JPS599975B2 - Method for manufacturing magnetic head core piece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic head core piece with excellent wear resistance.

The properties required for magnetic head core materials include good wear resistance against magnetic tape sliding, high saturation magnetic flux density and magnetic permeability related to the electromagnetic conversion characteristics of magnetic heads, and low coercive force. It is easy to process into pieces.

Materials for magnetic head cores that meet these requirements include:
Generally, permalloy, soft ferrite, 5-centastrite, etc. are used, but permalloy, which is relatively inexpensive and has high saturation density due to its characteristics, is mainly used.

However, it cannot be denied that this permalloy has poorer wear resistance than the other two materials mentioned above. Therefore, the present invention basically uses inexpensive permalloy, but forms a chromium oxide film on its surface to produce a magnetic head core piece with excellent wear resistance.

By the way, as a conventional means for imparting wear resistance to the magnetic head core15, for example, as shown in Japanese Utility Model Publication No. 53-3771, metal oxides such as Al2O3, Siq, MgO, etc. are deposited on the core by vacuum evaporation using an electron beam method. It is known that powders such as aluminum oxide, titanium oxide, and chromium oxide are coated by thermal spraying as shown in Utility Model Application Publication No. 109613/1983. Both methods use a method of attaching the metal oxide directly to the core surface, so they require special equipment for vacuum deposition and thermal spraying, and they also cannot achieve high productivity, resulting in high costs. There is this inconvenience.

Therefore, the present invention aims to manufacture a wear-resistant magnetic head core with high productivity and at low cost, without the need for special equipment as in the prior art.

Specifically, this invention forms a chrome plating layer on the surface of a core piece made of permalloy (Ni-Fe alloy),
700 to 110 in a humid gas with a dew point of 0 to +40°C.
This method involves performing heat treatment at 0°C to form a chrome metal oxide film with a thickness of 350.5 microns or more on the surface.

That is, the present invention is a method of improving the wear resistance of the entire core by the guard effect of the chromium oxide film.

In this invention, the dew point is limited to a range of 0 to +40°C. If the dew point is less than 0°C, oxidation of chromium is difficult to occur, and if the dew point exceeds 40°C, chromium oxidizes quickly and it is difficult to control the film thickness. This is because.

Further, the heat treatment temperature was limited to a range of 70°C to 1100°C, because below 700°C, chromium does not diffuse and the film does not grow. On the other hand, the reason is that if the temperature exceeds 1100°C, chromium diffuses quickly and it is difficult to control the film thickness. Further, the reason why the thickness of the chromium oxide film is limited to 0.5 microns or more is because the above-mentioned guard effect does not appear if the thickness is 0.5 microns or less. According to this invention, since the chromium oxide film is extremely hard with a Mohs hardness of 8.5, it serves to prevent wear caused by sliding of the magnetic tape and protect the entire core, thereby improving wear resistance. Furthermore, since the chromium oxide film is a good insulator, when core pieces are laminated, interlayer insulation can be completely obtained and eddy current loss can be reduced.
Next, embodiments of the invention will be described.

Example 1 A permalloy (Ni-Fe) thin plate is punched out using a well-known press or other means to form a desired core piece 1, and then the core piece is soaked in a known chromic anhydride bath (chromic anhydride 330
g/1, caustic soda 48g/1, trivalent chromium (Cr
2O3 Cr ionized) 62g/1, sulfuric acid 0
．． 6g/l) for 30 seconds at a current density of 80A/Dm2.
Electroplating was performed under the following conditions to deposit about 1.2μ of chromium on the core piece 1, thereby forming the core piece 7 with the chrome layer 2 shown in FIG. Piece 7 was magnetically purified in dry hydrogen at 70°C at 1100°C for about 3 hours, and then heated in wet hydrogen with a dew point of +30°C for 8 hours.
Heat treatment is performed at 00° C. for about 1 hour to oxidize the plated chrome layer 2 to form a chromium oxide film with a thickness of about 0.5 μm on its surface.

In other words, the above-mentioned magnetic sintering is an indispensable process for removing distortion in the crystal lattice of the permalloy core and improving its magnetic properties, but this magnetic sintering is also used to precipitate chromium oxide on the chromium layer at the same time. It is something. When a magnetic head was formed using the core piece formed as described above, wear characteristics 3 shown in FIG. 2 were obtained.

Example 2 A core piece similar to Example 1 was heated at 110°C in dry hydrogen at 70°C.
Magnetic sintering was carried out at 0°C for about 3 hours, and electroplating was performed in a known anhydrous chromic acid bath to form a chromium layer 2 of about 3.3μ on the core piece 1.
A heat treatment is performed at 0° C. for about 2 hours to oxidize the plated chrome layer 2 to form a chromium oxide film of about 0.8 μm on its surface.

When a magnetic head was formed using the core piece thus formed, wear characteristics 4 shown in FIG. 2 were obtained.

In addition, Fig. 2 shows the wear characteristics of commercially available high hardness permalloy6.
The wear characteristics 5 of Centast are also shown at the same time. Also,
In the examples of the present invention, heat treatment was performed at 800°C for about 1 hour in wet hydrogen with a dew point of +30°C, but the heat treatment was carried out at 800°C for about 1 hour at a dew point of +30°C.
The conditions may be changed in any way within the range of °C.

Further, if the thickness of the plating layer is 0.5 μm or more, it can be sufficiently effective against wear. In the above examples, the presence of the chromium oxide film and its thickness were determined as follows.

First, by X-ray microanalyzer analysis, we confirmed the presence of an 02-rich layer (oxygen-rich layer) in the chrome plating layer on the surface of the core piece, that is, the formation of a chromium oxide film. The thickness was calculated by using a combination of microstructural observation using a metallurgical microscope and Auger analysis while performing ion etching. As described above, according to the present invention, it is possible to provide a magnetic head core with extremely excellent wear resistance, and unlike the conventional method mentioned at the beginning, special equipment is not required and the cost is low. It has the great advantage of being inexpensive and capable of mass production.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the core piece in a chrome-plated state;
FIG. 2 is a characteristic diagram in the example.

Claims (1)

[Claims] 1 Form a chrome plating layer on a core piece made of permalloy, and heat this in a humid gas with a dew point of 0 to +40 °C to 700 °C
A method for producing a magnetic head core piece, which comprises heat-treating the piece at 1100°C to form a chrome oxide film having a thickness of 0.5 microns or more on the surface.