Materials used for making permanent magnets containing iron and nickel are made by __________ technique.

ANS:C - forging

Forging is a manufacturing process that involves shaping metal by applying compressive forces, typically using a hammer, press, or die. Here's an explanation of the forging process:

1. Preparation: The forging process begins with the selection of a suitable metal workpiece, often in the form of a billet or ingot. The workpiece is heated to a temperature above its recrystallization temperature but below its melting point to make it more malleable and easier to deform.
2. Shaping: Once heated, the workpiece is placed on a die or anvil and subjected to compressive forces. This force may be applied using a hammer in hand forging or a mechanical press in machine forging. The metal is shaped into the desired form by repeated blows or pressure, gradually reducing its cross-sectional area and increasing its length or width.
3. Types of Forging:
   • Open-die forging: In this process, the workpiece is placed between two flat or contoured dies, and compressive forces are applied to deform the metal. The metal flows outward from the center, resulting in a final shape determined by the movement of the dies.
   • Closed-die forging: Also known as impression-die forging, this process involves placing the workpiece within a die cavity that contains the desired shape. Compressive forces are applied to deform the metal, causing it to flow and fill the cavity, resulting in a final part with precise dimensions and details.
   • Roll forging: In this process, cylindrical or flat workpieces are passed between two rotating rollers that apply compressive forces to deform the metal. Roll forging is commonly used to produce long, cylindrical parts such as shafts and axles.
4. Finishing: After shaping, the forged part may undergo additional processes such as heat treatment, machining, or surface finishing to achieve the desired properties and surface quality.

Forging offers several advantages, including:

• Improved mechanical properties: The forging process refines the grain structure of the metal, resulting in enhanced strength, toughness, and fatigue resistance.
• Better material utilization: Forging allows for precise shaping of metal with minimal material waste.
• High production rates: Modern forging techniques, such as automated machine forging, enable the rapid production of complex parts with consistent quality.

Overall, forging is a versatile and widely used manufacturing process for producing high-quality metal components for various applications in industries such as automotive, aerospace, construction, and manufacturing.