Engineering Materials: Ferrous and Non-ferrous Metals PDF

MODULE 1.1 FERROUS and NON-FERROUS METALS ENGINEERING MATERIALS Engineering Materials are materials of constructions used for the construction of buildings, bridges, highways, fabrications machines...

MODULE 1.1 FERROUS and NON-FERROUS METALS ENGINEERING MATERIALS Engineering Materials are materials of constructions used for the construction of buildings, bridges, highways, fabrications machines, equipments, airplanes, ships, electrical applications, medical applications and others, used commercially for engineering purposes. Examples of are metals, wood or lumber, sand and gravel, cement, concrete products, plastics, rubber, leather, asbestos, mica, asphalt, ceramics, tiles, etc. ENGINEERING MATERIALS ARE CLASSIFIED INTO TWO GROUPS: a. Metallic Materials – are materials that contain metallic elements. They exhibit electrical and thermal conductivity, malleability, ductility and luster. Classification of Metallic Materials Ferrous materials - materials that contain iron as base metal or known as iron base metal. Examples are steels and cast iron. Non-ferrous Materials -are materials that do not contain iron as base metal or known as non-iron base metal. Examples are copper, silver, gold, bronze, brass and lead. b. Non-Metallic Materials are materials that do not recognized metallic characteristics such as plastics, Teflon, wood, rubber, glass, fiber glass, resin and cement, etc. c. Metalloids – materials that possess properties of both metals and non-metals. They have physical appearance of metals and brittle. Examples are boron, silicon, germanium, arsenic, tellurium and antimony. PROPERTIES, CHARACTERISTICS, LIMITATIONS AND APPLICATIONS OF FERROUS METALS 1. Wrought Iron As early as 1855 wrought iron was the most important metallic material for general structural purposes. It is a mechanical mixture of very pure iron and a silicate slag. The slag is distributed throughout the iron- based metal in the form of threads or fibers. Wrought iron is made by puddling process. It is readily worked by forging, bending and drawing. Wrought iron is composed primarily of iron with 1 to 2% of added slag, the byproduct of iron ore smelting, generally a mix of silicon, sulfur, phosphorous, and aluminum oxides. During manufacture, the iron is removed from heat and worked with a hammer while still hot to get it into its intended final form. 1 Engr.AJ Labayen Emat-Prelim  Properties/Characteristics Limitations Applications/Uses 1. Soft and malleable 1. Corrosion of wrought iron occurs 1. Use for making pipes and 2. Possess toughness in different forms such as tubes due to its superior 3. Fatigue resistant general, pitting and stress corrosion and fatigue 4. Other mechanical properties corrosion cracking due to its resistance and better welding and corrosion resistance are fibrous structure. and threading qualities. good depending upon the 2. The material 2. Use for machine parts such orientation of the slag deterioration occurs gradually as rods and shafting. 5. High ductility and can be easily over long periods of time, at 3. Use for making special chains forged and weld. predictable rates, and requires and crane hooks due to its appropriate routine or good weldability and high preventive maintenance to impact strength. control. 2. Steel Forging They are steels that are created through steel forging process. It is an alloy of carbon and iron that is compressed under extreme pressure to make a very hard and strong substance. Moreover, it is formed by the application of thermal and mechanical energy to steel billets or ingots to cause the material to change shape while in a solid state. Properties/Characteristics Limitations Applications/Uses 1. Possess good impact and shear 1. Difficulty to perform secondary 1. Ability to resist corrosion and strength. operations. heat 2. It has tight grain structure 2. Use for flanges, valve bodies making it mechanically strong and stems due to its ability to and wear resistant. withstand high pressure and 3. It offers great response to heat freedom from porosity. treatment. 3. Use for making tee, elbows, 4. The defects such as porosity reducers and other pipe and formation of cavities can fittings expose to high be avoided temperature and pressure. 4. Use for making disc and hubs. 3. Cast Iron Cast iron is an alloy of iron and carbon. In general alloys containing more than 1.7% carbon are referred to as cast iron. Being responsible for approximately 25% of the total engine weight, cast iron ranks second among the materials used in the construction of large diesel engines. Cast iron is made when pig iron is re-melted in small cupola furnaces (similar to the blast furnace in design and operation) and poured into molds to make castings In terms of cost per unit mass, cast iron is the cheapest metallurgical material available to a marine engineer. In fact it is re-melted pig iron, the composition of which has undergone some adjustments during the melting process. 2 Engr.AJ Labayen Emat-Prelim  Properties/Characteristics Limitations Applications/Uses Grey Cast Iron 1. Grey cast iron is widely used for 1. Susceptible to corrosion. 1. Used chiefly for parts that are not general engineering applications, subjected to severe tensile stress, due to its cheapness and ease of such as machine tool beds, large casting. pipes, pump housings, pulleys and 2. Tensile strength is 150 to 400 machine frames. N/mm2. 2. Use for major components of large 3. Brittle and has a compressive engines such as cylinder liners, strength which is three to four cylinder blocks, flywheels, cylinder times than its tensile strength. cover and crankcases. 4. Easily cast to a desired shape and 3. Use as material for propellers easily machined. 5. Resistance to chemicals, water, gas and steam. 6. Good wear resistance Malleable Cast Iron 1. Greater tensile strength, impact 1. Since the malleable cat 1. Use for differential and steering and fatigue strength than grey cast iron are made tough and gear housings, hubs, flanges, iron. machinable by an valve parts for marine, brake 2. Good machinability annealing process, pedals in automobiles therefore it cannot be formed into large section (up to 50 kg) due to limitation in the capacity of heat treatment equipment. 2. Susceptible to corrosion. Spheroidal Graphite / Ductile / Nodular Cast Iron 1. Has the same ductility, strength 1. Susceptible to corrosion. 1. Use for equipment used to and toughness with steel. conduct fluids such as valves and 2. Can be used as substitute for steel, pump bodies. when cast into shaped it can 2. Use for machinery parts which reduced machining cost. require a fair degree of 3. Tensile strength is 370 to 800 toughness with high yield N/mm2. strength such as gears, crankshafts and other automotive and machine components. 3. Use for diesel engines cylinder head and cover. 4. Use as material for propellers Microstructure of Cast Iron a. Grey cast iron b. Malleable cast iron c. Spheroidal graphite cast iron 3 Engr.AJ Labayen Emat-Prelim 4. Steel An alloy of iron and carbon in which the content of carbon does not exceed to 1.7%. Steel is produced from pig iron and/ or scrap iron by several processes with the removal of some carbon and several amounts of sulphur, phosphorus, manganese and silicon. Plain carbon Steel- is a steel which contain only iron and carbon, with some other impurities, while steels containing several elements that were intentionally added are classified as alloy steel. CLASSIFICATION OF PLAIN CARBON STEEL (according to its carbon content) CARBON CONTENT, % CLASSIFICATION 0.05-0.15% Very low-carbon steel 0.15-0.30% Low-carbon steel 0.30-0.60% Medium-carbon steel 0.60-0.90% High-carbon steel 0.90-1.50% Very high-carbon steel Properties/Characteristics Limitations Applications/Uses Low Carbon Steel - also referred as mild steels. If the carbon content is kept between 0.1% and 0.15%, the steel is often referred to as ‘ dead mild ’ steel. 1. Very ductile and very soft, 1. Low in strength and hardness 1. Tubing, pipes, wires, rods, rivets, 2. Can be pressed into 2. Unresponsive to heat treatment screws, case hardened parts. complicated shapes without due to low carbon content cracking. 3. Easily machined using high speed cutting tools Medium Carbon Steel 1. Harder, stronger and tougher 1. Cannot be bent or formed in 1. Shafting, axles, rods, gear, than low carbon steels cold condition since it will result connecting rods, wire for 2. They can be hardened by cracking springs, case-hardened large direct heating and quenching, sections and tempered to improve the 2. Suitable for heat-treated mechanical properties machine parts. 3. Large forgings, heavy duty gears High Carbon steel 1. Harder and less ductile than 1. Unsuitable for cold working 1. Shear blades, band saw, low and medium carbon steel. 2. Difficult to weld hammers, wrenches, cold 2. Easily hardened by heat chisels, pickaxes treatment. 2. Cutting and blanking punches 3. Good shock resistance. and dies, rock drills, hand tools, chisel. 4 Engr.AJ Labayen Emat-Prelim 5. CAST STEEL Cast steel is a ferrous alloy with a maximum carbon content of approximately 0.75%. Steel castings are solid metal objects produced by filling the void within a mold with liquid steel. Mechanical properties for cast steel are generally lower than wrought steels, but with the same chemical composition. Properties/Characteristics Limitations Applications/Uses 1. Can withstand high 1. Lesser abrasion resistance, 1. Use for diesel engines cylinder head and tensile stress and vibration absorption, cover. dynamic load. liquidity and casting 2. Use for diesel engines piston rod. performance compared to cast iron. 2. The toughness of cast steel is severely reduced at low temperatures. 6. ALLOY STEEL ALLOY STEEL is a steel alloyed with other elements in amount of between 1 and 50% by weight to improve its mechanical properties. Alloy steels are classified into two groups; low alloy steel and high alloy steels. Common alloying elements are molybdenum, manganese, nickel, chromium, vanadium, silicon and boron. Most alloy steel is medium- or high-carbon steel to which various elements have been added to modify its properties to an appreciable extent; Properties/Characteristics Limitations Applications/Uses 1. Greater strength, 1. Difficult to machine due to 1. Stainless steel – low carbon steel with hardness, wear its hardness. additions of 4-6% chromium. They are resistance and 2. Usually requires heat commonly used in gas turbine toughness than plain treatment in order to compressor, propeller shaft, gravity disc carbon steel. achieve the enhance and bowl body of purifiers. 2. Hot hardness in which it mechanical properties 2. Nickel steel (forged) – used as a material can retain its hardness for the crankshaft of diesel engine at high temperature. 3. Low alloyed Cr –Mo steel which has tensile strength (590-680) N/mm2 - used as a material for the crankshaft of diesel engine 4. Low alloy steels containing molybdenum and chromium or chromium and vanadium – used for steam turbine casing operating above 400⁰C. 5. High alloy steel (contains 9-12% chromium) – used as material for gas turbine casing. 5 Engr.AJ Labayen Emat-Prelim PROPERTIES, CHARACTERISTICS, LIMITATIONS AND APPLICATIONS OF NON-FERROUS METALS 1. Aluminum Aluminum is the most common metal of earth’s crust, being found in clays, kaolin, and certain rocks. Aluminum is characterized by its extreme lightness in weight Properties/Characteristics Limitations Applications/Uses 1. Pure aluminum is light, soft and 1. Requires processes to 1. Extensively used in bus bars and ductile. be welded. high voltage electric lines 2. Corrosion resistant 2. Low tensile strength 2. When in pure state it can be 3. High heat and electrical 3. Weak when in pure formed as foil, powder, sheet, conductivity. state and difficult to plate, rod, bar and wire. 4. Strength and hardness can be solder or weld. 3. It has the ability to be joined by increased when alloyed with riveting, resistance and fusion copper, magnesium, manganese, welding, brazing, and soldering. silicon and zinc. 4. It is used for making vats and 5. One of the most important tanks in chemical industry. characteristics of aluminum and 5. It is used for Alcladding its alloys is the thin oxide film (aluminum sheet used to cover which forms on their surfaces metal that is susceptible to when exposed to the corrosion) to prevent the atmosphere. If the oxide corrosion of the less resistant film is broken it will reform metal or alloy. quickly, and this gives these materials excellent corrosion resistance. 2. Copper Copper ranks next to iron and steel in terms of commercial importance because of its electrical conductivity and capacity to form useful alloys such as brass, bronze and monel metal. Properties/Characteristics Limitations Applications/Uses 1. High thermal and electrical 1. Unsuitable for structural 1. Copper can be formed into tube conductivities. The electrical and purposes due to its low or pipe used for water lines and thermal conductivities of high- tensile strength in industrial stills, evaporators, purity copper are greater than and condensers. those of any other metal except 2. Use for making electrical wires. silver 3. Use for form important alloys such bronze, brass and monel 2. Excellent corrosion-resistance to metal. chemicals, water and the atmosphere. 3. Possess ductility and malleability making wire drawing and sheet rolling easy. 6 Engr.AJ Labayen Emat-Prelim 3. Lead Lead is a bluish-white lustrous metal. Properties/Characteristics Limitations Applications/Uses 1. High corrosion resistance 1. Low mechanical strength 1. It can be extruded into pipes 2. Lead in pure state is very soft and 2. Tarnishes upon exposure that can be used chemical highly malleable to air plants and can be rolled into 3. Ductile sheet for tank linings since lead is not affected by water, air and sulfuric acid. 2. Use as form important alloys such as bearing materials, solder or type metals. 4. Zinc A silvery white metal with a blue tinge. Used as protective film in base metal that are prone to corrosion. Properties/Characteristics Limitations Applications/Uses 1. Brittle at room temperature. 1. Weak metal with tensile 1. Use to manufacture brass 2. Corrosion resistance strength less than half of 2. Use as protective coating in the 3. Ductile and malleable when mild carbon steel process of galvanizing and heated between 110ᵒC to 2. Cannot be used in load sherardizing. 150ᵒC. bearing applications. 5. Chromium Chromium is a lustrous, brittle, hard metal that can take a high mirror polish. Its color is silver-gray and it can be highly polished. Properties/Characteristics Limitations Applications/Uses 1. Magnetic and hard metal 1. Brittle when in pure state 1. Use as an alloying to steel in 2. High corrosion resistance order to make high chromium 3. Highly resistant to tarnishing steels. High-chromium steels are used to resist corrosion, to impart wear resistance and to increase the creep strength for the high-temperature services. 2. Onboard applications of chromium as an alloying element of steel are: a. Steam-generating plant - boiler plates and tubes, super heater headers and tubes, bodies of valves, soot blower elements, extraction pump shafts, air 7 Engr.AJ Labayen Emat-Prelim  ejector nozzles, feed pump impeller and shaft b. Diesel engine- valve seats, fuel valves, fuel nozzles, exhaust valves, valve guides, crankshaft, piston rings, connecting rod bolts, etc. 6. Manganese Manganese is a steel-gray, hard, shiny, brittle metal. Properties/Characteristics Limitations Applications/Uses 1. Hard and very brittle 1. Cannot be machined when 1. Use as an alloying element to in its pure form form monel metal that is used 2. Reacts rapidly in high for steam turbine casing. temperature and may even 2. Use as an alloying element to burn, giving off a bright steel. white light. 7. Molybdenum Molybdenum is a hard, silvery metal with a very high melting point. It is used primarily to make alloys with other metals. Properties/Characteristics Limitations Applications/Uses 1. High strength and hardness 1. Low temperature 1. Used as an alloying element to 2. Has high melting point embrittlement steel together with chromium 3. Low coefficient of thermal and vanadium. It is used as a expansion material for steam turbine rotor since molybdenum imparts resistance to creep and improved strength at elevated temperatures. 8. Tungsten Tungsten is a greyish-white lustrous metal, which is a solid at room temperature. Properties/Characteristics Limitations Applications/Uses 1. Has the highest melting point 1. Crack sensitive metal and Tungsten carbide is used for of any known metal which is usually brittle at room cutting tools and machining tools. 3380 ᵒC. temperature. 2. High tensile strength 3. Excellent corrosion resistance. 8 Engr.AJ Labayen Emat-Prelim 9. Magnesium Magnesium is a shiny, silver or gray colored metal that is light in weight and strong. Properties/Characteristics Limitations Applications/Uses 1. Good castability 1. Low elastic modulus 1. Use as an alloying element 2. Lowest density of all metallic 2. Limited cold workability with aluminum to improve constructional materials and toughness mechanical, fabrication and 3. Lightweight 3. Limited high strength and welding properties. 4. Corrosion resistant creep resistance at elevated 2. Use in the production of temperatures nodular cast iron. 4. high degree of shrinkage on solidification 9 Engr.AJ Labayen Emat-Prelim