JPS58123854A - Corrosion resistant alloy with high magnetic flux density - Google Patents

Abstract

PURPOSE:To enhance the pitting corrosion resistance of an Fe-Si-Al alloy without deteriorating the magnetic characteristics of so-called ''Sendust '' by adding Ru to the alloy and by restricting the S content. CONSTITUTION:This alloy consists of, by weight, 4-12% Si, 3-8% Al, 0.02- 0.5% Ru, 0.0003-0.0030% S and the balance Fe. It has superior resistance to corrosion due to salt water and >=9,000 G magnetic flux density at 10 Oe. By adding Ru, an acid-proof passive film is formed on the material surface. Compounds of S with impurities such as Ca, Mg and Mn contained in Fe by traces, that is, sulfides concentrate on the grain boundaries and act as rust forming points. Accordingly, only the addition of Ru does not produce a significant effect of enhancing the corrosion resistance. By restricting the S content, the effect of Ru can be shown furthermore.

Description

[Detailed description of the invention] The present invention relates to iron-silicon-aluminum alloys.

In particular, the present invention relates to an alloy with high magnetic permeability and high magnetic flux density that has excellent resistance to salt water corrosion, especially pitting corrosion.

In general, the characteristics that magnetic materials for magnetic head cores should have are good wear resistance against sliding of the magnetic tape, high saturation magnetic flux density and magnetic permeability related to the electromagnetic conversion characteristics of the magnetic head, and prevention of magnetization by the magnetic tape. It has a low coercive force and excellent corrosion resistance.

However, conventional magnetic materials for magnetic helad cores include permalloy and soft ferrite.Permalloy and permalloy have poor wear resistance, and soft ferrite has the disadvantage of having a low saturation magnetic density.

Furthermore, recently, with the appearance of alloy tapes (so-called metal tapes) having high coercive force as magnetic recording media, magnetic herad core materials having a saturation magnetic flux density of 9000 Gauss or more, preferably 9300 Gauss or more are required.

Therefore, Fe-8i-A/Fe-8i-A/
Alloys have been attracting attention recently. This alloy has excellent magnetic properties for use in head cores, but the main element is F.
Since it is E, there is a problem of insufficient corrosion resistance. In other words, magnetic heads are rather rarely used under controlled environments; for example, magnetic heads are used in cassette tape recorders, VTR1
They are often used in natural environments such as automatic ticket gates and automatic teller machines, and in extreme cases, they may be used in atmospheres containing salt or corrosive gases.

In addition to being used as a magnetic head, there are many opportunities to come into contact with aqueous solutions during the manufacturing process (6) of manufacturing magnetic heads from raw materials, and for the same reason as above, the magnetic head due to rusting of the KFe-8i-Al alloy Accidents during the head manufacturing process and when using magnetic heads have become a major problem. Rust in magnetic heads often occurs at the boundary between the core and case or resin, and especially when rust occurs between the gap spacer and other dissimilar metals or near the boundary with resin, it can significantly impede the reliability of recorded and reproduced information. This manifests itself in malfunction of the device, deterioration in sound quality, and significant decrease in output.

In view of this, the present invention mainly proposes a seed alloy that improves the corrosion resistance against pitting corrosion without impairing the magnetic properties of the Fe-8i-AI alloy so-called "Sendust" alloy (registered trademark). purpose.

The present invention has a weight ratio of silicon S14 to 12, aluminum A 13 to 8, ruthenium LI 0.02 to 05, sulfur S 0.0003 to 0.0030, and the balance iron! It is a high magnetic flux density alloy that is made of carbonaceous material, has excellent corrosion resistance against salt water corrosion, and has a magnetic flux density of 9000 Gauss or more at a magnetization strength of 10 oerste.

Here, the optimal amount of AI is 5 to 7%, but S+%F
From the relationship of e, etc., the magnetic properties are sufficiently good even in the range of 3 to 8 inches, so the lower limit is set to 3 inches and the upper limit is set to 8%.

The optimum amount of Si is 8 to 10 inches, but even 4 to 12% has sufficiently good characteristics, so the lower limit is set to 4 inches and the upper limit is set to 12 inches. The Ru content has a positive effect on corrosion resistance, but this effect is not visible when the Ru content does not reach 0.02%, and when the Ru content exceeds 0.5%, the magnetic flux density BIO
is less than 9000 Gauss, so the lower limit of Ru is 0.02
%, with an upper limit of 0.5%. S causes impurities and sulfide compounds in the iron raw material to form at the grain boundaries, and when this becomes a starting point for corrosion, small pitting corrosion occurs there. For this reason, it is better to reduce S as much as possible, but according to research by the inventors, when Ru is contained in the Fe-8i-A1 alloy, S is 0.0003" to 0.003" when Ru is present. % was found to be optimal for magnetic properties and corrosion resistance.As a result, the lower limit of S was 0.0003, and the upper limit was 0.003.
It was hot.

The reason why Sendust alloy contains Ru and S is as follows. The addition of Ru forms an acid-resistant passive film on the surface of the material. S and Fe contain a small amount of impurities (for example, Ca1Mg).

(Mn, etc.), that is, sulfides, accumulate at grain boundaries, and this becomes a starting point. Adding Ru alone has little effect on improving corrosion resistance. By suppressing the amount of S within a certain range, the effect of adding Ru can be further exhibited.

Example 1 98 Chi 5i-6,0% A containing 0.005 wt% S
/-20 when 0.05T of Ru is added to F'e alloy
% chloride ion aqueous solution immersion test, the number of pitting corrosion per 1 cJ was 750, which is the same number as in the case without the addition of Ru, and no improvement in corrosion resistance could be achieved.

About 0.003% of L/Si power @ 0.05%
When Ru is added, the number of pitting corrosion per lc- is significantly improved to 5.

In addition, if the value is less than 015%, 0.
By adding 0.2% Ru, the number of pitting corrosion per cf is 0 to 7, which improves the corrosion resistance. A pitting corrosion number of 10/hard/cd or less has not been achieved with conventional alloys of this type, and the composition of the present invention improves corrosion resistance when applied to magnetic heads, increasing its practical value. I think it's big.

Example 2 Table 1 shows the results of the composition and magnetic properties of Fe-8i-Al containing Ru and S as its main components. All samples have an outer diameter of 10 mm, an inner diameter of 6111 m, and a thickness of 0 and 2.
The size was mm. As is clear from this table.

Magnetic flux density Bl at 100e. , coercive force Hclo and effective magnetic permeability μe at 0,3 kHJi.

As a result, the magnetic properties were not impaired at all even when Ru was added.
I understand that.

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In this case, it is necessary to conduct continuous testing for several tens to 100 hours, which has the disadvantage that evaluation takes time. In other words, salt water resistance is chlorine ion resistance, so 1
The inventors devised a method (accelerated test) in which a test piece is immersed in an aqueous chloride ion solution as a simple method for evaluating salt water resistance. This test had a correlation with the salt spray test in terms of rust development. Therefore, in this example, salt water resistance was evaluated.

The method was determined by the number of pitting corrosion per cIll. The alloy used in the test was 8i9, 8% by weight, AJ5.9-6
．． 0% by weight, [LuO ~ 0.5% by weight, SO, 0O03
~0.03% by weight of Fe remains. The test properties were as follows: chlorine ion concentration of an aqueous solution containing chlorine ions: 20%, test temperature: 35°C, immersion time -1 minute.

Figure 1 represents the results of such a test. The figure is I
It shows the distribution of the number of pitting corrosion in the sample in relation to the amount of Lu and the amount of S.

As is clear from Fig. 1, if Ru is not included, a large number of pittings occur, whereas even if S is 0.0002% by weight or less, the number of pittings is 100/c [ For the above reasons, no practical value can be found in terms of corrosion resistance. Furthermore, even if the S content is o, oos% or more, the corrosion resistance will not improve.

As a result, the Fe-8i-k1 alloy contains H, u, and S at the same time, and moreover, Ru is 0.02 to 0.5 and S is 0.
It is clear that a range of 0.0003% to 0.003% is the optimum value for improving corrosion resistance.

As described above, according to the present invention, since the structure is as described above, an alloy having excellent corrosion resistance and a high magnetic flux density can be obtained. Therefore.

By applying the alloy according to the present invention as a magnetic head material, it has effects such as being able to withstand use in harsh environments.

[Brief explanation of the drawing]

Figure 1 is a diagram used to explain the pitting corrosion of an example of the alloy of the present invention. Agent Yoshi Akiyama

Claims (1)

[Claims] Silicon 4-12% by weight, aluminum 3-8% by weight, ruthenium 0.02-0.5% by weight, sulfur 0.0003-
A corrosion-resistant high magnetic flux density alloy having 0.0030% by weight, balance iron, excellent corrosion resistance against corrosion based on salt water, and a magnetic flux density of 9000 Gauss or more at 10 oersted.