Metals are opaque, lustrous elements that are good conductors of heat and electricity.
Properties of Metals
(i) Physical Properties
(ii) Mechanical Properties
Physical Properties
1. Weight: Weight varies from metal to metal. Unit is $\displaystyle \small kg/sq.cm$, $\displaystyle \small kg/cm^{2}$.
2. Construction/Composition: If metals are broken and their construction is examined, they look different from one another.
3. Color: Every metal has different color. Ex: Copper-red, Aluminum-white.
4. Conductivity: Metals that allow free passage of electricity and heat through them are called conductors. Conduction of each metal is different.
5. Fusibility: It is the property of metal to change its state from solid to liquid on being heated to a certain temperature. Temperature at which metal turns into liquid is called melting point. Each metal has different melting point.
6. Magnetization: It is the property of metal to become a magnet. It is not necessary that each metal should possess ability of magnetization. Each metal has different magnetism.
Mechanical Properties
1. Elasticity: On application of external force/energy/weight the metal acquires elasticity (deforms) and regains its original shape on removal of external force.
2. Plasticity: Metal undergoes permanent deformation on application of certain magnitude of force.
3. Brittleness: It’s the property of metal to resist deformation. On application of external force/weight/energy, metal is broken into pieces and turn into powder.
4. Ductility: Metal can be drawn into thin wires without breaking (hammered thin or stretched into wire).
5. Toughness: Metal does not break on heavy impact (hammer blows) or bending. On heating, metal tends to lose its toughness.
6. Hardness: metal does not easily bend or break and has potential to cut or scratch another metal. Hardness decreases when a metal is heated. Ex: steel is harder than copper/aluminum.
7. Malleability: Metal can be beaten into sheets without heating. Forging and rolling can be done without heating.
8. Tenacity: Metal may stand a pull and does not break. Maximum pull that a metal can bear without breaking is called tensile strength. Tenacity is the property of metal to bear the effect of tensile forces.
Iron
$\displaystyle \small \bullet$ Iron mixture obtained from mines is called ore.
$\displaystyle \small \bullet$ This is not pure because it contains other materials such as oxygen, sulphur etc.
$\displaystyle \small \bullet$ Iron ore is purified to obtain pure iron.
$\displaystyle \small \bullet$ Types of iron ores:
$\displaystyle \small \circ$ Hematite: $\displaystyle \small Fe_{2}O_{3}$ Iron content is 60-65%
$\displaystyle \small \circ$ Magnetite: $\displaystyle \small Fe_{3}O_{4}$ Iron content is 70-73%
$\displaystyle \small \circ$ Limonite: $\displaystyle \small FeO(OH).n(H_{2}O)$ Iron content is 60%
$\displaystyle \small \circ$ Siderite: $\displaystyle \small FeCO_{3}$ Iron content is 40-43%
$\displaystyle \small \circ$ Pyrite: $\displaystyle \small FeS_{2}$ Iron content is 47%
(iii) Wrought Iron
(iv) Steel
Pig Iron
$\displaystyle \small \bullet$ Iron obtained from blast furnace is called pig iron.
$\displaystyle \small \bullet$ Blast furnace is a big circular cauldron of steel whose inside diameter is about 8m and its height is 30-40m.
$\displaystyle \small \bullet$ At the bottom, there is a hole for the molten metal to come out which is called Tapping hole.
$\displaystyle \small \bullet$ Molten iron is taken out of the tapping hole is put in moulds.
$\displaystyle \small \bullet$ Its diameter is 1-2m and height is 5-8m.
$\displaystyle \small \bullet$ In this, pig iron with hard coke and calcium stone are put.
$\displaystyle \small \bullet$ When the furnace is heated to 1350$\displaystyle \small ^{0}C$ , the metal melts. Melted iron is put into moulds.
$\displaystyle \small \bullet$ Cast iron consists of 2-4% carbon.
$\displaystyle \small \bullet$ It cannot be beaten.
$\displaystyle \small \bullet$ Its elasticity is less.
$\displaystyle \small \bullet$ It cannot be forged since it is brittle. It breaks on striking.
$\displaystyle \small \bullet$ Its particles are granular.
$\displaystyle \small \bullet$ If it is cooled immediately after heating, it becomes harder and tempering cannot be done.
$\displaystyle \small \bullet$ If it is cooled slowly it becomes soft, called graphite.
$\displaystyle \small \bullet$ It catches less rust.
$\displaystyle \small \bullet$ Becomes soft in salt water.
$\displaystyle \small \bullet$ Compressive strength is more.
$\displaystyle \small \bullet$ Melting point is low.
$\displaystyle \small \bullet$ Cannot be welded and magnetized.
$\displaystyle \small \bullet$ Types of cast iron:
$\displaystyle \small \circ$ Grey cast iron
$\displaystyle \small \star$ Soft and brown colour
$\displaystyle \small \star$ 92% iron, 3% graphite, 0.5% carbon, other miscellaneous ingredients
$\displaystyle \small \star$ Melting point is 1200$\displaystyle \small ^{0}C$ Friction is less
$\displaystyle \small \star$ Used in casting- machine frames, cylinders, pipes, pistons, flywheels
$\displaystyle \small \circ$ White cast iron
$\displaystyle \small \star$ Hard and brittle
$\displaystyle \small \star$ 9% iron, 3% carbon, 0.5% graphite
$\displaystyle \small \star$ Less prone to rust
$\displaystyle \small \star$ Machining cannot be done
$\displaystyle \small \star$ Parts requiring no machining are made out of it
$\displaystyle \small \circ$ Mottled cast iron
$\displaystyle \small \star$ Brittle
$\displaystyle \small \star$ 93.5% iron, 1.75% graphite, 1.75% carbon
$\displaystyle \small \star$ Catches less rust
$\displaystyle \small \star$ Used for making drain lids
$\displaystyle \small \circ$ Malleable cast iron
$\displaystyle \small \star$ Less hard and less tough
$\displaystyle \small \star$ No carbon content. Graphite is more so it is soft
$\displaystyle \small \star$ Made by heating white cast iron with silica at 1500$\displaystyle \small ^{0}C$ and then cooled down gradually in the same furnace
$\displaystyle \small \star$ It can be machined and can be beaten into sheets
$\displaystyle \small \star$ Used for making hubs, brake-pedal, elbows of pipe, sockets
$\displaystyle \small \circ$ Alloy cast iron
$\displaystyle \small \star$ Made by mixing cast iron with like nickel, chromium etc.
$\displaystyle \small \star$ Tensile strength in increased
Wrought Iron
$\displaystyle \small \bullet$ Made by melting white pig iron in puddling furnace.
$\displaystyle \small \bullet$ It is the purest form of iron. It contains 99.9% of iron.
$\displaystyle \small \bullet$ When heated, wrought iron does not melt but becomes soft.
$\displaystyle \small \bullet$ Hardening and tempering cannot be done by normal process.
$\displaystyle \small \bullet$ Malleable and ductile.
$\displaystyle \small \bullet$ No effect of salt water.
$\displaystyle \small \bullet$ Corrosion resistant.
$\displaystyle \small \bullet$ Used for making chain, draw boxes, hooks, wires, sheets and rivet etc.
$\displaystyle \small \bullet$ Contains other impurities like sulphur, phosphorus etc. which cannot be separated.
$\displaystyle \small \bullet$ Types of Steel
(i) Plain Carbon steel
(ii) Alloy steel
$\displaystyle \small \bullet$ Types of Plain carbon steel according to the percentage of carbon
$\displaystyle \small \circ$ Low carbon steel
$\displaystyle \small \star$ Also called mild steel
$\displaystyle \small \star$ Carbon is 0.15-0.25%
$\displaystyle \small \star$ Due to less quantity of carbon, it is sufficiently soft and tolerate the strain.
$\displaystyle \small \star$ Forging and rolling can be done
$\displaystyle \small \star$ Used for making nuts, bolts, rivets, sheets, wires, T-iron, angle iron etc.
$\displaystyle \small \circ$ Medium carbon steel
$\displaystyle \small \star$ Carbon is 0.25-0.5%
$\displaystyle \small \star$ Due to excess carbon, it is harder and tougher than mild steel
$\displaystyle \small \star$ Tenacity is more
$\displaystyle \small \star$ Can be hardened or tempered
$\displaystyle \small \star$ Used for making high tensile tubes, wires, agricultural implements, connecting rods, cam shafts, spanners, pulleys etc.
$\displaystyle \small \circ$ High carbon steel
$\displaystyle \small \star$ Carbon content is 0.5-1.5%
$\displaystyle \small \star$ It is very hard and tough
$\displaystyle \small \star$ It acquires permanent magnetic properties
$\displaystyle \small \star$ Used for making pointed tools, springs, dyepumps, files, cutleries, cold chisels, press die etc.
$\displaystyle \small \circ$ Low alloy steel
$\displaystyle \small \star$ It has low percentage of alloying metals
$\displaystyle \small \star$ Its tensile strength is more
$\displaystyle \small \star$ It can be hardened and tempered
$\displaystyle \small \star$ Used in manufacturing of parts of aeroplane and camshaft etc.
$\displaystyle \small \circ$ High alloy steel
$\displaystyle \small \star$ It has high percentage of alloying metals
$\displaystyle \small \star$ Types of High alloy steel
$\displaystyle \small \blacktriangle$ Stainless steel
$\displaystyle \small \circ$ Contains 0.2-0.6% carbon, 12-18% chromium, 8% nickel, 2% molybdenum
$\displaystyle \small \circ$ It has good electric and heat resistance
$\displaystyle \small \circ$ Used for making pipes, utensils, scissors, parts of aeroplane, knives, gears etc.
$\displaystyle \small \blacktriangle$ Cobalt steel
$\displaystyle \small \circ$ High carbon steel. Contains 5-35% cobalt
$\displaystyle \small \circ$ It has more toughness and tenacity
$\displaystyle \small \circ$ Used to make permanent magnet
$\displaystyle \small \blacktriangle$ High speed steel
$\displaystyle \small \circ$ Also called High tungsten alloy steel because it contains more quantity of tungsten
$\displaystyle \small \circ$ Used for cutting tools, reamers drilling, milling cutters, hacksaw blades etc.
$\displaystyle \small \blacktriangle$ Nickel steel
$\displaystyle \small \circ$ Contains 0.3% carbon, 0.25-0.35% nickel
$\displaystyle \small \circ$ Due to nickel, its tensile strength, elastic limit and hardness is increased
$\displaystyle \small \circ$ Used for making precious instruments
$\displaystyle \small \blacktriangle$ Vanadium steel
$\displaystyle \small \circ$ Contains 1.5% carbon, 12.5% tungsten, 4.5% chromium, 5% vanadium, 5% cobalt
$\displaystyle \small \circ$ Used for manufacturing tools
$\displaystyle \small \blacktriangle$ Manganese steel
$\displaystyle \small \circ$ Also called Mangalloy, Hard field steel
$\displaystyle \small \circ$ Contains 13% manganese
$\displaystyle \small \circ$ It has high impact strength
$\displaystyle \small \circ$ It has high resistance to abrasion
Non-ferrous Metals
1. Copper
$\displaystyle \small \bullet$ Best conductors of heat and electricity
$\displaystyle \small \bullet$ Reddish brown colour
$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Becomes soft on heating
$\displaystyle \small \bullet$ Can be welded even when it is red hot
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 1084$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 8.9
$\displaystyle \small \bullet$ Electrical resistivity is 1.682 μΩ-cm
$\displaystyle \small \bullet$ High tenacity. Tensile strength is from 3 to 4.7 $\displaystyle \small tonnes/cm^{2}$
$\displaystyle \small \bullet$ Used in alloys like brass, bronze, gun metal
$\displaystyle \small \bullet$ Used in wires, cables, windings of generators and transformers, overhead conductors, bus-bars, alloyed with gold for making ornaments
$\displaystyle \small \bullet$ Light grey colour
$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 660$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 2.70
$\displaystyle \small \bullet$ It is light weight
$\displaystyle \small \bullet$ Tensile strength and toughness is high
$\displaystyle \small \bullet$ Used in aircraft industry, used for making windows, doors, furniture, home appliances, wires, utensils, pipes, rods, sheets, parts of machines, heating appliances, parts of automobile engines
$\displaystyle \small \bullet$ Bluish white colour
$\displaystyle \small \bullet$ It is malleable and ductile at high temperatures (125$\displaystyle \small ^{0}C$ )
$\displaystyle \small \bullet$ Melting point is 420$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 7.1
$\displaystyle \small \bullet$ Electrical resistivity is 15.5 μΩ-cm
$\displaystyle \small \bullet$ Temperature coefficient of resistance is $\displaystyle \small 36\times 10^{-4}$ $\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ It is brittle
$\displaystyle \small \bullet$ Not affected by air
$\displaystyle \small \bullet$ Forms a coating when exposed to moisture
$\displaystyle \small \bullet$ Used for galvanizing steel parts and wires to protect against rusting
$\displaystyle \small \bullet$ Used in electric cells
$\displaystyle \small \bullet$ Zinc oxide is used in zinc paints
$\displaystyle \small \bullet$ Zinc chloride is used as wood preservative
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 327$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 11.4
$\displaystyle \small \bullet$ Used for coating electric cables, acid proof chambers, soldering, fuses, water pipes, roofings etc.
$\displaystyle \small \bullet$ It is good insulator against nuclear radiation
$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Not affected by air
$\displaystyle \small \bullet$ Melting point is 232$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 7.4
$\displaystyle \small \bullet$ Electrical resistivity is 11.5 μΩ-cm
$\displaystyle \small \bullet$ Temperature coefficient of resistance is $\displaystyle \small 45\times 10^{-4}$ $\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Soft metal
$\displaystyle \small \bullet$ Tensile strength is low
$\displaystyle \small \bullet$ Used as protective coating on steel sheets, domestic brass utensils
$\displaystyle \small \bullet$ Used for production of food containers
$\displaystyle \small \bullet$ High tensile strength
$\displaystyle \small \bullet$ Lower conductivity
$\displaystyle \small \bullet$ Can be welded and soldered easily
$\displaystyle \small \bullet$ High resistant to corrosion
$\displaystyle \small \bullet$ Ductile
$\displaystyle \small \bullet$ Cheaper than copper
$\displaystyle \small \bullet$ Specific gravity is between 8.2 to 8.7
$\displaystyle \small \bullet$ Electrical resistivity is 7.5 μΩ-cm
$\displaystyle \small \bullet$ Melting point is 890$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Used as fuse holders, lamp holders, switches, valves, tubes, lamps, socket outlets, sliding contacts for starters and rheostats, household utensils, water pipes, machine parts like bushes, automobile fittings, typewriter and parts of musical instruments
$\displaystyle \small \bullet$ Resists corrosion better than brass
$\displaystyle \small \bullet$ Used for making belts, gun metal and bearings
$\displaystyle \small \bullet$ Wears due to friction
$\displaystyle \small \bullet$ Whitish yellow colour
$\displaystyle \small \bullet$ Used for making bearings, glands, parts of machines, boiler fittings
$\displaystyle \small \bullet$ It is hard and brittle
$\displaystyle \small \bullet$ Used for making bells of temple
$\displaystyle \small \bullet$ Types of solder
$\displaystyle \small \circ$ Hard solder
$\displaystyle \small \star$ Solders which fuse only when red hot
$\displaystyle \small \star$ Used for metals which can withstand such temperature
$\displaystyle \small \star$ Used for metals such as iron, copper, brass, gun metal
$\displaystyle \small \circ$ Soft solder
$\displaystyle \small \star$ Melting point is upto 400$\displaystyle \small ^{0}C$
$\displaystyle \small \star$ Tensile strength is 5.7 $\displaystyle \small kg/mm^{2}$
$\displaystyle \small \star$ Ex: tin lead-tin solders
$\displaystyle \small \star$ Used for joining copper, bronze, brass etc.
$\displaystyle \small \star$ Due to poor mechanical strength, joints made by such solders should not be subjected to heavy mechanical stresses
$\displaystyle \small \bullet$ High thermal conductivity
$\displaystyle \small \bullet$ Good casting quality
$\displaystyle \small \bullet$ Low shrinkage after casting
$\displaystyle \small \bullet$ Economical
$\displaystyle \small \bullet$ Used for bearing loads
$\displaystyle \small \bullet$ White metal
$\displaystyle \small \bullet$ Tough metal i.e. ductile and can be readily machined
$\displaystyle \small \bullet$ Not affected by atmosphere
$\displaystyle \small \bullet$ Can be forged and casted
$\displaystyle \small \bullet$ Used to make rods, sheets, wires, tubing, valves, condenser tubes
$\displaystyle \small \bullet$ Used in scientific instruments and ornaments
$\displaystyle \small \bullet$ High heating effect
$\displaystyle \small \bullet$ Used in making furnaces and heating elements
Properties of Metals
(i) Physical Properties
(ii) Mechanical Properties
Physical Properties
1. Weight: Weight varies from metal to metal. Unit is $\displaystyle \small kg/sq.cm$, $\displaystyle \small kg/cm^{2}$.
2. Construction/Composition: If metals are broken and their construction is examined, they look different from one another.
3. Color: Every metal has different color. Ex: Copper-red, Aluminum-white.
4. Conductivity: Metals that allow free passage of electricity and heat through them are called conductors. Conduction of each metal is different.
5. Fusibility: It is the property of metal to change its state from solid to liquid on being heated to a certain temperature. Temperature at which metal turns into liquid is called melting point. Each metal has different melting point.
6. Magnetization: It is the property of metal to become a magnet. It is not necessary that each metal should possess ability of magnetization. Each metal has different magnetism.
Mechanical Properties
1. Elasticity: On application of external force/energy/weight the metal acquires elasticity (deforms) and regains its original shape on removal of external force.
2. Plasticity: Metal undergoes permanent deformation on application of certain magnitude of force.
3. Brittleness: It’s the property of metal to resist deformation. On application of external force/weight/energy, metal is broken into pieces and turn into powder.
4. Ductility: Metal can be drawn into thin wires without breaking (hammered thin or stretched into wire).
5. Toughness: Metal does not break on heavy impact (hammer blows) or bending. On heating, metal tends to lose its toughness.
6. Hardness: metal does not easily bend or break and has potential to cut or scratch another metal. Hardness decreases when a metal is heated. Ex: steel is harder than copper/aluminum.
7. Malleability: Metal can be beaten into sheets without heating. Forging and rolling can be done without heating.
8. Tenacity: Metal may stand a pull and does not break. Maximum pull that a metal can bear without breaking is called tensile strength. Tenacity is the property of metal to bear the effect of tensile forces.
Types of Metals
(i) Ferrous Metals
(ii) Non-ferrous Metals
| Ferrous Metal | Non-ferrous Metal |
|---|---|
| Metals contain high iron and carbon | Metals do not contain iron or carbon |
| This is of black and brown color | These are found in different colors |
| The melting point is high | The melting point is low |
| Prone to rust/catches rust | Doesn’t catch rust |
| These can be magnetized | These cannot be magnetized |
| These are brittle in cold state | These are brittle in hot state |
| These are rigid and strong | These are comparatively less strong and soft |
| Not costly | Costly |
| Ex: pig iron, wrought iron, cast iron, mild steel, nickel etc. | Ex: copper, zinc, aluminum, gold, silver etc. |
Iron
$\displaystyle \small \bullet$ Iron mixture obtained from mines is called ore.
$\displaystyle \small \bullet$ This is not pure because it contains other materials such as oxygen, sulphur etc.
$\displaystyle \small \bullet$ Iron ore is purified to obtain pure iron.
$\displaystyle \small \bullet$ Types of iron ores:
$\displaystyle \small \circ$ Hematite: $\displaystyle \small Fe_{2}O_{3}$ Iron content is 60-65%
$\displaystyle \small \circ$ Magnetite: $\displaystyle \small Fe_{3}O_{4}$ Iron content is 70-73%
$\displaystyle \small \circ$ Limonite: $\displaystyle \small FeO(OH).n(H_{2}O)$ Iron content is 60%
$\displaystyle \small \circ$ Siderite: $\displaystyle \small FeCO_{3}$ Iron content is 40-43%
$\displaystyle \small \circ$ Pyrite: $\displaystyle \small FeS_{2}$ Iron content is 47%
Classification of Iron
(i) Pig Iron
(ii) Cast Iron (iii) Wrought Iron
(iv) Steel
$\displaystyle \small \bullet$ Iron obtained from blast furnace is called pig iron.
$\displaystyle \small \bullet$ Blast furnace is a big circular cauldron of steel whose inside diameter is about 8m and its height is 30-40m.
$\displaystyle \small \bullet$ At the bottom, there is a hole for the molten metal to come out which is called Tapping hole.
$\displaystyle \small \bullet$ Molten iron is taken out of the tapping hole is put in moulds.
Cast Iron
$\displaystyle \small \bullet$ It is made out of pig iron
$\displaystyle \small \bullet$ Cupola furnace is used to obtain cast iron.$\displaystyle \small \bullet$ Its diameter is 1-2m and height is 5-8m.
$\displaystyle \small \bullet$ In this, pig iron with hard coke and calcium stone are put.
$\displaystyle \small \bullet$ When the furnace is heated to 1350$\displaystyle \small ^{0}C$ , the metal melts. Melted iron is put into moulds.
$\displaystyle \small \bullet$ Cast iron consists of 2-4% carbon.
$\displaystyle \small \bullet$ It cannot be beaten.
$\displaystyle \small \bullet$ Its elasticity is less.
$\displaystyle \small \bullet$ It cannot be forged since it is brittle. It breaks on striking.
$\displaystyle \small \bullet$ Its particles are granular.
$\displaystyle \small \bullet$ If it is cooled immediately after heating, it becomes harder and tempering cannot be done.
$\displaystyle \small \bullet$ If it is cooled slowly it becomes soft, called graphite.
$\displaystyle \small \bullet$ It catches less rust.
$\displaystyle \small \bullet$ Becomes soft in salt water.
$\displaystyle \small \bullet$ Compressive strength is more.
$\displaystyle \small \bullet$ Melting point is low.
$\displaystyle \small \bullet$ Cannot be welded and magnetized.
$\displaystyle \small \bullet$ Types of cast iron:
$\displaystyle \small \circ$ Grey cast iron
$\displaystyle \small \star$ Soft and brown colour
$\displaystyle \small \star$ 92% iron, 3% graphite, 0.5% carbon, other miscellaneous ingredients
$\displaystyle \small \star$ Melting point is 1200$\displaystyle \small ^{0}C$ Friction is less
$\displaystyle \small \star$ Used in casting- machine frames, cylinders, pipes, pistons, flywheels
$\displaystyle \small \circ$ White cast iron
$\displaystyle \small \star$ Hard and brittle
$\displaystyle \small \star$ 9% iron, 3% carbon, 0.5% graphite
$\displaystyle \small \star$ Less prone to rust
$\displaystyle \small \star$ Machining cannot be done
$\displaystyle \small \star$ Parts requiring no machining are made out of it
$\displaystyle \small \circ$ Mottled cast iron
$\displaystyle \small \star$ Brittle
$\displaystyle \small \star$ 93.5% iron, 1.75% graphite, 1.75% carbon
$\displaystyle \small \star$ Catches less rust
$\displaystyle \small \star$ Used for making drain lids
$\displaystyle \small \circ$ Malleable cast iron
$\displaystyle \small \star$ Less hard and less tough
$\displaystyle \small \star$ No carbon content. Graphite is more so it is soft
$\displaystyle \small \star$ Made by heating white cast iron with silica at 1500$\displaystyle \small ^{0}C$ and then cooled down gradually in the same furnace
$\displaystyle \small \star$ It can be machined and can be beaten into sheets
$\displaystyle \small \star$ Used for making hubs, brake-pedal, elbows of pipe, sockets
$\displaystyle \small \circ$ Alloy cast iron
$\displaystyle \small \star$ Made by mixing cast iron with like nickel, chromium etc.
$\displaystyle \small \star$ Tensile strength in increased
Wrought Iron
$\displaystyle \small \bullet$ Made by melting white pig iron in puddling furnace.
$\displaystyle \small \bullet$ It is the purest form of iron. It contains 99.9% of iron.
$\displaystyle \small \bullet$ When heated, wrought iron does not melt but becomes soft.
$\displaystyle \small \bullet$ Hardening and tempering cannot be done by normal process.
$\displaystyle \small \bullet$ Malleable and ductile.
$\displaystyle \small \bullet$ No effect of salt water.
$\displaystyle \small \bullet$ Corrosion resistant.
$\displaystyle \small \bullet$ Used for making chain, draw boxes, hooks, wires, sheets and rivet etc.
| Composition of Wrought Iron | |
|---|---|
| Elements | Percentage |
| Carbon | 0.02-0.03% |
| Manganese | 0.02-0.1% |
| Silicon | 0.1-0.2% |
| Phosphorous | 0.05-0.2% |
| Sulphur | 0.02-0.04% |
Steel
$\displaystyle \small \bullet$ This is pure iron.
$\displaystyle \small \bullet$ Carbon content is from 0.15%-1.5%. Due to excessive carbon, it is harder and tougher.$\displaystyle \small \bullet$ Contains other impurities like sulphur, phosphorus etc. which cannot be separated.
$\displaystyle \small \bullet$ Types of Steel
(i) Plain Carbon steel
(ii) Alloy steel
Plain Carbon Steel
$\displaystyle \small \bullet$ In this carbon and iron is mixed.$\displaystyle \small \bullet$ Types of Plain carbon steel according to the percentage of carbon
$\displaystyle \small \circ$ Low carbon steel
$\displaystyle \small \star$ Also called mild steel
$\displaystyle \small \star$ Carbon is 0.15-0.25%
$\displaystyle \small \star$ Due to less quantity of carbon, it is sufficiently soft and tolerate the strain.
$\displaystyle \small \star$ Forging and rolling can be done
$\displaystyle \small \star$ Used for making nuts, bolts, rivets, sheets, wires, T-iron, angle iron etc.
$\displaystyle \small \circ$ Medium carbon steel
$\displaystyle \small \star$ Carbon is 0.25-0.5%
$\displaystyle \small \star$ Due to excess carbon, it is harder and tougher than mild steel
$\displaystyle \small \star$ Tenacity is more
$\displaystyle \small \star$ Can be hardened or tempered
$\displaystyle \small \star$ Used for making high tensile tubes, wires, agricultural implements, connecting rods, cam shafts, spanners, pulleys etc.
$\displaystyle \small \circ$ High carbon steel
$\displaystyle \small \star$ Carbon content is 0.5-1.5%
$\displaystyle \small \star$ It is very hard and tough
$\displaystyle \small \star$ It acquires permanent magnetic properties
$\displaystyle \small \star$ Used for making pointed tools, springs, dyepumps, files, cutleries, cold chisels, press die etc.
| Composition of Plain Carbon Steel | |
|---|---|
| Elements | Percentage |
| Carbon | 0.15-1.5% |
| Manganese | 0.025-1.65% |
| Phosphorus | Maximum 0.04% |
| Sulphur | Maximum 0.05% |
| Iron | 97% |
Alloy Steel
$\displaystyle \small \bullet$ Steel is mixed with alloying elements like vanadium, manganese, tungsten etc.
$\displaystyle \small \bullet$ Types of Alloy Steel$\displaystyle \small \circ$ Low alloy steel
$\displaystyle \small \star$ It has low percentage of alloying metals
$\displaystyle \small \star$ Its tensile strength is more
$\displaystyle \small \star$ It can be hardened and tempered
$\displaystyle \small \star$ Used in manufacturing of parts of aeroplane and camshaft etc.
$\displaystyle \small \circ$ High alloy steel
$\displaystyle \small \star$ It has high percentage of alloying metals
$\displaystyle \small \star$ Types of High alloy steel
$\displaystyle \small \blacktriangle$ Stainless steel
$\displaystyle \small \circ$ Contains 0.2-0.6% carbon, 12-18% chromium, 8% nickel, 2% molybdenum
$\displaystyle \small \circ$ It has good electric and heat resistance
$\displaystyle \small \circ$ Used for making pipes, utensils, scissors, parts of aeroplane, knives, gears etc.
$\displaystyle \small \blacktriangle$ Cobalt steel
$\displaystyle \small \circ$ High carbon steel. Contains 5-35% cobalt
$\displaystyle \small \circ$ It has more toughness and tenacity
$\displaystyle \small \circ$ Used to make permanent magnet
$\displaystyle \small \blacktriangle$ High speed steel
$\displaystyle \small \circ$ Also called High tungsten alloy steel because it contains more quantity of tungsten
$\displaystyle \small \circ$ Used for cutting tools, reamers drilling, milling cutters, hacksaw blades etc.
$\displaystyle \small \blacktriangle$ Nickel steel
$\displaystyle \small \circ$ Contains 0.3% carbon, 0.25-0.35% nickel
$\displaystyle \small \circ$ Due to nickel, its tensile strength, elastic limit and hardness is increased
$\displaystyle \small \circ$ Used for making precious instruments
$\displaystyle \small \blacktriangle$ Vanadium steel
$\displaystyle \small \circ$ Contains 1.5% carbon, 12.5% tungsten, 4.5% chromium, 5% vanadium, 5% cobalt
$\displaystyle \small \circ$ Used for manufacturing tools
$\displaystyle \small \blacktriangle$ Manganese steel
$\displaystyle \small \circ$ Also called Mangalloy, Hard field steel
$\displaystyle \small \circ$ Contains 13% manganese
$\displaystyle \small \circ$ It has high impact strength
$\displaystyle \small \circ$ It has high resistance to abrasion
| Pig iron | Cast iron |
|---|---|
| Obtained from Iron ore | Obtained from Pig iron |
| Melting point is 1200$\displaystyle \small ^{0}C$ |
Melting point is 1250$\displaystyle \small ^{0}C$ |
| Has more carbon content | Less carbon content |
| Produced in Blast furnace | Produced in Cupola furnace |
| Brittle | Less brittle |
| Less suitable for engineering applications | Suitable for engineering applications |
| Wrought iron | Steel |
|---|---|
| It is 99.9% pure iron | It’s an alloy of iron and carbon. 97% iron |
| Has low carbon content | Has carbon content up to 1.7% |
| Obtained from Cast iron | Obtained from Pig iron |
| Cannot be hardened and tempered | Can be hardened and tempered |
| Melting point is 1530$\displaystyle \small ^{0}C$ |
Melting point is 1370$\displaystyle \small ^{0}C$ |
| Cannot withstand heavy shocks | Can withstand heavy shocks |
| More ductile. Less elastic property | Less ductile. Good elastic property |
| It cannot be alloyed with other metals | It can be alloyed with other metals |
| Less engineering application | Less engineering application |
Non-ferrous Metals
1. Copper
$\displaystyle \small \bullet$ Best conductors of heat and electricity
$\displaystyle \small \bullet$ Reddish brown colour
$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Becomes soft on heating
$\displaystyle \small \bullet$ Can be welded even when it is red hot
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 1084$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 8.9
$\displaystyle \small \bullet$ Electrical resistivity is 1.682 μΩ-cm
$\displaystyle \small \bullet$ High tenacity. Tensile strength is from 3 to 4.7 $\displaystyle \small tonnes/cm^{2}$
$\displaystyle \small \bullet$ Used in alloys like brass, bronze, gun metal
$\displaystyle \small \bullet$ Used in wires, cables, windings of generators and transformers, overhead conductors, bus-bars, alloyed with gold for making ornaments
2. Aluminium
$\displaystyle \small \bullet$ Ores are Bauxite and Cryolite
$\displaystyle \small \bullet$ Good conductors of heat and electricity$\displaystyle \small \bullet$ Light grey colour
$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 660$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 2.70
$\displaystyle \small \bullet$ It is light weight
$\displaystyle \small \bullet$ Tensile strength and toughness is high
$\displaystyle \small \bullet$ Used in aircraft industry, used for making windows, doors, furniture, home appliances, wires, utensils, pipes, rods, sheets, parts of machines, heating appliances, parts of automobile engines
3. Zinc
$\displaystyle \small \bullet$ Ore is sphalerite
$\displaystyle \small \bullet$ Electrical conductivity is almost half of copper$\displaystyle \small \bullet$ Bluish white colour
$\displaystyle \small \bullet$ It is malleable and ductile at high temperatures (125$\displaystyle \small ^{0}C$ )
$\displaystyle \small \bullet$ Melting point is 420$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 7.1
$\displaystyle \small \bullet$ Electrical resistivity is 15.5 μΩ-cm
$\displaystyle \small \bullet$ Temperature coefficient of resistance is $\displaystyle \small 36\times 10^{-4}$ $\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ It is brittle
$\displaystyle \small \bullet$ Not affected by air
$\displaystyle \small \bullet$ Forms a coating when exposed to moisture
$\displaystyle \small \bullet$ Used for galvanizing steel parts and wires to protect against rusting
$\displaystyle \small \bullet$ Used in electric cells
$\displaystyle \small \bullet$ Zinc oxide is used in zinc paints
$\displaystyle \small \bullet$ Zinc chloride is used as wood preservative
4. Lead
$\displaystyle \small \bullet$ Soft bluish grey colour
$\displaystyle \small \bullet$ It is malleable and ductile$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Melting point is 327$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 11.4
$\displaystyle \small \bullet$ Used for coating electric cables, acid proof chambers, soldering, fuses, water pipes, roofings etc.
$\displaystyle \small \bullet$ It is good insulator against nuclear radiation
5. Tin
$\displaystyle \small \bullet$ Good conductors of heat and electricity
$\displaystyle \small \bullet$ Bluish white colour with lustre$\displaystyle \small \bullet$ It is malleable and ductile
$\displaystyle \small \bullet$ Highly resistant to corrosion
$\displaystyle \small \bullet$ Not affected by air
$\displaystyle \small \bullet$ Melting point is 232$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Specific gravity is 7.4
$\displaystyle \small \bullet$ Electrical resistivity is 11.5 μΩ-cm
$\displaystyle \small \bullet$ Temperature coefficient of resistance is $\displaystyle \small 45\times 10^{-4}$ $\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Soft metal
$\displaystyle \small \bullet$ Tensile strength is low
$\displaystyle \small \bullet$ Used as protective coating on steel sheets, domestic brass utensils
$\displaystyle \small \bullet$ Used for production of food containers
Non-ferrous Alloys
1. Brass
$\displaystyle \small \bullet$ Alloy of 60% copper and 40% zinc$\displaystyle \small \bullet$ High tensile strength
$\displaystyle \small \bullet$ Lower conductivity
$\displaystyle \small \bullet$ Can be welded and soldered easily
$\displaystyle \small \bullet$ High resistant to corrosion
$\displaystyle \small \bullet$ Ductile
$\displaystyle \small \bullet$ Cheaper than copper
$\displaystyle \small \bullet$ Specific gravity is between 8.2 to 8.7
$\displaystyle \small \bullet$ Electrical resistivity is 7.5 μΩ-cm
$\displaystyle \small \bullet$ Melting point is 890$\displaystyle \small ^{0}C$
$\displaystyle \small \bullet$ Used as fuse holders, lamp holders, switches, valves, tubes, lamps, socket outlets, sliding contacts for starters and rheostats, household utensils, water pipes, machine parts like bushes, automobile fittings, typewriter and parts of musical instruments
| Types of Brass | Contents |
|---|---|
| Red Brass | 85% copper, 15% zinc |
| Brazing Brass | 60% copper, 40% zinc |
| Cartridge Brass | 70% copper, 30% zinc |
| Admiralty Brass | 70% copper, 29% zinc, 1% tin |
| Silicon Brass | 78% copper, 20% zinc, 2% silicon |
| Muntz Brass | 60% copper, 40% zinc |
2. Bronze
$\displaystyle \small \bullet$ Alloy of copper, tin, zinc
$\displaystyle \small \bullet$ Hard and brittle$\displaystyle \small \bullet$ Resists corrosion better than brass
$\displaystyle \small \bullet$ Used for making belts, gun metal and bearings
| Types of Bronze | Contents | Uses |
|---|---|---|
| Phosphor Bronze | 80% copper, 10% tin, 1% phosphorus | To manufacture bearings, gears, worm wheels, slide valves, current carrying springs, brush holders, knife switch blades, sliding contacts, parts exposed sea water or salty water |
| Aluminium Bronze | 89% copper, 8% aluminium, 2% tin, 1% zinc | To manufacture diecast parts, rollers, pump rods and slides |
| Bearing Bronze | 86.5% to 88.5% copper, 9.25% to 10.5% tin, 0.7% to 1.25% lead, 1.25% to 2.5% zinc | For pistons, bushes, pipe fittings, bearings |
| Manganese Bronze | 58.5% copper, 39% zinc, 0.8% manganese, 1.8% iron, 0.25% aluminium | For making domestic utensils, propeller blades, warm wheels |
3. Gun Metal
$\displaystyle \small \bullet$ Alloy of 88% copper, 10% tin, 2% zinc
$\displaystyle \small \bullet$ It is strong, hard and tough$\displaystyle \small \bullet$ Wears due to friction
$\displaystyle \small \bullet$ Whitish yellow colour
$\displaystyle \small \bullet$ Used for making bearings, glands, parts of machines, boiler fittings
4. Bell Metal
$\displaystyle \small \bullet$ Alloy of 82% copper, 18% tin
$\displaystyle \small \bullet$ Ores are sulphide of tin, copper and iron$\displaystyle \small \bullet$ It is hard and brittle
$\displaystyle \small \bullet$ Used for making bells of temple
5. Solder
$\displaystyle \small \bullet$ Solders are alloys used for making joints between pieces of metal
$\displaystyle \small \bullet$ It melts soon$\displaystyle \small \bullet$ Types of solder
$\displaystyle \small \circ$ Hard solder
$\displaystyle \small \star$ Solders which fuse only when red hot
$\displaystyle \small \star$ Used for metals which can withstand such temperature
$\displaystyle \small \star$ Used for metals such as iron, copper, brass, gun metal
$\displaystyle \small \circ$ Soft solder
$\displaystyle \small \star$ Melting point is upto 400$\displaystyle \small ^{0}C$
$\displaystyle \small \star$ Tensile strength is 5.7 $\displaystyle \small kg/mm^{2}$
$\displaystyle \small \star$ Ex: tin lead-tin solders
$\displaystyle \small \star$ Used for joining copper, bronze, brass etc.
$\displaystyle \small \star$ Due to poor mechanical strength, joints made by such solders should not be subjected to heavy mechanical stresses
6. Bearing Metals
$\displaystyle \small \bullet$ Anti-friction alloy. Low coefficient of friction
$\displaystyle \small \bullet$ High melting point$\displaystyle \small \bullet$ High thermal conductivity
$\displaystyle \small \bullet$ Good casting quality
$\displaystyle \small \bullet$ Low shrinkage after casting
$\displaystyle \small \bullet$ Economical
$\displaystyle \small \bullet$ Used for bearing loads
Nickel-Copper Alloy
1. Monel metal
$\displaystyle \small \bullet$ Alloy of 60% nickel, 38% copper, small amount of manganese or aluminium$\displaystyle \small \bullet$ White metal
$\displaystyle \small \bullet$ Tough metal i.e. ductile and can be readily machined
$\displaystyle \small \bullet$ Not affected by atmosphere
$\displaystyle \small \bullet$ Can be forged and casted
$\displaystyle \small \bullet$ Used to make rods, sheets, wires, tubing, valves, condenser tubes
2. German silver
$\displaystyle \small \bullet$ Alloy of 25% nickel, 60% copper, 15% zinc
$\displaystyle \small \bullet$ White metal$\displaystyle \small \bullet$ Used in scientific instruments and ornaments
Nichrome
$\displaystyle \small \bullet$ Alloy of 80% nickel, 20% chromium
$\displaystyle \small \bullet$ High resistivity$\displaystyle \small \bullet$ High heating effect
$\displaystyle \small \bullet$ Used in making furnaces and heating elements
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