Aluminum electrical wires

Another form of failure for some materials is creep. Creep is a very slow, but permanent deformation of a material imder load. Some plastic materials are subject to creep failures. The cross-sectional area of a part may change and weaken the part as a result of creep. Another example is aluminum electrical wire. During a shortage of copper in the late 1970s, manufacturers substituted solid aluminum for solid copper in some electrical wiring applications. Tight connector screws became loose later as the local load of the connector on the aluminum wire caused creep in the aluminum material. That does not occur for copper wires. In some cases the loose connections for aluminum wires eventually led to arcing and fire. 

In the 1960s, aluminum electric wiring was used in many houses and other buildings. Over time, however, the aluminum oxidized and so the... 

Many elements are familiar to all of us. The charcoal used in outdoor grills is nearly pure carbon. Electrical wiring, jewelry, and water pipes are often made from copper, a metallic element. Another such element, aluminum, is used in many household utensils. 

If the principle behind the operation of photocopiers—the attraction of materials to a static charge—is so basic and well understood, why did it take so long to produce a practical photocopier The answer, as with many such innovations, is that the fundamental concept existed long before the materials necessary to implement the idea. Materials science is a discipline all to its own because of the virtually infinite variety of properties that the elements, as well as the substances derived from the elements, can display. Consider, for instance, the variation in the behavior of aluminum and copper (both of which are used in electrical wiring) and steel nails and galvanized nails (both of which are hit on the head). In the next chapter, we lay the differences on the table—the periodic table, that is. 

Copper and aluminum wire seem similar. Both are used in electrical wiring. But the aluminum visibly dissolves in this caustic solution, and the copper wire does not. The bubbles you observed rising from the dissolving aluminum are hydrogen, which explains why thin strips of aluminum foil are added to some lye-based drain cleaners to provide agitation to help break up clogs. 

Electricity flows through silver more easily than it does through any other metal. In most cases, however, metals such as copper or aluminum are used because they are less expensive. But sometimes, an electrical device is so important that cost is not a consideration. For example, electrical devices on spacecraft, satellites, and aircraft must work reliably and effi-ciendy. The cost of using silver is not as important as it would be in a home appliance. Thus, silver is used for electrical wiring and connections in these devices. 

Copper is a typical metal. It is lustrous (although it tarnishes readily) it is an excellent conductor of electricity (it is widely used in electrical wires) and it is readily formed into various shapes, such as pipes for water systems. Copper is one of the transition metals—the metals shown in the center of the periodic table. Iron, aluminum, and gold are other familiar elements that have metallic properties. All of the elements shown below and to the left of the heavy "stair-step" black line in Figure 3.7 are classified as metals, except for hydrogen (see Figure 3.9). 

What is an element Elements are all around us. The element iron is in everything from bridges to safety pins. Electric wire is made from the element copper. Cans are made from the element aluminum. The lead in pencils is not really lead. It is graphite. This is the element carbon. Even the air we breathe is made of elements. It is mostly nitrogen and oxygen. 

Copper is a good conductor of electricity. It is often used for electric wires. Iron is very strong. So iron and steel are often used to build skyscrapers, bridges, and other structures. Aluminum is strong, too. It is lighter than iron. It is used in structures that need to be both light and strong, such as airplane frames. 

Copper, however, is used in applications where purity is important. Copper, when pure, is ductile and an excellent electrical conductor, so it needs to be refined to be used in electrical wiring. Copper anodes (blister copper) are suspended in a water solution containing sulfuric acid and copper sulfate with steel cathodes. Electrolysis results in dissolution of copper from the anode and migration of copper ions to the cathode, where purified metal is deposited. The result is copper of 99.9 percent purity. A similar procedure may be used in recycling copper. Other metals that are electrorefined include aluminum. 

For electrical wire and cables, the combination of conductivity and low weight is very important. In the metallurgical industry, aluminum is used as a deoxidation agent in steel manufacturing (see Chapter 8 Iron) and as an alloying element in magnesium, titanium and copper alloys. 

C. What problems are associated with the buildup of aluminum oxide on electrical wiring made of aluminum ... 

Copper is normally used for electrical wiring in residential and commercial buUdings. However, between 1965 and 1973, the price of copper increased significantly and, consequently, aluminum wiring was installed in many buildings constructed or remodeled during this period because aluminum was a less expensive electrical conductor. An inordinately high number... 

Table 18.2 Compositions, Electrical Conductivities, and Coefficients of Thermal Expansion for Aluminum and Copper Alloys Used for Electrical Wiring...

Coefficient of thermal expansion values, as well as compositions and other properties of the aluminum and copper alloys used for electrical wiring, are presented in Table 18.2. 

Building Wires. These wires conduct electricity at relatively low voltages (eg, 110 V and 220 V). Typically they contain a metallic conductor (copper or aluminum) that is insulated with polymeric compounds based on polyethylene or PVC which are appHed over a conductor using an extmder. 

High purity 50% ferrosihcon containing <0.1% Al and C is used for production of stainless steel and corded wire for tires, where residual aluminum can cause harm fill alumina-type inclusions. These are also useflil in continuous cast heats, where control of aluminum is necessary. High purity grades of 50 and 75% ferrosihcon containing low levels of aluminum, calcium, and titanium are used for sihcon additions to grain-oriented electrical steels, where low residual aluminum content contributes to the attainment of desired electrical properties, eg, significant reduction of eddy currents. 

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