Rockwell Hardness Testing

3. Rockwell Test Procedure

1. Surface Preparation:
   
   

   • The test specimen should be flat, clean, and free from rust or coatings.

   • The minimum thickness of the specimen should be 10 times the indentation depth to avoid errors.

2. Indenter Selection:

   • Diamond cone (Brale) for hard materials (e.g., steel, iron).

   • Steel ball for soft materials (e.g., brass, aluminum).

3. Application of Load:

   • Minor Load (10 kgf) is applied first to eliminate surface irregularities.

   • Major Load (60, 100, or 150 kgf) is applied and held for a specific time.

   • After the major load is removed, the indentation depth is measured under the minor load.

4. Direct Hardness Reading:

   • The Rockwell Hardness Number (HR) is displayed on the dial or digital screen without additional calculations.

4. Advantages of Rockwell Hardness Test

✔ Quick and Direct Reading – No need for complex calculations.
✔ Suitable for Hard and Soft Materials – Different scales allow testing of a wide range of metals.
✔ Minimal Surface Damage – Small indentation compared to Brinell test.
✔ Automated Testing Possible – Many modern Rockwell testers provide digital readings.

5. Limitations of Rockwell Hardness Test

❌ Not suitable for very thin materials – Indentation depth can be too large.
❌ Surface finish affects accuracy – Rough or uneven surfaces may give incorrect readings.
❌ Limited to specific load-indenter combinations – Different materials require different scales.

6. Applications of Rockwell Hardness Test

• Automobile and Aerospace Industry – Testing steel, aluminum, and heat-treated components.

• Tool and Die Industry – Hardness testing of cutting tools, dies, and molds.

• Manufacturing and Quality Control – Ensuring material consistency in production.

• Construction Industry – Hardness measurement of structural materials.