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Last class -
Ceramic toolsCast irons
Last class -
Ceramic toolsCast irons
Today -
Case hardeningHardenability testQuenching design
Today -
Case hardeningHardenability testQuenching design
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Case hardeningCase hardening
Gear toothGear tooth
Carburizing - pack & gas - add C from CO gasCarburizing - pack & gas - add C from CO gas
Nitriding - add N from NH3
Nitriding - add N from NH3Carbonitriding - add C & N from CO & NH3
Carbonitriding - add C & N from CO & NH3
Case must be Q & T, except for nitrided
Case must be Q & T, except for nitrided
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Case hardeningCase hardening
Alternate case hardening methodAlternate case hardening method
Induction hardening - surface heating by high-frequency AC, then Q & T
Induction hardening - surface heating by high-frequency AC, then Q & T
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Truck rear axle shaftTruck 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
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
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Jominy testJominy test
Specimen & water quenchSpecimen & water quench Hardness measurementHardness measurement
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Jominy testJominy test
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Quench severitiesQuench severities
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Example quench design problemsExample quench design problems
What is max bar size for 4140 which will full harden with quench severity of 0.35?
What is max bar size for 4140 which will full harden with quench severity of 0.35?
Jominy curve
66
66
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Example quench design problemsExample quench design problems
What quench should be used for 2" diam. 4140 bar to full harden 1/2" deep?What quench should be used for 2" diam. 4140 bar to full harden 1/2" deep?
66
Quench severity ≈ 1.25 Water quench w/some agitation
Quench severity ≈ 1.25 Water quench w/some agitation
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Example quench design problemsExample quench design problems
Quench severity ≈ 1.25. What is hardness at center?Quench severity ≈ 1.25. What is hardness at center?
77
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Jominy curveJominy curve
Example quench design problemsExample quench design problems
Quench severity ≈ 1.25. What is hardness at center?Quench severity ≈ 1.25. What is hardness at center?
2" bar quenched at 1.25 corresponds to 7/16" on Jominy bar Hardness ≈ 54
2" bar quenched at 1.25 corresponds to 7/16" on Jominy bar Hardness ≈ 54
77
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Corrosion 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)
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)
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Corrosion Corrosion
Most corrosion is electrochemicalMost corrosion is electrochemical
Galvanic cell is necessaryGalvanic cell is necessary
No corrosion if one of these is missing:
anode cathode electrolyte electrical connection
No corrosion if one of these is missing:
anode cathode electrolyte electrical connection
anode cathode
electrolyte
electrical connection
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Corrosion Corrosion
Most corrosion is electrochemicalMost corrosion is electrochemical
Galvanic cell is necessaryGalvanic cell is necessary
Corrosion at anode Me = Me+n + ne–
(metal dissolves)
Corrosion at anode Me = Me+n + ne–
(metal dissolves)
anode cathode
electrolyte
electrical connection
No dissolution at cathode
No dissolution at cathode
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Corrosion Corrosion
What constitutes an anode/cathode pair?What constitutes an anode/cathode pair?
Zn Cu
electrolyte
electrical connection
Dissimilar metalsDissimilar metals
Ex: Cu & Zn (Zn corrodes)Ex: Cu & Zn (Zn corrodes)
How do we know?
Many combos tried experimentally
How do we know?
Many combos tried experimentally