JPS6150133B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a Fe-Si-A magnetic alloy, and more particularly to a high saturation magnetic flux density and high magnetic permeability alloy for use in a magnetic head core, which has excellent corrosion resistance in an acidic atmosphere, that is, acid resistance. In general, the characteristics that magnetic materials for magnetic head cores should have are good wear resistance against sliding of the magnetic recording medium, high saturation magnetic flux density to completely magnetize the recording medium, and magnetic permeability related to the sensitivity of the magnetic head. It has high magnetic flux, low coercive force to prevent magnetization by the recording medium, and excellent corrosion resistance because it can be used in any environment. Hitherto, permalloy, soft ferrite, and the like have been used as magnetic materials for magnetic head cores, but permalloy has poor wear resistance, and soft ferrite has the disadvantages of 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.
As the track and gap length are becoming narrower in the field, high saturation magnetic flux density, that is, magnetic flux density at an applied magnetic field of 10 oersteds (hereinafter referred to as
A magnetic head core material is required that has a B ₁₀ ) of 9300 Gauss or more and is also wear resistant. Therefore, Fe-
Si-A magnetic alloys have recently attracted attention. Fe−
Although the Si-A magnetic alloy has excellent magnetic properties as a head core material, it has a problem in that it does not have sufficient corrosion resistance because the main element is Fe. By the way, if a magnetic recording medium, especially a magnetic recording tape, is immersed in distilled water (PH=7) for 24 hours, the binder of the magnetic tape will dissolve, and distilled water has a pH of 3.7.
It changes to a certain extent and becomes acidic. For this reason, when Fe--Si--A 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 due to long-term use. When corrosion occurs on the magnetic tape sliding surface of the core, tape running is hindered, and wear resistance is significantly deteriorated due to a phenomenon called corrosive wear, which further causes spacing loss and a reduction in output. Generally, the corrosion resistance of iron alloys is based on the passivation phenomenon, and in order to obtain high corrosion resistance, it is preferable 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, it is necessary to reduce the amount of impurity elements such as C, N, P, and S present in the alloy. 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-Si-A 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-Si-A magnetic alloy, it has been impossible to suppress localized corrosion called pitting corrosion caused by impurities. Previously, the inventors
The impurity that causes pitting corrosion in such Fe-Si-A magnetic alloys is mainly S, and the amount of S is
We proposed to significantly improve the local corrosion of Fe-Si-A magnetic alloys caused by pitting corrosion by reducing the weight ratio to ~30ppm (the same applies hereafter) (Japanese Patent Application No. 57-85433), but in that case, It was difficult to reduce the amount of S to 3 ppm or less. Then add S to 3ppm
As a result of repeated research aimed at the following, it has become possible to industrially produce a Fe-Si-A magnetic alloy with an S content of 3 ppm or less using the method described below. It has been discovered that local corrosion can be significantly improved by doing so, leading to the present invention. That is, the first invention of the present invention is that Si4 to 12%,
An alloy consisting of A3 to 8%, Ti 0.1 to 1.0%, and the balance substantially Fe, the amount of S remaining in the alloy is 3 ppm or less, has excellent corrosion resistance in an acidic atmosphere, and has B ₁₀ It is a corrosion resistant high saturation magnetic flux density high magnetic permeability alloy with a magnetic flux density of 9300 gauss or more. Moreover, the second invention is Si4~12%, A3~8
%, Ti 0.1-1.0%, 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, has excellent corrosion resistance in an acidic atmosphere, and _B10 is a corrosion resistant high saturation magnetic flux density high magnetic permeability alloy with a value of 9300 Gauss or more. In the present invention, the optimum Si content is 7 to 10%, but due to the relationship between A, Fe, etc., it has sufficiently good magnetic properties even in the range of 4 to 12%, so the lower limit is set to 4.
%, with an upper limit of 12%. The optimum amount of A is 4 to 6%, but even in the range of 3 to 8%, the properties are sufficiently good, so the lower limit is set to 3% 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, and if it exceeds 1.0%, Ti will push out to the grain boundaries and cause intergranular corrosion. The amount added was set at 0.1 to 1.0% since it was a factor in lowering _B10 . Ru added in the second invention is also an effective element for passivating the alloy surface, and corrosion resistance is further improved by adding 0.02 to 0.5% Ru and Ti in combination than by adding Ti alone. 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. Moreover, even if it is added in an amount exceeding 0.5%, it is difficult to see any further improvement in corrosion resistance, and addition of 0.02 to 0.5% is sufficient. Corrosion of Fe-Si-A magnetic alloys in an acidic atmosphere begins with pitting corrosion, where S and sulfides remaining in the alloy serve as rust points, 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 rust points. In other words, the amount of S remaining in the alloy is 3ppm.
If the following conditions are met, pitting corrosion can be almost completely prevented. S
Although pitting corrosion can be prevented to some extent even if the amount is 3 ppm or more, it is still insufficient. By the way, most of the S amount remaining in the alloy is Fe.
Since it is brought in from the raw material, in order to reduce the amount of S in the alloy, it is sufficient to reduce the amount of S in the Fe raw material. Since 50 to 100 ppm of S exists in Fe raw materials used industrially,
Even if this Fe raw material is vacuum melted, there is no
Approximately 40 to 80 ppm of S remains. Therefore, first Fe
By melting only the raw materials and performing flux treatment and refining, high-purity iron with an S content of 30 ppm or less is produced, and this high-purity iron is further used to produce Fe-Si-A.
If the alloy is refined in the same manner as above, it is possible to reduce the amount of S remaining in the alloy to 3 ppm or less. Next, embodiments of the present invention will be described. 50 kg of normal Fe raw material with an S content of 80 ppm is dissolved in an argon gas atmosphere, 15 g of A is added to perform deoxidation, and then 65% CaO - 15% CaF ₂
A flux consisting of -20% A ₂ O ₃ was added three times or more within 30 minutes so that the surface of the molten metal was always covered with the flux. This is how it was refined
Table 1 shows the results of analyzing the S and O contents of the Fe raw material.

[Table] It is possible to obtain high-purity iron with a low S content from this, and using this high-purity iron, Fe-Si-A
The alloy was melted by flux refining as described above. Table 2 shows the results of analyzing the S and O contents of the Fe-Si-A alloy at this time.

[Table] By melting the Fe-Si-A alloy in this way, it is possible to reduce the amount of S remaining in the alloy 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 5 to 21 are examples of the present invention. The dimensions of the test pieces are as follows, and each test piece was subjected to a prescribed heat treatment and then subjected to measurement of magnetic properties and an acid resistance test. The test piece for measuring magnetic properties has an outer diameter of 8 mm and an inner diameter of 4 mm.
mm, thickness 0.2mm, and the acid resistance test specimen is 30mm in diameter.
It was 5mm thick. Acid resistance test uses 20% hydrochloric acid aqueous solution (30℃).
The evaluation method was to immerse it in this for 1 minute ^.
This is a comparison of the number of pitting corrosion (N) that occurs around each part. As is clear from Table 3, when the S amount exceeds 3 ppm, the number of pitting corrosion (N) per ^cm2 is significantly high even if Ti or Ti and Ru are added, but when the S amount is reduced to 3 ppm or less, As a result, N is significantly improved to 2 or less. For example, alloy number 12, 14,
16 and 21 have an S amount of 3 ppm or less, and also have Ti and Ru.
By adding , the number of pitting corrosion per cm ² becomes 0, and it can be seen that there is no corrosion at all when immersed in a 20% hydrochloric acid aqueous solution (30°C) for 1 minute. As a result, 0.1 to 1.0% Ti was added to the Fe-Si-A alloy.
It is clear that it is optimal for the amount of S contained and remaining in the alloy to be 3 ppm or less in order to improve acid resistance, and furthermore, if the amount of S remaining in the alloy is 3 ppm or less, Ru should be added to 0.02 to 0.5 ppm.
%, it is clear that the acid resistance is further improved.

【table】

[Table] As described above, according to the present invention, it is possible to obtain an alloy having excellent acid resistance and high magnetic flux density because of the above-described structure. The alloy according to the invention is therefore suitable for use as a magnetic head material.

Claims (1)

[Claims] 1% by weight: Si4~12%, A3~8%, Ti0.1~
1. A corrosion-resistant, high saturation magnetic flux density, high magnetic permeability alloy, characterized in that the amount of S remaining in the alloy is 3 ppm or less, the alloy consisting essentially of 1.0% Fe and the remainder Fe. 2 Weight%: Si4~12%, A3~8%, Ti0.1~
1.0% Ru, 0.02-0.5% Ru, and the balance substantially consists of Fe, and the amount of S remaining in the alloy is
Corrosion resistant high saturation magnetic flux density high magnetic permeability alloy characterized by less than 3ppm.