HEAT TREATMENT OF NON-FERROUS METALS

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• Q1: Define Alloy.
  Ans: An Alloy is a mixture of two or more metals, or a metal and a non-metal, designed to improve strength, corrosion resistance, hardness, or other properties.
• Q2: Define Cast Iron.
  Ans: Cast Iron is an iron-carbon alloy containing 2 — 4% carbon, known for its high hardness, compressive strength, and good casting properties.
• Q3: State four properties of Cast Iron.
  Ans: Properties of Cast Iron:

  • ➔ High compressive strength
  • ➔ Brittle in tension
  • ➔ Good wear resistance
  • ➔ Excellent castability
• Q4: State the types of Cast Iron.
  Ans: The types of Cast Iron are as follows:

  • ➔ White Cast Iron
  • ➔ Malleable Cast Iron
  • ➔ Gray Cast Iron
  • ➔ Chilled Cast Iron
  • ➔ Nodular Cast Iron
  • ➔ Alloy Cast Iron
• Q5: What is White Cast Iron?
  Ans: White Cast Iron is a hard, brittle cast iron with cementite in its structure, formed by rapid cooling of molten iron.
• Q6: State any four structural properties of White Cast Iron.
  Ans: Structural Properties of White Cast Iron:

  • ➔ Hard and brittle
  • ➔ High wear resistance
  • ➔ Contains cementite
  • ➔ Poor machinability
• Q7: What are Gray Cast Irons?
  Ans: Gray Cast Iron is a cast iron with graphite flakes in its structure, giving it a gray appearance and good damping capacity.
• Q8: State any four structural properties of Gray Cast Irons.
  Ans: Structural Properties of Gray Cast Iron:

  • ➔ Good machinability
  • ➔ Moderate hardness
  • ➔ Contains graphite flakes
  • ➔ Excellent vibration damping
• Q9: What are Chilled Cast Irons?
  Ans: Chilled Cast Iron is cast iron with a hard, white outer surface produced by rapid cooling, while the inner part is gray cast iron.
• Q10: What are Malleable Cast Irons?
  Ans: Malleable Cast Irons are heat-treated white cast irons that are made ductile and tough by annealing, suitable for machining and forging.
• Q11: What are Nodular Cast Irons?
  Ans: Nodular Cast Irons, or Ductile Irons, have spherical graphite in the structure, providing high strength, ductility, and toughness.
• Q12: What is Alloy Cast Irons?
  Ans: Alloy Cast Iron is cast iron with added elements like nickel, chromium, or molybdenum to improve hardness, strength, and corrosion resistance.
• Q13: What is Ledeburite?
  Ans: Ledeburite is a eutectic mixture of austenite and cementite formed in iron-carbon alloys with 4.3% carbon at 1147°C.
• Q14: Briefly explain the process of Annealing of Gray Cast Iron.
  Ans: Procedure of Annealing Gray Cast Iron:

  • ➔ Heat the gray cast iron to 800 — 900°C.
  • ➔ Hold at this temperature for a required period.
  • ➔ Cool slowly inside the furnace.
  • ➔ Relieves internal stresses and improves machinability.
• Q15: Briefly explain the process of Stress Relieving of Gray Cast Iron.
  Ans: Procedure of Stress Relieving Gray Cast Iron:

  • ➔ Heat the gray cast iron to 600 — 650°C.
  • ➔ Hold at this temperature to reduce internal stresses.
  • ➔ Cool slowly to prevent distortion or cracking.
• Q16: Briefly explain the process of Quenching of Gray Cast Iron.
  Ans: Procedure of Quenching Gray Cast Iron:

  • ➔ Heat the gray cast iron to a high temperature.
  • ➔ Rapidly cool it in water, oil, or a salt bath.
  • ➔ Hardens the surface of the cast iron.
• Q17: Briefly explain the process of Normalizing of Gray Cast Iron.
  Ans: Procedure of Normalizing Gray Cast Iron:

  • ➔ Heat the gray cast iron above the critical temperature.
  • ➔ Hold at this temperature for uniform heating.
  • ➔ Cool in air.
  • ➔ Refines grain structure and relieves internal stresses.
• Q18: Briefly explain the process of Producing Chilled Cast Iron.
  Ans: Procedure of Producing Chilled Cast Iron:

  • ➔ Pour molten gray cast iron into a metal mold or casting sand.
  • ➔ Surface cools rapidly.
  • ➔ Produces a hard, white layer on the surface.
• Q19: Briefly explain the process of Annealing of Aluminium and its alloys.
  Ans: Procedure of Annealing Aluminium and its Alloys:

  • ➔ Heat aluminium or its alloys to 300 — 550°C.
  • ➔ Hold at this temperature to remove internal stresses.
  • ➔ Cool slowly.
  • ➔ Improves ductility and toughness.
• Q20: What is Recrystallization?
  Ans: Recrystallization is the process in which deformed grains of a metal are replaced by new, strain-free grains during annealing, restoring ductility.
• Q21: Name the types of Annealing of Aluminium and its alloys.
  Ans: Types of Annealing of Aluminium:

  • ➔ Full Annealing
  • ➔ Partial Annealing
  • ➔ Process Annealing
• Q22: Name the three stages of Annealing of Aluminium.
  Ans: Three Stages of Annealing of Aluminium:

  • ➔ Recovery
  • ➔ Recrystallization
  • ➔ Grain Growth
• Q23: Define Heat Treated Alloys.
  Ans: Heat Treated Alloys are alloys whose mechanical properties are improved by controlled heating and cooling processes.
• Q24: Define Work Hardened Alloys.
  Ans: Work Hardened Alloys are alloys that have increased hardness and strength due to plastic deformation at room temperature.
• Q25: Briefly explain the process of Annealing of Work Hardened Alloys of Aluminium.
  Ans: Procedure of Annealing Work Hardened Aluminium Alloys:

  • ➔ Heat the work-hardened aluminium alloy to a suitable temperature.
  • ➔ Hold to allow recovery and recrystallization.
  • ➔ Cool slowly.
  • ➔ Restores ductility of the alloy.
• Q26: Briefly explain the process of Annealing of Heat Treated Alloys of Aluminium.
  Ans: Procedure of Annealing Heat Treated Aluminium Alloys:

  • ➔ Reheat the alloy to a temperature below the solution treatment temperature.
  • ➔ Hold to relieve internal stresses.
  • ➔ Cool to stabilize the properties.
• Q27: Briefly explain the Furnace used for the Annealing of Aluminium and its alloys.
  Ans: Furnace Used for Annealing Aluminium Alloys:

  • ➔ Use controlled-atmosphere or electric furnaces.
  • ➔ Ensure uniform temperature throughout the furnace.
  • ➔ Provide slow cooling to prevent thermal stresses.
  • ➔ Prevent oxidation of the alloy surface.
• Q28: Briefly explain the process of Annealing of Copper and its alloys.
  Ans: Procedure of Annealing Copper and Its Alloys:

  • ➔ Heat copper alloys to 400 — 700°C depending on composition.
  • ➔ Hold at this temperature to relieve stresses and soften the metal.
  • ➔ Cool slowly in air or furnace.
• Q29: Briefly explain the process of Homogenising Annealing of Copper and its alloys.
  Ans: Procedure of Homogenising Annealing Copper Alloys:

  • ➔ Heat copper alloys slightly above their solidus temperature.
  • ➔ Hold to dissolve segregation.
  • ➔ Cool slowly to achieve uniform composition and properties.
• Q30: Briefly explain the process of Stress Relieving of Copper Alloys.
  Ans: Procedure of Stress Relieving Copper Alloys:

  • ➔ Heat copper alloys to 200 — 400°C.
  • ➔ Hold for a few hours.
  • ➔ Cool slowly to reduce internal stresses caused by cold working or machining.
• Q31: Briefly explain the process of Recrystallisation of Copper and its alloys.
  Ans: Procedure of Recrystallisation Copper Alloys:

  • ➔ Heat deformed copper alloys to a specific temperature.
  • ➔ Allow new strain-free grains to form.
  • ➔ Restore ductility without significant grain growth.
• Q32: What is Precipitation Hardening?
  Ans: Precipitation Hardening is a heat treatment process where fine particles are formed within an alloy matrix to increase hardness and strength.
• Q33: Briefly explain the process of Solution Treatment as a part of Precipitation Hardening.
  Ans: Procedure of Solution Treatment (Precipitation Hardening):

  • ➔ Heat the alloy to a high temperature to dissolve soluble constituents into a solid solution.
  • ➔ Hold at this temperature to ensure uniform solution.
  • ➔ Quench the alloy rapidly to retain the solid solution.
• Q34: Briefly explain the process of Quenching as a part of Precipitation Hardening.
  Ans: Procedure of Quenching (Precipitation Hardening):

  • ➔ Rapidly cool the alloy immediately after solution treatment.
  • ➔ Trap the alloying elements in a supersaturated solid solution.
  • ➔ Prepare the alloy for the precipitation (aging) step.
• Q35: Briefly explain the process of Precipitation Treatment as a part of Precipitation Hardening.
  Ans: Procedure of Precipitation Treatment (Aging):

  • ➔ Heat the quenched alloy to a moderate temperature.
  • ➔ Hold to allow fine particles to form.
  • ➔ Hardness and strength of the alloy increase.
• Q36: Briefly explain the process of Stress Relieving of Brass.
  Ans: Procedure of Stress Relieving Brass:

  • ➔ Heat brass components to 200 — 400°C.
  • ➔ Hold for several hours.
  • ➔ Cool slowly to remove residual stresses from forming or machining operations.