Q1: Aluminium oxide (an abrasive) is used for grinding

ANS:B - high speed steel

High-speed steel (HSS) is a type of tool steel that is specifically designed for use in applications where the cutting tools are subjected to high speeds, temperatures, and mechanical stresses. It is known for its exceptional combination of hardness, wear resistance, toughness, and heat resistance, which make it ideal for cutting, drilling, milling, and machining operations in various industries. Here are some key characteristics and features of high-speed steel:

1. Composition: High-speed steel is an alloy steel that typically contains alloying elements such as tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), and cobalt (Co). These alloying elements contribute to the unique properties of HSS, such as hardness, red hardness (ability to retain hardness at elevated temperatures), and wear resistance.
2. Hardness: High-speed steel is characterized by its high hardness, which allows it to maintain sharp cutting edges even at high temperatures encountered during cutting operations. This property helps prolong tool life and maintain dimensional accuracy in machining processes.
3. Wear Resistance: HSS exhibits excellent wear resistance due to the presence of alloying elements like tungsten and molybdenum, which form hard carbides in the steel matrix. These carbides enhance the resistance of the material to abrasion and wear, resulting in longer tool life and improved performance in high-speed machining operations.
4. Toughness: Despite its high hardness, HSS retains good toughness, allowing it to withstand mechanical shock and impact loads encountered during cutting operations. This toughness helps prevent chipping and fracturing of cutting edges, leading to improved tool reliability and reduced downtime.
5. Heat Resistance: High-speed steel can withstand elevated temperatures encountered during high-speed machining without significant loss of hardness or mechanical properties. This property, known as red hardness, enables HSS cutting tools to maintain their cutting performance even at high temperatures, resulting in consistent machining quality and productivity.
6. Versatility: High-speed steel is a versatile material suitable for a wide range of cutting applications, including turning, milling, drilling, threading, and broaching. It is commonly used in the production of cutting tools such as drills, taps, reamers, end mills, and inserts for both ferrous and non-ferrous materials.

Overall, high-speed steel is valued for its exceptional combination of hardness, wear resistance, toughness, and heat resistance, making it one of the most widely used materials in the manufacturing industry for cutting tools and machining applications.