properties of the magnet HcJ produced by cast piece E were higher than that produced by cast piece F.
Example 4
According to the proportion (Nd, Pr)30.3Dy5.7Co2Cu0.2Al0.1Nb0.3Fe and B0.95(wt%) mixing, and adding 0.15% of aluminum iron as an additive by mass ratio, and recording as G; marking as H without adding additives, placing G, H rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 150kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 520kW for 12 minutes after preheating is finished, then carrying out casting with the temperature of 1470 ℃ and the rotating speed of a copper roller set to 35r/min, wherein the average thickness of cast pieces is 0.27mm, and cooling the cast pieces in an argon atmosphere for 120 minutes to take out of the furnace; and (3) putting the G, H cast sheet into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after the hydrogen absorption is finished, and dehydrogenating, wherein the dehydrogenation time is 380min, opening a heating furnace after the dehydrogenation is finished, spraying and cooling the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After airflow milling, the powder particle size of the fine powder G is 3.1-3.2um consistent with that of the fine powder H. G. H powder is pressed and molded in an oriented magnetic field of more than or equal to 1.6T to form a square blank of 55 multiplied by 40 multiplied by 32mm), the blank is placed in a sintering furnace and is vacuumized to 5.0 multiplied by 10-1pa is heated to 400 ℃ at the temperature rising rate of 8 ℃/min, and the temperature is kept for 60min for discharging the rubber; heating to 900 deg.C at a heating rate of 3 deg.C/min, maintaining for 180min, heating to 1065 deg.C at a heating rate of 2 deg.C/min, maintaining for 330min to obtain final densification, and air cooling with argonObtaining a sintered magnet at a temperature below 150 ℃; heating the sintered magnet to 895 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 495 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 4
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| G | 116 | 13.05 | 26.31 | 41.27 |
| H | 187 | 13.12 | 25.63 | 41.53 |
From the results of Table 4, it can be seen that the oxygen content in cast piece G was much lower than that in cast piece H, while the magnetic properties of the magnet HcJ produced by cast piece G were higher than that produced by cast piece H.
Example 5
According to the proportion (Nd, Pr)30.5Dy1.2Co1Cu0.15Al0.1Nb0.3Fe and B0.97(wt%) mixing, adding 0.18% of silicon-aluminum-barium-calcium according to the mass ratio as an additive and recording as I; marking as J without adding additives, placing I, J rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 140kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 510kW for 13 minutes after preheating is finished, then carrying out casting with the temperature of 1450 ℃ and the rotating speed of a copper roller set to 38r/min, wherein the average thickness of cast pieces is 0.28mm, and cooling the cast pieces in an argon atmosphere for 120 minutes to take out of the furnace; placing I, J cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After airflow milling, the powder particle size of the fine powder I is 3.15-3.25um consistent with that of the fine powder J. I. J powder is pressed and molded into a square blank of 58 multiplied by 42.5 multiplied by 33mm) in an oriented magnetic field of more than or equal to 1.6T, the blank is placed into a sintering furnace and vacuumized to 5.0 multiplied by 10-1pa is heated to 400 ℃ at the temperature rising rate of 8 ℃/min, and the temperature is kept for 60min for discharging the rubber; heating to 900 deg.C at a heating rate of 3 deg.C/min, maintaining for 180min, heating to 1060 deg.C at a heating rate of 2 deg.C/min, maintaining for 270min for final densification, and air-cooling to 150 deg.C or below to obtain sintered magnet; heating the sintered magnet to 900 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 505 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 5
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| I | 121 | 14.03 | 17.65 | 49.58 |
| J | 191 | 14.09 | 16.93 | 49.72 |
From the results of Table 5, it can be seen that the oxygen content in cast piece I is much lower than that in cast piece J, while the magnetic properties of the magnet produced by cast piece I, HcJ, are higher than those produced by cast piece J.
Example 6
According to the proportion (Nd, Pr)29.8Tb1Co1Cu0.1Zr0.1Fe and B0.96(wt%) mixing, and adding 0.1% of aluminum iron and 0.08% of ferromanganese as additives according to the mass ratio, and recording as K; marking as L without adding additive, placing K, L rare earth neodymium iron boron material in sequence from high melting point to low melting pointVacuumizing the vacuum rapid hardening furnace to less than or equal to 8Pa in a crucible of the air rapid hardening furnace, setting the heating power to 150kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 510kW for 13 minutes after preheating is finished, then carrying out casting at the temperature of 1450 ℃ and the rotation speed of a copper roller to 36r/min, wherein the average thickness of cast pieces is 0.28mm, and cooling the cast pieces in the argon atmosphere for 120 minutes to take out the cast pieces; placing K, L cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After the airflow milling, the powder particle size of the fine powder K is 2.9-3.1um as same as that of the fine powder L. K. L powder is pressed and molded into a square blank of 45 multiplied by 32.7 multiplied by 28mm) in an oriented magnetic field of more than or equal to 1.6T, the blank is placed into a sintering furnace and vacuumized to 5.0 multiplied by 10-1Heating to 400 ℃ below Pa according to the heating degree of 8 ℃/min, and keeping the temperature for 60min to carry out rubber discharge treatment; heating to 900 ℃ at a heating rate of 3 ℃/min, preserving heat for 180min, heating to 1070 ℃ at a heating rate of 2 ℃/min, preserving heat for 330min, performing final densification on the magnet, and then filling argon and air cooling to below 150 ℃ to obtain a sintered magnet; heating the sintered magnet to 900 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 505 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 6
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| K | 106 | 14.35 | 17.81 | 51.66 |
| L | 185 | 14.41 | 17.15 | 51.83 |
From the results of Table 6, it can be seen that the oxygen content in cast piece K is much lower than that in cast piece L, while the magnetic properties of the magnet HcJ produced by cast piece K are higher than those produced by cast piece L.
Comparative example 1
Comparative example 1 differs from example 1 in that the amount of addition of the oxygen scavenger is larger than the upper limit of the range of the present invention. And a performance comparison was made.
According to the proportion (Nd, Pr)30Dy1Co1Cu0.15Al0.4Zr0.1Fe and B0.96(wt%) mixing, adding 0.3% ferromanganese as additive and marking as M; marking as N without adding additives, placing M, N rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 150kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 510kW for 13 minutes after preheating is finished, then carrying out casting with the temperature measuring of 1460 ℃ and the rotation speed of a copper roller set to 35r/min, and casting sheets with average temperatureThe thickness is 0.28mm, and the cast piece is cooled in argon atmosphere for 120 minutes and taken out of the furnace; placing M, N cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After airflow milling, the powder particle size of the fine powder M is 2.9-3.0um as the powder particle size of the fine powder N. K. Pressing the L powder into 67.8 × 42 × 39mm square blank in an oriented magnetic field of 1.6T or more), placing the blank in a sintering furnace, and vacuumizing to 5.0 × 10-1Heating to 400 ℃ below Pa according to the heating degree of 8 ℃/min, and keeping the temperature for 60min to carry out rubber discharge treatment; heating to 900 deg.C at a heating rate of 3 deg.C/min, maintaining for 180min, heating to 1060 deg.C at a heating rate of 2 deg.C/min, maintaining for 300min for final densification, and air-cooling to 150 deg.C or below to obtain sintered magnet; heating the sintered magnet to 900 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 500 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 7
From the results of Table 7, it can be seen that the oxygen content in the cast piece M was much lower than that in the cast piece N, but the magnet properties Br and (BH) M were greatly reduced.
Comparative example 2
According to the proportion (Nd, Pr)28Dy2Gd1Co1.5Cu0.2Al0.8Zr0.1Fe and B0.95(wt%) mixing, adding 0.01% of aluminum iron as additive and marking as O according to mass ratio; marking as P without adding additives, placing O, P rare earth neodymium iron boron materials into a crucible of a vacuum rapid hardening furnace according to a sequence of melting points from high to low, vacuumizing the vacuum rapid hardening furnace to be less than or equal to 8Pa, setting heating power to 150kW for preheating to ensure that water vapor and the like of raw materials are removed, setting the power to 510kW for 13 minutes after preheating is finished, then carrying out casting with the temperature of 1470 ℃ and the rotating speed of a copper roller set to 35r/min, wherein the average thickness of cast pieces is 0.27mm, and cooling the cast pieces in an argon atmosphere for 120 minutes to take out of the furnace; placing O, P cast sheets into a hydrogen crushing furnace, vacuumizing to less than or equal to 5Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 150min, vacuumizing and heating to 550 ℃ after hydrogen absorption is finished, and performing dehydrogenation, wherein the dehydrogenation time is 380min, opening a heating furnace after dehydrogenation to perform spray cooling on the furnace body, and discharging at the temperature of less than or equal to 40 ℃ to obtain the neodymium iron boron fine powder. After the airflow milling, the powder particle size of the fine powder O is consistent with that of the fine powder P and is 2.85-2.95 um. O, P pressing the powder into 67.8 × 42 × 39mm square blank in an oriented magnetic field of 1.6T or more), placing the blank in a sintering furnace, and vacuumizing to 5.0 × 10-1Heating to 400 ℃ below Pa according to the heating degree of 8 ℃/min, and keeping the temperature for 60min to carry out rubber discharge treatment; heating to 900 deg.C at a heating rate of 3 deg.C/min, maintaining for 180min, heating to 1060 deg.C at a heating rate of 2 deg.C/min, maintaining for 300min for final densification, and air-cooling to 150 deg.C or below to obtain sintered magnet; heating the sintered magnet to 900 ℃ at the heating rate of 6 ℃/min, preserving heat for 120min, then performing air cooling to below 150 ℃ to finish the first stage aging treatment, heating to 500 ℃ at the heating rate of 6 ℃/min, preserving heat for 240min, performing air cooling to below 60 ℃, discharging to finish the second stage aging treatment, and preparing the sintered magnet: the cast piece is taken to compare the oxygen content, and a standard sample of a magnet phi 10 multiplied by 10(mm) is taken to compare and test the magnetic performance.
TABLE 8
| Item | Cast piece oxygen content/ppm | Br/KGs | HcJ/KOe | (BH)m/MGsOe |
| M | 169 | 12.49 | 23.63 | 37.89 |
| N | 176 | 12.51 | 23.57 | 37.91 |
From the results of Table 8, it can be seen that the oxygen content in the cast slab O was not greatly different from that in the cast slab P, and the magnet performance was not greatly improved.
As can be seen from comparative examples 1-2, the content of the additive in the present invention is critical and cannot be varied at will. Furthermore, as can be seen from the oxygen contents of the ndfeb obtained in examples 1 to 6, the present invention can control the oxygen content of the ndfeb to 121ppm or less, and is a significant improvement over the prior art.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (7)
1. A method for reducing the oxygen content of rare earth neodymium iron boron is characterized by comprising the following steps:
s1: weighing neodymium iron boron raw materials and an additive with the oxygen affinity higher than that of iron; the additive amount is 0.02-0.2wt% of the total amount; placing the obtained material in a crucible of a vacuum rapid hardening furnace, and vacuumizing the vacuum rapid hardening furnace; the additive is silicon-aluminum-barium-calcium;
s2: preheating the materials, and removing water vapor of the materials;
s3: after the preheating is finished, further heating the materials to enable the temperature to reach 1400-1500 ℃;
s4: removing oxides floating on the surface of the melt obtained in the step S4, and casting to obtain a cast sheet; cooling the cast sheet in an inert gas atmosphere and discharging;
s5: hydrogen crushing the cast sheet obtained in S4: placing the cast piece into a hydrogen crushing furnace, vacuumizing to be less than or equal to 10Pa, filling hydrogen into the furnace for hydrogen absorption reaction, wherein the hydrogen absorption time is 60-210min, vacuumizing and heating to 500-;
s6: carrying out airflow milling on the hydrogen-crushed material to prepare powder;
s7: and (3) molding and sintering the powder obtained in the step S6: placing the powder subjected to the jet milling into a press with a magnetic field of more than or equal to 1.4T for molding, placing the molded green body into a sintering furnace, and vacuumizing to 5.0 multiplied by 10-1Heating to 350-450 ℃ at the temperature of 5-10 ℃/min below Pa, and preserving heat for 40-80min to carry out glue discharging treatment; heating to 850-class 950 ℃ at a heating rate of 3-5 ℃/min, preserving heat for 240min, heating to 1060-class 1080 ℃ at a heating rate of 2-4 ℃/min, preserving heat for 360min, performing final densification on the magnet, and then filling argon and air-cooling to below 150 ℃ to obtain a sintered magnet; heating the sintered magnet to 880-920 ℃ at the heating rate of 5-8 ℃/min, preserving the heat for 90-180 min, and then air-cooling to 15 DEG CFinishing the first stage of aging treatment at the temperature below 0 ℃, heating to 450-550 ℃ at the heating rate of 5-8 ℃/min, preserving the heat for 180-300 min, and taking out of the furnace to finish the second stage of aging treatment after air cooling to the temperature below 60 ℃; and (5) preparing the neodymium iron boron magnet.
2. The method for reducing the oxygen content of the rare earth neodymium iron boron according to claim 1, wherein in S1, the neodymium iron boron is prepared from the following raw materials: raFe100-a-b-cBbMc(ii) a The mass percentage is 35 percent or more and more than or equal to a and more than or equal to 20 percent, 1.2 percent or more than or equal to b and more than or equal to 0.9 percent, 6 percent or more than or equal to c and more than or equal to 0 percent, and R is one or more of Nd, Pr, Dy, Tb, Gd and Ho; m is one or more of Co, Ga, Al, Cu, Nb, Zr and Mn.
3. The method for reducing the oxygen content of the rare earth neodymium iron boron according to claim 1, wherein in S1, materials are added according to the melting point from high to low, and the vacuum is pumped to less than or equal to 8 Pa.
4. The method as claimed in claim 1, wherein the preheating power in S2 is 200kW and 120-.
5. The method as claimed in claim 1, wherein in S3, the heating power is 350-550kW, and the heating time is 7-15 min.
6. The method for reducing the oxygen content of the rare earth neodymium iron boron according to claim 1, wherein in S4, the casting is carried out at the copper roller rotating speed of 35-45r/min, and the average thickness of the obtained cast sheet is 0.2-0.4 mm.
7. The method as claimed in claim 1, wherein in S4, the inert gas is argon, and the cooling time is 120-150 min.
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