HIGH STRENGTH COPPER ALLOY EXCELLENT IN BENDABILITY AND METHOD FOR PRODUCING THE SAME AND TERMINAL AND CONNECTOR USING THE SAME

摘要

A high strength copper alloy excellent in bendability which has been finally cold rolled, has a difference between a tensile strength and a 0.2% proof stress of 80 Mpa or less, and has been subjected to such a control of structure that it exhibits a mean grain size (mGS) of 5 mu m after the anneal at 425 DEG C for 10,000 sec and a standard deviation of said mean grain size ( sigma GS) of 1/3 X mGS or less; a method for producing the copper alloy which comprises subjecting a copper alloy to a cold rolling at a working ratio of 45 % or more, subjecting the resultant product to a final annealing to provide an alloy having a mean grain size (mGS) of 3 mu m and a standard deviation of said mean grain size ( sigma GS) of 2 mu m or less, and then subjecting the annealed product to a final cold rolling at a working ratio of 10 to 45 %. The above copper ally has been found as a result of an investigation for providing a high strength material having excellent bendability in a general copper alloy, particularly phosphor bronze, which involves adjusting the conditions for the cold rolling and annealing of phosphor bronze, searching the relationship between various properties after final rolling and has lead to stable accomplishment of the improvement of the properties which is considered to be due to the combined effect of grain boundary reinforcement and dislocation reinforcement.