BHN = Brinell Hardness Number (kgf/mm2). BHN is the Brinell Hardness Number, proposed by Swedish engineer Johan. The acronym BHN is used to show a Brinell Hardness Number. 300 Brinell steel is a hard-wearing alloy employed in earth moving and construction applications. The Brinell hardness test generally uses a steel ball 10 mm diameter which is pressed into the surface under a load of 30 kN.