Metals

● Mineral Deposit - concentrated enough to allow economical recovery of desired metal ● Ore - refers to the desired metal ● Gangue - non-economical metal ● Chromite - the main ore mineral of chromium ● Laterite - the resulting soil layer due to weathering, erosion and soil formation typically red in color due to the presence of iron oxides and hydroxides ● Seawater - a rich source of some metal ions such as Na + , Mg 2+ , and Ca 2+ ● Manganese Nodules - found in the vast areas of the ocean floor which are made up of mostly manganese with iron, nickel, copper, and cobalt in a chemically combined state ● Noble Metals - metals that show the least chemical reactivity ● Metallic Bond - a force that hold atoms together in a metallic substance. A type of chemical bond formed between positively charged atoms in which the free electrons are shared among a lattice of cations. ● Delocalized Electron - an electron in an atom, ion, or molecule not associated with any single atom or a single covalent bond ● Sea of Electrons - formed by delocalized electrons that are free to move throughout metals ● Metallurgical Process - the science and technology of separating metals from their ores and compounding alloys\ ● Alloy - a solid solution either of two or more metals or of a metal or metals with one or more nonmetals. ● (1) Preparation of the Ore - the desired mineral is separated from waste materials called gangue ● Flotation - the ore is finely ground and added to water containing oil and detergent to separate mineral particles from gangue ● Ferromagnetic Metals - strongly attracted to magnets ● Amalgam - an alloy of mercury with another metal/s ● Amalgamation - the process of using mercury to dissolve silver and gold in an ore . ● (2) Production of Metals - the production of a free metal is a reduction process since metals in their combined forms always have positive oxidation numbers ● Preliminary Operations - may be necessary to convert the ore to a chemical state more suitable for reduction. ● Metal Oxides - can be reduced more conveniently to yield the pure metals ● Pyrometallurgy - involved in most major metallurgical processes which are procedures carried out at high temperatures ● Electropositive Metal - can be used as a reducing agent to separate a less electropositive metal from its compound ● Electrolytic Reduction - suitable for very electropositive metals such as sodium, magnesium, and aluminum. This process is usually carried out on the anhydrous molten oxide or halide of the metal. ● (3) Purification of Metals - further treatment to remove impurities ● Fractional Distillation - applied to metals with low boiling points such as mercury, magnesium, and zinc to separate them from other metals ● Mond Process - a well-known method of fractional distillation for the purification of nickel ● Electrolysis - more electropositive metals are removed by an electrolysis process in which the impure metal acts as the anode and pure metal acts as the cathode. ● Zone Refining - a metal rod containing a few impurities is drawn through an electrical heating coil that melts the metal ● Iron Ore - contains from 50% to 70% iron depending on grade ● Hematite - almost 70% iron ● Coke - supplies heat for chemical reactions and produces carbon monoxide to reduce iron ore ● Limestone - used as a flux to react with and remove impurities in molten iron ● Hot Gases - used to burn coke ● Slag - a mixture of calcium silicate and calcium aluminate that remains molten at the furnace temperature ● Blast Furnace Process - a refractory-lined chamber with a diameter of about 9 to 11 m at its widest and a height of 40 m ● Pig Iron - product if blast furnace that contains over 4% C plus other impurities ● Steel - an alloy of iron containing 0.02% and 2.11% carbon by weight. It often includes other alloying elements: Mn, Cr, Ni, and Mo. ● Casting of Ingots - molds made of high carbon iron, tapered at top or bottom for removal of solid casting. The mold is placed on a platform called a stool for solidification. ● Continuous Casting - reduces solidification time by an order of magnitude. Steel is poured into the tundish and flows into a water-cooled continuous mold; it solidifies as it travels down in the mold. ● Cupola - a furnace used for converting pig iron into gray cast iron ● Cast Iron - obtained by melting the mixture of pig iron, scrap iron, and coke by a hot air blast. It has around 3% of carbon content. ● Basic Oxygen Furnace - uses pure exygen where air is blown up through the molten pig iron to burn off impurities ● Plain Carbon Steels - carbon is the principal alloying elements; strength increases with carbon content, bit ductility is reduced. ● Low Carbon Steels - contain less than 0.20% C, used in automobile sheet-metal parts, plate steel for fabrication, and railroad rails ● Medium Carbon Steels - range between 0.20% and 0.50% C, used in machinery components and engine parts ● High Carbon Steels - contain carbon in amounts greater than 0.50%, used in springs, cutting tools, and wear-resistant parts ● Low Alloy Steels - iron-carbon alloys that contain additional alloying elements in amounts totalling less than 5% weight; mechanical properties superior to plain carbon steels ● Stainless Steels - highly alloyed steels, typically with Cr and/or Ni, designed for corrosion resistance ● Precipitation Hardening Stainless - typical composition is 17% Cr and 7% Ni, with additional small amounts of alloying elements ● Duplex Stainless - a mixture of austenite and ferrite in roughly equal amounts ● Tool Steels - highly alloyed steeld designed for use as industrial cutting tools, dies, and molds. They must possess high strength, hardness, hot hardness, wear resistance, and toughness under impact. ● Band Theory of Electrical Conductivity - states that delocalized electrons move freely through “bands” formed by overlapping molecular orbitals ● Conduction Band - set of closely spaced empty energy levels ● Electronegativity - a measure of the ability of an atom to attract electrons when the atom is part of a compound. (Increases from left to right and from bottom to top) ● Metallic Property - how readily an atom can lose an electron (decreases from left to right and from bottom to top) ● Atomic Radius - the distance between the nuclei of two identical atoms bonded together (increases from right to left and top to bottom) ● Electron Affinity - the degree to which an atom or molecule attracts additional electrons; the minimum energy required to remove an electron from a negative ion (increases from left to right and from bottom to top) ● Metallic Luster - the property of metals that makes it shiny ● Silver - reflects about 90% of light falling on it ● Hardness - ability to resist denting from impact ● Malleability - ability of metals to be hammered in to thin sheets ● Gold and Silver - the most malleable metals ● Ductility - ability to be drawn into thin wires ● Electrical Conductivity - ability to conduct electricity ● Water reactivity - most metals reacting with water produce hydroxide ● Acid Reactivity - most metals react with acids to produce salts and hydrogen ● Metal Displacement Reactions - metals displace other metals in metallic compound when they have higher reactivity ● Corrosion - the deterioration of metals by an electrochemical process like rusting of iron and tarnishing of silver ● Platina - a greenish substance formed by copper which is copper carbonate ● Passivation - the surface of the iron metal is made inactive by treating it with a strong oxidizing agent such as nitric acid to form a thin oxide layer at the surface ● Alloys - combining the metal with other metals to reduce its tendency to oxidize ● Plating - applying a thin layer of other metals like tin or zinc on the surface of iron ● Cathodic Protection - a process in which metal that is to be protected from corrosion is made into the cathode in what amounts to a galvanic cell ● Designation Scheme for Steels - specified by a 4-digit number system YYXX, the first two numbers YY represent the alloying elements and the last two numbers XX represent the carbon % in hundredths of percentage points ● Stainless Steel - three-digit AISI numbering scheme; first digit indicates the general type and the last two digits give a specific grade within type ● Nonferrous Metals - metal elements and alloys not based on iron ● Alkali Metals - the most electropositive elements that have a body-centered crystal structure with low packing efficiency ● Lithium - the lightest known metal ● Alkaline Earth Metals - second most reactive metals in the periodic table and have increasing reactivity in the higher periods ● Aluminum - high electrical and thermal conductivity, corrosion resistance, and light ● Copper - low electrical resistivity ● Bronze - copper and tin ● Brass - copper and zinc ● Beryllium-Copper - the highest strength alloy of copper ● Galvanized Steel - steel coated with zinc ● Tungsten - highest melting point among metals and one of the densest , also the stiffest and hardest of all pure metals ● Superalloys - high-performance alloys designated to meet demanding requirements for strength and resistance to surface degradation at high service temperatures ● Iron-Based Alloys - in some cases, iron is less than 50% of total composition ● Nickel-Based Alloys - better high temperature strength than alloy steels ● Cobalt-Based Alloys - 40% Co and 20% Cr ● Heat Treating - performed to enhance properties ● Finishing Processes - commonly used to improve the appearance of metal parts and/or to provide corrosion protection ● Alloying - an important technique to strengthen metals ● Cold Working - strain hardening during deformation to increase strength. ● Heat Treatment - heating and cooling cycles performed on metal to beneficially change its mechanical properties ● Normalizing - the materials is heated between 750-980 degrees Celcius then cooled at a room temperature; product: high strength and high ductility, tougher than annealed steal ● Annealing - heating above critical temperature then controlled cooling inside furnace ● Quenching - heating then rapid cooling in water or oil for hardening steel ● Tempering - reheating below critical temperature, holding the temperature for a specific period, then slowly cooling in still air