Brinell Hardness Test: Introduction, Procedure, Formula, Standards (PDF)

Written by Anup Kumar Dey in Engineering Materials,Mechanical

The hardness of a material is its ability to resist localized permanent deformation, penetration, scratching, or indentation. So, it is an important parameter in engineering. Hardness Testing provides a means to quantify the hardness of a material and it is a key element in many quality control procedures and R&D work. Several methods are available for hardness testing. However, Brinell, Rockwell, Vickers, Knoop, Mohs, Scleroscope, and the files test are the most widely used hardness tests. In this article, we will learn about Brinell Hardness Test, its procedure, related formula, and standards.

What is the Brinell Hardness Test?

The Brinell Hardness Test method is the most commonly used hardness measurement technique in the industry. In the Brinell Hardness Testing, the hardness of a metal is determined by measuring the permanent indentation size produced by an indenter. Harder materials will generate shallow indentations while the softer materials will produce deeper indentations. This test method was first proposed by Swedish engineer Johan August Brinell in 1900 and according to his name, the test is popular as Brinell Hardness Test.

Brinell Hardness Test Procedure

The Brinell Hardness test is performed in a Brinell hardness test unit. In this test method, a predetermined force (F) is applied to a tungsten carbide ball of fixed diameter (D) and held for a predetermined time period, and then removed. The spherical indenter creates an impression (permanent deformation) on the test metal piece. This indentation is measured across two or more diameters and then averaged to get the indentation diameter (d). Using this indentation size (d) Brinell Hardness Number (BHN) is found using a chart or calculated using the Brinell hardness test formula. The equipment used for Brinell Hardness Testing are:

  • Brinell Hardness Testing Machine
  • Indenter Sphere, and
  • Brinell microscope to measure the generated impression.

Brinell Hardness Testing Machine:

The Brinell Hardness Testing Machine (Fig. 1) consists of a loading system that includes leavers, weights, hydraulic dashpot, and plunger enclosed in the body of the machine. The test material is kept on the adjustable anvil. Using the lever, the spherical ball indenter descends on the material with a pre-decided force that can be read on the screen.

Brinell Hardness Testing Machine
Fig. 1: Brinell Hardness Testing Machine

For softer metals the force used is less than harder metals. The force value varies from 1 kgf to 3000 kgf. Common test forces range from 500 kgf often used for non-ferrous materials to 3000 kgf for steels and cast irons.

There are four sizes of the indenter used for the Brinell hardness test. They are 1 mm, 2.5 mm, 5 mm, and 10 mm in size.

To obtain the same BHN with different ball diameters, geometrically similar indentations must be produced. It is possible if F/D2 is maintained constant.

Brinell Hardness Test Formula

Once the average indentation diameter is measured the Brinell Hardness Number (BHN or HBW) can be calculated using the following Brinell hardness test formula:

Brinell Hardness Test Equation
Fig. 2: Brinell Hardness Test Equation

Note that, the term HBW stands for Hardness Brinell Wolfram carbide.
Wolfram carbide (= tungsten carbide) underlines the use of tungsten carbide balls, as opposed to the (softer) steel balls previously used (HBS).

Brinell Hardness Test
Fig. 3: Brinell Hardness Test

The minimum Test Specimen thickness is at least 10 times the indentation depth as per ASTM standard and the same is at least 8 times the indentation depth as per ISO standard.

Specifying Brinell Hardness Number

While specifying a Brinell hardness number (BHN or HB), the test conditions used to obtain the number must be specified. The standard format for specifying is “HBW 10/3000”. “HBW” refers to a tungsten carbide ball used as an indenter, as opposed to “HBS”, which means a hardened steel ball. The “10” is the ball diameter in millimeters. The “3000” is the force in kilograms force.

Sometimes, the Brinell hardness is also specified as “XXX HB YYD2” where

  • XXX is the force to apply (in kgf)
  • YY specifies the material type (5 for aluminum alloys, 10 for copper alloys, 30 for steels).

Thus the Brinell hardness of a typical steel could be written: 250 HB 30D2. The following image from wikipedia provides some typical Brinell Hardness Values of common materials.

Typical Brinell Hardness Values
Fig. 4: Typical Brinell Hardness Values

Requirements for Brinell Hardness Testing

  • Before the test, the sample must be cleaned thoroughly. Preferable if the test surface is machined, ground, and polished to get better indentation measurement.
  • Proper indenter (Steel ball or carbide Ball) as per requirement need to be selected.
  • The applicable force needs to determined beforehand.
  • The load on the specimen to be maintained for the exact period of time.
  • The indents must be positioned to keep sufficient clearance from the specimen edge and between the individual indents.

Standards for Brinell Hardness Test

The widely used standards for Brinell Hardness Test in industries are:

  • ASTM E10
  • ISO 6506
  • JIS Z 2243

Advantages of Brinell Hardness Test

Brinell Test method has many advantages:

  • The hardness of rough samples can be measured which is difficult in other methods.
  • Application of high test load (up to 3,000 Kg) is possible.
  • Wide measuring range due to availability of a range of indenter sizes and loads
  • A Brinell hardness tester can determine the hardness of all types of metals.
  • Provides reliable results.

However, Brinell test method has some disadvantages as well:

  • There could be measuring errors due to using of optical instruments.
  • Surface imperfections can interfere with the test result if the surface not prepared thoroughly.
  • The requirement of a flat surface makes this test redundant for cylindrical surfaces.

Brinell vs Rockwell hardness Test

The main difference between Brinell and Rockwell Hardness Test is provided in the table below:

Brinell Hardness TestRockwell Hardness Test
In Brinell Hardness Test the indenter is a spherical Tungsten Carbide BallFor Rockwell Hardness Test the Indenter is a Small Steel Ball (HRB) or a diamond cone (HRC)
Hardness greater than 650 HB can not be measured with this set up.No such limitation.
It measures the diameter of the indentation to calculate hardness value.Depth of indentation is measured for calculating Rockwell hardness.
A comparatively slow method.Quicker process.
Surface preparation required.No surface preparation.
 Comparatively costlyCheaper option
Table 1: Brinell vs Rockwell Hardness Test

Brinell, Rockwell, and Vickers Hardness Conversion Table

The approximate conversion of Brinell, Rockwell B & C, and Vickers hardness is provided below for sample only. One more column indicating approximate equivalent tensile strength is also added.

Brinell Hardness (HB)-3000Kg-10 mm BallRockwell Hardness (HRC)-150Kg BraleRockwell (HRB)- 100Kg 1/16″ BallVickers Hardness (HV)- Diamond Pyramid 120 KgApprox. Tensile strength (N/mm²)
80072   
78071   
76070   
75269   
74568   
74667   
73566   
71165   
69564   
68163   
65862   
64261   
62760   
61359   
60158 746 
59257 727 
57256 694 
55255 649 
53454120589 
51353119567 
50452118549 
48651118531 
46950117505 
46849117497 
456481164901569
445471154741520
430461154581471
419451144481447
415441144381422
402431144241390
388421134061363
375411123931314
373401113881265
360391113761236
348381103611187
341371093511157
331361093421118
322351083321089
314341083201049
308331073111035
300321073031020
29031106292990
27730105285971
27129104277941
26428103271892
26227103262880
25526102258870
25025101255853
24524100252838
24023100247824
2332299241794
2292198235775
2232097227755
2161996222716
2121895218706
2081795210696
2031694201680
1991593199667
1911492197657
1901392186648
1861291184637
1831190183617
1801089180608
175988178685
170787175559
167686172555
166586168549
163485162539
160384160535
156283158530
154182152515
149 81149500
147 80147490
143 79146482
141 78144481
139 77142480
137 76140475
135 75137467
131 74134461
127 72129451
121 70127431
116 68124422
114 67121412
111 66118402
107 64115382
105 62112378
103 61108373
95 56104 
90 5295 
81 4185 
76 3780 
Table 2: Brinell, Rockwell & Vickers Hardness Conversion table
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Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

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