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Last class - Ceramic tools Cast irons

Explore modern methods like carburizing, nitriding, and induction hardening for high-performance gear tooth applications. Learn about hardenability tests, quenching designs, and Jominy curves. Discover optimal quench severities for materials like SAE 1050 steel and 4140 alloy. Study corrosion principles and galvanic cells in material testing.

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Last class - Ceramic tools Cast irons

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  1. Last class - Ceramic tools Cast irons Today - Case hardening Hardenability test Quenching design

  2. Case hardening Gear tooth Carburizing - pack & gas - add C from CO gas Nitriding - add N from NH3 Case must be Q & T, except for nitrided Carbonitriding - add C & N from CO & NH3

  3. Case hardening Alternate case hardening method Induction hardening - surface heating by high-frequency AC, then Q & T

  4. Truck rear axle shaft Ford uses SAE 1050 steel with manganese content modified from 0.80 to 1.10% in rear axle shafts. Normally 0.60-0.90 Mn YS = 49 ksi, TS = 90 ksi, EL = 15% (hot-rolled) YS = 80 ksi, TS = 120 ksi (Q+T) depends on heat treat conditions

  5. Jominy test Specimen & water quench Hardness measurement

  6. Jominy test

  7. Quench severities

  8. Example quench design problems Jominy curve 6 6 What is max bar size for 4140 which will full harden with quench severity of 0.35?

  9. Example quench design problems 6 What quench should be used for 2" diam. 4140 bar to full harden 1/2" deep? Quench severity ≈ 1.25 Water quench w/some agitation

  10. Example quench design problems 7 Quench severity ≈ 1.25. What is hardness at center?

  11. Example quench design problems Jominy curve 7 Quench severity ≈ 1.25. What is hardness at center? 2" bar quenched at 1.25 corresponds to 7/16" on Jominy bar Hardness ≈ 54

  12. Corrosion Hint for exams (and life): A substance which is corrosive will corrode other substances SS is thus certainly non-corrosive But it is also non-corrodable (in most instances)

  13. Corrosion Galvanic cell is necessary electrical connection anode cathode electrolyte Most corrosion is electrochemical No corrosion if one of these is missing: anode cathode electrolyte electrical connection

  14. Corrosion Galvanic cell is necessary electrical connection anode cathode electrolyte Most corrosion is electrochemical Corrosion at anode Me = Me+n + ne– (metal dissolves) No dissolution at cathode

  15. Corrosion electrical connection Zn Cu electrolyte What constitutes an anode/cathode pair? Dissimilar metals Ex: Cu & Zn (Zn corrodes) How do we know? Many combos tried experimentally

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