Q1: __________ can not be forged.

ANS:B - Cast iron

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2% by weight. It is characterized by its relatively low melting point, good fluidity when molten, excellent castability, and high compressive strength. Here's a detailed explanation of cast iron:

1. Composition: Cast iron is primarily composed of iron (Fe) and carbon (C), along with small amounts of other elements such as silicon (Si), manganese (Mn), sulfur (S), and phosphorus (P). The carbon content in cast iron typically ranges from 2% to 4%.
2. Types of Cast Iron:
   • Gray Cast Iron: Gray cast iron is the most common type of cast iron. It has a graphite microstructure, which gives it its characteristic gray color. The graphite flakes provide lubrication and promote the formation of chips during machining.
   • White Cast Iron: White cast iron has a white fractured surface due to the presence of cementite (iron carbide) in its microstructure. It is hard, brittle, and difficult to machine.
   • Ductile Cast Iron (Nodular Cast Iron): Ductile cast iron contains spherical graphite nodules instead of graphite flakes. This microstructure enhances its toughness, ductility, and impact resistance compared to gray cast iron.
   • Malleable Cast Iron: Malleable cast iron is produced by heat treating white cast iron or ductile cast iron. It has improved ductility and machinability compared to white cast iron.
3. Properties:
   • High Melting Point: Cast iron has a relatively high melting point compared to other metals, typically between 1150°C and 1350°C.
   • Good Fluidity: Molten cast iron has good fluidity, allowing it to fill intricate mold cavities during the casting process.
   • Excellent Castability: Cast iron can be cast into complex shapes with thin sections, making it suitable for a wide range of applications.
   • High Compressive Strength: Cast iron exhibits high compressive strength, making it suitable for applications where strength under compression is important.
   • Brittleness: Cast iron is brittle and prone to cracking under tension or impact loading.
   • Corrosion Resistance: Certain types of cast iron, such as ductile cast iron, can exhibit good corrosion resistance when properly coated or treated.
4. Applications:
   • Automotive Industry: Engine blocks, cylinder heads, brake disks, and other automotive components.
   • Construction: Pipes, fittings, manhole covers, and architectural elements.
   • Machinery: Machine bases, gears, pulleys, and flywheels.
   • Cookware: Cast iron cookware such as skillets, pans, and Dutch ovens.