JPS6027082B2 - magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the wear resistance of a magnetic head, particularly a magnetic head using a Sendust alloy.

Sendust alloy (Si 8-1 box weight% peak 4-8 weight% residual Fe) has significantly higher saturation magnetic flux density and magnetic permeability than oxide magnetic materials, and has a higher resistivity than other alloy magnetic materials. Since it has extremely high hardness, it is used as a magnetic head material for video devices that requires wear resistance.

However, even with this Sendust alloy, there is a problem that the hardness is lower than that of the oxide magnetic material, and the wear rate is about 1M tone higher than that of the oxide magnetic material. On the other hand, in a video magnetic head, the relative speed between the magnetic head and the tape is 11~
The relative speed of the audio head is 4.8 to 10 seconds, which is 10 phona louder than the relative speed of the audio head.
Therefore, it is extremely important to use materials with excellent wear resistance for video heads, and improving the wear resistance of sendust alloys has become a major issue. One method of obtaining a magnetic head made of Sendust alloy with excellent wear resistance is to use a single crystal Sendust alloy.

The wear rate of sendust differs depending on the crystal plane and orientation.
Other than the 0> direction etc. have higher wear resistance than crystal planes and orientations. Therefore, by aligning these planes and orientations with the tape facing surface of the magnetic head and the tape running direction, a magnetic head with excellent wear resistance can be obtained. but,
It is not necessarily easy to produce single crystal sendust alloy, and magnetic heads using this have the drawback of being expensive.

An object of the present invention is to obtain a magnetic head made of Sendust alloy with excellent wear resistance without using single-crystal Sendust alloy.

In order to achieve the above object, the present invention uses a polycrystalline sendust alloy in which the directions of each crystal grain are substantially parallel to each other as a magnetic head material.
The magnetic head is manufactured so that the 100> direction approximately coincides with the tape running direction of the magnetic head (approximately approximately 1y).

This makes it possible to obtain a magnetic head with better wear resistance than conventional single-crystal Sendust alloy magnetic heads without using single-crystal Sendust alloy. Generally, when a metal material is melted and then poured into a metal mold and solidified,
It is known that the portion in contact with the mold can form a columnar structure in the direction perpendicular to the mold. This columnar structure is formed by elongated growth of metal crystals in one direction, and may grow so that the axial direction of this columnar structure coincides with a certain direction of the metal crystals. Like Fe-N-Si alloys, body 0
In the case of crystals with a cubic structure, for example, as shown in "Introduction to Metal Physics Engineering: Hideo Kaneko, published by Asakura Shoten, June 15, 1939, p. 121," the crystal has a columnar structure. It is known that the axial direction is the <100) direction. As mentioned above, the Fe-Yamaichi Si alloy having a columnar structure aligned in the <100> direction used in the present invention has a Fe-AI-
It can be obtained from the part of the Si alloy ingot that is in contact with the mold or the part around it.

Such a columnar structure is generated when the Fe-N-Si alloy is cooled from the mold and solidifies rapidly.
In order to obtain a columnar structure, it is necessary to increase the cooling rate by controlling the ingot manufacturing conditions, that is, the material of the mold, the shape and size of the ingot, and the temperature. Types of molds are generally divided into ceramic molds such as sand molds and metal molds, but in order to increase the cooling rate, it is necessary to use molds with high thermal conductivity. .

As for the material of the mold, copper is preferable because it has high thermal conductivity, but a mold made of soft iron is better in terms of wettability with the setting sun and is therefore more preferable in terms of increasing the cooling rate. Furthermore, in order to cool the mold itself, it is further preferred that the outside of the mold be cooled by a water-cooled pipe. Furthermore, the cooling rate depends on the rate at which latent heat generated when the molten metal is cooled is removed, and the cooling rate can be increased if the total amount of latent heat is small.

Therefore, the smaller the volume of the ingot, the higher the cooling rate. Further, even if the ingot has the same volume, the larger the contact area with the mold, the higher the cooling rate, so the shape of the ingot is preferably flat rather than cylindrical.

The casting temperature is such that the melting point of the Fe-AI-Si alloy is approximately 13
5 and 0 (However, when Si is egg t.% and the mountain is sakaki t.%)
Therefore, it is necessary to cast at a temperature 100 to 400°C higher than this.

If the casting temperature is lower than this, the fluidity of the molten metal will be poor and cavities will easily form. In addition, if it is higher than this, N
There is a large amount of evaporation of components such as, and the composition tends to shift. Note that the columnar structure has a mirror orientation that is easily formed when the mirror temperature is high. This is thought to be because the higher the locking temperature, the larger the temperature gradient at the solidification interface, which makes unidirectional solidification more likely to occur. As described above, the polycrystalline body with uniform crystal orientation used in the present application can be easily manufactured simply by considering the manufacturing conditions as described above, and is more economically advantageous than the method using a single crystal.

Furthermore, as a method to investigate whether the columnar structure of the polycrystalline structure of the Fe-AI-Si alloy is oriented in the <100) direction, the plane perpendicular to the koji direction of the columnar structure is measured by X-ray diffraction. There is a way to do it. In other words, since the plane perpendicular to the <100) direction is the {100} plane, an X-ray diffraction pattern obtained from a columnar structure completely oriented in the <100) direction has a plane index that is an integral multiple of the {100} plane. Only the diffraction peaks corresponding to are obtained. Furthermore, even when some other directions are mixed, the intensity ratio of the plane index that is an integer multiple of the {100} plane is larger than that of the other plane indexes (for example, "X ``Essentials of Line Diffraction;'' by Currity, translated by Matsumura, published by Agne, January 30, 1947, pp. 277-278). The present invention will be explained below with reference to Examples.

Example 1 A predetermined amount of Fe, AI, and Si were weighed and melted in a vacuum melting furnace, and a Fe-AI-Si alloy Rakuyo was cast at a casting temperature of 1700 qo into a soft iron mold whose outside was cooled by a water-cooled pipe. An ingot of Fe-AI-Si alloy with a width of 1.5 mm, a length of 1 mm, and a height of 15 mm was fabricated.

As a result of analyzing the composition of this alloy, it was found that Si was 9.5M. %,
The mountain remains. %, the balance was Fe. As a result of observing the cross section of the ingot, it was found that the portion up to about 3 degrees from the surface in contact with the mold had a columnar structure. This part was cut out by cutting, and the plane perpendicular to the axial direction of the columnar structure was observed by X-ray diffraction. As a result, {200} and {400}
A diffraction peak corresponding to the plane appears strongly, and the intensity ratio between the {200} diffraction peak and the {220} diffraction peak is 1 {20
0}/1{220} was approximately 5. On the other hand, as a result of similarly observing the non-oriented part showing no columnar structure in the central part of the ingot by X-ray diffraction, it was found that 1 {200}/1 {200}
} was about 0.5. From the above, in the columnar structure of the ingot used in this example, the axis directions of the columnar structure are <10
It was revealed that the crystals were strongly oriented so as to coincide with the 0) direction. Using the polycrystalline sendust alloy produced in this way, in which each crystal grain is aligned in the 100> direction,
The magnetic head shown in FIG. 1 was manufactured so that the <100) direction was the tape running direction. FIG. 1a is a view of the head viewed from the tape contact surface, and FIG. 1b is a sectional view. Further, a magnetic head having the same shape as that shown in FIG. 1 was fabricated using a polycrystalline sendust alloy having the same composition and in which the orientation of each crystal grain was random (the sample was taken from the center of the ingot). These magnetic heads were incorporated into a VTR device and a wear test was conducted. The tape used was 7-Fe203 tape. Table 1 shows the wear amount of the magnetic head after 20 hours of tape running. As is clear from the table, a magnetic head using Sendust alloy with aligned <100> directions has 17% less wear than a magnetic head using polycrystalline Sendust alloy with random crystal grain orientation. . In this way, a magnetic head with greater wear resistance than conventional magnetic heads using polycrystalline sendust alloys could be obtained. Table 1

[Brief explanation of drawings]

FIG. 1 is a diagram showing a magnetic head implemented in the present invention. Figure 1

Claims (1)

[Claims] 1 Using a polycrystalline alloy with a composition consisting of 8 to 13% by weight of Si, 4 to 8% by weight of Al, and the balance Fe, the <100> directions of each crystal grain are aligned almost parallel to each other. A magnetic head characterized in that the <100> direction coincides with the tape running direction of the magnetic head.