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Having trouble understanding the iron-carbon phase diagram
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Mowarin Emmanuel
Having trouble understanding the iron-carbon phase diagram
For any steel with less than 0.02% carbon we should see only ferrite, and for steel with >0.02% carbon we should see only pearlite.
You have got a small misunderstanding here. The maximum solubility of carbon at $723\ \mathrm{^\circ C}$ is 0.02%. At room temperature it is very low ($0.005%$ at $0\ \mathrm{^\circ C}$). Also for carbon level between 0.02 and 0.8 you wont see only pearlite, you will see a combination of ferrite and pearlite for sure. Only at 0.8% you can observe pure pearlite(100%). Also note that the phase diagram is in such a way that if you cool from the ferrite+ austenite region at $800\ \mathrm{^\circ C}$ with carbon content < 0.02% we can still get a ferrite + pearlite + even austenite/martensite.
Phase diagrams give an ideal picture. In real situations, it is very tough to get very slow cooling rates to get the equilibrium structure.
For any steel with less than 0.02% carbon we should see only ferrite, and for steel with >0.02% carbon we should see only pearlite.
You have got a small misunderstanding here. The maximum solubility of carbon at $723\ \mathrm{^\circ C}$ is 0.02%. At room temperature it is very low ($0.005%$ at $0\ \mathrm{^\circ C}$). Also for carbon level between 0.02 and 0.8 you wont see only pearlite, you will see a combination of ferrite and pearlite for sure. Only at 0.8% you can observe pure pearlite(100%). Also note that the phase diagram is in such a way that if you cool from the ferrite+ austenite region at $800\ \mathrm{^\circ C}$ with carbon content < 0.02% we can still get a ferrite + pearlite + even austenite/martensite.Phase diagrams give an ideal picture. In real situations, it is very tough to get very slow cooling rates to get the equilibrium structure.
The phase diagram shows two phases, ferrite/iron, and iron carbide . It does not define the morphology; the form of the carbide. It could be in particles although we usually find the carbide in layers/ lamellae = pearlite ( with typical air cooling). Cooling rates , reheating and other thermal ( and mechanical) actions will have profound influence of the microstructures. TTT diagrams or Isothermal Transformation Diagrams explain the affect of cooling rates but they may be more than you want.
The phase diagram shows two phases, ferrite/iron, and iron carbide . It does not define the morphology; the form of the carbide. It could be in particles although we usually find the carbide in layers/ lamellae = pearlite ( with typical air cooling). Cooling rates , reheating and other thermal ( and mechanical) actions will have profound influence of the microstructures. TTT diagrams or Isothermal Transformation Diagrams explain the affect of cooling rates but they may be more than you want.
You have got a small misunderstanding here. The maximum solubility of carbon at $723\ \mathrm{^\circ C}$ is 0.02%. At room temperature it is very low ($0.005%$ at $0\ \mathrm{^\circ C}$). Also for carbon level between 0.02 and 0.8 you wont see only pearlite, you will see a combination of ferrite and pearlite for sure. Only at 0.8% you can observe pure pearlite(100%). Also note that the phase diagram is in such a way that if you cool from the ferrite+ austenite region at $800\ \mathrm{^\circ C}$ with carbon content < 0.02% we can still get a ferrite + pearlite + even austenite/martensite. Phase diagrams give an ideal picture. In real situations, it is very tough to get very slow cooling rates to get the equilibrium structure.
You have got a small misunderstanding here. The maximum solubility of carbon at $723\ \mathrm{^\circ C}$ is 0.02%. At room temperature it is very low ($0.005%$ at $0\ \mathrm{^\circ C}$). Also for carbon level between 0.02 and 0.8 you wont see only pearlite, you will see a combination of ferrite and pearlite for sure. Only at 0.8% you can observe pure pearlite(100%). Also note that the phase diagram is in such a way that if you cool from the ferrite+ austenite region at $800\ \mathrm{^\circ C}$ with carbon content < 0.02% we can still get a ferrite + pearlite + even austenite/martensite.Phase diagrams give an ideal picture. In real situations, it is very tough to get very slow cooling rates to get the equilibrium structure.
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The phase diagram shows two phases, ferrite/iron, and iron carbide . It does not define the morphology; the form of the carbide. It could be in particles although we usually find the carbide in layers/ lamellae = pearlite ( with typical air cooling). Cooling rates , reheating and other thermal ( and mechanical) actions will have profound influence of the microstructures. TTT diagrams or Isothermal Transformation Diagrams explain the affect of cooling rates but they may be more than you want.
The phase diagram shows two phases, ferrite/iron, and iron carbide . It does not define the morphology; the form of the carbide. It could be in particles although we usually find the carbide in layers/ lamellae = pearlite ( with typical air cooling). Cooling rates , reheating and other thermal ( and mechanical) actions will have profound influence of the microstructures. TTT diagrams or Isothermal Transformation Diagrams explain the affect of cooling rates but they may be more than you want.
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