Cold Rolling

Question 1

elastic deformation

Answer 1

it is temporary change in the the shape of a material when a load is applied. the object return to its original shape on removal of the load

Question 2

plastic deformation

Answer 2

this type of deformation is not reversible. in this case the material retains the deformed shape even after the removal of the load

Question 3

anisotropic

Answer 3

a material not possessing the same properties in all directions

Question 4

isotropic

Answer 4

a material possessing the the same properties in all directions

Question 5

the microstructural and mechanical characteristics of a _________plastically deformed metal specimen may be restored to their predeformed states by appropriate heat treatment, during which ____ processes are allowed to occurr

Answer 5

plastically deformed metal specimen……. recovery, recrystallization and grain growth

Question 6

during_____ there is a reduction in dislocation density and alterations in dislocation configurations

Answer 6

recovery

Question 7

define recrystallization

Answer 7

is the formation of a new set of grains that are stain free, in addition the material becomes softer and more ductile

Question 8

grain growth

Answer 8

is the increase in average size of polycrystalline materials, which proceeds by grain boundary motion

Question 9

work hardening/strain hardening

Answer 9

an increase in hardness and strength caused by plastic deformation at temperature below the plastic deformation range

Question 10

define metal forming

Answer 10

large group of manufacturing processes in which plastic deformation is used to change the shape of metal work-pieces

Question 11

what is the tool usually used in metal forming?

Answer 11

die

Question 12

give examples of stresses that plastically deform a metal

Answer 12

rolling, forging, extrusion

Question 13

the plastic deformation of metals _____ ; its important to note, however, that the recrystallization temperature varies greatly with different materials

Answer 13

above their recrystallization temperature

Question 14

elevated temperatures bring about a ______ in the yield strength of a metal and an ___ in ductility

Answer 14

decrease yield strength, increase in ductility

Question 15

at the temperatures of hot working

Answer 15

recrystallization eliminates the effects of strain hardening

elevated temperature promotes diffusion

Question 16

hot rolling

Answer 16

a material is passed trough two rolls that rotate opposite directions and the gap is smaller than the material

Question 17

forging

Answer 17

is mechanically working or deforming a single piece of metal this may be accomplished by the application of successive blows or by continuous squeezing

Question 18

extrusion

Answer 18

a bar of metal is forced through a die orifice by a compressive force that is applied to a ram; the extruded piece that emerges has the desired shape and reduced cross-sectional area

Question 19

drawing

Answer 19

is the pulling of a metal piece through a die having a tapered bore by means of a tensile force that is applied on the exict side. a reduction in cross section results, with a corresponding increase in length

Question 20

name hot working advantages over cold working

Answer 20

work-piece shape can be significantly altered

lower forces and power required

metals that usually fracture in cold working can be hot formed

strength properties of product are generally isotropic

no strengthening of part occurs from work hardening

Question 21

name hot working disadvantages

Answer 21

lower dimensional accuracy

higher total energy required

work surface oxidation, poorer surface finish

shorter tool life

Question 22

plastic deformation of metals

Answer 22

below the recrystallizations temperature

Question 23

Name and define 4 cold working processes

Answer 23

Squeezing/Cold Rolling
Pin a material between to solid objects and cause plastic deformation.

Bending
Is the plastic deformation of materials about a linear axis with little or no change in the surface area.

Shearing/Blanking
Is the mechanical cutting of materials without the formation of chips or the use of burning or melting.

Drawing
Sheet metal
The forming of parts where plastic flow occurs over a curved axis.
Wire/Rod/Tubing
A process of reducing the cross section of the material by pulling it through a die.`

Question 24

cold working advantages over hot working

Answer 24

no heat required

strength, fatigue, and wear properties are improved, superior dimensional control is achieved, better surface finished

directional properties can be imparted

contamination is minimized

Question 25

What are cold working disadvantages

Answer 25

high force are required to initiate and complete deformation

less ductility is available

heavier and more powerful equipment is required

metal surfaces mus be clean and scale- free

undesirable residual stresses may be produced

imparted directional proerties are detrimental

in som cases, metal may not be ductile enough to do cold working

intermediate anneals may be required to compensate for the loss of dcutility ath accompanies strain hardening

Question 26

A materials become more ____ as it is cold worked.

Answer 26

brittle

Question 27

deformation produced at temperatures ____

Answer 27

intermediate to hot and cold working

Question 28

compared to hot forming, the lower temperatures of warm working produce _____ an enable production of products with _____

Answer 28

produce less scaling……. better dimensional precision and smoother surfaces

Question 29

compared to cold working, it offers the advantages of

Answer 29

reduced loads

Question 30

warm working

Answer 30

tools last longer

Question 31

The warm regime generally requires less energy than hot working due to the decreased energy in heating the workpiece, ______ through high precision and the possible elimination of postforming heat treatments

Answer 31

energy saved

Question 32

when _____ a piece of cold rolled material the ___-

Answer 32

blanking/cutting

orientation of the cold rolled direction should be noted