Alloys or metallic compositions – Copper base – Zinc containing
Reexamination Certificate
2000-04-14
2002-01-22
Yee, Deborah (Department: 1742)
Alloys or metallic compositions
Copper base
Zinc containing
C420S482000, C420S489000, C148S434000, C148S436000
Reexamination Certificate
active
06340446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nickel-free white copper alloy having excellent strength, hardness, ductility, workability and corrosion resistance, suitable for use in elements, sliders, stoppers or the like for slide fasteners, or accessories such as metallic buttons, fasteners or the like for clothes, causing no allergic problem and having high whiteness.
2. Description of the Prior Art
As conventional copper alloys, for example, for the above-mentioned fasteners, copper-nickel-zinc alloys such as nickel silver, which has a white alloy hue, or copper-zinc alloy represented by red brass or brass have been used. Since nickel silver contains nickel as an alloying element, corrosion resistance is excellent. However, for example, where this is applied to the use as a slide fastener, the fastener often contacts with a skin, and there arises the allergic problem due to nickel. Whereas the copper-zinc alloy represented by red brass or brass does not cause such an allergic problem since it contains no nickel. However, its color tone becomes yellowish, and a white alloy cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a white copper alloy having excellent strength and hardness equal to those of nickel silver, as well as excellent workability, corrosion resistance and whiteness in addition to ductility, and having no allergic problem because the alloy contains no nickel.
The present invention comprises the following (1)-(5).
(1) A nickel-free white copper alloy represented by the general formula: Cu
a
Zn
b
Mn
c
Al
d
, wherein b, c, and d are 0.5≦b<5, 7≦c≦17 and 0.5≦d≦4 in terms of % by weight; and a is the balance, the alloy incidentally including unavoidable elements.
(2) A nickel-free white copper alloy, represented by the general formula: Cu
a
Zn
b
Mn
c
Al
d
X
e
, wherein X is at least one element selected from the group consisting of Si, Ti and Cr; b, c, d and e are 0.5≦b<5, 7≦c≦17, 0.5≦d≦4 and 0<e≦0.3 in terms of % by weight; and a is the balance, the alloy incidentally including unavoidable elements.
(3) The nickel-free white copper alloy as described in the above (1) or (2), wherein the b, c and d are 0.5≦b4, 7≦c≦15 and 0.5≦d≦2 in terms of % by weight.
(4) The nickel-free white copper alloy as described in any one of the above (1), (2) and (3), wherein the alloy is a single &agr;-phase state at room temperature.
(5) The nickel-free white copper alloy as described in any one of the above (1), (2) and (3), wherein the alloy has such a color tone that a* value and b* value representing a color tone defined by JIS Z 8729 are 0<a*<5 and 7<b*<15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the composition of the present invention, Zn has an effect of improving the mechanical properties of the alloy through its solid solution strengthening effect and also a cost reduction effect of the alloy. If the Zn content is less than 0.5%, the cost reduction effect and the strengthening effect are insufficient. If the content is more than 5%, the solid- solution coexistence temperature range becomes broad and macro segregation tends to be marked. Also, heat conduction and castability tend to decrease. Further, when the Zn content is larger than 5%, season cracking resistance deteriorates and also the crystalline structure becomes an &agr;+&bgr; phase, so that a sufficient cold-workability cannot be secured. By setting to 5% or less, the problem of season cracking does not occur and a more stable state can be maintained even if the X element defined in the aforesaid general formula Cu
a
Zn
b
Mn
c
Al
d
X
e
is added. 4% or less is more preferred. Mn has effects in providing improved mechanical properties to the alloy by the solid solution strengthening effect and also in cost reduction of the alloy. Further, by addition of Mn in the above-specified amount as a partial replacement of zinc, there occur the effect of improving the season cracking resistance as well as the effect of preventing the color tone of the copper alloy from turning to yellowish excessively. Further, it has an effect of lowering the melting point of the alloy, thus improving the castability and also suppressing vaporization of zinc from a melt. If it is less than 7%, the color tone becomes yellowish. Conversely, if it is larger than 17%, the crystal structure becomes an &agr;+&bgr; phase, so that a sufficient cold-workability cannot be secured. The upper limit of Mn is more preferably 15%.
Al has an effect of improving the season cracking resistance by forming a stable oxide film on the alloy surface. Further, it improves the mechanical properties of the alloy through the solid solution strengthening effect and also decreases the cost of the alloy. The lower limit of the Al amount is 0.5%. When the amount is too small, the season cracking resistance and the strengthening effect become insufficient. On the other hand, if it is larger than 4%, the crystalline structure becomes an &agr;+&bgr; phase, so that a sufficient cold-workability cannot be secured. 2% or less is more preferred.
The Element X (at least one element selected from the group consisting of Si, Ti and Cr) in the general formula Cu
a
Zn
b
Mn
c
Al
d
X
e
serves to form a coating on a melt surface during melting, and also serves to prevent oxidation of Mn and vaporization of Zn. Further, by forming a stable oxide coating on the alloy surface, there occur the functions of preventing elimination of Mn during annealing and improving the season cracking resistance and also the effect of preventing change in color tone with the lapse of time due to oxidation of Mn. The lower limit of the amount of the element X is more than 0%. However, if the amount is too small, the above effects are not sufficiently obtained. Therefore, the amount is preferably 0.02% or more. If the amount is larger than 0.3%, an intermetallic compound is formed with elements in the composition, causing deterioration of cold-workability.
The present invention alloy is composed a single &agr;-phase, and can secure a sufficient cold-workability. If outside the composition range of the present invention, the crystalline structure tends to be an &agr;+&bgr; phase, and the workability lowers.
Further, the present invention alloy is in ranges of 0<a*<5 and 7<b*<15 based on the chromaticity diagram of the (L* a* b*) colorimetric system if defined by JIS Z 8729.
The color tone mentioned in the present specification is shown by the values of psychometric lightness index L* (lightness: L star) and psychometric chromaticity indexes a* (greenish-reddish: a star) and b* (bluish-yellowish: b star) expressed in accordance with the specification of color of materials defined by JIS Z 8729. In particular, in order to be white color that is the characteristic of the present invention, it is better to be a color near achromatic color, which can be defined by the chromaticity indexes a* and b* as mentioned above.
The present invention is explained specifically below based on the examples.
REFERENCES:
patent: 0 545 231 (1993-09-01), None
patent: 0 678 586 (1995-10-01), None
patent: 09202931 (1997-05-01), None
Fukuyama Takahiro
Kita Kazuhiko
Sugimoto Yasuhiko
Yoshimura Yasuharu
Yee Deborah
YKK Corporation
LandOfFree
Nickel-free white copper alloy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nickel-free white copper alloy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nickel-free white copper alloy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2868110