Hardening And Metals Processing Flashcards
What is grain size hardening?
Reducing grain size increase the number of grain boundaries, therefore harder to plastically deform because more energy required to overcome grain boundary
How does yield strength relate to grain size?
Proportional to the inverse square of the grain size
What is cold working/work hardening?
Plastically deform the material, let go, the material will absorb some energy and when you try to deform the material again the yield strength would have increased
What is annealing?
A process for hypoeutectoidic steel, heat to 30 degrees above solidus line, keep it there until entire temp is uniform, then Cool down slowly in furnace, increases ductility
What is normalising?
For both hypo and hyper eutectic steel, heat to 50 degrees above solidus curve, keep it there until temperature is uniform, cool in air. Produces fine pearlite
What is process annealing?
Removes the effect of cold working by making the component more ductile, heat to above cold working temp and below 700 degrees, the grain size will grow, removing internal stresses produced by cold working
What is precipitation hardening?
Heat in ferrite region until it becomes homogeneous, quench to room temp, reheat to low temp below solidus line, keep there long enough in order to produce fine precipitates inside of metal. These precipitates increase strength and hardness because it is harder for dislocations to pass over them
What is hardenability?
To form a martensite layer at the surface during quenching
What is the jominy and quench test?
Heated to austenite region until homogeneous, the bottom of the specimen is cooled very fast to form a martensite layer
What is surface hardening?
Heat locally on the surface, the core remains perlite and ferrite, but the surface becomes tempered martensite
What is induction hardening?
Heat to austenite region using magnetic induction, quench and surface forms martensite
What is carburising?
Kept in high temp carbon rich atmosphere, carbon diffuses intro the metal making the component harder
What is nitriding?
Kept in nitrogen rich atmosphere in furnace, nitrogen diffuses in, forming different nitrates at the surface , improving strength, hardness and corrosion resistance, quenched in oil
What is nitrocarburizing?
Combination of carburising and nitriding
What’s die casting?
Molten metal is injected into cast
