An approximate relationship between the hardness and the tensile strength (of steel) is,
where HB is the Brinnell Hardness of the material, as measured with a standard indenter and a 3000 kgf load.
|Approx. TS 1420 MPa approximately* =|
|HB (3000)||408||Brinell 10 mm Standard 3000 kgf||80~445|
|HB (500)||>>||Brinell 10 mm Standard 500 kgf||89~189|
|HB (Tungsten 3000)||408||Brinell 10 mm Tungsten 3000 kgf||80~620|
|HB (Indentation)||3.04 mm||Brinell Indentation||6~2|
|HR-15N||82||Rockwell Superficial 15N||69~94|
|HR-15T||>>||Rockwell Superficial 15T||77~93|
|HR-30N||63||Rockwell Superficial 30N||41~85|
|HR-30T||>>||Rockwell Superficial 30T||53~82|
|HR-45N||48||Rockwell Superficial 45N||19~76|
|HR-45T||>>||Rockwell Superficial 45T||28~71|
|<<||The hardness value is below the acceptable range of the particular hardness scale.|
|>>||The hardness value is above the acceptable range of the particular hardness scale.|
|###||The hardness value is near the limit (within 15%) of the acceptable range of the particular hardness scale.|
The many hardness tests listed here measure hardness under different experimental conditions (e.g. indenters made in different sizes, shapes, and materials, and applied with different loads) and reduce their data using different formulae. As a result, there is NO direct analytic conversion between hardness measures. Instead, one must correlate test results across the multiple hardness tests.
This calculator is based on hardness data compiled from ASM Metals Reference Book 3rd ed, published by ASM International, and Machinery's Handbook 25th ed, published by Industrial Press. The calculator curve-fits multiple hardness data onto a common polynomial basis and then performs an analytic conversion. The accuracy of the conversion depends on the accuracy of the provided data and the resulting curve-fits, and on the valid ranges spanned by the different hardness tests. Converted hardness values should be used for comparative purposes only.