JPH024535B2 - - Google Patents

Description

[Detailed description of the invention]

Iron oxide, which is normally used in pigments and ferrite magnetic materials, is made by heat-treating iron sulfate, iron chloride, mill scale, etc., but it is made into hydroxide by pouring an alkali into an iron ion solution, and then It is supplied by roasting or by roasting pyrite to produce iron oxide. Among these iron oxides, mill scale obtained by roasting, oxidizing, and pulverizing has good powder characteristics with high density, but the grain shape is irregular and the activity is slightly low. Therefore, it is necessary to make the grain size as small as possible. However, it is difficult to crush dense and hard materials to particle sizes of 1μ or less. Also,
Iron oxide obtained by decomposing iron sulfate and iron chloride is often disadvantageous in use unless it is sufficiently deoxidized and its powder characteristics are adjusted. for example,
Remaining acid radicals react with additives and cause ferrite conversion or composition changes, and unsuitable powder properties can cause cracks to occur during powder molding, shrinkage ratio to deviate from the appropriate value, and a decrease in molded density. , defects such as a decrease in mechanical strength occur. Therefore, products that are stabilized by adjusting according to certain standards are supplied to the market. in this way,
Although there are a wide variety of sources for supplying iron oxide, the shape of the powder of this normal iron oxide is often amorphous, and there is also a needle-shaped powder for magnetic recording. Further, for use in ferrite using ordinary iron oxide, particularly for use in Ba, Sr, and La magnets, 1 mol % of barium carbonate is mixed with about 5 to 6 mol % of iron oxide. This mixing method may be either wet or dry, but if intimate mixing is required, the wet method yields preferable results. Next, when this mixture is heated, it becomes a hexagonal ferromagnetic material for the first time. The crystal axis direction of this magnetic material has no regularity and is so-called isotropic. Even if this mixed powder is temporarily formed in a magnetic field before calcination, the applied magnetic field has almost no effect and is not oriented. Here, the present inventors have developed a product in which the primary particles of iron oxide powder have an almost hexagonal crystal structure or cleavage plane, and have weak ferromagnetism, thereby increasing the activity. This method succeeded in obtaining high iron oxide. Therefore, in the production method of the present invention, first, Ca, Mg, Be, Cd,
Component oxides such as Co, Cr, Cu, Mn, Zn, S etc.
0.02% to 6% (If the component oxide is less than 0.02%, the effect is small, so it is set to 0.02% or more, and if it exceeds 6%, the activity decreases and the final product loses its magnetic properties, so it was set to 6% or less. ), if there is a large amount, mix at 10% or less. These oxides may be one type or a mixture of two or more types, but the total amount does not exceed 10% (if the total amount exceeds 10%, it will be difficult to create a distinctive magnetic material) Therefore, it should be 10% or less.) Furthermore, as group B, SiO ₂ 0.05% to 10% (SiO ₂ does not increase the sintered density if it is less than 0.1%, so it should be 0.1% or more,
If it exceeds 6%, the magnetic properties will deteriorate, so it is set to 6% or less. ), Al ₂ O ₃ 0.1 to 4% (Al ₂ O ₃ has little effect on increasing coercive force if it is less than 0.1%, so it should be made to be 0.1% or more, and if it exceeds 4%, the magnetic flux density will decrease, so
It was set at 4%. ) and mix them well.
This mixed powder is used as a matrix, and the hexagonal oxide that is the seed crystal for crystal formation is PbFe _7.5 Mn _3.5 Al _0.5
Ti _0.5 O ₁₉ or M ²⁺ O・6Fe ₂ O ₃ (here M ²⁺ is Ba,
Indicates Sr, Pb, and Ca. ) is added. The amount of hexagonal seed oxide added may be large, but if it is less than 0.5%, the effect on crystallization into a hexagonal system will be small, so it should be 0.5% or more, and the maximum is 4% or less.
Regarding ferromagnetic zinc namarate, it was set at 0.5% or more for the same reason as mentioned above, but Ba, Sr, Pb, Ca,
In order to express the unique characteristics of each metal ion, or for versatility, we want to keep it below 10%. M ²⁺ O・6Fe ₂ O ₃ in each oxide explained above is
It has a hexagonal crystal structure and exhibits ferromagnetism. Generally these are ferromagnetic namalites (magnet
plumbite (magnetic plumbite). By calcining the mixture of the components required by Groups A and B and the seed crystal oxide as described above, highly active iron oxide can be obtained according to the present invention. Next, regarding the limits of the amount of each of the above additive components, if the amount of Group A additives is increased to 10% or more, various hybrids with hexagonal, trigonal, equiaxed crystal system, and other magnetic properties will be generated. more likely to form. and,
Depending on the combination of additives and the selection of their amounts, the properties of the resulting material vary significantly, which poses a problem when applied to other ferrites. Also,
If the amount added is 0.02% or less, the effect of the crystal structure will be reduced, so the lower limit was set. The additives of group A or group B added to iron oxide can be freely selected and combined, and the amount added is adjusted by the seed crystal oxide. For example, SiO ₂ contained in the seed crystal oxide or TiO for these,
Large amount of Al ₂ O ₃ or divalent metal M ²⁺ for these. Furthermore, when the total content of iron oxides added to these is large, the amount of group A or group B additives is reduced, and the total content may be reduced to 0.02%, and when it is a small amount, it is 6%. % and mix accordingly. This ratio is a rough value and does not need to be strictly regulated. The mixed powder prepared with the above precautions may be granulated and calcined as it is, but more preferable results can be obtained if the powder is preformed and calcined while being oriented in a magnetic field. In the wet method, a mixed powder is made into a slurry, compressed and dehydrated in a magnetic field, and then calcined into a lump of an appropriate shape. In the wet preparation method, as is generally known, an alkali is added to the iron ion solution and the additive component ion solution to neutralize the solution, followed by filtration and washing with water. If this water washing is insufficient, for example, SO ₄ ions and BaCO ₃ will react, and BaSO ₄
Since this deteriorates the magnetic properties, the material is thoroughly washed with water, and a seed crystal oxide is added and mixed therein. This mixture is compressed and dehydrated in a magnetic field and then calcined to prepare the mixture. here,
The raw materials used include Cr ₂ O ₃ , As ₂ O ₃ , PbO, CdO,
It may contain MnO, NiO _2, etc., but care must be taken to make these substances insoluble and to prevent them from scattering as gas during calcination and final firing. Furthermore, the treatment of polishing powder and cleaning liquid after sintering also needs to be adequately controlled. Next, the reaction process is shown. The heating temperature is from around 700°C to 1450°C. At low heating temperatures, it is necessary to increase the heating time, and at high heating temperatures, crystals grow in a short time. However, above 1450°C, more FeO is produced, so this was set as the limit. However, in the wet method, the firing temperature on the high-temperature side is 1200
°C is sufficient. Further, when a large amount of seed crystal oxide is added, a relatively low heating temperature may be used, but a high heating temperature will require only a short time. However, when the amount of seed crystal oxide added is small, it is necessary to increase the heating time at a low temperature. If heated at high temperature,
There is a risk that the remaining iron oxide portion may grow into a hexagonal crystal due to the seed crystal oxide, or may be sintered as it is while the hexagonal crystal is matured. The pulverization is preferably carried out using a commonly used pulverizer, preferably using a pulverization method mainly based on impact action. This is to make it easier to cleave, increase the activity of the cleavage plane, and also serve to protect it. Therefore, it is recommended to install a classifier to prevent deterioration of activity and particle size distribution due to over-pulverization. Regarding the particle size, for ordinary iron oxide, particles of about 1 μm or less are used, but when the activated iron oxide of the present invention is used as a ferrite raw material, excellent properties can be obtained even with a particle size of 2 to 4 μm. can be obtained, and the added elements are sufficiently diffused into iron oxide to form ferrite. This is recognized to be a phenomenon that occurs because the iron oxide particles basically have a hexagonal crystal structure, and their activity increases when they are split from the cleavage plane of the crystal. When this granular material is further crushed into fine powder, the particle shape changes from plate-like to what appears to be irregularly shaped particles.
Basically, it is a fine powder with cleavage planes. As mentioned above, the prepared iron oxide of the present invention contains many substances that are generally considered to be impurities, but these components cause the crystallization of the substances during the reaction process. It is thought that iron oxides are useful and may precipitate during the cooling process, and even if they exist as excess components or impurities, the present iron oxides have a predominant activity and suppress the toxic effects of impurities, so they are not treated as impurities. I don't see it. This shows that there is no need to make the composition strict, which is industrially convenient. Next, we will discuss the production of calcined magnetic material.
The calcined magnetic material is calcined by mixing the present iron oxide and the main component and calcining the mixture as it is or by pressurizing it, or by pressurizing it in a magnetic field, and this step may be performed by a generally known method. First, this iron oxide and carbonates such as Ba, Sr, and La are mixed at a ratio of 5.0 to 6.0 to 1 mole, and heated to 1050 to 1200°C for isotropic materials and 1100 to 1100°C for anisotropic materials.
Heat at a temperature of 1300℃. For this isotropic calcined product, it is adjusted to about 2μ, and for anisotropic, it is adjusted to about 0.6μ. The particle size of the former isotropic magnetic powder is abnormally large compared to 0.5 to 1μ of normal ferrite raw material powder,
Powder fluidity, mold filling rate, moldability, etc. are good. Furthermore, although the sintering temperature is lower than that of general materials, it has a high density, and
Good characteristics. Furthermore, the shrinkage ratio during sintering is generally 15%, but the shrinkage ratio of the present invention is 10%, which is quite low. This has the advantage of increasing the amount of filling into the firing furnace and improving the accuracy of dimensions after firing. If an existing mold is used, if the particle size of this ferromagnetic powder is reduced from 2μ to around 1μ, the optimal sintering temperature will further drop to around 1180℃, and the shrinkage rate will increase. It shows a value of about 14 to 17%, the sintered density is similarly high, and the magnetic properties are good. These noteworthy features are extremely advantageous in terms of manufacturing technology.
Furthermore, even if the sum of both groups A and B of the components contained in iron oxide is the minimum value as shown below,
It should be noted that since it has the desired crystal structure and the feature of being a weak ferromagnetic material, it has a magnetic field orientation effect. That is, both iron oxide according to the present invention and ordinary iron oxide were prepared, BaCO ₃ and SiO ₂ were added to them, and after mixing, both were formed in a magnetic field and then fired. As a result, the calcination process is omitted. The composition of the iron oxide according to this invention is as follows, and the magnetism of this iron oxide was 0.8 emu. SiO ₂ 0.4, Al ₂ C ₃ 0.5, CaO 0.05, CoO 0,
MgO 0.03, MnO 0.02, TiO ₂ 0.04, Fe ₂ O ₃ Bal The table below shows a comparison of magnetic materials made using this iron oxide and iron oxide, a by-product of pickling steel.

[Table] As shown in the table above, there are slight differences in the diameter and height of this product, which represent the characteristics of this product. As described, the iron oxide obtained by this invention is
It has a variety of features not found in conventional products. Next, examples of this invention will be shown. Example 1 FeO ₃ 96%, CaCO ₃ 1%, SiO ₂ 1%,
BaCO ₃ 1% and Al ₂ O ₃ 1% are mixed closely, and BaO, a hexagonal crystal substance, is added as a seed crystal oxide.
5.2 Mix 30% by volume of Fe ₂ O ₃ powder, make it into a pellet, heat it to 1100℃, cool it, and then crush it with an atomizer to make hexagonal iron oxide. This is called Θiron oxide (ΘFe ₂ O ₃ ). When applying this Θ iron oxide powder to barium magnet production, ΘFe ₂ O ₃ 89.5%, BaCO ₃ 10%, CaCO ₃
0.5% is intimately mixed, calcined, and then ground into a powder of approximately 0.9μ, compacted in a magnetic field, and fired at 1240°C. The characteristics of this product are as follows.

[Table] In the above, the large difference in characteristics is the Θ of the present invention.
This is because iron oxide already has ferromagnetism and is highly dense. Example 2 Fe ₂ O ₃ 95.5%, SiO ₂ 0.2%, MnO 0.1%,
To a substance containing 0.1% MgO and 0.1% Al ₂ O ₃ , 50% fine powder of seed crystal oxide is added and mixed closely, heated at 1100°C, cooled, and pulverized to a particle size of 2μ or less. to this,
20% BaCO ₃ is added and mixed, calcined and pulverized, filled into a mold of the desired shape, formed under pressure, and then heated to 1180°C and allowed to cool. The characteristics of this product are as follows.

[Table] Example 3 Fe ₂ O ₃ 98.2%, SrCO ₃ 1%, CaCO ₃ 0.5%,
For 80% of the total of SiO ₂ 0.2% and Al ₂ O ₃ 0.1%,
Added 20% SrO・5.4Fe ₂ O ₃ powder and heated at 1200℃ for 20
After heating for several minutes and cooling, it is crushed to obtain Θ iron oxide powder. Strontium magnets using the above Θ iron oxide are made by adding 15% SrCO ₃ and 0.3% SiO ₂ to Θ iron oxide, mixing well and solidifying it into an appropriate shape, heating it at 1100°C, and cooling it to a size of 2μ or less. The powder is crushed to a particle size of , compression molded in the required mold, and sintered at 1200℃. The characteristics of this product are as follows.

【table】

Claims (1)

[Claims] 1 Mainly composed of iron oxide, with respect to the iron oxide, Ca,
Mg, Ti, Ni, Cd, Mn, Co, Cr, Cu, Zn, S
and Be oxide, or one or more substances that become oxides when heated, such as BaCO ₃ and SrCO ₃ , in weight ratio.
0.02% _~ 6%, _SiO2 0.1%~10% and _Al2O3
A mixture containing 0.1% to 4% of hexagonal seed oxide, ferromagnetic namalite, or a mixture of both at a weight ratio of 0.5% to 50% was heated at 700°C. A method for producing magnetic ore powder having a hexagonal crystal structure with cleavage planes, which comprises heating to a temperature range of ~1450°C, cooling, and pulverizing it by impact action.