Cu-Ni-Si BASED COPPER ALLOY SHEET HAVING EXCELLENT STRESS RELAXATION RESISTANCE, AND FATIGUE RESISTANCE AND SPRING PROPERTY AFTER BENDING, AND METHOD FOR PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a Cu-N-Si based copper alloy sheet which has satisfactory fatigue resistance and spring properties and has excellent stress relaxation resistance even if being used in a high temperature-high vibration environment for a long time after being bent into a prescribed shape as the material for various electronic parts.

SOLUTION: The Cu-Ni-Si based copper alloy sheet contains Ni of 1.0 to 3.0 mass%, Si in a concentration of 1/6 to 1/4 thereof and Cr of 0.002 to 0.4 mass%, and the balance Cu with inevitable impurities, in which the area ratio of the crystal grains with the average orientation difference between all pixels in the crystal grains measured by an EBSD method being <4° is 45 to 55% of the measured area; the area average GAM of the crystal grains present in the measured area is 0.8 to 1.6°; the number of the Ni-Si precipitate grains with a grain size of >0.1 μm measured by Field Emission Auger Electron Spectroscopy is 0.2 to 0.7 piece/μm2; the number of the Cr-Si precipitate grains with a grain size of 0.01 to 0.1 μm is 0.001 to 0.1 piece/μm2, and the concentration of Si solid-soluted in the crystal grains measured by a Transmission Electron Microscope is 0.1 to 0.4 mass%.

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