What is the full form of ‘CBN’, which is used as an abrasive in grinding processes?

Explanation:

Cubic Boron Nitride (CBN)

Definition: Cubic Boron Nitride (CBN) is a synthetically produced material that is used as an abrasive in grinding processes. It is known for its exceptional hardness, second only to diamond, and is primarily used in applications that require high precision and durability.

Properties: CBN is characterized by its high thermal stability, chemical resistance, and hardness. These properties make it an excellent material for cutting and grinding tools, particularly when working with hard and ferrous materials.

Manufacturing Process: CBN is produced by transforming hexagonal boron nitride (hBN) into its cubic form under high-pressure and high-temperature conditions. The process involves placing hBN in a press, subjecting it to pressures of around 5-10 GPa and temperatures of about 1500-2000°C. This transformation alters the crystal structure, resulting in the formation of CBN.

Advantages:

• Hardness: CBN is one of the hardest known materials, making it highly effective for grinding and cutting applications.
• Thermal Stability: It retains its hardness at high temperatures, which is crucial for maintaining performance during high-speed grinding processes.
• Chemical Resistance: CBN is chemically inert with ferrous materials, preventing reactions that could degrade the tool or the workpiece.
• Longevity: Tools made with CBN have a longer lifespan compared to those made with conventional abrasives, reducing the frequency of tool replacement and downtime.

Applications: CBN is widely used in various industrial applications, including:

• Grinding: CBN grinding wheels are used for precision grinding of hardened steels and superalloys.
• Cutting Tools: It is used in the production of cutting tools for machining hard metals.
• Finishing: CBN is used for finishing operations where high precision and surface quality are required.

Correct Option Analysis:

The correct option is:

Option 4: Cubic boron nitride

This option correctly identifies the full form of "CBN," which is Cubic Boron Nitride. CBN is an abrasive material used in grinding processes due to its exceptional hardness and thermal stability.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Calcium bi nitrous

This option is incorrect as "Calcium bi nitrous" does not refer to any known abrasive material used in grinding processes. It is not related to the term "CBN."

Option 2: Carbon boron nitrate

This option is incorrect because "Carbon boron nitrate" is not the correct full form of CBN. Additionally, it is not a material used in grinding processes. The correct term is Cubic Boron Nitride.

Option 3: Copper boron nitride

This option is incorrect as "Copper boron nitride" does not exist as a commonly known material in grinding processes. The term CBN specifically refers to Cubic Boron Nitride, not a compound involving copper.

Conclusion:

Understanding the correct full form of CBN is essential for recognizing its significance in industrial applications. Cubic Boron Nitride (CBN) is a critical material used in grinding and cutting tools due to its exceptional hardness, thermal stability, and chemical resistance. It is important to distinguish CBN from other materials and understand its specific properties and applications to appreciate its role in manufacturing and precision engineering.