Exam review

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Strength
Solid solution strengthening of copper is a common procedure.  Small amounts of an alloying element added to molten copper will completely dissolve and form a homogeneous microstructure (a single phase).  At some point, additional amounts of the alloying element will not dissolve; the exact amount is dependent on the solid solubility of the particular element in copper.  When that solid solubility limit is exceeded, two distinct microstructures form with different compositions and hardnesses.  Copper by itself is relatively soft compared with common structural metals.  An alloy with tin added to copper is known as bronze; the resulting alloy is stronger and harder than either of the pure metals.  The same is true when zinc is added to copper to form alloys known as brass. It should be noted that neither 'brass' nor 'bronze' is a concrete, technical term.   Tin is more effective in strengthening copper than zinc, but is also more expensive and has a greater detrimental effect on the electrical and thermal conductivities than zinc.  Aluminum (forming alloys known as aluminum bronzes), Manganese, Nickel, and Silicon can also be added to strengthen copper.

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City Steel Heat Treating Co.

f16_07_pg190

Solid Diffusion Hardening:

Case Hardening  Hard Case w/ tough core

Low-C Steels

(> 0.30% C):

Carburizing,

Nitriding,

Carbonitriding

Carburized depth of 0.030” to 0.050”

in 4 hours @ 1700°F