High-strength copper alloy excellent in bendability and method for producing the same and terminal and connector using the same

Abstract

The invention aims at providing high-strength copper alloy, especially phosphor bronze, with excellent bending workability. The excellently bendable high-strength copper alloy is obtained through grain size control whereby a finally cold rolled copper alloy with a tensile strength and 0.2% yield strength different by not more than 80 MPa is allowed to have characteristics such that its mean grain size (mGS) after annealing at 425° C. for 10,000 seconds is not more than 5 μm and the standard deviation of the mean grain size (σGS) is not more than ⅓XmGS. Improvements in characteristics presumably attributable to the synergistic effect of grain-boundary strengthening and dislocation strengthening are stably achieved by the adjustments of cold rolling and annealing conditions and by the study of the correlation between pertinent characteristic values after the final rolling. The method of processing the alloy comprises cold rolling to a reduction percentage of at least 45%, final annealing to the extent that the mean grain size (mGS) is not more than 3 μm and the standard deviation of the mean grain size (σGS) is not more than 2 μm, and final cold rolling to a reduction percentage of 10-45%.

What is claimed is:  
     
         1 . A high-strength copper alloy having excellent bending workability characterized in that it is a finally cold rolled copper alloy with a tensile strength and 0.2% yield strength different by not more than 80 MPa, the alloy having characteristics such that the mean grain size (mGS) thereof after annealing at 425° C. for 10,000 seconds is not more than 5 μm and the standard deviation of the mean grain size (σGS) is not more than ⅓XmGS.  
     
     
         2 . A high-strength copper alloy having excellent bending workability according to  claim 1  characterized by comprising from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, and the balance Cu and unavoidable impurities, with a tensile strength termed TS sn  (MPa) being TS sn >500+15XSn (Sn: tin concentration (mass %)), the alloy having characteristics such that the mean grain size (mGS) thereof after annealing at 425° C. for 10,000 seconds is not more than 5 μm and the standard deviation of the mean grain size (σGS) is not more than ⅓X mGS.  
     
     
         3 . A high-strength copper alloy having excellent bending workability according to  claim 1  or  2  characterized by comprising from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, and the balance Cu and unavoidable impurities, the alloy having characteristics such that the mean grain size (mGS (μm)) thereof after annealing at 425° C. for 10,000 seconds is mGS<2.7X exp (0.0436XSn (Sn: tin concentration (mass %)).  
     
     
         4 . A high-strength copper alloy having excellent bending workability according to  claim 1 ,  2 , or  3  characterized by being a phosphor bronze which comprises from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, from 0.05 to 2.0 mass %, in total, of one, two, or more selected from among Fe, Ni, Mg, Si, Zn, Cr, Ti, Zr, Nb, Al, Ag, Be, Ca, Y, Mn, and In, and the balance Cu and unavoidable impurities.  
     
     
         5 . A high-strength copper alloy having excellent bending workability according to 1, 2, or 3 characterized by being a phosphor bronze which comprises from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, from 0.05 to 2.0 mass %, in total, of one, two, or more selected from among Fe, Ni, Mg, Si, Zn, Cr, Ti, Zr, Nb, Al, Ag, Be, Ca, Y, Mn, and In, and the balance Cu and unavoidable impurities, with particles that mainly consist of precipitation or crystallization products of the alloying metals, 0.1 μm or more in diameter, being present in a number of not fewer than 100 per square millimeter of a cross section cut in parallel to the rolling direction.  
     
     
         6 . A method of manufacturing high-strength copper alloy having excellent bending workability characterized by the steps of cold rolling to a reduction percentage of at least 45%, final annealing tothe extent that the mean grain size (mGS) is not more than 3 μm and the standard deviation of the mean grain size (σGS) is not more than 2 μm, and final cold rolling to a reduction percentage of from 10 to 45%.  
     
     
         7 . A method of manufacturing high-strength copper alloy having excellent bending workability characterized by the steps of cold rolling to a reduction percentage of at least 45%, final annealing to the extent that the mean grain size (mGS) is not more than 2 μm and the standard deviation of the mean grain size (σGS) is not more than 1 μm, and final cold rolling to a reduction percentage of from 20 to 70%.  
     
     
         8 . A method of manufacturing high-strength copper alloy having excellent bending workability according to  claim 6  or  7  characterized by stress relief annealing of the cold rolled material that has been finally cold rolled to a reduction ratio X (%) and has a tensile strength of TS 0  (MPa), until the tensile strength TS a  (MPa) after the annealing is TS a <TS 0 −X.  
     
     
         9 . A method of manufacturing high-strength copper alloy having excellent bending workability defined in any of  claims 1  to  5  characterized by the steps of cold rolling to a reduction ratio of at least 45%, final annealing to the extent that the mean grain size (mGS) is not more than 3 μm and the standard deviation of the mean grain size (σGS) is not more than 2 μm, and final cold rolling to a reduction ratio of from 10 to 45%.  
     
     
         10 . A method of manufacturing high-strength copper alloy having excellent bending workability defined in any of  claims 1  to  5  characterized by the steps of cold rolling to a reduction ratio of at least 45%, final annealing to the extent that the mean grain size (mGS) is not more than 2 μm and the standard deviation of the mean grain size ((σGS) is not more than 1 μm, and final cold rolling to a reduction ratio of from 20 to 70%.  
     
     
         11 . A method of manufacturing high-strength copper alloy having excellent bending workability defined in any of  claims 1  to  5  characterized by the steps of cold rolling to a reduction ratio of at least 45%, final annealing to the extent that either (a) the mean grain size (mGS) is not more than 3 μm and the standard deviation of the mean grain size (σGS) is not more than 2 μm, and final cold rolling to a reduction ratio of from 10 to 45% or (b) the mean grain size (mGS) is not more than 2 μm and the standard deviation of the mean grain size (σGS) is not more than 1 μm, and final cold rolling to a reduction ratio of from 20 to 70%, and thereafter stress relief annealing the cold rolled material that has been finally cold rolled to the reduction ratio X (%) and having a tensile strength of TS 0  (MPa), until the tensile strength TS a  (MPa) is TS a <TS 0 −X.  
     
     
         12 . Terminal connectors using the high-strength copper alloys having excellent bending workability according to any of  claims 1  to  5 .