Copper alloy having excellent corrosion cracking resistance and dezincing resistance, and method for producing same

Abstract

A copper alloy having an excellent corrosion cracking resistance and an excellent dezincing resistance consists of: 58 to 66 wt % of copper (Cu); 0.1 to 0.8 wt % of Sn; 0.01 to 0.5 wt % of Si; at least one of 0.3 to 3.5 wt % of lead (Pb), 0.3 to 3.0 wt % of bismuth (Bi), 0.02 to 0.15 wt % of phosphorus (P), 0.02 to 3.0 wt % of nickel (Ni) and 0.02 to 0.6 wt % of iron (Fe) if necessary; and the balance being zinc (Zn) and unavoidable impurities, wherein the proportion of an alpha phase is 80 vol % or more. The apparent content of zinc (Zn) in the copper alloy is in the range of from 34 to 39 wt %.

1 . A copper alloy comprising 58 to 66 wt % of copper, 0.1 to 0.8 wt % of tin, 0.01 to 0.5 wt % of silicon, and the balance being zinc and unavoidable impurities, wherein a proportion of an alpha phase is 80 vol % or more.  
     
     
         2 . A copper alloy as set forth in  claim 1 , wherein an apparent content B′ of zinc in said copper alloy is in the range of from 34 to 39 wt %, said apparent content B′ of zinc being expressed by the following expression: 
           B ′=[( B+t   1   q   1   +t   2   q   2 )/( A+B+t   1   q   1   +t   2   q   2 )]×100 
       wherein A denotes the content (wt %) of copper and B denotes the content (wt %) of zinc, t 1  and t 2  denoting zinc equivalents of tin and silicon, respectively (t 1 =2.0, t 2 =10.0), and q 1  and q 2  denoting the contents (wt %) of tin and silicon, respectively.  
     
     
         3 . A copper alloy as set forth in  claim 1 , which further contains at least one of 0.3 to 3.5 wt % of lead and 0.3 to 3.0 wt % of bismuth.  
     
     
         4 . A copper alloy as set forth in  claim 1  or  3 , which further contains at least one of 0.02 to 0.15 wt % of phosphorus, 0.02 to 3.0 wt % of nickel, and 0.02 to 0.6 wt % of iron, the total amount thereof being in the range of from 0.02 to 3.0 wt %.  
     
     
         5 . A copper alloy as set forth in  claim 4 , wherein an apparent content B′ of zinc in said copper alloy is in the range of from 34 to 39 wt %, said apparent content B′ of zinc being expressed by the following expression: 
           B ′=[( B+t   1   q   1   +t   2   q   2   +t   3   q   3   +t   4   q   4 )/( A+B+t   1   q   1   +t   2   q   2   +t   3   q   3   +t   4   q   4 )]×100 
       wherein A denotes the content (wt %) of copper and B denotes the content (wt %) of zinc, t 1 , t 2 , t 3  and t 4  denoting zinc equivalents of tin, silicon, nickel and iron, respectively (t 1 =2.0, t 2 =10.0, t 3 =−1.3, t 4 =0.9), and q 1 , q 2 , q 3  and q 4  denoting the contents (wt %) of tin, silicon, nickel and iron, respectively.  
     
     
         6 . A method for producing a copper alloy, said method comprising the steps of: 
 preparing raw materials of a copper alloy comprising 58 to 66 wt % of copper, 0.1 to 0.8 wt % of tin, 0.01 to 0.5 wt % of silicon, and the balance being zinc and unavoidable impurities;    casting the raw materials to form an ingot;    hot working said ingot;    cold or hot working the hot worked ingot;    annealing the cold or hot worked ingot at a temperature of 300 to 600° C. for two minutes to five hours; and    cooling the annealed ingot at a cooling rate of 0.2 to 10° C./sec.    
     
     
         7 . A method for producing a copper alloy as set forth in  claim 6 , wherein an apparent content B′ of zinc in said copper alloy is in the range of from 34 to 39 wt %, said apparent content B′ of zinc being expressed by the following expression: 
           B ′=[( B+t   1   q   1   +t   2   q   2 )/( A+B+t   1   q   1   +t   2   q   2 )]×100 
       wherein A denotes the content (wt %) of copper and B denotes the content (wt %) of zinc, t 1  and t 2  denoting zinc equivalents of tin and silicon, respectively (t 1 =2.0, t 2 =10.0), and q 1  and q 2  denoting the contents (wt %) of tin and silicon, respectively.  
     
     
         8 . A method for producing a copper alloy as set forth in  claim 6 , wherein said raw materials further contain at least one of 0.3 to 3.5 wt % of lead and 0.3 to 3.0 wt % of bismuth.  
     
     
         9 . A method for producing a copper alloy as set forth in  claim 6  or  8 , wherein said raw materials further contain at least one of 0.02 to 0.15 wt % of phosphorus, 0.02 to 3.0 wt % of nickel, and 0.02 to 0.6 wt % of iron, the total amount thereof being in the range of from 0.02 to 3.0 wt %.  
     
     
         10 . A method for producing a copper alloy as set forth in  claim 9 , wherein an apparent content B′ of zinc in said copper alloy is in the range of from 34 to 39 wt %, said apparent content B′ of zinc being expressed by the following expression: 
           B ′=[( B+t   1   q   1   +t   2   q   2   +t   3   q   3   +t   4   q   4 )/( A+B+t   1   q   1   +t   2   q   2   +t   3   q   3   +t   4   q   4 )]×100 
       wherein A denotes the content (wt %) of copper and B denotes the content (wt %) of zinc, t 1 , t 2 , t 3  and t 4  denoting zinc equivalents of tin, silicon, nickel and iron, respectively (t 1 =2.0, t 2 =10.0, t 3 =−1.3, t 4 =0.9), and q 1 , q 2 , q 3  and q 4  denoting the contents (wt %) of tin, silicon, nickel and iron, respectively.