Chapter 13 - Bulk Deformation Processes in Metal Working

Question 1

What are the reasons why the bulk deformation processes are important commercially and technologically?

Answer 1

1) They are capable of significant shape change when hot working is used.
2) They have a positive effect on part strength when cold working is used.
3) Most of the processes produce little material waste.

Question 2

Name the four basic bulk deformation processes.

Answer 2

Rolling, forging, extrusion, wire and bar drawing.

Question 3

What is rolling in the context of the bulk deformation processes?

Answer 3

Rolling is a deformation process in which the thickness of the workpiece is reduced by compressive forces exerted by two opposing rolls. The rolls rotate, thus pulling and simultaneously squeezing the workpiece between them.

Question 4

In rolling of steel, what are the differences between a bloom, a slab and a billet?

Answer 4

A bloom is a rolled steel piece with a square cross section of 150mm by 150mm.
A slab is rolled from a bloom and has a rectangular cross section of about 250mm by 40mm.
A billet is rolled from a bloom and has a square cross section of 40mm by 40mm.

Question 5

List some of the products produced on a rolling mill.

Answer 5

Rolled products include flat sheet and plate stock, round bar and rod stock, rails, structural shapes such as I-beams and channels.

Question 6

What is draft in a rolling operation?

Answer 6

The difference between the starting thickness and the final thickness as the workpiece adheres to the rolls as the piece passes between the rolls, causing severe deformation of the metal below the surface in order to allow passage through the roll gap.

Question 7

What is sticking in a hot rolling operation?

Answer 7

Sticking is a condition in hot rolling in which the surface of the workpiece adheres to the roll as the piece passes between the rolls, causing severe deformation of the metal below the surface in order to allow passage through the roll gap.

Question 8

Identify some of the ways in which force in flat rolling can be reduced.

Answer 8

1) Use hot rolling
2) Reduce draft in each pass
3) Use smaller diameter rolls

Question 9

What is a two-high rolling mill?

Answer 9

Two opposing rolls between which the work is compressed.

Question 10

What is a reversing mill in rolling?

Answer 10

A reversing mill is a two high rolling mill in which the direction of the rolls can be reversed to allow the work to pass through from either side.

Question 11

Besides flat rolling and shape rolling, identify some additional bulk forming processes that use rolls to effect the deformation.

Answer 11

Ring rolling, thread rolling, gear rolling, roll piercing, roll forging.

Question 12

What is forging?

Answer 12

A deformation process in which the workpiece is compressed between two dies, using impact or gradual pressure to form the part.

Question 13

One way to classify forging operations is by the degree to which the work is constrained in the die. Name the three basic types.

Answer 13

1) Open die forging
2) Impression die forging
3) Flashless forging

Question 14

Why is flash desirable in impression die forging?

Answer 14

Because its presence constrains the metal in the die to fill the details of the die cavity.

Question 15

What is a trimming operation in the context of impression die forging?

Answer 15

A shearing operation used to remove the flash on the workpiece after impression die forging.

Question 16

What are the two basic types of forging equipment?

Answer 16

Hammers - which impact the workpart

Presses - which apply a gradual pressure to the work.

Question 17

What is isothermal forging?

Answer 17

A hot forging operation in which the die surfaces are heated to reduce heat transfer from the work into the tooling.

Question 18

The starting workpiece in steel hot rolling of plate and sheet stock is which of the following:

a) Bar stock
b) Billet
c) Bloom
d) Slab
e) Wire stock

Answer 18

d

Question 19

The maximum possible draft in rolling operation depends on which of the following:

a) Coefficient of friction between roll and work
b) Roll diameter
c) Roll velocity
d) Stock thickness
e) Strain
f) Strength coefficient of the work metal

Answer 19

a, b

Question 20

Which of the following stress or strength parameters is used in the computation of rolling force:

a) Average flow stress
b) Compression strength
c) Final flow stress
d) Tensile strength
e) Yield strength

Answer 20

a

Question 21

Which of the following rolling mill types are associated with relatively small diameter rolls in contact with the work.

a) Cluster mill
b) Continuously rolling mill
c) Four-high mill
d) Reversing mill
e) Three-high configuration

Answer 21

a, c

Question 22

Production of pipes and tubes is associated with which of the following bulk deformation processes:

a) Extrusion
b) Hobbing
c) Ring rolling
d) Roll forging
e) Roll piercing
f) Tube sinking
g) Upsetting

Answer 22

a, e, f

Question 23

Which of the following stress or strength parameters is used in the computation of the maximum force in a forging operation:

a) Average flow stress
b) Compression strength
c) Final flow stress
d) Tensile strength
e) Yield strength

Answer 23

c

Question 24

Which of the following operations are closely related to open-die forging?

a) Cogging
b) Flashless forging
c) Fullering
d) Impression die forging
e) Mannesmann process
f) Precision forging
g) Soaking
h) Upsetting

Answer 24

a, c, h

Question 25

Flash in impression die forging serves no useful purpose and is undesirable because it must be trimmed from the part after forming:

a) True
b) False

Answer 25

False

Question 26

Which of the following bulk deformation processes are involved in the production of nails for lumber construction:

a) Bar and wire drawing
b) Extrusion
c) Flashless forging
d) Impression die forging
e) Rolling
f) Upsetting

Answer 26

a, c, d