Akademija tehnicko-vaspitackih strukovnih studija u Nisu
Odsek Vranje
Seminarski rad
Predmet:
Engleski jezik II
Tema:
Fundamentals of manufacturing processes such as heat
treating
Profesor: Student:
Dr. Maja Stanojevic-Gocic Tasic Nemanja 338/DS-MI
Vranje, 2020.
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Content
Content......................................................................................................2
Heat treating (or heat treatment)................................................................3
Physical processes.....................................................................................4
Effects of composition...............................................................................5
Eutectoid alloys................................................................................5
Hypoeutectoid alloys........................................................................5
Hypereutectoid alloys.......................................................................6
Effects of time and temperature................................................................6
Techniques.................................................................................................8
1. Annealing.........................................................................................8
2. Normalizing......................................................................................9
3. Stress relieving.................................................................................9
4. Aging................................................................................................9
5. Quenching......................................................................................10
6.
Tempering.......................................................................................................11
7. Selective heat treating....................................................................12
8. Differential hardening....................................................................12
9. Flame hardening.............................................................................13
10. Induction hardening........................................................................13
11. Case hardening...............................................................................13
Literature.................................................................................................14
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When in the soluble state, the process of diffusion causes the atoms of the dissolved
element to spread out, attempting to form a homogenous distribution within the
crystals of the base metal. If the alloy is cooled to an insoluble state, the atoms of
the dissolved constituents (solutes) may migrate out of the solution. This type of
diffusion, called precipitation, leads to nucleation, where the migrating atoms group
together at the grain-boundaries. This forms a microstructure generally consisting
of two or more distinct phases. For instance, steel that has been heated above
the austenizing temperature (red to orange-hot, or around 1,500 °F (820 °C) to
1,600 °F (870 °C) depending on carbon content), and then cooled slowly, forms a
laminated structure composed of alternating layers of ferrite and cementite,
becoming soft pearlite. After heating the steel to the austenite phase and then
quenching it in water, the microstructure will be in the martensitic phase. This is
due to the fact that the steel will change from the austenite phase to the martensite
phase after quenching. Some pearlite or ferrite may be present if the quench did not
rapidly cool off all the steel.
Unlike iron-based alloys, most heat treatable alloys do not experience a ferrite
transformation. In these alloys, the nucleation at the grain-boundaries often
reinforces the structure of the crystal matrix. These metals harden by precipitation.
Typically a slow process, depending on temperature, this is often referred to as "age
hardening".
Many metals and non-metals exhibit a martensite transformation when cooled
quickly (with external media like oil,polymer,water etc.). When a metal is cooled
very quickly, the insoluble atoms may not be able to migrate out of the solution in
time. This is called a "diffusionless transformation." When the crystal matrix
changes to its low temperature arrangement, the atoms of the solute become
trapped within the lattice. The trapped atoms prevent the crystal matrix from
completely changing into its low temperature allotrope, creating shearing stresses
within the lattice. When some alloys are cooled quickly, such as steel, the
martensite transformation hardens the metal, while in others, like aluminum, the
alloy becomes softer.
