Lead Base Alloys
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| Lead Alloys |
Because lead
is very soft and ductile, it is normally used Commercially as lead alloys.
Antimony, tin, arsenic, and calcium are the most common alloying elements.
Antimony generally is used to give greater hardness and strength, as in storage
battery grids, sheet, pipe, and castings. Antimony contents of lead-antimony
alloys can range from 0.5 to 25%, but they are usually 2 to 5%.
Lead-calcium
alloys have replaced lead-antimony alloys in a number of applications, in
particular, storage battery grids and casting applications. These alloys
contain 0.03 to 0.15% Ca. More recently, aluminum has been added to
calcium-lead and calcium-tin-lead alloys as a stabilizer for calcium. Adding
tin to lead or lead alloys increases hardness and strength, but lead-tin alloys
are more commonly used for their good melting, casting, and wetting properties,
as in type metals and solders. Tin gives the alloy the ability to wet and bond
with metals such as steel and copper; unalloyed lead has poor wetting
characteristics. Tin combined with lead and bismuth or cadmium forms the
principal ingredient of many low-melting alloys.
Arsenical
lead (UNS L50310) is used for cable sheathing. Arsenic is often used to harden
lead-antimony alloys and is essential to the production of round dropped shot.
Applications
The most
significant applications of lead and lead alloys are lead-acid storage
batteries (in the grid plates, posts, and connector straps), ammunition, cable
sheathing, and building construction materials (such as sheet, pipe, solder,
and wool for caulking). Other important applications include counterweights,
battery clamps and other cast products such as: bearings, ballast, gaskets,
type metal, terneplate, and foil. Lead in various forms and combinations is
finding increased application as a material for controlling sound and
mechanical vibrations. Also, in many forms it is important as shielding against
x-rays and, in the nuclear industry, gamma rays. In addition, lead is used as
an alloying element in steel and in copper alloys to improve machinability and
other characteristics, and it is used in fusible (low-melting) alloys for fire
sprinkler systems.
Battery Grids. The largest use of lead is in the
manufacture of lead-acid storage batteries. These batteries consist of a series
of grid plates made from either cast or wrought calcium lead or antimonial lead
that is pasted with a mixture of lead oxides and immersed in sulfuric acid.
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| Battery Grids |
Type metals, a class of metals used in the
printing industry, generally consist of lead-antimony and tin alloys. Small
amounts of copper are added to increase hardness for some applications.
Cable Sheathing. Lead sheathing extruded around
electrical power and communication cables gives the most durable protection
against moisture and corrosion damage, and provides mechanical protection of
the insulation. Chemical lead, 1% antimonial lead, and arsenical lead are most
commonly employed for this purpose.
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| Lead Cable Sheath |
Sheet. Lead sheet is a construction
material of major importance in chemical and related industries because lead
resists attack by a wide range of chemicals. Lead sheet is also used in
building construction for roofing and flashing, shower pans, flooring, x-ray
and gamma-ray protection, and vibration damping and soundproofing. Sheet for
use in chemical industries and building construction is made from either pure
lead or 6% antimonial lead. Calcium-lead and calcium-lead-tin alloys are also
suitable for many of these applications.
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| Lead Sheet |
Pipe. Seamless pipe made from lead and
lead alloys is readily fabricated by extrusion. Because of its corrosion
resistance and flexibility, lead pipes finds many uses in the chemical industry
and in plumbing and water distribution system. Pipe for these applications is
made from either chemical lead or 6% antimonial lead.
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| Lead Pipe |
Solders in the tin-lead system are the most
widely used of all joining materials. The low melting range of tin-lead solders
makes them ideal for joining most metals by convenient heating methods with
little or no damage to heat-sensitive parts. Tin-lead solder alloys can be
obtained with melting temperatures as low as 182 °C and as high as 315 °C.
Except for the pure metals and the eutectic solder with 63% Sn and 37% Pb, all
tin-lead solder alloys melt within a temperature range that varies according to
the alloy composition.
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| Solders |
Lead-base bearing alloys, which are called lead-base babbitt
metals, vary widely in composition but can be categorized into two groups:
- Alloys of lead, tin, antimony, and, in many instances, arsenic
- Alloys of lead, calcium, tin, and one or more of the alkaline earth metals
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| Lead-Base Bearing Alloys |
Ammunition. Large quantities of lead are used
in ammunition for both military and sporting purposes. Alloys used for shot
contain up to 8% Sb and 2% As; those used for bullet cores contain up to 2% Sb.
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| Ammunition |
Terne Coatings. Long terne steel sheet is carbon
steel sheet that has been continuously coated by various hot dip processes with
terne metal (lead with 3 to 15% Sn). Its excellent solderability and special
corrosion resistance make the product well-suited for this application.
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| Trene Coating |
Lead foil, generally known as composition
metal foil, is usually made by rolling a sandwich of lead between two sheets of
tin, producing a tight union of the metals.
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| Lead Foil |
Fusible Alloys. Lead alloyed with tin, bismuth,
cadmium, indium, or other elements, either alone or in combination, forms
alloys with particularly low melting points. Some of these alloys, which melt
at temperatures even lower than the boiling point of water, are referred to as
fusible alloys.
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| Fusible Alloys |
Anodes made of lead alloys are used in the
electrowinning and plating of metals such as manganese, copper, nickel, and
zinc. Rolled lead-calcium-tin and lead-silver alloys are the preferred anode
materials in these applications, because of their high resistance to corrosion
in the sulfuric acid used in electrolytic solutions. Lead anodes also have high
resistance to corrosion by seawater, making them economical to use in systems
for the cathodic protection of ships and offshore rigs.
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| Anodes |
Below is
listed the Unified Numbering System (UNS) designations for various pure lead
grades and lead-base alloys.
Pure leads
L50000 - L50099
Lead -
silver alloys L50100 - L50199
Lead -
arsenic alloys L50300 - L50399
Lead -
barium alloys L50500 - L50599
Lead -
calcium alloys L50700 - L50899
Lead -
cadmium alloys L50900 - L50999
Lead -
copper alloys L51100 - L51199
Lead -
indium alloys L51500 - L51599
Lead -
lithium alloys L51700 - L51799
Lead -
antimony alloys L52500 - L53799
Lead - tin
alloys L54000 - L55099
Lead -
strontium alloys L55200 - L55299
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