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A cooling curve of naphthalene from liquid to solid. A cooling curve is a line graph that represents the change of phase of matter, typically from a gas to a solid or a liquid to a solid. The independent variable (X-axis) is time and the dependent variable (Y-axis) is temperature. [1] Below is an example of a cooling curve used in castings.
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. The actual cooling rate is a product of both the quench severity, which is influenced by quench media, agitation, load (quenchant ratio, etc.), and the thickness and geometry of ...
There are two types of continuous cooling diagrams drawn for practical purposes. Type 1: This is the plot beginning with the transformation start point, cooling with a specific transformation fraction and ending with a transformation finish temperature for all products against transformation time for each cooling curve.
Diffusional transformations like austenite transforming to a cementite and ferrite mixture can be explained using the sigmoidal curve; for example the beginning of pearlitic transformation is represented by the pearlite start (P s) curve. This transformation is complete at P f curve. Nucleation requires an incubation time.
A moderate cooling rate forms a more pearlitic matrix, while a fast cooling rate forms a more ferritic matrix. To achieve a fully ferritic matrix the alloy must be annealed . [ 1 ] [ 11 ] Rapid cooling partly or completely suppresses graphitization and leads to the formation of cementite , which is called white iron .
English: Example of a cooling curve of a pure metal or eutectic alloy, with various aspects pointed out. Based on image from Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4 .
English: The cooling curve and phase diagram of an alloy; in this case a copper/nickel alloy. Based on a diagram from Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.
Eutectic alloys for soldering, both traditional alloys composed of lead (Pb) and tin (Sn), sometimes with additional silver (Ag) or gold (Au) — especially Sn 63 Pb 37 and Sn 62 Pb 36 Ag 2 alloy formula for electronics - and newer lead-free soldering alloys, in particular ones composed of tin, silver, and copper (Cu) such as Sn 96.5 Ag 3.5.