Sonepat 6 All matters whether solid, liquid or gas consists of molecules which are bonded together to form the bulk material. Each molecule is further composed of tiny particles called atom. Individual properties of atoms and their arrangements in the molecule determine the properties of the material.
Sonepat 7 A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds.H2 , O2 & N2 are not compounds but H2 O, CO2 & CH4 are compounds.
Sonepat 8 In solids, molecules are quite close & have definite shape & volume. In liquids, molecules are relatively at more distances & have definite volume but no definite shape. In gases, molecules are at very large distance & have neither definite volume nor definite shape.
Sonepat 11 3. An atom of any element consists of the nucleus and the electrons. 4. The nucleus is a stationary mass, situated at the centre and carrying a net positive charge. 5. It consists of heavy particles: protons and neutrons. 6. Each of these particles are 1836 time heavier than the electrons.
Sonepat 12 7. Each proton carries a positive charge while the neutrons carries no charge. 8. An electron has a very small mass, and carries a net negative charge. 9. In its normal state, an atom carries equal number of electrons and protons, and is therefore electrically neutral.
Sonepat 14 Crystal structure: When atoms of any substance come together to form crystal is known as crystal structure. Crystal is a solid in which the constituent atoms, molecules or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions.
Sonepat 15 Crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a unit cell. This structure depends upon 1. Grouping of the atoms 2. Bonding between the atoms 3. Types of space lattice
Sonepat 17 Molecular structure: Molecular structure are formed when a limited number of atoms come together and get strongly bonded to another. The resulting groups are called molecules e.g. H2 O, CO2 , Cl4 , O2 , N2 etc. Usually they have covalent or ionic bonds.
Sonepat 18 Amorphous Structure: This type of structures are formed when atoms do not have the long repetitive pattern of arrangement and the pattern breaks at different places. Common examples of this group are glasses and polymers.
Sonepat 19 Microstructure: The appearance of the structure of a material under a microscope is called microstructure. Optical microscopes magnifies 1000 times whereas electronic microscopes can produce magnifications up to several thousands times.
Sonepat 22 Inter-Atomic Bonds: The bond between atoms makes it possible to combine to form a solid. Inter-atomic bonds are of three main types: 1. Metallic bond 2. Covalent bond & 3. Ionic bond. These bonds determine the electric conductivity of the materials.
Sonepat 23 Metallic bond: This type of bond exists in metals and their alloys e.g. brass which is the combination of copper & zinc. Stainless steel (composed of iron, chromium, carbon and nickel). 14 karat gold (composed of gold and copper).
Sonepat 24 It is a connection between atoms formed by sharing, rather than transferring electrons. Covalent bond: Silicon & Germanium has 4 electrons each in their outer most orbit. They share electrons.
Sonepat 25 Ionic bond: The bond taking place between sodium & chlorine. Sodium (11 electrons) has 1 electron in its outer most orbit and Chlorine (17 electrons) has 7. For some atoms it is easier to lose electrons than to pick up new ones.
Sonepat 29 Metal is an element or mineral, which is used in all work of engineering. As small as the needle and as big as machines, bridges, aeroplanes etc. all are produced out of metals. Most of the metals are solid at room temperature & have different properties.
Sonepat 37 4. Conductivity: Metals are good conductor of heat & electricity. 5. Magnetic: Iron, steel, cobalt & nickel are attracted by magnets but others are not. 6. Fusibility: Copper melts at 1083°C but tin at 232°C.
Sonepat 39 2. Malleability: Is that property of the metal due to which it permanently extends in all directions without getting ruptured upon hammering, rolling etc. to change its size and shape. before Before After
Sonepat 42 Hardness also means several qualities of a metal. 1. Resistance to abrasion, scratching, cutting or shaping. 2. May indicate strength, stiffness, brittleness, elasticity, toughness or combination of all above.
Sonepat 43 Hardness of a metal is measured by the hardness tester & is given in number. HRC: Hardness Rockwell ‘C’ is given for the metals of US origin. BHN: Brinell Hardness Number is for the metals of UK (EN series) origin. Shore hardness is use for measuring the indentation hardness of non-metals.
Sonepat 47 Symbol Element Density (g/cm3) Melting Point (°C) Ag Silver 10.5 961 Al Aluminium 2.7 660 Au Gold 19.3 1063 C Carbon Graphite 2.25 3550 Cu Copper 8.9 1083 Fe Iron 7.86 1535 Mn Manganese 7.5 1244 Mo Molybdenum 10.21 2610 Na Sodium 0.97 98
Sonepat 48 Symbol Element Density (g/cm3) Melting Point (°C) Ni Nickel 8.9 1453 P Phosphorus 1.82 44 Pb Lead 11.35 327 Sb Antimony 6.69 630 Si Silicon 2.4 1420 Sn Tin 7.3 232 W Tungsten 19.27 3380 Zn Zinc 7.13 420 Hg Mercury 13.6 -38
Sonepat 50 Ferrous metal: Metal or alloy in which iron is the major constituent and is easily separated from other materials with magnets e.g. pig, iron & steel. Non-ferrous metal: Metal or alloy that are free of iron or its alloys e.g.. copper, brass, bronze, aluminum bronze, lead,
Sonepat 51 Types of iron ore with iron %.: 1. Haematite (Fe2 O3 ), up to 70% iron. 2. Magnetite (Fe3 O4 ), up to 72.4% iron. 3. Limonite (2Fe2 O3 , 3H2 O), up to 59.8% iron. 4. Siderlite (FeCO3 ), up to 48.2% iron. 5. Geothite (Fe2 O3 , H2 O) up to 62.9%.
Sonepat 52 The separation of iron from iron ore is achieved by smelting it with coke and limestone in a blast furnace. Coke is combustible material for the blast furnace and supplies carbon required for making carbon monoxide gas. Limestone acts as a flux. It soaks up impurities and forms slag.
Sonepat 54 Hot air at about 800°C is blown through pipes called tuyere (like is a nozzle). The molten iron thus taken out from the bottom of the blast furnace is called pig iron. The slag produced is used mainly to build roads. A blast furnace once started may work for 5-10 years.
Sonepat 55 Pig iron: Pig iron absorbs varying amounts of carbon, silicon, sulphur, phosphorous and manganese during smelting process. A high amount of carbon makes the pig iron very hard and brittle & unsuitable for making any useful article. It lacks strength, ductility and resistance to shock.
Sonepat 57 Cast iron: Cast iron is produced by remelting pig iron in a cupola furnace. A cupola furnace is like a vertical steel stack lined with fire bricks on the inside. The charge which is added to the cupola furnace consists of coke, pig iron, scrap cast iron, steel and limestone.
Sonepat 58 The charge is loaded from the top of the cupola and it moves down as it starts melting. The air blast is directed near the bottom of the stack. It burns the coke and generates heat required to melt the charge. The operation of the cupola is not continuous.
Sonepat 61 Cast Iron & Types: Cast iron is an alloy of iron, carbon and silicon. The carbon content ranges from 2% to 4%. 1. Grey cast iron. 2. White cast iron 3. Malleable cast iron and 4. Nodular cast iron.
Sonepat 63 Grey cast iron: 1. This is widely used for the casting of machinery parts and can be machined easily. 2. Machine bases, tables, slide ways are made of cast iron because it is dimensionally stable after a period of aging. 3. Because of its graphite content, cast iron provides an excellent bearing and sliding surface.
Sonepat 64 4. The melting point is lower than that of steel and as grey cast iron possesses good fluidity, intricate casting can be made. 5. Grey cast iron is widely used for machine tools because of its ability to reduce vibration and minimise tool chatter.
Sonepat 65 6. Grey cast iron, when not alloyed, is quite brittle and has relatively low tensile strength. Due to this reason it is not used for making components subjected to high stress or impact loads. 7. Grey cast iron is often alloyed with nickel, chromium, vanadium or copper to make it tough. 8. Grey cast iron is weldable but the base material needs preheating.
Sonepat 66 Wrought Iron: Wrought iron is produced from pig iron by puddling (stirring molten iron with iron oxide) in a reverberatory furnace. The lower part of the furnace is covered with iron oxide on which the pig iron is charged. On heating, impurities like silicon, phosphorous, manganese and carbon get oxidized and form slag.
Sonepat 67 The iron oxide present in the slag reacts chemically with carbon, silicon, manganese, sulphur and phosphorous which may still be there in the charge. Due to puddling, the charge impurities are burnt off. Wrought iron is the purest form of iron as much as 99% of iron. When heated, wrought iron doesn’t melt, but only becomes pasty and in this form it can be forged to any shape.
Sonepat 68 Wrought Iron-Properties: 1. It becomes soft at white heat and it can be easily forged & welded. 2. It is used for making temporary magnets not permanent. 3. It can not be cast. 4. It is ductile, malleable & tough. 5. It is moderately elastic. 6. It is not affected by salt water. 7. It resists corrosion in a better way.
Sonepat 69 8. Melting point is about 1500 °C. 9. Its specific gravity is about 7.8. 10. Its ultimate compressive strength is about 2000 kgf/cm2 (200 MPa). 11. Its ultimate tensile strength is about 4000 kgf/cm² (400 MPa).
Sonepat 71 Steel: Steel is the most widely used engineering material because of its relative advantages over other materials. Steel is fundamentally an alloy of iron and carbon, with the carbon contents varying up to 1.5%. The carbon present is in a combined state.
Sonepat 72 Steel possesses following points of merit; 1. It is cheap and readily available. 2. It can have all mechanical properties. 3. Properties of steel can be improved easily by addition of small amounts of other elements known as alloying elements. 4. Any desired combination of strength and ductility an be obtained by different heat treatments. 5. Good machinability and weldability.
Sonepat 75 Type Classifica tion % of Carbon Property & Uses Low Carbon Steel Dead Mild Steel 0.10% to 0.12% Highly ductile. Used for making wire, rods, thin sheets& solid drawn tubes. Mild Steel 0.15% to 0.30% Soft & ductile. Used for general workshop purposes, boiler plates, bridge work, structural sections and drop forgings.
Sonepat 76 Classific ation % of Carbon Property & Uses Medium Carbon Steel 0.3% to 0.5% Used for making axles, drop forgings, high tensile tubes, wires and agricultural tools. 0.5% to 0.7% Harder, tougher and less ductile. Used for making springs, locomotive tyres, large forging dies, wire ropes, hammers and snap of riveters.
Sonepat 77 Classific ation % of Carbon Property & Uses High Carbon Steel 0.7% to 0.9% Harder, less ductile and slightly less tough. Used for making sprigs, small forging dies, shear blades and wood chisels. 0.9% to 1.1% Used for making cold chisels, press dies, punches, wood working tools, axes etc.
Sonepat 79 Killed steel: During the steel making process, oxygen may dissolved in the liquid metal & combine with carbon to form carbon monoxide bubbles. The CO bubbles trapped in the casting may initiates for the failure of steel. This can be eliminated through the addition of deoxidising agents such as aluminium, ferro-silicon and manganese.
Sonepat 80 Low Alloy Steel: When steel is mixed with other metals in lesser quantity, it is called low alloy steel. 1. Besides carbon, other metals are in lesser quantity. 2. Its tensile strength is more. 3. It can be welded. 4. It can also be hardened and tempered. 5. It is used in manufacturing various parts of an aeroplane and camshafts.
Sonepat 81 High alloy steel: Besides carbon, it has a high percentage of the other metals. It is of following types. 1. High Speed Steel 2. Nickel Steel 3. Vanadium Steel 4. Manganese Steel 5. Stainless Steel 6. Silicon Steel 7. Cobalt Steel and ………………….
Sonepat 82 High Speed Steel: 1. HSS is widely used in the manufacture of machine tools and other cutters. 2. It can withstand higher temperatures without losing its temper (hardness). 3. It cuts faster than high carbon steel, hence the name high speed steel. 4. At room temperature HSS and HCS have an equivalent hardness but HSS become advantageous at higher temperature.
Sonepat 83 It is also called high tungsten alloy steel because it has more quantity of tungsten. Let’s take an example; 25% tungsten means that it roughly has 75% steel. The melting point of Tungsten is 3400C & that of iron is 1600C. Simple arithmetic: 850+1200=2050C.
Sonepat 84 Nickel Steel: 1. It contains 0.3% carbon and 0.25% to 0.35% nickel. 2. Due to the presence of nickel its tensile strength, elastic limit and hardness is increased. 3. It does not catch rust . 4. Its cutting resistance increases 6 times more than the plain carbon and steel due to 0.35% presence of nickel.
Sonepat 85 5. This is used for making rivets, pipes, axle shafting, parts of bus and aeroplanes etc. 6. If 5% of cobalt is mixed with 30-35% of nickel, it becomes invar steel, which is used for making precious instruments.
Sonepat 86 Vanadium Steel: 1. It contains 1.5% carbon, 12.5% tungsten, 4.5% chromium, 5% vanadium and 5% cobalt. 2. Its elastic limit, tensile strength and ductility is more. 3. It has strength to bear sharp jerks. 4. It is used for manufacturing tools.
Sonepat 87 Stainless Steel: 1. Along with iron, it contains 0.2 to 0.6% carbon, 12 to 18% chromium, 8% nickel and 2% molybdenum. 2. It does not catch rust. 3. It is not affected by acid. 4. It is magnetic proof. 5. It is used for making knives, scissors, utensils, pipes, gears parts of aeroplane etc.
Sonepat 88 Silicon Steel: 1. It contains 14% silicon. Its uses vary according to the percentage of silicon. 2. The 0.5 to 1% silicon and 0.7 to 0.95% manganese mixture is used for constructional work. 3. The 2.5 to 4% silicon content mixture is used for manufacturing electric motors, generator, laminations of transformers. 4. The 14% silicon content mixture is used in chemical industries.
Sonepat 90 Manganese Steel: 1. It is also called special high alloy steel. 2. It contains 1.6 to 1.9% of manganese and 0.4 to 0.5% carbon. 3. It is hard and wears less. 4. It is not effected by magnet. 5. It is used in grinders and rail points etc.
Sonepat 91 Cast Iron & Steel Carbon content is high. Carbon content is less. Carbon is in free state. Carbon is mixed. Melting point is low. Melting point is high. It can not be magnetised. It can be magnetised. It is brittle, no forging. It can be forged. It does not rust easily It rusts quickly. Special welding. Ordinary welding Difference between
Sonepat 93 Microstructure: The appearance of the structure of a material under a microscope is called microstructure. Optical microscopes magnifies 1000 times whereas electronic microscopes can produce magnifications up to several thousands times.
Sonepat 94 Micro-constituents: Micro means very small which can not be seen with naked eye or power glass. Constituent means being the part of a whole. Micro-constituent means the smallest particle out of which the whole is made.
Sonepat 95 Critical Temperature: The temperature at which the phase transformations take place are important from the point of view of heat treatment of the alloys. Due to this reason, these temperatures are called critical temperatures or critical points.
Sonepat 96 Examples of phase transitions include: State Known as The solid-to-liquid : Melting The liquid-to-solid : Freezing The liquid-to-gas : Boiling/Vapourising The gas-to-liquid : Condensation The solid-to-gas : Sublimation The gas-to-solid : Deposition
Sonepat 97 Lower Critical Temperature: The temperature at which the change of structure to austenite starts, is called the lower critical temperature. Upper Critical Temperature: The temperature at which the structure of steel completely changes to austenite is called the upper critical temperature. This varies depending on the percentage of carbon in steel.
Sonepat 98 Example: In case the percentage of carbon in steel is 0.57 and 1.15, the lower critical temperature is 723C, and the upper critical temperature is 800C. For 0.84% carbon steel, both LCT and UCT are 723C. This steel is called eutectoid steel.
Sonepat 102 Cementite 1. Cementite or iron carbide is a chemical compound with the formula Fe3 C. 2. It has an orthorhombic crystal structure. 3. It is a hard & brittle material. 4. In its pure form, classified as ceramic.
Sonepat 103 5. In carbon steel, it is either formed from austenite during cooling or from martensite during tempering. 6. It mixes with ferrite, the other product of austenite to make pearlite. Pearlite + Cementitie
Sonepat 104 Pearlite: 1. Pearlite is the alternating layers of ferrite and cementite that occurs in steel. 2. It is formed as austenite is slowly cooled below 723°C with the formula Fe3 C. 3. Steel with less carbon content will not transform into pearlite. 4. The appearance of pearlite under the microscope resembles like pearl.
Sonepat 106 Martensite: 1. Martensite, named after the German metallurgist Adolf martens (1850- 1914). 2. Martensite most commonly refers to a form of ferrite supersaturated with carbon found in very hard steels. 3. Such steels are used as springs and piano wires.
Sonepat 107 4. The martensite is formed by rapid cooling quenching of austenite which traps carbon atoms that do not have time to diffuse out of the crystal structure. 5. In the 1880’s, Martens studied samples of different steels under a microscope, and found that the hardest steels had a regular crystalline structure.
Sonepat 108 6. He was the first to explain the cause of the widely differing mechanical properties of steels. 7. Since chemical processes acceleartes at higher temperature, martensite is easily destroyed by the application of heat. 8. Too much martensite leaves steel brittle, too little leaves it soft.
Sonepat 109 Austenite: 1. Austenite is a metallic, non-magnetic solid solution of carbon and iron that exists in steel above the critical temperature of 723°C. 2. It is named after Sir William Austen (1843-1902). 3. Its structure allows it to hold a high proportion of carbon in solution.
Sonepat 110 4. As austenite cools, it transforms into a mixture of ferrite and cementitie as the dissolved carbon falls out of solution. 5. Depending on alloy composition and rate of cooling, pearlite may form. 6. If the rate of cooling is very fast, the alloy may experience martensitic transformation. 7. The rate of cooling determines the therefore the mechanical properties.
Sonepat 115 Aluminium-Extraction: 1. Aluminium is reactive therefore it is difficult to extract from its ore, aluminium-oxide. 2. Therefore, it is extracted by elctrolysis; that is, the aluminium oxide is dissolved in molten cryolite and then reduced to the pure metal. 3. Cryolite is a mixture of aluminium, sodium, and calcium fluorides.
Sonepat 116 Aluminium-Properties: 1. Aluminium is soft, lightweight metal with normally dull silvery appearance. 2. It is caused by a thin layer of oxidation that forms quickly when the metal is exposed to air. 3. Aluminium oxide has a higher melting than pure aluminium. 4. Aluminium is non-toxic, non-magnetic, and non-sparking.
Sonepat 117 5. Aluminium is about one-third as dense as steel or copper. 6. It is malleable, ductile and easily machined and cast. 7. It has excellent corrosion resistance and durability because of the protective oxide layer. 8. Aluminium mirror finish has the highest reflectance of any metal. 9. Aluminium is a good heat conductor.
Sonepat 118 Aluminium-Application: 1. Transportation 2. Packaging 3. Treatment against fish parasites. 4. Construction 5. Consumer durable goods 6. Electric 7. Machinery 8. Powdered aluminium, used in silvering agent in paints.
Sonepat 119 9. Heat sinks in electronics. 10. It is used in the blades of weapons 11. Used in glass making. 12. Aluminium oxidises very energetically and as a result has found use in solid rockets fuels, thermite, and other pyrotechnique compositions. 13. Aluminium is also a super conductor at low temperatures of 1.2 K.
Sonepat 121 Copper--Extraction: 1. It is the oldest known metal found as ore in mines, contains 30% copper. 2. Ore is heated with silica, coke and lime in the reverberatory furnace. 3. On heating cuprous sulphide and ferrous oxide is formed. 4. Ferrous oxide with silica forms slag which is taken out. 5. Cuprous sulphide is heated again and is oxidised and copper is obtained.
Sonepat 122 Copper-Properties: 1. It is reddish with a bright metallic reflecting surface. 2. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). 3. Its alloys, brass and bronze, are very important. 4. Blue vitriol is the most important compounds
Sonepat 123 Copper-Applications: 1. Coinage, utensils, plumbing etc. 2. Bio-medical applications. 3. General engineering works. 4. As an alloying element. 5. Electrical wire, motor windings, thimbles, terminal ends etc.
Sonepat 125 Lead-Extraction: 1. The main lead mineral is galena (PbS), which contains 86.6% lead. 2. More than half of the lead used currently comes from recycling. 3. Froth flotation & sintering processes are used to obtain pure lead.
Sonepat 126 Lead-Properties: 1. Lead is a soft, heavy, toxic & malleable metal. 2. It is bluish white when freshly cut but changes to dull gray if exposed to air. 3. High resistance to corrosion. 4. Poor conductor of electricity. 5. It is poisonous. 6. It can be hardened by adding antimony.
Sonepat 127 Lead-Application: 1. Lead is used for making batteries. 2. Used in making bullets. 3. Colouring element for glazing in ceramic tiles. 4. Lead is used as shielding from radiation. 5. It changes the optical characteristics of the glass and reduces the transmission of radiation.
Sonepat 128 6. Lead is as electrodes in the process of electrolysis. 7. Lead is used in solder for electronics, 8. Used in high voltage power cables as sheathing material to prevent water diffusion into insulation. 9. Lead is added to reduce wear. 10.It is also used in weights.
Sonepat 130 Silver-Extraction: 1. Silver is found in native form, combined with sulphur, arsenic, antimony or chlorine. 2. The principal sources of silver are copper, copper-nickel, gold-lead, and lead-zinc ores. 3. This metal is also produced during the electrolytic refining of copper. 4. It is 99.9% pure.
Sonepat 131 Silver-Properties: 1. Silver is very ductile and malleable. 2. It has a brilliant white metallic luster that can take a high degree of polish. 3. It has the highest electrical conductivity of all metals, even higher than copper, but it is costly. 4. Pure silver also has the highest thermal conductivity.
Sonepat 132 Silver-Applications: 1. The malleability, non-toxicity and beauty of silver make it useful in dental alloys for fittings and fillings. 2. Polishing of mirror, photography, electrical contacts, explosives etc. 3. Widely used for making ornaments, coins, utensils. 4. Silver means money in at least 14 languages.
Sonepat 134 Tin-Extraction: 1. About 35 countries mine tin throughout the world. 2. Tin is produced by reducing the ore with coal in a reverberatory furnace 3. Most of the Tin is produced from cassiterite (SnO2 ).
Sonepat 135 Tin-Properties: 1. Tin is a malleable, ductile, highly, crystalline, silvery-white metal. 2. When a bar of tin is bent, a strange crackling sound known as the "tin cry" can be heard due to the breaking of the crystals. 3. This metal resists corrosion from distilled, sea and soft tap water 4. But can be attacked by strong acids.
Sonepat 136 5. Tin forms the dioxide SnO2 when it is heated in the presence of air. 6. Tin can be highly polished and is used as a protective coat for other metals in order to prevent corrosion or other chemical action. 7. Tin is malleable at ordinary temperatures but is brittle when it is heated.
Sonepat 137 Tin-Applications: 1. Tin is used for coating lead, zinc & copper to prevent corrosion. 2. Tin-plated steel containers are widely used for food preservation. 3. Some important tin alloys are; i. Bronze ii. Bell metal iii.Babbit metal iv.Soft solder v. White metal etc.
Sonepat 140 Zinc-Properties: 1. Zinc is bluish-white metal. 2. It looses shine in moist air and burns in air with a bright greenish flame. 3. It reacts with acids and alkalis and other non-metals. 4. It is malleable and can easily be beaten into various shapes. 5. Above 210°C, the metal becomes brittle and will be pulverized by beating.
Sonepat 141 Zinc-Application: 1. Zinc is the fourth most common metal in use, trailing only iron, aluminium & copper in annual production. 2. Zinc is used to galvanize steel to prevent corrosion. 3. Zinc is used in for making alloys. 4. Zinc is used in die casting of automobile parts, container of battery, paints, medicines etc.
Sonepat 142 Babbit metal: 1. Also called white metal. 2. Used to provide the bearing surface. 3. It was invented in 1839 by Issac Babbit. 4. This metal is characterized by its resistance to stain or rust. 5. Its compositions may have (i) 90% tin 10% copper. (ii) 89% tin 7% antimony & 4% copper (iii) 80% lead, 15% antimony & 5% tin
Sonepat 143 Brass: 1. Brass is the term used for alloy of copper and zinc. 2. The amount of zinc varying from 5 to 45 percent to create a range of brasses each with unique properties. 3. Brass has a yellow colour, somewhat similar to gold. 4. Brass has been known to man since prehistoric times, long before zinc itself was discovered.
Sonepat 144 Brass types: 1. Admiralty brass: 30% zinc and 1% tin. 2. Alpha brass: With less than 35% zinc. 3. Alpha-beta brass (Muntz metal), also called duplex brass, is 35-45 % zinc 4. Aluminum brass contains aluminum, which improves its corrosion resistance. 5. Arsenical brass contains an addition of arsenic and frequently aluminium and is used for boiler fire boxes. 6. Beta brasses, with 45-50 % zinc
Sonepat 145 7. Cartridge brass is a 30% zinc brass with good cold working properties. 8. Common brass, or rivet brass, is a 37% zinc brass, cheap and standard for cold working. 9. High brass, contains 65% copper and 35% zinc, has a high tensile strength and is used for springs, screws, rivets. 10.Leaded brass is an alpha-beta brass with an addition of lead. It has excellent machinability.
Sonepat 146 11. Low brass is a copper-zinc alloy having 20% zinc with a light golden color, excellent ductility and is used for flexible metal hoses and metal bellows. 12. Naval brass, similar to admiralty brass, is a 40% zinc brass and 1% tin. . 13. Brass can be used for cryogenic containers.
Sonepat 147 Bronze: 1. Bronze refers to a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorous, manganese, aluminium or silicon. 2. It is strong and tough and has many uses in industry. 3. It was particularly significant in antiquity, giving its name to the Bronze.
Sonepat 150 German Silver: 1. It is white and bright and contains 25 to 50% copper, 25 to 35% zinc and 15 to 35% nickel. 2. It is white and bright. 3. It is used for making domestic utensils. 4. It is widely used for cheap jewellery and the base metal for silver plating. 5. The letters EPNS on silverware stand for electroplated nickel silver.
Sonepat 151 Gun metals: 1. It contains 88% copper, 10% tin and 2% zinc. 2. It is hard, strong and tough. 3. It wears less due to friction. 4. It is whitish yellow. 5. It is used for making bearings, glands, parts of machine, boiler fittings etc.
Sonepat 152 Nichrome: 1. It contains 80% nickel & 20% chromium. 2. It is good conductor of electricity and gets heated when electricity is passed through it. 3. It is widely used in heaters, irons, cookers etc. as their heating elements.
Sonepat 153 Solder: 1. It melts soon & is used for soldering metals. 2. It is mixed in varying quantities with other metals for soldering different metals. 3. It is of two types hard solder & soft solder.
Sonepat 159 Purpose of Normalising: 1. To eliminate coarse-grained structure 2. To remove internal stresses (caused by working) 3. To improve the mechanical properties of steel. Method of Normalising: 1. Heat the metal to temperatures within the normalising range. 2. Hold at this temperature for a short time (15 minutes) & cool it in air.
Sonepat 161 Method of Hardening: 1. Heat the steel to a temperature above critical point (hardening temperature). 2. Hold at this temperature considerable period 3. Quench in water/oil/molten salt bath.
Sonepat 162 Purpose of Tempering: 1. To stabilise the structure of the metals 2. To reduce internal stresses 3. To reduce some of the hardness produced during hardening 4. To increase the ductility of the metal 5. To give the metal right structural condition combined with toughness and shock resistance.
Sonepat 163 Method of Tempering: 1. Reheat the steel after hardening to temperatures below critical point. 2. Hold at this temperature for a considerable time 3. Cool it slowly (4-5 minute for each mm of section).
Sonepat 165 Reasons: 1. Wear and fatigue start at the surface. 2. It is the surface where stress concentration appears from small cut or notch, scratches, tool marks etc. 3. Engine connecting rods, for example are never uniformly stressed. 4. Rotating shafts have maximum stress at the surface and minimum at the centre.
Sonepat 166 On the other hand, the core of the components should be; 1. Relatively soft to support the hard case, otherwise the material becomes brittle. 2. Tough, if a crack develops on the surface, it should be stopped when it reaches the core, instead of continuing through the core.
Sonepat 167 Therefore, for many engineering components it is desirable to have different properties at the surface and at the core. By basic heat treatment processes, such as annealing, normalising, hardening and tempering, it is possible to obtain steels in any condition either soft, tough or hard.
Sonepat 168 But how to achieve different properties at the surface and at the core of the same component? Such a combination of properties at different places of the same component can be achieved by a special heat treatment called case hardening or surface hardening.
Sonepat 169 Case hardening: 1. It is a process for hardening a ferrous material having have carbon content of 0.15% to 0.3%, so that they will not respond to direct hardening. 2. In such a manner that the surface layer, known as the case is substantially harder than the remaining material known as the core.
Sonepat 170 3. Carbon content at the surface is increased to about 0.9%. 4. When this is heated and quenched, only the surface layer gets hardened. 5. Core will remain soft and tough as required. 6. The surface, which must remain soft can be insulated against carburising by coating it with a suitable paste or by plating it with copper.
Sonepat 171 The chemical composition is changed by inserting the following chemical & based on that is their method. Carbon Carburising NitrogenNitriding Cynide Cyniding & Carbon + Nitrogen Carbo-nitriding
Sonepat 172 Pack Carburising: 1.The parts are packed in a suitable metal box in which they are surrounded by the carburising medium. 2.The lid is fitted to the box and is sealed with fire-clay and tied with a piece of wire so that no carbon gas can escape and no air can enter the box to cause decarburisation.
Sonepat 174 What happens on carburising? (i) The low carbon steel work piece is heated in contact with the carbon rich compound. (ii) The outer surface absorbs carbon and becomes high carbon steel (iii) It is hardened by heating first & then quenching the case becomes hard and the core which is of low carbon steel remains soft and tough because the core remains as low carbon steel.
Sonepat 175 Surface hardening: Surface hardening a process which is used to improve the wear resistance of parts without affecting the interior (core) of the part. This is done by; 1. Flame hardening & 2. Induction hardening.
Sonepat 177 2. The hardening temperature is generally about 50C higher than that for full hardening. 3. The heat is applied to the surface very rapidly and the work is quenched immediately by spraying it with water so that the heat is not conducted more than necessary into the work-piece. 4. Steels used for surface hardening will have a carbon content of 0.35% to 0.7%.
Sonepat 178 Advantages: (i) The hardening devices are brought to the work-piece. (ii) It is advantageous for large work- pieces. (iii) Short hardening time. (iv) Great depth of hardening. (v) Easily controlled. (vi) Small distortion and (vii) Low fuel consumption.
Sonepat 180 Induction hardening: 1. This is a production method. 2. In this method, the part to be surface- hardened is placed within an inductor coil through which a high frequency current is passed. 3. The depth of penetration of the heating becomes less, as the frequency increases. 4. After induction hardening of the work- pieces, stress relieving is necessary.
Sonepat 182 Effect of frequency on case depth Sr. No. Frequency of Induction Heating in Case depth produced after quenching in mm. 1 1,000 Hz 4.5 to 8 mm 2 3,000 Hz 3.75 to 5 mm 3 10,000 Hz 2.50 to 3.75 mm 4 120,000 Hz 1.5 to 2.5 mm 5 500,000 Hz 1to 2 mm 6 1000,000 Hz 0.25 to 0.75 mm
Sonepat 183 Heat treatment of non-ferrous metals: Annealing: Like steel, non-ferrous metals can be softened by heating and allowing to cool. However, only a few non-ferrous alloys can be hardened by heating and quenching Since most of them can not be hardened by quenching, the rate of cooling is not important.
Sonepat 184 In fact, copper components are often quenched in water. This not only saves time but also cleans the black oxide film from the surface of the components because of rapid contraction. Non Ferrous Metals Annealing Temperature (C) Cold working brasses 600-650 Copper 650-750 Aluminium 500-550 Duralumin 480-500
Sonepat 185 Soaking: When the steel on being heated reaches the required temperature, it is held in the same temperature for a period of time. This allows the heating to take place throughout the section uniformly. This process is called soaking. Why do we keep Roti on Tava? Dirty clothes in surf water?
Sonepat 186 Soaking Time: This depends upon the cross-section of the steel, its chemical composition, the volume of the charge in the furnace. A good general guide for soaking time in normal conditions is five minutes per 10 mm of thickness for carbon and low alloy steels and 10 minutes per 10 mm of thickness for high alloy steels.
Sonepat 188 Brine solution gives a faster rate of cooling while air cooling has the slowest rate of cooling. Brine solution (sodium chloride) gives severe quenching because it has; 1. higher boiling point than pure water 2. The salt content removes the scales formed on the metal surfaces due to heating.
Sonepat 189 Water is very commonly used for plain carbon steels. While using water, as a quenching medium, the work should be agitated. This can increase the rate of cooling. Cold air is used for hardening some special alloy steels.
Sonepat 190 The quenching oil used should be of a low viscosity. Special quenching oils, which can give rapid and uniform cooling with less fuming and reduced fire risk, are commercially available. Oil is widely used for alloy steels where the cooling rate is slower than plain carbon steels.
Sonepat 193 Aluminium (Al): 1. It is used as de-oxidiser. 2. It restricts the growth of Austenite. 3. It is used as alloying element in nitriding steel. Boron (B): 1. It increases hardenability to a greater extent.
Sonepat 194 Carbon (C): It is dissolved in pure liquid iron and if the solution is solidify slowly the carbon tends to separate out giving a structure, which is a mixture of pure iron and graphite. This gives a fairly tough iron, which breaks with a dark glistering fracture. It is easily machined.
Sonepat 195 If the same iron is cast and cooled slowly; i. Then it is hard ii. It has a higher tensile strength iii. Then is difficult to machine iv. Then it breaks with a close white fracture which is iron carbide, called cementite.
Sonepat 196 Cadmium (Cd): The melting point of cadmium is 320C. Cadmium is used for coating steel components. This has been used particularly to electroplate steel where a film of cadmium only 0.05 mm thick will provide complete protection against the sea.
Sonepat 197 Chromium (Cr) When added to steel, improves the corrosion resistance, toughness and hardenability. Stainless steel contains about 13% chromium. Chromium-nickel steel is used for bearings, chrome-vanadium steel for making hand tools like spanners & wrenches.
Sonepat 199 Cobalt (Co): It has wear resistance at very high temperatures. It is used for making magnets, ball bearings, cutting tools. Cobalt high speed steel (sometimes known as super HSS) contains about 5 to 8% cobalt due to which it has better hardness and wear resistance properties than the 18% tungsten HSS.
Sonepat 201 Manganese (Mn): Addition of manganese to steel increases hardness and strength but decreases the cooling rate. Manganese steel can be used to harden the outer surface for providing a wear resisting surface with a tough core.
Sonepat 203 Molybdenum (Mo): The melting point of molybdenum is 2620 C. This gives high resistance against softening when heated. Molybdenum high speed steel contains 6% of molybdenum, 6% of tungsten, 4% chromium and 2% vanadium. This high speed steel is very tough and has good cutting ability.
Sonepat 204 Phosphorus (P): Phosphorus in cast iron adds fusibility and fluidity but induces brittleness. Hence, it is rarely allowed to increase 1.0%. Phosphoric ions are useful, however, for castings when cheapness is essential.
Sonepat 206 Silicon alloyed steels are used in manufacturing of springs. Silicon is also used in certain type types of steel to improve its resistance to corrosion. Cast iron contains about 2.5% silicon which helps in the formation of free graphite which promotes the machinability of cast iron.
Sonepat 207 Sulphur (S): Sulphur is generally regarded as harmful in cast iron. It lowers the viscosity of the melt and tends to make the cast iron hard and brittle. Therefore it is necessary to keep it well below 0.1% for most foundry purposes.
Sonepat 210 This is used as an alloying metal for the production of high speed cutting tools which is an alloy of 18% tungsten, 4% chromium & 1% vanadium. Stellite is an alloy of 30% chromium, 20% tungsten, 1 to 4% carbon and the balance cobalt.
Sonepat 211 Vanadium (Va): This improves the toughness of steel. Vanadium steel is used in the manufacture of gears, tools etc. Vanadium high speed steel contains 0.70% carbon and about 10% vanadium which is considered as a superior high speed steel.
Sonepat 212 Chrome-vanadium steel contains 0.5 to 1.5% chromium, 0.15 to 0.3% vanadium & 0.13 to 1.10% carbon. Chrome-vanadium steel has high tensile strength, elastic limit and ductility hence it is used for making springs, gears, shafts, drop forged components etc.
Sonepat 216 Physical properties: 1. Non-metals are usually brittle and can not be used to make sheets or wires. 2. Non-metals usually do not have lustrous and cannot be polished. Only graphite and iodine are lustrous. 3. They are generally bad conductors of heat and electricity. The only exception is graphite, which is a good conductor of electricity.
Sonepat 217 4. A non-metal atom has 4, 5, 6, 7 or 8 electrons in its outer most shell. These electrons are not free or mobile. This is why non-metals do not conduct electric current. 5. Non-metals can be easily broken, i.e. the tensile strength of non-metals is low. 6. Non-metals have low melting and boiling points (exception is graphite).
Sonepat 218 7. They have low densities. 8. The solid non-metals e.g. sulphur and phosphorous are soft but carbon in the form of diamond, is very hard. 9. Non-metals do not produce any sound when struck with an object. 10. Non-metals exist in all the three states of matter. 11. All non-metals, except hydrogen, are electro-negative.
Sonepat 219 Ceramics: A ceramic is a compound formed by the combination of metallic and non-metallic elements. The typical examples of ceramic materials are; 1. Refractories, 2. Glasses, 3. Abrasives, 4. Enamels, 5. Insulating materials etc.
Sonepat 221 Refractories: 1. They withstand high temperatures. 2. Possess good mechanical strength. 3. Heat resistance and retain a constant volume. 4. Resistance to thermal shock. 5. These materials are used in furnaces either to support the heating element or to form the linings of the inner parts of the furnace.
Sonepat 222 6. Refractory materials, can be used at temperatures greater than 900 C. 7. Refractory materials are available in different shapes and sizes. 8. Common shapes are dense refractory blocks, lightweight bricks, refractory tubes, protection tubes, melting crucibles, and powder form. 9. Lightweight bricks and refractory powder are used as an insulating material.
Sonepat 224 Glass: 1. Glass is one of the oldest and most useful materials known to us. 2. When a liquid cools without crystallization taking place, it is known as glassy state. 3. In its structures, atoms do not have the long repetitive pattern and the pattern breaks at different places. 4. It is a material that is thick & resistant to flow.
Sonepat 225 5. Glass is manufactured by mixing the materials in proper proportions include sand, soda ash, limestone, dolomite, feldspar, sodium sulphate, broken glass etc. 6. The mixture is melted by heating up to 1500C. Some modifiers and refining agents are added to the melt. 7. The melt can be cast, drawn or rolled to produce different shapes.
Sonepat 226 Types of Glasses: Depending upon the chemical compositions, glasses can be classified into the following types. 1. Silica glass (fused glass) 2. Soda-lime-silica glasses 3. Borosilicate glasses 4. Aluminosilicate glasses and 5. Lead glasses.
Sonepat 227 Silica glass (fused glass): 1. Silica or quartz glass is a single-oxide glass and is made from commercially pure SiO2 . 2. It is known for high melting point, low co-efficient of thermal expansion and high chemical resistance. 3. This type of glass is suitable for use as laboratory ware. 4. It contains 96 to 99.9% silica depending upon the cost.
Sonepat 228 Soda-lime-silica glass: 1. The glasses are characterized by the presence of 15-25% Na2 and CaO. 2. This type of glass is widely used in the manufacture of glass containers, flat & plate glass, domestic ware, electrical lamps, bulbs etc.
Sonepat 229 Borosilicate glass: 1. The Presence of boric oxide (B2 O3 ) and Al2 O3 , results in better thermal shock resistance and chemical durability. 2. This is called Pyrex glass and greatly used in laboratory, medical ware, telescope lenses and chemical piping.
Sonepat 230 Aluminosilicate glass: 1. This glass contains about 10-15% Al2 O3 which improves strength and chemical durability of the glass. 2. One such type, known as E-glass (lime aluminoborosilicate), is used in the manufacturing of glass fibres. 3. It has high strength and thermal shock resisting characteristics.
Sonepat 231 Lead glass: 1. Addition of lead oxide (PbO) to glass improves its refractive index and lowers the melting point. 2. This type of glass is used where high refractive index, dispersion and radiation shielding are required. 3. Combination of K2 O, PbO, BaO and ZnO produce glass suitable for optical applications. 4. They are called flint glasses.
Sonepat 233 Properties of glass: 1. Glass is a super cooled liquid and considered as a brittle amorphous solid (without a clearly defined shape or form). 2. Its optical properties show an index of refraction of about 1.5, which can be varied to accommodate special needs. 3. It becomes ductile at elevated temperatures.
Sonepat 234 4. Its importance lies in the fact that it is chemically stable. 5. It is insoluble in water. 6. It has greater resistance to wear and abrasion than steel. 7. The specific gravity of glass averages about 2.5. 8. The co-efficient of thermal expansion is very low. 9. Leaded glass softens at 600 C and fused silicate glass at1550 C.
Sonepat 235 Application of glass: 1. Glass containers and bottles are extensively used as they are sufficiently strong, chemically inert and resistant to thermal shock. 2. Used as vitreous coatings on ceramic and metal surfaces. 3. Safety glass is used in automobiles due to its transparency, resistance to ultraviolet light, and resistance to shattering.
Sonepat 236 4. The largest use of glass is in the building construction. Various types of glasses used in buildings are transparent, translucent, decorative and roughened glasses, glass blocks, mirror glasses and glass claddings. 5. A recent development in glass is in the fibre form. Glass fibres are used for insulation purposes (thermal, sound & electrical) and as reinforcing materials.
Sonepat 238 Polymers: 1. The word polymer means "many parts." 2. A polymeric solid material may be considered to be one that contains many chemically bonded parts or units which themselves are bonded together to form a solid. 3. Two industrially important polymeric materials are plastics and rubbers. 4. Polymers have already taken part of the market for commercial grade steels.
Sonepat 239 Advantages: Good corrosion resistance, Low density, and where different shape and colour are the deciding factors. Disadvantages: Low strength & high temperature. It is convenient to classify polymers into three distinct classes. 1.Thermoplastic materials 2.Thermosetting materials and 3.Silicones.
Sonepat 240 Thermoplastic: They can be softened, hardened, or re- softened repeatedly by application of heat. By alternate heating and cooling they can be reshaped many times. Some common thermoplastics are: 1. Polyethylene 2. Polyvinylchloride (PVC) 3. Nylon 4. Acrylics etc.
Sonepat 241 Thermosetting: They undergo setting and hardening on heating and cooling. Once, they have been set and hardened, they can not be re melted and returned to their original state. 1. Bakelite 2. Vulcanised rubber 3. Duroplast 4. Epoxies etc.
Sonepat 243 Silicones: Silicones are largely inert compound with wide variety of forms and uses. They are heat resistant, non-stick and rubber like. They are Polymers that include silicon together with carbon, hydrogen, oxygen etc.
Sonepat 244 They are heat resistant, non-stick & rubber like frequently used in cookware, Medical applications, sealant, lubricants etc. Properties: 1. Thermal stability (-100 to 250°) 2. Excellent resistant to oxygen, ozone 7 sunlight. 3. Flexibility, electrical insulations, low toxicity, non-stick etc.
Sonepat 245 Rubber: Rubber is found in the watery solution that circulates in several varieties of plants. Rubber can also be produced synthetically. These form part of a broad study covered by rubber technology.
Sonepat 246 Rubber is used in applications where both its mechanical properties and its resistance to chemicals and toxic conditions are desirable. Such applications include automobiles tyres and tubes, air hose for water, steam and air, overshoes, raincoats, floor tiles and mats, protective gloves, hot water bottles, erasers etc.
Sonepat 247 Adhesives: Adhesive materials are those used to join two surfaces. Pressure sensitive adhesives cause adhesion simply by the application of pressure. Glues are widely used as adhesive materials. Glues are obtained from animal gelatins, vegetables and starches.
Sonepat 250 Polymers are substances containing a large number of structural units joined by the same type of linkage. These substances often form into a chain-like structure. Polymers in the natural world have been around since the beginning of time. Starch, cellulose, and rubber all possess polymeric properties. Man-made polymers have been studied since 1832. Today, the polymer industry has grown to be larger than the aluminum, copper and steel industries combined.
Sonepat 251 Today, the polymer industry has grown to be larger than the aluminum, copper and steel industries combined. Polymers already have a range of applications that far exceeds that of any other class of material available to man. Current applications extend from adhesives, coatings, foams, and packaging materials to textile and industrial fibers, composites, electronic devices, biomedical devices, optical devices, and precursors for many newly developed high-tech ceramics.
Sonepat 252 Agriculture and Agribusiness: Polymeric materials are used in and on soil to improve aeration, provide mulch, and promote plant growth and health. Medicine: any biomaterials, especially heart valve replacements and blood vessels, are made of polymers like Dacron, Teflon and polyurethane..
Sonepat 253 Industry : Automobile parts, windshields for fighter planes, pipes, tanks, packing materials, insulation, wood substitutes, adhesives, etc. are all polymer applications used in the industrial market. Plastic containers are light weight and economically less expensive than traditional containers. Clothing, floor coverings, garbage disposal bags, and packaging are other polymer applications. Sports Playground equipment, various balls, golf clubs, swimming pools, and protective helmets are often produced from polymers.