Explain the effect of alloying various elements on properties of steel.Ripunjay Tiwari
Ans·. The effects of various alloying elements are as follows
(a) Nickel increases hardness, toughness and impact strength at low temperature.
(b) Improves response to heat treatment especially in large sections.
(c) Improves elasticity, resistance to fatigue and corrosion.
(ii) Chromium –
(a) It forms a complex series of chromium carbides and thus
improves the harden ability and increases resistance to abrasion and wear.
(b) Combination of nickel and chromium improves the mechanical properties of steel.
(iii) Silicon –
(a) It removes oxygen in steel making.
(b) Increases strength without decreasing ductility.
(iv) Molybdenum –
(a) Molybdemu:n joins with carbon and promotes hardenability.
(b) Steel containing chromium and nickel suffer from temper
brittleness, this difficulty can be overcome by adding 0.25% molybdenum.
(c) Raises tensile and creep strength at high temperatures.
(a) Lowers the toughness and transverse ductility.
(b) Imports brittleness to chips removed in machining opera’tion.
(vi) Manganese –
(a) Counteracts the effect of sulphur (i.e., brittleness).
(b) Steel containing 11.-14% manganese are resistant to wear,
work harden easily and are resistant to abrasion under shock.
(vii) Vanadium –
(a) It gives strength and toughness to steel.
(b) It improves the hardening quality of steel.
(c) Used for providing a fine grained structure over a wide
range of temperature.
(a) Prevents precipitation of chromium carbide.
(a) It increase cutting hardness and magnetic retentivity.
(b) Refines the grains.
(c) It resists heat.
(a) It improves hardness and mechanical properties.
(b) It also improves rolling qualities of steel.
(a) Improves atmospheric corrosion resistance.
(b) Acts as a strengthening agent.
(xii) Aluminium –
(a) Used as an effective deoxidiser.
(b) Controls grain growth.
(c) Increases surface hardness.
(a) Improves mechanical properties such as tensile strength,
fatigue strength and hardness.
(b) Improves heat resistance.