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MFGT 104

Materials and Quality

Ferrous and Non-Ferrous Metals

Professor Joe Greene

CSU, CHICO

MFGT 104

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Ferrous and Non-Ferrous Metals Objectives

List various ingredients of cast iron, steels, and stainless steels

Recognize and use the nomenclature associated with steels

Recognize the major regions and ranges of the iron-carbon phase diagram

List the major shapes in which ferrous metal products are available

List and describe the various alloying elements in ferrous metals and thepurposes of each

Describe the process of galvanic corrosion in metals

Describe the refinement process, major alloys, uses, and properties

copper, brass, bronze,

magnesium, chromium, titanium, lead, tin zinc, gold, and platinum

Explain the refinement process, major alloys, uses, and properties

aluminum and nickel

Describe the uses and properties of major refractory metals

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Introduction

Steelwas used as long ago as 2000 B.C. when charcoal was

packed with iron bars and heated to 1000C.

Steel is not an element, but an iron-carbon alloy that contains

less than 2% carbon.

Cast iron contains between2%

and 4%

carbon. Wrought iron is almost pure iron that includes silicate slag.

The cementation process allowed the carbon in the charcoal to

diffuse into the iron to produce steel in steel bars.

The crucible process improved the quality by steel bars fromcementation were melted together in a large pot and poured

into bars thus yielding a more uniform-quality steel

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Production of Iron

Pure iron is used in limited amounts as iron ingot or ironpowder.

Steels of iron and alloying elements, i.e., carbon, silicon,

nickel, chromium, and manganese, are widely used.

Plain carbon steel(contains less than 1% of alloying element)

carbon, silicon, manganese

Low-alloy steelcontains alloying elements that alter the

properties nickel, chromium, molybdenum

High-alloy steelcontains more than 5% of alloying

elements

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Primary Ores Primary ores that are refined

Magnetite: combination of ferric oxide (Fe2O3) and ferrous oxide

(FeO), black in color and contains 65% iron and highly magnetic

Hematite: contains ferric oxide (Fe2O

3), or rust, is red in color and

contains 50% iron.

Taconite: is green in color and contains 30% iron and much silica.

Other ores that are rarely used due to low grade and yield

Limonite: hydrated ferrous oxide (FeO.H2O)

Siderite: Ferrous carbonate (FeCO3)

Iron pyrites: iron sulfides (FeS) Earliest smelting of iron ore from charcoal (blacksmith)

carbon from wood or coal was mixed with iron ore and placed in

furnace. Air was blown through mixture.

Sponge mass ,bloom, was produced that was hammered to removeimpurities and slag.

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Modern Practice

Modern practice- heats coal in furnace with no air.

Coking oven- furnace in which H2 and other elements are removed

leaving carbon in the form of coke.

Blast furnace- cleaned iron ore is layered with coke and limestone.

Slag is removed with other impurities after the metal is tapped from

the furnace. Limestone is used as a blast furnace slag to removeimpurities as sulfur and silica.

Process

Air is blown at the bottom of the furnace at 1100F so that the carbon in the

coke reacts with the oxygen in the ore and starts to burn of the oxygen from the

iron oxides. The T increases from the reaction to 3000F. After 5 to 6 hours, the iron is tapped from the furnace and poured into ingots

Each ingot (pig) weighs one ton and has 4% carbon as in cast iron.

For other steels, alloying elements are added after remelting.

Production rate of3000 tons of pig iron a day would require

6,000 tons of iron ore and 3,000 tons of coke. 1,500 tons of limestone and 90,000 ft3/min of hot air

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Continuous Process Shapes Steel can be formed into many shapes

hot rolled at 2200 F is used to form shapes

cold rolled (formed after cooling) or cold drawing at roomtemperature is used to finish thin, flat products

Common shapes

Angles with legs of equal (8x8in) or unequal lengths (9x4in)

Bars of solid shape cold or hot drawn from 0.75 to 12 in thick

Beams as in standard I and H beams

Billets with section of ingot suitable for rolling

Blooms as in slabs of steel with equal widths and depths

Channels of a U-shape in cross section

Plates: large flat slabs thicker than 0.25 in

Sheets: large flat slab thinner than 0.25 in

Tubing: square, rectangular and round tubing and pipe

Wires: drawn from bars that have been rolled to small diameters

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Carbon Content in Steels Carbon is the most important alloying element in steel.

Most steels contain less than 1% carbon.

Plain carbon steel- carbon is the only significant alloying

element

M

ild steel, or low carbon steel, are produced in the greatestquantity because it is cheap, soft, ductile, and readily

welded. Caution: it can not be heat-treated

Mild steels are used for car bodies, appliances, bridges,

tanks, and pipe.Name Carbon Content Examples

Low carbon (mild) 0.05% - 0.32% Sheet, structural

Medium carbon 0.35% - 0.55% Machinery

High carbon 0.60% - 1.50% Machine tools

Cast iron >2.00% Castings

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Carbon Content in Steels Medium carbon steel- used for reinforcing bars in

concrete, farm implements, tool gears and shafts, as wellas uses in the automobile and aircraft industries.

High carbon steels - used for knives, files, machine

tooling, hammers, chisels, axes, etc.

A small increase in carbon has significant impact onproperties of the steel. As Carbon increases the steel:

becomes more expensive to produce

becomes less ductile, i.e., more brittle

becomes harder

becomes less machinable

becomes easier to harden and harder to weld

has higher tensile strength has a lower melting point

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Cold Working in Steels

Cold workingis used to enhance the properties of steel

Reducing thickness by 4% raises the tensile strength by 50%

Cold working is plastic deformation at room temperature.

Cold working produces dislocations in the metals structure which

block dislocations as they slide along the slip planes

Products

Cold-rolled sheet steel

Cold drawn tubing

Drawbacks

higher leads are required to size the material as the yield strength increases

work-hardening occurs wherein the material becomes harder

heat treating can reduce the drawbacks

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Other Elements in Steels Alloying elements are added to nullify undesirable elements

Carbon Manganese

increases strength, malleability, hardenability, and hardness

Sulfur reacts with the Mn which reduces the hot short effect of the iron

sulfide accumulating at the grain boundaries and reducing strength at Temp

Aluminum-

reacts with Oxygen versus iron (no sparks). Killed steel

promotes smaller grain size which adds toughness

Silicon- reduces Oxygen negative effects

Boron- increases the hardenability of steel (only with Al added) Copper- increases corrosion resistance

Chromium- increases corrosion resistance and hardenability

Nickel, Niobium, titanium, tungsten carbide, vanadium

increase toughness and strength and impact resistance

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Nomenclature in Steels SAE and AISI developed method of cataloging steel based on

carbon content-%

carbon with implied decimal alloying elements

AISI 8620 steel is the same as SAE 8620 steel

Steels are usually 4 digit designations

1018 steel = 10 is plain carbon steel; 18 represents 0.18%

carbon 4030 steel = 40 is molybdenum steel of .15% to 0.30% Molybdenum and

0.30% carbon

2 - - - = nickel steel with % nickel, 22-- is nickel with 2% nickel

10100 = five digits indicated 1% carbon more

B in the middle of the number, 81B40 indicates min of 0.0005% boron

Various common steels

1010: Steel tuning; 1040: Connecting rods for automobiles

4140: Sockets and socket wrenches;52100: Ball and roller bearings

8620: Shafts, gears, and machinery parts.

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Tool Steels Tool steels are special types of steel produced to make

tooling to cut or shape other materials

Produced by electric furnace Typically, hardened and vary from high carbon to high alloy

Have high wear and heat resistance, high strength, good hardenability

Alloying elements include Chromium (Cr), Cobalt (Co), Copper (Cu),

Manganese (Mn), Molybdenum (Mb), Nickel (Ni), Silicon (Si), Tungsten

(W), and Vanadium (V)

Tool Steel Classification A: Air- Hardening, medium-alloy steel

H: Hot working steels. Forging equipment.

M: High speed steels, containing molybdenum. Lathe tools, drills

O: Oil-hardening, low alloy steels

S: Shock-resisting, medium-carbon, low-alloy steels. Hammers.

T: High-speed steels containing tungsten.

Contain 0.7

5%

C, 18%

W, 4%

Cr, 1%

V W: Water-hardening, high-carbon steels. W-1 plain carbon with 1%C

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Cast Iron Other ferrous metals include

cast iron (gray-3.5% carbon and >1% silicone and white- 2.5 - 3.5%

carbon and 0.5 - 1.5% silicon. )

ductile cast iron

malleable cast iron

wrought iron

Steel with >2% iron is cast iron because of the lack of ductility.

Carbon in form of graphite (gray) or iron carbide (white)

Grey cast iron has no ductility and will crack if heated or

cooled too quickly.

Grey cast iron has good compression strength, machinability, vibration

damping characteristics

Grey used for furnace doors, machine bases, and crackshafts

White cast iron has good wear resistance and is used in rolling

and crunching equipment

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Cast Iron Nodular or ductile cast iron is possible with the additions of

calcium, cerium, lithium, manganese, or sodium in 0.05%

Causes nodules (small balls or spheres instead of flat plates) or

spherulites to form if metal is allowed to cool slowly.

This removes stress risers in ordinary cast iron.

Ductile cast iron contains 4% Carbon and 2.5% Silicon Ductile iron is used for engine blocks, machine parts, etc.

Maleable cast irons are heat treated versions of white cast iron.

Cast iron with 2 to 3% Carbon is heated to 1750F, where iron carbide or

cementite is allowed to form spherulites. Similar to ductile cast iron Pearlitic malleable iron- heated to 1770F and quenched cooled

Ferritic malleable iron- heated to 1770F and air cooled

Special heat treated process gives malleable cast irons with min

elongation of 10%

to2

0%

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Stainless Steel Definition and Applications

Alloys that posses unusual resistance to attack bycorrosive media

Applications include aircraft, railway cars, trucks, trailers,...

AISI developed a 3digit numbering system for stainless steels

200 series: Austenitic- Iron-Cr-Ni-Mn Hardenable only by cold working and nonmagnetic

300 series: Austenitic- Iron-Cr-Ni

Hardenable only by cold working and nonmagnetic

General purpose alloy is type 304 (S30400)

400 series:

Ferritic- Iron-Cr alloy are not hardenable by heat treatment or cold working

Type 430 (S43000) is a general purpose alloy

Martensitic- Iron-Cr alloys are hardenable by heat treatment and magnetic

Type 410 (S41000) is a general purpose alloy

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Stainless Steel Corrosion of steels can be slowed with addition of Cr and Ni.

Stainless steels have chromium (up to 12%) and Ni (optional) ferritic stainless: 12% to 25% Cr and 0.1% to 0.35% Carbon

ferritic up to melting temp and thus can not form the hard martensitic steel.

can be strengthened by work hardening

very formable makes it good for jewelry, decorations, utensils, trim

austenitic stainless: 16% to 26% Cr, 6% to 23% Ni,

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Stainless Steel AISI developed a 3 digit numbering system for stainless steels

2

00 and3

00 series: Austenitic 400 series: Ferritic and martensitic

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Corrosion Ferrous metals rust because the iron reacts with oxygen to form iron oxide or

rust. Process is corrosion

Corrosion occurs as well when metal is in contact with water and metal ions

dissolved in water. Galvanic corrosion: electrochemical process which erodes the anode.

Metals in galvanic series: the further apart the worse the corrosion

Magnesium- most positive or anodic. Gives up electrons easily and corrodes

Aluminum

Zinc

Iron

Steel

Cast Iron

Lead Brass Copper

Bronze

Nickel

Stainless steel

Silver Graphite

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Introduction Nonferrous metals are those that do not contain iron

Many nonferrous metals are used in modern products Radioactive metals

uranium, thorium, plutonium as nuclear fuels.

zirconium is an alloying element and as a nuclear fuel.

Light metals

aluminum, beryllium, titanium as structural metals

calcium, lithium, magnesium, potassium, are used to extract metals from their

ores because they are too chemically reactive and too soft sodium and potassium are used in nuclear field as coolants

Heavy metals

Nickel and lead are used in many versatile applications

Copper is used for electrical and thermal applications

Cadmium, tin, and zinc are used in electrical applications and bearings

Cobalt and manganese are used as alloying elements for ferrous and non ferrous

Silver is used as a decorative and as a brazing alloy

Gold, silver, and platinum are used for electrical contacts and jewelry

Refractory metals (melt point > 3600F)

Columbium, titanium, tungsten, vanadium, and zirconium for high T, strength, hardness

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Aluminum

Aluminum is one of the most abundant elements in the earths crust

third to oxygen and silicon

8% of any clay is alumina, pure aluminum oxide (Al2O

3).

Extraction costs are lower for bauxite ore (Al2O

3*3H

20), hydrated aluminum ore.

Aluminum History

Aluminum discovered in 1825 by Hans Oested

Extraction process used reaction with sodium metal was very expensive.

Costs were $500 per pound. Royalty uses.

Charles Hall(1886) produced aluminum using electrolysis.

HallMethod involves the electrolysis of a molten solution of alumina in

cryolite or sodium aluminum fluoride at temperatures around 1745 F. Once in solution the Al separates by electrolysis.

Hall founded the Aluminum Company of America (ALCOA)

Bauxite first found near French town of Le Baux

Cost is as low as $0.15 per pound. Automotive is $1.50 per pound

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Aluminum Extraction

Majority of Bauxite in the US comes from Surinam, Jamaica, Guyana

Bauxite has iron oxides and other impurities.

Iron oxide difficult to remove since Al is very active metal, it will notreact with the Carbon as do iron and copper to reduce the oxide.

Steps in Aluminum production Ore is crushed and washed and then dried.

Dried powder is mixed with with soda ash (NaCO3

), lime (CaO), and water to formsodium aluminate (Na

2Al

2O4)

Effluent is filtered and then precipitated to yield aluminum hydrate [AlO(OH)]

Solution is heated to 2000F to form aluminum oxide (Al2O3) at 99.6% purity

Aluminum oxide is electrolyzed using Hall Method by placing in a container withcryolite at 1800F.

Large carbon electrodes are lowered into the molten solution, and a large directcurrent is applied (around 1000,000A). Electrodes are positively charged whereasthe lining of the container is the negative electrode.

Metallic aluminum is drawn off the bottom of the container and cast into ingots.

Aluminum is 99.5% to 99.8% pure with impurities being iron, manganese, andsilicon.

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Aluminum Properties

Properties

Corrosion resistant, Lightweight

Conductivity of 60% that of copper. Per pound conductivity is 2 x Cu

Low strength can be improved with alloys

FCC structure enables Al to be ductile and easily shaped. Attracts oxygen since it is chemically active.

Aluminum oxide is dull-gray and it sticks to the aluminum providing a

protection.

Anodizing of aluminum

Anode of aluminum is placed in an electroplating cell with oxalic, sulfuric, or

chromatic acid as the plating solution or electrolyte.

Current is applied to the solution causing the anode to be plated with a hard,

wear resistance surface.

Anodized coatings give the aluminum better appearance and may be colorized

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Wrought Aluminum Numbering System Wrought Numbering System

Aluminum Association developed system for cast and wrought Al

Wrought aluminum- 4 digit system, e.g. 2011 first digit represents alloying elements in the alloy

second digit represents alloy modifications or degree of control of impurities

third digit represents arbitrary numbers that indicate a specific alloy or indicate the purity

of the alloy over 90%

fourth digit represents same as third digit

Number Major Alloying Element

1---- None

2---- Copper

3---- Manganese

4---- Silicon

5---- Magnesium

6---- Magnesium and Silicon

7---- Zinc

8---- Other

9---- Unused

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Wrought Aluminum Numbering System

Common aluminum alloys Silicon alloys used for castings

Copper alloys used for machining

Magnesium alloys used for welding

Pure aluminum used for forming

Magnesium and silicon alloys used for extrusion

Copper alloys used for strength

Examples 2011 with 5% to 6% copper is a free machining alloy

2024 contains between 3.8% and 4.9% copper with 1.5% magnesium. This alloy isheat treatable aluminum alloy that is commonly used for aircraft parts.

3003 has 1% to 1.5% manganese which provides additional strength

4043 contains 4.5% to 6% silicon and is used in welding wire 5154 contains 3.1% to 3.9% magnesium and is weldable and available in sheets,

plates, and many structural shapes.

6063 contains approximately 0.5% magnesium and silicon and is used in windows,doors, and trim

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Casting Aluminum Numbering System Casting Numbering System

Cast aluminum- 3 digit system that is not generally standardized

Aluminum Association developed system for cast silicon casting alloys up to 99

silicon copper from 100 to 199

magnesium from 200 to 299

silicon manganese from300 to

399

Applications

Good conductor for electrical and electronics applications

Light weight good for structural applications that require mediumstrength and light weight.

High reflectivity for infrared and visible radiation make itdesirable for headlights, light fixtures, and insulations

Flake form is used for pigment

Cast Al engine blocks and pistons

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Casting Aluminum Heat Treatment Heat treatment

Internal structure of Al can be modified with heat treatment

Number system for heat treatment follows alloy designation Only copper, zinc and magnesium-silicon alloys can be age

hardened

Wrought alloys are not heat-treatable are given either an O

(annealed) suffux or an F (as-fabricated). Others are as follows

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Chromium Cr discovered in 1797 by Dr. Louis Vauguelin, Prof. of Chemistry at

the College of France

Named for its colorful nature Chromic oxide, Cr2O

3, has a dark green color

Potassium chromate, KCrO4, is bright yellow

Potassium dichromate, K2Cr

2O

7, is orange,

Chromium trioxide is red,

Lead chromate, PbCrO4, is yellow.

Chromium is the third hardest elementto Boron and Diamond

It is extremely resistant to corrosion and is often used as a corrosionresistant alloy or as a plating material.

Primary Chromium ore is chromite (FeOCr2O

3), typically found in

Albania, Russia, Rhodesia, Turkey, and Iran Reduction Process of Chromium (Most Cr is used in alloy form)

Grinding and crushing ore to powder

Reacted with powdered Al to release iron and chromium

Refined by electrolysis to obtain pure chromium (not always desired)

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Chromium Uses

Alloy for ferrous materials, e.g., HS steel, stainless steels, and other

metals, e.g., Ni alloys, refractories, and bronzes Plating material providing a hard, corrosion-resistant surface over

other materials.

Chromium will not stick to steel very well but will adhere to Nickel

Triple plating process is used to plate steels Steel is degreased and cleaned well,

Etched with nitric acid to roughen the surface of the steel,

Thin layer of copper is added to steel, then washed

Thin layer of nickel is added to copper then washed,

Final layer of chromium is added to nickel via Chromic acid.

Coating thickness of0.0002 inchprovide shiny decorative finish

Coating thickness of0.05 inchprovide wear resistance.

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Copper, Brass, and Bronze

Copper is one of the oldest metals- used by early civilizations

Copper is FCC Copper ores are found close to the earths surface as

oxide (cuprite)

sulfide (chalcopyrites, bornite, chalconite, and covellite)

carbonate (malachite and azurite) silicate form (chrysocolla)

Copper properties high thermal is 10 times that of steel, useful for chill, casting molds

melting point is 1981 F (however, oxides form when Cu is exposed toheat or environmental conditions thus surface treatments are needed.

electrical conductivity requires relatively pure copper

Silver, cadmium, and gold can be added to increase strength withoutsignificantly reducing conductivity

C A li ti

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Copper Applications Copper and Copper alloys are used for tubing and pipe and in

heat transfer applications.

Copper compounds are toxic and thus not used in food-related

Copper Alloys brass: alloy of copper and zinc

bronze: alloy copper and elements other than zinc

Copper is very useful in electrical applications A large percentage of Copper produced is used in electrical and

electronic industries.

At very low temps (absolute zero), Cu becomes asuperconductor.

Superconductors have very low resistance to current flow.

A current started in a superconductor will flow almost indefinitely. Magnetic Resonance Imaging (MRI) devices used in hospitals for

diagnosing patients are examples of superconductivity.

Future uses may include magnetic levitation (Mag-lev) trains beingprototyped in Japan today.

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Copper Smelting Process Copper Smelting Process

Copper ores are cleaned in a floatation process to remove silica

(sand), aluminum oxide (clays), and other unwanted materials. Floatation process

grind ores into powder and place in water.

foaming agent (soap) is added, creates a froth, brings the copper ore to surface.

Ore is skimmed off leaving undesirable materials in the water.

Concentrated ore is roasted in an oven to convert iron sulfides to ironoxides and contains copper oxides, copper sulfides, iron sulfates,silicates, and other impurities.

Ores are placed in smelting furnace and melted at 2600 F.

Melted ore is called matte copper, containing 30% copper.

Mixture placed in a converter with a flux (silica), air is blown through Sulfur is oxidized and removed from the melt by Sulfur dioxide bubbling

through the ore leaving blister copper.

Copper is 98% to 99% pure.

Slag drawn off t he mixture is further refined to extract other Au, Ag.

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Copper Electrical Wire Production Copper Electroplating

Small amounts of impurities reduces conductivity of the copper.

Impurities removed by electroplating Blister copper is remelted and cast into plates called anodes (+). Refined copper

cathodes (-) are placed on the other side in staggered pairs (figure below)

Plates are immersed in plating solution of copper sulfate.

Anode connected to Positive and cathode to Negative terminal of direct current.

When current is applied, the metal in the anode goes into solution and thecopper is plated on the cathode. Impurities in anode metal are left in the solution

Plating on cathode will be 99.9% pure copper.

Copper used in electrical wire is remelted using an oxidizing flame toprevent sulfur from being reabsorbed into the copper and keep oxygenless than 0.04%, called electrolytic tough pitch (ETP) copper.

Phosphorous is added to control the amount of oxygen in copper,oxygen-free high conductivity (OFHC) or phosphorous deoxidized(DHP) copper.

ll

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Copper Alloys

Copper alloys are among the oldest of metallic alloys

Alloying elements increase strength,hardness, machinability,appearance, and cost

Melting points of copper alloys are lower than that of pure copper.

Alloying elements

Aluminum, beryllium, lead, manganese,

Nickel, phosphorous, silicon, tin, and zinc

Brass: copper-zinc alloy

Zinc is added to increase strength, improve ductility, and improve machinability

Bronze: copper-tin alloy

Tin is added to improve strength, hardness, and ductility; reduce cost Names, compositions, and typical uses of copper alloys

There are more alloying elements in brasses than copper and zinc alone.

Brass and bronze are multi-component systems and have a phase diagram

C Z Ph Di

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Copper-Zn Phase Diagrams

Phase Diagram for Copper Zinc There are more alloying elements in brasses than copper and zinc alone.

Brass and bronze are multi-component systems and have a phase diagram.

Alfa brasses: up to 36% Zn can dissolve in Copper and form one phase. FCC

Beta phase is BCC

Alfa + Beta is 38% to 46% Zn

Brass Varieties: Yellow & Red

Red

less alloy better corrosion

most ductile and malleable

C Ti Ph Di

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Copper-Tin Phase Diagrams

Phase Diagram for Copper-Tin Bronze refers to metal alloys containing copper with any other metal

Traditionally copper and tin

Phosphorous added to improve ductility: phosphor bronzes (1% to 11% P)

Red Bronzes contain more than 90% copper

Al bronzes are heat treatable and highest strength bronzes. Uses structural

Si bronzes are high strength alloys of Cu and Ni. Uses in tubing as per

resistance to attack from fresh and salt water

Be bronzes (

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Magnesium

Magnesium discovered 1808 by Sir Davy is the lightest ofthe structural metals Mg weighs 66% as much as Al.

Derived from sea water. 1 lb of Mg from 100 gal of sea water.

Mg is hexagonal-closed pack in structure like most light meals.

Process

seawater is filtered through lime [Ca(OH)2] and oyster shells, which convertsthe Mg to Mg hydroxide and precipitates out of the water

HCl acid is added to convert MG hydroxide to Mg Cl

After drying, electrolysis decomposes the MgCl into Mg metal and chlorine gas

The Cl gas is recycled to HCl acid and Mg is drawn off.

Mg is active metal and was used first in incendiary bombs due to itburning with extremely hot flame, giving off intense heat.

Mg chips are readily ignitable making it dangerous to gas weld.

Mg used as anodes for protecting water tanks, piping, etc.

Mg used as alloy is ferrous metals, e.g., ductile cast iron.

Ni k l

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Nickel

Nickel closely resembles steel in many properties

Nickel is used for 5 cent coin, 75% Cu and 25 % Ni

Nickel supplied by Canada, Russia, and Australia in the form(FeNi)9S8 and pyrrhorite (iron sulfide with nickel)

Processing

Mond Process Carbon monoxide gas is washed and heated over ore which converts Ni tonickel carbonyl, which is very volatile.

It turns from solid to gas at temperatures above 1783 F.

Decomposition decomposes it into metallic nickel and carbon monoxide.

Extraction process similar to copper Ni ore is mined, crushed, and ground, washed, and concentrated by floatation

Ore is roasted and smelted in an electric furnace to produce matte

Matte is placed in converter, where air is blown through metal to produce blister

Blister Ni is remelted and cast into anodes, which are refined with electrolysis

Ni is placed on cathodes which is removed for fabrication or used as alloy

P i M t l

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Precious Metals Precious Metals due to value and use in jewelry and coinage.

Gold, silver, and platinum.

Limited applications in industry Gold (FCC structure)

Found as nuggets, dust, and in quartz rock (reacted with mercury orcyanide.

Most gold comes from South Africa Properties include electrical conductivity, corrosion resistance, andmalleability.

Applications include plating material via electroplating from AuCl,dental work as caps, crowns, and fillings. [Dental gold alloys are 70%

gold, 5%

platinum, 5%

palladium,25%

silver, 18%

copper,3%

nickel, 1% zinc.

Alloys of gold necessary because of inherent softness, Cu, Ni, andplatinum.

Purities are given in carat scale. 24 carat is pure gold. 12 carat is 50%

P i M t l

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Precious Metals

Silver (Ag, Latin argentum) FCC structure

Occurs in nature in argentite (Ag2

S) and horn silver (AgCl).

Properties: excellent malleability and ductility.

Applications:

US coins until 1964. Replaced by Nickel silver and copper.

Plating other metals as electrical conductors and jewelry.

Light sensitive compounds for photographic materials.

Approx. 30% of all silver goes toward photographic films and papers.

Photochromic (light sensitive) lenses for glasses which darken when exposed to

light

Brazing alloys and silver-cadmium batteries.

Explosives as silver fulminate.

Ointments, salves, and creams for medical purposes.

Gold and silver sold as Troy ounce, where there are 12 oz. to pound.

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Precious Metals

Platinum (FCC structure)

Platinum group contains 6 metals which are extracted from nickel ores

Includes iridium, osmium, palladium, rhodium, and ruthenium

All six have high melting points, > 3000F

Found in nature in the mineral sperrylite (PtAs2)

Applications:

corrosion resistant coatings and as a catalyst for many reactions.

High resistance wire for furnaces

Used in catalytic converters in automobiles, where it converts unburned

hydrocarbons and carbon monoxide to carbon dioxide and water.

Laboratory equipment, medical instruments, fine jewelry.

Disadvantage is cost, Pt is more expensive than gold