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(11) | EP 0 086 485 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Wound iron core |
| (57) A wound iron core formed by winding a thin strip of a soft magnetic alloy into a
triodal form, characterized in that a Co-base amorphous magnetic alloy is used as
the thin strip and that the thin strip is annealed in a magnetic field in the direction
of excitation, so that the core exhibits a rectangle ratio Br/B10 of 85% or higher in D.C. hysteresis curve. The Co-base amorphous magnetic alloy has
a composition substantially expressed by: Co100-a-bXaYb where X represents one, two or more elements selected from a group consisting of
Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and
Dy, while Y represents one, two or more elements selected from a group consisting
of B, C, Al, Si, P and Ge, and wherein the following conditions are met: 0≦ a ≦15
(atom%) and 14≦ b ≦30 (atom%). |
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a wound iron core made of a Co-base amorphous alloy and exhibiting a rectangular hysteresis property, as well as a superior soft magnetic property.
[0002] Wound iron cores made of, for example, anisotropic 50% Ni permalloy, supermalloy, directional silicon steel or the like material are finding use in magnetic phase shifters, magnetic amplifiers, D.C. current detectors, magnetic modulators and nowadays in S. W and R of magnetic amplifier control system. As is well known, these conventional wound iron cores have a large rectangle ratio Br/B10 in the B-H hysteresis curve. Recently, however, there is an increasing demand for a wound iron core which exhibits not only a large rectangle ratio Br/B10 but also a small coercive force Hc.
[0003] In S. W and R of magnetic amplifier control system, the wound iron core is used at a high frequency of an order of several tens of kilohertz (KHz) or higher. The 50% Ni permalloy, which is one of the conventionally used materials, exhibits a coercive force Hc which is as large as 0.1 Oe to cause a large loss in the core resulting in a large heat generation. This gives a rise to a demand for a wound iron core having a rectangle ratio Br/B10 equivalent to that of the 50% Ni permalloy and a coercive force Hc smaller than that of the same.
[0004] Among the wound iron cores used hitherto, the core of permalloy system such as of 50% Ni permalloy, supermalloy and so forth has a high sensitivity to strain of the magnetic material, so that the magnetic property is deteriorated seriously due to mechanical strain incurred during handling, transportation and winding or coiling thereby making it impossible to attain the expected performance of the wound iron core and the electric balance. In addition, these conventional materials for forming the wound iron core are produceable only through a careful and complicated process having the steps such as melting, ingot making, hot rolling, pickling, cold rolling and so forth, so that the production cost is raised uneconomically.
SUMMARY OF THE INVENTION
[0005] Accordingly, an object of the invention is to provide a less-expensive wound iron core having a rectangle ratio Br/BIO equivalent to that of ordinarily used 50% Ni permalloy and smaller coercive force than the same, while offering various advantages such as superior stability against strain and a high impact resistance, as well as easiness in heat treatment for attaining the rectangular hysteresis property, thereby to overcome the above-described problems of the prior art.
[0006] To this end, according to the invention, a thin sheet of Co-base amorphous alloy is used as the thin sheet having high magnetic permeability for constituting the wound iron core, and this sheet is subjected to an annealing in a magnetic field in the direction of excitation.
[0007] Above and other objects, features and advantages of the invention will become clear from the following description of the preferred embodiment of the invention taken in conjunction with the attached drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The attached sole Figure shows a D.C. hysteresis curve as obtained with a wound iron core of the invention formed from a Co-base amorphous alloy strip, in comparison with that exhibited by a wound iron core made from a conventional Fe-base material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0009] Generally, a Co-base amorphous alloy exhibits a magnetostriction of zero or substantially zero and, hence, a small magnetic anisotropy in the quenched state, which in turn facilitates the uniform and unidirectional magnetization by an external magnetic field during the annealing which is conducted under the influence of the magnetic field to attain a superior rectangular hysteresis property. It is, therefore, possible to attain a distinguished rectangular hysteresis property much more easily than in the case where an amorphous Fe-base alloy which tends to exhibit a large magnetostriction is used as the material. The small magnetostriction permits also a reduction in the coercive force down to a level below 1/10 of that presented by ordinarily used 50% Ni permalloy and below 1/2 of that presented by ordinarily used amorphous Fe-base alloy.
[0010] Hitherto, the Co-base amorphous alloy has been used mainly as the material of magnetic heads. No proposal nor attempt has been made up to now as to the use of the Co-base amorphous alloy in place of the 50% Ni permalloy as the magnetic core for would iron core, by realizing a rectangular hysteresis property through an annealing in a magnetic field parallel to the direction of the exciting current.
[0011] The present inventors have found that a wound iron core simultaneously exhibiting a large value of the rectangle ratio Br/B10 and a low coercive force Hc is obtainable by a process which has the steps of preparing an amorphous alloy having a composition expressed by Co100-a-aXaYb, where X represents one, two or more elements selected from a group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Ru, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, while Y represents one, two or more elements selected from a group consisting of B, C, Al, Si, P and Ge, particularly an amorphous alloy specified above satisfying the conditions of 0 < a < 15 and 14 < b < 30, annealing the amorphous alloy in a magnetic field and, after a cooling, winding the alloy into the form of an iron core.
[0012] In the composition of the amorphous alloy used in the invention, the total content of the element or elements Y serving as an amorphous structure former should range between 14 and 30 atom %, because the amorphous structure cannot be formed when the Y content is less than 14 atom % and when the same is 30 atom % or greater. Metalloid or semimetal elements such as C, Si, B, P, Ge and Al are known as elements for forming amorphous structure. However, for attaining a high thermal stability and toughness, it is preferred to use a combination of Si and B. Although the effect of the invention is not affected seriously by the presence of C, P, Ge or Al, the content of such elements is preferably not greater than 5 atom %. When a specifically high resistance to environmental condition, e.g. a specifically high moisture proof or anti-alkali property is required, the B content should be selected to be not greater than 10 atom % but the B content should not be reduced down below 7 atom % for otherwise the amorphous structure will not be obtained. Any Si content less than 10 atom % and not smaller than 20 atom % is not preferred because such an Si content will seriously deteriorate the thermal stability and increase the coercive force undesirably.
[0013] The content of the element X which serves as the transition metal element should be selected to be not greater than 15 atom %, because X content above 15 % undesirably increases the magnetostriction As to a level of 10 x 10 or greater. Elements other than Fe, Ni and Mn, when added by an amount smaller than 15 atom %, reduces the magnetostriction nearly to zero and improves the ability for forming the amorphous structure advantageously. The elements X, particularly Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, improves the hardness and, in addition, provides a higher thermal stability through raising the crystallization temperature.
[0014] The expected rectangular hysteresis property can be obtained also when the Co-base amorphous alloy strip of above-specified composition is annealed in a magnetic field in the direction of excitation which usually coincides with the longitudinal direction of the strip followed by an annealing in a magnetic field. Although direct electric current has been used hitherto for forming the external magnetic field during the annealing, an effect almost equivalent to that produced by the direct electric current is obtainable when an electric current obtained by a half-wave rectification or even alternating current (commercial frequency) is used for the formation of the magnetic field.
[0015] The advantage of the invention will be fully realized from the following description of example.
Example 1
[0016] A Co-base amorphous alloy strip of 55 mm wide was prepared to have a composition expressed by (Co0.94Fe0.06)76.5Si14B9.5. The strip was wound in a substantially troidal form into a wound iron core having an outside diameter of 35 mm and an inside diameter of 25 mm. The wound iron core was subjected to an annealing which was conducted at 320°C for 1 hour in a circumferentially directed magnetic field of 50 Oe. The properties of the thus produced wound iron core are shown in Table 1 and Fig. 1 in comparison with those of wound iron cores produced from conventionally used 50 % Ni permalloy and supermalloy. The wound iron core of Fe-base amorphous alloy appearing in Table 1 and Fig. 1 was made from an alloy having a composition expressed by Fe71Ni10Si10B9 and had been subjected to an optimum annealing conducted in a magnetic field of 50 Oe as in the case of the iron core of the invention.
[0017] From Table 1, it will be seen that the wound iron core of the invention formed from Co-base amorphous alloy exhibits a superior rectangle ratio Br/B10 of 96%, and a coercive force which is as small as less than 1/10 of that exhibited by the iron core formed from conventionally used 50% Ni permalloy.
1. A wound iron core formed by winding a thin strip of a soft magnetic alloy into
a troidal form, characterized in that a Co-base amorphous magnetic alloy is used as
said thin strip and that said thin strip is annealed in a magnetic field in the direction
of excitation, so that said core exhibits a rectangle ratio Br/Bio of 85% or higher in D.C. hysteresis curve.
2. A wound iron core according to claim 1, wherein said Co-base amorphous magnetic
alloy has a composition substantially expressed by:
where, X represents one, two or more elements selected from a group consisting of Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, while Y represents one, two or more elements selected from a group consisting of B, C, Al, Si, P and Ge, and wherein the following conditions are met: 0 < a < 15 (atom%) and 14 < b < 30 (atom%).
where, X represents one, two or more elements selected from a group consisting of Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, while Y represents one, two or more elements selected from a group consisting of B, C, Al, Si, P and Ge, and wherein the following conditions are met: 0 < a < 15 (atom%) and 14 < b < 30 (atom%).
3. A wound iron core according to claim 1, wherein said Co-base amorphous magnetic
alloy has a composition substantially expressed by:
where, X represents one, two or more elements selected from a group consisting of Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, and wherein the following conditions are met: 0 ≦ a ≦ 15 (atom%), 10 ≦ b ≦ 20 (atom%) and 7 ≦ c < 10.
where, X represents one, two or more elements selected from a group consisting of Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy, and wherein the following conditions are met: 0 ≦ a ≦ 15 (atom%), 10 ≦ b ≦ 20 (atom%) and 7 ≦ c < 10.