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Types of Copper and Properties
The copper most commonly used for sheet and strip applications complies with ASTM B370. It consists of 99.9 percent copper, and is available in six tempers designated by ASTM B370 as: 060 (soft), H00 (cold rolled), H01 (cold rolled, high yield), H02 (half hard), H03 (three quarter hard), and H04 (hard).
Soft temper copper is extremely malleable and best suited for applications such as intricate ornamental work. It was historically used in building construction. Because of its low strength, heavy gauge material was required. As a result, the use of soft temper copper is not recommended for most building applications.
With the development of cold rolled copper many years ago, the gauge of the material could be reduced without compromising its low maintenance and long life. Cold rolled temper is less malleable than soft temper copper, but is much stronger. It is by far the most popular copper temper currently used in construction. The properties of cold rolled copper are summarized in Table 1.1.1a.
|Specific Gravity||8.89 - 8.94|
|Density||0.322lb./cu. in. at 68°F|
|Thermal Conductivity||226 BTU/Sq Ft/Ft/Hr °F at 68°F|
|Coefficient of Thermal Expansion||0.0000098/°F from 68°F to 572°F|
|Modulus of Elasticity (Tension)||17,000,000 psi|
|Tensile Strength||32,000 psi min.|
|Yield Strength (0.5% Extension)||20,000 psi min.|
|Elongation in 2" - approx.||30%|
|Shear Strength||25,000 psi|
Rockwell (F Scale)
Rockwell (T Scale)
The significant properties of the six ASTM B370 designated tempers are summarized in Table 1.1.1 b.
In general, cold rolled 1/8 hard temper (H00) copper is recommended for most roofing and flashing installations. Soft copper may be used where extreme forming is required such as in complicated thru-wall flashing conditions. However, it should be noted that cold rolled copper offers far more resistance than does soft to the stresses induced by expansion and contraction. Copper roof sheet of higher temper should be specified only if indicated for specific and engineering applications requiring such higher tempers.
|Temper Designation Standard||Tensile Strength (Ksi)||Yield Strength (Ksi) Min.|
|H00 Cold-Rolled 1/8 Hard||32||40||20|
|H01 Cold-Rolled, high yield 1/4 Hard||34||42||28|
|H02 Half Hard||37||46||30|
|H03 Three quarter Hard||41||50||32|
The yield strength of cold-rolled high yield (H01) copper is significantly higher than standard cold rolled (H00) copper, up to 33,000 p.s.i. This allows the use of 12 ounce high yield copper in many applications where 16 ounce cold rolled copper is normally used.
The major use for high yield copper is flashing products, where malleability and strength are both important.
Another variation of copper is lead coated copper sheet and strip. The base metal is usually cold rolled copper, onto which lead has been applied. The lead coating is applied by dipping the sheet or strip into a bath of molten lead.
Good resistance to corrosion, good electrical and thermal conductivity, ease of fabrication coupled with strength and resistance to fatigue are criteria by which copper or one of its alloys is selected.
Corrosion Resistance: Copper is a noble metal able to resist attack quite well under most corrosive environmental conditions. In the presence of moisture, salt and high sulfur pollution, copper quickly begins to oxidize and progress through the weathering cycle. Its high resistance to corrosion is due to its ability to react to its environment and reach weathering equilibrium.
Electrical and Thermal Conductivity: Copper and its alloys are excellent conductors of electricity and heat. In fact, copper is used for these purposes more often than any other metal. Alloying invariably decreases electrical conductivity and to a lesser extent, thermal conductivity. Coppers and high-copper alloys are preferred over copper alloys containing more than a few percent total alloy content when high electrical or thermal conductivity is required.
Ease of Fabrication: Copper and its alloys are generally capable of being shaped to the required form and dimensions by any of the common fabricating processes. They are routinely rolled, stamped, drawn and headed cold; they are rolled, extruded, forged and formed at elevated temperature.
Copper and its alloys are readily assembled by any of the various mechanical or bonding processes commonly used to join metal components. Crimping, staking, riveting, and bolting are mechanical means of maintaining joint integrity. Soldering, brazing and welding are the most widely used processes for bonding copper metals. Selection of the best joining process is governed by service requirements, joint configuration, thickness of the components, and alloy composition(s).
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