Quiz7Sp02 - f+ ENSC 3313, Spring 2002 Answer any 4...

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f+ 11 ENSC 3313, Spring 2002 Quiz 7 Name Answer any 4 Questions onlv, 1 point each What steel composition, w/o C, does this microstructure correspond to? Explain! This is a ferrite-pearlite microstructure. I estimate ~ 3/8 pearlite, so -0.3 w/oC. Liquid ~ I-JOjuid 1200 -~ I ~ .3] ~ J ..,0 1~ 1~ 141X1 ~ 8): 7 ~ 5 ~ I A-~- 1600 f 1W l XXl 800 400 2"/. nital SOOx Wti&bi ~ -bon 2. Explain how we could obtain at room temperature, by cooling from austenite, a microstructure of a 0.8% C steel that is a) 100% spheroidite, b) 100% ~ pearlite, c) 100% bainite, d) 100% martensite. a) Cool slow.y 'til ~ 700°C to get coarse pearlite, then hold for (say) 50 hours to spheroidize the Fe3C, thence cool to room temp. b) Let the y transform near the "nose" then cool to room temp. c) Quench the y to -300°C and hold 'til it has transfonned to bainite, say > 1000s; then, cool to rQom temp. d) Water quench the y to below Mr (- -50°C) and then wann to room temp. Shown are two microstructures for the same steel. How would you convert a) A to B. b) B to A?
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Quiz7Sp02 - f+ ENSC 3313, Spring 2002 Answer any 4...

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