7-Engineering Alloys

7-Engineering Alloys - STEEL IRON CARBON ALLOYS NEAR...

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STEEL: IRON - CARBON ALLOYS NEAR EQUILIBRIUM Casting of Steel Ingots
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Modern Blast Furnace Conversion of Iron-oxide to produce pig iron. Fe 2 O 3 + 3 CO 2 Fe (~ 4 wt .% C ) + 3 CO 2 Operation of Basic-Oxygen Furnace 2 Fe (~ 4 wt .% C ) + O 2 FeO Fe ( < 0.1% C ) + CO
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Reduction in carbon content of the steel in about 22 minutes along with a reduction in the concentration of impurities such as sulfur and phosphorus. Mechanical Processing of Steel Products
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Hot Rolling of Steel Strip The Iron-Carbon Phase Diagram
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IRON - IRON CARBIDE PHASE DIAGRAM Iron with up to 6.67%C (Fe 3 C) Contains 3 invariant reactions: peritectic (L + δ γ ) eutectic (L γ + Fe 3 C ) eutectoid ( γ α + Fe 3 C ) IRON - IRON CARBIDE PHASE DIAGRAM CONTAINS Ferrite (alpha) Interstitial solid solution of carbon in BCC iron Low temperature phase Maximum solubility of 0.02% carbon at 723ºC Solubility at 0ºC is 0.005% carbon
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IRON - IRON CARBIDE PHASE DIAGRAM CONTAINS Austenite (gamma) Interstitial solid solution of carbon in FCC iron Maximum solubility of 2.08 % carbon at 1148ºC High temperature phase of steel Exists above 723ºC IRON - IRON CARBIDE PHASE DIAGRAM CONTAINS Cementite (Fe 3 C) Intermetallic compound iron-carbide negligible solubility limits composition of 6.67 % carbon and 93.3 % iron hard and brittle compound
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IRON - IRON CARBIDE PHASE DIAGRAM CONTAINS Ferrite (delta) Interstitial solid solution of carbon in BCC iron Maximum solubility of 0.09 % carbon at 1495ºC Very high temperature phase exists above 1400ºC PERITECTIC REACTION Liquid (0.53 % C) + Delta Ferrite (0.09 % C) Austenite (0.17 % C) 1495ºC
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EUTECTIC REACTION Liquid (4.3 %C) Austenite (2.08 %C) + Fe 3 C (6.67 %C) 1148ºC Basis for cast irons EUTECTOID REACTION Austenite (0.77 [~0.8] %C) Alpha Ferrite (0.02 %C) + Fe 3 C (6.67 %C) 723ºC Basis for steels
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EUTECTOID STEELS Eutectoid steels contain 0.8 % carbon Hypoeutectoid steels contain less than 0.8 % carbon Hypereutectoid steels contain more than 0.8 % carbon SLOW COOLING OF PLAIN CARBON STEELS Eutectoid plain carbon steels Austenitizing heating into the austenite phase region (above 723ºC) Cooling causes the austenite to transform from austenite to ferrite and cementite Pearlite the morphology of alternative layers of alpha ferrite and iron carbide
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HYPOEUTECTOID PLAIN CARBON STEELS Slow cooling from austenite phase produces . Austenite Proeutectoid Ferrite + Pearlite HYPOEUTECTOID PLAIN CARBON STEELS Slow cooling from austenite phase produces Proeutectoid ferrite - nucleates and grows at austenite grain boundaries.
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7-Engineering Alloys - STEEL IRON CARBON ALLOYS NEAR...

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