Magnetic performance detection method of anisotropic rare earth permanent magnet powder

Abstract

The invention discloses a magnetic performance detection method for anisotropic rare earth permanent magnet powder, and belongs to the field of magnetic materials. The detection method comprises the following steps: firstly, formulating a self magnetic powder mark range, comparing with a standard sample magnetic powder, and drawing a standard curve; the method comprises the following steps: respectively manufacturing a standard sample magnetic powder paraffin sample column and a to-be-tested sample magnetic powder paraffin sample column through matching of a paraffin sample column manufacturing mold and an orientation clamp, then testing the magnetic performance of the anisotropic permanent magnet sample column by using a permanent magnet characteristic automatic measuring instrument, inquiring a standard curve, converting to obtain a magnetic energy product value of the to-be-tested sample powder, and determining a corresponding mark; the magnetic performance detection of the anisotropic rare earth permanent magnet powder is completed. The detection method is low in price, the sample preparation process is convenient to operate, the detection period is short, repeatability is high, and errors are small.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic materials, and in particular to a method for detecting the magnetic properties of anisotropic rare earth permanent magnetic powder. Background Art

[0002] In 1990, Coey et al. synthesized the interstitial atomic metal compound Sm2Fe by gas-solid reaction. 17 N x After the introduction of SmFeN, SmFeN has become a strong competitor of NdFeB permanent magnet powder due to its superior intrinsic magnetic properties to Nd-Fe-B (NdFeB), higher Curie temperature, better corrosion resistance and other advantages. It plays an irreplaceable role in high temperature corrosion resistance environment and is known as the "fourth generation of rare earth permanent magnet".

[0003] At present, there are many methods for preparing anisotropic SmFeN powder, such as reduction diffusion, solution rapid quenching, co-precipitation, etc. However, no matter which preparation method is used, the powder must be crushed to a particle size of 1 to 3 μm to show its best magnetic properties.

[0004] At present, the detection method of the magnetic properties of anisotropic samarium iron nitrogen powder is relatively simple, and basically VSM (vibrating sample magnetometer) equipment is used to test its magnetic properties. However, VSM equipment is relatively expensive; and the sample preparation process of the powder has high technical requirements. For example, patent CN 112002548 A mentions the use of AB adhesive to make sample columns, which are cured for 2-3 hours. The curing time is long and the efficiency is low, which is not easy to apply to batch production processes. In addition, due to the high viscosity of AB adhesive, the particle size of samarium iron nitrogen powder is small (average particle size 1-3μm), and the powders are prone to agglomeration, making it difficult to mix evenly with AB colloid. The sample preparation process has high technical requirements and is not easy to operate. In addition, factors such as the small amount of VSM test samples lead to large errors in the detection process of the magnetic properties of anisotropic samarium iron nitrogen powder. Therefore, it is urgent to find a method for quickly and effectively detecting the magnetic properties of anisotropic samarium iron nitrogen powder.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for detecting the magnetic properties of anisotropic rare earth permanent magnet powder, which can quickly and effectively detect the magnetic properties of anisotropic samarium iron nitrogen powder, thereby solving the above technical problems existing in the prior art.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0009] Step 1, obtaining anisotropic samarium iron nitride permanent magnetic powder with a magnetic energy product value of 38 MGOe and a coercive force of 11 kOe as a standard sample magnetic powder;

[0010] Step 2, drawing a magnetic energy product standard curve according to the relationship between the magnetic energy product of the anisotropic rare earth permanent magnetic powder within the grade range and the magnetic energy product of the standard sample magnetic powder;

[0011] Step 3, respectively preparing a paraffin-like column of the magnetic powder of the standard sample and a paraffin-like column of the magnetic powder of the sample to be tested;

[0012] Step 4, using a permanent magnetic property automatic measuring instrument to test the paraffin sample column of the standard sample magnetic powder and the paraffin sample column of the sample magnetic powder prepared in step 3, respectively, to obtain the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder;

[0013] Step 5, converting the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder to be tested to obtain the corresponding magnetic energy product value of the standard sample magnetic powder and the test magnetic energy product value of the sample magnetic powder to be tested;

[0014] Step 6, taking the magnetic energy product value of the standard sample magnetic powder as a reference, according to the relationship between the test magnetic energy product value of the sample magnetic powder and the magnetic energy product value of the standard sample magnetic powder, query the actual magnetic energy product value of the sample magnetic powder to be tested according to the magnetic energy product standard curve drawn in step 2, and complete the magnetic property detection of the anisotropic rare earth permanent magnet powder to be tested.

[0015] Compared with the prior art, the method for detecting magnetic properties of anisotropic rare earth permanent magnet powder provided by the present invention has the following beneficial effects:

[0016] By using standard sample magnetic powder and drawing a magnetic energy product standard curve, combined with paraffin sample column production, the actual magnetic energy product value of the measured magnetic powder can be quickly and accurately obtained by querying the magnetic energy product standard curve according to the test magnetic energy product value of the sample magnetic powder to be tested, and then the magnetic properties of the measured anisotropic rare earth permanent magnet powder can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 The present invention provides a flowchart of a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder.

[0019] Figure 2 A schematic diagram of drawing a standard magnetic energy product curve for the detection method provided in an embodiment of the present invention.

[0020] Figure 3 Schematic diagram of the structure of the paraffin-like column sample preparation mold in the detection method provided in an embodiment of the present invention; wherein, (a) is a front schematic diagram of the paraffin-like column sample preparation mold; (b) is a left side schematic diagram of the paraffin-like column sample preparation mold; (c) is a right side schematic diagram of the paraffin-like column sample preparation mold.

[0021] Figure 4 A schematic diagram of sample orientation in a detection method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the specific content of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0023] First, the terms that may be used in this article are explained as follows:

[0024] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0025] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0026] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0027] The term "parts by mass" refers to the mass ratio relationship between multiple components. For example, if it is described that component X is x parts by mass and component Y is y parts by mass, then the mass ratio of component X to component Y is x:y. 1 part by mass can represent any mass, for example, 1 part by mass can be represented as 1 kg or 3.1415926 kg. The sum of the parts by mass of all components is not necessarily 100 parts, but can be greater than 100 parts, less than 100 parts or equal to 100 parts. Unless otherwise specified, the parts, proportions and percentages described herein are all measured by mass.

[0028] When concentration, temperature, pressure, size or other parameters are expressed in the form of a numerical range, the numerical range should be understood to specifically disclose all ranges formed by the pairing of any upper limit, lower limit, and preferred value in the numerical range, regardless of whether the range is explicitly stated; for example, if a numerical range of "2 to 8" is stated, the numerical range should be interpreted as including ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise specified, the numerical ranges stated herein include both their end values ​​and all integers and fractions within the numerical range.

[0029] The scheme provided by the present invention is described in detail below. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professionals in the field. If the specific conditions are not specified in the embodiments of the present invention, they are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used in the embodiments of the present invention, they are all conventional products that can be purchased commercially.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0031] Step 1, obtaining anisotropic samarium iron nitride permanent magnetic powder with a magnetic energy product value of 38 MGOe and a coercive force of 11 kOe as a standard sample magnetic powder;

[0032] Step 2, drawing a magnetic energy product standard curve according to the relationship between the magnetic energy product of the anisotropic rare earth permanent magnetic powder within the grade range and the magnetic energy product of the standard sample magnetic powder;

[0033] Step 3, respectively preparing a paraffin-like column of the magnetic powder of the standard sample and a paraffin-like column of the magnetic powder of the sample to be tested;

[0034] Step 4, using a permanent magnetic property automatic measuring instrument to test the paraffin sample column of the standard sample magnetic powder and the paraffin sample column of the sample magnetic powder prepared in step 3, respectively, to obtain the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder;

[0035] Step 5, converting the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder to be tested to obtain the corresponding magnetic energy product value of the standard sample magnetic powder and the test magnetic energy product value of the sample magnetic powder to be tested;

[0036] Step 6, taking the magnetic energy product value of the standard sample magnetic powder as a reference, according to the relationship between the test magnetic energy product value of the sample magnetic powder and the magnetic energy product value of the standard sample magnetic powder, query the actual magnetic energy product value of the sample magnetic powder according to the magnetic energy product standard curve drawn in step 2, and complete the magnetic property detection of the anisotropic rare earth permanent magnet powder to be tested.

[0037] Preferably, in step 1 of the above method, commercially available anisotropic samarium iron nitrogen powder with a magnetic energy product (BH) max = 38MGOe and a coercive force Hcj = 11kOe (hereinafter referred to as commercially available 38-11 powder) is purchased and used as the standard sample magnetic powder.

[0038] Preferably, in step 2 of the above method, the grade range of the standard sample magnetic powder and the sample magnetic powder to be tested is formulated in the following manner, and a standard curve is drawn, including:

[0039] Step 21, determining that the magnetic energy products corresponding to the anisotropic rare earth permanent magnet powders of various grades are 32MGOe, 34MGOe, 36MGOe, 38MGOe, and 40MGOe;

[0040] Step 22, taking the magnetic energy product value 38MGOe of the standard sample magnetic powder obtained in step 1 as a reference, calculating the percentage of the magnetic energy product value of each grade of anisotropic rare earth permanent magnetic powder in step 21 to the magnetic energy product of the standard sample magnetic powder;

[0041] Step 23, a magnetic energy product standard curve is drawn according to the percentage of the magnetic energy product value of each grade of anisotropic rare earth permanent magnetic powder and the magnetic energy product of the standard sample magnetic powder. The magnetic energy product standard curve is as follows: Figure 2 shown.

[0042] In the above step 22, the actual magnetic energy product of the grade powder ranges from 31 to 33 MGOe. In the step 22, the percentage of the magnetic energy product of the anisotropic rare earth permanent magnetic powder of grade 32 MGOe to the magnetic energy product of the standard sample magnetic powder is calculated as follows: 32÷38×100%=84.2%.

[0043] Preferably, in step 3 of the above method, the steps of preparing the paraffin-like column of the standard sample magnetic powder and the paraffin-like column of the sample magnetic powder to be tested are the same, except that the paraffin-like column of the standard sample magnetic powder uses anisotropic rare earth permanent magnetic powder corresponding to the standard sample magnetic powder, and the paraffin-like column of the sample magnetic powder to be tested uses anisotropic rare earth permanent magnetic powder corresponding to the sample magnetic powder to be tested. The steps of preparing the paraffin-like column are performed in the following manner, including:

[0044] Step 31, placing a predetermined amount of low melting point paraffin wax in a heating container, placing the heating container in an oven, and heating until the low melting point paraffin wax is completely melted;

[0045] Step 32, pouring the anisotropic rare earth permanent magnet powder into the heating container of the melted paraffin, stirring and mixing it with the low melting point paraffin in the heating container, and then heating it in the oven;

[0046] Step 33, after the paraffin wax is melted, stirring again to completely mix the low melting point paraffin wax and the anisotropic permanent magnetic powder to obtain a mixture sample;

[0047] Step 34, blocking one side of the sample adding through hole of the paraffin sample column sample preparation mold, and placing the mold in the oven for constant temperature treatment until the paraffin sample column sample preparation mold reaches a constant temperature;

[0048] Step 35, filling the mixture sample obtained in step 33 into the sealed paraffin sample column sample preparation mold that has reached a constant temperature after the treatment in step 34, compacting the mixture sample to drive out bubbles during the filling process, and sealing the other side of the sample filling through hole of the paraffin sample column sample preparation mold after filling;

[0049] Step 36, placing the paraffin sample column sample preparation mold processed in step 35 in the middle position of the orientation fixture, so that the sample in the paraffin sample column sample preparation mold is at the center position of the extreme end of the orientation fixture;

[0050] Step 37, respectively placing an electric heating rod and a temperature sensor into the heating hole and the temperature measuring hole of the paraffin sample column sample preparation mold, turning on the heating power switch of the electric heating rod for constant temperature heating until the mixture sample is completely softened;

[0051] Step 38, turning on the orientation fixture switch to orient the mixture sample, removing the electric heating rod after a few minutes, and allowing the mixture sample to solidify in the magnetic field for 5 to 15 minutes;

[0052] Step 39, after the paraffin in the mixture sample solidifies, the oriented paraffin sample column is taken out, and a pulsed magnetic field is used to magnetize the paraffin sample column to a saturated state, thereby obtaining a magnetic powder paraffin sample column.

[0053] Preferably, in step 31 of the above method, the melting point of the low melting point paraffin wax is 48-52°C, and the heating temperature of the oven is 50-65°C;

[0054] In the step 32, anisotropic rare earth permanent magnet powder is added into the heating container, and during the mixing process of the anisotropic rare earth permanent magnet powder and the low melting point paraffin, the heating container is placed in the oven, and the oven door is opened to perform the above operation;

[0055] In the step 34, one side of the sample adding through hole of the paraffin sample column sample preparation mold is tightly sealed by a tight transparent tape;

[0056] In the step 35, after the paraffin sample column is filled, the other side of the sample adding through hole of the sample preparation mold is tightly sealed by transparent tape;

[0057] In step 37, the constant temperature heating time is 3 to 5 minutes;

[0058] In step 39, the solidification time is 10 to 12 minutes.

[0059] Preferably, in the above method, the mold body of the paraffin sample column sample preparation mold is a plate-like structure, which is provided with a sample adding through hole, heating holes are arranged on the periphery of the sample adding through hole, and a temperature measuring hole is arranged on the mold body on the side of the sample adding through hole.

[0060] Preferably, in the above method, there are two heating holes, namely a first heating hole and a second heating hole, the first heating hole is arranged on the mold body above the sample adding through hole, and the second heating hole is arranged on the mold body below the sample adding through hole.

[0061] Preferably, the mold body is a rectangular plate.

[0062] Preferably, in the above method, the mold body is made of a plate made of non-magnetic material.

[0063] Preferably, in the above method, the non-magnetic conductive material plate is any one of bakelite plate, polytetrafluoroplastic plate and aluminum plate.

[0064] Preferably, in the above method, the thickness of the mold body is 7 mm, the diameter of the sample adding through hole on the mold body is φ9.5 mm to φ10 mm, and the thickness of the sample adding through hole is 7 mm.

[0065] Preferably, the mold body adopts a rectangular plate body, one side of the thin surface of the rectangular plate body is the front side, and the other side is the back side, a sample adding through hole is arranged on the side surface of the rectangular plate body, a heating hole is arranged on the front side of the rectangular plate body, and the front end of the heating hole is close to the outer periphery of the sample adding through hole, and the first heating hole and the second heating hole are arranged on the back side of the rectangular plate body.

[0066] Preferably, in the above method, in the step 32 of making the paraffin-like column, the content of the low-melting-point paraffin in the mixture of the low-melting-point paraffin and the anisotropic rare earth permanent magnet powder is 10-30wt%.

[0067] In summary, the method of the embodiment of the present invention, by adopting standard sample magnetic powder and drawing a magnetic energy product standard curve, combined with paraffin sample column production, can quickly query the magnetic energy product standard curve according to the test magnetic energy product value of the sample magnetic powder to be tested to obtain an accurate actual magnetic energy product value of the measured magnetic powder, and then determine the magnetic properties of the measured anisotropic rare earth permanent magnet powder.

[0068] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the solution provided by the embodiment of the present invention is described in detail with specific embodiments below.

[0069] Example 1

[0070] This embodiment provides a method for detecting the magnetic properties of anisotropic rare earth permanent magnet powder, which is applicable to various types of rare earth permanent magnet powder, especially to anisotropic samarium iron nitrogen powder with fine particle size. Figure 1 As shown, including:

[0071] Step 1, purchasing commercially available anisotropic samarium iron nitrogen powder with a magnetic energy product (BH) max = 38MGOe and a coercive force Hcj = 11kOe as a standard sample powder, hereinafter referred to as commercially available 38-11 powder;

[0072] Step 2, establish the magnetic powder grade range and draw a standard curve;

[0073] Step 21, the corresponding magnetic energy levels of the grades are (BH)max=32, 34, 36, 38, 40MGOe. The actual magnetic energy product range of 32MGOe grade powder is 31-33MGOe, and the rest are similar;

[0074] Step 22, taking the magnetic energy product (BH) max = 38MGOe of commercially available 38-11 powder as a benchmark, calculate the corresponding relationship of the magnetic energy product of other grades (with the percentage of 38MGOe), such as 32÷38×100%=84.2%;

[0075] Step 23, draw a standard curve, the curve is as follows Figure 2 shown.

[0076] Step 3: Using commercially available 38-11 powder as a standard sample, prepare paraffin-like columns of commercially available 38-11 powder and sample powder to be tested respectively.

[0077] The paraffin sample column preparation method of step 3 is as follows. The preparation methods of the paraffin sample columns of the commercially available 38-11 powder and the sample powder to be tested are the same. The difference lies in selecting the corresponding powders when using the powders, including:

[0078] Step 31, weigh a certain proportion of low melting point paraffin wax into a beaker, the melting point of the low melting point paraffin wax is 48-52° C., and the amount of the paraffin wax in the mixture with the powder is 10-30wt%;

[0079] Step 32, placing the beaker into an oven to completely melt the low melting point paraffin, the heating temperature of the oven being 50-65°C;

[0080] Step 33, take the anisotropic permanent magnetic powder, pour it into the beaker of the melted paraffin, stir and mix it with the paraffin until it is evenly mixed, heat it in the oven, wait for the paraffin to melt, and stir the paraffin and the anisotropic permanent magnetic powder again to achieve complete mixing, so as to obtain a mixture sample;

[0081] Step 34, a transparent tape is used to seal the opening of one side of the sample adding through hole 2 of the paraffin sample column sample preparation mold to prevent the sample from leaking during the adding process, and the mold is also placed in the above-mentioned oven for constant temperature, and the time is determined by the mold (the structure of the paraffin sample column sample preparation mold is as shown in FIG. Figure 3 As shown, a first heating hole 4 and a second heating hole 5 are arranged on the periphery of the sample adding through hole 2 of the mold body 1, and a temperature measuring hole 3 is arranged on the mold body on the side of the sample adding through hole 2) to reach a constant temperature, and the constant temperature can be achieved in 3 to 5 minutes. The mold body 1 is made of non-magnetic material, and should have a certain hardness and strength. It is not easy to have obvious thermal expansion and contraction under the temperature condition of less than 80°C, or the coefficient of variation is small. Such as bakelite, polytetrafluoroethylene plastic plate, aluminum, etc. Bakery board is preferred because bakelite is not easy to deform by heat, the metal material feels high in temperature, and it is not easy to operate in the oven. The sample preparation mold is a rectangular parallelepiped with a circular through hole of φ9 to 10mm, a thickness of 7mm or 10mm, and the through hole diameter is preferably φ9.5 to φ10mm. When the diameter is less than 9mm, the cross-sectional area of ​​the sample column is smaller than the required range of the magnetic measuring coil, and the error of the test result is large. The closer the size of the sample column is to the cross-sectional area of ​​the magnetic measuring coil, the more real the test result.

[0082] Step 35, fill the above-mentioned evenly stirred mixture of paraffin and permanent magnetic powder into the paraffin sample column sample preparation mold. Pay attention to compacting the sample during the filling process to drive out bubbles. After filling, use transparent tape to stick and seal the opening on the other side of the sample filling hole of the mold to prevent sample leakage.

[0083] Step 36, placing the mold with the added sample in the middle of the orientation fixture to ensure that the sample is at the center of the extreme end of the orientation fixture;

[0084] Step 37, respectively place an electric heating rod and a temperature sensor into the heating hole and the temperature measuring hole of the paraffin sample column sample preparation mold, turn on the heating power switch to heat and keep the temperature constant for several minutes to completely soften the sample. The heating time is preferably 3 to 5 minutes.

[0085] Step 38, turn on the switches of the two poles of the orientation fixture to orient the sample. After a few minutes, remove the electric heating rod to solidify the sample 6 in the magnetic field. A solidification time of 5-15 minutes can meet the sample preparation and sampling requirements, preferably 10-12 minutes. Too short a solidification time will cause the sample to deform during the sampling process, and too long a solidification time will have no other disadvantages except wasting time. Figure 4 , where 7 is the N pole of the pole head of the orientation fixture, and 8 is the S pole of the pole head of the orientation fixture.

[0086] Step 39, after the paraffin in the sample solidifies, take out the oriented sample column, and use a pulsed magnetic field to magnetize it to a saturated state, thus completing the paraffin sample column.

[0087] Step 4, using a permanent magnetic property automatic measuring instrument to test the magnetic properties of the paraffin sample column of the commercially available 38-11 powder and the sample powder to be tested, mainly testing the magnetic energy product (BH) max and the coercive force Hcj index.

[0088] Step 5, convert BH value, (since Hcj has nothing to do with the weight of the powder, and is basically consistent with the VSM test results, the coercivity Hcj value can be directly read from the test results of the permanent magnetic properties automatic measuring instrument without conversion. The magnetic energy product BH is positively correlated with the powder content, so it needs to be converted through a certain coefficient relationship to be obtained.)

[0089] Step 6, using the (BH)max value of the commercially available 38-11 powder paraffin column as a reference, calculate the (BH)max ratio (percentage) of the sample column to be tested and the commercially available 38-11 powder paraffin column, and substitute the above (BH)max ratio into the standard curve drawn in step (2), so as to find out the actual magnetic energy product (BH)max value of the sample to be tested, and determine the actual magnetic energy product (BH)max value of the sample powder to be tested, that is, indirectly determine the magnetic energy product (BH)max value of the anisotropic permanent magnetic powder to be tested, and determine the brand of the sample powder to be tested.

[0090] During the implementation of the present invention, firstly, it is necessary to compare and convert the powders that are already sold on the market and have accurate brands, or the powders that have been accurately tested by VSM equipment as standard samples. And the diameter of the mold through hole is limited to φ9-10mm, and the thickness is 7mm or 10mm. The diameter needs to match the diameter of the magnetic measuring coil. If the through hole diameter is too small, it will affect the magnetic performance test results and the error will be large. If the diameter is too large, it cannot match the magnetic measuring coil and cannot be tested. The thickness can be arbitrarily selected as 7mm or 10mm according to industry standards.

[0091] The present invention also limits the melting temperature of the low melting point paraffin, preferably the low melting point paraffin with a melting point of 48-52° C., and the heating temperature of the oven is 50-65° C. When the melting point is high or the heating temperature is high, it is not easy to operate manually under high temperature conditions. At the same time, repeatedly opening and closing the oven door for operation is more likely to cause energy waste.

[0092] In the present invention, low melting point paraffin is used as a shaping medium, and its addition content is limited to 10-30wt%, preferably 15wt%-20wt%. When the paraffin content is higher than 30wt%, the shrinkage rate of the paraffin sample column is too high during the heating and cooling process, and the sample column is irregular, which affects the performance test. When the paraffin content is lower than 15wt%, the sample column shrinkage rate is very small, but the orientation is incomplete.

[0093] The following uses the detection of the magnetic properties of anisotropic samarium iron nitrogen powder as an example to further illustrate the beneficial effects of the present invention in combination with the embodiments and comparative examples.

[0094] Example 2

[0095] This embodiment provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0096] Weigh 2.5g of paraffin in a beaker, heat it in an oven (60°C) to melt, accurately weigh 10g of commercially available 38-11 permanent magnetic powder, add it to the paraffin and stir evenly, heat and stir repeatedly, fill the mold and place the mold in the orientation fixture and heat for 5 minutes, turn on the power supply for orientation after the paraffin is completely softened, remove the electric heating rod for cooling and curing after 4 minutes. After taking out the paraffin sample column, use a magnetometer to test the magnetic properties, i.e., the magnetic energy product (BH) max and the coercive force Hcj. The test results are shown in the results of Example 2 in Table 1. The test results are used as a standard to determine the magnetic properties of the sample powder.

[0097] Example 3

[0098] This embodiment provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0099] Weigh 2.5g of paraffin in a beaker, heat it in an oven (60°C) to melt, accurately weigh 10g of anisotropic samarium iron nitrogen sample powder A, add it to the paraffin and stir evenly, heat and stir repeatedly, fill the mold and place the mold in the orientation fixture and heat for 5 minutes, turn on the power supply for orientation for 4 minutes after the paraffin is completely softened, remove the electric heating rod for cooling and curing. After taking out the paraffin sample column, use a magnetometer to test the magnetic properties, i.e., the magnetic energy product (BH) max and the coercive force Hcj. The test results are shown in the results of Example 3 in Table 1.

[0100] The ratio of (BH)max of the sample powder A tested using the permanent magnetic property automatic measuring instrument to (BH)max of the standard sample in Example 1 was calculated.

[0101]

[0102] Query the standard curve (attached Figure 1 ).

[0103] 95.85% is numerically closer to 94.7% corresponding to 36MGOe, confirming that the magnetic properties of the anisotropic rare earth permanent magnet powder to be tested belong to the magnetic properties of the permanent magnet powder with the grade of 36MGOe.

[0104] Determine the actual (BH)max value of the sample to be tested.

[0105] By checking the energy product curve, we can know that the (BH)max value of sample powder A is close to 36MGOe, and the Hcj value is 10kOe through the direct reading of the test results of the permanent magnetic properties automatic measuring instrument. Therefore, the energy product (BH)max of the sample to be tested is 36MGOe, and the coercive force Hcj is 10kOe, which means that the anisotropic samarium iron nitrogen sample powder A is anisotropic samarium iron nitrogen powder of grade 36-10.

[0106] Example 4

[0107] This embodiment provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0108] Weigh 2.5g of paraffin in a beaker, heat it in an oven (60°C) to melt, accurately weigh 10g of anisotropic samarium iron nitrogen sample powder B, add it to the paraffin and stir evenly, heat and stir repeatedly, fill the mold and place the mold in the orientation fixture and heat for 5 minutes, turn on the power supply for orientation for 4 minutes after the paraffin is completely softened, remove the electric heating rod for cooling and curing. After taking out the paraffin sample column, use a magnetometer to test the magnetic properties, i.e., the magnetic energy product (BH) max and the coercive force Hcj. The test results are shown in the results of Example 4 in Table 1.

[0109] The ratio of (BH)max of the sample powder A tested using the permanent magnetic property automatic measuring instrument to (BH)max of the standard sample in Example 1 was calculated.

[0110]

[0111] Query the standard curve (attached Figure 1 ).

[0112] 88.05% is numerically closer to 89.5% corresponding to 34MGOe.

[0113] Determine the actual (BH)max value of the sample to be tested.

[0114] By checking the magnetic energy product curve, we can know that the (BH)max value of sample powder B is close to 34MGOe, and the Hcj value is 10kOe through the direct reading of the test results of the permanent magnetic properties automatic measuring instrument. Therefore, the magnetic energy product (BH)max of the sample to be tested is 34MGOe, and the coercive force Hcj is 9kOe, which means that sample powder B is anisotropic samarium iron nitrogen powder of grade 34-09.

[0115] Example 5

[0116] This embodiment provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0117] Weigh 3.33g paraffin in a beaker, heat it in an oven (60°C) to melt, accurately weigh 10g of commercially available 38-11 permanent magnet powder, add it to the paraffin and stir evenly, heat and stir repeatedly, fill the mold and place the mold in the orientation fixture and heat for 5 minutes, turn on the power supply for orientation after the paraffin is completely softened, remove the electric heating rod for cooling and curing after 4 minutes. After taking out the paraffin sample column, use a magnetometer to test the magnetic properties, i.e., the magnetic energy product (BH) max and the coercive force Hcj. The test results are shown in the results of Example 5 in Table 1.

[0118] Example 6

[0119] This embodiment provides a method for detecting magnetic properties of anisotropic rare earth permanent magnet powder, comprising:

[0120] Weigh 2.5g paraffin in a beaker, heat it in an oven (60°C) to melt, accurately weigh 10g of commercially available 38-11 permanent magnet powder, add it to the paraffin and stir evenly, heat and stir repeatedly, fill the mold and place the mold in the orientation fixture and heat for 2 minutes, turn on the power supply for orientation after the paraffin is completely softened, remove the electric heating rod for cooling and curing after 4 minutes. After taking out the paraffin sample column, use a magnetometer to test the magnetic properties, i.e., the magnetic energy product (BH) max and the coercive force Hcj. The test results are shown in the results of Example 6 in Table 1.

[0121] Comparative Example

[0122] The comparative examples are commercially available 38-11 powder, sample powder A, and sample powder B. The magnetic properties of the three samples are tested by VSM detection method to verify the effectiveness and reliability of the magnetic property detection method of the present invention. The test results are shown in Comparative Examples 1 to 3 in Table 1.

[0123]

[0124] It can be seen from the analysis of Table 1 that the detection method of the present invention is effective and reliable by comparing the (BH)max values ​​of Example 2 and Example 3 and the detection results of Comparative Example 1 and Comparative Example 2. In addition, the detection results of Example 4 and Comparative Example 3 once again prove the effectiveness of the present invention.

[0125] Through the analysis and comparison of the above embodiments and comparative examples, the method of the present invention achieves the following technical effects.

[0126] The magnetic properties of the anisotropic samarium iron nitrogen powder tested by the present invention are close to the real value, that is, similar to the VSM test result, indicating that the method of the present invention for detecting the magnetic properties of anisotropic permanent magnetic powder is feasible. The sample preparation method of the present invention has a simple operation process, the magnetic property detection equipment is inexpensive and easy to obtain, and the detection cycle is short and efficient, and has certain application value.

[0127] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for detecting the magnetic properties of anisotropic rare earth permanent magnet powder, characterized in that: include: Step 1, obtaining anisotropic samarium iron nitride permanent magnetic powder with a magnetic energy product value of 38 MGOe and a coercive force of 11 kOe as a standard sample magnetic powder; Step 2, drawing a magnetic energy product standard curve according to the relationship between the magnetic energy product of the anisotropic rare earth permanent magnetic powder within the grade range and the magnetic energy product of the standard sample magnetic powder; Step 3, respectively preparing a paraffin-like column of the magnetic powder of the standard sample and a paraffin-like column of the magnetic powder of the sample to be tested; Step 4, using a permanent magnetic property automatic measuring instrument to test the paraffin sample column of the standard sample magnetic powder and the paraffin sample column of the sample magnetic powder prepared in step 3, respectively, to obtain the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder; Step 5, converting the magnetic energy product of the standard sample magnetic powder and the magnetic energy product of the sample magnetic powder to be tested to obtain the corresponding magnetic energy product value of the standard sample magnetic powder and the test magnetic energy product value of the sample magnetic powder to be tested; Step 6, taking the magnetic energy product value of the standard sample magnetic powder as a reference, according to the relationship between the test magnetic energy product value of the sample magnetic powder and the magnetic energy product value of the standard sample magnetic powder, query the actual magnetic energy product value of the sample magnetic powder according to the magnetic energy product standard curve drawn in step 2, and complete the magnetic property detection of the anisotropic rare earth permanent magnet powder to be tested.

2. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 1, characterized in that: In the step 2, the grade range of the standard sample magnetic powder and the sample magnetic powder to be tested is determined in the following manner, and a standard curve is drawn, including: Step 21, determining that the magnetic energy products corresponding to the anisotropic rare earth permanent magnet powders of various grades are 32MGOe, 34MGOe, 36MGOe, 38MGOe, and 40MGOe; Step 22, taking the magnetic energy product value 38MGOe of the standard sample magnetic powder obtained in step 1 as a reference, calculating the percentage of the magnetic energy product value of each grade of anisotropic rare earth permanent magnetic powder in step 21 to the magnetic energy product of the standard sample magnetic powder; Step 23, plotting a magnetic energy product standard curve based on the percentage of the obtained magnetic energy product values ​​of the anisotropic rare earth permanent magnetic powder of each brand and the magnetic energy product of the standard sample magnetic powder.

3. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 1 or 2, characterized in that: In step 3, the steps of preparing the paraffin-like column of the standard sample magnetic powder and the paraffin-like column of the sample magnetic powder to be tested are the same, except that the paraffin-like column of the standard sample magnetic powder uses anisotropic rare earth permanent magnetic powder corresponding to the standard sample magnetic powder, and the paraffin-like column of the sample magnetic powder to be tested uses anisotropic rare earth permanent magnetic powder corresponding to the sample magnetic powder to be tested. The steps of preparing the paraffin-like column are performed in the following manner, including: Step 31, placing a predetermined amount of low melting point paraffin wax in a heating container, placing the heating container in an oven, and heating until the low melting point paraffin wax is completely melted; Step 32, pouring the anisotropic rare earth permanent magnet powder into the heating container of the melted paraffin, stirring and mixing it with the low melting point paraffin in the heating container, and then heating it in the oven; Step 33, after the paraffin wax is melted, stirring again to completely mix the low melting point paraffin wax and the anisotropic permanent magnetic powder to obtain a mixture sample; Step 34, blocking one side of the sample adding through hole of the paraffin sample column sample preparation mold, and placing the mold in the oven for constant temperature treatment until the paraffin sample column sample preparation mold reaches a constant temperature; Step 35, filling the mixture sample obtained in step 33 into the sealed paraffin sample column sample preparation mold that has reached a constant temperature after the treatment in step 34, compacting the mixture sample to drive out bubbles during the filling process, and sealing the other side of the sample filling through hole of the paraffin sample column sample preparation mold after filling; Step 36, placing the paraffin sample column sample preparation mold processed in step 35 in the middle position of the orientation fixture, so that the sample in the paraffin sample column sample preparation mold is at the center position of the extreme end of the orientation fixture; Step 37, respectively placing an electric heating rod and a temperature sensor into the heating hole and the temperature measuring hole of the paraffin sample column sample preparation mold, turning on the heating power switch of the electric heating rod for constant temperature heating until the mixture sample is completely softened; Step 38, turning on the orientation fixture switch to orient the mixture sample, removing the electric heating rod after a few minutes, and allowing the mixture sample to solidify in the magnetic field for 5 to 15 minutes; Step 39, after the paraffin in the mixture sample solidifies, the oriented paraffin sample column is taken out, and a pulsed magnetic field is used to magnetize the paraffin sample column to a saturated state, thereby obtaining a magnetic powder paraffin sample column.

4. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 3, characterized in that: In the step 31, the melting point of the low melting point paraffin is 48-52°C, and the heating temperature of the oven is 50-65°C; In the step 32, anisotropic rare earth permanent magnet powder is added into the heating container, and during the mixing process of the anisotropic rare earth permanent magnet powder and the low melting point paraffin, the heating container is placed in the oven, and the oven door is opened to perform the above operation; In the step 34, one side of the sample adding through hole of the paraffin sample column sample preparation mold is tightly sealed by a transparent tape; in the step 35, the other side of the sample adding through hole of the paraffin sample column sample preparation mold after filling is tightly sealed by a transparent tape; In step 37, the constant temperature heating time is 3 to 5 minutes; In step 39, the solidification time is 10 to 12 minutes.

5. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 3, characterized in that: The mold body of the paraffin sample column sample preparation mold is a plate-like structure, which is provided with a sample adding through hole, a heating hole is arranged on the periphery of the sample adding through hole, and a temperature measuring hole is arranged on the mold body on the side of the sample adding through hole.

6. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 5, characterized in that: There are two heating holes, which are divided into a first heating hole and a second heating hole. The first heating hole is arranged on the mold body above the sample adding through hole, and the second heating hole is arranged on the mold body below the sample adding through hole.

7. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 5, characterized in that: The mold body is made of a non-magnetic material plate.

8. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 7, characterized in that: The non-magnetic conductive material plate body is any one of bakelite plate, polytetrafluoroplastic plate and aluminum plate.

9. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 5, characterized in that: The thickness of the mold body is 7 mm, the diameter of the sample adding through hole on the mold body is φ9.5 mm to φ10 mm, and the thickness of the sample adding through hole is 7 mm.

10. The method for detecting magnetic properties of anisotropic rare earth permanent magnet powder according to claim 5, characterized in that: In the step 32 of making the paraffin-like column, the content of the low-melting-point paraffin in the mixture of the low-melting-point paraffin and the anisotropic rare earth permanent magnet powder is 10-30 wt%.

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