Brinell

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 

 

brinell 1

2. Measurement of the indentation
with diameter d 

 

brinell 2

CALCULATION OF THE BRINELL HARDNESS

 

Calculation formula for Brinell hardness:
 
brinell 3
 

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.
 
brinell 4
 
 

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:

 

brinell 5

 

 

 

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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