Brinell Test

Brinell Test

The Brinell test relies on mechanical or hydraulic loads as large as 3000 Kg. acting through a 10 mm hard steel or carbide ball. In order to compensate for variations in the response of materials to the application of the load, the time for which the load is applied is specified. For hard materials such as steel, a 30-second loading period is adequate. Softer metals and alloys such as brass or aluminum require about 60 seconds. After the load is removed, the diameter of the impression made by the ball is measured in millimeters. The Brinell hardness number, abbreviated as BHN, is the quotient of the load, P (kg), divided by the area, A, of the impression:

	P
BHN =	_______________________________
	( D- (D2 - d2) 1/2 ) p D/2

Where D is the diameter of the ball penetrator (mm) and d is the diameter of the impression(mm). In practice, the BHN is read directly from a table listing different values of d for various values of load, P.

The Brinell test makes a large impression on the surface of the piece tested. Unless such a large impression can be tolerated, and often it can not, the test is destructive. However, the large impression is advantageous because it gives a more representative result than would a smaller impression which would be more sensitive to local soft or hard inhomogeneties. The size of the impression also renders the test less sensitive to the presence of rough surface finish and mill scale than is the case when tests are used which rely on small indentations.

Operation of Brinell Testing Machine:

(1) Turn air on

(2) Set the required load on the dial.

Note: For steel and other hard materials the load is 3,000 kg. for 30 seconds. For non-ferrous materials a 500 kg. load is used for 60 seconds. Thin specimens should not be tested by this method.

(3) Place the specimen on the anvil and apply a preload by bringing the specimen surface to contact with the ball penetrator.

(4) Pull the load knob and apply the appropriate timing at that load level.

(5) Release the load by pushing the load knob back into the initial position.

(6) Remove the specimen and measure the diameter of the indentation. The Brinell Microscope reads in millimeters. Take several readings and average them.

(7) Look up BHN from chart or calculate from the formula.

The following is a sample hardness data as presented in a laboratory report. Use the same format in your report.

Material	Rockwell Hardness Scale, Major Load, Type of Penetrator	Rockwell Hardness Number	Brinell Hardness Number	Brinell Load, Indentation Diameter	Tensile Strength (Ksi)
Example 1 (steel)	Rc 150 Kg C-Brale	51 or Rc 51			253
Example 2 (steel)	15 N 45 Kg N-Brale	42 or 15N42			182
Example 3 (Steel)			352	3000 Kg 3.25 mm	176