1 Metals-Ferrous and Non Ferrous By Engr. Dr. Attaullah Shah Ferrous Metals. Ferrous is an adjective used to indicate the presence of iron. The word is derived from the Latin word ferrum "iron"). Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel). The term non-ferrous is used to indicate metals other than iron and alloys that do not contain an appreciable amount of iron All forms of iron and steel / manufactured to meet wide variety of specification Chemical composition & internal structure is highly controlled during manufacturing. Good strength and hard. Fabricated in shops to desired size & shape Good quality control during manufacturing Brief History: Iron age (12 th century BC) (mostly wrought iron) weapons made with inefficient smelting methods. The best weapons? When iron combined with carbon! Became more common after more efficient production methods were devised in the 17th century. With invention of the Bessemer process in the mid-19th century, steel became a relatively inexpensive mass-produced good IRON Basic constituent of steel. Most abundant metallic in the earths crust after aluminum Found in the form of ores as oxides, carbonates, silicates & sulfides Produced in blast furnaces. It can be produced into 3 commercial forms that is: a) wrought iron b) steel c) cast iron Increase in the amount of carbon decreases the melting point of the metal. Carbon exerts the most significant effects on the microstructure and properties of iron products. Iron Ores Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3). Hematite is also known as "natural ore", a name which refers to the early years of mining, when certain hematite ores containing up to 66% iron could be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. 98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil. Pig Iron Pig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel. Pig iron has a very high carbon content, typically 3.54.5%, which makes it very brittle and not useful directly as a material except for limited applications. The Chinese were making pig iron by the later Zhou Dynasty (1122256 BC). An ingot is a material, usually metal, that is cast into a shape suitable for further processing. WROUGHT IRON Manufactured by melting & refining iron to a high degree of purity. Then, molten metal is poured into a ladle and mixed with hot slag. The fluxing action of the slag causes a spongy mass to form which is processed by rolling & pressing. It is only iron-bearing material containing slag. Its a low carbon steel (less than 0.1% carbon by weight) containing a small amount of slag, usually less than 3%. It contains small amount of manganese (less than 0.1%) and silicon (0.2%). Its ductility is lower than steel. Its tensile strength is lower. It can be molded easily and has good resistance to corrosion. It is used to make pipes, corrugated sheets, grills, bars, chains and other products. It can be cold worked, forged and welded like steel. Forging is working a metal to predetermined shape by one or more processes such as hammering, pressing and rolling at a temperature above the re-crystallization temperature. Cold working is the process of working at a temperature that doesnt alter the structural changes caused by the work or that is below the re-crystallization temperature. Wrought iron is used extensively where corrosion resistance is needed. Wrought Iron Gate & Wrought Iron Fence Wrought Iron Rack CAST IRON Manufactured by reheating pig iron (in a cupola) and blending it with other material of known composition. Alternate layers of pig iron (with or without scrap steel) and coke are charged into furnace. Limestone is added to flux the ash from the coke. Heat necessary for the smelting is supplied by the combustion of coke and air supplied by the blast. Cupola function to purify iron and produce a more uniform product. When sufficient metal is accumulated at the bottom of the furnace, it is tapped. Composed primarily of iron, carbon and silicon Shaped by being cast in a mold It has the greatest amount of carbon Basically, the amount and form of carbon could affect the strength, hardness, brittleness and stiffness of cast iron. Adding carbon to iron increases its hardness and strength but lowers the ductility. Cast iron has high compressive strength but its tensile strength is low. There are 2 types of cast iron that is: a) Gray Cast Iron b) White Cast Iron Cast Iron Teapot Cast Iron Pots Cast Iron Bench GRAY CAST IRON Gray Cast Iron also known as ordinary ast iron owing to the color of fracture. It contains free carbon (graphite flakes) that makes the metal weak and soft. Contains high carbon content and large numbers of graphite flakes. The flakes gives a gray appearance to a fractured surface most widely used cast iron Have poor ductility Advantages of cast iron are as follows: a) Cheap b) Low melting point c) Fluid easy to cast, especially advantageous into large complex shapes. d) Excellent bearing properties e) Excellent damping properties (ability to absorb noise and vibration) g) Can be heat threatened h) Can be alloyed White Cast Iron White Cast Iron is called in such name due to the fracture surface that has a silvery white metallic color. Carbon is combined chemically with iron in the form of cementite that makes this metal strong, hard and brittle. harder and more resistant to wear from abrasion compared to gray iron. Excellent wear resistance High compressive stress White Cast Iron Daybed Steel Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron. Steel Products Steel alloy consisting mostly of iron with a little carbon (0.2% % by weight) Cast iron = carbon content between 2.1% - 4.0% Iron = iron-carbon alloy with less than 0.005% carbon. Wrought iron contains 1 3% by weight of slag in the form of particles elongated in one direction more rust resistant than steel and welds better The abcs of Steel Making: Raw Material: Carbon in the form of coke Iron ore (Fe 2 O 3 ) Limestone (CaCO 3 ) Air (lots of it!!) The abcs of Steel Making: Coke Solid residue product from the destructive distillation of coal. About 80 to 95% C. Made by heating black coal in small ovens at 300 C for 24 hours in a coke plant. The abcs of Steel Making: The iron ore Consists of oxides in nature of iron and oxygen Primarily magnetite (Fe 3 O 4 ) or hematite (Fe 2 O 3 )magnetitehematite The blast furnace basically separates the iron from the oxygen in a reduction process Mined primarily in Australia, Brazil and Canada. The abcs of Steel Making: The limestone Acts as a flux converts impurities in the ore into a fuse able slag The abcs of Steel Making: Air Preheated by fuel gas from the coke ovens to about 1000 C. Delivered to the blast furnace at 6,000 m 3 /min Passes through furnace and burns the coke to produce heat required and also generates the carbon monoxide. The abcs of Steel Making: Typical blast furnace: 1.6 tons of iron ore 0.18 tons of limestone 0.6 tons of coke 2 -3 tons of preheated air The abcs of Steel Making: Step 1 The Blast Furnace: Stands 300 feet tall Designed to run continuously for 4 -5 years before being relined. Heat generated by burning coke in the preheated air. Coke acts as reducing agent and changes to carbon monoxide (the reducing agent) which removes the oxygen from the iron oxide. The abcs of Steel Making: Step 1 The Blast Furnace: Four primary zones the bottom zone (zone 4) reaches temperature of 1800 C this is where iron is tapped off. The top zone (zone 1) where coke is burned and moisture driven off. Zone 2 slag coagulates and is removed. The abcs of Steel Making: Step 1 The Blast Furnace: Two important chemical reactions: Oxidation of the carbon from coke: Reduction of iron ore: The abcs of Steel Making: Step 1 The Blast Furnace: Products from the blast furnace: Iron stored in steel shelled ladles Pig iron (brittle w/ 4% carbon) Step 2: Manufacturing of Steel from Iron Two common methods: Bessemer Furnace = Ingots = molten steel poured into molds to create ingots which then go through forging press and roughing mill to create billet, bloom or slab, OR: Continuous cast continuous process to again create a billet, bloom, slab or as cast semis Step 2 The Bessemer converter: Used for REFINEMENT: Takes pig iron with high C content and removes C. Removes impurities such as Si and Mn (via oxides) Much smaller furnace (vs. Blast furnace) Lowered cost of steel making Poured into molds to form ingots Replaced by basic oxygen process and electric arc furnace. Steel Ingots Figure 9-12: processing of refined steel into products. F 9-13 The whole spectrum of steel products!