Cu-Ni-Si BASED COPPER ALLOY SHEET HAVING HIGH DIE ABRASION RESISTANCE AND GOOD SHEAR PROCESSABILITY AND METHOD FOR PRODUCING SAME

摘要

A Cu-Ni-Si based copper alloy sheet which has an excellent die abrasion resistance and a good shear processability while maintaining a sufficient strength and a sufficient conductivity, said Cu-Ni-Si based copper alloy sheet comprising 1.0-4.0 mass% of Ni, 0.2-0.9 mass% of Si and the balance consisting of Cu and unavoidable impurities, wherein the number of Ni-Si precipitate grains having a grain size of 20-80 nm present on the surface thereof is 1.5×106 to 5.0×106/mm2 and the number of Ni-Si precipitate grains having a grain size exceeding 100 nm present on the surface thereof is 0.5×105 to 4.0×105/mm2. In the Cu-Ni-Si based copper alloy sheet, the ratio a/b [wherein a stands for the number (grains/mm2) of Ni-Si precipitate grains having a grain size of 20-80 nm that are present in a surface layer extending from the surface to the depth corresponding to 20% of the thickness of the whole sheet; and b stands for the number (grains/mm2) of Ni-Si precipitate grains having a grain size of 20-80 nm that are present below the surface layer] is in the range of 0.5-1.5, and the concentration of Si solid-soluted in crystal grains present in an area at a depth of less than 10 mum from the surface is 0.03-0.4 mass%.