TWI636016B - Methods of fabricating modified iron oxide powder and fabricating ferrite magnet - Google Patents

Abstract

A method for producing modified iron oxide powder and ferrite magnet. The method for producing the modified iron oxide powder comprises the steps of: providing an unmodified iron oxide powder, wherein the unmodified iron oxide powder has an average particle diameter of between 0.05 and 0.08 micrometers, and the unmodified oxidation The ferrous ion of the iron powder is between 0.6 and 1.2% by weight; and a calcination step is carried out, and the unmodified iron oxide powder is held at a temperature between 790 and 850 ° C for 50 to 60 minutes. Between the modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of 0.16 to 0.35 micrometers, and the modified iron oxide powder has a ferrous ion system greater than 0 and less than or equal to 0.15 weight percent.

Description

Method for manufacturing modified iron oxide powder and ferrite magnet

The present invention relates to a method for producing iron oxide powder and a magnet, and more particularly to a method for producing a modified iron oxide powder and a ferrite magnet.

The ferrite magnets are mainly composed of a lanthanide ferrite (BaFe ₁₂ O ₁₉ ) system and a lanthanide ferrite (SrFe ₁₂ O ₁₉ ) system. Although the ferromagnetic magnet has lower magnetic properties than rare earth permanent magnets, such as NdFeB permanent magnet materials. However, since the main raw material of the ferrite magnet is iron oxide, the iron oxide can be derived from the waste acid recovery by-product of the cold rolling pickling plant of the steel sheet, and thus has the advantages of easy raw material acquisition and high cost performance. Until now, the ferrite magnet is still one of the magnets with high cost performance and large dosage.

The ferrite magnet is usually made of iron oxide (Fe ₂ O ₃ ) powder and sintered with other metal oxides such as strontium (Sr), barium (Ba) or calcium (Ca). Therefore, the iron oxide powder is the basic material for preparing the ferrite magnet.

In general, in the steel production process, it is usually necessary to remove the iron oxide on the surface of the steel through the acid between the hot rolling step and the cold rolling step. The iron oxide dissolved in the acid solution can be obtained through a process of recovery and purification (for example, by spray baking method; also known as Ruthner method), and further used as a base material of the permanent magnet ferrite magnet. However, the properties of the iron oxide powder obtained from the steel production process are difficult to predict, so if the iron oxide powder is used as a base material for preparing the ferrite magnet, the properties of the produced ferrite magnet are unstable. Or not good.

The Chinese mainland invention patent (Publication No.: CN103172387A) proposes a method of removing chloride ion (Cl ^- ) in the iron oxide powder produced by the Ruthner method by roasting in a manner of placing the iron oxide raw material at a temperature of 600 ± 10 ° C. The roasting kiln is baked for 50 to 60 minutes, and after cooling, the content of chloride ions in the iron red is sampled and then mixed with the strontium carbonate to prepare a ferrite magnet. However, even with this production method, the ferrite magnet produced is still insufficient in magnetic properties.

Therefore, it is necessary to provide a method for manufacturing modified iron oxide powder and ferrite magnet to solve the problems of the conventional technology.

An object of the present invention is to provide a method for producing a modified iron oxide powder which is subjected to a calcination step of unmodified iron oxide powder at a specific temperature for a specific period of time so that the average particle size of the modified iron oxide powder is reached. A specific range and a lower weight percentage of ferrous ions.

Another object of the present invention is to provide a method for producing a ferrite magnet, which is a modified iron oxide powder obtained by the method for producing a modified iron oxide powder, which is used as a main raw material of a ferrite magnet, and After the compound is mixed, a calcination step, a pulverization step, a magnetic field alignment step and a sintering step are performed to obtain the ferrite magnet, wherein the ferrite magnet has excellent magnetic properties.

In order to achieve the above object, the present invention provides a method for producing a modified iron oxide powder, comprising the steps of: providing an unmodified iron oxide powder, wherein an average particle diameter of the unmodified iron oxide powder is between 0.05 and Between 0.08 microns, and the ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2% by weight; and performing a calcination step, the unmodified iron oxide powder is between 790 and 850 ° C The temperature is maintained between 50 and 60 minutes to prepare a modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of 0.16 to 0.35 μm, and the modified iron oxide powder The ferrous ion system is greater than 0 and less than or equal to 0.15 weight percent.

In one embodiment of the invention, the unmodified iron oxide powder is produced by a spray roasting process.

In an embodiment of the invention, the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent.

In order to achieve the above object, the present invention provides a method for producing a ferrite magnet, comprising the steps of: providing an unmodified iron oxide powder, wherein the unmodified The average particle diameter of the iron oxide powder is between 0.05 and 0.08 micrometers, and the ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2 weight percent; performing a calcination step, The unmodified iron oxide powder is held at a temperature between 790 and 850 ° C for between 50 and 60 minutes; to obtain a modified iron oxide powder, wherein an average particle size of the modified iron oxide powder is Between 0.16 and 0.35 microns, and the ferrous ion of the modified iron oxide powder is greater than 0 and less than or equal to 0.15 weight percent; and a mixing step is performed, 85 to 95 parts by weight of the modified iron oxide powder and 5 Mixing to 15 parts by weight of a telluride to form a mixture; performing a calcination step, holding the mixture at a temperature between 1260 and 1300 ° C for between 50 and 70 minutes to form a pretreatment; Performing a pulverization step, pulverizing the pretreated material such that an average particle diameter of the pretreated material is between 0.65 and 0.7 μm; performing a magnetic field alignment step on the pulverized pretreated material to form a The embryo body; and performing a sintering step, the embryo body is between 1 The temperature between 220 and 1240 ° C is maintained for between 50 and 70 minutes to produce the ferrite magnet.

In one embodiment of the invention, the unmodified iron oxide powder is produced by a spray roasting process.

In an embodiment of the invention, the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent.

In an embodiment of the invention, the telluride comprises at least one of cesium carbonate and derivatives thereof.

In one embodiment of the invention, the halide has an average particle size between 2 and 3 microns.

In an embodiment of the invention, the magnetic field alignment step is performed by a magnetic field forming machine, wherein a magnetic field strength of the magnetic field alignment step is between 1.3 and 1.7 Tesla and a molding pressure system is between 3 and Between 4 tons / square meter.

In an embodiment of the invention, an oxygen content of an atmosphere in the calcining step is between 4% and 6%.

10‧‧‧ method

11~12‧‧‧Steps

20‧‧‧Method

21~27‧‧‧Steps

Fig. 1 is a flow chart showing a method for producing a modified iron oxide powder according to an embodiment of the present invention.

Fig. 2 is a flow chart showing a method of producing a ferrite magnet according to an embodiment of the present invention.

The above and other objects, features and advantages of the present invention will become more <RTIgt; Furthermore, the directional terms mentioned in the present invention, such as upper, lower, top, bottom, front, rear, left, right, inner, outer, side, surrounding, central, horizontal, horizontal, vertical, longitudinal, axial, Radial, uppermost or lowermost, etc., only refer to the direction of the additional schema. Therefore, the directional terminology used is for the purpose of illustration and understanding of the invention.

Referring to FIG. 1 , a method 10 for manufacturing a modified iron oxide powder according to an embodiment of the present invention mainly comprises the following steps 11 to 12: providing an unmodified iron oxide powder, wherein the unmodified iron oxide powder is The average particle size is between 0.05 and 0.08 microns, and the ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2 weight percent (step 11); and a calcination step is performed on the The modified iron oxide powder is maintained at a temperature between 790 and 850 ° C for between 50 and 60 minutes to prepare a modified iron oxide powder, wherein an average particle diameter of the modified iron oxide powder is between 0.16 to 0.35 μm, and the ferrous ion of the modified iron oxide powder is greater than 0 and less than or equal to 0.15 weight percent (step 12). The present invention will be described in detail below with reference to Fig. 1 for a detailed description of the implementation details of the above steps of an embodiment and the principles thereof.

The method 10 for manufacturing modified iron oxide powder according to an embodiment of the present invention is first performed in step 11 : providing an unmodified iron oxide powder, wherein an average particle diameter of the unmodified iron oxide powder is between 0.05 and 0.08 μm. The ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2 weight percent. In this step 11, the unmodified iron oxide powder is, for example, a by-product produced in a steel process. More specifically, the unmodified iron oxide powder may be obtained by a spray roasting method from an acid solution containing iron oxide, and the unmodified iron oxide powder usually contains inevitable impurities. Ions, such as ferrous ions, chloride ions, and/or other impurity ions.

The method for manufacturing the modified iron oxide powder according to an embodiment of the present invention is finally a step 12: performing a calcination step of holding the unmodified iron oxide powder at a temperature between 790 and 850 ° C for 50 to 60 Between the minutes to prepare a modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of 0.16 to 0.35 μm, and the modified iron oxide powder has a ferrous ion system greater than 0 and less than Equal to 0.15 weight percent. In this step 12, the calcination step refers to a temperature holding process that does not require a specific atmosphere protection in a general atmospheric environment. In one embodiment, the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent.

It is to be noted that the method 10 for modifying the modified iron oxide powder according to an embodiment of the present invention is to maintain the unmodified iron oxide powder at a specific temperature for a certain period of time so that the modified iron oxide powder has a specific average value. The particle size (which may also be referred to as the average particle size of the primary particles) and has a lower weight percentage of ferrous ions. More specifically, when the modified iron oxide powder has the above characteristics, it contributes to the production of a ferrite magnet having better magnetic properties. Detailed experimental results will be described in the following paragraphs.

Referring to FIG. 2, a method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention mainly comprises the following steps 21 to 27: providing an unmodified iron oxide powder, wherein an average of the unmodified iron oxide powder The particle size is between 0.05 and 0.08 micrometers, and the ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2 weight percent (step 21); performing a calcination step, the unmodified The iron oxide powder is maintained at a temperature between 790 and 850 ° C for between 50 and 60 minutes to produce a modified iron oxide powder, wherein the modified iron oxide powder has an average particle size of 0.16 to Between 0.35 microns, and the ferrous ion of the modified iron oxide powder is greater than 0 and less than or equal to 0.15 weight percent (step 22); performing a mixing step of 85 to 95 parts by weight of the modified iron oxide powder and 5 to 15 parts by weight of one of the tellurides is mixed to form a mixture (step 23); a calcination step is carried out, and the mixture is held at a temperature between 1260 and 1300 ° C for between 50 and 70 minutes to form a pretreatment (step 24); performing a pulverization step to pulverize the pretreated material, So that an average particle size of the pretreated material is between 0.65 and 0.7 microns (step 25); The pretreatment is subjected to a magnetic field alignment step to form an embryo body (step 26); and a sintering step is performed, and the embryo body is held at a temperature between 1220 and 1240 ° C for between 50 and 70 minutes. The ferrite magnet is produced (step 27). The present invention will be described in detail below with reference to Fig. 2 for details of the implementation of the above steps of an embodiment and the principles thereof.

The method for manufacturing a ferrite magnet according to an embodiment of the present invention is first performed in step 21: providing an unmodified iron oxide powder, wherein an average particle diameter of the unmodified iron oxide powder is between 0.05 and 0.08 μm. And the ferrous ion of the unmodified iron oxide powder is between 0.6 and 1.2 weight percent. In this step 21, the unmodified iron oxide powder is, for example, a by-product produced in a steel process. More specifically, the unmodified iron oxide powder may be obtained by a spray roasting method from an acid solution containing iron oxide, and the unmodified iron oxide powder usually contains unavoidable impurity ions such as ferrous ions. , chloride ions and / or other impurity ions.

The method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention is followed by the step 22: performing a calcination step of holding the unmodified iron oxide powder at a temperature between 790 and 850 ° C for 50 to 60 minutes. Between the modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of 0.16 to 0.35 micrometers, and the modified iron oxide powder has a ferrous ion system greater than 0 and less than or equal to 0.15 weight percent. In this step 22, the calcination step refers to a temperature holding process that does not require a specific atmosphere protection in a general atmospheric environment. In one embodiment, the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent.

The method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention is followed by the step 23: performing a mixing step of mixing 85 to 95 parts by weight of the modified iron oxide powder with 5 to 15 parts by weight of one of the tellurides. To form a mixture. In this step 23, the telluride may comprise at least one of cesium carbonate and its derivatives. In one embodiment, the halide has an average particle size between 2 and 3 microns. It should be mentioned here that in the case where the average particle size of the telluride is between 2 and 3 microns, compared to the unmodified iron oxide powder (average particle size between 0.05 and 0.08 microns) The modified iron oxide powder (having an average particle diameter of between 0.16 and 0.35 micrometers) and the bismuth compound There are fewer size gaps, so that the pre-processed material formed in the calcination step can have a more uniform distribution of grain size, and the formed grain size is not too large or too small, so that the finally produced ferrite The body magnet has better magnetic properties.

The method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention is followed by step 24: performing a calcination step of holding the mixture at a temperature between 1260 and 1300 ° C for between 50 and 70 minutes to form a former Treatment. In this step 24, the calcining step is mainly to mutually diffuse various components at a high temperature to form a stable phase. In one embodiment, an oxygen content of an atmosphere of the calcining step may be between 4% and 6%.

The method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention is followed by a step 25 of performing a pulverization step of pulverizing the pretreated material so that an average particle diameter of the pretreated material is between 0.65 and 0.7 μm. between. In this step 25, the pulverization step can be carried out, for example, by cooling the pretreated material after the calcination step to below 90 ° C, and coarsely passing through a pulverizer (Roller Mill) equipped with a cyclone collector. After pulverization, the coarsely pulverized powder has a narrow unimodal particle size distribution of 2.6±0.1 μm; thereafter, wet pulverization is carried out, and wet milling is performed by a ball mill (Ball Mill) at a weight ratio of 1:12. After 32 hours, a narrow unimodal particle size distribution having an average particle diameter of between 0.65 and 0.7 microns is obtained, wherein the steel ball is, for example, a 3/16 inch diameter chromium-free bearing steel ball. In one embodiment, when wet fine pulverization is carried out, trace additives such as Co ₃ O ₄ , CaCO ₃ , SiO ₂ and SrCO ₃ may be added.

The method 20 for manufacturing a ferrite magnet according to an embodiment of the present invention is followed by a step 26 of performing a magnetic field alignment step on the pulverized pretreated material to form an embryo body. In this step 26, the magnetic field alignment step is performed, for example, by a magnetic field forming machine, wherein the alignment magnetic field strength of the magnetic field alignment step is between 1.3 and 1.7 Tesla and the molding pressure system is between 3 and 4 tons. /m square between.

The method for manufacturing a ferrite magnet according to an embodiment of the present invention is finally a step 27: performing a sintering step of holding the body at a temperature between 1220 and 1240 ° C for between 50 and 70 minutes. The ferrite magnet is produced.

It is to be noted that the manufacture of a ferrite magnet according to an embodiment of the present invention The method 20 is a main material using a modified iron oxide powder (for example, the method for producing modified iron oxide powder according to an embodiment of the present invention), and is mixed with a telluride, followed by a calcination step, a pulverization step, and a magnetic field alignment step. And a sintering step to produce the ferrite magnet, wherein the ferrite magnet has excellent magnetic properties. More specifically, at least one reason why the ferrite magnet has excellent magnetic properties is due to the use of the modified iron oxide powder. Furthermore, at least another reason for the ferrite magnet to have excellent magnetic properties is due to the use of various steps having specific parameters.

Hereinafter, several examples and comparative examples will be described to explain the modified iron oxide powder obtained by the method for producing modified iron oxide powder according to an embodiment of the present invention as a main raw material, which can improve the magnetic properties of the ferrite magnet. .

Example 1

Providing unmodified iron oxide powder having a ferrous iron (Fe ²⁺ ) content of about 0.6 wt%, a chloride ion (Cl ^- ) content of about 0.1 wt%, and an average particle diameter of primary particles of between about 0.05 and 0.08 μm) . The unmodified iron oxide powder was subjected to a calcination step at about 800 ° C for 50 minutes to obtain a modified iron oxide powder.

The modified iron oxide powder was subjected to the mixing step, the calcining step, the pulverizing step, the magnetic field aligning step and the sintering step described in the examples of the present invention to obtain the ferrite magnet of Example 1.

Examples 2 to 4 and Comparative Examples 1 to 5

The method for producing the ferrite magnets of Examples 2 to 4 and Comparative Examples 1 to 5 was substantially the same as that of Example 1. The only difference is that the iron oxide powder used may not be modified (for example, Comparative Examples 1, 2 and 5), the temperature used in the baking step is different (Examples 1 to 4 and Comparative Examples 3 and 4), calcination. The oxygen content used in the step is different (for example, 8% in Comparative Example 2 and 5% in the other). On the other hand, the additives in Example 4 and Comparative Example 5 additionally contained a lanthanoid compound so as to conform to the determination of the ferrite magnet component standard of the FB9 series (Japan TDK Corporation product standard); and Examples 1 to 3 In comparison with Comparative Examples 1 to 4, the lanthanoid compound was not added so as to conform to the determination of the ferrite magnet component standard of the FB6 series (Japan TDK Corporation product standard). The parameters of the respective examples and comparative examples are listed in Table 1 below.

Next, the analysis and comparison were carried out, and the ferrite magnets obtained in the respective examples and comparative examples were subjected to JIS (Japanese Industrial Standard) C2501 and C2502 standards, and passed through instruments (for example, BN Loop Tracer of NIM-2000 type of China Institute of Metrology). Measurements of magnetic properties such as residual magnetization (Br), coercive force ( _b H _c ), intrinsic coercive force ( _i H _c ), and maximum magnetic energy product ((BH) _max ) were performed. Please refer to Table 2 below for the results after the test.

As can be seen from Table 2 above, for the product classification of FB6, Examples 1 to 3 have excellent magnetic properties, such as a residual magnetization greater than 4400 G, a coercive force greater than 3130 Oe, and an intrinsic coercive force greater than 3200 Oe, and The maximum magnetic energy product is greater than or equal to 4.50 MGOe. Among them, Comparative Example 2 has magnetic properties close to those of Examples 1 to 3, but this is because Comparative Example 2 has an oxygen content of 8% used in the calcination step, and this method will increase a large amount of iron oxide production. The cost of body magnets. On the other hand, for the product classification of FB9, the respective magnetic characteristics of Example 4 were significantly higher than those of Comparative Example 5.

Further, the specifications of the product classification for FB6 for magnetic characteristics are as follows: Br = 4400 ± 100 G, _b H _c = 3250 ± 150 Oe, _i H _c = 3300 ± 150 Oe, and (BH) _max = 4.6 ± 0.2 MGOe. The specifications of the FB9 product classification for magnetic properties are as follows: Br = 4500 ± 100 G, _b H _c = 4300 ± 150 Oe, _i H _c = 4500 ± 150 Oe, and (BH) _max = 4.9 ± 0.2 MGOe. However, it should be mentioned that although each magnetic property defines a range value, in reality, the higher the value of the magnetic property, the better. It can be seen that the ferrite magnets of Examples 1 to 4 not only conform to the specification of the above-mentioned product classification for magnetic properties, but also exceed the specified range standard among several magnetic properties, and more clearly show the ferrite of an embodiment of the present invention. The ferrite magnet produced by the method for producing a magnet is excellent.

In addition, it is worth mentioning that the weight percentage of ferrous ions in each comparative example is relatively high. Generally, if the weight percentage of ferrous ions is high, the magnetic properties of ferrite magnets produced by using similar processes are not good ( Unless other process parameters are changed, for example, Comparative Example 2 changes the oxygen content of the calcination step). Yet at least one object of the present invention is to reduce the weight percentage of ferrous ions of iron oxide as a main component to improve the magnetic properties of the ferrite magnet. To improve the weight percentage of ferrous ions of iron oxide, it is necessary to maintain a temperature of 750 to 850 ° C for 50 to 60 minutes to produce this effect. However, it is mentioned that holding the temperature at 790 to 850 ° C for 50 to 60 minutes may also have the effect of lowering the weight percentage of chloride ions of iron oxide.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (10)

A method for producing a modified iron oxide powder, comprising the steps of: providing an unmodified iron oxide powder, wherein an average particle diameter of the unmodified iron oxide powder is between 0.05 and 0.08 micrometers, and the unmodified The iron oxide powder of the iron oxide powder is between 0.6 and 1.2 weight percent; and a calcination step is carried out, and the unmodified iron oxide powder is maintained at a temperature of between 790 and 850 ° C for 50 to Between 60 minutes to prepare a modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of 0.16 to 0.35 μm, and the modified iron oxide powder has a ferrous ion system greater than 0 and Less than or equal to 0.15 weight percent. The method for producing a modified iron oxide powder according to claim 1, wherein the unmodified iron oxide powder is obtained by a spray roasting method. The method for producing a modified iron oxide powder according to claim 1, wherein the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent. A method for producing a ferrite magnet, comprising the steps of: providing an unmodified iron oxide powder, wherein an average particle diameter of the unmodified iron oxide powder is between 0.05 and 0.08 μm, and the unmodified The ferrous ion of the iron oxide powder is between 0.6 and 1.2% by weight; performing a calcination step, maintaining the temperature of the unmodified iron oxide powder at a temperature between 790 and 850 ° C for 50 to 60 minutes Between the preparation of a modified iron oxide powder, wherein the modified iron oxide powder has an average particle diameter of between 0.16 and 0.35 micrometers, and the modified iron oxide powder has a ferrous ion system greater than 0 and Less than or equal to 0.15 weight percent; Performing a mixing step of mixing 85 to 95 parts by weight of the modified iron oxide powder with 5 to 15 parts by weight of one of the tellurides to form a mixture; performing a calcination step, the mixture is at 1260 to 1300 ° C The temperature is maintained between 50 and 70 minutes to form a pretreatment; a pulverization step is performed, and the pretreated material is pulverized so that an average particle diameter of the pretreatment is between 0.65 and 0.7 microns. Performing a magnetic field alignment step on the pulverized pretreated material to form an embryo body; and performing a sintering step of holding the embryo body at a temperature between 1220 and 1240 ° C for 50 to 70 Between the minutes to make the ferrite magnet. The method for producing a ferrite magnet according to claim 4, wherein the unmodified iron oxide powder is obtained by a spray baking method. The method for producing a ferrite magnet according to claim 4, wherein the modified iron oxide powder has a monochlorinated ion system greater than zero and less than or equal to 0.01 weight percent. The method for producing a ferrite magnet according to the fourth aspect of the invention, wherein the telluride comprises at least one of cesium carbonate and a derivative thereof. The method for producing a ferrite magnet according to claim 4, wherein an average particle diameter of the telluride is between 2 and 3 μm. The method for manufacturing a ferrite magnet according to claim 4, wherein the magnetic field alignment step is performed by a magnetic field forming machine, wherein a magnetic field strength of the magnetic field alignment step is between 1.3 and 1.7 Tesla. The molding pressure is between 3 and 4 tons per square meter. A method for producing a ferrite magnet according to claim 4, wherein An oxygen content in an atmosphere of the calcination step is between 4% and 6%.