Silver containing copper alloy

Abstract

A copper alloy that consists essentially of, by weight, from 0.15% to 0.7% of chromium, from 0.005% to 0.3% of silver, from 0.01% to 0.15% of titanium, from 0.01% to 0.10% of silicon, up to 0.2% of iron, up to 0.5% of tin, and the balance copper and inevitable impurities has high strength, a yield strength in excess of 80 ksi, and high electrical conductivity, in excess of 80% IACS. The alloy further has substantially isotropic bend characteristics when the processing route includes a solution heat anneal above 850° C. and subsequent cold rolling into sheet, strip or foil interspersed by bell annealing. As a result, the alloy is particularly suited for forming into box-type electrical connectors for both automotive or multimedia applications. The alloy is also suitable for forming into a rod, wire or section.

We claim:  
     
         1 . A copper alloy, consisting essentially of, by weight: 
 from 0.15% to 0.7% of chromium;    from 0.005% to 0.3% of silver;    from 0.01% to 0.15% of titanium;    from 0.01% to 0.10% of silicon;    up to 0.2% of iron;    up to 0.5% of tin; and    the balance copper and inevitable impurities.    
     
     
         2 . The copper alloy of  claim 1 , consisting essentially of, by weight: 
 from 0.25% to 0.6% of chromium;    from 0.015% to 0.2% of silver;    from 0.01% to 0.08% of titanium;    from 0.01% to 0.10% of silicon;    less than 0.1% of iron;    up to 0.25% of tin; and    the balance copper and inevitable impurities.    
     
     
         3 . The copper alloy of  claim 2  having a maximum of 0.065% of titanium.  
     
     
         4 . The copper alloy of  claim 2  having a minimum of 0.05% of titanium.  
     
     
         5 . The copper alloy of  claim 2 , consisting essentially of, by weight: 
 from 0.3% to 0.55% of chromium;    from 0.08% to 0.13% of silver;    from 0.02% to 0.065% of titanium;    from 0.02% to 0.05% of silicon;    from 0.03% to 0.09% of iron;    less than 0.05% of tin; and    the balance copper and inevitable impurities.    
     
     
         6 . The copper alloy of  claim 1  wherein a ratio, by weight, of iron to titanium, Fe:Ti, is from 0.7:1 to 2.5:1.  
     
     
         7 . The copper alloy of  claim 6  where Fe:Ti is from 0.9:1 to 1.7:1.  
     
     
         8 . The copper alloy of  claim 6  wherein at least a portion of the iron is replaced with cobalt on a 1:1, by weight, basis.  
     
     
         9 . The copper alloy of  claim 1  wherein the zirconium content is essentially zero.  
     
     
         10 . The copper alloy of  claim 1  having a Quality Function Deployment, QFD, value in excess of 50 for both automotive and multimedia applications.  
     
     
         11 . The copper alloy of  claim 1  further containing from 0.05% to 0.2%, by weight, of magnesium.  
     
     
         12 . The copper alloy of  claim 10  formed into an electrical connector.  
     
     
         13 . The copper alloy of  claim 12  formed into a box-type connector.  
     
     
         14 . The copper alloy of  claim 10  formed into a leadframe.  
     
     
         15 . The copper alloy of  claim 1  formed into a rod.  
     
     
         16 . The copper alloy of  claim 1  formed into a wire.  
     
     
         17 . A process for forming a copper alloy having high electrical conductivity, good resistance to stress relaxation and isotropic bend properties, comprising the steps of: 
 casting a copper alloy that contains, by weight, from 0.15% to 0.7% of chromium and the balance copper and inevitable impurities;    hot working said copper alloy at a temperature of between 700° C. and 1030° C.;    cold working said copper alloy to a thickness reduction of from 40% to 99% in thickness; and    annealing said copper alloy in a first age anneal at a temperature of from 350° C. to 900° for from 1 minute to 10 hours.    
     
     
         18 . The process of  claim 17  wherein said cast copper alloy further contains from 0.005% to 0.3% of silver, from 0.01% to 0.15% of titanium, from 0.01% to 0.10% of silicon, up to 0.2% of iron and up to 0.5% of tin.  
     
     
         19 . The process of  claim 18  wherein said hot working is hot rolling at a temperature of between 750° C. and 1030° C. to form a strip and a solution anneal at a temperature of from 850° to 1030° for from 10 seconds to 15 minutes followed by a quench from a temperature in excess of 850° C. to less than 500° C. is interposed between said hot working and said cold working.  
     
     
         20 . The process of  claim 19  wherein said hot rolling is at a temperature of from 900° C. and 1020° C. and is followed by a water quench.  
     
     
         21 . The process of  claim 19  wherein said solution annealing step is a strip anneal at temperature of from 900° C. to 1000° C. for from 15 seconds to 10 minutes.  
     
     
         22 . The process of  claim 21  wherein said solution annealing step is at a temperature of from 930° C. to 980° C. for from 20 seconds to 5 minutes.  
     
     
         23 . The process of  claim 21  including a second age anneal subsequent to said first age anneal wherein said second age anneal is at a temperature of from 300° C. to 450° C. for from one hour to 20 hours.  
     
     
         24 . The process of  claim 23  wherein said first age anneal is at a temperature of from 350° C. to 550° C. for from 1 hour to 10 hours.  
     
     
         25 . The process of  claim 24  wherein said first age anneal is at a temperature of from 400° C. to 500° C. and said second age anneal is at a temperature of from 350° C. to 420° C.  
     
     
         26 . The process of  claim 25  wherein said first age anneal is for from one to three hours and said second anneal is for from five to seven hours.  
     
     
         27 . The process of  claim 24  including the step of forming an electrical connector having improved resistance to stress relaxation following said second age anneal.  
     
     
         28 . The process of  claim 21  including the steps of cold rolling and stress relief annealing following said first age anneal.  
     
     
         29 . The process of  claim 28  wherein said cold rolling following said first age anneal is 10% to 50% reduction in thickness and said stress relief anneal is at a temperature of from 200° C. to 500° C. for from 10 seconds to 10 hours.  
     
     
         30 . The process of  claim 28  including the step of forming an electrical connector from said copper alloy following said stress relief anneal.  
     
     
         31 . The process of  claim 24  including the steps of cold rolling and stress relief annealing following said second age anneal.  
     
     
         32 . The process of  claim 31  wherein said cold rolling following said second age anneal is for a 10% to 50% reduction in thickness and said stress relief anneal is at a temperature of from 200° C. to 500° C. for from 10 seconds to 10 hours.  
     
     
         33 . The process of  claim 32  including the step of forming an electrical connector from said copper alloy following said stress relief anneal.  
     
     
         34 . A process for forming a copper alloy having high electrical conductivity, good resistance to stress relaxation and isotropic bend properties, comprising the steps of: 
 casting a copper alloy that contains, by weight, from 0.15% to 0.7% of chromium and the balance copper and inevitable impurities via a continuous process whereby said copper alloy is cast as a strip with a thickness of from about 0.4 inch to 1 inch:    cold rolling said strip to a thickness effective for strip solution annealing solution annealing said strip at a temperature of between 850° C. and 1030° C. for from 10 seconds to 15 minutes;    quenching said solution annealed strip from a temperature in excess of 850° C. to less than 500° C.;    cold working said copper alloy to a thickness reduction of from 40% to 80% in thickness; and    annealing said copper alloy in a first age anneal at a temperature of from 350° C. to 900° for from 1 minute to 10 hours.    
     
     
         35 . The process of  claim 21  wherein said casting step forms a rectangular ingot that is reduced to strip by hot rolling followed by a cold work inducing cold rolling step.  
     
     
         36 . The process of  claim 35  where in said cold work inducing cold rolling step said strip is reduced in thickness by from 25% to 90%.  
     
     
         37 . The process of  claim 36  including a stress relief anneal step following said cold work inducing step, said stress anneal step being at a temperature of 200° C. to 500° C. for from 10 seconds to 10 hours.  
     
     
         38 . The process of  claim 37  including the step of forming an electrical connector having high strength and high electrical conductivity following said stress relief anneal step.  
     
     
         39 . The process of  claim 18  wherein said hot working is extruding at a temperature of between 700° C. and 1030° C. to form a rod of said copper alloy.  
     
     
         40 . The process of  claim 39  wherein said hot extruding is at a temperature of between 930° C. and 1020° C. and is followed by a water quench.  
     
     
         41 . The process of  claim 39  wherein said cold working is extrusion with a thickness reduction of up to 98% and said annealing is at a temperature of from 350° C. to 900° C. for from 1 minute to 6 hours.  
     
     
         42 . The process of  claim 41  wherein said cold working and said annealing steps are repeated at least one additional time.  
     
     
         43 . The process of  claim 42  wherein said rod is cold extruded for a thickness reduction of up to 98% following a last of said annealing steps.  
     
     
         44 . The process of  claim 43  including forming a rod having high strength and high electrical conductivity.  
     
     
         45 . The process of  claim 43  including forming a wire having high strength and high electrical conductivity.  
     
     
         46 . The process of  claim 17  wherein said hot working is hot rolling at a temperature of between 750° C. and 1030° C. to form a strip and a solution anneal at a temperature of from 850° to 1030° for from 10 seconds to 15 minutes followed by a quench from a temperature in excess of 850° C. to less than 500° C. is interposed between said hot working and said cold working.  
     
     
         47 . The process of  claim 46  wherein said hot rolling is at a temperature of from 900° C. and 1020° C. and is followed by a water quench.  
     
     
         48 . The process of  claim 46  wherein said solution annealing step is a strip anneal at temperature of from 900° C. to 1000° C. for from 15 seconds to 10 minutes.  
     
     
         49 . The process of  claim 48  wherein said solution annealing step is at a temperature of from 930° C. to 980° C. for from 20 seconds to 5 minutes.  
     
     
         50 . The process of  claim 48  wherein said first age anneal is at a temperature of from 350° C. to 550° C. for from 1 hour to 10 hours.  
     
     
         51 . The process of  claim 49  wherein said first age anneal is at a temperature of from 400° C. to 500° C. and said second age anneal is at a temperature of from 350° C. to 420° C.  
     
     
         52 . The process of  claim 51  wherein said first age anneal is for from one to three hours and said second anneal is for from five to seven hours.  
     
     
         53 . The process of  claim 48  including the steps of cold rolling and stress relief annealing following said first age anneal.  
     
     
         54 . The process of  claim 53  wherein said cold rolling following said first age anneal is 10% to 50% reduction in thickness and said stress relief anneal is at a temperature of from 200° C. to 500° C. for from 10 seconds to 10 hours.