Phosphor bronze strip having excellent bending workability

Abstract

A phosphor bronze strip having excellent bending workability and high mechanical strength for use in electronic parts such as terminal connectors wherein; the phosphor bronze strip has a stripe in a cross sectional microstructure revealed by etching; the difference of the maximum and the minimum of tin concentration in the region containing the stripe is between 5 and 40 mass %, preferably 5 to 25 mass % of that of a base material; and the strip is manufactured by the steps of cold rolling to a reduction ratio of at least 45%, final recrystalization annealing to the extent that the mean grain size (mGS) is from 0.5 to 2 μm and the standard deviation of the grain size (σGS) is not more than 1.5 μm, and final cold rolling to a reduction ratio of 20 to 70%.

What is claimed is:  
     
         1 . A phosphor bronze strip having excellent bending workability and high mechanical strength characterized in that; 
 said phosphor bronze strip has a stripe in a cross sectional microstructure revealed by etching by an aqueous solution containing hydroperoxide and ammonia;    the difference of the maximum and the minimum of tin concentration in the region containing the stripe is between 5 and 40 mass % of tin concentration of a base material (ΔC sn  is 5 to 40 mass %); and    said phosphor bronze strip is manufactured by the steps of cold rolling to a reduction ratio of at least 45%, final recrystalization annealing to the extent that the mean grain size (mGS) is from 0.5 to 2 μm and the standard deviation of the grain size (σGS) is not more than 1. 5μm, and    final cold rolling to a reduction ratio of 20 to 70%.    
     
     
         2 . The phosphor bronze strip according to  claim 1 , wherein said difference of the maximum and the minimum of tin concentration in the region containing the stripe is between 5 and 25 mass % of tin concentration of a base material (ΔC sn  is 5 to 25 mass %).  
     
     
         3 . The phosphor bronze strip according to claim 1 or 2, wherein said phosphor bronze strip is manufactured by a further step of final stress relief annealing to reduce a tensile strength at a rate of from 3 to 10% after the step of the final cold rolling.