Thermal Processing

1
Thermal Processing

• Annealing
• Thermal exposure to elevated temperature for
  generally long periods of time
• A need for
• Removing defects from processing and from damaged
  structures
• removing residual stresses and strains that arise
  from differential cooling between the outside and
  inside of a structure

2
Annealing Terminology

• Critical Temperatures, based on phase boundaries
• Composition will affect the formation
  temperatures of the different phases
• Normalizing the growing of new, small grains
  out of elongated ones from deformation processing
• Austenizing Formation of all austenite

3
Heat Treatment for Steel Hardening

• Heat treatment that forms a martensite
• A function of alloy composition, quenching
  medium, and specimen dimensions
• End Quench testing
• Hardenability curves
• Alloy compositions are much more important in
  forming really hard materials

4
Quenching Medium

• It should make sense that the quenching medium
  has a controlling influence on the rate of heat
  extraction on a specimen surface
• The largest issue with fluid heat extraction is
  the boiling point of the fluid

5
Precipitation Hardening

• There are phase diagrams that have potential for
  the precipitation of a hardened phase following a
  quenching and annealing procedure
• The precipitation of a new (harder) phase results
  if there is a decreased level of solid solubility
  for the new phase.