COLD Rolling (Working)

Question 1

Anisotropic

Isotropic

Answer 1

Anisotropic: material without same properties in all directions
Isotropic: material with same properties in all directions

Question 2

Processes which allow microstructural and mechanical characteristics of plastically deformed metal specimen to restore predefomed states

Answer 2

Recovery: reduction in dislocation in density and alterations in dislocation configurations
Recrystallization: formation of a new set of grains that are strain free making material softer and more ductile
Grain growth: increase in average grain size of polycrystalline materials which proceeds by grain boundary motion

Question 3

Work Hardening/Strain Hardening/Cold Working & Hot Working

Answer 3

Cold Working: increase in hardness and strength caused by plastic deformation at temperatures below the recrystallization range
Hot Working: deforming metal plastically at such a temperature and strain rate that recrystallization takes place simultaneously with the deformation avoiding any strain hardening

Question 4

Hot Working processes

Answer 4

hot rolling, forging, extrusion, hot drawing

Question 5

Cold Working Processes

Answer 5

squeezing/cold rolling, bending, shearing/blanking, drawing

Question 6

Cold Working vs. Hot Working

Answer 6

Advantages: no heating required, better surface finish, superior dimensional control is achieved, better reproducibility and interchangability in products; strength, fatigue and wear properties are improved through strain hardening; contamination problems minimized
Disadvantages: higher forces required to initiate and complete deformation; heavier and more powerful equipment required; metal surfaces must be clean and scale-free; loss of ductility from strain hardening may need to be compensated with intermediate anneals; undesirable residual stresses may be produced

Question 7

Strain Hardening

Answer 7

increasing amount of cold working will increase the yield strength, UTS, and reduce ductility making the material more brittle

Question 8

Grain changes due to deformation

Answer 8

the volume of the material must stay the same so as the area is reduced, the length is increased

Question 9

Anisotropic behavior of cold rolling

Answer 9

Hall Petch equation states that as the grains get smaller, the strength increases –> anisotropic
short longitudinal: along the major axis, long grains, less strenth
short transverse: along the width, small round grains, greater strength