Chapter 12

Question 1

Bulk deformation process

Answer 1

Rolling, forging, extrusion and wire and bar drawing

Question 2

Pressworking parts and tooling

Answer 2

Part - Stampings

Tooling - Punch and die

Question 3

Average Flow Stress

Yf e K n

Answer 3

Yf is average flow stress
e is maximum strain
K is strength
n strain hardening
K and n reduced at high temp

Question 4

Stronger? Machined thread or rolled thread

Answer 4

Rolled thread. Grains do not match up.

Question 5

Temps for cold, warm and hot working

Answer 5

Cold 30%
Warm 30 - 50
Hot 50 to 75

Question 6

Cold working properties

Adv (4) Dis (3)

Answer 6

No machining required
Both near net shape and net shape
Mass production

Better accuracy
Better surf fin
Increases strength and hardness
No heating of work required

Higher forces and power needed
No scale or dirt
Ductility and strain hardening limit amount of forming possible

Question 7

Warm Working Adv(3) Dis(1)

Answer 7

Lower forces and power than CW
More intricate geometries
Lower need of annealing

Workpiece must be heated

Question 8

Hot working

Adv(5) Dis(4)

Answer 8

Workpart can be superdeformed
Lower forces needed
When metals fracture in CW they will be HW
Strength isotropic
No strengthening of park after forming

Lower dimensional accuracy
Higher energy to heat and deform
Surface oxidation so bad surf fin
Shorter tool life

Question 9

Lubricant needs (4)

Answer 9

Good temp for hot and cold
Not chemical reactivity with tool or work metals
Ease of application
Cost