High-purity coppers and most of the copper-based alloys have good continuous teristics and are produced in the form of rod, strip and hollow .Because of the exceptional trigh toxicity of cadmium, stringent environment controls are mandatory, hence the necessity to find suitable alternative material.
High-Purity Copper
Oxygen-free high-conductivity copper (B51400 HCC1) is produced extensively in billet or rod form by continuous casting. Very low impurity levels in the product are assured by using as feedstock high-grade cathode (Cu-Cath-l).
Continuous Casting of Cu : Cd Alloys and Cu: Mg Alloys
Cu: Cd Alloys
Extensive use is made of copper-cadmium alloys as electric trolley wire. The Material used as an alternative to oxygen-free copper based on higher strength while still maintaining high electrical conductivity. Continuous casting of the CDA alloys C16200 and C16201 in the form of rod is rally in the horizontal mode. More recently the upcast technique has been applied
Cu: Mg Alloys
The Cu: Cd alloys mainly as rod for electrical transmission line and trolley wire. The tensile strength electrical conductivity, although not entirely meeting those of the Cu: Cc 5, are comparable.
Copper - Tin Alloys
The tin bronzes differ considerably from the brasses insofar as relationship between thermal equilibria and actual structure in the cast condition. In true equilibrium an tin alloy would solidify entirely as a solid solution. In practice under normal casting conditions the wide freezing range causes extensive segregation to occur and the last liquid to solidify is so enriched in tin that it freezes by peritectic reaction at 798°Cto form B. On cooling further the B transfonns again.
Examining the binary Cu-Sn diagram in equilibrium there would be a series of eutectoid reactions where B would transform to a and y at 586°C (HIJ), then the y would transform to a and 15 at a temperature of 520°C (KLM) and finally the dlly the g the binary Cu-Snediagram in equilibrium there would be a series of eutectoid reactdons where B would >ranseorm to a and y at 586°C (HIJ), then the y would transform to a and 15 at a temperature of 520°C (K The d phase is an intermetallic compound Cu31Sn8 and is hard and brittle. The a+ d eutectoid is present as blue/grey phase evenly distributed in bearing bronze to give excellent wear resistance.
Copper-Tin-Phosphorus Alloys
In many of the copper -tin alloys phosphorus is added. Phosphorus is a strong deoxidiser, increasing fluidity and producing an alloy with increased tensile strength and wear resistance. A vertical section through Cu-Sn-P diagram at 5% tin. Phosphorus is present as copper phosphide Cu3P which forms by a eutectic reaction, appearing in the microstructure as a skeleton-like structure with the a+ d eutectoid. Cast phosphor bronzes containing up to 13 wt% tin and up to 1.0wt% phosphorus are used mainly for heavy -duty bearing where low coefficient of friction and high strength and toughness are required.
Copper Aluminium Alloys
The copper-aluminium alloys, known as aluminium bronzes, form an important group of engineering materials, characterised by their high strength and corrosion resistance. A solid solution containing up to 9.4+wt% Al with a narrow freezing range similar to the brasses forming a peritectic at 1037°C and 8.5wt% Al. Alloys containing less than 8% aluminium are single-phase a alloys. Solidification commences with the formation of a dendrites. The freezing range is short with the as-cast structure being essentially single phase. Segregation is not pronounced.
The alloy containing 10% aluminium solidifies as B depositing a as the line DR is crossed and at 565°C the remaining B decomposes to form lamellar eutectoid a +y2. The reaction is, of course, diffusion controlled, and normal casting rates result in the retention of B. The alloys we consider in continuous casting have lower aluminium contents forming an all-a structure.
Copper-Nickel Alloys
There are two commercially important groups of copper-nickel alloys in the 90/10 and 70/30 ranges both having exceptional corrosion resistance in sea water. With either, 1 or 2% each of iron and manganese is added for a further improvement in corrosion resistance. In this form they are particularly useful for sea water condenser systems and for cladding off-shore structures. A further group of alloys in commercial use is based on Cu-3% Ni. These alloys are used for electrical connectors and springs.
The Cu: Ni alloys are an example of complete miscibility in the solid and liquid states. All the alloys have identical single-phase structures. In the cast condition the wide freezing range gives rise to heavily cored dendrites and as the two elements inter-diffuse slowly, segregation usually persists.
