The Fundamentals of Metalworking (PDF)

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Recrystallisation during hot working • The minimum temperature at which reformation of the crystals occurs is called Recrystallisation Temperature. • Above the recrystallisation temperature the kinetic energy of atoms increases and therefore they are able to attach themselves to the newly formed nuclei which in turn begin to grow into crystals. This process continues until all the distorted crystals have been transformed. • Hot working results in grain refining. Deformed in direction of work Nuclei form at grain boundaries at points of max stress Nuclei grow into new grains Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Recrystallisation • Recrystallisation takes place at higher temperatures than recovery which leads to a new formation of grains. • The process includes 1) primary recystallisation and 2) secondary recrystallisation and grain growth. Primary recrystallisation www.msm.cam.ac.uk Recrystallised grains with annealing twins - Primary recrystallisation occurs at the beginning of the new grain formation process. - Recrystallisation temperature does not depend on the metal alone, but on a whole number of variables temperature, strain and minimum dislocation density available (amount of deformation) - Small impurities in pure metals can considerably increase the recrystallisation temperature. Deformed matrix Recrystallised grain with annealing twins surrounded by deformed matrix with high density of dislocations. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Page 1 and 2: Fundamentals of metalworking Subjec
Page 3 and 4: Classification of metal forming pro
Page 5 and 6: • Tension type processes: the app
Page 7 and 8: Mechanics of metal working • Meta
Page 9 and 10: • However the convention is rever
Page 11 and 12: Yield criteria and stress-strain st
Page 13 and 14: Tresca yield criterion Yielding occ
Page 15 and 16: FEM analysis • Finite element met
Page 17 and 18: Determination of flow curve Stress-
Page 19 and 20: Flow curve • Strain hardening occ
Page 21 and 22: • The products resulting from the
Page 23: Effects of temperature on metal for
Page 27 and 28: Effects of grain size and strain on
Page 29 and 30: Effects of strain rate and temperat
Page 31 and 32: Polygonization Recovery • Recover
Page 33 and 34: Static and dynamic changes of struc
Page 35 and 36: Advantages and disadvantages of hot
Page 37 and 38: Advantages and disadvantages of col
Page 39 and 40: Increasing reduction Effects of met
Page 41 and 42: Effect of principal stresses in met
Page 43 and 44: Effects of friction and lubrication
Page 45 and 46: σσσσ σσσσ Example : homogen
Page 47 and 48: Effect of residual stresses • Res
Page 49 and 50: Workability • Workability is conc

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