Hardness Brinell

The principle of the Brinell hardness test is that the spherical surface area of a recovered indentation made with a standard hardened steel ball under specific load is direcdy related to the property called hardness. In the following, HBN = Brinell hardness number, P = load in kgf,... 

In practice it is stiU necessary to read the diameter of the Brinell impressions with a caUbrated microscope however, the computations to derive the Brinell hardness number are uimecessary for standard loads and indentors. Table 1 of ASTM ElO (2) contains the tabulated relation between indentation diameter and hardness number. 

The latest portable Brinell testers are spring-loaded, hand-held, and digitized to read direcdy in Brinell hardness units. Their accuracy is questionable because of extreme surface sensitivity and they are not in fact Brinell testers but RockweU indenters caUbrated to read in Brinell numbers. 

Sodium—lead alloys that contain other metals, eg, the alkaline-earth metals, are hard even at high temperatures, and are thus suitable as beating metals. Tempered lead, for example, is a beating alloy that contains 1.3 wt % sodium, 0.12 wt % antimony, 0.08 wt % tin, and the remainder lead. The German BahnmetaH, which was used ia axle beatings on railroad engines and cars, contains 0.6 wt % sodium, 0.04 wt % lithium, 0.6 wt % calcium, and the remainder lead, and has a Brinell hardness of 34 (see Bearing MATERIALS). 

AHoy no. Nominal composition, wt % Compressive Yield Strength, MPa Ultimate Brinell hardness... 

Common name UNS designation 0.5% Yield strength, MPa " Compressive yield strength, MPa " Tensile strength, MPa " Elongation in 5 cm, % Brinell hardness, 500-kg load Electrical conductivity, % lACS Thermal conductivity at 20°C, W/(m-K) ... 

Chromium. Chromium [7440 7-3] also forms heat-treatable copper ahoys. These ahoys, in the heat-treated condition, have a Brinell hardness of about 120 and an electrical conductivity of about 80% lACS. 

Base-metal P numberf Weld-metal analysis A numberf Material group Nominal waU thickness Minimum specified tensile strength, base metal Metal temperature range h/in, nominal wall Minimum time, b Brinell hardness, maximum... 

For erosive wear. Rockwell or Brinell hardness is likely to show an inverse relation with carbon and low alloy steels. If they contain over about 0.55 percent carbon, they can be hardened to a high level. However, at the same or even at lower hardness, certain martensitic cast irons (HC 250 and Ni-Hard) can out perform carbon and low alloy steel considerably. For simplification, each of these alloys can be considered a mixture of hard carbide and hardened steel. The usual hardness tests tend to reflect chiefly the steel portion, indicating perhaps from 500 to 650 BHN. Even the Rockwell diamond cone indenter is too large to measure the hardness of the carbides a sharp diamond point with a light load must be used. The Vickers diamond pyramid indenter provides this, giving values around 1,100 for the iron carbide in Ni-Hard and 1,700 for the chromium carbide in HC 250. (These numbers have the same mathematical basis as the more common Brinell hardness numbers.) The microscopically revealed differences in carbide hardness accounts for the superior erosion resistance of these cast irons versus the hardened steels. 

Brinellharte, /. Brinell hardness, brlnellieren, t.t, test with the Brinell machine. Brinell-probe, /. Brinell test or sample, -zahl, /. Brinell number. 

Figure 59.20 Allowable stress as a function of Brinell hardness...

BS 3468 designation Ni-Resist type Composition (wt. %) Minimum tensile strength (X 10 N/m ) Brinell hardness... 

Brinell hardness Transverse strength Tensile strength... 

Material Density (g/cm 1 Coating weight (kg/m ) 0-025 mm thickness Brinell hardness Ratio of contraction stresses in sprayed deposits 0-51 mm thick Compressive strength (stress to collapse) (MN/m )... 

Spraying conditions make hardness values so variable that unless they are accurately known no comparisons are possible. Brinell hardness figures for sprayed molybdenum vary from 350 when produced with a reducing flame to 725 with an oxidising flame, and while a thick sprayed deposit of 0-8% carbon steel can give a figure of 330, the hardness of a particle obtained by micro hardness methods will be about 550. 

Brinell hardness number Vickers hardness number hour... 

Hardness is closely related to strength, stiffness, scratch resistance, wear resistance, and brittleness. The opposite characteristic, softness, is associated with ductility. There are different kinds of hardness that measure a number of different properties (Fig. 5-5). The usual hardness tests are listed in three categories (a) to measure the resistance of a material to indentation by an indentor some measure indentation with the load applied, some the residual indentation after it is removed, such as tests using Brinell hardness,... 

Brinell hardness A common test used to determine the hardness of a material by indentation of a specimen. Pressing a hardened steel ball generally 10 mm diameter down on a specimen carries out the test, and the diameter of the subsequent impression formed provides a basis for calculating hardness. 

Bhn Brinell hardness number CPRR Center for Plastics Recycling... 

The Brinell test uses an indentor of 10 mm diameter hardened steel ball, and applies a load which is usually 3000 kg. The Brinell hardness number (BHN) is defined as the load, F (kilogrammes), divided by the surface area of the indentation. The expression given below describes the definition. 

Indentation hardness using modified tests based on Brinell hardness measurements have been used by some researchers [148] to provide information on the surface hardness of tablets. In addition, these tests are capable of providing a measure of a tablet s plasticity or elasticity. For the most part, such tests have been confined to basic research applications in a few laboratories, but their value is beginning to be more widely recognized. 

Figure 6.2 shows yield stress versus shear modulus data for face-centered cubic metals at about 78 K. The yield stresses were derived from Brinell Hardness Numbers (Gilman, 1960). The slope of the correlation line is tb = G/333, in good agreement with the theoretical estimate of the previous paragraph. 

Figure 6.2 Yield stresses derived from Brinell Hardness Numbers for pure f.c.c. metals versus their shear moduli. The measurements were made at the temperature of liquid nitrogen (after Gilman, 1960).

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