In view of titanium's high melting temperature,
BRASS.--Brass is a copper alloy containing zinc
approximately 3,300F, its high-temperature properties
and small amounts of aluminum, iron, lead,
manganese, magnesium, nickel, phosphorous, and tin.
are disappointing. The ultimate and yield strengths of
titanium drop fast above 800F. In applications where
Brass with a zinc content of 30 to 35 percent is very
ductile, while that containing 45 percent has relatively
the declines might be tolerated, the absorption of
high strength. "Muntz metal" is a brass composed of 60
oxygen and nitrogen from the air at temperatures
percent copper and 40 percent zinc. It has excellent
above 1,000F makes the metal so brittle on long
corrosion-resistant qualities when in contact with salt
exposure that it soon becomes worthless. Titanium
water. Its strength can be increased by heat treatment.
has some merit for short-time exposure up to
As cast, this metal has an ultimate tensile strength of
2,000F where strength is not important, as in aircraft
50,000 psi and can be elongated 18 percent. It is used in
fire walls.
making bolts and nuts, as well as parts that come in
Sharp tools are essential in machining techniques
contact with salt water. "Red brass," sometimes termed
because titanium has a tendency to resist or back away
bronze because of its tin content, is used in fuel and oil
from the cutting edge of tools. It is readily welded, but
line fittings. This metal has good casting and finishing
the tendency of the metal to absorb oxygen, nitrogen,
properties and machines freely.
and hydrogen must never be ignored. Machine welding
BRONZES.--Bronzes are copper alloys contain-
with an inert gas atmosphere has proven most
ing tin. The true bronzes have up to 25 percent tin, but
successful.
those below 11 percent are most useful, especially for
Both commercially pure and alloy titanium can
such items as tube fittings in aircraft.
absorb large amounts of cold-work without cracking.
Among the copper alloys are the copper aluminum
Practically anything that can be deep drawn in
alloys, of which the aluminum bronzes rank very high
low-carbon steel can be duplicated in commercially
in aircraft usage. They would find greater usefulness in
pure titanium, although the titanium may require more
structures if it were not for their strength/weight ratio as
intermediate anneals.
compared with alloy steels. Wrought aluminum
IDENTIFICATION O F T I TA N I U M . --
bronzes are almost as strong and ductile as
Titanium metal, pure or alloyed, is easily identified.
medium-carbon steel, and possess a high degree of
When touched with a grinding wheel, it makes white
resistance to corrosion by air, salt water, and chemicals.
spark traces that end in brilliant white bursts. When
They are readily forged, hot- or cold-rolled, and some
rubbed with a piece of glass, moistened titanium will
react to heat treatment.
leave a dark line similar in appearance to a pencil mark.
These copper-based alloys contain up to 16 percent
of aluminum (usually 5 to 11 percent) to which other
Copper and Copper Alloys
metals such as iron, nickel, or manganese may be
added. Aluminum bronzes have good tearing qualities,
Most commercial copper is refined to a purity of
great strength, hardness, and resistance to both shock
99.9 percent minimum copper plus silver. It is the only
and fatigue. Because of these properties, they are used
reddish-colored metal, and it is second only to silver in
electrical conductivity. Its use as a structural material is
and slide liners. Aluminum bronzes are available in
limited because of its great weight. However, some of
rods, bars, plates, sheets, strips, and forgings.
its outstanding characteristics, such as its high
electrical and heat conductivity, in many cases
Cast aluminum bronzes, using about 89 percent
overbalance the weight factor.
copper, 9 percent aluminum, and 2 percent of other
elements, have high strength combined with ductility,
Because it is very malleable and ductile, copper is
and are resistant to corrosion, shock, and fatigue.
ideal for making wire. In aircraft, copper is used
Because of these properties, cast aluminum bronze is
primarily for the electrical system and for instrument
used in gun mounts, bearings, and pump parts. These
tubing and bonding. It is corroded by salt water, but is
alloys are useful in areas exposed to salt water and
not affected by fresh water. The ultimate tensile
corrosive gases.
strength of copper varies greatly. For cast copper, the
tensile strength is about 25,000 psi; and when
Manganese bronze is an exceptionally
cold-rolled or cold-drawn, its tensile strength increases,
high-strength, tough, corrosion-resistant copper zinc
ranging from 40,000 to 67,000 psi.
alloy containing aluminum, manganese, iron, and
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