JPS6158429B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to non-magnetic materials used for structural parts of magnetic heads, and more particularly to a ceramic composition for magnetic heads used for sliders or spacers essential to the construction of various magnetic heads such as computers, particularly ferrite magnetic heads for floppy disks. . Generally, magnetic heads are made of Mn-Zn ferrite, Ni
-A core made of Zn ferrite magnetic material and structural parts made of non-magnetic material are assembled by glass welding.Ni- High permeability Mn-Zn instead of Zn ferrite
Ferrite is used, and TiO ₂ -CaO-based porcelain with the same coefficient of thermal expansion is used as the non-magnetic structural component material. In other words, if the core material and non-magnetic structural components have different coefficients of thermal expansion, distortion will occur when they are welded to glass, which will not only cause deterioration of magnetic properties, but also cause cracks, peeling, etc., and damage the magnetic head. This has become a major problem in assembly. Furthermore, if there are many pores in this non-magnetic structural component material, when the magnetic head and the recording medium come into contact with each other, the magnetic powder coated on the recording medium may adhere to the pores or cause chipping, which may cause the magnetic head or recording medium to run in contact with each other. Due to media damage, densified non-magnetic porcelain compositions with low porosity are desired. Conventional TiO ₂ -CaO based porcelain compositions
Within the range of the two-phase mixed structure of TiO ₂ and TiO ₂ ,
It is known that the coefficient of thermal expansion increases linearly with the amount of CaO/TiO ₂ , and the coefficient of thermal expansion of the Mn-Zn ferrite core material mentioned above is fixed by the composition determined by the required electromagnetic properties. However, since it is 105 to 120×10 ^-7 /℃, it is necessary to match the thermal expansion coefficient of the non-magnetic structural component material to that of ferrite, and the difference in thermal expansion coefficient should be kept below 2×10 ^-7 /℃. To suppress _TiO2 50~75wt%, CaO25~
A porcelain composition with a composition of 50 wt% was used. On the other hand, as a method for reducing pores in a ceramic composition, Al ₂ O ₃ , SiO ₂ ,
A known method is to improve the sintered density by adding at least one kind of sintering auxiliary material such as MgO, SrO, CdO, or ZrO ₂ up to 4wt%. If pores remain, especially if the amount of ZrO ₂ added is less than 2wt%, the size of the molded product may be 40mm x 20mm.
When the size is as large as mm x 20 mm, the problem with normal sintering methods is that the inside of the sintered body is reduced and becomes black. In addition, hot isostatic pressing is a known method for reducing porosity, and although it is extremely effective, since this treatment is usually performed in an argon atmosphere, the surface of the treated material is reduced and becomes black. Even if heat treatment is performed again in an oxygen atmosphere, it is difficult to completely decolorize the material, and it is not possible to uniformly restore the color to the inside of the material. In view of the above problems, this invention has a coefficient of thermal expansion equivalent to that of Mn-Zn ferrite, a very dense crystal structure, and can be processed by normal sintering without hot isostatic pressing. _TiO2 with a porosity of less than 0.2%, which is equivalent to hot isostatic pressing treatment.
We propose a CaO-based porcelain composition. That is, this invention can contain TiO ₂ 50wt% ~ 75wt%
%, CaO25wt%~50wt%, _TiO2 , CaO
Contains _ZrO2 exceeding 8wt% and 15wt% or less, and MgO3wt% to 8.5wt%, with the total of 100,
This ceramic composition for magnetic heads consists of four phases: CaTiO ₃ , TiO ₂ , ZrTiO ₄ and MgTiO ₃ and has a high density with a porosity of 0.2% or less. The porcelain composition according to the present invention includes CaTiO ₃ ,
It is characterized by being composed of four phases: TiO ₂ , ZrTiO ₄ , and MgTiO ₃ , and can be made as dense as the porosity of hot isostatically pressed materials, while also having a low coefficient of thermal expansion.
It can be precisely adjusted in the range of 105 to 120 × 10 ^-7 /℃, and because it contains ZrO ₂ , it can be sintered at a lower temperature than conventional sintering temperatures, making it a dense, defect-free material with few pores and wear resistance. It has good properties, has a sufficiently small crystal grain size, and has good workability. When the ZrO ₄ phase in the porcelain composition according to the present invention was observed using an X-ray microanalyzer, it was found that most of the ZrO ₄ phase was generated at grain boundaries.
As the in-phase increases, O ₂ through the ZrTiO ₄ phase in the crystal
It is thought that this allows for the inflow of the sintered body, which is effective in preventing blackening inside the sintered body. The reasons for limiting the components of the porcelain composition according to the present invention are as follows. When _TiO2 content is less than 50wt%, the thermal expansion coefficient is 120
×10 ^-7 /℃, and if the TiO ₂ content exceeds 75wt%, the thermal expansion coefficient will be 105 × 10 ^-7 /℃.
TiO2 is less than 50wt%, making it unsuitable as a partner material for glass welding with Mn-Zn ferrite.In order to maintain the same thermal expansion coefficient as Mn-Zn ferrite, which has a coefficient of thermal expansion of 105 to 120×10 ^-7 /℃, TiO ₂ 50wt% is used. The content should be ~75wt%. If the CaO content exceeds 50wt%, the thermal expansion coefficient will exceed 120×10 ^-7 /℃, and the CaO content will exceed 25wt%.
If the content is less than 105 × 10 ^-7 /℃, the thermal expansion coefficient
CaO25wt%~50wt is less than 50wt%, making it unsuitable as ^a partner material for glass welding with Mn-Zn ferrite. % content. ZrO ₂ is added to improve the porosity of the TiO _{2 -CaO} system;
If the total amount of CaO is 100, if it is less than 8wt%, the porosity of the sintered ceramic composition will be more than 1.0%, and the structure will be
There are four phases: CaTiO ₃ , TiO ₂ , ZrO ₂ , and MgTiO ₃ ,
The inside of the sintered body is unfavorable because it is easily reduced and turns black. In addition, if the content exceeds 15 wt%, the porosity of the sintered body will be 0.2% or more, and the workability will deteriorate, making it unsuitable as a mating material for soft ferrite. Therefore, the addition should be more than 8 wt% and less than 15 wt%. By adding MgO to the ZrO ₂ -containing TiO ₂ -CaO system, the sintering temperature can be lowered, resulting in finer crystals, resulting in a material with less grinding resistance and stabilizing the crystal grain size. It is effective for
However, addition of MgO in excess of 8.5 wt% is unsuitable because it makes the coefficient of thermal expansion too small, and it is also undesirable because the hardness becomes too high. Less than 3wt%
Addition of MgO is not preferable because as the amount of TiO ₂ increases, crystals grow, compactness is lost, and the coefficient of thermal expansion increases. Therefore, MgO is 3wt% ~
The content is 8.5wt%. The present invention will be explained below based on examples. Using commercially available TiO ₂ , CaCO ₃ , ZrO ₂ , and MgO, as shown in Table 1, the composition after sintering is the composition ratio according to the present invention (No. 1 to 6) and the composition ratio outside the scope of the present invention. Weigh out the composition ratio (No. 7 to 9), mix in a ball mill, dry, and then mix in the air.
Calcining was performed at 900°C for 2 hours. Furthermore, the calcined raw material was again finely ground in a ball mill until the average particle size was 1.3 μm, and then 1.5 wt % of polyvinyl alcohol was added as a binder and granulated. After granulation,
It was molded into a size of 40 x 20 x 20 mm under a molding pressure of 2000 Kg/cm ² and sintered in air at 1200°C for 2 hours. The obtained porcelain was examined for properties such as density, coefficient of thermal expansion, and Vickers hardness, and the measurement results are shown in Table 2. Furthermore, the workability in the table is evaluated by using the same processing machine and expressing the increase in power of the spindle motor in watts. As is clear from Tables 1 and 2, Sample No. 7~
Comparative Example No. 9 has a thermal expansion coefficient that matches that of Mn-Zn ferrite, 105 to 120×10 ^-7 /°C, but has poor porosity;
No. 1 to 6) have a thermal expansion coefficient of 105 to 120×10 ^-7 /℃
It exhibits excellent properties such as mechanical strength and workability, and in particular, it is densified to the same degree as materials treated with hot isostatic pressing, the crystal grain size is small, and pores are reduced. Since the obtained porcelain has low porosity and good workability, it has excellent wear resistance and is found to be optimal as a material for magnetic head structural parts on which the recording medium slides.

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Claims (1)

[Claims] 1 _TiO2 50wt%~75wt%, CaO25wt%~50wt%
and the total of TiO ₂ and CaO is 100,
_ZrO2 more than 8wt% and less than 15wt%, and MgO3wt%~
A porcelain composition for a magnetic head, characterized by containing 8.5 wt% and having a high density with a porosity of 0.2% or less.