Bronzes: Properties of bronzes, Phosphor Bronze, Silicon bronze, Beryllium bronze, Manganese bronze, Aluminium Bronze

Bronzes

Bronze is a common alloy of copper and tin.
The alloys of copper and tin are generally
termed
as bronzes. The wide range of composition of these alloys comprise of 75
to 95% copper
and    5 to 25% tin.

Properties of bronzes

Bronze has higher strength,
better corrosion resistance than brasses. It is comparatively hard and resists surface
wear and can be shaped or rolled into wire, rods and sheets very
easily. It has antifriction or bearing properties. Bronze is costlier than brass. The tensile strength of bronze
increases gradually with the amount of tin, reaching a maximum when
tin is about 20%. However the percentage of
tin content if increases beyond this amount,
the
tensile strength decreases very rapidly.
Bronze is most ductile when it contains about 5% of tin. As the amount of tin increases about 5%, the ductility gradually
decreases and practically disappears with about 20% of
tin. Whereas presence of zinc in the bronze increases fluidity
   of molten metal, strength and ductility.

Some of the common types of bronzes are
discussed as under:

Phosphor Bronze

When bronze contains phosphorus in very small amount,
then phosphor bronze is produced.

A common type of phosphor bronze has the following
composition. 
Cu  
=   89 to 94% , Sn 
=   6  to 10% and P 
=   0.1  to 0.3%

Properties of Phosphor Bronze

Tensile strength, ductility,
elasticity,
soundness of castings, good
wearing quality and resistance to fatigue of phosphor bronze increases with increase of phosphorus in bronze. This material possesses good corrosion
resistance especially for sea water, so
that it is much used for propeller
blades. Phosphor bronze of proper composition can be easily casted, forged,
drawn, and cold rolled.

Applications of Phosphor Bronze

Phosphorus bronze is used making
for bolts, electric contact springs, bearings, bushes, gears, ship sheathing,
valve parts, propeller blades, worm wheels, gears, nuts for machine lead
screws, pump parts, linings and for many other purposes. It is also suitable
for making springs and corrosion resistance mine cables. 

 Silicon bronze

Silicon bronze contains Cu = 96%, Si   =
 3%, 
Mn 
or  Zn  =  1%

Silicon bronze has good general
corrosion resistance of copper combined with higher strength. It can be cast,
rolled, stamped, forged and pressed either hot or cold and it can be welded by
all the usual methods.

Applications of Silicon bronze

Silicon bronze is widely
used for making
boilers, tanks, stoves
or where high strength and good corrosion
resistance is required.
It is used also for making screws,
tubing’s, pumps etc.  

Beryllium bronze

Beryllium bronze is a copper base alloy
contains Cu = 97.5%, Br = 2.5%

Beryllium bronze possesses
higher tensile strength than other bronzes. It possesses excellent corrosion
resistance. It is having high yield point and high fatigue limit. It is having good hot and cold resistance. This can be heat treated
by precipitation hardening. It possesses
excellent formability in soft condition, and high fatigue and creep resistance
in hardened condition.
However it involves high cost.

Applications of Beryllium bronze

Beryllium bronze is particularly suitable
material for making
springs, tubes, diaphragms and electrical contacts, heavy duty electrical switches, cams and bushings. This is used for

springs, heavy duty electrical switches, cams and bushings. Having
non-sparking characteristics,
it
is used for making chisels and hammers using for such conditions where spark
might cause explosion. It has a film forming and a soft lubricating property, which makes it more suitable as
a bearing metal. Since the wear resistance of beryllium copper is five times
that of phosphorous bronze, therefore it is used as a bearing metal in place of
phosphor bronze.

 Manganese bronze

Manganese bronze is an alloy of copper, zinc
and little percentage of manganese. The usual composition of this bronze is Copper   =
 60%, 
Zinc   =
 35%, 
Manganese = 5%

Manganese bronze is highly resistant
to corrosion. It is stronger
and harder than phosphor
bronze.

Applications of Manganese bronze

Manganese bronze is mainly used for bushes, plungers, feed pumps,  rods  etc. Worm
gears are frequently made from this bronze. 

Aluminium Bronze

Aluminium bronze possesses

Properties Cu = 85 to 88%, Al = 8 to 11%, Fe = 3% and Sn = 0.5%

The aluminium bronze with 8%
aluminium possesses very good cold working properties. When iron is added to
this metal, its mechanical properties are greatly improved by refining the
grain size and improving the ductility. The maximum tensile strength of this
alloy is 450 MPa with 11 % aluminium. This material possesses good resistance
to corrosion and it is somewhat difficult to cast due to oxidation problem.

Applications of Aluminium bronze

Aluminium bronze is generally used for making
fluid connection fittings, gears, propellers,
air pumps, bushings, tubes, slide and valves etc. Cams and rollers are commonly
produced using this
alloy.

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