The universe is a playground of improvisation – it follows no external pattern – Cogitor Reticulus.

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Presentation transcript:

The universe is a playground of improvisation – it follows no external pattern – Cogitor Reticulus

From Timken handbook (http://www. timken NICKEL - Ni is used in low alloy steels to reduce the sensitivity of the steel to variations in heat treatment and distortion and cracking on quenching. It also improves low temperature toughness and hardenability.

Jominy test Specimen & water quench Hardness measurement

Jominy test

Quench severities

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

Example quench design problems 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 6

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

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

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)

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

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

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

Assignment: Review today's classnotes a. Jominy test b. Jominy curves c. quench severities d. Galvanic cell