Brinell scale

"BHN" redirects here. For other uses, see BHN (disambiguation).

Force diagram

The Brinell scale /brəˈnɛl/ characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science. It is measured as BHN, Brinell Hardness Number, and was named for Johan August Brinell.

History

Proposed by Swedish engineer Johan August Brinell in 1900, it was the first widely used and standardised hardness test in engineering and metallurgy. The large size of indentation and possible damage to test-piece limits its usefulness. However, it also had the useful feature that the hardness value divided by two gave the approximate UTS in ksi for steels. This feature contributed to its early adoption over competing hardness tests.

Test details

The typical test uses a 10 mm (0.39 in) diameter steel ball as an indenter with a 3,000 kgf (29.42 kN; 6,614 lbf) force. For softer materials, a smaller force is used; for harder materials, a tungsten carbide ball is substituted for the steel ball. The indentation is measured and hardness calculated as:

$\operatorname {BHN} ={\frac {2P}{\pi D\left(D-{\sqrt {D^{2}-d^{2}}}\right)}}$

where:

BHN = Brinell Hardness Number (kgf/mm²)

P = applied load in kilogram-force (kgf)

D = diameter of indenter (mm)

d = diameter of indentation (mm)

Brinell hardness is sometimes quoted in megapascals; the Brinell hardness number is multiplied by the acceleration due to gravity, 9.80665 m/s², to convert it to megapascals.

The Brinell hardness number can be correlated with the ultimate tensile strength (UTS), although the relationship is dependent on the material, and therefore determined empirically. The relationship is based on Meyer's index (n) from Meyer's law. If Meyer's index is less than 2.2 then the ratio of UTS to BHN is 0.36. If Meyer's index is greater than 2.2, then the ratio increases.

The Brinell hardness is designated by the most commonly used test standards (ASTM E10-14 and ISO 6506–1:2005) as HBW (H from hardness, B from brinell and W from the material of the indenter, tungsten (wolfram) carbide). In former standards HB or HBS were used to refer to measurements made with steel indenters.

HBW is calculated in both standards using the SI units as

$\operatorname {HBW} =0.102{\frac {2F}{\pi D\left(D-{\sqrt {D^{2}-d^{2}}}\right)}}$

where:

F = applied load (newtons)

D = diameter of indenter (mm)

d = diameter of indentation (mm)

Common values

When quoting a Brinell hardness number (BHN or more commonly HB), the conditions of the test used to obtain the number must be specified. The standard format for specifying tests can be seen in the example "HBW 10/3000". "HBW" means that a tungsten carbide (from the chemical symbol for tungsten or from the Spanish/Swedish/German name for tungsten, "Wolfram") ball indenter was used, 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.

The hardness may also be shown as XXX HB YYD². The XXX is the force to apply (in kgf) on a material of type YY (5 for aluminum alloys, 10 for copper alloys, 30 for steels). Thus a typical steel hardness could be written: 250 HB 30D². It could be a maximum or a minimum.

Correspondent relations among scale, indenter and test force:

Hardness symbol	Diameter of Indenter mm	F/D2	Test force N/kgf
HBW 10/3000	10	30	29420(3000)
HBW 10/1500	10	15	14710(1500)
HBW 10/1000	10	10	9807(1000)

Brinell hardness numbers

Material	Hardness
Softwood (e.g., pine)	1.6 HBS 10/100
Hardwood	2.6–7.0 HBS 10/100
Lead	5.0 HB (pure lead; alloyed lead typically can range from 5.0 HB to values in excess of 22.0 HB)
Pure Aluminium	15 HB
Copper	35 HB
Hardened AW-6060 Aluminium	75 HB
Mild steel	120 HB
18–8 (304) stainless steel annealed	200 HB
Quenched and tempered steel wear plate	400-700 HB
Hardened tool steel	600–900 HB (HBW 10/3000)
Glass	1550 HB
Rhenium diboride	4600 HB
Note: Standard test conditions unless otherwise stated

Standards

• International (ISO) and European (CEN) Standard
  • "EN ISO 6506-1:2014: Metallic materials – Brinell hardness test – Part 1: test method".
  • "EN ISO 6506-2:2017: Metallic materials – Brinell hardness test – Part 2: verification and calibration of testing machine".
  • "EN ISO 6506-3:2014: Metallic materials – Brinell hardness test – Part 3: calibration of reference blocks".
  • "EN ISO 6506-4:2014: Metallic materials – Brinell hardness test – Part 4: Table of hardness values".
• US standard (ASTM International)
  • "ASTM E10-14: Standard method for Brinell hardness of metallic materials".

See also

• Brinelling
• Hardness comparison
• Knoop hardness test
• Leeb rebound hardness test
• Rockwell scale
• Vickers hardness test

References

• Tabor, David (2000). The Hardness of Metals. Oxford University Press. ISBN 0-19-850776-3.

External links

• Brinell Hardness Test – Methods, advantages, disadvantages, applications
• Video on the Brinell hardness test on YouTube
• Rockwell to Brinell conversion chart (Brinell, Rockwell A,B,C)
• Struers hardness conversion table (Vickers, Brinell, Rockwell B,C,D)
• Brinell Hardness HB conversion chart (MPa, Brinell, Vickers, Rockwell C)