CN110544569A - neodymium-iron-boron magnet and production process thereof - Google Patents
neodymium-iron-boron magnet and production process thereof Download PDFInfo
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Abstract
the invention discloses a neodymium iron boron magnet, which relates to the field of magnetic materials and comprises the following components, by mass, 15-20% of Nd, 4-8% of Pr, 1-2% of Tb, 1-8% of La, 1-6% of Ce, 1-2% of Co, 0.1-0.2% of Cu, 0.5-1.5% of Al, 1-4% of Ho, 1-4% of Dy, 1-12% of Gd, 1-1.3% of Ga, 0.92-1% of B, and the balance of Fe and inevitable impurities. Here, through adding 1 ~ 6% Ce, not only saved the cost, also avoided the problem that the biggest magnetic energy product of neodymium iron boron descends by a wide margin simultaneously, secondly, the production technology of this application is convenient, and combines the content of adding Ce, has improved the coercive force of neodymium iron boron magnet effectively.
Description
Technical Field
the invention relates to the field of magnetic material production, in particular to a neodymium iron boron magnet and a production process thereof.
background
The neodymium magnet is also called neodymium iron boron magnet (NdFeB magnet), and is a tetragonal crystal formed of neodymium, iron, and boron (Nd 2Fe 14B). In 1982, the neodymium magnet was discovered by a person living in the special metal of Sumitomo. The magnetic energy product (BHmax) of this magnet was greater than that of a samarium cobalt magnet, and was the largest in magnetic energy product worldwide at that time. Later, Sumitomo specialty metals successfully developed powder metallurgy (powder metallurgy) and general automotive successfully developed melt-spinning (melt-spinning) processes that could produce neodymium-iron-boron magnets. This magnet is a permanent magnet that is second only to absolute zero holmium magnets in magnetism today and is also the most commonly used rare earth magnet. In addition, the ndfeb magnet is widely used in electronic products such as hard disks, mobile phones, earphones, and battery-powered tools.
With the wider application field of the neodymium iron boron, the dosage is increased every year. The praseodymium-neodymium rare earth elements are generally expensive due to the price. On the basis of ensuring the magnetic performance of the normal neodymium iron boron magnet, how to reduce the production cost of the neodymium iron boron becomes an important problem to be solved urgently in the industry.
Disclosure of Invention
The invention aims to provide a neodymium iron boron magnet, which is characterized in that a certain amount of cerium is added in a neodymium iron boron raw material, so that the cost is saved, meanwhile, the maximum magnetic energy product of the produced neodymium iron boron is reduced by a small amplitude, and in addition, the magnetic performance of the neodymium iron boron is also greatly improved after the production process operation is carried out.
the above object of the present invention is achieved by the following technical solutions: a neodymium iron boron magnet is characterized in that: the material comprises, by mass, 15-20% of Nd, 4-8% of Pr, 1-2% of Tb, 1-8% of La, 1-6% of Ce, 1-2% of Co, 0.1-0.2% of Cu, 0.5-1.5% of Al, 1-4% of Ho, 1-4% of Dy, 1-12% of Gd, 1-1.3% of Ga, 0.92-1% of B, and the balance of Fe and inevitable impurities.
By adopting the technical scheme, the price of Ce is much lower than that of Nd and Pr, and Ce can form Ce2Fe14B with Fe and B, and can replace elements such as PrNd, and the like, so that the production cost of the neodymium iron boron is reduced. The addition amount of Ce is controlled to be 1-6% of the total amount, so that the reduction rate of Hcj and (BH) max of the finished neodymium iron boron magnet is less than 1%. Therefore, the cost of the neodymium iron boron is reduced, and the reduction of the magnetic performance of the neodymium iron boron is effectively controlled.
preferably, the total mass ratio of Ce to NdPr is 1: 12 to 16.
By adopting the technical scheme, the ratio of the mass of Ce to the total mass of NdPr is controlled to be 1: 12-16, as shown in the test results of the examples, the BHmax of the NdFeB has a small reduction rate.
a production process of a neodymium iron boron magnet comprises the following steps,
firstly, weighing prepared raw materials according to component requirements, and then carrying out melt refining on the raw materials to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller for melt spinning, thereby obtaining a melt spinning sheet;
Step three, adding the melt-spun sheet into a hydrogen breaking furnace for hydrogen breaking treatment to obtain hydrogen powder;
step four, grinding the hydrogen crushed powder into raw material powder through an airflow mill;
Step five, pressing and forming the raw material powder under the protection of nitrogen to obtain a green body;
step six, pressing the green body for the second time through isostatic pressing oil pressure;
Step seven, placing the green body subjected to isostatic pressing oil pressure in a sintering furnace for sintering, and then performing two-stage aging to obtain a semi-finished product;
and step eight, after the semi-finished product is machined, magnetizing to obtain a finished product of the neodymium iron boron magnet.
preferably, the temperature of the raw material in the step one is controlled to be 1400-1500 ℃ in the refining process, and the holding time is 5-20 min.
Preferably, the temperature of the molten liquid in the second step is controlled to be 1400-1450 ℃.
preferably, in the seventh step, the sintering temperature is gradually increased from the normal temperature to 700-900 ℃, kept for 20-30 min, and then increased to 1500-1800 ℃ and kept for 4-6 h.
By adopting the technical scheme, the sintering temperature is firstly increased to 700-900 ℃, and in the process, because the activity of Ce is stronger than that of other rare earths such as PrNd, a liquid phase is more easily generated, so that the uniform shrinkage density of the product is improved, and the strength of the magnet is improved.
Preferably, in the seventh step, the first-stage aging temperature of the two-stage aging is 850-920 ℃, and the temperature is kept for 1-3 hours, and the second-stage aging temperature is 500-650 ℃, and the temperature is kept for 4-6 hours.
by adopting the technical scheme, the sintering temperature is controlled to be 1500-1800 ℃, the primary aging temperature is controlled to be 850-920 ℃, and the secondary aging temperature is controlled to be 500-650 ℃, so that the finally produced neodymium iron boron magnet can overcome the adverse effect caused by adding Ce, and the coercive force of the neodymium iron boron magnet is obviously improved.
Preferably, after sintering is completed, the sintering furnace is evacuated, and then the green body is cooled to the primary aging temperature along with the sintering furnace.
because under conventional conditions, in order to improve the cooling efficiency of sintered neodymium iron boron, argon is generally introduced in the industry for cooling, but the temperature of a green body is rapidly reduced in the process, so that the final product is easy to deform. After the sintering furnace is vacuumized, the temperature of the green body is naturally reduced along with the sintering furnace, so that the problem of deformation of the product is effectively avoided.
Preferably, in the seventh step, before sintering the green body, the green body is placed in a graphite box with the bottom uniformly sprayed with corundum powder.
Through adopting above-mentioned technical scheme, place the unburned bricks in the graphite box, like this in sintering process, can help making the unburned bricks be heated evenly on the one hand, and also possess certain heat preservation effect, on the other hand the stone ink horn also can provide the C element, can be used to detach unnecessary oxygen element in the unburned bricks, is favorable to guaranteeing magnetic property and the mechanical strength of neodymium iron boron like this.
meanwhile, metals such as Ce are easy to melt out in the sintering process, so that after the magnets are cooled, the magnets can be bonded with the bottom of the graphite box, and therefore when the magnets are taken down, flaws are easy to appear on the surfaces of the magnets, and the workload of machining is increased. And the corundum powder can make the graphite box bottom smooth on the one hand, and on the other hand also can make unburned bricks and graphite box bottom have certain space to avoid the possibility that final magnetic path and graphite box bond.
Preferably, the granularity of the raw material powder in the fourth step is controlled to be D50: 4.6-5.0 μm, SMD: 2.8 to 3.2 μm.
By adopting the technical scheme, the adverse effect of Ce on the Hcj of the neodymium iron boron can be effectively compensated. In addition, if the particle size of the mixed powder is controlled to be less than 4.6 μm in D50 and less than 2.8 μm in SMD, the Hcj offset of Nd-Fe-B is not large, but the difficulty of processing is further increased, thus being not beneficial to improving economic benefit.
In conclusion, the beneficial technical effects of the invention are as follows:
1. By adding 1-6 wt% of Ce into the neodymium iron boron material, the production cost of the neodymium iron boron is effectively reduced, and meanwhile, the magnetic property of the neodymium iron boron is effectively controlled to be reduced;
2. by adjusting the sintering temperature and time and the two-stage aging temperature and time of the neodymium iron boron, the influence of Ce on the neodymium iron boron magnet is effectively overcome, and the coercive force of the neodymium iron boron is effectively improved;
3. Before sintering, the corundum powder is firstly sprayed in the graphite box, so that the magnetic material and the bottom of the graphite box can be prevented from being bonded, and the possibility of generating flaws on the magnetic material is effectively reduced.
Detailed Description
the first embodiment,
a production process of a neodymium iron boron magnet comprises the following steps:
firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1400 ℃, and preserving heat for 20min to obtain molten liquid;
step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
Step seven, putting the pressed green body into a graphite box which is fully sprayed with the corundum powder at the bottom, then putting the green body and the graphite box into a vacuum sintering furnace, gradually increasing the temperature of the vacuum sintering furnace from normal temperature to 700 ℃, preserving heat for 30min, then gradually increasing the temperature to 1500 ℃ and preserving heat for 6 h;
and step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to the primary aging temperature of 850 ℃, preserving heat for 1h, then cooling to the secondary aging temperature of 500 ℃, preserving heat for 6h, and finally cooling to the normal temperature to obtain a semi-finished product.
And step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 15% Nd, 4% Pr, 1% Tb, 1% La, 1% Ce, 1% Co, 0.1% Cu, 0.5% Al, 1% Ho, 1% Dy, 1% Gd, 1% Ga, 0.92% B, and the balance Fe and inevitable impurities.
comparative examples A,
The difference from the first embodiment is only that in the seventh step, the maximum temperature of the vacuum sintering furnace is increased to 1400 ℃, and the temperature is kept for 30 min;
And in the eighth step, the primary aging temperature is 800 ℃, the heat preservation time is 2 hours, the secondary aging temperature is 450 ℃, and the heat preservation time is 7 hours.
example II,
a production process of a neodymium iron boron magnet comprises the following steps:
firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1450 ℃, and preserving heat for 13min to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
Step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
Step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
Putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
Step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
step seven, the pressed green body is put into a graphite box which is fully sprayed with the corundum powder at the bottom, then the green body and the graphite box are put into a vacuum sintering furnace, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 800 ℃, the temperature is kept for 25min, then the temperature is gradually increased to 1650 ℃, and the temperature is kept for 5 h;
and step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to 880 ℃ of the primary aging temperature, preserving heat for 2 hours, then cooling to 580 ℃ of the secondary aging temperature, preserving heat for 5 hours, and finally cooling to normal temperature to obtain a semi-finished product.
And step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 17% Nd, 6% Pr, 1.5% Tb, 4.5% La, 3.5% Ce, 1.5% Co, 0.15% Cu, 1% Al, 2.5% Ho, 2.5% Dy, 6.5% Gd, 1.1% Ga, 0.96% B, and the balance Fe and inevitable impurities.
comparative example II,
the difference from the second embodiment is only that in the seventh step, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 1650 ℃.
example III,
A production process of a neodymium iron boron magnet comprises the following steps:
Firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1500 ℃, and preserving the temperature for 5min to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
Step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
Putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
step seven, the pressed green body is put into a graphite box which is fully sprayed with the corundum powder at the bottom, then the green body and the graphite box are put into a vacuum sintering furnace, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 900 ℃ and is kept for 20min, then the temperature is gradually increased to 1800 ℃ again and is kept for 4 h;
and step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to the primary aging temperature of 920 ℃, preserving heat for 1h, then cooling to the secondary aging temperature of 650 ℃, preserving heat for 4h, and finally cooling to the normal temperature to obtain a semi-finished product.
and step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 20% Nd, 8% Pr, 2% Tb, 8% La, 6% Ce, 2% Co, 0.2% Cu, 1.5% Al, 4% Ho, 4% Dy, 12% Gd, 1.3% Ga, 1% B, and the balance Fe and inevitable impurities.
Comparative example III,
the difference from the third embodiment is only that in the seventh embodiment, the maximum temperature of the vacuum sintering furnace is raised to 1900 ℃, and the temperature is kept for 3 hours;
The eight steps of the first-stage aging temperature is 970 ℃, the temperature is kept for 0.5h, and the second-stage aging temperature is 700 ℃ for 3 h.
Example four,
A production process of a neodymium iron boron magnet comprises the following steps:
Firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1450 ℃, and preserving heat for 13min to obtain molten liquid;
step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
Step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
Putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
Step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
step seven, the pressed green body is put into a graphite box which is fully sprayed with the corundum powder at the bottom, then the green body and the graphite box are put into a vacuum sintering furnace, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 800 ℃, the temperature is kept for 25min, then the temperature is gradually increased to 1650 ℃, and the temperature is kept for 5 h;
and step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to 880 ℃ of the primary aging temperature, preserving heat for 2 hours, then cooling to 580 ℃ of the secondary aging temperature, preserving heat for 5 hours, and finally cooling to normal temperature to obtain a semi-finished product.
and step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
Here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 16% Nd, 8% Pr, 1.5% Tb, 4.5% La, 2% Ce, 1.5% Co, 0.15% Cu, 1% Al, 2.5% Ho, 2.5% Dy, 6.5% Gd, 1.1% Ga, 0.96% B, and the balance Fe and inevitable impurities.
Comparative example four,
it differs from example four only in that Ce was not contained, and the mass fraction of Nd was 17% and the mass fraction of Pr was 9%.
Example V,
a production process of a neodymium iron boron magnet comprises the following steps:
firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1450 ℃, and preserving heat for 13min to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
Step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
Step seven, the pressed green body is put into a graphite box which is fully sprayed with the corundum powder at the bottom, then the green body and the graphite box are put into a vacuum sintering furnace, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 800 ℃, the temperature is kept for 25min, then the temperature is gradually increased to 1650 ℃, and the temperature is kept for 5 h;
and step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to 880 ℃ of the primary aging temperature, preserving heat for 2 hours, then cooling to 580 ℃ of the secondary aging temperature, preserving heat for 5 hours, and finally cooling to normal temperature to obtain a semi-finished product.
And step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
Here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 15% Nd, 4.5% Pr, 1.5% Tb, 4.5% La, 1.5% Ce, 1.5% Co, 0.15% Cu, 1% Al, 2.5% Ho, 2.5% Dy, 6.5% Gd, 1.1% Ga, 0.96% B, and the balance Fe and inevitable impurities.
Comparative example V,
it differs from example five only in that Ce was not contained, and the mass fraction of Nd was 16% and the mass fraction of Pr was 5%.
Example six,
A production process of a neodymium iron boron magnet comprises the following steps:
firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature at 1450 ℃, and preserving heat for 13min to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
Putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
Step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
Step seven, the pressed green body is put into a graphite box which is fully sprayed with the corundum powder at the bottom, then the green body and the graphite box are put into a vacuum sintering furnace, the temperature of the vacuum sintering furnace is gradually increased from normal temperature to 800 ℃, the temperature is kept for 25min, then the temperature is gradually increased to 1650 ℃, and the temperature is kept for 5 h;
And step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to 880 ℃ of the primary aging temperature, preserving heat for 2 hours, then cooling to 580 ℃ of the secondary aging temperature, preserving heat for 5 hours, and finally cooling to normal temperature to obtain a semi-finished product.
and step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
Here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 20% Nd, 8% Pr, 1.5% Tb, 4.5% La, 1.75% Ce, 1.5% Co, 0.15% Cu, 1% Al, 2.5% Ho, 2.5% Dy, 6.5% Gd, 1.1% Ga, 0.96% B, and the balance Fe and inevitable impurities.
comparative example six,
The difference from example six is only that the particle size of the raw meal in step four is D50:5.3 μm and SMD: 3.5 μm.
example seven,
A production process of a neodymium iron boron magnet comprises the following steps:
Firstly, preparing raw materials of a neodymium iron boron magnet according to the content of each component of a final finished product, then adding the raw materials into a smelting furnace for smelting, controlling the temperature to be 1400-1500 ℃, and preserving the temperature for 5-20 min to obtain molten liquid;
Step two, pouring the molten liquid on a water-cooled roller in a vacuum melt-spun furnace for melt-spinning, thereby obtaining a melt-spun sheet;
step three, collecting the melt-spun sheets in the step two, adding the melt-spun sheets into a hydrogen breaking furnace, introducing hydrogen into the hydrogen breaking furnace, and then heating while performing hydrogen breaking treatment to obtain hydrogen crushed powder;
Step four, adding the hydrogen crushed powder into an airflow grinding device, and after the airflow grinding treatment, obtaining D50 of 4.6-5.0 μm and SMD: 2.8-3.2 μm raw material powder;
Putting the raw material powder into a die in a nitrogen environment for compression molding to obtain a green body;
step six, putting the green body into a bag, vacuumizing, and then performing secondary pressing through isostatic pressing oil pressure;
step seven, putting the pressed green body into a graphite box with the bottom fully sprayed with the corundum powder, then putting the green body and the graphite box into a vacuum sintering furnace, gradually increasing the temperature of the vacuum sintering furnace from the normal temperature to 700-900 ℃, preserving heat for 20-30 min, then gradually increasing the temperature to 1500-1800 ℃, and preserving heat for 4-6 h;
And step eight, vacuumizing the vacuum sintering furnace, naturally cooling the vacuum sintering furnace inside to the primary aging temperature of 850-920 ℃, preserving heat for 1-3 hours, then cooling to the secondary aging temperature of 500-650 ℃, preserving heat for 4-6 hours, and finally cooling to the normal temperature to obtain a semi-finished product.
and step nine, machining the semi-finished product, and then magnetizing to obtain the finished neodymium iron boron magnet.
Here, the mass fractions of the respective components in the finished Nd-Fe-B magnet were 16% Nd, 5% Pr, 1.5% Tb, 4.5% La, 2.1% Ce, 1.5% Co, 0.15% Cu, 1% Al, 2.5% Ho, 2.5% Dy, 6.5% Gd, 1.1% Ga, 0.96% B, and the balance Fe and inevitable impurities.
Comparative examples seven,
the difference from the seventh embodiment is only that in the seventh embodiment, corundum powder is sprinkled on the bottom of the graphite box.
the 20 ℃ coercive force, the 20 ℃ maximum magnetic energy and the compressive strength of the ndfeb of the examples one to seven and the comparative examples one to six were tested, and the appearance of the sintered ndfeb was observed to obtain the results of the following tables one and two:
TABLE I, EXAMPLES I TO VII, PERFORMANCE TEST RESULTS FOR ND-FE-B MAGNETS
Table two, comparative example one to comparative example seven each performance test results of the neodymium iron boron magnet
The test results of table one and table two were analyzed:
1. Through the respective comparison of the first embodiment, the third embodiment, the fourth embodiment and the fifth embodiment with the first comparative embodiment, the third comparative embodiment, the fourth comparative embodiment and the fifth comparative embodiment, it can be seen that Ce in the present application is controlled to be 1-6 wt% of the total amount of the ndfeb magnet, and when the sintering temperature of the ndfeb is 1500-1800 ℃, the heat preservation time is 4-6 hours, the first-order aging temperature is 850-920 ℃, the heat preservation time is 1-3 hours, the second-order aging temperature is 500-650 ℃, and the heat preservation time is 4-6 hours, the coercivity of the ndfeb magnet can be effectively improved under the condition that the decrease of the maximum magnetic energy product of the ndfeb magnet is effectively relieved, and through the respective comparison of the fourth embodiment and the fifth embodiment, and the fourth comparative embodiment and the fifth comparative embodiment, it can be seen that when the mass: when the magnetic flux density is 12-16 hours, the frequency of the maximum energy product reduction of the neodymium iron boron magnet is minimum;
2. as can be seen from the comparison between the second embodiment and the first embodiment, the temperature is increased to 700-900 ℃ in the sintering process, so that the strength of the neodymium iron boron magnet is improved;
3. As can be seen from a comparison of example six and comparative example six, the particle size of the raw powder was controlled to D50:4.6 to 5.0 μm and SMD: 2.8-3.2 mu m, so that the influence of the added Ce on the coercivity of the neodymium iron boron can be effectively weakened;
4. As can be seen from the comparison between the seventh embodiment and the seventh comparative example, the bottom of the graphite box is filled with the corundum powder, so that the semi-finished product can be prevented from being bonded with the bottom of the graphite box, and the obvious gap on the surface of the semi-finished product is reduced when a worker takes the semi-finished product.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (10)
1. A neodymium iron boron magnet is characterized in that: the material comprises, by mass, 15-20% of Nd, 4-8% of Pr, 1-2% of Tb, 1-8% of La, 1-6% of Ce, 1-2% of Co, 0.1-0.2% of Cu, 0.5-1.5% of Al, 1-4% of Ho, 1-4% of Dy, 1-12% of Gd, 1-1.3% of Ga, 0.92-1% of B, and the balance of Fe and inevitable impurities.
2. a neodymium iron boron magnet according to claim 1, characterized in that: the total mass ratio of Ce to NdPr is 1: 12 to 16.
3. a process for producing a neodymium iron boron magnet as claimed in any one of claims 1 and 2, wherein: comprises the following steps of (a) carrying out,
Firstly, weighing prepared raw materials according to component requirements, and then carrying out melt refining on the raw materials to obtain molten liquid;
step two, pouring the molten liquid on a water-cooled roller for melt spinning, thereby obtaining a melt spinning sheet;
Step three, adding the melt-spun sheet into a hydrogen breaking furnace for hydrogen breaking treatment to obtain hydrogen powder;
step four, grinding the hydrogen crushed powder into raw material powder through an airflow mill;
Step five, pressing and forming the raw material powder under the protection of nitrogen to obtain a green body;
Step six, pressing the green body for the second time through isostatic pressing oil pressure;
Step seven, placing the green body subjected to isostatic pressing oil pressure in a sintering furnace for sintering, and then performing two-stage aging to obtain a semi-finished product;
and step eight, after the semi-finished product is machined, magnetizing to obtain a finished product of the neodymium iron boron magnet.
4. A process for producing a neodymium iron boron magnet according to claim 3, characterized in that: in the first step, the temperature of the raw material is controlled to be 1400-1500 ℃ in the refining process, and the holding time is 5-20 min.
5. The production process of the neodymium-iron-boron magnet according to claim 4, characterized in that: and controlling the temperature of the molten liquid during pouring in the step two to be 1400-1450 ℃.
6. the production process of the neodymium-iron-boron magnet according to claim 5, characterized in that: and seventhly, gradually increasing the sintering temperature from the normal temperature to 700-900 ℃, keeping the temperature for 20-30 min, and then increasing the temperature to 1500-1800 ℃ and keeping the temperature for 4-6 h.
7. the production process of a neodymium iron boron magnet according to claim 6, characterized in that: and seventhly, keeping the primary aging temperature of the two-stage aging at 850-920 ℃ for 1-3 hours, and keeping the secondary aging temperature at 500-650 ℃ for 4-6 hours.
8. The production process of a neodymium iron boron magnet according to claim 7, characterized in that: and after sintering is finished, vacuumizing the sintering furnace, and then cooling the green body to the primary aging temperature along with the sintering furnace.
9. A process for producing a neodymium iron boron magnet according to claim 3, characterized in that: and seventhly, before sintering the green body, placing the green body in a graphite box with the bottom uniformly full of corundum powder.
10. a process for producing a neodymium iron boron magnet according to claim 3, characterized in that: and the granularity of the raw material powder in the fourth step is controlled to be D50: 4.6-5.0 μm, SMD: 2.8 to 3.2 μm.
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