powerpoint presentationryba/coursewo… · ppt file · web view · 2007-03-05last class - ceramic...
TRANSCRIPT
Case hardening
Gear toothCarburizing - pack & gas - add C from CO gas
Nitriding - add N from NH3Carbonitriding - add C & N from CO & NH3
Case must be Q & T, except for nitrided
Case hardening
Alternate case hardening method
Induction hardening - surface heating by high-frequency AC, then Q & T
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
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?
6
Quench severity ≈ 1.25 Water quench w/some agitation
Jominy curve
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
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)
Corrosion
Most corrosion is electrochemical
Galvanic cell is necessary
No corrosion if one of these is missing:
anode cathode electrolyte electrical connection
anode cathode
electrolyte
electrical connection
Corrosion
Most corrosion is electrochemical
Galvanic cell is necessary
Corrosion at anode Me = Me+n + ne–
(metal dissolves)
anode cathode
electrolyte
electrical connection
No dissolution at cathode