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Quench severities

Quench severities. 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? . Example quench design problems. 6. What quench should be used for 2" diam. 4140 bar to full harden 1/2" deep?.

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Quench severities

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  1. Quench severities

  2. 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?

  3. 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

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

  5. 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 ≈ 53

  6. 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)

  7. 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

  8. 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

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

  10. Corrosion more cathodic electrical connection electrical connection Zn anode Cu cathode electrolyte electrolyte more anodic Result: the galvanic series

  11. Corrosion Ex: 1 contains little dissolved oxygen 2 contains much dissolved oxygen 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes

  12. Corrosion Practical example: crevice corrosion 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes

  13. Corrosion Deformation ––> non-homogeneous residual stress 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes

  14. Corrosion Deformation ––> non-homogeneous residual stress 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes Non-passivated vs. passivated metal or alloy

  15. Corrosion What constitutes an anode/cathode pair? In summary– Anything that makes two half-cells different gives anode & cathode ––> corrosion We can call these types macro cells

  16. Corrosion Then what about micro cells? anode & cathode within single material operating on a micro scale Grain boundary - high energy region…anodic wrt bulk of grain Differently oriented grains - some planes of atoms dissolve faster than others Segregation (coring)

  17. Corrosion Then what about micro cells? anode & cathode within single material operating on a micro scale Segregation (coring)

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