JPS5976855A - Corrosion resistant alloy having high saturation magnetic flux density and high magnetic permeability - Google Patents

Abstract

PURPOSE:To obtain an alloy having high saturation magnetic flux density, high magnetic permeability and improved corrosion resistance in an acidic atmosphere by specifying the amounts of Fe, Si, Al and Ti contained in an alloy and by regulating the amount of S remaining in the alloy. CONSTITUTION:This corrosion resistant alloy having high saturation magnetic flux density and high magnetic permeability consistis of, by weight, 4-12% Si, 3-8% Al, 0.1-1.0% Ti and the balance essentially Fe. The alloy may further contain 0.02-0.5% Ru, and the amount of S remaining in the alloy is regulated to <=3ppm. The alloy has improved acid resistance and high magnetic flux density because of Ti added alone or Ti and Ru added combinedly and the restricted S content. The alloy is suitable for use as the material of a magnetic head, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Fe-8t-AA magnetic alloy, and particularly to a high saturation magnetic flux density and high magnetic permeability alloy for magnetic cores that has excellent corrosion resistance in an acidic atmosphere, that is, acid resistance.

In general, the characteristics that magnetic materials for magnetic helad cores should have are:
It has good wear resistance against sliding of the magnetic recording medium, high saturation magnetic flux density to completely magnetize the recording medium, high magnetic permeability related to the sensitivity of the magnetic head, and high coercive force to prevent magnetization by the recording medium. Furthermore, it has excellent corrosion resistance so that it can be used in any environment.

Conventionally, permalloy, ferrite, etc. have been used as magnetic materials for magnetic head cores, but ferrite has poor wear resistance, and soft ferrite has a low saturation magnetic flux density. ing.

Recently, metal tape has been used as a magnetic recording medium with high recording density in the O7" and VTR fields.

As vapor-deposited tapes and the like are becoming more widespread, and narrower tracks and narrower gap lengths are progressing in the VTR field, high saturation magnetic flux density, that is, magnetic flux density at an applied magnetic field of 10 Oe (hereinafter referred to as B10), is 9300 Gauss or higher. There is a demand for a magnetic head core material that has both wear resistance and wear resistance.

Fe-81-At is a magnetic material that compensates for the shortcomings of Sokote, Nokumalloy, and ferrite and also satisfies the above requirements.
Magnetic alloys have been attracting attention recently. Although the Fe-8t-At magnetic alloy has excellent magnetic properties as a hesodo core material, there is a problem in that the corrosion resistance is insufficient because the main element is Fe.

By the way, when a magnetic recording medium, especially a magnetic recording tape, is immersed in distilled water (pH = 7) for 24 hours, the magnetic tape becomes
Ingu dissolves and the pH of the distilled water changes to about 3.7, becoming acidic. For this reason, li'
When an e-8t-At magnetic alloy is used as the head core material, the core is constantly exposed to an acidic atmosphere due to sliding with the magnetic tape, resulting in corrosion over long periods of use. If corrosion occurs on the magnetic tape sliding surface of the core, tape running will be hindered, and the wear resistance will be significantly degraded due to the phenomenon of corrosion wear, which will further lead to spacing loss and reduce output. This is based on the passivation phenomenon, and in order to obtain high corrosion resistance, it is best to form a strong passive film. However, even if a passive film is formed, it has a major drawback of being susceptible to localized corrosion called pitting corrosion. Therefore, in order to overcome this drawback, C2 present in the alloy must be
It is necessary to reduce impurity elements such as N, P, and S.

Among these, S in particular significantly deteriorates corrosion resistance, so it is necessary to reduce S as much as possible.

The present inventors have discovered that the corrosion resistance of the Fe-3i-At magnetic alloy is also similar to that of the above-mentioned general iron alloy. That is, even if an alloying element that forms a passive film is added to the Fe-8i-At magnetic alloy, it has been impossible to suppress localized corrosion called pitting corrosion caused by impurities. Previously, the present inventors discovered that the impurity that causes pitting corrosion in such Fe-8i-At magnetic alloys is mainly S.
It was proposed that localized corrosion of Fe-81-At magnetic alloy due to pitting corrosion could be significantly improved by reducing the amount to 3 to 30 ppm (weight ratio, same hereinafter) (Japanese Patent Application No. 1983).
7-85433), but in that case it was difficult to reduce the amount of S to 3 ppm or less.

After that, we conducted repeated research to reduce the S content to 3 ppm or less.

li'e-8 with an S amount of 3 ppm or less by the method described below
It has become possible to industrially manufacture i-At magnetic alloys. It was discovered that by doing so, local corrosion could be significantly improved, leading to the present invention.

That is, the first invention of the present invention has Si of 4 to 12%.

An alloy consisting of 3 to 8 inches of At, 11 to 1.0 inches of TiO, and the remainder substantially Fe, the amount of S remaining in the alloy is 3 ppm or less, and has excellent corrosion resistance in an acidic atmosphere. It is a corrosion-resistant, high saturation magnetic flux density, and high magnetic permeability alloy with B+O of 9300 Gauss or more.

Moreover, the second invention is Si4-12th and At3-8th.

T r 0.1-1.09' t Ru 0.02-0
．． 5% and the balance substantially consists of Fe, the amount of S remaining in the alloy is 3 ppm or less,
Excellent corrosion resistance in acidic atmosphere and BIO of 930
In the present invention, Si is a corrosion-resistant high saturation magnetic flux density high magnetic permeability alloy having a magnetic flux density of 7 to 10 Gauss or more. , % is optimal, but due to the relationship between At, Fe, etc., it has sufficiently good magnetic properties even in the range of 4 to 12%, so the lower limit is set to 4.

The upper limit is set at 12 inches. The optimum amount of AA is 4 to 6 parts, but since it has sufficiently good properties even in the range of 3 to 8 parts, the lower limit is set to 3 parts and the upper limit to 8 parts.

Ti is added to passivate the alloy surface, and if the amount added is less than 0.1%, the effect will be small;
, Of6 is exceeded, Ti is pushed out to the grain boundaries and becomes a cause of intergranular corrosion and causes a decrease in 13+o. Therefore, the amount added was set to 0.1 to 1.0 Ti.

Ru added in the second invention is also an effective element for passivating the alloy surface, and is more effective than Ti alone.
Corrosion resistance is further improved by adding 2 to 0.5 Ti in combination. When the amount of Ru added is 0.02% or less, the effect of addition is small and there is no significant difference from the case of adding Ti alone. 0 again
It is difficult to see any further improvement in corrosion resistance even if more than 5.0% is added (addition of 0.02 to 0.5% is sufficient.

The form of corrosion of Fe-8i-At magnetic alloys in an acidic atmosphere starts with pitting caused by S and sulfides remaining in the two alloys, and progresses to full-scale corrosion when exposed to an acidic atmosphere for a long time. It is. Therefore, in order to prevent pitting corrosion, it is necessary to reduce S and sulfides in the alloy, which cause pitting corrosion.

That is, if the amount of S remaining in the alloy is 3 ppm or less, pitting corrosion can be almost completely prevented. Although pitting corrosion can be prevented to some extent even if the S content is 3 ppm or more.

It is still insufficient.

By the way, most of the amount of S remaining in the alloy is brought in from the Fe raw material, so in order to reduce the amount of S in one alloy, it is sufficient to reduce the amount of S in the Fe raw material. Fe raw materials used industrially contain 50 to 1100 pp
Since S exists in the alloy, even if this Fe raw material is used for vacuum melting, about 40 to B Oppm of S remains in the alloy. Therefore, first, only the Fe raw material was melted and then fluxed and refined to produce high-purity iron with an S content of 30 ppm or less.

Furthermore, when a Fe-8t-At alloy is refined in the same manner as above using this high-purity iron, the amount of S remaining in the alloy is reduced to 3.
It is possible to reduce the amount to less than ppm.

Next, examples of the present invention will be described.

50 kg of normal Fe raw material with S content of 80 ppm
was dissolved in an argon gas atmosphere to form AA15. ! 17 was added to perform deoxidation, and then 65% CaO-15
A flux such as %CaF2-20% Az2o3 was added so that the surface of the molten metal was always covered with the flux.
It was added three times or more in 0 minutes. Table 1 shows the results of analyzing the S and O contents of the refined Fe raw material.

Table 1 It is possible to obtain high-purity iron with a lower S content than this, and using this high-purity iron, Fe-3i-At alloy was produced by flux refining in the same manner as above.

Table 2 shows the results of analyzing the S and 0 contents of the Fe-8i-A1 alloy at this time.

Table 2 When the Fe-8t-At alloy is melted in this manner, it is possible to reduce the amount of S remaining in the two alloys to 3 ppm or less.

Table 3 shows the composition, magnetic properties, and acid resistance test results of various alloys thus prepared. Alloys 1 to 4 are comparative examples in which the S amount was not adjusted to 3 ppm, and Alloys 9 and 5 to 21 are examples of the present invention. The dimensions of the test piece are as shown below.

After each test piece was subjected to prescribed heat treatment, magnetic properties were measured.
and was subjected to acid resistance tests.

The test piece for measuring magnetic properties has an outer diameter of 8 mm and an inner diameter of 4 mm.
The test piece for acid resistance test is 0.2m thick and has a diameter of 30mm and a thickness of 5mm.
It was ffl+++.

The acid resistance test was conducted using a 20% hydrochloric acid aqueous solution (30° C.) and immersed in this for 1 minute, and the evaluation method was a comparison of the number of pitting corrosion (N) occurring in lz2 adashi.

As is clear from Table 3, when the amount of S exceeds 3 ppm, the number of pitting corrosion (N) per cm2 is extremely high even if Ti or Ti and Ru are added. When it is set below, N is significantly improved to 2 or less. For example, 1 alloy number 12, 14, 16.2
1 has an S content of 3 ppm or less, and by adding Ti and Ru, the pitting corrosion number of 1crn2 becomes O.

It can be seen that immersion in a 20% hydrochloric acid aqueous solution (30° C.) for 1 minute caused no corrosion at all.

As a result, Ti was added to the Fe-8t-A7 alloy by 0.1 to 1.
It is clear that a S content of 0% and an amount of S remaining in the alloy of 3 ppm or less is optimal for improving acid resistance! l), 4 and further Ru from 0.02 to 0.
It is clear that the acidity is further improved by containing 5%.

As described above, according to the present invention, it is possible to obtain an alloy having excellent acid resistance and high magnetic flux density since it is constructed as described above. Therefore, the alloy according to the present invention is suitable for use as a magnetic head material.

Claims (1)

[Claims] 1. St 4-12% by weight, At 3-8%, Ti
1. A corrosion-resistant, high saturation magnetic flux density, high magnetic permeability alloy, characterized in that the alloy consists of 1 to 1.0% O, and the balance substantially Fe, and the amount of S remaining in the two alloys is 3 ppm or less. 2. Si 4-12%, At 3-8%, Ti in weight%
O, 1-1. An alloy with high corrosion resistance, high saturation magnetic flux density, and high permeability, characterized in that the alloy consists of O%, Ru0.02 to 0.5%, and the balance substantially Fe, and the amount of S remaining in the two alloys is 3 ppm or less. magnetic alloy.