Phosphor bronze strip with excellent press formability

Abstract

The present invention relates to a high-strength copper alloy used for electronic parts such as terminals and connectors, and more particularly, to a high-strength phosphor bronze strip. The present invention provides a phosphor bronze strip with excellent punching formability characterized in that a total content of S (20 to 100 ppm), Mn, Ca, Mg and Al is 50 ppm or less, a phosphor bronze strip with excellent punching formability characterized in that the sum total of lengths of etching imprints is 5 mm/mm 2 or more when a cross-section parallel to the rolling direction is etched, a phosphor bronze strip with excellent punching formability characterized in that a copper sulfide phase exists in a range of 1 to 3% of the microstructure whose cross-section is parallel to the rolling direction and a phosphor bronze strip characterized in that the plastic deformation ratio when subjected to a shearing test with clearance of 4 to 10% is 50% or less.

What is claimed is:  
     
         1 . A phosphor bronze strip with excellent punching formability comprising 20 to 100 mass ppm of S, 50 mass ppm or less, in total, of one, two, or more selected from among Mn, Ca, Mg and Al.  
     
     
         2 . A phosphor bronze strip with excellent punching formability, wherein the sum total of lengths of etching imprints when a cross-section parallel to rolling direction is etched is 5 mm/mm 2  or more.  
     
     
         3 . A phosphor bronze strip with excellent punching formability, wherein a copper sulfide phase exists in a range of 1 to 3% of a microstructure of a cross-section parallel to rolling direction.  
     
     
         4 . The phosphor bronze strip according to any of claims  1 ,  2 , or  3 , wherein a plastic deformation ratio when a shearing test is conducted with clearance of 4 to 10% is 50% or less.  
     
     
         5 . A phosphor bronze strip with excellent bending formability and punching formability comprising 20 to 100 mass ppm of S, 50 mass ppm or less, in total, of one, two, or more selected from among Mn, Ca, Mg and Al, 100 to 1,000 mass ppm of Zn.  
     
     
         6 . A phosphor bronze strip with excellent bending formability and punching formability, wherein a mean grain size (mGS) after annealing for 10,000 seconds at 425° C. is 5 μm or less, a standard deviation of the grain size (σGS) is ⅓ mGS or less and a difference between tensile strength and 0.2% yield strength of the cold-rolled phosphor bronze strip is within 80 MPa.  
     
     
         7 . The phosphor bronze strip with excellent bending formability and punching formability according to any of claims  1 ,  2 ,  3 , or  5 , wherein a mean grain size (mGS) after annealing for 10,000 seconds at 425° C. is5 μm or less, a standard deviation of the grain size (σGS) is ⅓ mGS or less and a difference between tensile strength and 0.2% yield strength of the cold-rolled phosphor bronze strip is within 80 MPa.  
     
     
         8 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 4 , wherein a mean grain size (mGS) after annealing for 10,000 seconds at 425° C. is 5 μm or less, a standard deviation of the grain size (σGS) is ⅓ mGS or less and a difference between tensile strength and 0.2% yield strength of the cold-rolled phosphor bronze strip is within 80 MPa.  
     
     
         9 . A phosphor bronze strip with excellent bending formability and punching formability, wherein a strip subjected to cold-rolling at a reduction ratio of 45% or more is subjected to final recrystallization annealing to a mean grain size (mGS) of 3 μm or less and the extent that standard deviation of the grain size (σGS) of 2 μm or less, and then subjected to final cold rolling at a reduction ratio of 10 to 45%.  
     
     
         10 . The phosphor bronze strip with excellent bending formability and punching formability according to any of claims  1 ,  2 ,  3 , or  5 , wherein a strip subjected to cold-rolling at a reduction ratio of 45% or more is subjected to final recrystallization annealing to the extent that the mean grain size (mGS) of 3 μm or less and a standard deviation of the grain size (σGS) of 2 μm or less, and then subjected to final cold rolling at a reduction ratio of 10 to 45%.  
     
     
         11 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 4 , wherein a strip subjected to cold-rolling at a reduction ratio of 45% or more is subjected to final recrystallization annealing to the extent that the mean grain size (mGS) of 3 μm or less and a standard deviation of the grain size (σGS) of 2 μm or less, and then subjected to final cold rolling at a reduction ratio of 10 to 45%.  
     
     
         12 . The phosphor bronze strip with excellent bending formability and punching formability according to any of claims  1 ,  2 ,  3 ,  5 ,  6 , or  9 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.  
     
     
         13 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 4 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.  
     
     
         14 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 7 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.  
     
     
         15 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 8 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.  
     
     
         16 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 10 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.  
     
     
         17 . The phosphor bronze strip with excellent bending formability and punching formability according to  claim 11 , wherein a cold-rolled material subjected to final cold rolling at a reduction ratio of X (%) with tensile strength of TS o  (MPa) is subjected to stress relief annealing until tensile strength TS a  (MPa) becomes TS a <TS o −X.