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There is a large variety on metal materials available on the market, that it fall out of the scope of this section.
Metals can be grouped in the following major categories:
- Steels (carbon steels, tool steels, alloy steels, stainless steels, etc)
- Aluminum alloys
- Copper alloys
- Other alloyes (like Magnesium alloys, Titanium alloys, Platinum, Gold, etc)
The metals most used in the electro-mechanic industry are described more in details.
For very detailed information and data sheets please go to:
American Iron and Steel Institute or
Materials Information Resource.
Aluminum ranks second to copper in the commercial importance as an electrical conductor. Its conductivity is approximately 60 per
cent of that of pure copper. Taken on a mass basis, the conductivity of aluminum is about twice that of copper. This, as well as a
greater strength per unit weight, gives aluminum some advantage over copper as a conductor material when used as a long span of
transmission cable.
The increased diameter of an aluminum conductor necessary to carry the same amount of current of an equivalent copper conductor
tends to minimize corona losses and skin affect. This larger diameter, however, has a disadvantage since it offers a greater
resistance to wind and storm owing to its larger area.
Aluminum is high in malleability and ductility and can consequently be rolled into sheets or drawn into wire with relative ease.
it can be welded or soldered without too much difficulty provided a proper flux is used to retard the forming of a detrimental
oxide film. Of the two processes soldering is the more difficult.
Similar to copper, aluminum is very resistant to deterioration through oxidation by the formation of an initial oxide film which
prevents further oxidation. The protective coating of the oxide film is so effective that many aluminum parts to be subjected to
various corrosive atmospheric conditions are given pre-oxidation treatment through an anodizing process. This oxide film presents
difficulties where contact surfaces are to be made. Aluminum, however, is readily corroded when in contact with most metals in a
moist atmosphere due to its highly negative potential. This type of corrosion is caused by a galvanic action in which the moisture,
acting as an electrolyte, causes current to flow through the contact of the two metals while an electron transfer causes the
aluminum to go into solution.
Physical Properties of Aluminum
| Property | Value |
Electrical Conductivity at 20°C
(68°F) | 60.97% I.A.C.S. |
| Resistivity | 13.36 Microhms per sq. in. per ft. |
| Density | 2.705 grm. per cu. cm. at 20°C, .09766 lbs. per cu. in. at 20°C |
| Weight per sq. in. per ft. of length | 1.172 lb. |
| Tensile Strength | 24,000 lbs. sq. in |
| Modulus of Elasticity | 10,000,000 lbs. per sq. in. |
| Length-Temperature Coefficient | 0.000023 per Deg. C. |
| Resistance-Temperature Coefficient | 0.00403 per Deg. C. |
Copper ranks highest in commercial importance of all conductor materials. With the exception of silver, it has the highest
conductivity, volume for volume, of any other metal or substance. In addition to its high conductivity, it has sufficient
strength to be used for a limited number of structural purposes. It is easily rolled and drawn at a comparatively small
expenditure of power. Its has a high resistance to deterioration by oxidation which is due to the fact that an initially thin
surface coating of oxide protects the metal underneath from further oxidation. Copper can be brazed, soldered and tinned with
relative ease. However, it cannot be easily welded because its high thermal conductivity will not permit a sufficient temperature
build up in a concentrated area. Pure copper is not used extensively for casting owing to its high cost and the difficulty in
casting it.
Conductivity standards of copper apply to pure copper in the annealed or unrestrained condition, for as the metal is cold worked
its resistance is increased and conductivity decreased. The cold working of copper greatly increases its ultimate tensile strength
as shown by the marked difference between cast copper at approximately 24,000 lbs. per square inch and hard-drawn copper wire
which attains ultimate tensile strengths as high as 70,000 lbs. per square inch. The introduction of impurities in small amounts,
likewise exhibits a marked effect on the conductivity of copper, for example, the introduction of approximately .005% of
phosphorus will depress the conductivity of copper from 100% to 94%.
Physical properties of copper
| Property | Value |
| Electrical Conductivity at 20°C (68°F) | 100% I.A.C.S., annealed; 98% I.A.C.S., hard drawn. |
| Density | 8.90 gm. per cu. cm. at 20°C.; .322 Lb. per cu. in. at 20°C. |
| Weight per sq. in. per Foot of Length | 3.864 pounds. |
| Tensile Strength | 40,000 Lb. per sq. in. |
| Young's Modulus of Elasticity | 16,000,000 Lb. per sq. in. |
| Resistance 100 ft. of 1 sq. in. cross section at 20°C | 0.000831 ohms. |
| Coefficient of Increase in Resistance, per °C | 0.000393 ohms. |
| Melting Point | 1,083°C (1981.4°F). |
| Annealing Point | 250°C (482°F) |
| Specific Heat at 25°C | 0.0918 cal. per g. per °C. |
| Thermal Conductivity at 20°C | .0923 cal. per sq. cm.
per cm. per sec. per °C. |
| Thermal Conductivity at 68°F | 223 BTU per sq. ft. per ft. per hr. per °F. |
| Average Linear Coefficient of Expansion per °C between 25°C and 100°C | 0.0000168. |
| Average Linear Coefficient of Expansion per °F between 77°F and 212°F | 0.0000093. |
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