• Ease of post-casting processing, because good surface fi nish and high tolerance control are readily achieved. In addition, many cast copper alloys are polished to a high luster, and plating, solder- ing, brazing and welding also are routinely performed.


• Large alloy choice; several alloys may be suitable candidates for any given application.


• Comparable costs to other metals due to their high yield, low machining costs and little requirement for surface coatings, such as paint.


• Good castability, as all copper alloys can be sand cast and many can be centrifugal, continuous, permanent mold or die cast.


Figure 2 shows a brass casting that was converted from a 10-piece fabrication. In this case, the permanent mold casting process produced better dimensional accuracy and reproduc-


Fig. 3. Copper allows for complex casting designs, such as this connector with fi ns, slots and cast-in holes.


ibility. Additionally, with the near-net- shape features, weight and secondary machining can be minimized. Depending on the requirements of


a particular cast component, copper- based alloys have a range of mechani- cal and physical properties. Table 1 shows the full listing of cast copper- base alloys, including properties and end-use applications.


Designing With Copper Alloys


T e choice of alloy and casting method (sand, permanent mold, die or investment casting) determines the mechanical and physical properties (Table 1), section size, wall thickness and surface fi nish that can be achieved. Typical properties of common copper alloys are shown in Table 2. T e rules in design of thick and thin sections are simple: avoid design- ing a casting that contains both thick and thin sections. When such changes are necessary, the thicker section


32 | METAL CASTING DESIGN & PURCHASING | Mar/Apr 2015


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