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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?. Quench severity ≈ 1.25
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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? Quench severity ≈ 1.25 Water quench w/some agitation
Example quench design problems 7 Quench severity ≈ 1.25. What is hardness at center?
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
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)
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
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
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
Corrosion more cathodic electrical connection electrical connection Zn anode Cu cathode electrolyte electrolyte more anodic Result: the galvanic series
Corrosion Ex: 1 contains little dissolved oxygen 2 contains much dissolved oxygen 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes
Corrosion Practical example: crevice corrosion 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes
Corrosion Deformation ––> non-homogeneous residual stress 1 2 What constitutes an anode/cathode pair? Dissimilar metals Different electrolytes
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
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
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)
Corrosion Then what about micro cells? anode & cathode within single material operating on a micro scale Segregation (coring)