Question: What are the limitations of Plain Carbon Steel? Explain the effect of alloying elements on phase transformation
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Subject: Material Technology

Topic: Effect of alloying Element on Steel

Difficulty: High

mt(63) • 364 views
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modified 11 months ago  • written 11 months ago by gravatar for Atharv Inamdar Atharv Inamdar650
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  1. Mild steel which is very commonly used steel for various application consists only 0.05 to 0.32% carbon content.
  2. It is relatively cheap and easy to handle and easy to use for fabrication purpose.
  3. Though it has some limitations which are as follows:
  • There cannot be strengthening beyond about 100000 psi without significant loss in toughness (impact resistance) and ductility.
  • Large sections cannot be made with a martensite structure throughout, and thus are not deep hardenable.
  • Rapid quench rates are necessary for full hardening in medium-carbon leads to shape distortion and cracking of heat-treated steels.
  • Plain-carbon steels have poor impact resistance at low temperatures. They have poor corrosion resistance for engineering problems.
  • Plain-carbon steel oxidizes readily at elevated temperatures.

Effects of the alloying element are given as follows:

  • Austenite stabilizers such as Nickel, Manganese, Copper and Nitrogen tend to raise temperatures A4 temperature and lower A1 and A3 temperature as a result of which more austenite region is present in the above diagram as compared to ferrite region. These elements are more stable in austenite region of steel.
  • Ferrite stabilizers such as Chromium, Tungsten, Vanadium, Molybdenum, Silicon and Aluminum more stable in ferrite region. By addition of these elements into the steel the proportion of ferrite region increases by reducing the area occupied by austenite region in the iron-iron equilibrium diagram.
  • If the proportion of these elements increases there forms a gamma loop by joining A4 and A3 temperatures. In this phase Ferrite exists from room temperature to melting point of steel.

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modified 11 months ago  • written 11 months ago by gravatar for Atharv Inamdar Atharv Inamdar650
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