Aluminum Characteristics of Non-ferrous Metals
Aluminum
O Aluminum is one of the most abundant elements in the earth's crust and also the most important of Non-ferrous Metals.
O Aluminum is a silvery white metal.
O It is a light metal with a density about a 1/3 of steel or brass.
O It is a good conductor of electricity.
o- On a conductivity to weight basis aluminum is a better conductor than copper.
O Aluminum is very ductile.
O Good corrosion resistance of aluminum is due to the thin oxide layer on its surface.
o- Aluminum has great affinity for oxygen.
o- Any fresh metal in air rapidly oxidizes to give a thin layer of oxide on the metal surface.
o- This surface layer is not penetrated by oxygen and protects the metal from further attack.
O Good conductor of heat, high thermal conductivity.
O Non magnetic. .
O Melting point of Aluminum= 650°C
O Fusion range of Aluminum Alloys = 520°C to 650°C.
Characteristics of Aluminum
O Some of its main characteristics are,
o- Light - weight (One - third the weight of steel)
o- High thermal and electrical conductivity
o- Non-toxicity .
o- Soft and ductile.
o- Low specific gravity.
o- High strength- to-weight ratio.
o- High reflectivity They exhibit toughness and high strength.
Advantages
O Lighter
O Strength comparable to steel
O Corrosion resistance
O Good machinability
O Can be anodized
O Better thermal and electrical conductivity Disadvantages
O Less strength (compared to the higher strength steel alloys)
O Not good for threaded fasteners
O More difficult to paint.
O Weld mends require post welding heat treat to recover mechanical properties.
O More difficult to weld
O Fatigues .
O High cost .
O Lower modulus of elasticity therefore increased deformation .
O Low elongation values.
Properties of aluminum alloy
O Aluminum forms high strength alloys in conjunction with other metals such as Cu, Cr, Ni, Fe, Zn, Mn, Si, & Mg.
O Some of Al alloys are more than four times as strong as the same weight of mild steel.
O They are Malleable and Ductile.
O They exhibit toughness and become stronger at temps below ordinary atmospheric.
O They do not work well at temps of the orders of 300°C to 400°C.
O Aluminum and its alloys can be,
o- Cast
o- Forged .
o- Welded.
o- Extruded, Rolled etc.
Application of Al and Al-alloys
Transportation Industry
O Structural frame work
O Engine parts .
Trim and Decorative Features
o- Hardware - Doors .
o- Window Frames .
o- Tanks .
o- Furnishing & Fittings
O Trains, Trucks, Buses, Automobile cars & airplanes use many component parts made up of aluminum alloys.
O In food industry, aluminum alloys find applications are,
o- Food Preparation Equipment's.
o- Refrigeration.
o- Storage containers .
o- Bakery equipment .
o- Shipping containers .
O In architectural field used for,
o- Window frames .
o- Doors hardware .
o- Roofing's
o-Railings .
o- Fasteners.
o- Lighting fixture
o- Solar Shading.
o- Grills etc.
O In process industries used to,
o- Handle organic chemicals
o- Petrochemnicals .
o- Drugs .
O Used to produce,
o- Tanks
o- Drums
o- Pipes .
o- Heat exchangers .
o- Gratings .
o- Smoke-stacks .
o- Precipitators
o- Centrifuges
o- Valves.
o- Fittings.
Aluminum alloys
O Duralumin : Al = 95 %, Cu = 4 %, Mn 0.5 %, Mg = 0.5 %.
O Magnalumin : Al = 70 to 90 %, Cu =1.75 % and Mg = 2 to 10 %.
O Hindalium : Mg = 3.5, and small percentage of chromium and rest of aluminum.
O Y Alloy :
W= 3.5 - 4.5.
Ni = 1.8 - 2.3 .
Mg = 1.2 - 1.7
Al = balance = 83 %
O Electron :
Al = 9 to 11 %
Zn = up to 3.5 % .
Mn = 0.5 % and Mg = Rest .
O Aluminum Alloys are Classified into following types. They are,
o- Wrought alloys
o- Cast alloys .
o- Heat - Treatable alloys .
o- Non Heat treatable alloys.
Duralumin
Duralumin Properties
O Light, Tough, Highly ductile, Easily Castable.
O Good conductors of heat & electricity.
O Corrosion Resistant.
O Approaches steel in strength and its density is one - third that of steel. Applications
O Due to Good strength and Low density.
o- Finds extensive use in Aircraft Industry.
o- Used in making Automobile and Locomotive parts.
O Due to High ductility and Good electrical conductivity.
o- Used in making Surgical instruments, Cables, Fluorescent tube caps.
Magnalumin
O Strong, tough & lighter than Al.
O Possesses mechanical properties similar to brass.
Applications
O Used for making cheap balances, airplane parts and Scientific instruments.
Electron Applications
O Used for Crank-cases of engines.
O Covers, Brackets, Similar lightly stressed components.
O Construction of Pans, Petrol, Oil tanks, Break components, Gear-Boxes etc.,
Stainless steel
O Adding chromium to low carbon steel gives it abrasion and corrosion resistance.
O In addition to iron, carbon, nickel and chromium, modern stainless steel may also contain other elements, such as niobium, molybdenum, and titanium.
O Nickel, molybdenum, niobium, and chromium enhance the corrosion resistance of stainless steel.
O It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, or stain 'less' than other types of steel.
O The sizes of chromium atoms and their oxides are similar, so they pack neatly together on the surface of the metal, forming a stable layer only a few atoms thick.
O If the metal is cut or scratched and the passive film is disrupted, more oxide will quickly form and recover the exposed surface, protecting it from oxidative corrosion.
O Iron, on the other hand, rusts quickly because atomic iron is much smaller than its oxide, so the oxide forms a loose rather than tightly-packed layer and flakes away.
O The passive film requires oxygen to self-repair, so stainless steels have poor corrosion resistance in low-oxygen environments.
O In seawater, chlorides from the salt will attack and destroy the passive film more quickly than it can be repaired in a low oxygen environment.
Applications of Stainless steel
O Stainless steel is resistance to corrosion and staining, It has low maintenance and is familiar to make it an ideal material for many applications.
O There are over 150 grades of stainless steel, of which fifteen are most commonly used.
Some Stainless Steels Grades
O 301 - High strength for roll formed structural components
O 303 - Free Machining bar grades
O 304 - Standard 18/8 grades
O 409 – Automotive exhaust grade - weld stabilized.
410 - Low-duty hardened applications.
430 - Resistant to mildly corrosive environment.
O The alloy is milled into coils, sheets, plates, bars, wire and tubing to be used in cookware, cutlery household hardware surgical instruments, major appliances, industrial equipment.
O An automotive and aerospace structural alloy and construction material in large buildings.
O It can be re - finished by any jeweler and will not oxidize or turn black.
O Some firearms incorporate stainless steel components as alternative an to blued or packetized steel.
Some automotive manufacturers use stainless steel as decorative highlights in their vehicles.
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