JPH01269208A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain the magnetic head having excellent reproduction sensitivity and corrosion resistance by forming a magnetic head core of an alloy which has a prescribed compsn. and in which the number of crystals grains per mm<2> sectional area is <=250 pieces. CONSTITUTION:This magnetic head has the compsn. contg. 3-12wt.% Cr and 0.5-8wt.% Si and consisting of the balance Fe and unavoidable impurities. In addition, the head is formed of the alloy in which the number of the crystals grains per 1mm<2> sectional area (the average value when measurement is made at 10 points with 100 times magnification) is <=250 pieces. This magnetic head is capable of executing good magnetic recording even with a magnetic recording medium having high coercive force of >=2,000Oe and has the excellent reproduction sensitivity and corrosion resistance; for example, the head has the tendency to additionally enhancing the coercive force of the magnetic layer for the purpose of protecting recording data; in addition, the magnetic head adequate as a magnetic head for magnetic cards for which the use environment is abuse is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic head suitable for a recording/reproducing system of a high coercivity magnetic recording medium such as a magnetic card.

(Prior Art) In recent years, magnetic cards have come into widespread use for various purposes, such as cash cards, telephone cards, ID cards, program cards for various computers, and data cards. As described above, as magnetic cards are used more and more, the coercive force of the magnetic layer used is increased in order to increase the reliability of magnetic cards against external magnetic fields, that is, to prevent recorded data from dropping out. There is a growing tendency to do so. For example, the coercive force of the magnetic layer used in current cash cards is around 8000 e, which is about twice as high as that of magnetic recording media for audio, etc.; Attempts have been made to use magnetic layers.

Incidentally, conventionally, as magnetic heads for magnetic recording and reproduction of these magnetic cards, those in which a magnetic head core portion is formed of a Sendust alloy (Fe-8l-AJ2 alloy) have often been used. However, in Sendust alloys, the magnetic flux density, for example, the magnetic flux density at 500e,
Since the B50 is as small as about 10 kG, a problem arises in that sufficient magnetic recording cannot be performed on a magnetic recording medium having a magnetic layer with a high coercive force, such as the above-mentioned coercive force of 20,000 e or more.

In order to solve these problems, it is necessary to use a material with high magnetic flux density as the material for the magnetic head core. Here, as a high magnetic flux density alloy that satisfies such characteristics, a permendur alloy (for example, a 2% v-49% Co-balance Fe alloy) is known. However, magnetic heads that use this permendur-based alloy in the magnetic head core can perform good magnetic recording even on high coercive force magnetic recording media by taking advantage of its high magnetic flux density during magnetic recording. However, there is a problem in that the sensitivity during reproduction is low and a magnetic head that exhibits good magnetic properties for both recording and reproduction cannot be obtained.

On the other hand, PE-8L alloy has high magnetic flux density,
Although it has the characteristics of being able to perform relatively good magnetic recording on high coercivity magnetic recording media and has excellent sensitivity during playback, it has the problem of poor corrosion resistance. This was first revealed through experiments and research by the inventors of the present application. In other words, especially in the case of magnetic cards, there are many opportunities for fingers to touch the magnetic layer and get it dirty with sweat or oil, and the environment in which they are used is wide-ranging, including outdoors, in the workplace, and even along roads where dust is flying up. Compared to other magnetic recording media, there are far more factors that cause rust and wear on the magnetic head, such as dirt and oil that adhere to these magnetic cards. Therefore, if the corrosion resistance is low, the contact surface with the magnetic layer becomes rough, the gab width changes, etc., and the recording and reproducing characteristics tend to deteriorate, resulting in a lack of reliability.

(Problems to be Solved by the Invention) As mentioned above, magnetic heads using Sendust-based alloys cannot perform sufficient magnetic recording on magnetic recording media with high coercive force, such as magnetic cards, and have poor corrosion resistance. There was also the problem that it was low.

In addition, although magnetic heads using permendur alloys have excellent magnetic recording characteristics, they have the problem of low reproduction sensitivity; Fe-8i alloys have excellent magnetic recording and reproduction characteristics, but There was a problem of low corrosion resistance and lack of reliability.

This invention was made to address the problems of the prior art, and it enables sufficient magnetic recording on magnetic recording media with high coercive force, such as magnetic cards, and has excellent reproduction sensitivity. The object of the present invention is to provide a magnetic head that has good corrosion resistance and excellent reliability.

[Structure of the Invention] (Means for Solving the Problems) The magnetic head of the present invention first contains 3 to 12% by weight of Cr, 0.5 to 8% by weight of Si, and the remainder is Fe and unavoidable elements. has a composition consisting of specific impurities, and has a cross-sectional area of 1-
The magnetic head core is characterized by being formed of an alloy in which the number of crystal grains per unit (average value when measured at 10 locations at 100x magnification) is 250 or less, and secondly, C
3 to 12% by weight, 0.5 to 8% by weight of Si, Aff
i, Nbq MOSGe5ZrSHf', Co.

Ru5Rhs Pd508% Ir5Pts Lanthanoid rare earth elements, W %Ti, Ta, Mn5Cus
Contains one or more selected from V and N1 in a total amount of 6% by weight or less, with the balance consisting of Fe and unavoidable impurities, and the number of crystal grains per 1 mj of cross-sectional area (magnification 100 The magnetic head core is characterized in that the magnetic head core is formed of an alloy having an average value of 250 or less when measured at 10 locations.

The alloy forming the core of the magnetic head of the present invention contains Cr in an amount of 3 to 12% by weight, preferably 6 to 10% by weight, as a component for improving corrosion resistance. If the Cr content is less than 3% by weight, for example, the corrosion resistance required for a magnetic head for recording and reproducing on a magnetic card that is expected to be used under harsh conditions cannot be obtained;
If it exceeds , the magnetic flux density will decrease.

In addition, 0.5 to 8% by weight, preferably 3 to 8% by weight of St as a component that improves the reproduction sensitivity of the magnetic head.
Contains within the range of If the Si content is less than 0.5% by weight, sufficient reproduction sensitivity for a magnetic head cannot be obtained, and if it exceeds 8% by weight, it may not be suitable for magnetic recording media with high coercive force, such as a coercive force of 20,000 e or more. However, a high magnetic flux density that enables sufficient magnetic recording cannot be obtained, and workability also deteriorates.

In addition to the above-mentioned components, the alloy forming the core of the magnetic head of the present invention contains l, NbSM, and other components that improve workability.
o5 Ge, Zrs Hls 00% RLJ% R
It is possible to contain one or more selected from hs Pd5Oss Ir5Pts lanthanoid rare earth elements, W ST1, Tas Mns Cus V, and Nl in a total amount of 6% by weight or less. however,
If the total content of the above components exceeds 6.0% by weight, the magnetic flux density will decrease and the growth of crystal grains will be hindered, making it difficult to obtain corrosion resistance, so the content should be less than this. Preferably 3% by weight
The content is more preferably 2% by weight or less.

The magnetic head of the present invention is manufactured, for example, as follows.

That is, first, alloy components satisfying the composition ratios of each component listed above are melted and cast, then subjected to hot forging or rolling, followed by repeated cold working and annealing as necessary, followed by cutting or punching. A magnetic head core having a desired shape, such as a block shape or a thin plate shape suitable for a laminate, is manufactured by the above method.

After this, final magnetic annealing is performed at a temperature of 850°C or higher, preferably over too"c, and at appropriate cooling conditions corresponding to the composition. Then, as with a normal magnetic head, a nonmagnetic member is interposed between the gaps. A magnetic head core is prepared, a coil is wound, and the core is inserted into a case made of a high permeability magnetic material such as permalloy, and the inside is filled and solidified with an epoxy resin or the like to obtain a magnetic head.

In the magnetic head of the present invention, among the above manufacturing steps,
Magnetic annealing after finishing the shape of the magnetic head core is an important process. That is, by performing magnetic annealing at a high temperature as described above and under appropriate cooling conditions, the cross-sectional area in (the number of crystal grains per
It is possible to increase the crystal grain size to 250 or less, preferably 100 or less (average value when measured twice), and as a result, the number of grain boundaries, which are the starting point of corrosion, is reduced, resulting in significantly improved corrosion resistance. At the same time, the reproducing sensitivity of the magnetic head is significantly improved. In addition, the number of crystal grains per cross-sectional area 1 is counted as one if all the crystal grains are included in the 100x magnification photograph or in the microscope field, and those in which some crystal grains are included are counted as one. The evaluation was based on a total of 172 pieces, which were measured at 10 locations, and the average value was shown.

Number of crystal grains per 1 mN cross-sectional area (10 at 100x magnification)
If the average value when measured at multiple locations exceeds 250, that is, if the crystal grains are small, sufficient corrosion resistance cannot be obtained, and reliability under severe conditions as described above will decrease.

As mentioned above, the magnetic annealing conditions are as follows:
Annealing is performed at a temperature of 0°C or higher, and at as high a temperature as possible within a range that does not cause problems in terms of shape retention, etc., and the annealing time varies depending on the alloy composition and temperature, but is approximately 0°C.
．． About 1 hour to 10 hours, and the cooling rate is 1000℃
/hour to about 10°C/hour is appropriate.

(Function) In the magnetic head of the present invention, the alloy forming the magnetic head core has extremely excellent corrosion resistance due to its Cr content and the size of its crystal grains, and is suitable for magnetic recording and reproduction of magnetic cards. It has excellent reliability even under the harsh conditions in which it is used. In addition to this property of excellent corrosion resistance, it also has a large magnetic flux density, for example, the magnetic flux density B50 in a magnetic field of 500e is 1.
It has become possible to sufficiently perform magnetic recording on high coercive force magnetic recording media that satisfy 4kG or more, and even 15kG or more, and have a coercive force of 20,000e to 40,000e, and also has excellent sensitivity during playback. It is something.

(Example) Next, embodiments of the invention will be described.

Examples 1 to 10 The alloy components having the compositions shown in Table 1 were melted and cast, hot rolled, and then cut to a shape with an outer diameter of approximately 6 mm
It was processed into a block-like core shape of 10tsX 4mtx and a gap length of 25μ.

Next, each of the core members was magnetically annealed under the conditions shown in Table 1 to produce a magnetic head core.

In addition, for comparison with this invention, we conducted experiments in which the magnetic annealing conditions were changed to change the crystal grain size, and the alloy composition was changed to conventionally used sendust alloys, permendur alloys, Fe alloys, etc. A magnetic head core was produced using a -3i alloy in the same manner as in the above example.

(Left below) Next, the magnetic flux density in the magnetic field of 5008 of each of these magnetic head core materials subjected to appropriate heat treatment・B5
o and the number of crystal grains per cross-sectional area 1i at any position (shown as the average value of measurements taken at 10 locations in an enlarged photograph with a magnification of 100 times). The results are shown in Table 2.

Thereafter, magnetic heads for magnetic cards were manufactured using each of the above magnetic head cores.

Next, each magnetic card magnetic head obtained in this way was attached to a magnetic card recording and reproducing device, and using each of these magnetic card recording and reproducing devices, a coercive force of 28,500
A magnetic card with a magnetic layer of 200+aA, 1
Magnetic recording was performed under kHz conditions. Next, the recorded data was reproduced using the same magnetic head, and the recording characteristics were evaluated based on the output voltage at that time. Furthermore, after recording was performed on the magnetic head using the same magnetic head, reproduction was performed using each magnetic head, and the reproduction sensitivity was evaluated based on the output voltage at that time.

In addition, in order to evaluate the corrosion resistance, these magnetic heads were sprayed with salt water at a concentration of 5% at 35°C for 48 hours, and the playback sensitivity after the salt water spray was measured in the same way as the evaluation of playback sensitivity described above. The rate of decrease in sensitivity was evaluated.

The results of each of these characteristic evaluations are also shown in Table 2.

(Leaving space below) As is clear from the evaluation results of each characteristic shown in Table 2, the magnetic head according to the present invention has a high magnetic flux density and can perform good magnetic recording on a magnetic recording medium with a high coercive force. The playback sensitivity was excellent. That is, it was confirmed that the magnetic head had sufficient magnetic properties as a magnetic recording head and as a reproducing magnetic head, and could be used for both purposes. In addition, it has excellent corrosion resistance and excellent reliability even under severe usage conditions.

On the other hand, among the magnetic heads of the comparative examples, the magnetic heads manufactured using conventionally used alloys cannot perform sufficient magnetic recording on magnetic recording media with high coercive force. Recording characteristics cannot be obtained (Comparative Example 1), magnetic recording is possible but reproduction characteristics are insufficient (Comparative Example 2), magnetic recording and reproduction characteristics are relatively good but corrosion resistance is poor, and harsh usage conditions Each of them had drawbacks, such as a lack of reliability for use under conditions (Comparative Examples 3 and 4). Furthermore, magnetic heads using alloys in which crystal grains were not sufficiently grown (Comparative Examples 5 and 6) were inferior in corrosion resistance and reproduction sensitivity, as well as Comparative Example 3, and lacked reliability.

[Effects of the Invention] As is clear from the above embodiments, the magnetic head of the present invention can perform good magnetic recording on a magnetic recording medium having a high coercive force, such as 20,000 e or more, and also has excellent readability. Excellent sensitivity. To provide a magnetic head which is also excellent in corrosion resistance, for example, has a tendency to further increase the coercive force of a magnetic layer in order to protect recorded data, and is suitable as a magnetic head for magnetic cards which are used in harsh environments. I can do it.

Applicant: Toshiba Corporation Agent Patent Attorney Suyama Sa

Claims (2)

[Claims] (1) 3 to 12% by weight of Cr, 0.5 to 8% by weight of Si
alloy with a composition in which the remainder consists of Fe and unavoidable impurities, and the number of crystal grains per 1 mm^2 cross-sectional area (average value when measured at 10 locations at 100x magnification) is 250 or less A magnetic head characterized in that a magnetic head core is formed of. (2) 3 to 12% by weight of Cr, 0.5 to 8% by weight of Si
, Al, Nb, Mo, Ge, Zr, Hf, Co, Ru,
Contains one or more selected from Rh, Pd, Os, Ir, Pt, lanthanoid rare earth elements, V, Ti, Ta, Mn, Cu, V and Ni in a total amount of 6% by weight or less, with the balance being It has a composition consisting of Fe and unavoidable impurities, and the number of crystal grains per 1 mm^2 cross-sectional area (magnification 1
1. A magnetic head characterized in that a magnetic head core is formed of an alloy having an average value of 250 or less particles when measured at 10 points at a magnification of 0.00 times.