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As with conventional quench and tempering the material being heat treated must be cooled from the austenitizing temperature quickly enough to avoid the formation of pearlite. The specific cooling rate that is necessary to avoid the formation of pearlite is a product of the chemistry of the austenite phase and thus the alloy being processed.
Conversely, at higher coiling temperatures, pearlite forms with coarser lamellae, and a smaller amount of pearlite is observed as coarse cementite particles tend to dominate the structure. The carbon diffusion during the formation of pearlite, just ahead of the growth front, is critical in determining the thickness of the lamellae and ...
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. [5]
Slow cooling rates allow for the development of coarse cementite particles at grain boundaries, while faster cooling rates promote the formation of fine pearlitic colonies. Coiling temperature, in particular, has a significant impact on carbide morphology: lower coiling temperatures (below the eutectoid temperature) promote fine pearlite ...
The morphology of cementite plays a critical role in the kinetics of phase transformations in steel. The coiling temperature and cooling rate significantly affect cementite formation. At lower coiling temperatures, cementite forms fine pearlitic colonies, whereas at higher temperatures, it precipitates as coarse particles at grain boundaries.
In materials science, lamellar structures or microstructures are composed of fine, alternating layers of different materials in the form of lamellae. They are often observed in cases where a phase transition front moves quickly, leaving behind two solid products, as in rapid cooling of eutectic (such as solder ) or eutectoid (such as pearlite ...
Austenite is slightly undercooled when quenched below Eutectoid temperature. When given more time, stable microconstituents can form: ferrite and cementite. Coarse pearlite is produced when atoms diffuse rapidly after phases that form pearlite nucleate. This transformation is complete at the pearlite finish time (P f).
The temperature range lies between the minimum and maximum operating temperature of the element. Elements can cover temperatures ranging from -15 °C to +120 °C. Elements may move in proportion to the temperature change over some part of the range, or may open suddenly around a particular temperature depending on the composition of the waxes.