Metal treatment – Stock – Titanium – zirconium – or hafnium base
Patent
1997-11-28
1999-03-23
Sheehan, John
Metal treatment
Stock
Titanium, zirconium, or hafnium base
148671, 420417, C22C 1400
Patent
active
058853758
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a high strength titanium alloy useful as a material for products such as ornaments including watch bodies, watch bands, bracelets, earrings, pendants, necklaces, eyeglass frames; the products made of the titanium alloy; and a method for producing the products.
BACKGROUND ART
Titanium has excellent corrosion resistance and high ratio of strength/specific gravity with no change in color and the like with the elapse of time. Therefore, titanium is expected to be useful as a material for products such as ornaments which a person puts on the body. Especially, in recent years, ornaments are required to be made of biocompatible material which does not cause metal allergy for human body. As titanium is a typical material which does not cause metal allergy, much attention has been focused on titanium as a material for ornaments. Under such circumstances, titanium has been superseding conventional metals such as stainless steel as a material for ornaments.
Ornaments are required to satisfy the requirements such as beauty in appearance, ability of being formed in a complicated and precise shape, and high resistance to getting flawed during the use in daily life. In addition, ornaments are required to have a clear mirror-finished surface which is capable of being formed with various kinds of surface finishings (such as letters written in extremely thin thickness to the extent of hair: hereinafter, referred to as hair-line property). From the viewpoint of machinability, ornaments are required to be produced with a number of minute holes satisfactorily formed therein.
In reality, titanium and titanium alloys used as a material for ornaments, and a method for producing ornaments are derived from the technologies developed in other industrial fields such as aerospace field, chemical industries, and nuclear energy field. Thus-produced ornaments do not necessarily satisfy the required properties.
Industrial pure titanium of JIS-1 series or JIS-2 series is one of the materials which are most commonly used for ornaments. However, the ornaments made of such titanium are easy to get flawed by contact or friction in a daily life, or their surface finishes are worn out. Therefore, the ornaments made of such titanium are inferior to those made of stainless steel in beauty and decorativeness, which are essential properties for ornaments.
As an titanium alloy includes large amount of alloy elements, ornaments made of titanium alloy have increased strength and high resistance to flaw. In this respect, an titanium alloy is superior to industrial pure titanium as a material for ornaments. However, as an titanium alloy is poor in processability, it is difficult to conduct a precise and minute machining thereto, resulting in imposing limitations on designs of ornaments. In addition, almost all titanium alloys include alloy elements such as aluminum, nickel, vanadium, chromium. These alloy elements are poor in biocompatibility, and therefore, not desirable for ornaments. In addition, as these alloy elements are relatively expensive, the material cost becomes high.
Various technologies have been developed for improving the abrasion resistance of industrial pure titanium and the machinability of titanium alloy. However, these technologies are intended for use in the fields other than ornament industries, and therefore, are not applicable to ornaments. For example, Japanese Patent publication No. 7-62196 suggests a titanium alloy having an improved abrasion resistance. In this art, the abrasion resistance of the titanium alloy is improved by dispersing titanium carbide. However, the obtained titanium alloy has too high hardness, resulting in shortening a life of drill which is used in a drilling process of forming minute holes for ornaments. Japanese Patent publication No. 5-42490 suggests a titanium alloy in which inclusions such as sulfide are dispersed for the purpose of enhancing the machinability and free-cutting properties thereof. However, the inclusions are too soft to give the pro
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Enomoto Tadao
Hashimoto Norio
Kushida Hachiro
Taguchi Hideo
Takemura Atsushi
Citizen Watch Co. Ltd.
Kabushiki Kaisha Kobe Seiko Sho
Sheehan John
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