Cu-Ni-Zn-Mn Alloy

Abstract

Precipitation hardened alloy on the basis of copper, zinc, nickel and manganese exhibiting a high strength and ductility with values similar to those of stainless steels in combination with excellent machinability. The inventive alloy family is characterized by fine fibre-like or globular precipitates that emerge during intermediate temperature annealing treatments, which in case of the unleaded variations significantly improves the machinability. The alloy of invention is particularly suited for free machining applications such as the production of pen tips and reservoirs for writing implements of reduced tip dimensions, where conventional Cu—Ni—Zn—Mn alloys fail due to lack of strength and where the corrosion resistance in gel-based inks is insufficient without restriction to other fields of application.

What is claimed is: 
     
         1 - 23 . (canceled) 
     
     
         24 . A precipitation hardenable copper alloy comprising, in percentage of weight, between 43.5 and 48 wt. % Cu, between 36 and 40 wt. % Zn, between 9 and 12 wt. % Ni, between 5 and 7 wt. % Mn, 2.0 wt. % or less of Pb, 1.0 wt. % or less of Al, 2.0 wt. % or less of Sn, between 0.05 and 0.5 wt. % of Fe, 0.2 wt. % or less of Si. 
     
     
         25 . The copper alloy according to  claim 24 ,
 further comprising 0.15 wt. % or less of As.   
     
     
         26 . The copper alloy according to  claim 24 ,
 having tensile strength values above 800 MPa and elongations above 5% when subjected to a low temperature heat treatment comprised between about 300° C. and about 450° C.   
     
     
         27 . The copper alloy according to  claim 26 , wherein
 having a beta phase precipitated in a fine needle-like structure when subjected to the low temperature heat treatment.   
     
     
         28 . The copper alloy according to  claim 24 , wherein
 the presence of Al and Sn results in a high volume fraction of beta during a hot deformation, and which can be reduced during intermediate temperature annealing for allowing good cold formability, and NiSn-rich precipitates and or Ni—Al rich precipitates when submitted to a low temperature heat treatment comprised between about 300° C. and about 450° C.   
     
     
         29 . The copper alloy according to  claim 24 ,
 having hardness values comprised between 190 and 320 HV, tensile strength comprised between 550 and 700 MPa, and elongation greater than 25% when the alloy is subjected to a high temperature heat treatment comprised between 500 and 700° C.   
     
     
         30 . The copper alloy according to  claim 24 ,
 having tensile strength greater than 800 MPa and tensile elongation greater than 5% when the alloy is subjected to a low temperature heat treatment comprised between 300 and 450° C.   
     
     
         31 . The copper alloy according to  claim 24 ,
 having a microstructure containing fine-grained needle-like or globular-like precipitates of similar composition or different composition than the matrix and with grain size below 5 micron when the alloy is subjected to a low temperature heat treatment comprised between 300 and 450° C.   
     
     
         32 . A precipitation hardenable copper alloy comprising between 45 and 48 wt. % Cu, between 36 and 40 wt. % Zn, between 9 and 14 wt. % Ni, between 4 and 7 wt. % Mn, between 0.05 and 0.5 wt. % Fe, 1.5 wt. % or less of Ca, 1.0 wt. % or less of Si, 1.0 wt. % or less of Al, 0.15 wt. % or less of As, and 0.1 wt. % or less of Pb. 
     
     
         33 . The copper alloy according to  claim 32 , wherein
 Ca forms precipitates with Cu and/or Zn in a pure alpha or a duplex alpha/beta structure.   
     
     
         34 . Copper alloy product, comprising a copper alloy comprising, in percentage of weight, between 43.5 and 48 wt. % Cu, between 36 and 40 wt. % Zn, between 9 and 12 wt. % Ni, between 5 and 7 wt. % Mn, 2.0 wt. % or less of Pb, 1.0 wt. % or less of Al, 2.0 wt. % or less of Sn, between 0.05 and 0.5 wt. % of Fe, 0.2 wt. % or less of Si. 
     
     
         35 . The copper alloy product according to  claim 34 ,
 comprising wires, rods, strips, and rectangular shapes and profiles.   
     
     
         36 . The copper alloy product according to  claim 35 ,
 being obtained via casting, hot extrusion and successive cold drawing and heat treatment steps.   
     
     
         37 . The copper alloy product according to  claim 35 , wherein
 wires have a final diameter smaller than 2.5 mm.   
     
     
         38 . The copper product according to  claim 34 ,
 comprising a writing implement.   
     
     
         39 . The copper product according to  claim 38 , wherein
 said writing implement comprises a pen tip, a tip socket and/or reservoir for pen tips to be filled with either oil-based, gel-based inks or other liquids