Metal treatment – Stock – Copper base
Reexamination Certificate
2000-05-04
2002-04-30
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Copper base
C420S472000
Reexamination Certificate
active
06379478
ABSTRACT:
BACKGROUND OF THE INVENTION
Several families of copper alloys are known in various arts. For example, Mikawa et al., U.S. Pat. No. 5,041,176 discloses a copper alloy including from 0.1-10% nickel (Ni); 0.1-10% tin (Sn); 0.05-5% silicon (Si); 0.01-5% iron (Fe); and 0.0001-1% boron (B), by weight. This disclosure requires formation of an Ni-Si intermetallic compound homogeneously dispersed in the alloy. Fe is required for age hardening. However, at Fe concentrations greater than 5%, electrical conductivity is compromised and corrosion becomes a serious problem. B is incorporated into the alloy to improve corrosion resistance, hardness and strength. High hardness is achieved by precipitation hardening at a tempering temperature of 400° to 450° C. Si also serves as a deoxidizer.
Although the Mikawa alloy is suitable for use in electronic parts where good electrical conductivity, heat conductivity, strength, hardness, plating ability, soldering ability, elasticity, and corrosion resistance including resistance to acids are required, this alloy is of a different composition and displays different characteristics from those obtainable according to the instant invention.
Another comparison alloy is disclosed by Kubosono et al., U.S. Pat. No. 5,516,484. Kubosono et al. discloses copper-nickel based alloys that are processed using horizontal continuous casting with a graphite mold. The Ni—Cu alloy system is essentially a different alloy than the alloy of the instant invention. In this alloy copper (Cu) is an undesired impurity whose content must be kept below 0.02%. Kubosono et al., teaches that effects obtainable by addition of Si cannot be recognized if no B is present.
U.S. Pat. No. 5,334,346 to Kim et al. discloses a high performance copper alloy for electrical and electronic parts. The Kim alloy consists essentially of copper and 0.5 to 2.4% by weight Ni; 0.1-0.5% Si; 0.02 to 0.16% P; and 0.02 to 0.2% magnesium (Mg). Kim et al. discusses precipitation hardening where Ni
2
Si and Ni
3
P precipitate in the copper matrix. Any excess of free Si and P, is taught as causing formation of brittle intermetallic compounds which lead to peeling and cracking. Mg is proposed as a scavenger element to remove free Si and P. However, as content of Mg increases, conductivity and utility of the alloy are compromised. Zinc (Zn) and Fe are also disclosed as possible scavengers. This alloy does not contain Sn.
Hashizume et al., U.S. Pat. No. 5,064,611 discloses a process for producing a copper alloy that contains 1-8% Ni; 0.1-0.8% P; 0.6-1.0% Si; optionally, 0.03 to 0.5% Zn; and Cu. Ni
5
P
2
and Ni
2
Si are disclosed as intermetallic compounds for increasing mechanical strength of the alloy with minimal decrease in electrical conductivity. Sn is not present in this alloy.
As an example of a copper-tin alloy, i.e., bronze, Asai et al., U.S. Pat. No. 5,021,105, discloses an alloy comprising 2.0-7.0% Sn; 1.0-6.0% Ni, cobalt (Co) or chromium (Cr); 0.1-2.0% Si; and Cu. This alloy may be processed to exhibit elongation of 3-20%; strength of 70-100 kg/mm
2
; and electroconductivity from 10-30% IACS. Ni is disclosed as being important for strengthening; Cr is disclosed as improving hot rolling properties and heat resistance; and Co is disclosed as contributing to effective heat resistance. According to Asai et al. Sn content is limited to 7% by the hot rolling method used to process the alloy. Asai et al. does not disclose phosphorus (P) as a constituent. Accordingly, this alloy suffers similar limitations to Mikawa et al., as discussed above.
Similarly, Arita et al., U.S. Pat. No. 4,337,089, discloses a Cu—Ni—Sn alloy containing 0.5-3.0% Ni; 0.3-0.9% Sn; 0.01-0.2% P; 0.0-0.35% manganese (Mn) or Si; and Cu. This alloy features 60 kg/mm
2
tensile strength and elongation of more than 6% (i.e., to provide the mechanical property necessary for bend working) by combining heat treatment and cold rolling in its processing. In Arita et al., Si or Mn is incorporated to enhance strength. The low Sn content disclosed in Arita et al., however, does not provide the combined formability-strength properties of the instant invention.
Takeda et al., U.S. Pat. No. 5,132,083 teaches a laser padding material which is a powder containing 1-5% Ni; 0.2-5% Si; less than 1% ; less than 2% P; less than 3% Mn; and Cu. Sn and lead (Pb) are optional ingredients, at 8-15% for each. This powder can be laser processed to produce a copper laser padding material excellent in sliding-abrasion resistance. The chemistries involved in laser padding are not the same as in the alloy of the instant invention. For example, no rolling, hot or cold, is used to process the padding material.
A designation system for providing a means for defining and identifying coppers and copper alloys is known as UNS (Unified Numbering System). This system is in common use in North America and uses a five digit (recently expanded from three digit) numbering following a C prefix. The numbering system is not a specification, but rather a useful number code for identifying mill and foundry products. The C designations appearing below refer to the UNS numbers. The general art that includes alloys thus includes many patentable alloys that are similar in some respects in composition, but that display different desired properties depending on the specific content and processing of the alloy.
UNS alloy C85800 is a leaded yellow brass containing 1.5% Sn, 1.5% Pb, 31-41% Zn, 0.5% Fe, 0.05%Sb, 0.5% Ni (incl Co), 0.25% Mn, 0.05% As, 0.05% S, 0.01% P, 0.55% Al, 0.25% Si and 57.0% minimum Cu.
In the electronics industry, phosphor bronzes with required strength and formability are known that can be used up to 100° C. However, the need exists for alloys resistant to higher temperatures, e.g., of 120° C., 140° C. and temperatures up to or exceeding 150° C. Higher temperature applications will allow faster speed in electronic processing and allow the alloy to be used in higher temperature environments.
Accordingly, the present invention provides a phosphor bronze alloy with characteristics much improved over those known in the art. The invention provides an alloy that when processed has desired spring and strength properties and superior durability especially at higher temperatures at an economic price.
REFERENCES:
patent: 4732731 (1988-03-01), Asai et al.
patent: 5286444 (1994-02-01), Tomikawa et al.
patent: 1060052 (1992-04-01), None
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patent: 07126779 (1995-05-01), None
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Oya, Shigeo; Nakano, Kosaku, Effects of micro-segregation on inverse segregation in copper-tin alloys, Rep. Cast. Res. Lab., Waseda Univ. (1977), 28, 57-61 (provided abstract only).
Farquharson Daniel D.
Mandle David H.
Ip Sikyin
Sughrue & Mion, PLLC
The Miller Company
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