COPPER AND COPPER-BASE ALLOYS 



CHAPTER I 

 THE COPPERS 



Electrolytic tough-fitch copper is the type of copper 

 most widely used in industrial applications in the United 

 States. Such copper contains controlled amounts of 

 cuprous oxide introduced during refining. The cuprous 

 oxide, which ordinarily is present in amounts ranging from 

 0.02 to 0.05 per cent, causes the copper to take a "level 

 set" on sohdif}dng and does not impair its electrical 

 conductivity or materially affect its physical properties. 



Oxygen-free copper (high-conductivity and low-conduc- 

 tivity). The following oxygen-free coppers have been 

 developed during the past several years: 



1. An oxygen-free copper that is prepared by melting 

 and casting copper under special atmospheres and out of 

 contact with oxygen. 



2. An oxygen-free copper that is prepared by melting 

 cathodes and removing oxygen by the judicious use of 

 phosphorus. A residual phosphorus content of under 

 0.01 per cent is maintained. 



3. Coalesced copper — manufactured by cpmpressing 

 specially prepared granular cathodes in a reducing 

 atmosphere while hot and then extruding through a die 

 into commercial shapes without any previous melting. 



4. Copper which is deoxidized with calcium boride 

 or other such deoxidants and which contains no residual 

 deoxidant. 



5. Copper that is deoxidized with phosphorus and 

 contains between 0.01 and 0.03 per cent residual phos- 

 phorus. This is the common type of " phosphorized 

 copper." 



Types 1, 2, 3, and 4 are known as "high-conductivity 

 oxygen-free copper" because they possess electrical con- 

 ductivities sufficiently high to meet A.S.T.M. and other 

 specification requirements for use as electrical conductors. 



Type 5 is known as "low-conductivity oxygen-free 

 copper" because of the lower electrical conductivity 

 incidental to the phosphorus content. 



Lake or silver-hearing copper derives its name from the 

 fact that large deposits of this type of copper were located 

 in the vicinity of Lakes Superior and Michigan. Lake 

 copper usually contains silver in amounts ranging from 

 7 to 30 ounces per ton and may or may not contain arsenic 

 from 0.001 to 0.50 per cent, depending upon the exact 

 source of the ore. Natural Lake copper is fire-refined 

 to a high degree of purity, and some types have suffi- 

 ciently high electrical properties to be suitable for 

 electrical conductors. Because the Lake deposits have 

 been extensively worked and are approaching exhaustion, 



it has become the practice recently to add silver to 

 electrolytic copper. Such copper is known as "synthetic 

 Lake" or "silver-bearing" copper. 



In addition to the coppers of major importance, already 

 mentioned, the following special coppers are of com- 

 mercial significance: 



1. Arsenical copper — in which arsenic in controlled 

 amounts up to 0.60 per cent is added to electrolytic 

 cathode copper for the purpose of improving certain 

 mechanical properties and properties of corrosion 

 resistance. Oxygen may or may not be present. 



2. Tellurium copper — in which tellurium in amounts up 

 to 0.75 per cent is added to previously deoxidized copper 

 to produce free-cutting properties without impairing 

 too seriously electrical conductivity or hot-working 

 properties. 



3. Leaded copper — in which 1 per cent or more lead is 

 added to previously deoxidized copper for the purpose 

 of imparting free-cutting properties without seriously 

 impairing electrical or thermal conductivities, but with 

 a sacrifice of hot-working properties. 



The coppers, with the exception of leaded copper, are 

 exceptionally plastic through a wide range of temperature 

 and possess no critical range in which plasticity is 

 seriously reduced. It is comjnercial practice to hot-roll 

 copper through a temperature range of 1200 to 1650°F. 

 as this is the range of maximum plasticity. Copper, 

 with the above exception, may be hot-worked by any 

 of the commercial fabricating methods. 



The coppers possess almost unlimited capacity for 

 being cold-worked. However, although it is common 

 practice in the manufacture of certain types of products 

 to effect reductions of 90 per cent without intermediate 

 annealing, copper that is to be used for deep drawing 

 or stamping operations is usually brought to its final 

 gage by reductions not exceeding 50 per cent of its cross- 

 sectional area. 



Copper to be used for drawing, stamping, or forming is, 

 of course, supplied in the annealed condition. Copper 

 is annealed at temperatures between 450 and 1500°F., 

 depending on the properties desired. Those grades of 

 copper which contain oxygen must not be annealed in 

 reducing atmospheres as under such conditions copper 

 becomes gassed, i.e., the copper oxide eutectic is reduced 

 to pure copper leaving voids or fissures (see Figs. 1 and 2). 

 Copper that has been gassed is completely lacking in 

 ductility and unsuited for further use. Those grades 



