Question

15. From the iron-carbon phase diagram (see Figure below) a. What are the concentrations of carbon in each a-ferrite and Fe3C at a temperature just below 727°C? b. What are the phases involved in the eutectoid reaction? c. I am making a hyper-eutectoid steel with 2 wt%C. If I cool slowly from 1400°C, what phases and microstructure will I have at room temperature, assuming only equilibrium phases can be present? d. What is the euctectoid composition for Fe-C system shown below? Composition (at%C) 10 15 1600 20 25 1538°C 1493°C L 1400 2500 1394°C y+L 1200 1147°C 2.14 4.30 Austenie 2000 Temperature (°C) 1000 Temperature (°F) 912°C Y+ Fezc 800 1500 + Y 727°C 0.76 0.022 a, Ferrite 600 a + Fogo Dementite (FeyC) 1000 400 0 (Fe) 1 5 6 6.70 Composition (wt% C)

Answer 1

for hyper Hyper eutectic b Solution @ at a temperature just below 727°C the percentage of carbon in each a-ferrite and Fesc o ranges from 0.022 % to 6.7Y for hypo eutectoid steel → 0.022% to 0.76 Y C ecetectoid steel 0076% to 2.147. c for eart son pearlite → 0.76%. for eutectic steel 4.3 % carbon Hypo eclectic 2.14 to 4.3% 4.3 to 6.77 Phase reaction of eutectoide reaction is given his during cooling Y-Austenite a-ferrite + Fesc solid solid 1 t solida. © when 2%. wt by c steel hyper eutectoid steel is cooled slowly from 1400°C tem to room temp we get solid phase mixture of L-Ferrite & fegc ma BCC microstructure. @ Bgm the eutectoid composition shown in diagram is 0.76 % Carbon in which formation takes place upon cooling below above 727°c we 727°C and upon heating and having peanlite recetion got Y- Austenite. CS Scanned with CamScanner