Chapter 19

Chapter 19 - ANNOUNCEMENTS - 4/19 Reading: Chapters 11, 19...

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Unformatted text preview: ANNOUNCEMENTS - 4/19 Reading: Chapters 11, 19 Final Exam: 10:15-12:15, Tuesday, May 8 Chapter 19 - 1 Quenching Medium & Geometry Effect of quenching medium: Medium air oil water Hardness low moderate high Severity of Quench low moderate high Effect of geometry and size (industrial parts): When surface-to-volume ratio increases: cooling rate increases hardness increases Position center surface Cooling rate low high Hardness low high Chapter 19 - 2 Hardenability Steels Ability to form martensite Jominy end quench test to measure hardenability. Chapter 19 - 3 Hardness versus distance from the quenched end. Adapted from Fig. 11.11, Callister 7e . (Fig. 11.11 adapted from A.G. Guy, Essentials of Materials Science , McGraw-Hill Book Company, New York, 1978.) Adapted from Fig. 11.12, Callister 7e . 24C water specimen (heated to phase field) flat ground Rockwell C hardness tests Hardness, HRC Distance from quenched end Hardness Changes with Position The cooling rate varies with position. Adapted from Fig. 11.13, Callister 7e . (Fig. 11.13 adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and Cooling Transformation Diagrams , American Society for Metals, 1977, p. 376.) distance from quenched end (in) Hardness, HRC 20 40 60 1 2 3 600 400 200 A M A P 0.1 1 10 100 1000 T (C) M (start) Time (s) 0% 100% M (finish) M a r t e n s i t e M a r t e n s i t e + P e a r l i t e F i n e P e a r l i t e P e a r l i t e Chapter 19 - 4 Thermal Properties ISSUES TO ADDRESS... How does a material respond to heat ? How do we define and measure... heat capacity coefficient of thermal expansion thermal conductivity thermal stress thermal shock resistance How do ceramics, metals, and polymers rank? Chapter 19 - 5 Heat Capacity General: The ability of a material to absorb heat....
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Chapter 19 - ANNOUNCEMENTS - 4/19 Reading: Chapters 11, 19...

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