S E S POLYTECHNIC SOLAPUR By Prof M

S. E. S. POLYTECHNIC SOLAPUR By- Prof. M. S. KHED

Metals and Alloys Hardness: Hardness is the ability of the metal to resist wear or abrasion and penetration. Ductility: It is the property of the metal by which it can be stretched in length without breaking. Malleability: It is the property by which a metal can be hammered into shapes without cracking and rolled in to sheets: Toughness: The property of metal to resist repeated shocks or vibrations. Brittleness: It is the property of a metal which does not permit permanent deformation without breakage. Tenacity: Tenacity of a metal is measured by weight which its wire can support. Tensile strength: It is the ability to carry the load without breaking.

Weldability: It is the process of uniting two pieces of metal by means of heat, by bringing their ends together in the molten state. Mechinability: It is property due to which a material can be easily cut by cutting tools to produce a desired shape and surface finish on its surface. Casting: The process of pouring molten metal into mould and allowing it to solidify is known as casting. Forging: The process of giving predetermined shape to piece of metal at sufficiently high temperature when metal is in the plastic state is known as forging. Extrusion: The process by which a piece of metal is reduced in cross section by forcing it to flow through a die orifice under high pressure is known as extrusion process. Brazing: A method of joining metal surfaces by introducing molten non ferrous alloy with melting point above 400 oc between them. Soldering: : A method of joining metal surfaces by introducing molten non ferrous alloy with melting point below 400 oc between them.

Metals are one of the two major classifications of elements (non-metals being the other). v v Almost all metals are found in the combined state as compounds on the crust of the earth. This is due to their high reactivity. v However, there are few exceptions. Such as gold, silver, copper, platinum and bismuth, which are found in the free state, due to their low reactivity. v Aluminium is the most abundant metal in the earth's crust, followed by iron and calcium.

Types of Ores occur in the form of compounds. These compounds are generally oxides, sulphides, carbonates or halides. Classification of ores Type of ore Metals Compound (in the ore) Oxide Ores Aluminium Bauxite - Al 2 O 3, 2 H 2 O Copper Cuprite - Cu 2 O Iron Haematite - Fe 2 O 3 Magnetite - Fe 3 O 4 Sulphide Ores Iron Pyrite - Fe. S Copper Glance - Cu 2 S Copper Pyrites - Cu. Fe. S 2 Carbonate Ores Halide Ores Zinc Blende - Zn. S Calcium Limestone - Ca. CO 3 Zinc Calamine - Zn. CO 3 Sodium Rock Salt - Na. Cl Calcium Fluorspar - Ca. F 2

Extraction of Metals - Metallurgy The compounds of various metals found in nature as ores are mixed with impurities like sand rock. The various processes involved in the extraction of metals from their ores and their subsequent refining are known as metallurgy. An overview of various processes involved during metallurgy is given below.

Ø Steps involved in extraction of metal form its ores Crushing: a)The ores obtained from the mines is in the form of big lumps. b) These lumps are crushed into suitable size particles. Concentration Of ores The process of removal of gangue or matrix form the ore is known as concentration.

Metallurgy : The various processes involved in the extraction of metals from their ores econoimically and profitably are known as metallurgy. Ores Those minerals from which the metals can be extracted profitably are called ores. Gangue or Matrix The rocky impurities, including silica and earthly particles, present in an ore are called gangue or matrix. Minerals The natural materials in which the metals or their compounds occur in the earth are called minerals.

Main process Sub-process 1. Concentration of the ore (removal of a. unwanted metals and gangue to purify the b. ore). c. d. e. 2. Conversion into metal oxide. 3. Reduction of metal oxide to 4. Refining of impure metal. into pure metals. Hydraulic washing. Gravity separation. Froth floatation. Magnetic separation. Chemical separation. a. Calcination for carbonate ore. b. Roasting for sulphide ore. a. Roasting - mercury (Hg) is produced by roasting Cinnabar (Hg. S) in air. b. Reduction - using highly reactive elements. Example: aluminium reduces manganese dioxide to manganese. c. Electrolytic reduction - highly reactive elements, such as sodium and mercury, are obtained by electrolytic reduction when the metal is deposited at cathode. a. Electrolytic refining - of copper, gold, tin, lead, chromium, nickel, etc. b. Liquation process - for tin, lead and bismuth. c. Distillation process - for zinc, mercury. d. Oxidation process - for iron.

Concentration of the ore 1. Hydraulic washing process (Gravity separation) This process separates the heavier ore particles from the lighter gangue particles. This is done by washing them in a stream (jet) of water over a vibrating, sloped table with grooves. Denser ore particles settle in grooves. Lighter gangue particles are washed away. Hydraulic Washing (Gravity Separation

2. Froth floatation process : In this process, separation of the ore and gangue particles is done by preferential wetting. This process is generally used for sulphide ores of copper, lead and zinc. The finely powdered ore is mixed with water and a suitable oil in a large tank. A current of compressed air agitates the mixture. The ore particles are wetted by oil and forms a froth at the top, which is removed. The gangue particles wetted by water settle down. Ore preferentially wetted by oil is removed as froth. Gangue wetted by water is removed after it settles down. Froth Floatation

3. Magnetic separation process This process is used in the extraction of metals which exhibit magnetic properties. For example, in the extraction of iron, crushed magnetite ore (iron) particles are separated using their magnetic property. The pulverized ore is moved on a conveyor belt. Electro-magnetic wheel of the conveyor attracts only the magnetic particles into a separate heap. Eg. Tinstone contain magnetic impurities. Only the magnetic particles are attracted by the magnetic wheel. These particles fall separately into a different heap as shown in the diagram. Magnetic Separation

There are three practice questions below this that you need to answer after watching the video. 1. Process of separating metal from ore is called magnetic separation I. floatation process II. metallurgy III. cyclone separation 2. Naturally occurring metallic compounds are called I. metalloids II. minerals III. hard solids IV. soft solids 3. In magnetic separation, magnets are used to separate mineral and gangue I. metal and mineral II. metal and gangue III. iron and steel