CCT Curves Explanation -Scroll down, please. -Do not copy and paste a whole answ

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CCT Curves Explanation

-Scroll down, please.

-Do not copy and paste a whole answer from the internet. In your own words and thank you kindly.

May I Please get help on one big question regarding CCT curves?.

(1)-Please elaborate on what is a CCT Curve.
-What is the difference between a CCT curve and a TTT curve?

(2)-On the 1st image, how did they come to the given statement?. Why do Ferrite and Pearlite share a common region?, how come they aren't in separate regions like the M and B (Martensite and Bainite).
-Lastly, what does the dashed thick line indicate?.

(3)-What type of microstructure and amount(%) would we have if we used 10mm of Air to quench it?. Most impotently how did you come to the results?. (the percent next to the start and Finnish are 10%, 50%, and 90%).

(4) - Please elaborate why the 2nd image has two areas with the 10, 50, 90% indicators and what dictates this.
-What would be the microstructure and amount for 20mm water, 2mm air, lastly 100mm oil?.

A big thank-you in advance!

N DIAGRAM AUSTENITISED AT 900 C PREVIOUS TREATMENT ROLLED 18' C (1017-1022) C Si Mn P S Cr MoNi A Nb V 0,18 0.20 0,45 0,020 0.020 ANALYSIS Wr% COOLING RATE AT 800 C 200 100 C PER MIN 10 20,000 10,000 ,000 2,000 1000 50 800 600 eC 400 300M 100 10 seconds 100 miutes 10 hours 00 1000 2000 mm mm OIL mm WATER 0 S1 50 100 200 AIR BAR DIAMETER 100 150 200 100 10 100 150 200 300 800 T HARDNESS AFTER TRANSFORMATION 700 60 600 500 HV 40 300 200 100 Figure 8a: A 10 mm thick 1018 plate quenched in water will produce approximately 92% Bainite and 8% Martensite. The hard ness would be approximately HRC 30

Explanation / Answer

1) In a TTT diagram the isothermal transformation for all range of temperature values are plotted first. I t is a S shaped curve and all these individual isotherm which also depicts the the time for 100%, 50 % transformation of austenite to pearlite; is compiled to form a single TRY diagram. In a CCT curve the transformation temperature is changing (practical) and plotted

(2) Below eutectoid temperature, when austenite is brought down to a temperature where pearlite is forming, and we maintain that condition we get pearlite transformed from 100% austenite to 50% austenite +50% pearlite. this is shown by dashed lunes.

Bainite is formed below the nose in TTT diagram.(215-540 oC. It is formed when austenite is cooled to this region and then transforms isothemally fully into Bainite after a period of time.

(3) The type of microstructure purely depends on the temperature from which you are cooling. eg: if are annealing eutectoid steel , you will get a pearlite with coarse microstructure.

(4) 10% means it has got the 10 percent of austenite transformed, 50 means 50 % to pearlite or Bainite or martensite, depending on temperature.

If u choose oil and water(quenching) you get done microstructure, and is hard.

sir cooling relieves stress and get a coarse grain structure

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