JPH0633168B2 - Porcelain composition for magnetic head - Google Patents

Description

The present invention relates to a magnetic head porcelain (hereinafter referred to as a porcelain head slider) that supports a magnetic pole piece (ferrite core) used in a magnetic head such as a floppy disk. The present invention relates to a porcelain composition, and more particularly to a porcelain composition for a slider for a porcelain head suitable for Mn-Zn ferrite.

(Background Art) As shown in the figure, the slider 1 is generally a ferrite core 2
Are bonded by heat treatment through the adhesive glass 3 to form a magnetic head. Therefore, if there is a large difference in thermal expansion between the slider and the ferrite core, cracks or residual strains will occur in these materials due to the thermal history during heat treatment, and glass peeling or the like will occur during the assembly process. Therefore, the slider must have its ceramic composition and composition ratio selected to match the coefficient of thermal expansion of the ferrite core.

There are various grades of ferrite cores depending on the application, and the thermal expansion coefficient is 105 to 12 depending on this grade.
It needs to be applied to a wide range of 5 × 10 ^-7 / ° C. Therefore, by changing the composition ratio of the slider, 105
It is desired that a wide range of thermal expansion coefficient of up to 125 × 10 ⁻⁷ / ° C. be easily selected.

Further, this slider is required to have as few pores as possible in the porcelain sintered body. If there are many pores on the surface of the sintered body that comes into contact with the floppy disk, the magnetic powder coated on the disk surface will easily adhere to the pores, and the existence of the adhered magnetic powder will impair the porcelain characteristics during recording and reproduction. Bring

In addition, the porcelain of the slider must be sufficiently sintered and densified. If the sintering is insufficient and the strength and toughness are inferior, chipping and cracks will occur in the porcelain, leading to a serious defect that the disk itself will be damaged when running on a floppy disk.

On the other hand, Ni-Zn ferrite has been conventionally used as a core of a porcelain head, but as a ferrite core for a floppy disk, Mn-Zn ferrite is now superior to Ni-Zn in magnetic characteristics, particularly in coercive force. From that, Mn
-It is shifting to Zn ferrite.

(Explanation of Prior Art) Forsterite and barium titanate having a thermal expansion coefficient of about 90 to 98 × 10 ⁻⁷ / ° C. are known as slider compositions applied to Ni—Zn ferrite. .
However, when these porcelains are applied to Mn-Zn ferrite, the thermal expansion coefficient of Mn-Zn ferrite is 105 to 125 ×
Since it is 10 ⁻⁷ / ° C. and the difference in thermal expansion is too large, it is difficult to apply these porcelains.

On the other hand, as a slider composition applied to Mn-Zn ferrite, for example, calcium titanate, magnesium titanate, and strontium titanate, which are mainly composed of a titanate compound, have almost the same thermal expansion coefficient as that of Mn-Zn ferrite. It is known to be degree. However, Mn
-Zn ferrite is 105 to 125 × 10 ^-7 / depending on required characteristics
There are a wide variety of grades in a wide range of ℃, but for the magnetic head that has been conventionally used to linearly change the thermal expansion coefficient of this wide range only by changing the composition ratio and easily match the thermal expansion coefficient of various grades. No slider composition has been found.

On the other hand, in the composition containing the titanate compound as a main component, when fired in, for example, argon gas, Ti ions are reduced, so that the color tone of the porcelain is extremely changed. In this case, it is necessary to restore the changed color of the porcelain.

Further, since the desorption of crystal grains becomes a problem during mirror-finishing in the sintered body mainly composed of the titanate compound, there is no need for de-graining and selective polishing (soft grains are selectively polished). A magnetic head slider composition having excellent properties is desired.

(Present invention is a problem to be solved) The present inventors whereas the main component of the current result of intensive research in view of the, Mn-Zn CaO-SiO ₂ compound close to the thermal expansion coefficient of the ferrite, the specific amount of TiO By adding ₂ , the SiO ₂ component becomes a stable crystal consisting of a uniform calcined product of calcium silicate (CaSiO ₃ ) compound other than the glass phase and calcium titanate (CaTiO ₃ ), and the mixing ratio of these is adjusted. The thermal expansion coefficient of Mn-Zn ferrite is 105 to 125 ×
A slider for a magnetic head that can be applied to a wide range of 10 ^-7 / ° C, has good sinterability, has few pores, can prevent color unevenness due to reducing atmosphere treatment, and has excellent mirror surface workability. It was found that a composition was obtained.

(Object of the invention) Therefore, the present invention is a dense sintered body containing a calcium silicate (CaSiO ₃ ) compound and calcium titanate (CaTiO ₃ ) with a small glass component, and the thermal expansion of Mn-Zn ferrite. To provide a slider composition for a magnetic head, which can be applied to a wide range of coefficients, has good sinterability, has few pores, can prevent color unevenness due to a reducing atmosphere treatment, and has excellent mirror finish. With the goal.

(Means for Solving the Problem) According to the present invention, SiO ₂ is 22 to 50 mol%, and TiO ₂ is ₂ to 30%.
There is provided a porcelain composition for a magnetic head, which is composed of mol% and CaO of 45 to 57 mol%.

The magnetic composition having the above composition range has a fine uniform mixed structure composed mainly of one or more of CaSiO ₃ phase or Ca ₃ Si ₂ O ₇ phase and CaTiO ₃ phase at an appropriate firing temperature, and has a conventional forsterite structure. Sinterability is improved as compared with MgO-SiO ₂ porcelains such as, and a dense sintered body can be obtained.

Further, in the porcelain composition having the above composition range, Ca
The uniform composition of SiO ₃ phase or Ca ₃ Si ₂ O ₇ phase and CaTiO ₃ phase is the main constituent, and the glass component is small, so there is little shedding and selective polishing during mirror finishing caused by the glass component existing at the grain boundaries. Become. In addition, due to the presence of the CaSiO ₃ phase and the Ca ₃ Si ₂ O ₇ phase, the hardness is M more than that of the conventional titanate-based slider material.
It approaches the n-Zn ferrite, and it becomes easy to maintain the flatness of the head guarantee surface (the surface on the side that contacts the floppy disk) after glass welding. Further, since it has a stable crystal phase composed of a uniform calcined product of CaSiO ₃ and CaTiO _3, it has a thermal expansion coefficient of 105
The coefficient of thermal expansion can be linearly changed by changing the composition ratio in a wide range of up to 125 × 10 ⁻⁷ / ° C., and a slider having a desired coefficient of thermal expansion can be obtained.

If the SiO ₂ content is less than 22 mol%, the densification of the sintered body is hindered on the side where the amount of CaO is large, and the densification of the sintered body is good on the side where the amount of TiO ₂ added is large, but the color tone changes / color due to reduction. The unevenness is likely to occur. When SiO ₂ exceeds 50 mol%, SiO ₂ exists alone and a glass phase is easily formed, so that pores are generated and sufficient densification cannot be achieved. If TiO ₂ is less than 2 mol%, CaSi
Since the sintering of O ₃ and Ca ₃ Si ₂ O ₇ cannot be promoted sufficiently, the generation of pores cannot be suppressed sufficiently. When the content of TiO ₂ exceeds 30 mol%, the CaTiO ₃ phase is increased on the side where CaO is added a lot, so that the effect in a reducing atmosphere becomes remarkable,
Easily color unevenness occurs, CaTiSiO ₅ with more sides of SiO ₂ added
Since a phase (coefficient of thermal expansion is 65 × 10 ^-7 / ° C) is generated, the coefficient of thermal expansion becomes extremely low. CaO denseness of the glass phase is generated tends sintered body mainly composed of SiO ₂ with large side of SiO ₂ added is deteriorated is less than 45 mol%, of the thermal expansion coefficient in TiO ₂ added is large sides This is a region where a low CaTiSiO ₅ phase is formed, and the coefficient of thermal expansion drops extremely. When CaO exceeds 57 mol%, CaO is likely to exist in an unreacted state, has hydration properties and has poor water resistance, and is generally unsuitable as a magnetic head slider.

The CaSiO ₃ and Ca ₃ Si ₂ O ₇ phases have a pure composition ratio (CaO: SiO ₂ = 50: 5).
Although it is difficult to obtain a dense sintered body with the formulation of 0 mol% and 60:40 mol%), the addition of TiO ₂ has an auxiliary effect on the formation of CaSiO ₃ and Ca ₃ Si ₂ O ₇ phases. After all, both phases are conventional Ti
The calcination temperature is lower than that of the O ₂ -CaO system, that is, 10
What had been about 00 to 1150 ° C, crystal formation proceeds at about 900 to 1100 ° C, and uniform crystal growth occurs during main firing.
Abnormal grain growth can be suppressed.

Hereinafter, the present invention will be described in detail with reference to examples. In the present invention, a method of manufacturing a slider for a magnetic head is as follows: the raw materials are weighed to a predetermined composition ratio, mixed and pulverized and then calcined, and then the calcined product is finely pulverized, and an organic binder is added to granulate the mixture. A usual method of firing after shaping into a shape is adopted.

(Example) Commercially available industrial raw material (purity of 98% or more), silica (SiO ₂ ) as a silica source, titanium oxide (TiO ₂ ) as a titania source,
Calcium carbonate (CaCO ₃ ) or calcium hydroxide (Ca (OH) ₂ ) is selected as the calcia source, weighed so that the composition ratios shown in Table 1 are obtained, wet mixed using a ball mill, and dried 900 Calcination was performed at ~ 1100 ° C for 1-2 hours. After calcination, the mixture of impurities was suppressed and finely pulverized, an organic binder and the like were added, and after granulation, pressure molding was performed at 1.0 to 2.0 t / cm ² . Then, it baked at 1250-1380 degreeC in air | atmosphere, and obtained sample No. 1-15 shown in Table 1.

The crystal phase of the obtained sintered body was identified by the X-ray diffraction method. The production ratio was determined by the peak ratio, and at the same time, the area ratio was measured from the difference in the light reflectance due to each crystal phase of the sample mirror surface using the XMA device by the image analyzer, and the volume ratio was converted to the evaluation. It should be noted that this value almost coincided with the quantity ratio obtained by the X-ray diffraction method. Hardness is a load of 1 kg (Hv (1.0)
It shows with the Vickers hardness. Measurement calculation is JIS Z22
According to 44, the unit is kg / mm ² . Regarding the compactness of the sintered body, those having a water absorption of more than 2% are indicated by x, those having o% are indicated by o, and the middle thereof is indicated by Δ. Color unevenness was evaluated by observing the inside of the sintered body after the reducing atmosphere treatment and whether there was a difference in color from the surface.

As can be seen from Table 1, sample Nos. 1, 8, 9, 10, 1
Sample Nos. 1 and 13 are out of the composition range of the present invention.
In Nos. 8 and 8, since the amount of TiO ₂ was small, the sintering was not sufficiently promoted. Samples No.9 and 10 are SiO ₂ amount is small based, CaO intensive side (sample No.9) in densification of the sintered body is inhibited, TiO ₂ intensive side (sample No.10) The color unevenness has occurred. Sample No. 11 is a system with a large amount of TiO ₂ ,
_{2 The} CaTiSiO ₅ phase with a low coefficient of thermal expansion is generated on the side with a relatively large amount of addition, and it can be seen that the coefficient of thermal expansion is extremely low at 65 × 10 ^-7 / ° C. In sample No. 13, the amount of SiO ₂ was slightly increased, so that SiO ₂ was present alone and a glass phase was formed, and pores were generated, so that it was not sufficiently densified. Sample No. 14 is a typical example of a conventional TiO ₂ —CaO composition composed of _two phases, a CaTiO ₃ phase and a TiO ₂ phase, and is a typical example.
The hardness of -Zn ferrite is considerably larger than about 650 kg / mm ² , and it becomes easy to selectively polish the Mn-Zn ferrite side during mirror finishing. Sample 15 is a conventional forsterite porcelain, which has a small coefficient of thermal expansion and is too hard to be applied as a slider for Mn-Zn ferrite.

On the other hand, sample Nos. 2 to 7 and 12 are within the range of the present invention, and the thermal expansion coefficient is selected within the range of 105 to 125 × 10 ^-7 / ° C applicable to Mn-Zn ferrite. A dense sintered body having good porcelain hardness and sinterability is obtained, and color unevenness does not occur.

Further, sample No. 14 and each sample No. 2 within the scope of the present invention
Comparing the calcination temperatures of Nos. 7 and 7, it is understood that the calcination temperature is comparatively lower than that of the conventional TiO ₂ —CaO system.

The present invention as described above can be applied to a wide range of thermal expansion coefficient of the Mn-Zn ferrite by a specific composition ratio of these as SiO ₂ -TiO ₂ -CaO-based, fully a pore densification of the sintered body It is possible to obtain a slider composition for a porcelain head, which is less likely to cause the occurrence of color unevenness due to the treatment in a reducing atmosphere and has excellent mirror-finishing processability.

[Brief description of drawings]

The drawing is a perspective view of a magnetic head used for a floppy disk.

Claims (1)

[Claims] 1. A magnetic head porcelain composition comprising 22 to 50 mol% of SiO ₂ , ₂ to 30 mol% of TiO ₂ , and 45 to 57 mol% of CaO.