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

2. 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.

3. Jominy test
Specimen & water quench
Hardness measurement

4. Jominy test

5. Quench severities

6. 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

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

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

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

10. 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)

11. 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

12. 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

13. 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

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