CASE HARDENING PROCESS

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• Q1: Define Case Hardening.
  Ans: Case Hardening is a heat treatment process in which the surface of low-carbon steel is hardened while the core remains soft and ductile.
• Q2: Write the names of Case Hardening Processes.
  Ans: Case Hardening Processes:

  • ➔ Carburizing
  • ➔ Cyaniding
  • ➔ Nitriding
  • ➔ Flame Hardening
  • ➔ Induction Hardening
• Q3: Define Core.
  Ans: Core is the inner part of a steel component that remains soft and ductile during case hardening while the surface is hardened.
• Q4: Define Carburizing.
  Ans: Carburizing is a case hardening process in which carbon is diffused into the surface of low-carbon steel at high temperatures to increase hardness.
• Q5: State the types of Carburizing.
  Ans: Types of Carburizing:

  • ➔ Pack Carburizing
  • ➔ Gas Carburizing
• Q6: What is Pack Carburizing?
  Ans: Pack Carburizing is a method where steel components are packed in a carbon-rich material like charcoal and heated to high temperatures to diffuse carbon into the surface.
• Q7: What is Gas Carburizing?
  Ans: Gas Carburizing is a method where steel is heated in a carbon-rich gas atmosphere, such as methane or propane, to allow carbon to diffuse into the surface.
• Q8: What is the Cyaniding Process for Case Hardening of Steel?
  Ans: Cyaniding is a process in which steel is heated in a bath of sodium cyanide or a mixture of cyanide salts to introduce both carbon and nitrogen into the surface for hardening.
• Q9: Write the equation of the Cyaniding Process.
  Ans: NaCN → Na + C + N
  Carbon and nitrogen diffuse into the steel surface during heating.
• Q10: What is the Nitriding for Case Hardening of Steel?
  Ans: Nitriding is a case hardening process in which nitrogen is diffused into the surface of steel at relatively low temperatures to increase hardness and wear resistance.
• Q11: What is the temperature in the Nitriding Process?
  Ans: The temperature for nitriding is usually between 500°C and 550°C.
• Q12: What is the Process of Flame Hardening for Case Hardening of Steel?
  Ans: Flame Hardening is a process in which the steel surface is rapidly heated by an oxy-acetylene flame and then quenched, hardening only the surface layer.
• Q13: State the methods of Flame Hardening.
  Ans: Methods of Flame Hardening:

  • ➔ Oxy-Acetylene Flame Hardening
  • ➔ Oxygen-Gas Flame Hardening
• Q14: What is the Process of Induction Hardening for Case Hardening of Steel?
  Ans: Induction Hardening is a process in which the surface of steel is heated by electromagnetic induction and then quenched to produce a hardened surface while the core remains soft.
• Q15: What is the Skin Effect in the process of Induction Hardening?
  Ans: Skin Effect is the tendency of alternating current to concentrate near the surface of the steel during induction heating, causing rapid heating of the surface while the core remains cooler.