Copper
Easy to work, ductile and malleable
Excellent resistance to corrosion
Good machinability
Non magnetic
Good electrical and thermal conductivity
Can be soldered, brazed and welded.
Ease of forming alloys with other elements like Zn, Sn, Al, Pb,
Si, Ni etc.
Brass- Cu-Zn
Bronze- Cu-Sn
Copper alloys
In general,
Copper plus zinc is Brass.
Any other alloy of copper other than brasses is termed as
bronze (previously only copper -tin alloy was called as brass)
Copper alloys - bronzes
Tin bronze 2-4% Zn,
8-10% Sn remaining copper
Pressure castings, bushings and bearings
Leaded tin bronze
remaining copper.
4%Zn, 6-8.5% Sn, o.5-1.5% Pb ,
Can be used upto 550 deg F
Pressure castings,bushings, electrical castings, gears , pumps
etc
High leaded tin bronze:
1-3%Zn, 5-10%Sn, 7-15%Pb
Bearings operating at high speeds and high pressure and for
corrosion resistant pumps.
Copper alloys - bronzes
Gun metal:
5-10% Sn, 2-5% Zn, remainder copper.
Good tensile strength and resistance to corrosion.
Used for bearings, steam pipe fittings, marine castings,
hydraulic valves and gears.
Simpler way to compile
2 to 5
Use lead as differentiator
8 to 10
zinc
2
4
tin
10
8.5
others
3
10
15 lead
2 to5
5 to 10
1.5lead
name
uses
Tin bronze
bushing, bearing
Leaded tin bronze use upto 550 degFelectrical castings,
bushings, bearings
high leaded tin
bearings, corrosion
bronze
resistant pumps
bearings, steam pipe
gun metal
fittings, valves
Copper alloys - bronzes
Aluminium bronze
1-4% Fe, 9-11% Al , remaining copper
For heavy duty parts, marine equipments,
gears, bearings, bushings,
valve seats, guide stems,
acid resisting pumps, parts resisting corrosion and oxidation,
Components requiring strength at elevated temperatures.
Copper alloys -brasses
Alloys of copper and zinc
Addition of zinc improves ductility and strength
Good corrosion resistance and good working properties.
1.Alpha brasses-upto 36% zinc
20-36 % -yellow
5-20%-red
2.Alpha plus beta brasses 54 to 62 % copper
Copper alloys -brasses
Yellow alpha brasses are subjected to a pitting corrosion called
dezincification.
This happens when brass is in contact with sea water or with
fresh waters that have a high content of oxygen and carbon
dioxide.
Dezincification involves dissolution of the alloy and a
subsequent deposition of non adherent copper.
This will lead to leakage through the porous layer of copper.
Small amounts of tin or antimony reduce dezincification in
yellow brasses.
Copper alloys -brasses
Stress relief anneal is done to avoid season cracking.
Season cracking or stress corrosion cracking is due to high
residual stress left in the brass after cold working.
These stresses make the brass more susceptible to
intergranular corrosion.
Intergranular corrosion:
corrosion happening preferentially at grain boundaries.
Copper alloys -brasses
Addition of 0.3 -0.5% lead improves machinability
so that leaded brass is used for
screw machine parts,
engraving plates,
keys,
lock parts,
tumblers,
gears and
watch parts.
Parts that need to be
machined to minute details
Copper alloys -brasses
Admiralty metal 71Cu-28zn-1Sn
Improved strength and corrosion resistance.
Used for condenser and heat exchanger tubes in steam power
plant equipment
Aluminium brass 76Cu-22zn-2Al
Forms a tenacious self healing film which protects the tube
against high cooling water velocities in marine and land power
stations.
Copper alloys -brasses
Cartridge brass Cu70, Zn30. and yellow brass Cu65, Zn 35
Automotive – radiator cores,headlight reflectors,
Electrical-lamp fixtures, socket shells
Hardware-fasteners, screws, rivets, springs
Ammunition components
Copper alloys -brasses
Red brasses
5-20% zinc
Better corrosion resistance than yellow brasses and are not
susceptible to stress corrosion cracking
Gliding metal 95Cu-5Zn coins, medals, tokens,emblems,
plaques, base for items to be gold plated.
Commercial brass 90Cu-10Zn excellent cold working- so used
in costume jewelry,marine hardware, forgings, rivets and
screws.
Silicon brass: 80Cu-14Zn-4Si-0.5Pb
For die cast parts and small gears
Copper alloys -brasses
Red brass 85Cu-15Zn electrical conduit, condenser and heat
exchanger tubes, plumbing pipes, nameplates etc
Low brass 80Cu-20Zn
ornamental metal work,
thermostat bellows,
musical instruments,
flexible hose,
other deep drawn articles.
Alpha plus beta brasses
These contain 54 -62 % copper
These contain two phases alpha and beta.
The beta phase is harder and more brittle at room
temperature and so difficult to cold work.
At elevated temperatures, the beta phase becomes very
plastic and so these alloys have excellent hot working
properties (when heated to the single phase beta
region).
Alpha plus beta brasses
Muntz metal 60Cu-40Zn
Rapid cooling will suppress the precipitation of alpha phase.
This can be subsequently precipitated by suitable heat
treatments.
Hence this alloy is Hardenable.
Used for
Ship sheathing, condenser heads,
perforated metal and architectural work.
Also for valve stem and condenser tubes
0.4 to 0.8 Pb improves machinability (leaded muntz)
Alpha plus beta brasses
Free cutting brass 61.5Cu-35.5Zn 3Pb has the best
machinability plus good mechanical and corrosion resistance
properties.
Used for automatic high speed screw machine parts
Naval brass:60Cu39.25Zn, 0.75Sn
Also known as TOBIN bronze has increased resistance to salt
water corrosion. Used for condenser plates, welding rods,
propeller shafts, piston rods and valve stems.
Manganese bronze:
58.5Cu-39Zn, 1.4Fe, 1Sn and 0.1Mn
High zinc brass with high strength and wear resistance.
Used for clutch discs, shafts, valve stems, welding rods.
Cupronickels
Copper nickel alloys that contain upto 30%Nickel
Copper nickel phase diagram is of solid solution type.
At all compositions, the cupronickel alloys are single phase in
nature.
Not susceptible to heat treatment and their properties can be
altered only by cold working.
Have high resistance to corrosion fatigue.
High resistance to corrosive and erosive action of rapidly
moving sea water.
Used for Condenser, distiller, evaporator and heat exchanger
tubes. (where evaporation of salts are expected)
Cupronickels-Nickel silver
Alloys of copper, nickel and zinc
Copper
Nickel
Zinc
50-70
5-30
5-40
Addition of nickel to Cu-Zn gives
a pleasing silver -blue-white colour and
good corrosion resistance to food chemicals, water and atmosphere.
Used for rivets, screws, tableware,radio dials, costume jewelry.
Cupronickels-Nickel silver
More than 60 Cu -single phase
Between 50-60 Cu, two phase.
Hence hot workable and have high modulus of elasticity.
Used for
springs and contacts in telephone equipment,
resistance wire,
surgical and dental equipment.
Aluminium
Light weight (density about one third of steel)
Good malleability, formability and corrosion resistance.
High strength to weight ratio than steels.
High electrical and thermal conductivity
Non magnetic,- can be used for electrical shielding purposes
like enclosure for electrical equipment.
Strength is 13,000 psi. can be improved to 100,000 psi by cold
working.
Extensively used cooking utensils, food and beverage cans
and welded assemblies.
Aluminium and copper
Max solubility o copper in aluminium is 5.65% at 1018 deg F
It decreases to 0.45% at 572 deg F
So, alloys containing 2.5 to 5 % copper will respond to heat
treatment by age hardening.
Solution treatment is carried out by heating the alloy to the
singel phase region, followed by rapid cooling.
An intermediate alloy phase(Ѳ - theta) is formed. This is
similar in composition to CuAl2.
Subsequent aging, precipitates the theta phase , thus
increasing the strength of the alloy.
Bearing alloys
A bearing is a device to allow
constrained relative motion between
two parts, typically rotation or linear
movement.
Bearings may be classified broadly
according to the motions they allow
and according to
their principle of operation as well as
by the directions of applied loads
they can handle.
A bearing is a device to allow constrained relative motion
between two parts, typically rotation or linear movement.
Bearings may be classified broadly according to the motions
they allow and according to their principle of operation as well
as by the directions of applied loads they can handle.
ball
Inner surface
Outer surface
Good bearing needs....
The general attributes of a good bearing material are:
· A low coefficient of friction versus hard shaft materials,
· The ability to absorb and discard small contaminant particles
(embedibility),
· High compressive strength,
· High fatigue strength,
· Corrosion resistance,
· Reasonable cost and ready availability.
Bearing alloys
Lead base alloys known as Babbits
Used for bearings
SAE13
SAE14
SAE13
Pb85, Sb10, Sn5
Pb75, Sb15, Sn10
Pb83, Sb15, Sn1 Arsenic 1
The microstructure consists of
cubes of antimony -tin compound
in a binary eutectic mixture of
lead and tin solid solutions.
Bearing alloys
Used for automotive connecting rods,
camshaft bearings,
diesel engine bearings,
car and rail bearings,
electrical motor bearings.
Lead is heavy, soft and malleable.
Antimony raises the recrystallisation temperature and
improves strength and hardness.
Tin improves hardness and strength and also decreases the
eutectic temperature.
Babbit metal
Babbitt metal, also called white metal, is an alloy used to provide the bearing
surface in a plain bearing. Babbitt metal is characterized by its resistance to
galling.
Common compositions for Babbitt alloys:
 90% tin 10% copper
 89% tin 7% antimony 4% copper
 80% lead 15% antimony 5% tin
Originally used as a cast in place bulk bearing material, it is now more
commonly used as a thin surface layer in a complex, multi metal structure.
Babbit metal
Babbitt metal is soft and easily damaged, and seems at first sight an unlikely
candidate for abearing surface, but this appearance is deceptive.
The structure of the alloy is made up of small hard crystals dispersed in a matrix
of softer alloy.
As the bearing wears, the harder crystal is exposed,
with the matrix eroding somewhat to provide a path
for the lubricant between the high spots
that provide the actual bearing surface.
The Basics
Bearings reduce friction by providing smooth metal balls or rollers, and a
smooth inner and outer metal surface for the balls to roll against. These
balls or rollers "bear" the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple:
Things roll better than they slide. That is because when things slide, the
friction between them causes a force that tends to slow them down. But if
the two surfaces can roll over each other, the friction is greatly reduced.
The wheels on your car are like big bearings. If you had something like
skis instead of wheels, your car would be a lot more difficult to push
down the road.
Effect of tin andTin
zinc
Bronzes
Tin's principal function in these bronzes is to strengthen the alloys.
Zinc also adds strength, but more than about 4% zinc reduces the antifrictional
properties of the bearings alloy.
The tin bronzes are strong and hard and have very high ductility.
This combination of properties gives them a
high load-carrying capacity,
good wear resistance and
the ability to withstand pounding.
The alloys are noted for their corrosion resistance in seawater and brines.
Tin Bronzes
Tin Bronzes
The tin bronzes' hardness inhibits them from conforming easily to rough or
misaligned shafts.
Similarly, they do not embed dirt particles well and therefore must be used with
clean, reliable lubrication systems.
They require a shaft hardness between 300-400 BHN.
Tin bronzes operate better with grease lubrication than other bronzes; they are
also well suited to boundary-film operation because of their ability to form polar
compounds with small traces of lubricant.
Differences in mechanical properties among the tin bronzes are not great. Some
contain zinc as a strengthener in partial replacement for more-expensive tin.
Leaded Tin Bronze
Leaded Tin Bronzes
Some tin bronzes contain small amounts of lead.
In this group of alloys, lead's main function is to improve machinability.
It is not present in sufficient concentration to change the alloys' bearing
properties appreciably .
A few of the leaded bronzes also contain zinc, which strengthens the alloys at a
lower cost than tin.
The leaded bronzes in this family otherwise have similar properties and
application as the tin bronzes.
High Leaded Tin Bronze
High-Leaded Tin Bronzes
The family of high-leaded tin bronzes include the workhorses of the bearing
bronze alloys. Alloy C93200 has a wider range of applicability, and is more often
specified, than all other bearing materials. It, and the other high-leaded tin
bronzes are used for general utility applications under medium loads and
speeds, i.e., those conditions which constitute the bulk of bearing uses.
Strengths and hardnesses are somewhat lower than those of the tin bronzes
but this group of leaded alloys excel in their antifriction and machining
properties.
High strength is sacrificed for superior lubricity in the bronzes containing 15 and
25 percent lead, Alloys C93800 and C94300.
These high-leaded tin bronzes embed dirt particles very well and conform easily
to irregularities in shaft surfaces and permit use with unhardened shafts. As in all
leaded bronzes the lead is present as discrete microscopic particles
Aluminium Bronze
Aluminum Bronzes
The aluminum bronzes are the strongest and most complex of the copper-based
bearing alloys.
Their aluminum content provides most of their high strength and makes them the
only bearing bronzes capable of being heat treated.
Their high strength, up to 68,000 psi yield and 120,000 tensile, permits them to
be used at unit loads up to 50 percent higher than those for leaded tin bronze.
Because of their high strength, however, they have fairly low ductility and do not
conform or embed well.
They consequently require shafts hardened to 550-600 BHN.
Surfaces must also be extremely smooth, with both shaft and bearing finished to
1520 in RMS.
Aluminium Bronze
Aluminum Bronzes
Careful attention should be given to lubricant cleanliness and reliability, the latter
because these alloys do not have the anti-seizing properties typical of the
leaded and tin bearing bronzes.
On the other hand, the aluminum bronzes have excellent corrosion resistance
and are ideally suited for such applications as marine propellers and pump
impellers.
The aluminum bronzes also have superior elevated temperature strength. They
are the only bronzes - and the only conventional bearing material able to operate
at temperatures exceeding 50OF.
Manganese Bronze
Manganese Bronzes: Alloy Nos. C86300, C86400
Manganese bronzes are modifications of the Muntz metal-type alloys (60%
copper 40% zinc brasses) containing
small additions of manganese, iron and aluminum,
plus lead for lubricity, anti-seizing and embeddibility.
Like the aluminum bronzes, they combine very high strength with excellent
corrosion resistance.
Manganese bronze bearings can operate at high speeds under heavy loads,
but require high shaft hardnesses and nonabrasive operating conditions.
Summary
Summary
Bearing bronzes offer
broad ranges of strength, ductility,
hardness, wear resistance,
anti-seizing properties, low friction and
the ability to conform to irregularities,
tolerate dirty operating environments and contaminated lubricants.
The corrosion resistance of bearing bronzes is generally superior to
other bearing materials, and can be selected to meet particular ambient
conditions.
Summary
Summary
Bronzes permit easy and economical manufacture, allowing bearings to
be made in special and one-of-a-kind configurations simply and at low
cost.
No bearing metals have better machinability than the leaded and highleaded bearing bronzes.
Almost without exception, a bearing bronze can be selected to satisfy
any bearing application that exists.
More info from :Copper Development Association Inc
copper.org