Copper/zinc alloys having low levels of lead and good machinability

Abstract

The free-cutting copper alloy according to the present invention contains a greatly reduced amount of lead in comparison with conventional free-cutting copper alloys, but provides industrially satisfactory machinability. The free-cutting alloys comprise 69 to 79 percent, by weight, of copper, 2.0 to 4.0 percent, by weight, of silicon, 0.02 to 0.4 percent, by weight, of lead, and the remaining percent, by weight, of zinc.

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         3 . A free-cutting copper-silicon-zinc alloy, comprising: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         4 . A free-cutting copper-silicon-zinc alloy as recited in  claim 3 , made by a process comprising the step of subjecting the alloy to a heat treatment for 30 minutes to 5 hours at 400 to 600° C. so the one or more phases are finely dispersed in the matrix. 
     
     
         5 . A free-cutting copper-silicon-zinc alloy, comprising: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         6 . A free-cutting copper-silicon-zinc alloy as recited in  claim 5 , wherein the alloy includes one or more elements selected from the group consisting of tin and phosphorous, and the one or more phases are formed and uniformly dispersed in the matrix. 
     
     
         7 . A free-cutting copper-silicon-zinc alloy as recited in  claim 5 , made by a process comprising the step of subjecting the alloy to a heat treatment for 30 minutes to 5 hours at 400 to 600° C. so the one or more phases are finely dispersed in the matrix. 
     
     
         8 . A free-cutting copper-silicon-zinc alloy, comprising: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases formed in the matrix.   
     
     
         9 . A free-cutting copper-silicon-zinc alloy, comprising: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 0.02 to 0.25 percent, by weight, of phosphorus, 0.02 to 0.15 percent, by weight, of antimony, and 0.02 to 0.15 percent, by weight, of arsenic; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         10 . A free-cutting copper-silicon-zinc alloy as recited in  claim 9 , wherein the alloy includes one or more elements selected from the group consisting of tin and phosphorous, and the one or more phases are formed and uniformly dispersed in the matrix. 
     
     
         11 . A free-cutting copper-silicon-zinc alloy as recited in  claim 9 , made by a process comprising the step of subjecting the alloy to a heat treatment for 30 minutes to 5 hours at 400 to 600° C. so the one or more phases are finely dispersed in the matrix. 
     
     
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         23 . A free-cutting copper-silicon-zinc alloy, comprising: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc; wherein
 an extruded round test piece of the alloy having a circumferential surface, when cut on the circumferential surface by a lathe provided with a point nose straight tool at a rake angle of −8 degrees at a cutting rate of 50 m/min, a cutting depth of 1.5 mm and a feed rate of 0.11 mm/rev, yields chips having one or more shapes selected from the group consisting of an arc shape and a needle shape.   
     
     
         24 . A free-cutting copper-silicon-zinc alloy, comprising: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; and a remaining percentage, by weight, of zinc; wherein
 an extruded round test piece of the alloy having a circumferential surface, when cut on the circumferential surface by a lathe provided with a point nose straight tool at a rake angle of −8 degrees at a cutting rate of 50 m/min, a cutting depth of 1.5 mm and a feed rate of 0.11 mm/rev, yields chips having one or more shapes selected from the group consisting of an arc shape and a needle shape.   
     
     
         25 . A free-cutting copper-silicon-zinc alloy, comprising: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc; wherein
 an extruded round test piece of the alloy having a circumferential surface, when cut on the circumferential surface by a lathe provided with a point nose straight tool at a rake angle of −8 degrees at a cutting rate of 50 m/min, a cutting depth of 1.5 mm and a feed rate of 0.11 mm/rev, yields chips having one or more shapes selected from the group consisting of an arc shape and a needle shape.   
     
     
         26 . A free-cutting copper-silicon-zinc alloy, comprising: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 0.02 to 0.25 percent, by weight, of phosphorus, 0.02 to 0.15 percent, by weight, of antimony, and 0.02 to 0.15 percent, by weight, of arsenic; and a remaining percentage, by weight, of zinc; wherein
 an extruded round test piece of the alloy having a circumferential surface, when cut on the circumferential surface by a lathe provided with a point nose straight tool at a rake angle of −8 degrees at a cutting rate of 50 m/min, a cutting depth of 1.5 mm and a feed rate of 0.11 mm/rev, yields chips having one or more shapes selected from the group consisting of an arc shape and a needle shape.   
     
     
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         31 . A free-cutting copper-silicon-zinc alloy as defined in  claim 26 , made by a process comprising the step of subjecting said alloy to a heat treatment for 30 minutes to 5 hours at 400 to 600° C. 
     
     
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         33 . A free-cutting copper-silicon-zinc alloy, consisting essentially of: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         34 . A free-cutting copper-silicon-zinc alloy, consisting essentially of: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         35 . A free-cutting copper-silicon-zinc alloy, consisting essentially of: 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 1.0 to 3.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases formed in the matrix.   
     
     
         36 . A free-cutting copper-silicon-zinc alloy, consisting essentially of: 69 to 79 percent, by weight, of copper; 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.5 percent, by weight, of tin, 0.02 to 0.25 percent, by weight, of phosphorus, 0.02 to 0.15 percent, by weight, of antimony, and 0.02 to 0.15 percent, by weight, of arsenic; and a remaining percentage, by weight, of zinc;
 wherein the copper-silicon-zinc alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.