JPS6018134B2 - Method for manufacturing oxidized metal magnetic core material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal oxide core material having high electrical resistance and magnetic properties, and particularly to a method for manufacturing a nickel-zinc ferrite magnetic core material using a hot isostatic pressure bonding process. This relates to a manufacturing method.

Ferrite burnt stripes have come into widespread use as magnetic head cores or memory element materials for electronic computers, magnetic head core materials for tape recorders, and core materials for various communication devices, and their magnetic properties have also been significantly improved. ing.

However, ferrite crystals generally have a problem in that they lack mechanical strength and are brittle materials. For this reason, we focused on the fact that mechanical strength is related to the densification of crystal grains, and
It has been proposed to improve the mechanical strength to some extent by increasing the density by hot press compaction or hot isostatic press compaction (for example, see publications such as Tokusekki No. 49-128296); however, Mechanical strength varies due to differences in crystal grains depending on the material and precipitation of a second phase due to annealing treatment at a temperature higher than the hot isostatic pressing temperature, so metal oxide magnetic cores still have sufficient mechanical strength. Materials, especially nickel-zinc ferrite materials, have not been obtained. Therefore, these materials can be used, for example, in the magnetic heads of electronic computers or tape recorders.
When this is applied, problems arise such as wear and tear due to contact between the magnetic head and the magnetic disk or contact with the magnetic tape, which shortens the life of the magnetic head. When used as a memory element in an electronic computer, a memory plane is manufactured by arranging ring-shaped ferrite cores in rows and columns, and weaving the cores through read and write conductors through the center of the arranged cores. The above-mentioned core weaving work is usually done by hand, and the above-mentioned conductive wire is inserted into each core one by one, so if the strength of the core is weak, even a slight external force applied during the work can cause the core to break. There is a problem that the yield rate decreases. In other words, although it has recently become desirable to make the core shape as small as possible in order to increase storage density and improve information processing speed, the shape of the core is limited due to the inherent strength of the material. The drawback is that it is limited to a certain size. Therefore, if it is possible to obtain ferrite made of a material with high mechanical strength, it will inevitably be possible to downsize the core shape, thereby reducing the power consumption required to drive electronic devices. At the same time, the information processing capacity of the device in which the core is used can be increased, and the processing speed can be further improved. As mentioned above, core strength is extremely important in the production of ferrite because ferrite with high core strength can be used in a wider range of fields such as electronic computers and communication equipment, and therefore has superior mechanical strength. The emergence of metal oxide magnetic core materials was desired.

In particular, nickel-zinc ferrite material, which has high density, high electrical resistance and magnetic properties, is a material with good high frequency properties as is well known, so if its core strength increases, it will become a magnetic core head material with even better properties. Since it is something that can be obtained, its realization is desired. The present invention was made as a result of intensive studies to improve the drawbacks of the conventional metal oxide-rich materials mentioned above, and is a nickel-lead-based ferrite material by adding an appropriate amount of manganese oxide and bonding by hot isostatic pressure. This makes the crystal grains uniform and finer, and also prevents the precipitation of the second phase, which is thought to cause crystal grains to fall off and have a significant negative impact on mechanical strength, resulting in high density with extremely high core strength. This is a manufacturing method characterized by obtaining a magnetic core.

That is, in the production method of the present invention, the main component is nickel oxide 10-25%, zinc oxide 15-40%, and ferric oxide 45-60% in molar ratio, and manganese oxide 0.0% as a subcomponent in weight ratio. 001 to 3.0%, and after pressure molding the mixture into a desired shape, 12
Primary sintering is carried out at below 0 pi○, followed by hot isostatic sintering at 500 to 200 hydrophobic pressure and 1000 to 1250 qo, and then in oxygen or air and at a temperature below the hot isostatic pressing temperature. It is characterized by heat treatment.

In the present invention having such a structure, the raw material components are usually blended to have the above composition, and after thoroughly mixing the mixture using a ball mill, roll mill, etc., which also serves as pulverization,
This mixture is pre-swept at 800 DEG -1100 DEG C. for at least 3 microminutes in an oxygen-containing atmosphere.

Next, the preliminary dawn compacts are thoroughly mixed using a pole mill or a roll mill, etc., which also serves as pulverization.
This mixture is pressure molded into the desired shape. This molded body is phosphorized in oxygen or air at a temperature of 1200 oo or less for at least 30 minutes as a first scaling process to remove the precipitation of the second phase mainly composed of zinc or nickel, and then 500 at a temperature of 1000 to 125℃ as the dawning process.
Hot isostatic sintering is performed under conditions of ~200 atmospheric pressure, and as a final step, heat treatment is performed at a temperature below the hot isostatic sintering temperature at which grain growth and second phase precipitation occur. By applying this method, it is possible to obtain a nickel-zinc ferrite composite having a crystal grain size of 20 μm or less and a competitive density of approximately 100%. Generally, oxides are used as the raw material components, but in the present invention, they are not necessarily limited to oxides, and instead of oxides, other materials that can be easily converted into oxides during firing, such as carbonates. Compounds such as nitrates, sulfates, or tathates may also be used.

The present invention will be described in detail with reference to the drawings below, but before that, a brief explanation of how to display the core strength will be given. This was determined by actually measuring the occurrence of chips, scratches, etc. over time.

FIG. 1 is a characteristic curve showing the core strength (life) when a magnetic head using a nickel-zinc ferrite core obtained according to the present invention is slid against a magnetic disk.
In the figure, curve 1 shows that after preventing the precipitation of the second phase in the first competitive mackerel, hot water purification is performed and
Curve 2 is an example of a comparative product in which heat treatment was performed in air for 5 hours according to the method of the present invention.

Further, curve 3 is an example of a comparative product when the powder was pre-condensed in air according to the usual powder method. That is, the composition in the above drawing consists of 18% nickel oxide, 32% zinc oxide, 50% ferrous oxide, and manganese oxide by weight.
The mixture with 0.5% added was prephosphorized in air at 800 qo for about 60 minutes, and the pre-sintered stripes were finely ground and mixed, then pressure molded into the desired shape, and the primary scale was heated to 1150°C.
The mixture was phosphorized for 120 minutes.

Next, as a second scale, hot isostatic pressurization was performed at 112 mm for about 1 hour in argon gas under the condition of 100 hydrophobic pressure, and finally the sample was subjected to hot isostatic pressurization. At a temperature that is almost the same as that of the grains and at which the second phase does not precipitate, that is, 1 in air.
It was obtained by heat treatment at 100°C for 5 hours. In this case, the crystal grain size was 7 mm, and the adjacency density was approximately 100%. As is clear from a comparison of the above curves, there is a significant difference in core strength between the core strength of the core that has been subjected to hot isostatic sintering with the addition of manganese oxide and the core strength that has been heat treated after hot isostatic sintering according to the present invention. Therefore, the hot isostatically processed product of the present invention (curve 1) can withstand much longer use than the hot isostatically processed product (curve 2), and is extremely durable. It has high strength.

In other words, the core strength is improved by about 4 times compared to a comparative product that is hot isostatically formed. Therefore, even if manganese is added, unless heat treatment is performed after hot isostatic pressure compaction, the strength of the core will not be improved and the desired core strength cannot be expected. On the other hand, as the amount of manganese added increases, the core strength of curve 3 when phosphorized in air according to the normal powder method increases compared to curve 2 where no heat treatment is performed after hot isostatic pressing. The strength increases rapidly and reaches a maximum at 0.3-0.8%, and above that the effect gradually decreases, but it does not reach the strength of curve 1 according to the invention. Although the strength of the core obtained by the present invention shown by curve 1 can be improved even without the addition of manganese, practically it is desirable to add about 0.001 to 3.0% of manganese. From this point of view, the effective amount of manganese oxide added in the present invention is 0.001 to 3. % by weight. Introducing an appropriate amount of these additives can improve the mechanical strength of the material without adversely affecting the inherent magnetic properties of ferrite. The core strength is related not only to the interaction due to the addition of manganese, but also to the interaction between the sintering atmosphere and zinc oxide or nickel oxide, and it is effective to use zinc oxide in an amount of at least 10 mol % or more and 45 mol % or less. If the sintering temperature is 1200 oo or higher and the sintering atmosphere is neutral or reducing, a second phase mainly composed of zinc oxide or nickel oxide will precipitate depending on the composition, regardless of whether manganese is added, and this sample will be neutralized. Alternatively, hot isostatic pressure competition in a reducing atmosphere may further increase the amount of second phase precipitated.

Precipitation of the second phase can be removed to some extent by treatment in an air or oxygen atmosphere, but even if the precipitated second phase is diffused into the ferrite matrix to form a single-phase structure, the grain boundary area is not affected by solvent dissolution. The core strength is weak due to the difference in concentration, and the mechanical strength that is the objective of the present invention cannot necessarily be achieved. Figure 2 is a diagram showing the surface condition showing traces of a pressed sample of the material obtained according to the present invention when 0.5% by weight of manganese oxide was added and heat treated after hot isostatic pressing. FIG. 2 is a diagram showing the surface state when no heat treatment is performed after hot isostatic pressurization.

FIG. 2 shows an example in which the effects of the present invention are exhibited by heat treatment, and FIG. 3 shows an example in which the mechanical strength of the material deteriorates when heat treatment is not performed after hot isostatic pressure bonding. In other words, according to the traces of the straining test shown in Figure 3, if the hot isostatic pressure is applied as is, the grain boundaries become extremely weak as shown by arrow 1, which makes it easier for the grains to fall off. It was confirmed that the strength of the material was significantly reduced (arrow 2). Furthermore, if the second phase is precipitated, the hardness of the second phase is lower than that of the ferrite matrix, so even if heat treated, it easily falls off, which is also a major cause of a decrease in strength. The reason why excellent mechanical strength is obtained by combining the simultaneous addition of manganese oxide, hot isostatic sintering, and heat treatment is that, as mentioned above, the removal of the second phase precipitate, which has a different mechanical strength from the ferrite matrix, and The effect of hot isostatic compression is to densify the crystal structure and suppress grain growth.

Therefore, the high core strength according to the present invention is achieved by nickel-
Ferrite is mainly composed of zinc and is obtained by combining the addition of manganese oxide with hot isostatic pressing and hot treatment, and as mentioned above, the amount of manganese oxide added is 0.001 to 3.0%. The range is effective and the desired high core strength can be obtained.

If the manganese oxide content is less than 0.001%, the effect of the addition of both will be minimal; on the other hand, if the manganese oxide content exceeds 3.0%, the core strength will deteriorate, and the effect of the addition will become difficult to recognize. This deteriorates the high frequency magnetic properties and makes it impossible to use it as a magnetic head core. Therefore, addition of more than necessary must be avoided. However, by adding an appropriate amount of additives, the resistance to rumors can also be improved. However, as the amount added increases, the magnetic properties generally deteriorate. Therefore, within the range of the effective addition amount that can improve the mechanical strength mentioned above, although the characteristics deteriorate slightly in the region where the addition amount is large, it is possible to maintain magnetic properties sufficient to withstand use as a magnetic core. When used as a head material, its industrial value is extremely great.

[Brief explanation of the drawing]

FIG. 1 is a characteristic curve diagram showing the mechanical strength of the magnetic core material obtained by the method of the present invention, and FIGS. 2 and 3 show the degree of brittleness of the material obtained by the present invention in a strain test. FIG. 3 is a diagram showing the surface state of the magnetic core material. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 molar ratio of 10 to 25% nickel oxide, 15% zinc oxide
~40% and 45~60% of ferric oxide as a main component, and manganese oxide as a subcomponent in a weight ratio of ~0.001~
A molded product containing 3.0% is placed in oxygen or air.
Primary sintering at 200°C or lower, followed by hot isostatic sintering at 500 to 2000 atm and 1000 to 1250°C, followed by heat treatment in oxygen or air and at a temperature below the hot isostatic sintering temperature. A method for producing an oxidized metal magnetic core material.