JPS5920451A - Alloy for core of head for vtr picture - Google Patents

Abstract

PURPOSE:To obtain an alloy for the core of a head for a VTR picture provided with high saturation magnetic flux density and superior wear resistance by combinedly adding specified amounts of Cr and Nb to a ternary Fe-Al-Si alloy. CONSTITUTION:This alloy consists of, by weight, 5-11% Si, 3-9% Al, 5-8% Cr, 0.05-0.5% Nb and the balance Fe. The alloy is obtd. by adding said specified amounts of Cr and Nb to a prescribed Fe-Al-Si alloy, and by adding Cr and Nb, a very thin, dense and strong oxide film with superior adhesive strength is formed at high temp. Since the alloy has superior wear resistance as the material of the core of a head for a VTR picture, it can contribute largely to the improvement of technique using a small-sized portable magnetic recording device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alloy for a core that has a high saturation magnetic flux density and exhibits excellent wear resistance as a rad core for VTR images.

Recently, following the spread of home VTRs, research and development of small portable type VTRs equipped with cameras is progressing.

In order to obtain clear images under conditions where the relative speed between the tape and the head is high, this small double-type VTR uses a metal tape with a high coercive force that can record short wavelengths. The head core C2 is made of single-crystal ferrite, which is currently in practical use. Sendas (Fe-AI-8i ternary alloy) is considered the most promising. However, since this alloy has inferior wear resistance compared to FERA (Jl2), attempts have been made to improve the wear resistance by adding several special elements.

In order to develop Radcore for VTR images with excellent wear resistance, the present inventors have conducted research on Sendust's wear resistance (C = influence of various additive elements).
The wear mechanism of RAD core is completely different from that of audio cassette decks and card readers, and the core alloy that exhibits excellent wear resistance in audio cassette decks and card readers is RAD core. It has been found that this method has no effect at all in the case of

That is, in the case of audio cassette decks and card players, C2 has a fairly good correlation between the hardness of the core and the abrasion resistance (-), and it is said that general C2 hard abrasives cause less wear. For example, Fe-Al-8i ternary alloy Flea 2 B
, Ti, Zr, and other elements added singly or in combination to increase the hardness of the alloy are used as Fe-Al-8 as heads in audio cassette decks and card readers.
It has much better wear resistance than five-component alloys.

However, when used in a rad core for VTR images, no such effect of improving abrasion resistance is observed, and in some cases, the abrasion resistance may be reduced.

Fe-A plate-8i ternary alloy with B alone or Ti4yZr
The alloy added in combination with the core of a card reader shows 5 to 6 times better wear resistance than the Fe-Al-Si ternary alloy, but when used as a rad core for VTR images, the wear resistance is As the core of an audio cassette deck, its wear resistance is also related to its corrosion resistance against leachate from the tape, and generally speaking, the better the corrosion resistance, the less wear it will cause. In the case of Fe
- Adding approximately 0.1 to 1 Q wt% of Ru to the Al-Si ternary alloy, alone or in combination with other elements, improves wear resistance by 2 to 3 times as a core for audio cassette decks and card readers. However, this remarkable difference in abrasion resistance is due to the fact that the wear mechanism of the VTR image rad core is completely different from that in other cases. It seems to be.

In other words, wear in the case of a card reader is caused by direct abrasion of the core surface by the card (2).Therefore, the harder the card, the less wear there is.In the case of an audio cassette deck, wear is caused by direct abrasion of the core surface by the tape. This occurs due to corrosion of the core surface due to the moisture contained in the tape component.Therefore, the harder the tape and the better its corrosion resistance to leachate, the less wear it will cause.On the other hand, in the case of RadCore (- is Because the sliding speed of the tape is much higher than in other cases, the core surface is extremely hot compared to card readers and audio cassette decks.
=, an oxide film is formed on the core surface 42, and this is polished by the tape. In such a cVTR image rad core, the core surface is not directly scraped off, but an oxide film is formed, which is worn away, and wear progresses indirectly.

Therefore, as a rad core to a VTR image, F e -A
l-Si ternary alloy (instead of adding elements that provide good resistance to hardness and tape leachate (C2), elements that form a dense, strong, and adhesive oxide film at high temperatures are added. It is estimated that it is necessary to do so.

The present invention is based on the above findings and considerations (C), and as a result of further investigation, we have developed an alloy for VTR image rad cores that has a high saturation magnetic flux density and exhibits excellent wear resistance.

8is~11wt% (hereinafter wt% is simply abbreviated as duck) AI
3-9%, Cr5-8%, Nb 0.05-0.5
%, pertains to alloys with the balance consisting of Fe.

That is, the present invention adds various elements to a Fe-Al-Si ternary alloy to improve the properties and adhesion of the high-temperature oxide film formed.
As a result of research on the
When added in combination with l+5 to 0.5%, an extremely thin, dense, strong, and highly adhesive high-temperature oxide film is produced, and it can be used as a rad core for VTR images, significantly compared to the conventional Sendust core@C2. (2) It has excellent wear resistance.

However, in the present invention, the alloy composition is limited as described above for the following reasons (2).

The reason why we limited the A1 content to 3 to 9% and the Si content to 5 to 11% is because the AI father is able to maintain magnetic properties even if either of 8i is below the lower limit or exceeds the upper limit. This is because the value of .mu.e) decreases significantly, making it unusable for rad cores for VTR images.

Also, the Or content is 5-8% and the Nb content is 0.05-8%.
The reason for limiting the content to 03% is that if either Cr or Nb is less than the lower limit, no improvement in wear resistance will be observed, whereas if it exceeds the upper limit, the saturation magnetic flux density (Bs) or effective magnetic permeability will decrease, and the metal tape This is because it becomes impossible to respond to

Hereinafter, the alloy of the present invention will be explained in detail with reference to Examples.

999% purity electrolytic iron, 99.99% purity AI, 99.99% purity 3i, 99.9% purity Cr and purity 9
9.9% Nb was mixed in various proportions (two formulations) and this was melted using high frequency vacuum melting XF" (vacuum lf3~
10XIO-"Hg), and a cast iron mold (25mm thick, 25mm wide) of the composition shown in Table 1C:
An ingot of length IFIOI+)11 was obtained. These ingots were subjected to electric discharge machining, wire cutting, and sobbing C2, and a ring for measuring magnetic properties with an outer diameter of 8 mm, an inner diameter of 4 m, and a thickness of 3.2 mm was used. Fin, length 2.
Three test pieces for abrasion resistance measurement were prepared in eight containers, and after heat-treating them in vacuum at a temperature of 100° C. for 1 hour, magnetic properties and abrasion resistance were measured.

These results are also listed in Table 1.

There are four measuring rings for magnetic properties (two B-H).
Tracey (Draw a B-H curve from 2, calculate the saturation magnetic flux density CBS) and coercive force (HC), and further calculate the C2LC
The effective magnetic permeability (μe
) was measured.

In addition, the micro Vickers hardness was measured using one test piece for wear resistance C, and the remaining two test pieces were attached to a brass head board C2, and the sliding surface was Polished to a curvature of .5m++H (installed on a VTR,
A wear test was conducted for 100 hours under the following conditions, and the amount of wear was measured using a microscope.

A VHS type VTR was used, a test piece was made to protrude 45 μm from the side of the head cylinder/dar, and a TDK Avirile tape was used, and this was applied at a rate of 5.5 μm per second. It was slid at a speed of FIIlml.

As is clear from Table 1, all of the alloys of the present invention have much improved wear resistance compared to conventional alloys without significantly deteriorating their magnetic properties. Even when compared to the best of these, it can be seen that it has more than five times the wear resistance.

In contrast, comparison alloys with lower Cr or Nb contents than the composition range of the invention alloys do not exhibit any improvement in wear resistance, and also have Cr or Nb contents lower than the composition range of the invention alloys. It can be seen that with many comparative alloys, the saturation magnetic flux density is significantly lowered, and Radcore C2 cannot be used for VTR images.

As described above, the C2 alloy of the present invention has a high saturation magnetic flux density and excellent wear resistance as a rad core for VTR images, and can be applied to a rad core for VTR images, and can be used as a rad core for VTR images. This has a remarkable effect that greatly contributes to the improvement of recording technology.

Claims (1)

[Claims] s+5~lxwt%, A13~9wt%, Cr5~8w
t%, Nb01) 5~Q, 5 w 1%, balance Fe for VTR image rad core alloy