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MFGT 104Materials 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 the purposes 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

• Steel was used as long ago as 2000 B.C. when charcoal was packed with iron bars and heated to 1000°C.

• Steel is not an element, but an iron-carbon alloy that contains less than 2% carbon.

• Cast iron contains between 2% 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 from cementation

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 iron powder.

• 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 steel contains alloying elements that alter the properties– nickel, chromium, molybdenum

• High-alloy steel contains 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 (Fe2O3), 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 remove impurities 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 remove impurities as sulfur and silica.

– Process• Air is blown at the bottom of the furnace at 1100°F 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 3000°F.• 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 of 3000 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 room temperature 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• Mild steel, or low carbon steel, are produced in the greatest quantity 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 ExamplesLow carbon (mild) 0.05% - 0.32% Sheet, structuralMedium carbon 0.35% - 0.55% MachineryHigh carbon 0.60% - 1.50% Machine toolsCast 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 well as 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 on properties 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 working is 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 metal’s 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 0.75%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% to 20%

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Stainless Steel• Definition and Applications

– Alloys that posses unusual resistance to attack by corrosive 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, <0.15% Carbon • nonmagnetic and low strength % to 25% Cr and 0.1% to 0.35% Carbon

• machinable and weldable, but not heat-treatable

• used for chemical processing equipment, food utensils, architectural items

– martensitic stainless: 6% to 18% Cr, up to 2% Ni, and 0.1% to 1.5% C• hardened by rapid cooling (quenching) from austenitic range.

• Corrosion resistance, low machinability/weldability used for knives, cutlery.

– Marging (high strength) steels: 18% to 25% Ni, 7% Co, with others• heated and air cooled cycle with cold rolled

• Machinable used for large structures, e.g., buildings, bridges, aircraft

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

– 200 and 300 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 earth’s crust

– third to oxygen and silicon

– 8% of any clay is alumina, pure aluminum oxide (Al2O3).

– Extraction costs are lower for bauxite ore (Al2O3*3H20), 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.

– Hall Method 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 not

react 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 form

sodium aluminate (Na2Al2O4)– 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 with

cryolite at 1800F.– Large carbon electrodes are lowered into the molten solution, and a large direct

current is applied (around 1000,000A). Electrodes are positively charged whereas the 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, and

silicon.

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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 digitNumber Major Alloying Element1---- 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 is heat 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 from 300 to 399

– Applications• Good conductor for electrical and electronics applications• Light weight good for structural applications that require medium strength and light weight.• High reflectivity for infrared and visible radiation make it desirable 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, Cr2O3, has a dark green color– Potassium chromate, KCrO4, is bright yellow– Potassium dichromate, K2Cr2O7, is orange,– Chromium trioxide is red,– Lead chromate, PbCrO4, is yellow.

• Chromium is the third hardest element to Boron and Diamond• It is extremely resistant to corrosion and is often used as a corrosion

resistant alloy or as a plating material.• Primary Chromium ore is chromite (FeOCr2O3), 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 of 0.0002 inch provide shiny decorative finish

– Coating thickness of 0.05 inch provide 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 earth’s 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 to

heat or environmental conditions thus surface treatments are needed.– electrical conductivity requires relatively pure copper– Silver, cadmium, and gold can be added to increase strength without

significantly reducing conductivity

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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 a superconductor.– 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 being

prototyped 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 iron oxides 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 the copper

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 to prevent sulfur from being reabsorbed into the copper and keep oxygen less 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.

•

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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

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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

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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 (<2% Be) are heat treatable and highest strength copper alloy. Non-sparking when struck by another metal. Uses with explosives.

– Nickel bronzes named Nickel silver and German Silver used for coins

» Present dimes and quarters are 75% Cu and 25% Ni clad over and inner core of copper

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Magnesium• Magnesium discovered 1808 by Sir Davy is the lightest of

the 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 converts the 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 it burning 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.

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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 to

nickel 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

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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 or

cyanide.– Most gold comes from South Africa– Properties include electrical conductivity, corrosion resistance, and

malleability.– 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, and platinum.

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

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Precious Metals• Silver (Ag, Latin argentum) FCC structure

– Occurs in nature in argentite (Ag2S) 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