Copper-beryllium alloy strip

Abstract

The yield strength of UNS C17460 BeCu alloy can be significantly enhanced without compromising electrical conductivity or bend formability by age hardening the alloy during manufacture using two separate heat treatment steps and cold rolling the alloy for enhancing age hardening response between these two heat treatment steps rather than before age hardening begins as in current technology.

We claim:  
     
         1 . A copper-beryllium alloy comprising about 0.15 to 0.5 wt. % Be, about 0.35 to 1.40 wt. % Ni and/or Co, up to about 0.5 wt. % Zr, with the balance being copper and incidental impurities, wherein the alloy exhibits an electrical conductivity of at least 45% IACS, a bend formability of less than about 3 R/t in the longitudinal (Good Way) direction and less than 9 R/t in the transverse (Bad Way) direction, and a 0.2% yield strength of at least about 130 ksi.  
     
     
         2 . The alloy of  claim 1 , wherein the alloy has a bend formability of less than about 5 R/t in the transverse (Bad Way) direction.  
     
     
         3 . The alloy of  claim 2 , wherein the alloy has a bend formability of less than about 3 R/t in the transverse (Bad Way) direction.  
     
     
         4 . The alloy of  claim 3 , wherein the alloy has a 0.2% yield strength of at least about 140 ksi.  
     
     
         5 . The alloy of  claim 4 , wherein the alloy contains about 0.15 to 0.5 wt. % Be, about 1.0 to 1.40 wt. % Ni, up to 0.5 wt. % Zr and the balance Cu plus incidental impurities.  
     
     
         6 . The alloy of  claim 4 , wherein the alloy contains about 0.15 to 0.5 wt. % Be, about 0.35 to 0.60 wt. % Co and the balance Cu plus incidental impurities.  
     
     
         7 . The alloy of  claim 1 , wherein the alloy contains about 0.15 to 0.5 wt. % Be, about 1.0 to 1.40 wt. % Ni, up to 0.5 wt. % Zr and the balance Cu plus incidental impurities.  
     
     
         8 . The alloy of  claim 1 , wherein the alloy contains about 0.15 to 0.5 wt. % Be, about 0.35 to 0.60 wt. % Co and the balance Cu plus incidental impurities.  
     
     
         9 . The alloy of  claim 1 , wherein the alloy contains no more than about 0.5 wt. % of one or more of the following additional ingredients: Fe, Al, Si, Sn, Zn, Cr, V, Mo, Mn, W, Ag, Au, Ta, Nb, Ti, Hf, P, Mg, Ca, Se, Te, S and Pb.  
     
     
         10 . Alloy strip or wire made from the alloy of  claim 1 .  
     
     
         11 . Alloy strip or wire made from the alloy of  claim 4 .  
     
     
         12 . Alloy strip or wire made from the alloy of  claim 5 .  
     
     
         13 . A process for making alloy strip exhibiting an electrical conductivity of at least 45% IACS, a bend formability of less than about 3 R/t in the longitudinal (Good Way) direction and less than 9 R/t in the transverse (Bad Way) direction, and a 0.2% yield strength of at least about 130 ksi, the alloy forming the strip containing 0.15 to 0.5 wt. % Be, about 0.35 to 1.40 wt. % Ni and/or Co, up to about 0.5 wt. % Zr, with the balance being copper and incidental impurities, the process comprising 
 (a) subjecting the alloy to a first age hardening heat treatment directly after final solution anneal,    (b) cold rolling the alloy, and    (c) subjecting the alloy to at least a second age hardening heat treatment.    
     
     
         14 . The process of  claim 13 , wherein the first age hardening heat treatment step is carried out to achieve substantial peak aging or slight averaging of the alloy.  
     
     
         15 . The process of  claim 13 , wherein the alloy is heated at about 725 to 825° F. during the first age hardening heat treatment, then cold rolled by an amount of about 45 to 65% in thickness reduction, and then subjected to a second age hardening step by 
 heating the alloy in bulk at about 550° F. to 800° F., or  
 passing a continuous length of the strip through an age hardening furnace maintained at a temperature of 750° F. to 900° F., for a dwell time of no more than 5 minutes.  
 
     
     
         16 . The process of  claim 15 , wherein the alloy is subjected to final solution anneal by heating at a temperature of 1650 F to 1725 F for a time sufficient to achieve an annealed average grain size not exceeding about 0.030 mm.  
     
     
         17 . The process of  claim 13 , wherein an alloy strip having a 0.2% yield strength of at least about 130 ksi, an electrical conductivity of at least about 45% IACS and a bend formability of 3 R/t or less in both the longitudinal and transverse directions is produced by heating the alloy at about 850 to 950° F. during the first age hardening heat treatment, then cold rolling the alloy by an amount of about 15 to 50% in thickness reduction, and then subjecting the alloy to a second age hardening step by passing a continuous length of the strip through an age hardening furnace maintained at a temperature of 750 to 800° F., for a dwell time of no more than 5 minutes.  
     
     
         18 . The process of  claim 17 , wherein the alloy is subjected to final solution anneal by heating at a temperature of 1650 F to 1725 F for a time sufficient to achieve an annealed average grain size not exceeding about 0.030 mm.  
     
     
         19 . The process of  claim 13 , wherein an alloy strip having a 0.2% yield strength of at least about 140 ksi, an electrical conductivity of at least about 45% IACS and a bend formability of 3 R/t or less in both the longitudinal and transverse directions is produced by heating the alloy at about 1700 to 1750° F. during final solution anneal, heating the alloy at about 700 to about 800° F. during the first age hardening heat treatment, cold rolling the alloy by an amount of about 15 to 30% in thickness reduction, and then heating the alloy in bulk at about 550° F. to 800° F. during a second age hardening heat treatment.  
     
     
         20 . The process of  claim 19 , wherein the alloy is subjected to final solution anneal by heating at a temperature of 1700 F to 1750 F for a time sufficient to achieve an annealed average grain size not exceeding about 0.030 mm.  
     
     
         21 . A process for making alloy wire exhibiting an electrical conductivity of at least 45% IACS, a 0.2% yield strength of at least about 130 ksi, the alloy forming the strip containing 0.15 to 0.5 wt. % Be, about 0.35 to 1.40 wt. % Ni and/or Co, up to about 0.5 wt. % Zr, with the balance being copper and incidental impurities, the process comprising 
 (a) subjecting the alloy to a first age hardening heat treatment directly after final solution anneal,    (b) cold working the alloy, and    (c) subjecting the alloy to at least a second age hardening heat treatment.