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Engineering Materials and Processes Lecture 7 – Mechanical Shaping of Metals Mechanical Deformation of Metals

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Engineering Materials and Processes Lecture 7 – Mechanical Shaping of Metals Mechanical Deformation of Metals Engineering Materials and Processes Lecture 7 – Mechanical shaping of metals Mechanical Deformation of Metals Reference Text Section Higgins RA & Bolton, 2010. Materials for Engineers and Technicians, Ch 7 5th ed, Butterworth Heinemann Additional Readings Section Sheedy, P. A, 1994. Materials : Their properties, testing and selection Ch 13 Callister, W. Jr. and Rethwisch, D., 2010, Materials Science and N.A. Engineering: An Introduction, 8th Ed, Wiley, New York. Ashby, M.F., 2011. Materials Selection in Mechanical Design, 4th Ed, Ch 13 Butterworth Heinemann, Oxford, UK. Engineering Materials and Processes Ashby: Fig 13.2 The classes of processes Engineering Materials and Processes Hot-working processes (Higgins 7.2) Hot Working processes are carried out above the recrystallisation temperature of the material. 7.2 Hot Working Processes 7.2.1 Forging 7.2.2 Hot-rolling Engineering Materials and Processes Hot-working processes: Forging (Higgins 7.2.1) VIDEO: Open-die forging can produce forgings from a kg to more than 150 tonnes. “Open-die” means the metal is not confined laterally during forging. The process works progressively from the starting stock into the desired shape. Flat-faced dies are usual. Wide range of shapes and sizes are possible, especially suited to large custom parts like a ship’s propeller shaft. Seamless Rolled Ring Forging: Starts with a cast billet, then upset and punched to form a donut shape, then rolling and squeezing (or in some cases, pounding) the donut into a thin ring. Ring diameters can be anywhere from a 100mm to 10m. Engineering Materials and Processes Hot-working processes: Hot-Rolling (Higgins 7.2.2) Hot Rolling (Billet to plate/sheet): Dalarna University www.du.se (Creative Commons) Breaking down billets (large thick slabs cast from the furnace) into successively thinner plate, and finally sheet. Fun and Games with Hot Rolling… HD-720 “Cobble” = British terminology “Miss-roll = US terminology Cobble: http://www.youtube.com/watch?v=NnqZ-ybpdhQ Cobble 2: http://www.youtube.com/watch?v=v4p-YCtbhMQ Engineering Materials and Processes Hot-working processes: Extrusion (Higgins 7.2.3) Like squeezing toothpaste from a tube, material is forced through a die and is plastically deformed into the cross-section of the die. The die hole can be almost any shape, (e.g. a circular die will make a rod) Mostly used for low temperature metals: copper pipes, aluminium extrusions. Steel can only be drawn or hot rolled, but not extruded in the same way as aluminium. Pity. Would have been a nice way to make steel pipe. openlearn.open.ac.uk Engineering Materials and Processes Hot-working processes: Extrusion (Higgins 7.2.3) Extruding a hollow shape is an obvious problem. How do you hold the die that forms the hole? Extrusion bridge die making a hollow section product. Note: in reality, the die and ring are held together. http://openlearn.open.ac.uk/mod/oucontent/view.php?id=399740&section=3.5 Engineering Materials and Processes Hot-working processes: Extrusion (Higgins 7.2.3) Aluminium dominates the extrusion industry because the metal has excellent ductility without the need for extreme temperatures. It is also an obvious choice for window frames, structural and decorative parts, and almost anything of a constant cross-section. Heated to about 900oF (480oC) to keep it well above the recrystallisation temperature (150oC). The design of the extrusion profile effects extrusion performance. (E.g. Better to have symmetry, avoid long flats, minimize internal holes, etc…) PBCLinear Engineering Materials and Processes Hot-working processes 3 (Higgins 7.2) Other Hot Working Processes Hot forming of Coil Springs: http://www.youtube.com/watch?v=6BplSiK8qK8 Friction Welding: http://www.youtube.com/watch?v=5JbnDXw-0pM Engineering Materials and Processes Cold-working processes (Higgins 7.3) Cold Working processes are carried out below the recrystallisation temperature of the material. See text: 7.3 Cold Working Processes 7.3.1 Cold-rolling 7.3.2 Drawing 7.3.3 Cold-pressing and deep-drawing Bolts: http://www.youtube.com/watch?v=7PQyant3mCc 7.3.4 Spinning 7.3.5 Stretch-forming 7.3.6 Coining and embossing 7.3.7 Impact-extrusion Engineering Materials and Processes Cold-working processes: Cold Rolling (Higgins 7.3.1) Cold Rolling Steel Sheet: Steelmaking: Cold Rolling by CorusBCSATraining Roll Curving Steel plate for Wind Turbine Tower http://www.tsgnorthamerica.com Engineering Materials and Processes Cold-working processes: Drawing (Higgins 7.3.2) Cold Drawing of Hexagonal Bar http://www.youtube.com/watch?v=72JWZAWZp5Q Engineering Materials and Processes Cold-working processes: Cold Pressing and Deep Drawing (Higgins 7.3.3) Forming Bolts http://www.youtube.com/watch?v=7PQyant3mCc Engineering Materials and Processes Cold-working processes: Spinning (Higgins 7.3.4) Metal Spinning http://www.youtube.com/watch?v=7PQyant3mCc Engineering Materials and Processes Cold-working processes: Stretch-forming (Higgins 7.3.5) Stretch Forming http://www.youtube.com/watch?v=eSVi7dC5L_Q Engineering Materials and Processes Cold-working processes: Coining and embossing (Higgins 7.3.6) Stamping http://www.youtube.com/watch?v=I7uBmlwxXRU Engineering Materials and Processes Cold-working processes: Impact Extrusion (Higgins 7.3.7) Impact Extrusion http://www.youtube.com/watch?v=zMhVPId-pRA Engineering Materials and Processes Cold-working processes: Roll Forming Roll Forming – Roofing http://www.youtube.com/watch?v=HrDegG_zkWY Spiral Ducting http://www.youtube.com/watch?v=fIe8PQXNrUo ERW Pipe Forming (5” or 125mm) http://www.youtube.com/watch?v=77utCIwKSn4 Engineering Materials and Processes Powder Metallurgy (Higgins 7.4) Powder Metallurgy (PM) involves pressing the powder and then heating (above recrystallisation but below the melting point) – called sintering – which binds the particles together. See text: 7.4.1 Uses of powder-metallurgy 7.4.2 Cemented carbides 7.4.3 Sintered-bronze bearings Powder Metallurgy http://www.youtube.com/watch?v=_0wd8sgNIOg Engineering Materials and Processes Machining metals (Higgins 7.5) Machining is a cold-working process in which the cutting edge of a tool forms shavings or chips of the material being cut. See text: Higgins 7.5 Machining Centre: 5 axis various jobs http://www.youtube.com/watch?v=0LCaRqQ8Qf8 High Speed Video: Milling Cutter http://www.youtube.com/watch?v=IUBQN1JfY80 Machining a large shaft – Lathe http://www.youtube.com/watch?v=ObsvfP5Nrw4 Engineering Materials and Processes Profile Cutting This is for cutting sheet material. Usually CNC • Laser. Fast, accurate, good finish, many materials. Finest kerf. Fussy maintenance. High speed laser cutting http://www.youtube.com/watch?v=RQIJSsbvolc • Water jet: Almost any material. No heat damage. Water jet cutting bullet-proof glass http://www.youtube.com/watch?v=KmUWA_oXDEQ Engineering Materials and Processes Profile Cutting This is for cutting sheet material. Usually CNC • Flame Cut (Gas): Cheaper system, good for thick steel plate. Worst quality. High speed laser cutting http://www.youtube.com/watch?v=Zy3g4-D1ZeA • Plasma: Better finish than flame cut, but cheaper than laser. CNC Plasma http://www.youtube.com/watch?v=FHUs_u27IpE • CNC router: Typically wood, plastic and soft metals (e.g. thin aluminium), often held down by vacuum onto a spoil board (MDF) Engineering Materials and Processes Video Forming & Shaping Metal Davis, John. Warriewood, NSW : Classroom Video, c2002. DVD (22 min.) Hot Forming, Cold Forming, Machining Mt Druitt College Library: DVD 671.3/FORM Recommended Viewing: All sections. Engineering Materials and Processes Online Properties Resources. Graphical comparison of materials properties. DoITPoMS: Dissemination of IT for the Promotion of Materials Science Wikipedia: Materials properties Forming: Forging, Rolling, Extrusion, Machining CorusBCSATraining http://www.youtube.com/user/CorusBCSATraining Engineering Materials and Processes GLOSSARY Hot forming Coolant Cold forming Facing Recrystallisation Turning Annealing Metal Spinning Work Hardening Roll Forming Stress Relieving Extrusion Drawing Hot Rolling ERW Cold Rolling CNC Powder Metallurgy Profile Cutting Sintering Plasma Cutting Drawing Laser Cutting Blanking Oxy Cutting Bending Water Jet Cutting Stretching Open Die Forging Upset Forging Cavity Forging Engineering Materials and Processes QUESTIONS Callister: NA Moodle XML: 10107 Processing 1. Define all the glossary terms. 2. Explain which type of process would be used for making railway tracks and compare it to the process of making road crash barriers. Explain the difference. 3. Why are aluminium and copper based metals extruded, but not steel. 4. Explain the process of making an ERW round pipe. 5. Make a table comparing the various profile cutting technologies. Compare machine cost, running cost, speed, accuracy, thickness, material range. 6. CNC if far superior to manual control of a machining operation. Why do we still have manual machines at all? 7. A metal gear needs to be manufactured in the tens of thousands. Compare the process options of powder metallurgy, machining, casting and forging. Include cost of die, material costs, running costs, speed, accuracy, product performance. (See: http://openlearn.open.ac.uk/mod/oucontent/view.php?id=399740&section=3.9) Engineering Materials and Processes.
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