Question

It is essential to do annealing and pickling, after performing
1. drilling
2. grinding
3. metal spinning
4. broaching

Answer 1

Correct Answer - Option 2 : grinding

Concept:

Grinding:

• Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.
• Grinding is used to finish workpieces that must show high surface quality and high accuracy of shape and dimension.
• The accuracy in dimensions in grinding is of the order of 0.000025 mm.
• According to the accuracy of the work to be done on a grinding machine, they are classified as Rough grinding machines and precision grinding machines.
• For grinding a job, the right grinding wheel is to be selected. The selection of a grinding wheel will depend on the following factor:
  • Material to be ground
  • Amount of stock to be removed
  • Area of contact
  • Finish required
  • Wheel speed
  • Work speed

After the removal of organic contaminants, the following procedures are commonly used.
Electropolishing

• Electropolishing normally produces a surface that guarantees optimal corrosion resistance.
• The material gains a fine luster, and, above all, an even micro profile that meets extremely stringent hygienic requirements.

Pickling

• Pickling is the most common chemical procedure used to remove oxides and iron contamination.
• Thorough rinsing with clean tap water must follow pickling.
• The water quality requirements, including acceptable chloride content, increase with the surface requirements.
• Pickling normally involves using an acid mixture containing 8-20 vol% nitric acid (HNO₃) and 0.5-5 vol% hydrofluoric acid (HF).
• Chloride containing agents such as hydrochloric acid (HCl) should be avoided since there is an obvious risk of pitting corrosion.