One finds a diagram of steel below, based on which he designs a manufacturing pr

Question

One finds a diagram of steel below, based on which he designs a manufacturing process. Step one: heat the steel to 800°C, keep at this temperature for long enough time to reach equilibrium; Step two: salt bath at 600°C for 5 seconds; Step 3: quench to room temperature. What type of steel he would make? 800 Eutectoid temperature A Austenite (stable) 700 Coarse pearlite RIC 15 P- Pearlite P Medium pearlite RIC 30 600 Fine pearlite RiC 40 Upper or feathery bainite RIC 40 1000 500 Nose B- Bainite Ending Lower or acicular bainite RIC 60 300Austenite (unstable) Beginning M(start) 50% 50% M+AM-A 50 ng0 M(50%) M(90%) 100 M- Martensite RiC 64 10 10 10 13 104105 Time (s) Isothermal-Transformation Diagram for a 1080 Eutectoid Steel austenite mixture of austenite and pearlite. mixture of austenite and bainite. medium pearlite.

Explanation / Answer

Answer is mixture of austenite and pearlite.

At 800 degree Celsius it is fully austenure. Now it is brought to 600 oC for 5s, there by transforming aboutv40 % of austenite to pearlite. Now on rapid cooling to room temperature the remaining austenite has to transform into martensite. But in option it is not given Hence option 3 is the best choice.

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