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Brinell

BACKGROUND INFORMATION BRINELL HARDNESS TESTING (DIN EN ISO 6506)     Johann August Brinell (Sweden) presented his new hardness testing method at the world exhibition in Paris in 1900.   In this method, a carbide ball is pressed vertically into the surface of a sample with a certain force. This creates an indentation in the sample surface. The diameter of the indentation d is determined using a measuring microscope and the Brinell hardness is calculated or referred to from the corresponding tables.
1. Indentation of a hard metal ball with ØD and test force F in the specimen	2. Measurement of the indentation with diameter d
CALCULATION OF THE BRINELL HARDNESS   Calculation formula for Brinell hardness:     For the Brinell hardness test, the selection of suitable test parameters is of decisive importance. The Brinell method becomes inaccurate for very small or very large penetration depths. For this reason, the test load must be selected such that the following conditions are met for the mean indentation diameter: 0,24 * D < d <0,6 * D In order to meet these conditions, 'Stress level B' was introduced. This depends on the material group to be tested.       The stress level is selected according to the following table:      STRESS LEVEL B FOR BRINELL HARDNESS TESTERS Material Stress level B [N/mm²] Ball diameterD [mm] Test forceF [N] Recordable Hardness Range [HBW] Steel and cast steel Nickel and titanium alloys Cast iron ≥ 140 HBW Cu and Cu alloys ≥ 200 HBW     30 1 2,5 5 10 2,94,2 1839 7355 29420 95 – 650 Light metals and their alloys ≥ 35 HBW     15 1 2,5 5 10 - - - 14710 48 – 327 Cast iron < 140 HBW Cu and Cu alloys 350-200 HBW     10 1 2,5 5 10 98,07 612,9 2452 9807  32 – 218 Cu and Cu alloys < 35 HBW Light metals and their alloys ≥ 35 < HBW <  80      5 1 2,5 5 10 49,03 306,5 1226 4903 16 – 109 Light metals and their alloys ≥ 35 HBW     2,5 1 2,5 5 10 24,52 153,2 612,9 2452   8 – 55 Lead and tin     1 1 2,5 5 10 9,807 61,29 245,2 98,7 3 – 22   According to DIN EN ISO 6506 Only ball diameters >1 mm may be used for testing cast iron       After the degree of stress has been determined, test load F and ball diameter D can be determined according to the table. In principle, the ball diameter should be as large as possible in order to cover as large and therefore representative a part of the sample surface as possible. Hardness values determined with different ball diameters at the same degree of loading can only be compared to a limited extent. Hardness values determined with the same ball diameter but different degrees of loading are not comparable. Therefore, it is essential that all parameters are always specified when specifying a hardness value.   BRINELL HARDNESS TESTING RESULTS According to DIN EN IS 6506-1 the result of a Brinell hardness test is indicated as follows:   310 HBW 2,5 / 187,2 / 20   ⇒   Hardness value as per Brinell 310 HBW 2,5 / 187,2 / 20   ⇒   Abbreviation for Brinell hardness 310 HBW 2,5 / 187,2 / 20   ⇒   Ball diameter in mm 310 HBW 2,5 / 187,2 / 20   ⇒   Test force [N] = 9.807 * test force specification 310 HBW 2,5 / 187,2 / 20   ⇒   Application time of the test force  (omitted if it is between 1-15 s)     FURTHER PREREQUISITES FOR BRINELL HARDNESS TESTING   More prerequisites need to be fulfilled for standard-compliant testing:         Test temperature normal requirements: 10°C bis 35°C high requirements: 23°C ± 5°C Distances between the indentations and from the edge a ≥ 2,5 * d b ≥ 3,5 * d

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