Brinellhardhet

Brinellhardhet, or Brinell hardness, is a measure of a material’s resistance to plastic deformation under a specified load and a 10‑mm diameter spherical indenter. It was introduced by the Swedish engineer Johan August Brinell in 1900 and remains one of the standard hardness tests for metals.

Test procedure: A hard indenter, typically a 10 mm diameter steel or tungsten carbide ball, is pressed into the material surface with a controlled load for a defined dwell time. The indentation diameter is measured, usually with optical microscopy. The Brinell hardness number HB is calculated by HB = 2P / [π D (D - sqrt(D^2 - d^2))], where P is the applied load in kilograms-force, D is the ball diameter in millimeters, and d is the indentation diameter in millimeters. In practice, the designation HBW is used when a tungsten carbide ball is employed, and HBS when a steel ball is used.

Applications and limitations: Brinell hardness is suitable for metals with relatively coarse or heterogeneous microstructures and for softer alloys, as the relatively large indentation averages properties over a larger volume. It is less appropriate for very hard, brittle materials, very thin sheets, or highly polished surfaces where measurement is difficult. Surface roughness, indentation spacing, and dwell time can influence results.

Standards and interpretation: The method is specified by standards such as ISO 6506 and ASTM E10. Brinell numbers can be correlated with other hardness scales (such as Rockwell or Vickers), but conversions are approximate and material‑dependent.