| 摘要 |
Provided is a copper alloy sheet which has such extremely high strength that the 0.2% proof strength is 980 MPa or higher and which is satisfactory in terms of conductivity, stress relaxation properties, and press workability. The copper alloy sheet contains, in terms of mass%, 2.50-4.00% the sum of Ni and Co, 0.50-2.00% Co, 0.70-1.50% Si, 0-0.50% Fe, 0-0.10% Mg, 0-0.50% Sn, 0-0.15% Zn, 0-0.07% B, 0-0.10% P, and 0-0.10% REM (rare earth element(s)), the total content of Cr, Zr, Hf, Nb, and S being 0-0.01%, and the remainder comprising Cu and unavoidable impurities. In the sheet, the population of "coarse second-phase grains" having a diameter of 5 μm or larger is 10 grains/mm2 or less, the population of "fine second-phase grains" having a diameter of 5-10 nm is 1.0×109 grains/mm2 or greater, and the matrix phase has an Si concentration of 0.10 mass% or higher. |
