Chapter 26 Flashcards
Define: Annealing
Heating a metal to a suitable temperature, holding it at that temperature for a certain time (soaking), and slowly cooling. It is performed to reduce hardness, improve form-ability, and relieve cold-worked metals.
Define: Soaking
Holding a metal at a high temperature for a certain time. Component of annealing.
Define: Normalizing
Involves similar heat and soaking cycles to produce fine pearlite with higher strength and hardness but lower ductility than the full anneal treatment.
Define: Full vs Process vs. Stress-Relief Anneal
Full: heating alloy into austenite region, followed by slow cooling in the furnace to produce coarse pearlite.
Process: When annealing occurs to allow for futher cold working of the metal.
Stress-Relief: Annealing to relieve residual stresses in a metal. reduces distortional and dimensional variations.
Define: Recrystallization
If annealing conditions permit full recovery of the cold-worked metal to its original grain structure.
Define: Martensite
Hard, brittle phase that gives steel its unique ability to be strengthened to very high levels.
Define: Pearlite
Mixture of ferrite and carbide phases in the form of thin parallel plates. Obtained by slow cooling of austenite.
Define: Bainite
Same mixture of ferrite and carbide but produced by initial rapid cooling and later slow cooling; appears in feather-like regions.
Define: Austenitizing
Heating steel to a sufficiently high temperature so that it is converted entirely or partially to austenite, as determined by its phase diagram.
Define: Quenching
Cooling austenite rapidsy enough to avoid passing through the nose of the TTT curve, as indicated in the phase diagram.
Define: Tempering
Used ot harden steels to reduce brittleness, increase ductility and toughness, and relieve stresses in the martensite structure. Involves heating and soaking at a temperature just below the austenite region.
Define: Jominy End Quench Test
Hardenability test done by heating a standard specimen into the ausenite range, then quenching one end with water. The cooling rate decreases with distance from quenched end. Rockwell hardness is then measured at all points along test specimen.
Define: Hardenability
the relative capacity of a steel to be hardened by transformation to martensite.
Define: Precipitation Hardening
Involves the formation of fine particles (precipitates) that act to block the movement of dislocations and thus strengthen and harden the metal. Metal is heated to temperature below T_s.
Define: Carburizing
Heating a part of low carbon steel in the presence of carbon-rich environment so that C is diffused into the surface. Increases hardness
