EFFECTS OF ALLOYING ELEMENTS IN STEEL
EFFECTS OF ALLOYING ELEMENTS IN STEEL
CARBON (C)
Content:
• 0.15% - 0.30% (Mild steel)
Effects:
• Tensile strength and Hardness: Increases
• Ductility and Toughness: Decreases
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
SULPHUR (S)
Content:
• less than 0.05%
Effects:
• Reacts with iron to form FeS (Iron sulfide)
• FeS has low melting point (1200ºC)
• It causes “Hot shortness”
• Hot Shortness: Loss of ductility at higher temperature
• Reduces weldability but promotes chip formation.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
MANGANESE (Mn)
Content:
• Up to 1.65%
Effects:
• Combines with Sulphur - MnS
• Combines with Oxygen - MnO
• MnS and MnO reduces Sulphur and Oxygen which are removed as Slag
• Fracture Toughness and Yield strength - Increases
• Chances of Solidification cracking - Decreases.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
PHOSPHORUS (P)
Content:
• Up to 0.045%
Effects:
• Combines with Iron to form Fe3P
• Causes “Cold Shortness”
• Cold Shortness: Brittle at low temperature.
• Fracture Toughness and Ductility- Decreases
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
SILICON (Si)
Content:
• 0.05% - 0.3%
Effects:
• Acts as a killing Agent, promotes deoxidation by
forming SiO2 (Remove oxygen from melt)
• Promotes fluidity from molten steel.
• Useful in Casting and welding.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
COPPER (Cu)
Content:
• 0.2% - 0.6%
Effects:
• Corrosion resistance increases ( used for
weathering steel “Corten”)
• Hardness increases when mixed with equal
amount of Nickel – 1.25%
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
CHROMIUM (Cr)
Content:
• 0.1% - 0.9%
Effects:
• Corrosion resistance and Hardness - Increases
• Maintains strength of steel at elevated temperatures.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
NICKEL (Ni)
Content:
• 0.25% - 1.5%
Effects:
• Fracture Toughness, Strength, Corrosion resistance
and Ductility - Increases.
• Improved properties are obtained when alloyed more
than 8%.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
MOLYBDENUM (Mo)
Content:
• 0.5% - 4%
Effects:
• Improved Strength and creep resistance
at elevated service temp
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
NIOBIUM (Nb)
Content:
• Less than 0.05%
Effects:
• Combines with steel to form – Niobium carbide and carbonitride
precipitates which increase the strength.
• Strength – Increases.
• Promotes / refines grain size, which improve the Toughness.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
VANADIUM (V)
Content:
• 0.05% - 0.1%
Effects:
• Strength and Toughness – Increases.
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EFFECTS OF ALLOYING ELEMENTS IN STEEL
ALUMINIUM (Al)
Content:
• Up to 0.015%
Effects:
• Acts as a deoxidizer in steel making process.
• Combines with oxygen to form Al2O3.
• Combines with nitrogen to form Aluminium Nitride (AlN)
which increases the Toughness.
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