Hardness test

Hardness test:

        BRINELL HARDNESS TEST:

     Dr J. A. Brinell invented the Brinell test in Sweden in 1900. The oldest of the hardness test methods in common use today, the Brinell test is frequently used to determine the hardness of forgings and castings that have a grain structure too course for Rockwell or Vickers testing. Therefore, Brinell tests are frequently done on large parts. By varying the test force and ball size, nearly all metals can be tested using a Brinell test. Brinell values are considered test force independent as long as the ball size/test force relationship is the same.   

         

Brinell Test Method:

All Brinell tests use a carbide ball indenter. The test procedure is as follows:
• The indenter is pressed into the sample by an accurately controlled test force.
• The force is maintained for a specific dwell time, normally 10 - 15 seconds.
• After the dwell time is complete, the indenter is removed leaving a round indent in the sample.
• The size of the indent is determined optically by measuring two diagonals of the round indent using either a portable microscope or one that is integrated with the load application device.
• The Brinell hardness number is a function of the test force divided by the curved surface area of the indent. The indentation is considered to be spherical with a radius equal to half the diameter of the ball. The average of the two diagonals is used in the following formula to calculate the Brinell hardness. 


                          
                   The Brinell number, which normally ranges from HB 50 to HB 750 for metals, will increase as the sample gets harder. 

 METALLURGICAL MICROSCOPE:

Microscope Stand   : Rigid & stable stand with well counted large modular base. Ball baring                                                 guide ways and slides provides extra smooth movement
Viewing Head         : Binocular with dipodic and inter papillary adjustment. 
Focusing         : Co-axial Coarse & Fine focusing module
Stage                : Large size stage with co-axial low drive, for convenient viewing of                                                        specifications 
Illumination        :  Incident light through Epi-illuminator with field Aperture Diaphragm and                                            filter slot, continuously variable luminosity control through built in-in                                                            electronic Transformer.
Objectives         : High fidelity flat field objectives M5x, M10x, M40x, M100x 
Eyepieces         : Compensation Wide field 10x & 15x paired.
Magnification         : 50x - 1500x



              

PROCEDURE FOR MICRO STRUCTURE:

Place the specimen inside the cylinder of the mounting press.
Pour 15 to 25 grams of Bakelite powder on the specimen into the Cylinder.
Insert the cap screw into the cylinder and fix it.
Raise the piston with the hydraulic arrangement so that the Bakelite powder gets compressed.
Switch on the electric timer and set the time to 15 minutes.
After 15 minutes remove the specimen` which is embedded in Bakelite powder by removing the         cap screw and raising the piston.
Make the specimen flat by using motor driven emery belt.
Carry fine polishing on the specimen using aluminium oxide and diamond paste abrasives.
Carry fine polishing on the specimen using aluminium oxide and diamond paste abrasives.
Clean the specimen with water.
Etch the specimen with suitable etching agent and clean the specimen with water.
Dry   the   specimen   and observe the structure under the microscope.
If the structure and observe the structure under the microscope and is drawn.

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