Q1: Turning/machining of __________ usually does not require any cutting fluid.

ANS:A - cast iron

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. It is one of the oldest and most versatile materials used in engineering and construction due to its excellent properties, including strength, wear resistance, and castability. Here are some key points about cast iron:

1. Composition: Cast iron primarily consists of iron (Fe) and carbon (C), with carbon typically present in the range of 2% to 4%. In addition to iron and carbon, cast iron may contain other alloying elements such as silicon (Si), manganese (Mn), sulfur (S), and phosphorus (P), which influence its properties.
2. Types of Cast Iron:
   • Gray Cast Iron: Contains graphite flakes dispersed throughout the matrix of ferrite and pearlite. Gray cast iron is known for its excellent machinability, damping capacity, and wear resistance. It is commonly used in applications such as engine blocks, cylinder heads, and machine tool components.
   • White Cast Iron: Has a white, crystalline fracture surface due to the presence of cementite (iron carbide) in the microstructure. White cast iron is extremely hard and brittle, making it suitable for applications requiring wear resistance, such as grinding balls and liners for crushing equipment.
   • Ductile Cast Iron (Nodular Cast Iron): Contains nodules of graphite instead of flakes, which improve its ductility and toughness compared to gray cast iron. Ductile cast iron combines the strength and wear resistance of cast iron with the ductility of steel, making it suitable for a wide range of applications, including automotive components, pipes, and gears.
   • Malleable Cast Iron: Undergoes heat treatment to convert the carbon in the form of graphite into irregularly shaped nodules, resulting in improved ductility and toughness compared to white cast iron. Malleable cast iron is used in applications requiring high strength and impact resistance, such as pipe fittings and automotive parts.
3. Properties:
   • High Strength: Cast iron exhibits high compressive strength, making it suitable for structural applications where resistance to compressive loads is essential.
   • Wear Resistance: The presence of graphite in cast iron provides inherent lubrication, reducing friction and wear during sliding or abrasive contact with other surfaces.
   • Good Machinability: Gray cast iron is easy to machine due to its graphite flakes, which act as solid lubricants, reducing tool wear and improving surface finish.
   • Damping Capacity: Cast iron has excellent damping capacity, absorbing and dissipating vibrations, which makes it suitable for applications requiring noise reduction and vibration damping.
4. Applications: Cast iron is used in various industries and applications, including:
   • Automotive: Engine blocks, cylinder heads, brake rotors, and exhaust manifolds.
   • Construction: Manhole covers, pipe fittings, and architectural elements.
   • Machinery: Machine tool components, gears, and pulleys.
   • Infrastructure: Water and sewage pipes, bridge bearings, and railway components.

Overall, cast iron is a versatile material with a wide range of properties and applications, making it indispensable in various industries and sectors of the economy. Its combination of strength, wear resistance, and machinability makes it suitable for a diverse range of engineering and construction applications.