JPS5831388B2 - High permeability alloy - Google Patents

Description

Detailed Description of the Invention At present, in analog and digital magnetic recording and reproducing devices, high-grade machines that require particularly high reliability use mainly high-grade materials such as single crystal ferrite or hot-pressed ferrite as the core material of the magnetic head. Density ferrite is used.

However, these high-density soft ferrites are extremely difficult to process, produce so-called ferrite noise peculiar to ferrite heads, and have an extremely low magnetic flux density of 4,000 to 5,000 G at most. Not only is it unsuitable for magnetic tape, but it also has a number of drawbacks, such as distortion of the recording waveform due to magnetic saturation at the tip of the core.

On the other hand, the so-called sendust alloy whose main composition is 9.6% Si, 15.4% Aff, and the balance Fe is μ〇235.0
00, Hc=0.020e, Bs=11000G, and has excellent soft magnetic properties, and the specific electrical resistance ρ is also ρ-80μQ
cm, which is relatively high, and can be said to have favorable electromagnetic properties as a core material for a magnetic head.

Furthermore, these Sendust alloys have better workability than ferrite, and Sendust heads using them exhibit excellent head characteristics without any so-called ferrite noise.

An alloy consisting of 9.62% Si, 75.38% A, and the balance Fe has an initial magnetic permeability of 35,000. Maximum permeability 120,00
0, coercive force 0.0220e, saturation magnetic flux density 10000
G.

It has excellent soft magnetic properties, high magnetic flux density, and relatively high specific electrical resistance with a specific electrical resistance of 80 μQcm (Journal of Japan Institute of Metals, No. 3 (1937), p. 127). It can be said that it has ideal magnetic properties as a core material.

That is, permalloy, soft ferrite, etc. are currently used as magnetic heads for analog and digital magnetic recording and reproduction, but the former has problems with wear resistance, and is only partially put into practical use. Abrasion-resistant permalloy has a drawback in terms of magnetic flux density.

On the other hand, soft ferrite has problems with its workability, produces so-called ferrite-specific noise, and, like wear-resistant permalloy, is inferior in terms of magnetic flux density.

In contrast, the so-called sendust alloy, which has a composition of 9.6%5i-5.4%M-balance Fe, has no problems with magnetism as described above, and has excellent workability and durability during use. The failure rate due to breakage is also better than that of ferrite, and although it is somewhat inferior to ferrite in terms of wear resistance, it is significantly superior to permalloy-based products, so it is gradually gaining popularity. It is being put into practical use.

In particular, recently, as magnetic tapes with large coercive force are being put into practical use for high-density, highly reliable recording and reproduction, expectations for these sendust-based alloys are particularly high in terms of wear resistance and magnetic flux density.

Nowadays, magnetic heads are generally used under extremely harsh environmental conditions.

Only a few magnetic heads are used in controlled environments; for example, cassette tape recorders, automatic ticket gates at railway stations, automatic cash dispensers, etc. are generally used in natural environments, and in extreme cases. exposed to salt, moisture, or corrosive gases for long periods of time.

A magnetic head has a precisely controlled gap of about 1 to 1.5 microns in a part of the head core in order to exchange information with a recording medium, and is essentially a precision machined part.

On the other hand, most conventional magnetic heads have been made using permalloy.

This is due to permalloy's good soft magnetic properties and excellent workability, but in addition, it can also be attributed to its excellent corrosion resistance and chemical resistance.

Permalloy as a core material for magnetic heads is mainly used by JI.
It is equivalent to S-PC material and contains approximately 80% Ni, 1
It usually contains about 5% Fe and small amounts of Mo, Mn, etc., and has good corrosion resistance.

Further, in some cases, it also contains Cu, which further increases corrosion resistance, so that the corrosion resistance or chemical resistance as a whole is significantly excellent.

However, the so-called Sendust alloy (1) is an alloy whose composition consists mostly of Fe, and its corrosion resistance and chemical resistance are significantly inferior, so if it is used in the harsh natural environment as mentioned above, it may cause so-called rust. Many accidents occurred due to this, and it became a big problem in practical use.

When incorporated into a magnetic head, rust mainly occurs around gear parts that are easily exposed to outside air, and can significantly impede the reliability of recorded or reproduced information, resulting in equipment malfunction, deterioration in sound quality, and significant output loss. It may appear as a decline.

In order to improve the basic problems of sendust as described above, the authors invented and proposed an alloy containing Cr and Ni (Japanese Patent Application Laid-Open No. 5O-119298), but
As a result of research into single additions, we were able to invent a new alloy with excellent corrosion resistance and magnetic properties.

In the present invention, by adding Cr alone, the corrosion resistance of conventional sendust can be significantly improved without impairing its excellent magnetic properties.

That is, the weight ratio is Si6 to 12, A19 to 12 (excluding 9), and the remainder is mainly Fe, and Cr is added to 1 to 1.
It is a high magnetic permeability alloy characterized by the addition of 0%.

The composition range of the alloy of the present invention was determined for the following reasons.

That is, Cr has a great effect in significantly improving the corrosion resistance of the alloy of the present invention, but if the amount is less than 1%, the effect is not obvious, and if the amount exceeds 10%, the magnetic permeability decreases. Either case is not practical because the magnetic flux density decreases significantly.

On the other hand, a composition consisting of 9.6%5i-5,4%Al-balance Fe is known as the composition in which conventional sendust exhibits the highest magnetic permeability (H, Masumoto: Sci
.

Rep, Fohoku Imp, Univ, 388'
36), when Cr is added to the F=-8i-AA alloy system, the Fe, Si, and Al compositions that give the highest magnetic permeability shift to the higher Al side.

In this case, the amount of Al is 9 to 10% from the viewpoint of magnetic properties.
However, the above range was determined because it has a sufficiently good magnetic permeability even in the range of 9 to 12% (excluding 9) from the relationship with Si and other alloying elements.

The optimal amount of Si is 7.5 to 8.5%, but 6 to 8.5% is optimal.
Since the magnetic permeability is sufficiently good even in the range of 12%, the lower limit is set to 6% and the upper limit is set to 12%.

9.6%5i-5,4%Al-
This figure shows how corrosion resistance and effective magnetic permeability change when Cr is added to an alloy with the remainder being Fe.

As can be seen from the figure, as the amount of Cr added increases, the rust area ratio in the salt spray test becomes significantly better, but on the other hand, the effective magnetic permeability decreases rapidly.

On the other hand, when 4% Cr is added in Fig. 3, Sl and A
7 shows how magnetic permeability changes depending on the amount.

Further, FIG. 4 shows the Fe-8i-A1 composition range in which the effective magnetic permeability is maximum when 2.4% and 7% Cr is added.

As can be seen from Figures 3 and 4, by adding Cr, the composition range where the magnetic permeability increases is higher than that of Al.
You can see it moving to the side.

Examples based on the present invention will be described below.

Note that the present invention is not limited to the examples.

In the example alloy, raw materials were weighed to a desired composition ratio, melted in a high frequency induction melting furnace, and then cast in Ar.

After that, the future 10φ-6 is made by electrical discharge machining or machining.
A ring sample for magnetic measurement of φ and a plate sample for corrosion resistance test of 30 mrn×30 were obtained.

Table 1 shows the magnetic properties and corrosion resistance test results of the materials obtained by the above treatment.

Here, the magnetic property is the effective magnetic permeability μe at IKHz
, lKH2 and the magnetic flux density B1o(T) at an applied magnetic field of 100e (-8e OAm-1).

Furthermore, the corrosion resistance test is expressed as a percentage of the rust area ratio to the sample surface area when 5% saline was sprayed at 35°C for 24 hours.

As can be seen from Table 1, the surface of the conventional Sendust alloy (sample 413) was 100% covered with rust after a 24-hour salt spray test, but the corrosion-resistant Fe- It can be seen that the Si-Al-Cr alloys (samples/161 to 13) have excellent corrosion resistance and magnetic properties comparable to those of conventional materials.

As described in detail above, the corrosion-resistant high permeability alloy according to the present invention not only has extremely excellent corrosion resistance, but also has magnetic properties comparable to conventional materials, making it a great candidate for industrial effectiveness. It is something.

[Brief explanation of the drawing]

Figure 1 (ts) shows the relationship between the amount of Cr added and the rust area ratio, Figure 2 shows the relationship between the amount of Cr added and the effective permeability, and Figure 3 shows the relationship between the amount of Al and Si and the effective permeability. FIG. 4, a diagram showing the relationship between magnetic permeability, is a diagram showing the composition range in which the effective magnetic permeability is maximum.

Claims (1)

[Claims] 1 Weight ratio: Si 6-12%, A19-12% (9
A high magnetic permeability alloy characterized in that 1 to 10% of Cr is added to an alloy consisting of Fe as the balance (excluding Cr).