Copper Hard-drawn

Copper Copper, hard drawn 13 None (bent copper) 0.67... 

TABLE 10-34 Hard-Drawn Copper Threadless Pipe (ASTM B302) ... 

The 1-cm rods of copper are drawn through successively smaller dies until the desired size of wire is reached. The dies must be made of exceptionally hard materials because of the tremendous amount of wear from drawing the wire. The dies typically are made of tungsten carbide or diamond. 

Copper and aluminium are used in their highly refined form for the power conductors of cables. The total impurities contained in high conductivity copper should be less than 0.1% and for aluminium less than 0.5%. The measured conductivity of these metals will have its highest value when they are annealed. Hard drawn conductors will have conductivity that is several percentage points lower than the annealed value. Note that castings made of these materials will generally have conductivity slightly lower than their rolled and drawn forms. 

Cast copper does not have outstanding mechanical properties. Work hardening by rolling or drawing improves these properties. In sizes typical of chlor-alkali busbars, hard-drawn copper bars or strips have tensile strengths of about 2.5 tons cm . Cold working destroys about 2-3% of the maximum electrical conductivity. Annealing restores this at the expense of some of the enhanced physical properties [18]. 

Many different types of conductors are used on overhead distribution lines. They vary both in size and number, depending on the voltage level and the type of circuit. Copper, aluminum, and steel are the most commonly used material for overhead lines. Copper is used in three forms hard drawn, medium-hard drawn, and soft drawn or annealed. Hard-drawn copper has the greatest strength and is used for circuits of relatively long spans (200 ft or more). However, its inflexibility makes it harder to work with. The soft-drawn variety is the weakest of the copper conductors. Its use is limited to short spans. The medium-hard-drawn copper conductor has found more widespread use in the medium range distribution circuits. 

The most common conductor alloy (1350) offers a minimum conductivity of 61.8% of the International Annealed Copper Standard (lACS) and from 55 to 124 MPa (8 to 18 ksi) minimum tensile strength, depending on size. When compared with lACS on the basis of mass instead of volume, minimum conductivity of hard drawn aluminum 1350 is 204.6%. Other aUoys are used in bus bar, in service at slighdy elevat temperatures, and in cable television installations. 

Evidence bears this out. A pure metal, such as sodium, is soft enough to be cut with a butter knife. Other pure metals, such as copper or gold, can be drawn into wires or hammered into sheets. Ionic compounds, by contrast, are hard and brittle. 

The chemicals leached from these surfaces depend on the corrosive properties of the particular water as well as the chemical nature of the surface. Hard water tends to deposit a mineral layer on the inside of pipes and on other surfaces that essentially limits the access of water to the surfaces. On the other hand, soft water, particularly at lower pHs, can actively dissolve toxic metals such as lead or cadmium from pipes or solder. Copper in pipes is also frequently leached from pipes at high concentrations when the water has corrosive properties. Asbestos-cement has been used widely in water mains. The extraction of the asbestos fibers from these surfaces is also very much increased at lower pH and with soft water. The use of lead pipe and solder in household pipes has pretty much been abandoned in the United States. However, alloys of lead are still utilized in many faucets and brass fixtures (e.g., submersible pumps). Rather high concentrations of lead can result if water stands in these fixtures overnight. As a result it is always wise to avoid using the water first drawn from the tap in the morning for human consumption. Low levels of lead exposure in utero or in the first few years of life have been associated with delayed CNS development in humans and experimental animals. 

Figure 12-18. Degree of contact for a hard spherical indenter pressed into the flat, rough surface of an unconstrained deformable body. The data divide into two classes. Homogeneous solids drawn rod aluminum, bead blasted A cold rolled aluminum, bead blasted cold rolled aluminum, bead blasted and then annealed Ygold, bead blasted and then annealed work-hardened turned copper. Degree of 0.007. Solids with hardened surface layers aluminum, bead blasted. Degree of contact ranged Data by Williamson and Hunt [16].

Cerium particles ignite in air but cerium metal is soft and sparks cannot be drawn from it. CeFe2 with small amounts of magnesium, copper, and tin makes an excellent lighter flint material because it is hard and brittle. 

The substance mixed with dried copper oxide was burnt in the hard-glass tube A, heated with burning charcoal in the sheet-iron pan. Water was collected in the calcium chloride tube B and carbon dioxide in the potash bulbs D, protected from loss of moisture by another calcium chloride tube E weighed with D. After the combustion the drawn-out tip of A was broken off and a slow stream of air aspirated through the apparatus. 

---