AHMEDABAD INSTITUTE OF TECHNOLOGY
PREPARED BY: SUBMITTED TO: PROF. I. J.Bhavasar NAME ENROLL. NO. PATEL DIVYESH 130020119559 13/ME/559 PATEL HARESH 130020119561 13/ME/561 PANDYA VAIBHAV 130020119552 13/ME/552 PATEL BHARGAV 130020119556 13/ME/556 PANCHAL SUNNY 130020119549 13/ME/549 KADIA POOJAN 130020119529 13/ME/529 SUBMITTED TO: PROF. I. J.Bhavasar
The Iron-Iron Carbide Phase Diagram Heat Treatment of Steel
Features Reactions Phases present L a ferrite Bcc structure Ferromagnetic Fairly ductile d Bcc structure Paramagnetic g austenite Fcc structure Non-magnetic ductile Fe3C cementite Orthorhombic Hard brittle Reactions Peritectic L + d = g Max. solubility of C in ferrite=0.022% Max. solubility of C in austenite=2.11% Eutectic L = g + Fe3C Eutectoid g = a + Fe3C
Microstructures a g
Steels Classification/Nomenclature Steel is an interstitial solid solution of carbon in iron. Theoretically steel has a maximum of 2.11% carbon. In practice, the amount of carbon rarely exceeds 0.8% Classification/Nomenclature Low carbon steels up to 0.2%C Medium carbon steels 0.2-0.4%C High carbon steels >0.4% C AISI 1020: Last two numbers indicate Amount of carbon :0.2%C 10 indicates plain carbon steel AISI 4340: 0.4%C 43 indicates alloy steel
Microstructural changes in steel on cooling for different compositions
Eutectoid steel
Hypoeutectoid steel
Hypereutectoid steel
Iron-Carbon (Fe-C) Phase Diagram Max. C solubility in iron = 2.11 wt% • 2 important Fe3C (cementite) 1600 1400 1200 1000 800 600 400 1 2 3 4 5 6 6.7 L g (austenite) +L +Fe3C a + L+Fe3C d (Fe) Co, wt% C 1148°C T(°C) 727°C = T eutectoid points -Eutectic (A): L Þ g + Fe3C A S R 4.30 -Eutectoid (B): g Þ a + Fe3C g Result: Pearlite = alternating layers of a and Fe3C phases 120 mm (Adapted from Fig. 9.27, Callister 7e.) 0.76 C eutectoid B R S Fe3C (cementite-hard) a (ferrite-soft)
Eutectoid Reactions (II) Contains an eutectic reaction and an eutectoid reaction
Peritectic Reactions Peritectic solid phase + liquid phase will together form a second solid phase at a particular temperature and composition upon cooling L + Reactions are slow as product phase will form at boundary between two reacting phases separating them Peritectics are not as common as eutectics and eutectiods. There is one in Fe-C system
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