Lab Manual | Rockwell Hardness testing machine

AIM : To study the Rockwell Hardness testing machine and perform the Rockwell hardness test.

APPARUTS :- Rockwell Hardness testing machine, specimen of mild steel or other material.

THEORY: – Hardness represents the resistance of material surface to abrasion, scratching and cutting, hardness after gives clear indication of strength. In all hardness tests, a define force is mechanically applied on the piece, varies in size and shape for different tests. Common indentors are made of hardened steel or diamond.

Rockwell hardness tester presents direct reading of hardness number on a dial provided with the m/c. principally this testing is similar to Brinell hardness testing. It differs only in diameter and material of the indentor and the applied force. Although there are many scales having different combinations of load and size of indentor but commonly ‘C’ scale is used and hardness is presented as HRC. Here the indentor has a diamond cone at the tip and applied force is of 150 kgf. Soft materials are often tested in ‘B’ scale with a 1.6mm dia. Steel indentor at 60kgf.

SPECIFICATION OF HARDNESS TESTING M/C AND INDENTORS:-

A hardness test can be conducted can be conducted on Brinell testing m/c, Rockwell hardness m/c or vicker testing m/c. the specimen may be a cylinder, cube, thick or thin metallic sheet. A Brinell-cum-Rocwell hardness testing m/c along with the specimen is shown in figure.

Various scales in Rockwell hardness test are given below:-

PROCEDURE:-

1. Insert ball of dia. ‘D’ in ball holder of the m/c.

2. Make the specimen surface clean by removing dust, dirt, oil and grease etc.

3. Make contact between the specimen surface and the ball by rotating the jack adjusting wheel.

4. Push the required button for loading.

5. Pull the load release lever wait for minimum 15 second. The load will automatically apply gradually.

6. Remove the specimen from support table and locate the indentation so made.

7. Repeat the entire operation, 3-times.

OBSERVATION AND CALCULATION : –

Following observation are recorded are from a test on steel specimen using a hardened steel ball as indentor.

· Test piece material =———–

PRECAUTIONS:-

· The specimen should be clean properly

· Take reading more carefully and