High-strength copper alloys with excellent bending workability and terminal connectors 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 ⅓×mGS. 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%.

1 . A high-strength copper alloy having excellent bending workability that 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 the mean grain size (mGS) thereof after annealing at 425° C. for 10,000 seconds not more than 5 μm and the standard deviation of the mean grain size (σGS) not more than ⅓×mGS, wherein the alloy consists essentially of from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, and the balance Cu and unavoidable impurities. 
     
     
         2 . A high-strength copper alloy having excellent bending workability according to  claim 1  with a tensile strength termed TS Sn  (MPa) being TS Sn >500+15×Sn (Sn: tin concentration (mass %)). 
     
     
         3 . A high-strength copper alloy having excellent bending workability according to  claim 1 , the alloy having characteristics such that the mean grain size (mGS (μm)) thereof after annealing at 425° C. for 10,000 seconds is mGS<2.7×exp (0.0436×Sn (Sn: tin concentration (mass %)). 
     
     
         4 . A high-strength copper alloy having excellent bending workability, wherein the high-strength copper alloy is a phosphor bronze which consists essentially of from 1 to 11 mass % Sn, from 0.03 to 0.35 mass % P, from 0.05 to 1.0 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, and 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 the mean grain size (mGS) thereof after annealing at 425° C. for 10,000 seconds not more than 5 μm and the standard deviation of the mean grain size (σGS) not more than ⅓×mGS. 
     
     
         5 . A high-strength copper alloy having excellent bending workability according to  claim 4 , wherein the alloy is a phosphor bronze with particles that consist essentially 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 comprising 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 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 according to  claim 6  of manufacturing high-strength copper alloy having excellent bending workability comprising the steps of 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  comprising 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 according to  claim 6  of manufacturing high-strength copper alloy having excellent bending workability defined in  claim 1 . 
     
     
         10 . A method according to  claim 7  of manufacturing high-strength copper alloy having excellent bending workability defined in  claim 1 . 
     
     
         11 . A method according to  claim 7  of manufacturing high-strength copper alloy having excellent bending workability defined in  claim 1 . 
     
     
         12 . A terminal connector using the high-strength copper alloys having excellent bending workability according to  claim 1 . 
     
     
         13 . A high-strength copper alloy having excellent bending workability according to  claim 4 , with a tensile strength termed TS Sn  (MPa) being TS Sn >500+15×Sn (Sn: tin concentration (mass %)). 
     
     
         14 . A high-strength copper alloy having excellent bending workability according to  claim 4 , having
   mGS<2.7×exp(0.0436×Sn)   where mGS is the mean grain size in μm of the alloy after annealing at 425° C. for 10,000 seconds, and   Sn is the tin concentration in mass %.   
     
     
         15 . A terminal connector using the high-strength copper alloy having excellent bending workability according to  claim 13 .