Forging

Question 1

Compared to forging

Answer 1

1.Less form freedom
2.Superior Strength
3.Superior ductility
4.Superior hardness

Question 2

Upsetting

Answer 2

1.Blank (billet or slug) is compressed between 2 flat dies to produce a decrease in height
2.Volume stays constant, so diameter increases

Question 3

Upsetting curve relationships(3)

Answer 3

1.C/S area increases
a. More force required to produce same stress
2.In cold forging strain hardening takes place
3. Friction b/w billet & die makes billet more resistant to deformation

Question 4

Stress/Strain - Upsetting =

Answer 4

sig_t = K*eps_t^n

sig_t = true stress
eps_t:true strain
K: material const.
n = strain hardening exp.

Question 5

Forging temps(3)

Answer 5

Cold:Below 40% T_melt (K)
Warm: B/W 40-80% T_melt
Hot: above 80% T_melt

Question 6

Hot Forging

Answer 6

Yield strength lower so less force required to deform metal
yield stress a function of strain rate – Zener-Hollomon

Question 7

Zener-Hollomon Parameter

Answer 7

Z = eps_r * exp(Q/RT)

eps_r: strain rate (1/s)
Q: Activation Engery(J/mol)
R: Universal Gas constant (8.314 J/mol*K)
T: Temperature (K)

Question 8

Hot Forging Drawbacks (4)

Answer 8

1. Distortion and warping during cooling
2. Oxidation (leads to cracks and surface faults)
3. No strain hardening at elevated temps
4. Can soften material from recrystallization and grain growth

Question 9

log(z) = 10 (solve for z)

Answer 9

Z = 10^10

Question 10

log(eps_r) = -1

Answer 10

eps_r = 1^-1 or .1 (1/s)

Question 11

Forging Methods (6)

Answer 11

1. Open die forging
2. Impression Forging
3. Press Forging
4. Net-Shape forging
5. Cold Heading
6. Coining