Cu-Ni-Si-based copper alloy sheet material and method of manufacturing same

Abstract

This invention provides a copper alloy sheet material containing, in mass %, Ni: 0.7%-4.2% and Si: 0.2%-1.0%, optionally containing one or more of Sn: 1.2% or less, Zn: 2.0% or less, Mg: 1.0% or less, and Co: 2.0% or less, and a total of 3% or less of one or more of Cr, B, P, Zr, Ti, Mn and V, the balance being substantially Cu, and having a crystal orientation satisfying Expression (1):I{420} / I0{420}>1.0,   (1)where I{420} is the x-ray diffraction intensity from the {420} crystal plane in the sheet plane of the copper alloy sheet material and I0{420} is the x-ray diffraction intensity from the {420} crystal plane of standard pure copper powder. The copper alloy sheet material has highly improved strength, post-notching bending workability, and stress relaxation resistance property.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a Cu—Ni—Si-based copper alloy sheet material suitable for use in electrical and electronic parts such as connectors, lead frames, relays, switches and the like, particularly to a copper alloy sheet material that exhibits excellent bending workability and stress relaxation resistance property while maintaining high strength and high conductivity, and a method of manufacturing the same.[0003]2. Background Art[0004]The connectors, lead frames, relays, switches and other current-carrying components of electrical and electronic parts require good conductivity for minimizing generation of joule heat due to passage of current and also require high strength capable of enduring stress imparted during assembly and / or operation of the electrical or electronic parts. Because electrical and electronic parts are generally formed by bending, the current-carrying components must also have excellent bending wor...

AI Technical Summary

Benefits of technology

[0027]In light of the foregoing circumstances, an object of the present invention is to provide a Cu—Ni—Si-based copper alloy that retains high strength while simultaneously achieving the demanding bending workability required in the notch-and-bend method and the stress relaxation resistance property needed to ensure reliability in the harsh use environments of, for example, vehicle-mounted connectors.

Problems solved by technology

This in turn has led to still severer requirements regarding the level of material strength.

With this method, however, the notching work-hardens the vicinity of the notch, so that cracking is apt to occur during the ensuing bending.

In addition, the fact that more and more electrical and electronic parts are being utilized in severe environment applications has made stress relaxation resistance property an increasingly critical issue.

However, Cu—Ni—Si-based alloy is known to be an alloy system that is difficult to make excellent in both strength and bending workability or both bending workability and stress relaxation resistance property.

However, the former method reduces conductivity and causes bending workability to decline with increasing amount of Ni—Si type precipitates.

Thus while a high strength level and a high conductivity level may be achieved, it may become impossible to form the electrical or electronic part.

However, this method increases the tendency of work-hardening for the material, so that when the notch-and-bend method is adopted, the notching markedly increases hardness in the vicinity of the notch.

A problem therefore arises of the bending workability being radically degraded at the time of bending the material along the notch.

However, while it may be possible to achieve crystal grain refinement in this case, the amount of Ni and Si entering solid solution is reduced, which inevitably lowers the strength level after aging treatment.

Particularly in the case of vehicle-mounted connectors and other high-temperature environment applications, the diffusion velocity of the atom along grain boundaries is extremely high than that within the grains, so that the loss of stress relaxation resistance property caused by crystal grain refinement becomes a major problem.

This kind of texture regulation usually lowers strength.

Patent Documents 2 and 3 point out that the fact that bending workability is anisotropic makes it difficult to improve bending workability simultaneously both for the case where the bending axis lies perpendicular to the rolling direction (G.W.) and for the case where it lies parallel to the rolling direction (B.W.).

However, even in the Cu—Ni—Si-based alloys improved in bending workability by texture control as in Patent Documents 1 to 5, no consideration is given to preventing cracking caused by the notch-and-bend method, indicating that the post-notching bending workability is not sufficiently improved.

Moreover, while, as mentioned in the foregoing, crystal grain refinement is effective for improving bending workability, it is a negative factor with regard to overcoming stress relaxation, which is one type of creep phenomenon.

Because of this, and the fact that achieving a high degree of improvement is difficult even with to regard bending workability alone, still further improvement of stress relaxation resistance property cannot be achieved even by using the prior art texture control.

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