Metals and Metallurgical Principles.pptx

Metals and Metallurgical Principles

1. Metals and Metallurgical Principles ORE METAL MATERIALS

2. A n element is a chemical substance that cannot be broken down into other substances by chemical reactions. The basic particle that constitutes a chemical element is the  atom. Elements are identified by the number of protons in their nucleus, known as the element's atomic number. Elements are classified on three categories: Metals, Non-metals and Metalloids. Metals are elements that are generally hard, shiny, malleable, ductile, and fusible, with high electrical and thermal conductivity, commonly used in a wide range of industrial and everyday applications due to their versatile properties. Eg . Iron, copper, gold, silver ,etc. Metals and Metallurgical Principles INTRODUCTION

3. Non-metals are elements characterized by their lack of metallic properties, typically being poor conductors of heat and electricity, and often found as gases, liquids, or brittle solids, playing key roles in various chemical processes and biological systems. Eg . Oxygen. Hydrogen, carbon, etc. Metalloids are elements that have properties intermediate between metals and non-metals, often being semiconductors and found in applications such as electronics and alloys due to their unique ability to conduct electricity better than non-metals but not as well as metals. Metalloids are also called semi-metals as they are poor conductors of heat and electricity. Eg . Arsenic, bismuth, beryllium, etc. Metals and Metallurgical Principles Introduction (Contd.....)

4. The process of extracting a metal from its ore and refining it, is called metallurgical process or simply as metallurgy . The actual process of extraction of a metal from its ore depends upon the nature of the ore and the metal. There is no universally operational method for the extraction of metals. Certain common steps however, are involved in all metallurgical processes . Metallurgy comprises of 3 steps: Concentration of Ore Isolation of metal from the concentrated Ore Purification of the metal Metals and Metallurgical Principles METALLURGY

5. Metals and Metallurgical Principles Some of the types of Metallurgical processes are as follows: Pyrometallurgy ( pryo means heat): Pyrometallurgy is a branch of metallurgy that involves the extraction and purification of metals through high-temperature processes. It involves heating ores to separate the metal from other materials through chemical reactions. This method typically includes steps such as roasting, smelting, and refining to separate metals from their ores. b. Electrometallurgy : Electrometallurgy is the method of extraction of metals from the pre by electrolytic reduction in molten state or in aqueous solution. Electrowinning is a process that extracts metal from a solution by using an electric current to deposit the metal onto an electrode. It is commonly used to recover metals like gold, silver, and copper.Generally applied for alkali and alkaline earth metals.

6. Metals and Metallurgical Principles c. Hydrometallurgy: Hydrometallurgy is the method of extraction of metals from the ore by dissolving the ore with suitable reagent and subsequent precipitation of the metal by other active electropositive metals. This method is used for the extraction of Ag, Au from their ores which are less reactive. For example, silver ore is leached with a dilute solution of sodium cyanide. Silver ore is dissolved forming a complex (Sodium argentocyanide ). The solution is further treated with zinc to get the precipitate of silver. Ag 2 S + 4NaCN 2Na[Ag(CN) 2 ] +Na 2 S sodium argentocyandide 2Na[Ag(CN) 2 ] + Zn Na 2 [Zn(CN) 4 ] +2Ag sodium tetracyanozincate

7. Metals and Metallurgical Principles Minerals: Minerals are naturally occurring, inorganic solid substances with a specific chemical composition and crystalline structure. They are the building blocks of rocks and can have various properties such as color , hardness, and luster . All the Minerals are ores but all ores are not minerals. For eg . Clay contains aluminium but it is not an ore of aluminium.the process of taking out a minerals from mine is called mining. Ores: Ores are naturally occurring rocks or sediments from which valuable minerals or metals can be extracted profitably. They contain high concentrations of specific minerals or metals and are mined for industrial use, such as copper, gold, and iron ores. All minerals are not suitable for extractions of metals due to: Minerals may not be deposited in a large area. Metal may be present in low percentage by composition in the given mineral Impurities present in the minerals may not be easily removed and extraction of metal may be difficult.

8. Metals and Metallurgical Principles State of Minerals: Native state: Elements in their native state are found in nature in their pure, un combined form. Examples include gold, silver, and platinum, which are often found as native metals due to their low reactivity and ability to occur in their metallic form. These generally have alluvial impurities like sand, clay, etc. Combined state: Elements in their combined state are found as part of compounds or minerals. Most elements are found in this form, bonded with other elements. For instance, iron is commonly found in compounds such as hematite ( Fe₂O ₃) and magnetite ( Fe₃O ₄), and oxygen is found in water (H₂O) and various minerals. Complex ores are those ores containing two or more metals, as lead zinc whereas Simple ores contain only one metal.

9. Metals and Metallurgical Principles Some common ores found in Nepal Mineral Location Nickel Bamangaun ( Dadeldhura ), Beringkhola ( Ilam ), Bauligad ( Bajhang ) Khoprekhani ( Sindhuli ) Bismuth Dadeldhura and Baraghare and Mandukhola area in Makawanpur district Tungsten Dadeldhura and Makwanpur Iron Dhaubadi ( Nawalpur ),  Lalitpur  ( Phulchoki ), Thoshe ( Ramechhap ), Labdhikhola ( Tanahu ), Jirbang ( Chitwan ) , and Dhuwakot ( Parbat ) Silver Ganesh Himal ( Rasuwa ), Barghare ( Makawanpur ),Bering Khola ( Ilam ) Zinc Ganesh Himal area ( Rasuwa ), Phakuwa ( Sankhuwashbha ), Libangkhairang , Damar , and Baraghare ( Makawanpur ), Pangum ( Solukhumbu ) , Salimar valley ( Mugu / Humla ), Phulchoki ( Lalitpur ), Sishakhani and Khandebas ( Baglung ), Duwakot (Parbat) Bhalu Danda ( Dhading ), Kholakhani ( Taplejung ) Copper Gyazi ( Gorkha ), Okharbot ( Myagdi ) and Wapsa ( Solukhumbu ) Cinabar Khimti River Gold Mahakali , Chamaliya , Jamari gad, Seti , Karnali , Bheri , Rapti , Lungrikhola and Phagumkhola ( Rolpa ), Kaligandaki , Myagdikhola , Modi, Madi , Marsyandi , Trishuli , Bhudhi Gandaki , and Sunkoshi Tin Meddi and Genera ( Dadeldhura ) and Mandhukhola area ( Makawanpur ) Cobalt Netadarling and Tamghas ( Gulmi ) and Samarbhamar ( Arghakhanchi )

10. Metals and Metallurgical Principles Gangue or Matrix, Flux and Slag Gangue refers to the worthless minerals or materials in an ore deposit that are separated from the valuable minerals during the extraction process. Flux is a substance added during the smelting or refining process to facilitate the removal of impurities and to help the formation of slag. Flux + Matrix Slag The types of flux are: a. Acidic Flux: Contains substances like silica or alumina that react with basic impurities to form a slag. It is used in processes such as the extraction of iron from its ore. b. Basic Flux: Contains substances like lime (calcium oxide) that react with acidic impurities to form a slag. It is commonly used in processes like steelmaking.

11. c. Neutral Flux: Does not significantly alter the acidity or basicity of the slag and is used to maintain the desired properties of the molten metal. Examples include borax and certain fluorides. d . Reducing Flux: Contains substances that remove oxygen from the metal ore or slag, helping to prevent oxidation. It is used in processes where oxidation needs to be controlled. Slag is a by product of metal smelting that consists of the non-metallic residue left after the extraction of the desired metal from ore . Metals and Metallurgical Principles Types of flux.( contd …)

12. Metals and Metallurgical Principles Alloy Alloy is a metal made by combining two or more elements, typically metals, to achieve desirable properties such as increased strength, hardness, or resistance to corrosion. Examples include stainless steel (iron, chromium, and nickel) and aluminum alloys ( aluminum with elements like copper or magnesium). Alloys’ chemical properties remain the same as component elements whereas physical properties changes.

13. Metals and Metallurgical Principles Some important Alloys, composition and their usages

14. Classification of Alloys Based on Metal Content(Iron): a. Ferrous Alloys: Alloys containing iron as the primary metal or major metal are called Ferrous Alloys. Example: Steel (iron and carbon), Cast Iron (iron, carbon, and silicon). b. Non-Ferrous Alloys: Alloys do not containing iron as the primary metal. Example: Bronze (copper and tin), Brass (copper and zinc). Uses of Alloying: Enhanced Strength: Alloying improves the mechanical strength and hardness of metals, making them suitable for structural applications. Example: High-Strength Low-Alloy (HSLA) Steel is used in construction and automotive industries due to its superior strength. Improved Corrosion Resistance: Alloying can increase a metal's resistance to corrosion and oxidation, extending its lifespan and reducing maintenance. Example: Stainless Steel , with chromium added, is used in kitchen utensils and medical instruments due to its resistance to rust and corrosion. Metals and Metallurgical Principles

15. Uses of Alloying: Better Wear Resistance: Alloys can be designed to withstand wear and abrasion, making them ideal for high-friction environments. Example: Bronze is used in bearings and bushings because of its durability and resistance to wear. Enhanced Conductivity: Alloying can modify a metal's electrical or thermal conductivity to suit specific applications. Example: Brass , with its improved electrical conductivity, is used in electrical connectors and terminals. Improved Ductility and Malleability: Alloying can enhance a metal's ability to be shaped or deformed without breaking. Example: Aluminum Alloys , such as those used in aerospace, offer good ductility and are lightweight, making them suitable for aircraft components. Temperature Stability: Some alloys are designed to retain their properties at high or low temperatures. Example: Inconel alloys, used in jet engines and industrial reactors, maintain strength and resist oxidation at high temperatures. Metals and Metallurgical Principles

16. Specific Functional Properties of Alloying: Alloying can impart unique properties required for specialized applications. Example: Amalgams , such as those used in dental fillings, combine mercury with other metals for their specific hardness and malleability Metals and Metallurgical Principles Amalgams: Amalgams are alloys that include mercury combined with another metal or metals. They have been used for various purposes ,one of the most notable uses being dental amalgams for filling cavities. some examples are Sodium-Amalgams (Na-Hg) b. Silver-Amalgams (Ag-Hg ) Zinc-Amalgams(Zn-Hg ) d. Copper-Amalgams (Cu-Hg) Almost all metals form amalgam with mercury except some metals like iron, platinum, tungsten and tantalum. Dental amalgams are typically made from a mixture of mercury (about 50%) and a powdered alloy composed of silver, tin, and copper. Other metals like zinc, indium, or palladium can also be included .

17. Properties: Amalgams are known for their durability, strength, and ability to withstand the forces of chewing. They have good compressive strength and are relatively easy to manipulate and shape. Some Uses are: Dental Amalgams: Used for over a century, these fillings are known for their longevity and effectiveness in restoring teeth. They are particularly useful in posterior teeth (molars) where chewing forces are greatest. Industrial Applications: Amalgams are used in the extraction of gold and silver from ore. Mercury amalgamates with these metals, making it easier to separate them from other materials. Metals and Metallurgical Principles Amalgams:

18. Metals and Metallurgical Principles a. Crushing and Pulverization : Crushing : The process of reducing large chunks of materials into smaller pieces using mechanical forces, typically involving crushers . Process: Feeding: Large materials, such as rocks or ores, are fed into the crusher. Crushing: The crusher applies compressive forces to break the materials into smaller pieces. Output: The resulting smaller pieces are then ready for further processing or use . Pulverization : The process of grinding materials into fine powders or dust using mechanical forces, typically involving mills. Process: Feeding : Smaller pieces of material from the crushing process are fed into the mill. Grinding : The mill applies mechanical forces such as impact, compression, and attrition to grind the material into fine powders. Output : The resulting fine powders are then ready for further use or chemical processing . General Principles of the extraction of Metals

19. Metals and Metallurgical Principles General Principles of the extraction of Metals b. Concentration: Removing unwanted materials, such as sand and clay, from ore is referred to as concentration, dressing, or benefaction. This process involves multiple steps, which are chosen based on the differences in physical properties between the metal compounds and the gangue (waste materials). The choice of methods also depends on factors like the type of metal, available technology, and environmental considerations. Here are some key procedures used in this process . Gravity Separation: The process of separating ore from gangue based on their differing gravities is known as gravity separation. This method involves washing powdered ore with an upward stream of running water, which carries away the lighter gangue particles while leaving the heavier ore particles behind. The lighter gangue, being less dense, is washed out and discarded, while the denser ore particles remain, allowing for the concentration of the desired material. This technique is valued for its simplicity and environmentally friendly nature, as it primarily uses water for separation, though its effectiveness depends on the significant difference in density between the ore and gangue, and it requires considerable water resources.

20. Metals and Metallurgical Principles General Principles of the extraction of Metals Powdered

21. Metals and Metallurgical Principles General Principles of the extraction of Metals b. Magnetic Seperation : This method uses differences in magnetic properties to separate ore from gangue. If either the ore or the waste material can be attracted by a magnet, magnetic separation is used. For example, this is done with iron ores. The crushed ore is moved on a conveyor belt that passes over a magnetic roller, which pulls out the magnetic particles and separates them from the non-magnetic ones . Magnetic separation is used to extract metals that exhibit magnetic properties. This technique is commonly employed to separate iron from its ores, such as magnetite, due to its strong magnetic nature. It is also utilized for chromium ores like chromite and tantalum ores containing tantalite.

22. Metals and Metallurgical Principles General Principles of the extraction of Metals c. Froth Floatation Method: This method is used to remove gangue from sulfide ores. The process starts by creating a suspension of powdered ore mixed with water, to which collectors and froth stabilizers are added. Collectors, such as pine oils, fatty acids, or xanthates, make the mineral particles less likely to wet with water, while froth stabilizers like cresols or aniline help maintain the froth. The oils make the mineral particles wet, whereas the gangue particles remain wet with water.

23. A rotating paddle agitates the mixture and introduces air, creating froth that carries the mineral particles. This froth is then skimmed off, dried, and the ore particles are recovered. In some cases, two sulfide ores can be separated by adjusting the oil-to-water ratio or using depressants. For example, sodium cyanide ( NaCN ) can be used as a depressant to prevent zinc sulfide ( ZnS ) from rising with the froth while allowing lead sulfide ( PbS ) to be collected in the froth.

24. Metals and Metallurgical Principles General Principles of the extraction of Metals d. Leaching : Leaching is a chemical process that extracts valuable metals or minerals from ores by dissolving them in a solvent. The material is prepared, mixed with a solvent that dissolves the desired components, and then the solution is separated from the residue or precipitate to recover the metals. This method is used in mining, environmental clean up , and agriculture but requires careful handling of potentially toxic solvents to manage environmental and health risks . For Eg . Bauxite(Al 2 O 3 .2H 2 O) ore is concentrated by leaching it with a 45% caustic soda solution and forms soluble sodium meta aluminate. It is also given by Baeyers m ethod. Al 2 O 3 .2H 2 O + 2NaOH 2NaAlO 2 + 3H 2 O This solution is filtered to remove insoluble impurities like silica and other oxides. The filtrate is diluted with water and agitated for several hours to get precipitate of aluminium hydroxide. NaAlO 2 + 2H 2 O Al(OH) 3 + NaOH The precipitate is seperated and ignited to get Al 2 O 3 .

25. Metals and Metallurgical Principles General Principles of the extraction of Metals c. Conversion of concentrated ores into reducible form: This process involves the conversion of metals ore in to reducible form(Metal Oxide). It is easy to obtain metal from their oxides so this process is carried out. This step can be done by two processes: Calcination: T he concentrated ore obtained is heated strongly in the absence of air or a limited supply of air below its melting point. This process is called Calcination process. This process is suitable for only oxide or hydroxide or carbonate ores. b. Roasting: It is the process in which the concentrated ore obtained is heated strongly in the presence of air or a limited supply of air below its melting point. This process is only suitable for sulphide ores. The changes during this processes are: It removes volatile impurities like CO 2 , SO 2 , moisture, etc. It directly removes water. The ore becomes porous and easy to handle in succeeding steps . These processes are done in a special type of vessel known as reverberatory furnace. In some conditions Calcination is carried out in an open-hearth furnace, shaft furnace, blast furnace, etc.

26. Metals and Metallurgical Principles General Principles of the extraction of Metals

27. c. Conversion of concentrated ores into Metal form: Reduction process is used for converting metal – oxides into metal . Reduction of the metal oxide usually involves heating it with some other substance acting as a reducing agent (C or H 2 or Al or CO or even another metal). The reduction reaction chosen depends on the chemical reaction or reactivity of metals. Generally reduction by heat, chemical reduction or electrolytic reduction processes are utilized. Carbon Reduction (Smelting): In this process the reducing agent (e.g., carbon) combines with the oxygen of the metal oxide. Oxides of Zn, Fe, Ni, Sn, Pb are reduced by heating them with carbon. Metal – oxide is mixed with coke, a source of carbon, and heated in a furnace . The heating process is carried above the melting point of the metal. Carbon reacts with oxygen and free metal is obtained. Metals and Metallurgical Principles General Principles of the extraction of Metals

28. Carbon Reduction (Smelting )( Contd …) Some metal oxides get reduced easily while others are very difficult to be reduced (reduction means electron gain or electronation ). In any case, heating is required. To understand the variation in the temperature requirement for thermal reductions ( pyrometallurgy ) and to predict which element will suit as the reducing agent for a given metal oxide ( MxOy ), Gibbs energy interpretations are made. Metals and Metallurgical Principles General Principles of the extraction of Metals Reduction in Blast Furnace

29. Metals and Metallurgical Principles General Principles of the extraction of Metals ii. Reduction by Al: This process is called the Thermite process. Al is more reactive than carbon. Some metal – oxides that cannot be reduced by coke are reduced by Al. Al itself attracts oxygen from the metal – oxide and becomes aluminum oxide and this frees the metal. Mn (Manganese), Sn(Tin) and Cr(Chromium) metal oxides are extracted and reduced by Al.

30. The mixture of roasted or calcined ore and aluminium is called thermite is mixed with barium peroxide and suitable flux in a crucible. Burning Magnesium is introduced to crucible for ignition, large amount of energy is released. Metallic oxide is reduced to metal in molten form and collected in bottom. Metals and Metallurgical Principles General Principles of the extraction of Metals

31. Metals and Metallurgical Principles General Principles of the extraction of Metals iii. Reduction by electrolysis : Some consideration for this process are: a. Reactivity of the Metal : Choose electrolytes and conditions to prevent re-oxidation and side reactions based on metal reactivity. b. Electrodes : Select inert, conductive materials like graphite, platinum, or coated metals to avoid degradation and participation in the reaction. c. Addition of Flux : Use fluxes to enhance conductivity, remove impurities, and ensure smooth deposition of the reduced metal for higher purity and quality . Highly reactive metal – oxides and metal – chlorides are not easy to be reduced by chemical reactions. Metals such as Na, K, Mn , Ca have to be freed from their ores by electrolytic processes. These metals are so reactive that they themselves are powerful reducing agents. Molten metal – oxides or chlorides form the electrolyte in an electrochemical cell. The cathode of the cell provides the electrons needed for the metal to free itself from the metal – oxide or metal – chloride bonds. In the electrolysis, metals atoms get deposited on the cathode electrodes, which then have to carefully removed and stored.

32. iii. Reduction by heat (Self Reduction): Metals that are unreactive, like Hg, can be reduced from their ores by heating them. Mercury ore cinnabar is actually mercury sulphide. This can be heated at 300°C so that S is removed as SO 2  and HgO is obtained. Hg is a very unreactive metal. HgO dissociates into Hg and oxygen soon. Metals and Metallurgical Principles General Principles of the extraction of Metals

33. c. Refining : A metal extracted by any method is usually contaminated with some impurity like trace amount of others metals, unreduced oxides, residual slag or flux and non-metals like carbon, silicon, etc. For obtaining metals of high purity, several techniques are used depending upon the differences in properties of the metal and the impurity. Some of them are listed below. Distillation ( b) Liquation ( c) Electrolytic refining ( d) Zone refining (e ) Poling ( f) Oxidation a. Distillation: This is very useful for low boiling metals like zinc and mercury. The impure metal is evaporated to obtain the pure metal as distillate . Distillation purifies metals by heating them until they vaporize, separating them from impurities with higher boiling points that remain in the furnace. The metal vapor is then directed into a cooler area where it condenses back into a liquid or solid form, which is collected as the purified metal. Impurities are left behind in the distillation apparatus, and the process can be repeated to achieve higher purity levels. This method is especially effective for metals with significantly different boiling points from their impurities, such as zinc, mercury, and cadmium . Metals and Metallurgical Principles General Principles of the extraction of Metals

34. (b) Liquation: In this method, a low melting metal like tin can be made to flow on a sloping surface. In this way it is separated from higher melting impurities. This method is used when the metal to be extracted has lower melting point than the impurties or gangue . Metals and Metallurgical Principles General Principles of the extraction of Metals In this method: The crude or impure metal obtained after extraction process is placed on the sloping hearth of a reverberatory furnace and heated in the absence of air slightly above the melting point of the metal. Metal melts and flows away leaving non-fusible impurities (oxides) behind. This method is employed for low melting metals like Bi, Sn, Pb , Hg.

35. ( c) Electrolytic refining: In this method, the impure metal is made to act as anode. A strip of the same metal in pure form is used as cathode. They are put in a suitable electrolytic bath containing soluble salt of the same metal. The more basic metal remains in the solution and the less basic ones go to the anode mud. This process is also explained using the concept of electrode potential, over potential, and Gibbs energy which you have seen in previous sections. Metals and Metallurgical Principles General Principles of the extraction of Metals

36. Metals and Metallurgical Principles General Principles of the extraction of Metals As shown in the figure above :The reactions involved are : Anode: M → M n + + ne– Cathode: M n + + ne– → M Eg . Copper is refined using an electrolytic method. Anodes are of impure copper and pure copper strips are taken as cathode. The electrolyte is acidified solution of copper sulphate and the net result of electrolysis is the transfer of copper in pure form from the anode to the cathode: Anode: Cu → Cu 2+ + 2 e– Cathode: Cu 2+ + 2e– → Cu Impurities from the blister copper deposit as anode mud which contains antimony, selenium , tellurium, silver, gold and platinum; recovery of these elements may meet the cost of refining. Zinc may also be refined this way.

37. Metals and Metallurgical Principles General Principles of the extraction of Metals (d) Zone refining : This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. A circular mobile heater is fixed at one end of a rod of the impure metal. The molten zone moves along with the heater which is moved forward. As the heater moves forward, the pure metal crystallises out of the melt and the impurities pass on into the adjacent molten zone. The process is repeated several times and the heater is moved in the same direction. At one end, impurities get concentrated. This end is cut off. This method is very useful for producing semiconductor and other metals of very high purity, e.g., germanium, silicon, boron, gallium and indium.

38. Metals and Metallurgical Principles General Principles of the extraction of Metals Poling: Poling is a method used to purify metals that have oxidized impurities. It is typically used to purify metals like copper or tin that are in the impure form of a copper oxide or tin oxide. A log of wood which is still green is used to stir the liquid metal.

39. THANK YOU