ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 1 ver. 1 Deformation Processing - ExtrusionME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 2 Overview • Equipment • Characteristics • Mechanical Analysis – direct extrusion – indirect extrusion • Redundant work • DefectsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 3 Geometry (90o die) D1 D2 p dead zone 45o angleME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 4 EquipmentME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 5 ExtrusionME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 6 EquipmentME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 7 ExtrusionsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 8ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 9 Characteristics • Similar to closed die forging • Forging – slug (bulk) is forging – flash (extrusion) is waste • Extrusion – extrusion (flash) is part – billet (bulk) is wasteME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 10 Types • Direct • Indirect • Tubular • Hydrostatic • Cold ImpactME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 11 Types 1 – direct 2 – indirect 3 – heading (forging also)ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 12 Flow types • “Laminar” • “Turbulent” – redundant work – can bring outside of billet into center – leaving the skin keeps outside scale out of final extrusionME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 13 Steel extrusion • Tprocessing = 2100 to 2400oF (1150 – 1315oC) • Tmelting = 2500 - 2800oF (1370 – 1540oC) • Die  400oF (205oC) • Obviously “Hot” – above recyrstallization point • Lubricants – glass (viscous lube ) 0.001” thick – MoS2 – graphiteME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 14 Mechanical Analysis D1 D2 p dead zone 45o angle external friction internal friction xME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 15 Assumptions • Metal deforms uniformly – D1 to D2 • No redundant work • Can’t use slab analysis – die angles too great – friction too high • Dead zone sets up at 45 degreesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 16 p tfriction Upper bound analysis • Work input by external forces = plastic work expended friction externalcompress work toplasticfriction internalpressureW W W WME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 17 Rate of work = Power • Work rate = Power • Work rate = Area • stress • velocityME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 18 Pressure work input • Power = A • p • v – ram moves at velocity, vram rampvpDW 421ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 19 Internal “frictional” work input • Work determined by integrating rate of frictional work dissipation at each cross section from D2 to D1 – tfriction = tflow – vi is in x-direction D D + dD dx dL=dD/2 45o 12DDiflowfDdLvWtME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 20 • Volumetric flow rate – where D, Ai, vi are instantaneous Internal “frictional” work input iiramvAvAQ 1ramivDDv21ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 21 2121ln2DDDvWflowramftInternal “frictional” work input 12221DDflowramfDdDDvWtME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 22 Plastic work to compress input • Power = up x Area x velocity • hence tflowpduvolumeEnergy 2/ 21ln2DDramflowpwvDDDW 4ln42121tME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 23 Total work input (without external friction) • reducing 2121212121ln244ln444DDvDDDvDvpDflowramflowramramtt21ln414.32 DDpflowtME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 24 Extrusion ratio (re) • Reduction in area (RA) is large – it is not sensitive for classification • Use re instead RADDre11221ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 25 Extrusion pressure (without external friction) 22121ln707.1ln414.32DDDDpflowteflowrpln707.12tME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 26 Billet - wall friction • Assume limiting case: friction stress = shear flow stress tf = tflow tflow tflowME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 27 Additional pressure due to billet - wall friction xDDpflow1214t122 Dxpflowttflow tflowME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 28 Direct extrusion pressure 122222 Dxppppflowflowflowflowxtttt11212ln707.122ln414.32DxrpDxDDpeflowxflowxttME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 29 Indirect extrusion • No wall- billet interaction • Include wall - dead zone interaction – assume: friction stress = shear flow stress tf = tflow • Same result as direct extrusion – without external friction dead zone D1 D2 tflowME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 30 Additional pressure due to billet- dead zone friction 1212 DDpflowtD1 dead zone D2 tflow tflow  2421121DDDDpflowtME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 31 Indirect Extrusion Pressure 1212211ln707.121ln414.32DDrpDDDDpeflowflowttME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 32 12nKYnflowflowtStrain hardening (cold – below recrystallization