Q1: To improve the machinability of steel by its softening, it is subjected to

ANS:C - shot blasting

Shot blasting is a surface treatment process used to clean, strengthen, or prepare the surface of a material by propelling abrasive particles at high velocity onto the surface. It is commonly used in various industries for surface preparation, surface cleaning, and surface finishing applications. Here's a detailed explanation of shot blasting:

1. Principle:
   • Shot blasting operates on the principle of kinetic energy transfer. Abrasive particles, typically made of materials like steel, cast iron, or aluminum oxide, are propelled at high velocity onto the surface of the workpiece using compressed air or centrifugal force.
   • The kinetic energy of the abrasive particles imparts mechanical energy to the surface of the material, effectively removing surface contaminants, scale, rust, or old coatings, and creating a textured or profiled surface finish.
2. Equipment:
   • Shot blasting machines consist of an enclosed chamber or cabinet where the workpiece is placed. The machine includes a blast wheel or turbine that propels the abrasive particles, a dust collection system to capture airborne particles, and a recovery system to recycle and reuse the abrasive media.
   • Depending on the application, shot blasting machines may be equipped with various configurations, such as batch-type machines for small parts or continuous conveyor systems for large and heavy workpieces.
3. Abrasive Media:
   • Abrasive media used in shot blasting can vary in size, shape, and composition depending on the material being treated and the desired surface finish.
   • Common types of abrasive media include steel shot, steel grit, aluminum oxide, garnet, glass beads, and ceramic beads. Each type of abrasive media has specific properties, such as hardness, shape, and particle size distribution, that influence its effectiveness for different applications.
4. Applications:
   • Shot blasting is used for a wide range of applications across various industries, including:
     • Surface cleaning and preparation before coating, painting, or plating.
     • Removal of rust, scale, mill scale, or welding residues from metal surfaces.
     • Surface texturing or profiling to improve adhesion of coatings or to impart decorative finishes.
     • Deburring and edge rounding of metal components.
     • Shot peening to improve the fatigue life and stress resistance of metal parts by inducing compressive residual stresses on the surface.
5. Advantages:
   • Shot blasting offers several advantages over traditional surface preparation methods, including fast and efficient cleaning, uniform surface treatment, selective removal of surface contaminants, and the ability to achieve specific surface roughness or texture requirements.
   • It is a versatile and cost-effective process suitable for a wide range of materials, shapes, and sizes of workpieces.

In summary, shot blasting is a highly effective surface treatment process used for cleaning, strengthening, and preparing the surface of materials by propelling abrasive particles at high velocity. It is widely used in various industries for surface preparation, surface cleaning, and surface finishing applications.