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.
