Metal Properties

Specific Gravity and Density: Specific gravity is the ratio of mass of any material to that of the same volume of water at 4 °C. Density is the unit mass of material to that of volume at some reference temperature, usually 20 °C. The numerical values, for all practical purposes, when density is expressed in g/cu.cm is same.

Density and Weight of Copper: Pure copper, rolled, forged or drawn and then annealed, has a density of 8.89 g/cm³ at 20 °C or 8.90 g/cm³ at 0 °C. Samples of high conductivity copper usually will vary from 8.87 to 8.91 and occassionally from 8.83 to 8.94. Variation in density may be caused by microscopic flaws or seams or the presence of scale or some other defect; the presence of 0.03 % oxygen will cause a reduction of about 0.01 in density. Hard drawn copper has about 0.02 % less density than annealed copper, on average, but for practical purposes, the difference is negiligible.

The international standard of density, 8.89 at 20 °C, corresponds to a weight of 0.32117 lb/in³.

Copper Alloys: Density and mass of copper alloy varies with the composition. For hard-drawn wire covered by ASTM specification B105, the density of alloy 85 to 20 is 8.89 g/cm³ at 20 °C; alloy 15 is 8.54; alloy 13 and 8.5 are 8.78.

Copper Clad Steel: Density and weight of copper-clad steel wire is a mean between the density of copper and the steel, which can be calculated readily when the relative volumes or cross section of copper and steel are known. For practical purposes, a value of 8.15 g/cm³ at 20 °C is used.

Aluminium Wire: Density and weight of aluminum wire (commercially hard-drawn) is 2.705 g/cm³ at 20 °C. With less pure material there is an appreciable decrease in density on cold working. Annealed metal having a density of 2.702 will have a density of 2.700 when in hard-drawn or fully cold-worked conditions.

Aluminum-Clad Wire: Density and weight of aluminum clad wire is a mean between the density of aluminum and the density of steel, which can be calculatec readily when the relative volumes or cross sections of aluminum and steel are known. For practical purposes, a value of 6.59 g/cm³ at 20 °C is used.

Aluminum Alloys: Density and weight of aluminum alloy varies with type and compositions. For hard drawn aluminum alloy wire 5005-H19 and 620-T81, a value of 2.703 g/cm³ at 20 °C is used.

Pure Iron and Galvanised Steel Wire: Density and weight of pure iron are 7.90 g/cm³ at 20 °C. Density and weight of galvanised steel wire (EBB, BB, HTL-85, HTL-135 and HTL-195) with class A weight of zinc coating are 7.83 g/cm³ at 20 °C, with Class B are 7.80 g/cm³, and with Class C are 7.78 g/cm³.

Percent Conductivity: It is very common to rate the conductivity of a conductor in terms of its percentage ration to the conductivity of chemically pure metal of the same kind as the conductor is primarily constituted or in ratio to the conductivity of the international copper standard. Both forms of the conductivity are useful for various purposes. The ratio can also be expressed in two different terms, one where the conductor cross sections are equal and therefore termed the volume conductivity ratio and the other where the conductor masses are equal and therefore termed the mass-conductivity ratio.

International Annealed Copper Standard: The IACS is the internationally acceptted value for the resistivity of annealled copper of 100 % conductivity. The standard is expressed in terms of mass resistivity as 0.15328 Ω.g/m², or the resistance of a uniform round wire 1m long weighing 1g at 20 °C. Equivalent expressions of the IACS in various units are: 857.20 Ω.lb/mi²; 1.7241 µΩ⋅cm; 0.67879 µΩ⋅in; 10.371 Ω.cmil/ft; 0.017241 Ω.mm²/m.

The preceding values are the equivalent of 1/58 Ω.mm²/m, so the volume conductivity can be expressed as 58 S.mm²/m at 20 °C.

Electrical Resistivity: Electrical resistivity is a measure of the resistance of a unit quantity of a given material. It may be expressed in terms of either mass or volume; mathematically, mass resistivity: δ = Rm/l²; volume resistivity: ρ = RA/l; where R is resistance, m is mass, A is cross-sectional area, and l is length.