Co-Ni-base alloy

Abstract

A Co—Ni-base alloy, being characterized in that a composition of the alloy comprises at least Co, Ni, Cr, Mo, W and Fe, and percentages by weight of the composition are from 25% to 45% of Co, from 25% to 40% of Ni, from 18% to 26% of Cr, from 3% to 11% of Mo, from 0.5% to 9% of W, wherein a sum of Mo and W is from 4% to 13% by weight, and from 1.1% to 5% of Fe.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Co—Ni-base alloy, and, more particularly to a Co—Ni -base alloy having a high elasticity and a high corrosion resistance for use in a small-size precision device and the like, a mainspring using the Co—Ni-base alloy, and a method for producing the mainspring. 2. Description of the Related Art To date, a Co-base alloy, a Co—Ni-base alloy which is more efficient than the Co-base alloy or the like has been used as a high elastic material for use in a small-size precision device (for example, refer to patent document 1). Further, since a high output torque, durability and corrosion resistance are required for a mainspring of a wrist-watch, the Co-base alloy or the Co—Ni-base alloy which is high in Young's modulus or material strength, excellent in corrosion resistance and has a favorable plastic workability has been used as a material for the mainspring. The Young's modulus of the Co-base alloy...

AI Technical Summary

Benefits of technology

N: number of effective turns of spring; and

As seen from the formula, a material having a high Young's modulus is necessary for obtaining a high output torque without increasing the thickness or width of the spring. Further, the mainspring of the wrist-watch is ordinarily small in size such that the thickness and width thereof are approximately 0.1 mm and 1 mm, respectively. Therefore, it is required that the material for use in the mainspring of the wrist-watch has not only a high Young's modulus, but also a favorable plastic workability property such that it can be machined into a thin narrow hoop (strip-shaped material). For this account, a material which has a high Young's modulus, a favorable plastic workability, a mainspring having a high output torque using the material and a method for producing the mainspring are required. Simultaneously, durability of the mainspring and improvement of corrosion resistance thereof are also required.

According to the present invention, an alloy in which a strengthening element is newly added to a Co—Ni-base alloy to define a composition and, as a result, mechanical strength is remarkably enhanced is provided. It has been found that, in the Co—Ni-base alloy, W alone or a combination of W and Nb was added as a strengthening element to a main elements of Co, Ni, Cr, Mo and the like to newly define a composition range thereof and, as a result, material strength was remarkably enhanced compared with an example of a conventional Co—Ni-base alloy. Further, it has been found that a mainspring having high performance can be obtained by using the Co—Ni-base alloy according to the present invention, performing plastic working so as to have a high Young's modulus in a rolling direction of such rolled material and, after working, performing an age-hardening treatment.

This alloy has a favorable plastic workability and a low stacking fault energy and, accordingly, has a high work hardening ability. When the alloy is subjected to cold-plastic working, fine deformation twins are densely formed in an FCC phase which is the parent phase and the like and, through a subsequent work-hardening, an alloy strength is enhanced. The cold plastic working ratio is preferably 50% or more. Further, a superplastic phenomenon is expressed by the presence of such fine deformation twins.

The Co—Ni-base alloy according to the present invention is enhanced in a material strength compared with the conventional Co—Ni-base alloy. For this account, it is effective to use the Co—Ni-base alloy according to the invention for the spring or the like for the precision device which requires high load, high reliability and high corrosion resistance and, therefore, it has an advantage such that it can correspond to a trend of down-sizing and being free of maintenance thereof and the like. By processing the Co—Ni-base alloy according to the invention, the mainspring having a high output torque, an excellent durability and corrosion resistance can be obtained. When the mainspring according to the invention is used as a power source of the wrist-watch, since a large driving torque can be obtained without enlarging thickness or width thereof, it is possible to increase a moment of inertial of a balance wheel, thereby being capable of decreasing a change of a rate to be caused by a vibration or a shock. Further, diversification of added mechanisms or an increase of duration period of time can be realized. Still further, even when it is repeatedly used, since characteristics thereof are hardly deteriorated, the high output torque can be maintained. It is tough and is hardly broken. Furthermore, even when it is left in a humid environment caused by, for example, a climate, a human perspiration or the like, it performs a high corrosion resistance.

Problems solved by technology

Along with a performance enhancement of a mechanical wrist-watch or a diversification of added mechanisms thereof, a higher output torque has been required for a mainspring which is an energy source, and there is a problem in that a conventional mainspring is insufficient.

However, a space within the mechanical wrist-watch is limited and, accordingly, it is not advantageous to increase thickness or width of the spring.

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