The hardness of any matter is the resistance to indentation. You measure it by measuring the depth of the indentation when submitted to a fixed force. The Rockwell hardness test is often used in the industry as it is more convenient with high accuracy than all other hardness testing methods. The testing method is applicable on all metal surfaces using a Rockwell hardness tester. However, the test should not be used o in the following circumstances:-
- Where the metal surface conditions would lead to too much variation.
- Where the indentations formed would be bigger for the fore applied
- Where the sample size limits the test usage
- Where the sample shape limits its use
Steps of taking Rockwell hardness test
The Rockwell hardness test starts with a preliminary test force known as the minor load. It is put on a sample using an indenter for a specific dwell time to form an indentation. The depth of indentation is then measured. Afterwards, a major load is input to satisfy the total test load required. The major load is applied for a specified dwell time to cater for the elastic recovery. It is then removed. The preliminary load then holds out for a specific dwell time and the final depth of indentation is determined. The Rockwell hardness is the difference between the baseline and final depth of indentation. It is a reliable hardness test method by specialists.