JPS58204154A - Corrosion-resistant alloy with high saturation magnetic flux density and high magnetic permeability - Google Patents

Abstract

PURPOSE:To obtain a corrosion-resistant alloy with high saturation magnetic flux density, high magnetic permeability and enhanced acid resistance, by adding a small amount of Ti to an Fe-Si-Al alloy and by regulating the amount of S among the impurities in the alloy. CONSTITUTION:This corrosion-resistant alloy with high saturation magnetic flux density and high magnetic permeability consists of, by weight, 4-12% Si, 3-8% Al, 0.1-1.0% Ti and the balance essentially Fe or further contains 0.02-0.5% Ru. The amount of S remaining in the alloy is regulated to 3-30ppm. Ti is added to passivate the alloy surface. Since the alloy contains reduced amounts of S and sulfide which form rusting spots when the alloy is exposed to an oxidizing atmosphere for a long time, pitting corrosion can be prevented. The alloy has superior acid resistance and high magnetic flux density, so it is suitable for use as the material of the core of a magnetic head.

Description

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

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

Conventionally, magnetic herad core is used as a gravel material.

Permalloy, soft ferrite, etc. are used,
Permalloy has poor wear resistance, and soft ferrite has a low saturation magnetic flux density.

Recently, metal tapes, vapor-deposited tapes, etc. have become popular as magnetic recording media with high recording density in the audio and VTR fields.Furthermore, in the VTR field, narrower tracks and narrower gap lengths are progressing. magnetic flux density.

That is, the magnetic flux density (
B below. ) is required to be 9,300 Gauss or higher, and a magnetic core is required that also has wear resistance.

Fe-8t-AA magnetic alloy has recently been attracting attention as a magnetic material that makes up for all of the deficiencies of Sokote, permalloy, and ferrite, and also satisfies the above requirements.

Although the Fe-8t-AL 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), the binder of the magnetic tape dissolves, and the distilled water changes to UpH=3.7, making it acidic. For this reason, when Fe-81-AA magnetic alloy is used as the head core material, the core is constantly exposed to an acidic atmosphere due to sliding contact with the magnetic tape, and corrosion occurs over long periods of use. If corrosion occurs on the sliding surface of the magnetic tape, tape running will be hindered and the tape will be damaged. Ta. Due to the phenomenon of corrosive wear, the wear resistance is significantly deteriorated, resulting in further spacing loss and a reduction in output.

In general, the corrosion resistance of iron alloys is based on the passivation phenomenon,
In order to obtain high corrosion resistance, it is best to form a strong passive film on the entire surface. 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 completely overcome this drawback, C, N,
It is necessary to reduce impurity elements such as P and S.

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

The present inventors have discovered that the corrosion resistance of the Fe-8i-AL 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-8t-AA magnetic alloy, it has been impossible to suppress localized corrosion called pitting corrosion caused by impurities. The present inventors have discovered that the impurity that causes pitting corrosion in such Fe-8t-AA magnetic alloys is mainly S, and that the amount of S is 6
It has been found that when the content is 0 ppm or less, local corrosion of the Fe-8t-AA magnetic 3-alloy due to pitting corrosion can be significantly improved.

The present invention has been made based on the above-mentioned new findings.

That is, the first invention of the present invention is an alloy consisting of 4 to 12% Si (by weight, the same hereinafter), 3 to 8% AA, 1 to 10% TiD, and the balance substantially Fe; The amount of S remaining in B is 3 to 30 ppm, and the corrosion resistance in an acidic atmosphere is excellent. It is a corrosion-resistant, highly saturated magnetic flux density, and high magnetic permeability alloy having a magnetic flux density of 9,300 Gauss or more.

Moreover, the second invention is Si4-12%, AA3-8 ratio.

TiO, 1-1.0%, RuO, 02-0.5%
and a corrosion-resistant high saturation magnetic flux density alloy in which the balance is substantially composed of Fe, the amount of S remaining in the alloy is 3 to 30 ppm, and has excellent corrosion resistance in an acidic atmosphere and a Blo of 9600 Gauss or more. It is a high magnetic permeability alloy.

In the present invention, 5iU7-10% is optimal, but k
From the relationship of 456 to 12 mm, the lower limit is set to 456,000,000,000.
The upper limit was set at 12%. The optimum amount of AtO is 4 to 6%, but since it has sufficiently good characteristics even in the range of 3 to 8 qb, the lower limit is set to 6% in total and the upper limit is set to 8%.

Ti is added to passivate the alloy surface, and if the amount added is less than 0.1%, the effect will be small;
If Ti exceeds 0%, Ti precipitates at grain boundaries, causing intergranular corrosion and lowering B+ok, so the amount added is set to 0.1 to 1.0%.

Corrosion resistance is further improved. Ru addition amount is 0.0
If it is less than 2%, the effect of addition is small and there is no big difference from the case of adding Ti alone. Moreover, even if it is added in an amount exceeding 0.5%, it is difficult to see any further improvement in corrosion resistance.

Addition of 0.02-0.5% is sufficient.

The form of corrosion of Fe-8i-AA magnetic alloys in an acidic atmosphere starts with pitting caused by S and sulfides remaining in the alloy, 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, by setting the amount of S remaining in the alloy to 3 to 30 ppm, pitting corrosion can be completely prevented. S amount 'r3
It is industrially difficult to reduce the content to less than ppm,
If it exceeds 30 ppmffi, pitting corrosion cannot be prevented even if the alloy surface is made passivated by Ti or Ti and Ru.

By the way, since most of the S amount remaining in the alloy is brought in from the uFe raw material, it is sufficient to reduce the S amount in the uFe raw material in order to reduce the amount of S to one alloy.

Fe raw materials used industrially contain 50 to 1100
Since ppm of S is present, even if this Fe raw material is vacuum melted, about 40 to 80 ppm of S remains in the alloy. Therefore.

First, by melting only the Fe raw material and performing flux treatment and refining, high-purity iron with an S content of 30 ppm or less is produced, and when Fe-8i-AA magnetic alloy is melted using this high-purity iron, it becomes an alloy. It is possible to reduce the amount of S remaining therein to 30 ppm or less.

Next, examples of the present invention will be described.

Normal Fe raw material with S content of 8[lppm] 50 to 2
was dissolved in an argon gas atmosphere to form At15I/ffi
Deoxidize by adding 65% Cab-15% C.
Apply a flux consisting of aF2-20 To At, o3 so that the surface of the molten metal is always covered with the flux.

It was added three times or more over a period of 30 minutes. Table 1 shows the results of a complete analysis of the S and O contents of the Fe raw material refined in this way.

Table 71: Obtaining high-purity iron with low S content:
It is possible to produce Fe-8i using this high-purity iron raw material.
- If the A7 magnetic alloy is melted in the same manner as the conventional method, it is possible to reduce the amount of S remaining in the two alloys to 30 ppm or less.

Table 2 shows the composition, magnetic properties and acid resistance test results of various alloys. In addition, 1 alloys 1 to 3 are comparative examples with S content 'i30
It is not adjusted to less than ppm, and the alloy 2 is 4 to 20
is an example of the present invention.

The dimensions of the test pieces are as shown below, and each test piece is subjected to a specified heat treatment before its magnetic properties are measured.

and was subjected to acid resistance tests.

The test piece for measuring magnetic properties has an outer diameter of 8mm, an inner diameter of 4mm, and a thickness of 0.
．． The test piece for the acid resistance test had a diameter of 3 degrees and a thickness of 5 mm.

The acid resistance test used a 20% hydrochloric acid aqueous solution (30°C).

The test piece was immersed in this solution for 1 minute, and the evaluation method was a comparison of the number of pitting corrosion occurring per 1α.

As is clear from Table 2, if the amount of S exceeds 30 ppmi, even if Ti or Ti and Ru are added,
The number of pitting corrosion (goods) in crn atashi is significantly high.

When the amount of S is set to 30 ppm or less, the number of pitting corrosion per crn hole is significantly improved to 10 or less. for example.

Alloy No. 13 (S = 4 ppm) has a pitting corrosion count of 2 per 1 by adding 0.3 Ti and Ru each.
It is individual.

As a result, 0.1 to 1.0% of Ti was added to the Fe-8i-At alloy.
0% content and the amount of S remaining in the alloy is 3 to 30 ppp
It is clear that a value in the range of m is the optimum value for improving acid resistance;
It is clear that the acid resistance is further improved by containing 0.02 to 0.5%.

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.

Agent (71η) Patent Attorney Go M Yosuke =11-288-

Claims (1)

[Claims] 1. Si 4-12%, At 5-8%, Ti 0.
1. A corrosion-resistant, high saturation magnetic flux density, high magnetic permeability alloy, characterized in that the alloy consists of 1 to 1,0% and the remainder substantially Fe, and the amount of S remaining in the 9 alloy is 3 to 30 ppm. 2. Si 4-12%, At 3-8%, Ti 0.2% by weight.
A highly saturated corrosion-resistant alloy characterized by an alloy consisting of 1 to 1.0% Ru, 0.02 to 0.5% Ru, and the balance substantially Fe, and the amount of S remaining in the alloy is 3 to 30 ppm. Magnetic flux density high permeability alloy.