Forging

Question 1

Forming Processes: Independent Variables

Answer 1

Independent variables are the aspects of the processes that the engineer
or operator has direct control
◦
Starting material
◦
Starting geometry of the workpiece
◦
Tool or die geometry
◦
Lubrication
◦
Starting temperature
◦
Speed of operation
◦
Amount of deformation

Question 2

Dependent Variables
determined by the independent variable selection

Answer 2

◦
Force or power requirements
◦
Material properties of the product
◦
Exit or final temperature
◦
Surface finish and precision
◦
Nature of the material flow

Question 3

Independent Dependent Relationships

Answer 3

Independent variables
control is direct and immediate
Dependent variables
control is entirely indirect

Question 4

Friction and Lubrication Under Metalworking
Conditions

Answer 4

50% of the energy is spent in overcoming friction

Changes in lubrication can alter material flow, create or eliminate defects,
alter surface finish and dimensional precision, and modify product
properties

Production rates, tool design, tool wear, and process optimization depend
on the ability to determine and control friction

Question 5

2 forms of friction

Answer 5

◦
Abrasion
◦
Adhesion

Question 6

Surface Deterioration

Answer 6

Surface wear is related to friction

Question 7

which wear isnt and is objectionable

Answer 7

Wear on the workpiece is not objectionable,
but wear on the tooling is!

Tooling wear is economically costly and can impact dimensional precision

Tolerance control can be lost

Tool wear can impact the surface finish

Question 8

In general, an increase in temperature is related to

Answer 8

a decrease in strength, increase in ductility,
and decrease in the rate of strain hardening

Question 9

3 different ways to process our material

Answer 9

Hot working
Cold working
Warm working

Question 10

Hot Working

Answer 10

Plastic deformation of metals at a temperature
above the recrystallization temperature

Question 11

adv and diasdv of hot working

Answer 11

diasdv: poor sf with a lot of impurities
hard to machine/grind
poor aesthetic
size of grains upon cooling not uniform

adv
easier faster and cheaper to form the material

Question 12

as cooling, Recrystallization is followed by:

Answer 12

◦
grain growth
◦
additional deformation and recrystallization
◦
drop in temperature that will terminate diffusion and freeze the recrystallized structure

Question 13

impurity flow during hot working

Answer 13

During plastic deformation, impurities
tend to flow along with the base metal
or fraction into rows of fragments

Question 14

cold working? adv?

Answer 14

Cold Working
Plastic deformation
below the recrystallization temperature

Advantages as compared to hot working
◦
Better surface finish
◦
Superior dimensional control
◦
Strength, fatigue, and wear are improved
◦
Contamination is minimized

Question 15

Disadvantages of Cold Working

Answer 15

Higher forces are required to initiate and complete the deformation
Heavier and more powerful equipment and stronger tooling are required
Less ductility is available
Undesirable residual stresses may be produced

Question 16

warm forming? adv?

Answer 16

Deformations produced at temperatures intermediate to cold and hot working

Advantages
◦
Reduced loads on the tooling and equipment
◦
Increased material ductility
◦
Possible reduction in the number of anneals

Better dimensional precision and smoother surfaces than hot working
◦
Used for processes such as forging and extrusion

Question 17

Isothermal Forming

Answer 17

Deformation that occurs under constant
temperature
Dies and tooling are heated to the same
temperature as the workpiece
Eliminates cracking from
nonuniform surface
temperatures