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A hardness test performed by pressing a steel ball of standard hardness into a surface by a standard pressure.
a hardened steel ball of known diameter is applied to the specimen under a known loading for a period of 1 second.

The diameter of the impression resulting in the specimen is measured with a microscope. Hardness is indicated by the Brinell Number, derived by dividing the applied load in kilograms by the spherical area of the impression in square millimeters. The harder the material, the smaller the impression and consequently the higher the Brinell number. To keep the relationship between load P, diameter D and the impression produced within limits, for different materials, different P/D2 ratios are used. The following are approximate Brinell numbers, for the stated material.

Material Brinell Hardness Number
Bronze (Chill Cast) 32
Brass 60
Gunmetal 70 - 75
Mild Steel 110 - 130
Carbon Steel 150 - 200
Cast Iron 400

Related Terms


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American Society for Testing Materials - a society for developing standards for materials and test methods.


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