Metal treatment – Stock – Copper base
Reexamination Certificate
2000-11-17
2003-09-30
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Copper base
C148S436000
Reexamination Certificate
active
06627009
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an extrafine copper alloy wire, an ultrafine copper alloy wire, and a process for producing the same, and more particularly to an extrafine copper alloy wire, with an outer diameter of 0.02 to 0.1 mm, possessing excellent bending fatigue lifetime and torsional strength and an ultrafine copper alloy wire, with a wire diameter of not more than 0.08 mm, possessing excellent tensile strength, electrical conductivity, and drawability and good elongation, and a process for producing the same.
BACKGROUND OF THE INVENTION
A reduction in size of electronic equipment, IC testers, medical ultrasound system and the like has led to an ever-increasing demand for a reduction in diameter of electric wires for use in these types of equipment. In general, conductor wires for electric wires used in this field are classified into three groups, that is, products having an outer diameter of more than 0.1 mm, products having an outer diameter of 0.02 to 0.1 mm, and products having an outer diameter of less than 0.02 mm.
For conductor wires having an outer diameter exceeding 0.1 mm, importance is attached to torsional properties and elongation from the viewpoint of preventing loosening of wires, for example, during twisting work or working of terminals. In general, for this application, annealed tough pitch copper (TPC), which is advantageous from the viewpoints of low price and good electrical conductivity, has been used.
For conductor wires having an outer diameter of less than 0.02 mm, wires are highly likely to be broken during extrusion of an insulator due to the very small diameter. For this reason, a copper-tin alloy is used which possesses excellent tensile strength and flexing resistance although the copper-tin alloy has somewhat low electrical conductivity.
For extrafine conductor wires having an intermediate size, that is, an outer diameter of 0.02 to 0.1 mm, annealed TPC is used when twistability, workability of terminals, and high electrical conductivity are required, while wire drawn product of copper-tin alloys are used when flexing resistance is required.
According to the conventional extrafine conductor wires having an intermediate size, however, the strength of the annealed TPC is so low that the bending fatigue lifetime is unsatisfactory, while, when the wire drawn products of copper-tin alloys are used, the elongation and torsional strength are so low that there is a high fear of wires being loosened, for example, during twisting work or working of terminals of electric wires.
In the case of electric wires for medical ultrasound system, there is a demand for electric wires (cables) which have an increased number of wire cores (micro coaxial cables) while maintaining the outer diameter of conventional electric wires.
To this end, high strength, high flexing resistance, high electrical conductivity, good twistability, and good workability of terminals are required of conductors for electric wires. In this case, importance is attached to high strength, flexing resistance, and high electrical conductivity among these property requirements, and, at the present time, electric wires using a hard material of a dilute copper alloy as the conductor constitute the mainstream of electric wires for medical ultrasound system.
This electric wire for medical ultrasound system comprises a large number of ultrafine copper alloy wires stranded together. The ultrafine copper alloy wire is produced by melting a dilute copper alloy, casting the molten alloy into a wire rod, and then drawing the wire rod through a die to a diameter of 0.03 mm&phgr;.
When an ultrafine copper alloy wire having a smaller diameter (for example, not more than 0.025 mm&phgr;) is used as a conductor for electric wires from the viewpoint of further reducing the diameter of electric wires for medical ultrasound system, however, excessively low breaking strength of the conductors using the conventional copper alloy causes frequent wire breaks at the time of wire drawing or stranding of the conductors. For this reason, the formation of ultrafine copper alloy wires having a diameter of not more than 0.025 mm&phgr; using conventional alloys was very difficult.
Thus, ultrafine copper alloy wires having higher tensile strength have been desired. Merely increasing the tensile strength, however, results in lowered electrical conductivity. This has led to a demand for copper alloys having both high tensile strength and high electrical conductivity.
Further, excellent drawability is required for the formation of ultrafine copper alloy wires having a diameter of not more than 0.025 mm&phgr;. When a wire rod is drawn by dicing, the presence of foreign materials having a size of about one-third of the wire diameter in the wire rod poses a problem of wire breaks. Therefore, the amount of foreign materials contained in the wire rod should be reduced to improve the wire drawability.
Detailed analysis of the foreign materials contained in a sample of a broken wire has revealed that the cause of the inclusion of foreign materials in the wire rod is classified roughly into two routes. One of them is inclusions contained in the copper alloy as a base material and the metallic elements as the additive, and peeled pieces produced by the separation of refractories such as SiC, SiO
2
, and ZrO
2
, which are components of ceramics and cement used in crucibles employed in melting and/or molds used in casting. The other route is foreign materials externally included during wire drawing. Among these foreign materials, the inclusion of the latter type of foreign materials can be reduced by performing the step of wire drawing in a clean environment.
On the other hand, improving the quality of the base material (improving the purity of substances constituting the base material) is necessary for reducing the amount of the former type of foreign materials (inclusions and peeled pieces). Therefore, when ultrafine wires are formed by wire drawing, very careful attention should be paid so as to avoid the inclusion of foreign materials in steps from melting to wire drawing, and the factor in the inclusion of the foreign material should be minimized.
Further, in the case of ultrafine copper alloy wires having a diameter of not more than 0.025 mm&phgr;, the twistability and the workability of terminals, that is, elongation, in addition to the tensile strength and the electrical conductivity, become important.
SUMMARY OF THE INVENTION
The invention has been made with a view to solving the above problems of the prior art, and it is an object of the invention to provide an extrafine copper alloy wire, with an outer diameter of 0.02 to 0.1 mm, possessing excellent bending fatigue lifetime based on high tensile strength and excellent torsional strength based on high elongation, and a process for producing the extrafine copper alloy wire.
It is another object of the invention to provide an ultrafine copper alloy wire possessing excellent tensile strength, electrical conductivity, and drawability and, at the same time, good elongation, and a process for producing the ultrafine copper alloy wire.
The features of the invention will be summarized below.
(1) An extrafine copper alloy wire comprising
a copper alloy wire having an outer diameter of 0.02 to 0.1 mm,
said copper alloy wire being formed of a heat treated copper alloy comprising 0.1 to 0.9% by weight of tin and not more than 50 ppm of oxygen with the balance consisting of copper.
In this feature of the invention, the content of tin is limited to 0.1 to 0.9% by weight. When the tin content is less than 0.1% by weight, the strength is unsatisfactory and, in its turn, the bending fatigue lifetime is unsatisfactory. On the other hand, when the tin content exceeds 0.9% by weight, the elongation is unsatisfactory. This results in lowered torsional strength and, thus, causes a problem of loosening of wires at the time of stranding or working of terminals in electric wires.
The content of oxygen is limited to not more than 50 ppm. When the oxygen content exceeds 50 ppm, an oxid
Aoyama Seigi
Goto Shigetoshi
Ichikawa Takaaki
Komuro Hiroshi
Matsui Hakaru
Hitachi Cable Ltd.
Ip Sikyin
LandOfFree
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