lecture 12 - ME 330 Engineering Materials Lecture 12 Metal...

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Lecture 12 Metal Processing / Hardenability Stephen D. Downing Mechanical Science and Engineering © 2001 - 2010 University of Illinois Board of Trustees, All Rights Reserved ME 330 Engineering Materials
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 1 of 38 This Lecture . .. ± CCT Examples and Review ± Ferrous and Nonferrous Alloys ± Metal Fabrication ± Thermal Processing ± Heat Treatment of Steels ± Precipitation Hardening ± Hardness Testing
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 2 of 38 Pearlite, Bainite, Martensite ± Pearlite ± Formed by diffusion ± Ferrite and cementite ± Lamellar structure ± Stronger than ferrite ± Bainite ± Not as much diffusion ± Ferrite and cementite ± Not lamellar structure ± Harder that pearlite ± Martensite ± Diffusionless transformation ± Speed of sound ± BCT Structure (body-centered tetragon) with carbon interstitials ± Strong and brittle ± Austenite ± FCC Structure ± Above 725 C ± Transforms to other phases ± Ferrite ± Iron + C in solid solution ± Max. C is 0.022% ± Ductile ± Cementite ± Compound, Fe 3 C ± Hard and Brittle ± Contains 6.7% C
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 3 of 38 Austenitic Transformations
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 4 of 38 Isothermal Cooling Curve Pearlite, Bainite, Martensite γ γ γ +P Pearlite, P Bainite, B γ +B (Coarse pearlite) (Fine pearlite) time (s) 11 0 1 0 2 10 3 10 4 10 5 10 -1 Temperature ° C 400 500 600 700 300 200 800 T e γ Martensite, M M (start) M (50%) M (90%) (upper Bainite) (lower Bainite)
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 5 of 38 Quench More Than Once Quench to 650° Hold for 20 sec Reset the clock Quench to 400° Hold for 1000 sec. 50% pearlite •5 0 % b a i n i t e
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 6 of 38 Representative TTT Diagrams 4140 Steel Mn 0.77 Cr 0.98 Mo 0.21 4340 Steel Mn 0.78 Cr 0.80 Mo 0.33 Ni 1.79 1021 Steel 1045 Steel 1095 Steel
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 7 of 38 ± Isothermal heat treatment not common ± Practically, want to cool steadily to room temperature ± Isothermal curves shifted to longer times and lower temperatures ± Bainite will not form for plain carbon steel ± Alloying agents shifts the pearlite transformation curve to the right ± Now possible to obtain bainite ± 2 “knees” appear on curve Continuous Cooling Transformation (CCT)
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 8 of 38 Eutectoid Steel
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 9 of 38 Alloy Steel (4340)
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ME 330 - Lecture 12 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 10 of 38 Problems (CCT) s C s C s C s C / 01 . 0
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This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture 12 - ME 330 Engineering Materials Lecture 12 Metal...

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