JPS6122020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel amorphous ferromagnetic alloy for magnetic heads that has stable magnetic properties, low magnetostriction, and high saturation magnetic flux density.

A ferromagnetic alloy with low magnetostriction is practical and more desirable for the following reasons.

1 Excellent magnetic properties such as low coercive force and high magnetic permeability,
Generally obtained when magnetostriction approaches zero.

2. If the magnetostriction is zero, the material is insensitive to mechanical strain, and when the material is processed into a desired product, there is no risk of deterioration of magnetic properties due to strain during processing.

3. Electromagnetic devices made of materials with zero magnetostriction do not generate noise even when used with alternating current.

Further, it is desirable that the saturation magnetic flux density be high for the reasons described below.

(1) If the saturation magnetic flux density is high, the same efficiency can be achieved with less material.

(2) Good linearity and suppresses electromagnetic distortion.

Currently, known low magnetostriction crystalline alloys include (a) an Fe alloy containing about 80 at.% Ni, and (b) an Fe alloy containing about 6 wt.% Si. Alloys containing elements such as , Mo, and Al are known.

Alloys represented by b) have a high saturation magnetic flux density and about
Although it is approximately 18kG or more, it is extremely brittle and has only limited practical use. stomach)
The saturation magnetic flux density of alloys represented by is as low as about 7kG, which is also not desirable for practical purposes.

By the way, the results of recent research (C _x Fe _1-x ) aB _b C _c
It is generally disclosed that the amorphous alloy represented by has low magnetostriction and high saturation magnetic flux density.
[For example, Japanese Patent Application Laid-Open No. 105525/1983]. However, here x is 0.84~1.0, a is 0.78~0.85, b is 0.1~
For 0.22, c is 0 to 0.12, and b+C is 0.15 to 0.22
satisfy. This alloy is a strong and very practical material. Typical properties are Co ₇₄ Fe ₆ B ₁₄ C ₆
In the alloy, the saturation magnetic flux density is 11.8kG, and the magnetostriction is 1.
It is about ×10 ^-5 or less. However, our recent research has revealed that there are difficulties in putting this alloy into practical use. When used in environments with temperatures above room temperature, the magnetic properties of this alloy system change,
It was expected that the characteristics would deteriorate after long-term use over several years even at room temperature.

For example, when we measure the DC magnetization characteristics, we find that 150
It can be seen that aging treatment at a relatively low temperature of about °C and for a relatively short time of about 0.5 hours significantly changes its characteristics. Although the saturation magnetic flux density does not change, the coercive force increases by about 2 to 3 times, the magnetic permeability decreases to about 1/5 or less, the residual magnetic flux density also decreases slightly, and the magnetic properties deteriorate. Therefore, it is difficult to say that such an amorphous alloy system is practical.

SUMMARY OF THE INVENTION An object of the present invention is to provide an amorphous alloy for a magnetic head that has low magnetostriction, high saturation magnetic flux density, is strong, has good wear resistance and workability, and has stable magnetic properties.

In order to achieve the above objects, the present invention has the following features:
(Fe _a Ni _b Co _c ) wTzByCx, 0.02a
0.15, 0<b0.3, c=1-a-b, 0<x
<0.2, 0.05<y<0.25, 0.15<x+y<0.25, T is at least one element selected from Cr, Mo, and W and satisfies 0.012z0.05,
The amorphous alloy for magnetic heads is characterized in that w=1-x-y.

Hereinafter, the present invention will be explained in detail with reference to Examples. An amorphous alloy is a solid whose constituent elements are arranged without long-period regularity and have a structure similar to that of a liquid.

In this example, a so-called centrifugal quenching method was used to obtain an amorphous alloy. Other well-known industrial production methods for amorphous alloys include rolling quenching, single-rolling, and the like. In principle, all of these methods involve ejecting raw material molten alloy onto a metal cylinder rotating at high speed, rapidly expanding the surface area, and quenching it at the same time, solidifying it before crystals form to obtain an amorphous alloy. be. According to these methods, a long ribbon-like sample with a thickness of about 10 μm can be easily obtained. Among these methods, the centrifugal quenching method provides a faster quenching rate and a longer cooling time than other methods. Generally, the amorphous state is Fe,
Transition metals such as Co, Ni, Cr and about 20 at.% B, Si
It is already known that it can be easily obtained in an alloy composition consisting of semimetals (called amorphous elements). However, whether or not an amorphous state is actually obtained depends on the cooling rate and cooling time.
Therefore, alloy compositions that are difficult to amorphize using other manufacturing methods can be relatively easily crystallized using the centrifugal quenching method. It goes without saying that the present invention can be applied to other manufacturing methods, but in that case, the composition range that can be made amorphous is somewhat limited.

The metal hollow cylinder for rapid cooling used in this example had an outer diameter of
It is made of copper with a diameter of 40 mm, an inner diameter of 360 mm, and a length of 80 mm ^L. It rotates at a maximum rotation speed of 2500 rpm or less,
Raw materials previously mixed into a desired composition were melted and ejected onto the inner surface of this cylinder. The amorphous nature of the sample thus prepared was confirmed by X-ray diffraction, differential thermal measurement, etc.

_Figure 1 _{shows ,} as _{a comparative example , the} DC _{magnetization characteristics ( B} -H
FIG. These characteristics did not change even after being left at room temperature for about 3 months after production. Furthermore, no change was observed when aging at 150°C for 0.5 hours, and only a slight change in properties was observed after aging at 200°C for 0.5 hours, resulting in improved stability of magnetic properties. Such a stabilizing effect is mainly obtained by adding the Cr element, and the area where the addition is effective is shown in Figure 2. This figure shows (Fe ₀ . ₀₆ Co ₀ .
₉₄ ) In the _{0.8 -W} Cr _W B _0.14 C _0.06 system, the activation energy Q _{, which} is considered to control changes in magnetic properties, is shown with respect to the amount w of Cr added. Activation energy is a value estimated from changes in coercive force of samples aged isochronously at different temperatures, and the rate at which property changes occur is
Since it is considered to be proportional to exp[-Q/RT] (where R is a gas constant and T is an absolute temperature), the larger the value, the more stable it is.

Figure 2 shows that the stabilizing effect is particularly effective when the amount of Cr added is 1.2 at.% or more and 5 at.% or less. A similar stabilizing effect was seen with the addition of transition group elements such as Mo and W;
Cr had the greatest effect, followed by Mo and W, in that order. Furthermore, the addition of these transition metals had the effect of improving corrosion resistance and making it easier to obtain an amorphous state.

The magnetostriction of the amorphous alloy of the above-mentioned comparative example was 1×10 ⁻⁶ or less, the saturation magnetic flux density was also about 10 kG or more, and the coercive force was 30 mOe or less, showing very excellent magnetic properties. Although this amorphous alloy is sufficiently practical, in the present invention, it is further developed for specific purposes.
Addition of Ni provides improved properties. Ni
Like Cr, Mo, and W, addition improves stability and increases magnetic permeability at the same time. For example (Fe ₀ .
₀₆ Co _0.94 ) _0.78 Cr _{0.2 B 0.14} Co _0.06 The effective permeability at _a frequency _{of 500} kHz _{in the} rapidly cooled sample was approximately 1500 (Fe _{0.06 Ni 0.2 Co 0 .94} ) _{0.78Cr0.2B0.14C0.06} The value _{for the} rapidly _{cooled sample} was _{approximately 3000 .} However, care must be taken as the addition of Ni lowers the saturation magnetic flux density.
In order for the new alloy to be superior to conventional practical alloys such as permalloy, the saturation magnetic flux density must be at least 7kG.
This requires that the Ni content be approximately 30 at.% in the combination of the ferromagnetic elements Fe, Ni, and Co contained in the amorphous alloy.

Furthermore, the magnetostriction of an amorphous alloy is mainly determined by the combination of ferromagnetic elements contained therein, and varies somewhat depending on the content of other parts B, C, etc., but the magnetostriction is small (approximately ±5 ×10 ^-6 or less) The practically usable range was that the proportions of Fe, Ni, and Co were each 0.02 or more and 0.15 or less, zero or more and 0.3 or less, and the remainder.

Furthermore, in order to easily obtain an amorphous state,
Metalloid elements such as B, C, P, Si, Al, Ge etc.
It is necessary to include a range greater than 0.15 and less than 0.25. However, small amounts of elements other than B and C tend to lower the saturation magnetic flux density of the alloy, making them not very practical. However, since elements such as Si are useful for achieving an amorphous state more easily, it is actually necessary to determine its content depending on the application. Even in this case, in order to obtain better characteristics than before, it is necessary to set the content so that the saturation magnetic flux density does not drop below 7 kG.

B and C are amorphous elements that are less likely to lower the saturation magnetic flux density of the alloy. In order to obtain an amorphous state relatively easily, the proportions of B and C in the total must each be in a range of more than 0.05 and less than 0.25, more than 0 and less than 0.2, and the total proportion of B and C must be in a range of more than 0.05 and less than 0.25, and was required to be in a range of more than 0.15 and less than 0.25. When only C or a large amount of C is contained as an amorphous element, it is difficult to obtain an amorphous state. On the other hand, if B is the only amorphizing element, an amorphous state can be easily obtained, but B is an expensive element, and replacing it with cheap C is not practical. Very effective. Another benefit of C inclusion is that it generally increases the stiffness of amorphous alloys, which leads to improved wear properties. The Vickers hardness of an alloy without C substitution is 700 to 800, while the Vickers hardness of an alloy with a suitable amount of C substitution is 1000 or more. Furthermore, the wear resistance is approximately twice as strong when C is substituted.

It goes without saying that the properties of the amorphous alloy of the present invention can be further improved by conventionally known methods such as heat treatment in a magnetic field.

[Brief explanation of the drawing]

Figure 1 shows the DC magnetization characteristics of amorphous alloys in comparative examples, and Figure 2 shows the amount of Cr added to amorphous alloys in other comparative examples and the activation energy that is thought to control changes in magnetic properties. FIG.

Claims (1)

[Claims] 1 (Fe _a Ni _b Co _c ) wTzByCx, 0.02
a0.15,0<b0.3,c=1-a-b,0
<x<0.2, 0.05<y<0.25, 0.15<x+y<0.25
An amorphous alloy for a magnetic head, in which T is at least one element selected from Cr, Mo, and W and satisfies 0.012z0.05, and w=1-xy-z.