WL 112 Ch20 ch20 presentation

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Metallurgy
Fundamentals
Ferrous and Nonferrous

High-Density Metals: Zinc,
Tin, Lead, Mercury, and
Uranium
Chapter 20

Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website.
• Identify the properties and commercial applications of zinc, tin, lead,
mercury, and depleted uranium.
• Describe how the die casting process is used to produce parts from zinc.
• Explain why a tin-lead solder is used to make printed circuit boards and
other electronic assemblies.
• Understand why printed circuit board production requires a much greater
percentage of successful solder joints than heat-treated steel hydraulic
shafts, even though both specify precision dimensions.
Learning Objectives

• List the properties and current applications of lead and mercury.
• Explain why fewer applications for lead and mercury exist today
than in the recent past.
• State the primary precautions workers involved with lead and
mercury should take in their daily activities.
• Explain how the properties of depleted uranium are potentially
harmful if it is not handled correctly.
Learning Objectives

• This chapter describes four
heavy metal elements.
• Zinc, tin, lead, and mercury
Introduction: Heavy Metals
Goodheart-Willcox Publisher

• Zinc comes from ore and recycled zinc products.
• Zinc sulfide ore (zinc blende) is mostly from underground mines.
• Ore is crushed and separated from gangue by floatation.
• Roasting above 1650°F (900°C) forms zinc oxide and sulfur dioxide.
• Zinc oxide can be reduced to metal by roasting with coke.
• Zinc vapor in furnace exhaust is captured and condensed to solid zinc.
• Sulfur dioxide by-product is converted to sulfuric acid.
• This is sold or used in a second method of zinc extraction.
Zinc Production

• Most zinc produced by roasting coke contains some lead.
• Second method of extraction leaches zinc from ore using sulfuric
acid.
• Forms zinc compound that is reduced to metal in an electrolytic cell
• This zinc contains less than 0.0001% lead.
• Zinc produced this way is in greater demand as manufacturers seek
to reduce lead in our environment.
Producing Zinc with Less Lead

• When galvanized steel scrap is charged to an electric arc furnace
(EAF), zinc vaporizes.
• This is captured in furnace exhausts.
• About 30% of all primary zinc in US is obtained from recycled zinc
parts and EAF dust.
Zinc from Scrap

• Zinc can be recycled indefinitely without loss of properties.
• Inhalation of zinc fumes is dangerous.
• Touching or handling zinc parts or galvanized sheet poses no
significant hazard.
Zinc
Sustainable Metallurgy

• Zinc resists creep at ambient temperatures because it has a
hexagonal close-packed crystal structure.
• Zinc parts under constant load retain their shape.
• Better than other low-melting-point metals and plastic parts.
• Zinc alloys have been developed for better creep resistance.
• They find applications with temperatures as high as 248°F (120°C).
• UNS Z35637 (ZA-8) is an example.
Zinc Key Properties: Creep Resistance

• Most zinc alloys have relatively narrow freezing range.
• Zinc casting alloys are more fluid than alloys with wider freezing
range.
• Dendrites formed during solidification are shorter and smaller than
with other alloys.
• High fluidity means liquid metal fills small channels in castings
better.
Zinc Key Properties: High Fluidity for
Casting

• Zinc can be rolled or forged.
• It has a hexagonal close-packed (hcp) crystal structure.
• This means working at room temperature without cracking is difficult.
• Rolling and forging are usually done at hot-work temperatures.
Forming Solid Zinc

• The major method for producing zinc items is die casting.
• Die casting in steel dies solidifies liquid rapidly.
• Dendrite spacing and grain size much smaller than in sand castings.
• Properties of finished parts are more uniform across part.
• Higher impact and tensile strength
• Common zinc die casting alloys contain about 4% aluminum.
• Tight controls are kept on other elements.
Zinc Applications—Die Casting

• Zinc die casting alloys melt over a narrow temperature range.
• Zinc alloy 3 (also called UNS Z33520, ASTM AG40A, and Zamak 3)
• Melts between 718°F and 729°F (381°C and 387°C)
• Low melting temperature means dies erode more slowly than with Mg.
• Protective cover gases and fluxes are not needed for zinc.
• Zinc alloys can flow into channels less than 0.040″ (1 mm) thick.
• Microscopic shrinkage cavities do not develop during freezing.
Die Cast Zinc Alloy 3

• Zinc is die cast with cold-chamber and hot-
chamber processes.
• Cold-chamber injection molding equipment is
less expensive and requires less maintenance.
• Hot-chamber die casting has several
advantages.
• Very consistent liquid metal temperature
• Closely controlled amount of metal with each
plunger stroke
• No oxide skin mixed with injected metal
Hot- vs. Cold-Chamber Zinc Die Casting
Chicago White Metal Casting, Inc.

• Hot-chamber die casting can make precise, consistent parts.
• Melt temperature, die temperature, die temperature distribution, and
injection rate and pressure must be controlled.
• Parts can be made with tolerances of ±0.001″.
• Very complex shapes can be cast.
Hot-Chamber Die Casting Zinc

• Heat sink for LED light bulb fixture is an application of hot-chamber
die casting.
• Webs and channels are designed for optimum heat transfer.
• Each part must be dimensionally consistent.
Heat Sink for LED Light Bulb
Audrius Merfeldas/Shutterstock.com

• Small line is visible in parts where die halves met.
• Dies are usually designed so parting line ridge may be left on parts.
• High ram force or low clamping force pushes liquid metal out
between die halves.
• Forms thin flash of excess metal
• Flash must be removed
• By a punch designed for each part, manual grinding, or tumbling parts
in very hot air
Parting Lines and Flash

• Zinc has been displaced by engineered plastics for many
automotive applications.
• Plastic is lighter but cannot be used at elevated temperatures.
• Zinc is still preferred for complex shapes under load above 150°F
(66°C) or for long times.
• Zinc die cast alloys, such as zinc alloy 3 (UNS Z33520), will not creep
for periods of weeks.
• Engine components such as carburetors are an example of this.
Zinc or Plastic?

• Automation makes it easier to maintain desired conditions but does
not always monitor all required factors.
• Opening a shop window changes temperature profile in dies.
• Liquid metal dissolves gases from air, so porosity can increase.
• Large amounts of remelt from gates and runners can add impurities.
• Different alloys must be kept separate.
• Process technicians and operators must control conditions.
Process Control of Die Casting

• Zinc offers best corrosion protection of all sacrificial coatings for
steels.
• Zinc is a very electronegative metal.
• Zinc will corrode before steel.
• Corrosion protection is done two ways.
• Zinc bars can be bolted to structures.
• Zinc can cover entire steel component.
Zinc Applications for Corrosion
Protection

• Zinc blocks attached to ship hull corrode
before steel hull.
• Some oil and gas pipes are protected this
way.
• Blocks of zinc are connected to pipe by a
steel cable, then buried a few feet away.
• Zinc galvanic protection is preferred at a
pipeline collection site (where many pipes
and valves meet).
Zinc Sacrificial Corrosion
Dennis Dronin/Shutterstock.com

• Protective zinc can be applied using several methods.
• Hot-dip galvanizing
• Electroplating
• Molten metal spray
• Mechanical plating with zinc powder
• Hot-dip galvanizing is most common method.
• Steel strip is passed through a bath of molten zinc at speeds up to
600 feet per minute (3 m/s).
Galvanizing Steel

• Steel strip reacts with zinc, creating a
thin layer of zinc metallurgically bonded
to steel.
• This sheet can be stamped and formed
into parts without losing its galvanized
layer.
• Individual parts can be cleaned and
dipped into liquid zinc.
Hot-Dip Galvanizing
American Galvanizers Association

• Large zinc crystals form on steel’s surface.
• Differences in crystallographic orientation reflect light
differently.
• Grains stand out in a phenomenon called spangle.
• Different grain sizes (grades of spangle) have
slightly different formability and corrosion protection.
• Customers specify desired grade in purchase
orders.
Spangle
Jay Warner

• Electroplating uses electrolysis to deposit a thin
layer of metal onto another substance for
corrosion resistance.
• Small parts (bolts and screws) are zinc
electroplated.
• Electroplating keeps zinc coating uniformly thin.
• Parts are usually given a chromate conversion
coating as well.
• This imparts a shine to the finish.
• The zinc does not oxidize and dull for some time.
Zinc Electroplating

• Plating requires multiple baths.
• Cleaning, preparation, plating, additional coatings, rinsing and drying
• Short parts are tumbled in a drum while solutions are pumped in
and out.
• Larger parts are hung on rack-type frames and dipped sequentially
into solution tanks.
• Production plating of large parts uses programmable controller.
• Technicians must be alert to needed adjustments.
Electroplating Process Control

• Pure tin is soft, white metal resistant to corrosion in typical moist-air
conditions.
• Most tin metal is used for tin solders.
• A significant amount is used for tin plating steel.
• Some is alloyed with copper, lead, or silver.
Tin

• Tin metal is extracted from the mineral ore cassiterite (tin oxide).
• This is smelted and electrolytically refined into ingots.
• Most tin comes from Asia.
• About 15% of tin is recycled, mostly from printed circuit boards.
Sources of Tin

• Current tin mines may play out within 50 years.
• Tin from recycling will increase, especially if price of mined tin rises.
• Illegal tin mining is common, where mine owners skirt safety regulations,
environmental precautions, and taxes.
• Some electronics manufacturers are working to avoid illegally mined tin.
• Electronic Industry Citizenship Coalition (EICC) seeks to help electronics
firms develop more stable supply chains.
• Free of conflict minerals and questionable practices
Tin

• Strength is not important for most applications using tin alloys.
Properties of Tin

• For some products, creep strength and crack growth resistance are
desirable.
• Large microchips, encapsulated integrated circuits, installations
subject to vibration
• Neither cold work nor heat treatment can strengthen tin alloys.
• Tin’s melting point, 450°F (232°C), is too low.
Properties of Tin (cont.)

• Solder alloys are designed to melt below 400°F (204°C).
• Must metallurgically bond with base metal but not melt it
• Form layer(s) of intermetallic compounds between tin and base metal
• For circuit boards, solder must melt at lowest temperature possible.
• Avoids damaging electronic components
• Is completely solid at temperatures below 200°F (93°C)
• Metallurgically bonds to copper tracks and component leads
Applications: Tin Solders

• Alloy of 60% tin and 40% lead—also called eutectic solder
• Minimum melting point is 361°F (183°C).
• Bonds easily to copper using noncorrosive flux
• Lead-free solder became more desirable for health reasons.
• SAC solders were developed (SnAgCu—tin, silver, and copper).
• SAC 305 has 96.5% tin, 3% silver, and 0.5% copper.
• Melts at 423°F (217°C), much higher than lead-bearing solder
• Improvements in computer chips helped make it workable.
Electrical Solder

• Modern electronics is based on small integrated circuits (ICs) called
microchips, or simply chips.
• Encapsulated in black plastic, with copper leads extending out
• Copper leads connect to electronic circuits.
• Information (electrical signals) pass through leads into chips.
Integrated Circuits (Chips)
Warner Consulting, Inc.

• Printed circuit boards (PCBs) connect chips to device.
• PCBs have copper tracks with tin-plated copper pads for connections.
Printed Circuit Boards
Anatoliy Sadovskiy/Shutterstock.com

• Soldering connects chip leads and PCB tracks.
• Electrically and metallurgically bonded
• Smallest spacing between leads to miniaturize devices
• With excess solder, unintended connections (shorts) may occur.
• With insufficient flux or solder, open (failed) connections may occur.
Soldering Printed Circuit Boards

• IC chips degrade and fail if exposed to solder temperatures too
long.
• Solder melting temperature must be as low as possible.
• Main reason for using 40% lead solders in past
• Low-lead solders under development melt at higher temperatures.
• Special chips and procedures must be used.
Importance of Keeping Temperatures
Low

• Two methods used to solder PCBs
• Wave soldering and reflow soldering
• Wave soldering uses flowing liquid solder.
• PCB passes over and just touches flowing
solder.
• Surface tension pulls liquid metal into joint
areas.
• All circuit board connections are soldered
quickly.
Soldering Assembled PCBs
SEHO Systems GmbH

• Process uses solder made into paste of
powder and flux.
• Small droplets of paste are placed on copper
pads on PCBs.
• PCBs pass through reflow soldering oven to
make solder connections.
• Small components require precise amount
and placement of paste.
Reflow Soldering PCBs
Audrius Merfeldas/Shutterstock.com; Dmitry Morgan/Shutterstock.com

• In the 1950s and 1960s, one flaw per 1000 parts (1000 flawed solder
joints per one million) was acceptable quality.
• A circuit board with 1000 solder joints would yield zero successful boards.
• In 1980s, Motorola developed Six Sigma to ensure excellence.
• Goal to achieve less than 3.4 defects per one million products (or 3.4 flawed
joints per one million joints made)
• Producing a 1000-joint PCB yields about 996 successful boards for every
1000.
The Critical Need for Joint Quality in PCBs (Part 1)
Practical Metallurgy

• Six Sigma requires constant effort from technicians and operators.
• Temperature controllers must be calibrated frequently.
• Process speed, fluxes, and solders must be carefully maintained.
• Poorly packaged IC chips may change amount of oxide on leads.
• Any process changes must be measured and documented carefully.
• Helps assure changes reduce number of flawed PCBs.
• Alert technicians and operators are most likely to observe changes.
• They are essential to problem-solving aspects of Six Sigma projects.
The Critical Need for Joint Quality in PCBs (Part 2)
Practical Metallurgy

• Tin is most commonly electroplated onto steel to produce tinplate.
• Tin-coated steel resists corrosion and remains shiny in indoor
atmospheres.
• If tinplate is gouged, exposed steel may discolor and rust.
• Tin-plated steel is used to manufacture cans for paint and other
products.
Tinplate

• In the past, all steel cans for food were tin plated and called “tin
cans.”
• Today, polymer coatings are used on many tin-plated steel food
containers.
• Allows a thinner layer of tin.
• Tin electroplating is used on copper leads of electronic components.
• Prevents corrosion before soldering and promotes reliable solder
joints.
Tinplate (cont.)

• Tin is alloyed with copper to make tin bronze.
• Tin bronze is preferred for cast artwork.
• Its high fluidity allows it to take on fine detail in molds.
Tin as an Alloy Addition

• Lead once had many common applications.
• Water pipes, pipe solder, shot for firearms, lead oxide for white paint
• Today, hazards of lead are better understood.
• Ingested lead reduces cognition and brain functioning.
• Lead causes permanent brain damage, especially in growing children.
• Today, most applications have found alternative material.
• Some applications still require properties only lead provides.
Lead

• In 1970s, awareness grew of lead’s damaging effect on people.
• By early 2000s, European Union released its Restriction of
Hazardous Substances (RoHS) directives.
• Effectively eliminated four metals from products and production: lead,
mercury, cadmium, and hexavalent chromium
• Soldered electronic devices are still allowed to use lead.
Reduction of Lead in the Environment

• OSHA and EPA requirements in US are reducing lead exposure.
• Lead paint chips and lead in water from service lines and pipe
fittings have been a hazard, such as in Flint, Michigan.
• There is no safe minimum threshold for lead exposure, and anyone
who works with lead must be checked regularly.
• Lead refinery
• Lead battery manufacturer
• Radiator repair shop
Reduction of Lead in the Environment
(cont.)

• Lead shot for hunting waterfowl can contaminate and poison birds.
• Birds eat lead pellets, and lead contamination moves up food chain.
• Lead concentration increases at each step up on food chain.
• This is called bioaccumulation.
• At Nahunt Marsh, Iowa, birds were dying of lead poisoning before EPA
began remediation in 1999.
• Lead shotgun pellets banned in 1991 in US for waterfowl hunting.
• Copper-coated steel pellets is one solution to reduce lead contamination.
Lead Contamination in Nahunt Marsh, Iowa

• Lead is obtained from mining and from scrap.
• Galena is lead ore, a crystalline form of lead
sulfide.
• It is smelted to produce lead.
• Sulfur dioxide gas is a byproduct converted to
sulfuric acid and sold.
• China and Australia produce most primary lead.
• Today, all lead produced in US comes from
recycled scrap.
Sources of Lead
Lukasz Stefanski/Shutterstock.com

• Lead can be cast, rolled, extruded, bent, and crimped.
• Lead will creep near room temperature under very low loads.
• Its melting point is 621.43°F (327.46°C).
• Lead is near hot-work temperatures at 75°F (24°C).
Processing Lead

• Ninety percent of lead produced in US is for lead-acid batteries.
• For battery plate, lead is cast into plate form directly from melt.
• Calcium metal may be alloyed with lead.
• This forms large CaPb3 particles in lead plates during casting.
• CaPb3 particles increase resistance to recrystallization and creep,
even at temperatures as high as 3/4 of absolute melting point.
Applications for Lead: Batteries

• Lead absorbs ionizing radiation very well.
• High-energy gamma, beta particle, and
neutron radiation
• Lead is effective as radiation shielding.
• Dental patients wear lead aprons while
X-ray machines are on.
• Lead aprons shield medical personnel
from X-rays.
Applications for Lead: Radiation
Shielding
CWA Studios/Shutterstock.com

• Lead is used for keels in sailboats because of its high density.
• This helps stabilize boats with a small volume.
• Less volume creates less drag as it passes through water.
Applications for Lead: Sailboat Keels
MattJackson/Shutterstock.com

• Lead is alloyed in brass and steel to improve machinability.
• Brass with 1% to 4% lead is called free-machining, or leaded, brass.
• During machining, metal chips come off in short pieces that fall
aside easily.
• Without lead, chips can form long, curled lengths of rough-edged
metal.
• This complicates machining and can be dangerous to handle.
Lead as an Alloy Addition

• In the past, lead alloys were used for many applications.
• Hot metal typesetting, water pipes, flashing around roof vents
• Tetraethyl lead in gasoline reduced engine knocking.
• Lead compounds were used in pesticides and for pigments.
• Traditional red color used for barns came from low-cost lead paint.
• Tin-lead solder alloys (50% lead) used to solder copper water pipes
• Today, these applications have been discontinued.
No-Longer-Used Applications

• Lead-free solders are now required in most applications.
• Municipal water operations use chemicals to reduce amount of dissolved lead from
pipes.
• But tests seem to show many water lines deliver more lead than is healthy.
• Exposure to lead can occur through inhalation, ingestion, and skin contact.
• Lead paint peels and turns into dust—major source of lead exposure for children.
• Bulk metallic lead is not hazardous, provided users wash thoroughly.
• Inhalation is especially a concern for workers in lead-related occupations.
• Be sure to follow safety data sheet (SDS) guidelines.
Health and Safety with Lead Exposure
Safety Note

• Mercury is an extremely dense, silvery-white
metal.
• Mercury is the only metal that is liquid at room
temperature.
• Freezing point is –37.89°F (–38.83°C).
• Lowest melting point of all pure metals
Mercury
MarcelClemens/Shutterstock.com

• Most common ore of mercury is cinnabar (HgS).
• Mercury extracted by heating cinnabar in air and condensing vapor.
• China produces most mercury (2/3 of global production).
• Mercury is also recovered from copper electrolysis and other metal
smelting operations.
• All mercury produced in US comes from recycled sources.
• Impure mercury is distilled by heating, and the mercury vapor is
condensed.
Sources of Mercury

• Mercury can cause chronic and acute poisoning.
• Both mining and recycling mercury are hazardous operations.
• Abandoned mercury mines and refining sites contain mercury
waste.
• Water runoff from these is a source of environmental damage.
• Downstream fish are usually too contaminated to be eaten.
• Often, no companies or individuals remain to clean up sites.
Toxicity of Mercury

• About half of mercury emissions come from natural volcanic action.
• About 5% of mercury emissions come from gold production.
• People living and working near gold mines have greatest exposure.
• About 4% of emissions are from nonferrous smelter operations.
• In US, about 20% of mercury in air is from coal-fired power plants.
• Mercury is a trace element in coal and vaporizes when coal is burned.
• Mercury stack emissions are absorbed in water and concentrated in
fish.
Sources of Mercury Emissions

• Mercury is clearly an occupational hazard in workplaces.
• Industrial and commercial uses of mercury are regulated in many
countries.
• In US, occupational exposure limits are set by OSHA.
• Environmental releases and disposal of mercury are regulated by
Environmental Protection Agency (EPA).
Occupational Exposure to Mercury

• Mercury and most of its compounds must be handled with care.
• Mercury can be absorbed through skin.
• Mercury vapor can be inhaled.
• Containers of mercury must be sealed to avoid evaporation.
• Any heating of mercury must be done with proper ventilation.
• In lab or workshop, metallic mercury may sit in floor drain traps.
• This will slowly vaporize and can cause long-term, low-level exposure.
• If spills occur, use SDS cleaning procedures to avoid exposure.
Safe Handling of Mercury
Safety Note

• US has been phasing out applications of
mercury since 1990.
• RoHS directive effectively bans use,
production, and import of mercury-bearing
products in EU countries.
• Today, mercury is used primarily for
fluorescent lamps.
• Mercury is also used to manufacture
industrial chemicals.
Applications for Mercury
Bokhach/Shutterstock.com

• Despite mercury content, CFL lamps are so efficient there is a net
reduction in mercury released.
• Coal contains small amount of mercury that escapes when it is
burned.
• CFLs reduce amount of coal used to make electricity.
• Each CFL contains about 4 mg of mercury.
• Much less than amount used for standard long-tube fluorescent bulbs.
CFLs and LEDs (Part 1)

• Breaking CFL bulbs should be avoided.
• Old bulbs should be recycled at places prepared for them.
• As costs drop, LEDs will likely replace CFLs, further reducing
amount of mercury in environment.
CFLs and LEDs (Part 2)

• Spark-free electrical switches are needed at oil fields and platforms.
• No-spark mercury switches are made by sealing mercury inside a
glass ampule with two electrical contact wires.
Sealed Mercury Switches
dcwcreations/Shutterstock.com

• Tilting/rotating ampule opens or closes circuit.
• Any spark is contained inside.
• Mercury tilt switches were used in automobiles prior to 2000.
• EPA requires safe removal of switches from scrap automobiles.
Sealed Mercury Switches (cont.)

• Mercury dissolves many other metals to form amalgams.
• Gold and silver are examples.
• An amalgam is an alloy of mercury and another metal.
• Today, mercury amalgam is used for some dental fillings.
• Only for certain teeth in adults
• Amalgams expand slightly as they set.
• This assures a tight fit.
Mercury Amalgams

• Adding mercury to sluice box for gold and silver mining increases
recovery.
• Mercury forms gold or silver amalgam with fine particles of these metals.
• Amalgam sinks to bottom better than fine gold or silver particles alone.
• Mercury is removed by heating, leaving gold or silver behind.
• Over two centuries of mining have left mercury behind in US.
• About 50,000 tons never recovered in California alone
• Potentially creating environmental issues in abandoned mine sites
Mercury Aids Recovery of Gold

• Many applications using mercury (Hg) have disappeared.
• Old thermometers, manometers, and home thermostats
• Mercury batteries were common during twentieth century.
• These were banned in most countries in 1990s.
• Before 2009, flat-screen displays often contained mercury.
• Two very old applications long gone:
• Felt production for hats (Alice in Wonderland’s Mad Hatter)
• Mirrors coated with mercury-tin amalgam
No-Longer-Used Applications of Mercury

• Uranium ore contains two isotopes, U-238 and U-235.
• The “238” and “235” represent atomic weights of each isotope.
• U-235 is used for nuclear reactors and atomic bombs.
• After U-235 removed, remaining material is depleted uranium
• Density of DU is 19.1 g/cm3, 68% greater than lead.
• DU is slightly radioactive but easily shielded.
• Metallic uranium applications use machined castings to develop
desired shapes.
Depleted Uranium (DU)

• Uranium ore is mined in US Southwest.
• Metal in ore contains U-238, 0.7% U-235, and trace of U-234.
• Ore is converted to oxide, then reduced to metal by reaction with a
more reactive element.
• The metal is then reacted to form uranium hexafluoride (UF6).
• U-235 is separated from U-238 to make reactor fuel or weaponry.
• U-238 compound is reduced to solid depleted uranium.
• Depleted uranium has 60% of ore’s as-mined radioactivity.
US Source of Depleted Uranium

• Uranium has a complex series of crystal structures that vary with
temperature and alloying.
• Bulk deformation is difficult, so machining castings is preferred.
• Depleted uranium is alloyed with small amounts of titanium or
molybdenum for added strength.
Processing Depleted Uranium

• Uranium is highly reactive, like magnesium and beryllium.
• Grinding and cutting must be done with care.
• Hot metal fines will burn on contact with water.
• No water can be used to cool workpieces or cutting tools during
processing.
• Metal fines must be collected and disposed of as radioactive
material.
Processing Depleted Uranium (cont.)

• Every worker must absolutely avoid breathing any dust from
uranium grinding and cutting operations.
• If any uranium-bearing dust is ingested, radiation will be totally
absorbed.
• In addition, uranium is chemically toxic, just like lead.
Uranium
Safety Note

• Many applications for depleted uranium (DU) are based on its high
density.
• Radiation shielding
• DU absorbs high-intensity gamma radiation very well.
• DU is often used in industrial radiography cameras.
• Shields are enclosed in plastic foam to prevent direct contact.
• DU is used for helicopter rotor counterweights.
• Passengers and crew are far enough away to avoid radiation.
Applications for Depleted Uranium

• First used during 1991 Gulf War
• High density of DU provides added “punch” to
pierce tank armor.
• Depleted uranium also burns intensely when it
penetrates.
DU Armor-Piercing Shells

• When these weapons are used, DU is scattered around battlefield.
• Forms dust that is inhaled by friend and foe alike
• Embedded metal fragments another way of ingesting DU
• Use of DU bullets spreads low-level radioactive material around area.
• Long-term impact outlasts immediate conflict.
DU Armor-Piercing Shells—Radioactive
Dust

• Hard to justify DU in any application where U-238 dust escapes
• Despite any military advantage, nearby residents and soldiers will ingest
some DU dust.
• Irradiates any person who carries it and is highly toxic to that person
• In addition, U-238 dust spreads, contaminating that area.
• It continues to negatively impact every living thing there for years.
• Ongoing discussion urging countries to ban military use of DU
• No resolution has been adopted by any country with large military.
Depleted Uranium

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