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Select Copper Material: Composition, Purity and Alloying Elements

To optimize the electrical conductivity of copper die-cast rotors, it is necessary to use a copper alloy having very low levels of impurities. As shown in Figure 2.1.1, even low levels of most impurity elements will significantly increase the electrical resistivity of copper.

Figure 2.1.1. Influence of dissolved impurity elements on the electrical conductivity of copper at ambient temperature
(Copyright 1980 Olin Corporation. Used with Permission. All rights reserved )

Therefore, it is recommended that alloys C10100 or C11000 be used for die-casting copper rotors. As shown in Table 2.1.1, both these alloys have electrical conductivities of 101% IACS.

Table 2.1.1: Electrical conductivities of copper alloys
Alloy	Common Name	Electrical Conductivity
C10100	Oxygen free electronic copper	101% IACS
C11000	Electrolytic tough pitch copper	101% IACS

The chemical compositions of alloy C10100 is shown in Table 2.1.2, and alloy C11000 in Table 2.1.3. Additional information about these two alloys can be found in ASTM B 224, "Standard Classification of Coppers".

**Table 2.1.2:** Composition specification for alloy C10100
Element	Nominal	Minimum	Maximum
Copper	--	99.99	--
Residual deoxidants	--	None
Phosphorus	--	--	0.0003
Tellurium	--	--	0.0010
Other named elements*	--	--	--
*Hg, max., 1 ppm (0.0001%); Zn, max., 1 ppm, (0.0001%); Cd, max., 1 ppm, (0.0001%); S, max., 18 ppm (0.0018%); Pb, max., 10 ppm (0.0010%); Se, max., 10 ppm (0.0010%); Bi, max., 10 ppm (0.0010%); Oxygen max., 10 ppm (0.0010%) The total of the seven following elements, Se, Te, Bi, As, Sb, Sn and Mn not to exceed 40 ppm, (0.0040%).

**Table 2.1.3:** Composition specification for alloy C11000
Element	Nominal	Minimum	Maximum
Copper (inc. silver)	--	99.90	--
Oxygen	0.04	--	--