Heat Treatments Flashcards
What is metal hardening?
Alloys being heated above critical transformation temperature of material, then cooled rapidly to cause soft initial material to be harder and stronger
What is case hardening?
Using a low carbon metal and combining it with a higher carbon metal, producing a harder metal that can be easily moulded
What is precipitation hardening? What are the three steps of this?
Heating alloying materials (ie Al & Ti) at low temperatures
Solution annealing, quenching and ageing
What is quenching? What are some typical quenching agents?
Rapid cooling of a part until solubility limit is exceeded (alloys can’t discharge)
Water, oil and gas
What is ageing?
Heating a solution to an intermediate temperature so the oversaturated solid solution transforms into two-phase alloys
What is tempering?
Reheating a steel at a relatively low temperature that causes precipitation and spheroidisation of carbides in the steels’ microstructure
What is the primary purpose of annealing?
To make a metal softer and more workable as it reduces the risk of fracture, cracking and distortion
What are three properties of steel?
Strong
Corrosion resistant
Hard
What are three properties of copper?
Ductile
Good electrical conductor
Malleable
What are smart materials?
Materials that when deformed return to their original shape (shape memory alloys)
What does metal hardening do?
Makes a material harder
What are three properties of iron?
Soft
Malleable
Easily magnetised
What are the steps for heat treating low carbon (0.4) steel?
Heat furnace to 600 - 900 °C for 15 mins/ till red hot
To normalise allow metal to cool at room temperature
To (water) quench agitate metal in water until bubbles stop
To (oil) quench place metal in oil
To anneal turn off furnace and leave metal to cool inside
