What is the definition of a heat treatment?
Heat treatments are thermal solid state operations in order to obtain specific microstructure and properties
What are the side effects of heat treatments?
geometric and dimensional variations
Surface modification
modification of the stress state
What are the phases of heat treatments and their temperature profile?
Heating
Soaking
Cooling
What are the operational variations of heat treatments?
variation between batch or continous furnaces
variation between atmospheres:
protective atmosphere
atmosphere delivering diffusive elements
air
What are the main process parameters in heating?
heating rate
Pre heating
atmosphere
What are the main parameters in soaking?
Temperature
time
What are the main parameters in cooling?
cooling rate
breaks in cooling
What are the effects of heat treatments?
phase transformations
recrystallization
grain growth
precipitation
stress relieving
What are the advantages of a salt bath furnace?
dramatically Higher heating rate
Which properties influence the heating process?
type of furnace
piece dimension
thermal properties
What are the process parameters of Annealing?
T: 750-800°C
Slow controlled cooling at 10-20°C/h
What are the process parameters of Hardening?
T:1050°C
15-30min holding time after heating
What is the rough difference in cooling time between water oil and air?
10
Cooling rate of water>oil>air
What can be the reason for distortion after heat treatment?
Nonuniform introduction of stresses through nonuniform shape or cooling
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