JPH09208301A - Nonmagnetic ceramic for magnetic head and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonmagnetic ceramic for a magnetic head, having a coefficient of thermal expansion close to that of an Mn-Zn-based ferrite, excellent in processability and extremely few in voids. SOLUTION: This nonmagnetic ceramic for a magnetic head comprises 100 pts.wt. of a main component composed of 40-48mol% calculated as CaO of Ca and 60-52mol% calculated as TiO2 of Ti, 0.02-0.20 pt.wt. of Al2 O3 and 0.10-0.30 pts.wt. of SiO2 and has 0.8-2.5μm average crystal particle diameter and 850-900kgf/mm<2> Vickers hardness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slider material for fixing a head core or the like in a magnetic head device used for magnetic recording such as a hard disk for computers, floppy disks, magnetic tapes, audio recorders and video tape recorders. For example, the present invention relates to a non-magnetic ceramic.

[0002]

2. Description of the Related Art In recent years, magnetic recording devices using magnetic heads have been increasing in recording density and capacity, and accordingly, high linear density and high track density are required for magnetic heads. There is. Therefore, a so-called composite type magnetic head device in which a magnetic head core made of Mn-Zn ferrite or the like is adhered to a slider made of non-magnetic ceramic with glass or the like has been conventionally used.

According to this composite type magnetic head,
Since the Mn-Zn ferrite adhered to the slider has a thermal expansion coefficient of 100 to 120 × 10 ⁻⁷ / ° C., the thermal expansion coefficient of the ferrite and the slider material is different from the thermal expansion coefficient of about 400 ° C. at the time of adhesion. It is necessary to match the coefficient of thermal expansion of ferrite with that of the slider material so that problems such as peeling during processing do not occur due to the effects of cracks and residual strain that result from differences. In addition, as the non-magnetic ceramics that form the slider, it is required that the material has small voids and few voids, and that the slider itself has excellent workability in order to respond to the miniaturization of the head.

Among these required characteristics, the coefficient of thermal expansion is a factor determined by the material composition, and adjustment is relatively easy. For example, in Japanese Examined Patent Publication No. 21940/1985, 100 parts by weight of a main component composed of 50 to 70 mol% of TiO _{2 and} 50 to 30 mol% of CaO is added to Al ₂ O ₃ .
A non-magnetic ceramic for a magnetic head added with 2 to 4.0 parts by weight is shown, and a predetermined thermal expansion coefficient can be obtained by adjusting the composition ratio of TiO ₂ and CaO which are main components.

Therefore, the most important points of the magnetic head ceramics forming the slider are workability and voids among the required characteristics.

Regarding workability, if the grinding resistance is large when processing for forming a slider, particularly when a groove for incorporating a magnetic head is processed with a diamond grindstone, the processing efficiency is significantly deteriorated, and therefore the grinding resistance is small. In addition, excellent workability with less chipping is required. It is generally known that as the material hardness increases, the grinding resistance increases, chipping also increases, and the workability tends to deteriorate.

Regarding voids, if many slider voids are present, for example, when the magnetic head and a floppy disk come into contact with each other to run, the magnetic powder coated on the disk adheres to the voids or from the void portion. There is a risk of chipping and damaging the magnetic head or floppy disk. Further, since there is a possibility that abrasive grains or grinding powder when polishing the slider or dust in the air may enter the voids and damage the magnetic head or the floppy disk, it is required that there be no voids.

On the other hand, the above Japanese Patent Publication No. 60-21940
It was extremely difficult to obtain void-free ceramics for magnetic heads by pressureless sintering as disclosed in Japanese Patent Laid-Open Publication No. Therefore, as described in Japanese Patent Application Laid-Open No. 3-261652, etc., it is generally performed by using a HIP (hot isostatic pressing) method to reduce voids.

[0009]

However, when the magnetic head ceramics are manufactured by the HIP method in order to eliminate the voids, the following problems occur.

In the ceramics containing a titanic acid-based compound as a main component, when fired in argon gas during HIP, Ti ions are reduced and the volume resistivity becomes low.
In addition, discoloration is likely to occur. Therefore, in order to secure good insulation and further eliminate color unevenness, it was necessary to perform an oxidation treatment after the HIP treatment. Therefore,
There is a problem that the manufacturing process becomes complicated and the product cost increases.

When the HIP process is carried out, the residual stress of the voids crushed during the HIP process is released during the oxidization process, so that the reliability of the slider is lowered.

Since HIP promotes grain growth and improves the inter-particle bonding force, the hardness of the ceramics is increased and the workability may be deteriorated.

Therefore, the present invention has a thermal expansion coefficient of 105 to 120 × 10 ^-7 / ° C. which is similar to that of Mn-Zn ferrite, and in order to solve the above-mentioned drawbacks, the void amount is reduced without HIP treatment, Further, it is an object of the present invention to provide a non-magnetic ceramic for a magnetic head, which has low hardness and excellent workability, and has low cost and high reliability.

[0014]

As a result of repeated studies on the above-mentioned problems, the present inventor has calculated that Ca is 40 to 40 in terms of CaO.
48 mol% and 60 to 52 mol% of Ti in terms of TiO _2.
0.02 with respect to 100 parts by weight of the main component consisting of
~ 0.20 parts by weight of Al ₂ O ₃ and 0.10 to 0.30
The composition contains parts by weight of SiO ₂ , the average crystal grain size is 0.8 to 2.5 μm, and the Vickers hardness is 850 to 900.
It was found that non-magnetic ceramics for magnetic heads having excellent characteristics can be obtained by controlling to kgf / mm ² .

Hereinafter, the present invention will be described in detail.

According to the present invention, the main component of ceramics is substantially composed of oxides of Ca and Ti, and CaO is 4
It is important that the composition is 0 to 48 mol% and TiO ₂ is 52 to 60 mol%.

The reason for limiting the above composition is that CaO is 40
When the content of TiO ₂ is less than 60 mol% and the content of TiO ₂ exceeds 60 mol%, the coefficient of thermal expansion becomes less than 105 × 10 ⁻⁷ / ° C.
Not suitable as a slider material for ferrites. On the other hand, when CaO exceeds 48 mol% and TiO ₂ is less than 52 mol%, the TiO ₂ crystal phase in the ceramics decreases, and the grain growth of calcium titanate (CaTiO ₃ ) crystals cannot be suppressed. Abnormal grain growth occurs and voids remain in the ceramic.

Further, in the present invention, as an accessory component, 0.02 to 0.02 is used.
0.20 parts by weight of Al_TwoO_ThreeAnd 0.10 to 0.30
Part of SiO_Two It contains. Reasons for limiting the above composition
, Although these components act as sintering promoters,
_TwoO_Three0.20 parts by weight, SiO_TwoOver 0.30 parts by weight
This promotes crystal grain growth, which results in crystal growth
This is because the pores gather at the grain boundaries and aggregate to form voids.
You. The lower limit of Al _TwoO_Three0.02 parts by weight, SiO
_Two0.10 part by weight is contained as an unavoidable impurity in the primary raw material.
It is the amount to be covered.

Further, in addition to the above-mentioned components, the ceramic of the present invention contains Fe ₂ O ₃ , Nb ₂ O ₅ , MgO, P ₂ O ₃ ,
SrO, BaO, ZrO ₂ , and NiO may be contained in an amount of 0.5 parts by weight or less, respectively, in a range of 2 parts by weight or less in total.

Further, according to the present invention, it is important that the average grain size of the crystals constituting the ceramic is in the range of 0.8 to 2.5 μm. This is because the average crystal grain size is 0.8μ
This is because if it is less than m, it is not possible to obtain a dense ceramics due to insufficient sintering, and there are many voids so that the strength becomes low and it cannot be used as a slider material. On the other hand, the average crystal grain size is 2.5μ
When it exceeds m, pores are gathered in the grain boundary phase portion as the crystal grains grow, and voids are generated. That is, according to the present invention, voids increase rapidly when the average crystal grain size exceeds 2.5 μm.
It was found that the voids can be sufficiently reduced by controlling the thickness to be 5 μm or less.

Further, in the present invention, the Vickers hardness of ceramics is set to 850 to 900 kgf / mm ² , but if it is less than 850 kgf / mm ² , wear resistance is poor,
On the other hand, if it exceeds 900 kgf / mm ² , the workability is deteriorated.

Next, the non-magnetic ceramics for magnetic head of the present invention is manufactured from a step of forming raw materials prepared and pulverized to have the above composition range into a predetermined shape, and then firing at a normal pressure of 1150 to 1250 ° C. It is characterized by doing.

First, a raw material powder for producing CaO or TiO ₂ by firing, such as CaCO ₃ powder or TiO ₂ powder, is prepared and, in some cases, partially calcined. If necessary, Al ₂ O ₃ and SiO ₂ are added to these raw material powders, and they are weighed and mixed so as to have the above-mentioned ratio.

At this time, it is important that the final Al ₂ O
₃ and SiO ₂ contents are 0.20 parts by weight and 0.
It should not exceed 30 parts by weight. For that purpose, it is preferable to use CaCO ₃ powder, TiO ₂ powder, or the like with high purity, and to use, for example, zirconia balls instead of alumina balls as the crushing balls and liner during the mixed crushing.

The raw material thus obtained is shaped by a desired shaping means and fired. At the time of firing, the firing temperature and firing time are adjusted so that the average crystal grain size of the final sintered body falls within the above range. It is necessary to. Specifically, 1
It suffices to carry out calcination in the atmosphere at 150 to 1250 ° C under atmospheric pressure for 1 to 2 hours.

Here, the firing temperature is set within the above range because
This is because if the temperature is lower than 1150 ° C, it is difficult to completely sinter, and if the temperature exceeds 1250 ° C, the average crystal grain size becomes large. Further, the reason why the firing is performed under normal pressure is that the hardness of the obtained sintered body becomes high and the workability deteriorates and the manufacturing process becomes complicated if the HIP treatment is performed as described above.

The non-magnetic ceramic for magnetic head of the present invention thus obtained has two phases, ie, a calcium titanate (CaTiO ₃ ) phase and a rutile-structured titanium oxide (TiO ₂ ) phase as crystal phases. The titanium oxide phase has the effect of suppressing the crystal growth of the calcium titanate phase.

As described above, the present invention suppresses the crystal growth during firing and reduces the average crystal grain size by reducing the addition amounts of Al ₂ O ₃ and SiO ₂ which act as sintering accelerators. This is to prevent the generation of voids. Therefore, ceramics with few voids can be obtained by normal pressure firing without HIP treatment.

[0029]

Example 1 Calcium titanate (CaTiO ₃ ) powder and titanium oxide (TiO ₂ ) powder were weighed so that the composition ratio shown in Table 1 was obtained, and A was measured with a mill using zirconia balls.
By suppressing the mixture of l ₂ O ₃ and SiO ₂ , the average particle size is 0.6
It was wet-mixed and pulverized so as to have a particle size of not more than μm. In the raw material powder, Al ₂ O ₃ was 0.02 parts by weight and SiO ₂ was 0.10 parts by weight with respect to 100 parts by weight of the main component.
Parts by weight were included.

A binder was added to this raw material for granulation, and then the raw material was molded under a pressure of 0.8 to 2.0 ton / cm ² . After that, 1 to 1250 to 1250 ℃ under atmospheric pressure
It was fired for 2 hours to obtain a sintered body shown in Table 1.

The average crystal grain size and workability of the obtained sintered body were measured by the following methods.

The average crystal grain size was obtained by mirror-polishing the obtained sintered body and then etching it to obtain a 1500 times scanning electron microscope (SE).
M) Take a picture and draw an arbitrary 8 cm straight line on this picture.
This was calculated by the following: average crystal grain size (μm) = 80000 × 3 ÷ 1500 ÷ N 2, where N is the number of crystal grains on this straight line.

The workability is determined by the maximum load power applied to the main spindle of the diamond wheel and the chipping size generated at the edge portion after the groove processing when a groove having a depth of 2 mm is processed by the diamond wheel using a surface grinder. evaluated. The smaller the maximum load current and the chipping size, the better the workability.
W or less and chipping size of 50 μm or less were evaluated as ◯, and chipping sizes of 50 μm or more were evaluated as x.

The bulk density of the obtained sintered body is 4
The coefficient of thermal expansion and the void rate at 0 to 400 ° C. were examined. The void ratio is evaluated by measuring the number of voids of 5 μm or more occupied in the final lap surface by the diamond abrasive grains of 1 μm, and the number of voids per 3080 μm ² is x or more, 10 to 50 is Δ, and 10 or less. Is indicated by a circle.

The results of each measurement are shown in Table 1. Of these, Since the composition ratios of the main components of Nos. 1, 21, and 22 were out of the range of the present invention, the coefficient of thermal expansion was out of the desired range or the void ratio was poor. No. 2, 9,
In Nos. 17 and 19, since the firing temperature was higher than 1250 ° C and the average crystal grain size was more than 2.5 µm, the void ratio was poor,
On the other hand, no. In Nos. 8 and 15, since the firing temperature was lower than 1150 ° C. and the average crystal grain size was less than 0.8 μm, the porosity was high and the sintering was not completed. In addition, No. As Comparative Example 16, as a comparative example, it was subjected to HIP treatment at 1100 ° C. under 2000 atm after firing at 1250 ° C. The void ratio was excellent, but the workability was poor because the hardness was high.

On the other hand, the firing temperature is 1150 to 12
The average crystal grain size was set to 50 ° C. and the average crystal grain size was set in the range of 0.8 to 2.6 μm. 3-7, 10-1
In 4, 18, and 20, all are 105 to 120 × 10 ⁻⁷
It had a coefficient of thermal expansion of / ° C and a porosity of 0.3% or less, which was almost completely sintered, and was an excellent result in terms of workability and void rate.

[0037]

[Table 1]

[0038]

Example 2 Calcium titanate (CaTiO ₃ ) powder, titanium oxide (TiO ₂ ) powder, alumina (Al ₂ O)
₃ ) powder, silica (SiO ₂ ) powder, the final composition is shown in Table 2.
The mixture was weighed so as to have the ratio shown in Table 1, and the mixture was pulverized by wet mixing so that the mixture of impurities was suppressed by using a mill and the average particle diameter was 0.6 μm or less. A binder was added to this raw material for granulation, and then the raw material was molded at a pressure of 0.8 to 2.0 ton / cm ² . After that, 1 to 1250 to 1250 ℃ under atmospheric pressure
It was fired for 2 hours to obtain a sintered body of Table 2.

The Vickers hardness, workability and void ratio of the obtained sintered body were measured. Vickers hardness is
A load of 500 g was applied with a Vickers hardness meter to measure 10 points, and the average value was taken as the Vickers hardness. The workability and void rate are the same as in Example 1.

The results are shown in Table 2. From this result, Al ₂ O
₃ and SiO ₂ contents are 0.20 parts by weight and 0.
No. over 30 parts by weight. In Nos. 25, 28 and 31, the void ratio was poor due to crystal growth. On the other hand, Al
N having a content of ₂ O ₃ and SiO ₂ within the range of the present invention
o. In Nos. 23, 24, 26, 27, 29 and 30, crystal growth was suppressed, so that the void ratio could be made excellent and the workability was also excellent.

[0041]

[Table 2]

[0042]

As described above, according to the present invention, Ca is changed to C
0.02 to 0.20 parts by weight of Al ₂ O ₃ with respect to 100 parts by weight of the main component consisting of 40 to 48 mol% in terms of aO and 60 to 52 mol% of Ti in terms of TiO ₂ .
It contains 0.10 to 0.30 parts by weight of SiO _2, has an average crystal grain size of 0.8 to 2.5 μm and a Vickers hardness of 850.
By was ~900kgf / mm ^2, Mn-Z
It is possible to obtain a non-magnetic ceramic for a magnetic head, which has a coefficient of thermal expansion similar to that of an n-type ferrite, is excellent in workability, and has very few voids.

The non-magnetic ceramics for magnetic head of the present invention is manufactured from a process in which raw materials prepared and pulverized to have the above composition range are molded into a predetermined shape and then fired under a normal pressure of 1150 to 1250 ° C. By doing
Ceramics with few voids can be obtained in a simple process without performing P treatment.

Therefore, if a slider for a magnetic head is constructed using this non-magnetic ceramic for magnetic head,
It is possible to provide a high-performance magnetic head which can cope with high density of the magnetic recording device, has a long life, and does not adversely affect the magnetic medium.

Claims (2)

[Claims] 1. Ca is 40 to 48 mol% in terms of CaO,
Ti is 0.02 to 0.20 parts by weight of Al ₂ O ₃ and 0.10 to 0.30 parts by weight with respect to 100 parts by weight of the main component composed of 60 to 52 mol% in terms of TiO ₂ . SiO
_A non-magnetic ceramic for a magnetic head, containing _2, having an average crystal grain size of 0.8 to 2.5 μm and a Vickers hardness of 850 to 900 kgf / mm ² . 2. Ca is 40 to 48 mol% in terms of CaO,
Ti is 0.02 to 0.20 parts by weight of Al ₂ O ₃ and 0.10 to 0.30 parts by weight with respect to 100 parts by weight of the main component composed of 60 to 52 mol% in terms of TiO ₂ . SiO
_A method for producing a non-magnetic ceramic for a magnetic head, which comprises a step of forming a raw material which is prepared and pulverized so as to contain ₂ , into a predetermined shape, and then firing the material under a normal pressure of 1150 to 1250 ° C.