Copper alloy with high strength and excellent processability in bending and process for producing copper alloy sheet

Abstract

The present invention provides a Cu—Fe—P alloy which has a high strength, high conductivity and superior bending workability. The copper alloy comprises 0.01 to 1.0% Fe, 0.01 to 0.4% P, 0.1 to 1.0% Mg, and the remainder Cu and unavoidable impurities. The size of oxides and precipitates including Mg in the copper alloy is controlled so that the ratio of the amount of Mg measured by a specified measurement method in the extracted residue by a specified extracted residue method to the Mg content in said copper alloy is 60% or less, thus endowing the alloy with a high strength and superior bending workability.

1 . A copper alloy having a high strength and superior bending workability, respectively containing 0.01 to 3.0% by mass of Fe, 0.01 to 0.4% by mass of P and 0.1 to 1.0% by mass of Mg, and remainder Cu and unavoidable impurities, wherein in the grain size measured by a crystal orientation analysis method in which an electron back scattering pattern system is mounted on a field emission scanning electron microscope, the mean grain size described below is 6.5 μm or less, and the standard deviation of the mean grain size described below is 1.5 μm or less:
 wherein when n indicates the number of crystal grains measured and x indicates the grain size values measured, the mean grain size is expressed as (Σx)/n, and the standard deviation of the mean grain size is expressed as [nΣx 2 −(Σx) 2 ]/[n/(n−1) 1/2 ], and 
 wherein a plate of the copper alloy has a yield stress of 400 MPa or greater. 
 
     
     
         2 . The copper alloy according to  claim 1 , wherein the ratio of small-angle grain boundaries which are grain boundaries between crystal grains in which the difference in crystal orientation is small, i.e., 5 to 15°, as measured by the crystal orientation method in the copper alloy, is 4% to 30%, taken as the ratio of the total length of the small-angle grain boundaries to the total length of the crystal grain boundaries in which the difference in crystal orientation is 5 to 180°. 
     
     
         3 . The copper alloy according to  claim 1 , wherein said copper alloy further contains Ni or Co, or both, in a content by mass of 0.01 to 1.0%. 
     
     
         4 . The copper alloy according to  claim 1 , wherein said copper alloy further contains Zn in a content by mass of 0.005 to 3.0%. 
     
     
         5 . The copper alloy according to  claim 1 , wherein said copper alloy further contains Sn in a content by mass of 0.01 to 5.0%. 
     
     
         6 . The copper alloy according to  claim 1 , wherein a copper alloy plate contains Mn or Ca, or both, at a total content of 0.0001 to 1.0% by mass. 
     
     
         7 . The copper alloy according to  claim 1 , wherein said copper alloy plate further contains one or more elements selected from a set of Zr, Ag, Cr, Cd, Be, Ti, Co, Ni, Au and Pt at a total content of 0.001 to 1.0% by mass. 
     
     
         8 . The copper alloy according to  claim 1 , wherein said copper alloy plate contains no more than a total content of 0.1 mass %, including 0%, of Hf, Th, Li, Na, K, Sr, Pd, W, S, Si, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B and/or mischmetal. 
     
     
         9 . The copper alloy according to  claim 1 , wherein the mean grain size is 4 μm or less. 
     
     
         10 . The copper alloy according to  claim 1 , wherein the standard deviation of the mean grain size is 0.9 μm or less. 
     
     
         11 . The copper alloy according to  claim 2 , wherein the ratio of small-angle grain boundaries is 5% to 25%. 
     
     
         12 . The copper alloy according to  claim 1 , wherein a plate thereof has a conductivity of 60% IACS or greater. 
     
     
         13 . A method for manufacturing a plate of the copper alloy according to  claim 1 , in which a copper alloy plate is obtained by a process including casting, hot rolling, cold rolling, annealing and cold rolling, wherein the temperature upon the completion of hot rolling is set at 550° C. to 850° C., the subsequent cold rolling rate is set at 70 to 98%, the mean heating rate in the subsequent annealing is set at 50° C./s or greater, the mean cooling rate following the annealing is set at 100° C./s or greater, and the cold rolling rate in the subsequent final cold rolling is set in the range of 10 to 30%.