Machinable copper-based alloy and method for producing the same

Abstract

Alloy containing between 1% and 20% by weight of Ni, between 1% and 20% by weight of Sn, between 0.5%, 3% by weight of Pb in Cu which represents at least 50% by weight of the alloy; characterized in that the alloy further contains between 0.01% and 5% by weight of P or B alone or in combination. The invention also pertains to a metallic product having enhanced mechanical resistance at intermediate temperatures (300° C. to 700° C.) and excellent machinability. The metallic product of the invention can be advantageously used for the fabrication of connectors, electromechanical, or micromechanical pieces.

1 . Alloy containing between 1% and 20% by weight of Ni, between 1% and 20% by weight of Sn, between 0.5%, 3% by weight of Pb in Cu which represents at least 50% by weight of the alloy; characterized in that
 the alloy further contains between 0.01% and 5% by weight of P or B, alone or in combination.   
     
     
         2 . The alloy according to  claim 1 , wherein
 the alloy further contains between 0.01% and 0.5% by weight of P or B alone or in combination.   
     
     
         3 . The alloy according to  claim 1 , wherein
 said alloy comprises 9% by weight of Ni, 6% by weight of Sn, 1% by weight of Pb.   
     
     
         4 . The alloy according to  claim 3 , wherein
 said alloy has a yield strength R p 0.2  essentially above 180 MPa, measured at 400° C. after heat treatment at 800° C. for about one hour, followed by a quench in water or in air.   
     
     
         5 . The alloy according to  claim 3 , wherein
 said alloy has a maximum stress R m  essentially above 333 MPa, measured at 400° C. after heat treatment at 800° C. for about one hour, followed by a quench in water or in air.   
     
     
         6 . The alloy according to  claim 3 , wherein
 said alloy has a Hv hardness essentially above 190, measured after a heat treatment at 800° C. for about one hour and subsequent aging at 320° C. for about twelve hours.   
     
     
         7 . The alloy according to  claim 1 , wherein
 said alloy comprises a second phase containing Ni, Sn, and either B or P respectively, after a heat treatment at 800° C. for about one hour, followed by a quench in water or in air.   
     
     
         8 . Production method of a metallic product composed of an alloy containing between 1% and 20% by weight of Ni, between 1% and 20% by weight of Sn, between 0.5%, 3% by weight of Pb in Cu which represents at least 50% by weight of the alloy; the alloy further containing between 0.01% and 5% by weight of P or B, alone or in combination; the method comprising the steps of:
 a) obtaining a first slug of said alloy having a homogeneous structure;   b) annealing said alloy at a temperature comprised between 690° C. and 880° C. for homogenizing and improving the alloy cold forming properties;   c) cooling at a cooling speed comprised between 50° C./min and 50000° C./min, depending on the transversal dimension of said product and composition of said alloy; and   d) cold forming.   
     
     
         9 . The method according to  claim 8 , wherein
 step a) of  claim 8  is a continuous casting process for extruding a first slug of said alloy with a diameter comprised between 25 mm and 1 mm.   
     
     
         10 . The method according to  claim 8 , wherein
 said alloy in first slug is stirred electromagnetically or mechanically in order to obtain said alloy with fine equiaxed crystals with average grain size being essentially below 5 mm.   
     
     
         11 . The method according to  claim 8 , wherein
 step a) of  claim 8  is a sprayforming process and wherein said first slug is formed with a diameter up to 320 mm and an average grain size below 200 microns.   
     
     
         12 . The method according to  claim 8 , wherein
 said cold forming step comprises a rolling, wire-drawing, stretch-forming, hammering process.   
     
     
         13 . Metallic product obtained from a production method of a metallic product composed of an alloy containing between 1% and 20% by weight of Ni, between 1% and 20% by weight of Sn, between 0.5%, 3% by weight of Pb in Cu which represents at least 50% by weight of the alloy; the alloy further containing between 0.01% and 5% by weight of P or B, alone or in combination; the method comprising the steps of: a) obtaining a first slug of said alloy having a homogeneous structure; b) annealing said alloy at a temperature comprised between 690° C. and 880° C. for homogenizing and improving the alloy cold forming properties; c) cooling at a cooling speed comprised between 50° C./min and 50000° C./min, depending on the transversal dimension of said product and composition of said alloy; and d) cold forming; wherein
 said metallic product has a tensile strength comprised between 700-1500 MPa, measured at room temperature after the annealing and cooling steps b) and c). 
 
     
     
         14 . The product according to  claim 13 , wherein
 said product has a Hv hardness comprised between 250 and 400, after the annealing and cooling steps b) and c) of  claim 13 .   
     
     
         15 . The product according to  claim 13 , wherein
 said product has a machinability index greater than 70%, in relation to standard ASTM C36000 brass.   
     
     
         16 . The product according to  claim 13 , wherein
 the product has the shape of a rod, wire, strips, slab, ingot, and sheet.   
     
     
         17 . The product according to  claim 13 , wherein
 the product is used for the fabrication of the whole or part of machined electrically conductive pieces or mechanical or micromechanical pieces.