Microsoft power point lecture4
- 1. 1 MANUFACTURINGMANUFACTURING PROCESSESPROCESSES -- AMEM 201AMEM 201 –– Lecture 4:Lecture 4: Forming ProcessesForming Processes (Rolling, Extrusion, Forging, Drawing)(Rolling, Extrusion, Forging, Drawing) DR. SOTIRIS L. OMIROU 22 Forming ProcessesForming Processes -- Definition & TypesDefinition & Types -- Forming processes are those in which the shape of a metal piece is changed by plastic deformation Forming processes are commonly classified into hot-working and cold-working operations. Typical forming processes are: Rolling Extrusion Forging Drawing
- 2. 2 33 Forming ProcessesForming Processes -- RollingRolling -- Rolling is a process of reduction of the cross-sectional area or shaping a metal piece through the deformation caused by a pair of rotating in opposite directions metal rolls. 44 The gap between the rotating rolls is less than the thickness of the entering bar therefore a friction force is necessary in order to bite the bar and to pull it through the rolls. A metal bar passing through the rotating rolls is squeezed, and it elongates while its cross section area decreases. Forming ProcessesForming Processes -- RollingRolling --
- 3. 3 55 A machine used for rolling metal is called rolling mill. A typical rolling mill consists of a pair of rolls driven by an electric motor transmitting a torque through a gear and pair of cardans. The rolls are equipped with bearings and mounted in a stand with a screw-down mechanism. Forming ProcessesForming Processes -- RollingRolling -- 66 Rotating rolls perform two main functions:Rotating rolls perform two main functions: Pull the work into the gap between them by frictionPull the work into the gap between them by friction between workpart and rollsbetween workpart and rolls Simultaneously squeeze the work to reduce its crossSimultaneously squeeze the work to reduce its cross sectionsection Forming ProcessesForming Processes -- RollingRolling --
- 4. 4 77 EquipmentEquipment –– Picture 1Picture 1 7 Rolls Rolls Housing/ Stand Adjusting Screw 88 8 Adjusting screwAdjusting screw EquipmentEquipment –– Picture 2Picture 2
- 5. 5 99 9 Pictures showing the rolling process:Pictures showing the rolling process: EquipmentEquipment –– Picture 3Picture 3 1010 Types of RollingTypes of Rolling Based on workpiece geometry :Based on workpiece geometry : –– Flat rollingFlat rolling -- used to reduce thickness of a rectangularused to reduce thickness of a rectangular cross sectioncross section –– Shape rollingShape rolling -- square cross section is formed into asquare cross section is formed into a shape.shape. Based on work temperature :Based on work temperature : –– Hot RollingHot Rolling –– most common due to the large amount ofmost common due to the large amount of deformation requireddeformation required –– Cold rollingCold rolling –– produces finished sheet and plate stockproduces finished sheet and plate stock
- 6. 6 1111 Hot rolling is a rolling operation carried out at a temperature just below the metal melting point, permitting large amount of deformation. Cold rolling is a rolling operation carried out at room temperature. Cold rolling is commonly conducted after hot rolling when good surface quality and low thickness tolerance are needed. Cold rolling causes material strengthening. Types of RollingTypes of Rolling 1212 Some of the steel products made in a rolling mill.Some of the steel products made in a rolling mill. Rolled Products Made of SteelRolled Products Made of Steel
- 7. 7 1313 Side view of flat rolling, indicating before and after thicknessSide view of flat rolling, indicating before and after thicknesses,es, work velocities, angle of contact with rolls, and other featureswork velocities, angle of contact with rolls, and other features.. Diagram of Flat RollingDiagram of Flat Rolling 1414 Flat Rolling TerminologyFlat Rolling Terminology DraftDraft = amount of thickness reduction= amount of thickness reduction fo ttd Where, d = draft; to = starting thickness; tf = final thickness
- 8. 8 1515 ReductionReduction = draft expressed as a fraction of starting= draft expressed as a fraction of starting stock thickness:stock thickness: ot d r where r = reduction Flat Rolling TerminologyFlat Rolling Terminology 1616 Shape RollingShape Rolling AccomplishedAccomplished by passing work through rollsby passing work through rolls that have the reverse of desired shapethat have the reverse of desired shape Products include:Products include: –– Construction shapes such as IConstruction shapes such as I--beams,beams, LL--beams, and Ubeams, and U--channelschannels –– Rails for railroad tracksRails for railroad tracks –– Round and square bars and rodsRound and square bars and rods
- 9. 9 1717 Rolling MillsRolling Mills Equipment is massive and expensiveEquipment is massive and expensive Rolling mill configurations:Rolling mill configurations: –– TwoTwo--high:high: two opposing rollstwo opposing rolls –– ThreeThree--high:high: work passes through rolls in both directionswork passes through rolls in both directions –– FourFour--high:high: backing rolls support smaller work rollsbacking rolls support smaller work rolls –– Cluster mill:Cluster mill: multiple backing rolls on smaller rollsmultiple backing rolls on smaller rolls –– Tandem rolling mill:Tandem rolling mill: sequence of twosequence of two--high millshigh mills 1818 Various configurations of rolling mills: (a) 2Various configurations of rolling mills: (a) 2--high rolling mill.high rolling mill. TwoTwo--High Rolling MillHigh Rolling Mill
- 10. 10 1919 Various configurations of rolling mills: (b) 3Various configurations of rolling mills: (b) 3--high rolling mill.high rolling mill. ThreeThree--High Rolling MillHigh Rolling Mill 2020 Various configurations of rolling mills: (c) fourVarious configurations of rolling mills: (c) four--high rolling mill.high rolling mill. FourFour--High Rolling MillHigh Rolling Mill
- 11. 11 2121 Multiple backing rolls allow even smaller roll diametersMultiple backing rolls allow even smaller roll diameters Various configurations of rolling mills: (d) cluster millVarious configurations of rolling mills: (d) cluster mill Cluster MillCluster Mill 2222 VariousVarious configurations of rolling mills: (e) tandem rolling mill.configurations of rolling mills: (e) tandem rolling mill. Tandem Rolling MillTandem Rolling Mill Rolling mills have several stages, where the each stage successively reduces the thickness of the stock until the desired cross section is achieved.
- 12. 12 2323 Thread RollingThread Rolling -- DefinitionDefinition Deformation process used to form threads onDeformation process used to form threads on cylindrical parts by rolling them between two diescylindrical parts by rolling them between two dies Important commercial process for massImportant commercial process for mass producing bolts and screwsproducing bolts and screws Performed by cold working in thread rollingPerformed by cold working in thread rolling machinesmachines 2424 Thread rolling with flat dies: (1) start of cycle, and (2) end oThread rolling with flat dies: (1) start of cycle, and (2) end of cycle.f cycle. Thread RollingThread Rolling
- 13. 13 2525 Thread RollingThread Rolling AdvantagesAdvantages over thread cutting (machining):over thread cutting (machining): –– Higher production ratesHigher production rates –– Better material utilizationBetter material utilization –– Stronger threads and better fatigue resistance dueStronger threads and better fatigue resistance due to work hardeningto work hardening 2626 Rolling of screw threads Thread RollingThread Rolling
- 14. 14 2727 Ring RollingRing Rolling -- DefinitionDefinition Deformation process in which a thickDeformation process in which a thick--walled ring of smallerwalled ring of smaller diameter is rolled into a thindiameter is rolled into a thin--walled ring of largerwalled ring of larger diameterdiameter Applications:Applications: ball and roller bearing races, steel tires forball and roller bearing races, steel tires for railroad wheels, and rings for pipes, pressure vessels,railroad wheels, and rings for pipes, pressure vessels, and rotating machineryand rotating machinery 2828 Ring rolling used to reduce the wall thickness and increase theRing rolling used to reduce the wall thickness and increase the diameter of a ring:diameter of a ring: (1) start, and (2) completion of process.(1) start, and (2) completion of process. Ring RollingRing Rolling As thickAs thick--walled ring is compressed, deformed metal elongates,walled ring is compressed, deformed metal elongates, causing diameter of ring to be enlargedcausing diameter of ring to be enlarged Hot working process for large rings and cold working process forHot working process for large rings and cold working process for smaller ringssmaller rings
- 15. 15 2929 Forming ProcessesForming Processes -- ExtrusionExtrusion -- Extrusion is a metal forming process involving shaping a metal billet (hot or cold) by forcing it through a die with an opening. The two possible schemes of extrusion are presented in the picture: 3030 Forming ProcessesForming Processes -- Direct ExtrusionDirect Extrusion -- The metal billet is placed to the container of the extrusion press. The die with an opening is mounted at the end of the container. When the hydraulically driven ram presses the billet, the metal starts to flow through the opening forming the extruded product of the required cross section. In the direct extrusion the extruded metal flows in the direction of the ram motion.
- 16. 16 3131 Forming ProcessesForming Processes -- Indirect ExtrusionIndirect Extrusion -- In the indirect extrusion the metal flows in the direction opposite to the ram motion. Indirect extrusion requires a lower force than direct process as there is no friction between the billet and inside walls of the container. 3232 Forming ProcessesForming Processes -- ExtrusionExtrusion -- In the hot extrusion process the metal billet is preheated to the required temperature: (450°C - 500°C) for aluminum alloys and (700°C - 800°C) for Copper alloys. The dies are manufactured from hard alloyed steels. Extrusion is used for manufacturing round and hexagonal rods, tubes, various profiles (mainly aluminium) and other shapes. Typical examples of parts made by extrusion are the aluminium door- and window-frames.
- 17. 17 3333 (a) Direct extrusion to produce a hollow or semi(a) Direct extrusion to produce a hollow or semi--hollowhollow cross sections; (b) hollow (c) semicross sections; (b) hollow (c) semi--hollow cross sections.hollow cross sections. Hollow and SemiHollow and Semi--Hollow ShapesHollow Shapes 3434 Extrusion RatioExtrusion Ratio Also called theAlso called the reduction ratioreduction ratio, it is defined as, it is defined as where,where, rrxx = extrusion ratio;= extrusion ratio; AAoo = cross= cross--sectional area of the starting billet;sectional area of the starting billet; AAff = final cross= final cross--sectional area of the extrudedsectional area of the extruded sectionsection Applies to both direct and indirect extrusionApplies to both direct and indirect extrusion f o x A A r
- 18. 18 3535 (a)(a) Definition of die angle;Definition of die angle; (b)(b) Effect of die angle on ram force.Effect of die angle on ram force. Extrusion Die FeaturesExtrusion Die Features 3636 Forging is a compressive metal forming process, involving shaping a metal piece by hammer or press. Forming ProcessesForming Processes -- ForgingForging -- The figure shows an open- die forging process. Note the red hot bar stock in place.
- 19. 19 3737 Classification of Forging OperationsClassification of Forging Operations Cold vs. hot forging:Cold vs. hot forging: –– Hot or warm forgingHot or warm forging –– most common, duemost common, due to the significant deformation and the needto the significant deformation and the need to reduce strength and increase ductility ofto reduce strength and increase ductility of work metalwork metal –– Cold forgingCold forging –– advantage: increasedadvantage: increased strength that results from strain hardeningstrength that results from strain hardening Impact vs. press forging:Impact vs. press forging: –– Forge hammerForge hammer -- applies an impact loadapplies an impact load –– Forge pressForge press -- applies gradual pressureapplies gradual pressure 3838 Types of Forging DiesTypes of Forging Dies -- OpenOpen--diedie OpenOpen--die forgingdie forging -- work is compressedwork is compressed between two flat dies, allowing metal tobetween two flat dies, allowing metal to flow laterally with minimum constraintflow laterally with minimum constraint
- 20. 20 3939 Types of Forging DiesTypes of Forging Dies -- ImpressionImpression--diedie ImpressionImpression--die forgingdie forging -- die containsdie contains cavity or impression that is imparted tocavity or impression that is imparted to workpartworkpart. Metal flow is constrained so that. Metal flow is constrained so that flash is createdflash is created 4040 Types of Forging DiesTypes of Forging Dies -- FlashlessFlashless FlashlessFlashless forgingforging -- workpart is completelyworkpart is completely constrained in die. No excess flash is createdconstrained in die. No excess flash is created
- 21. 21 4141 Usually forged parts are much stronger/tougher than cast or machined parts made from the same material. This is because the hammering process arranges the micro- structure of the metal so that the crystal grains get aligned along the part profile. This leads to an increase in strength. It is therefore common to use forging to make parts that will carry very high stresses during their use, rather than casting. Quality of forged partsQuality of forged parts 4242 Forming ProcessesForming Processes -- DrawingDrawing -- Drawing is a metal forming process involving pulling a workpiece (cold or hot) through a die providing reduction of the cross section of the workpiece.
- 22. 22 4343 Forming ProcessesForming Processes -- DrawingDrawing -- Drawing is the process most commonly used to make wires from round bars; this process is very similar to extrusion, except that instead of pressure from the back end, in drawing, the wire is pulled from the side where it emerges from the circular die. Dies are made of specially hardened tool steels, or tungsten carbide. Diamond dies are used for drawing very fine wires. Drawing may be hot (the stock is heated to a high temperature for processing), or cold (the stock is not heated). 4444 Drawing of bar, rod, or wire.Drawing of bar, rod, or wire. Wire and Bar DrawingWire and Bar Drawing
- 23. 23 4545 Area Reduction in DrawingArea Reduction in Drawing Change in size of work is usually given byChange in size of work is usually given by areaarea reduction:reduction: where,where, rr = area reduction in drawing;= area reduction in drawing; AAoo = original area of work;= original area of work; AAff = area of final work;= area of final work; o fo A AA r