Steel hardness test methods and hardness conversion

The hardness of steel is important to many processes. Steel hardness describes the properties of steel that enable it to resist plastic deformation, indentation, penetration, and scratching. In engineering, steel hardness is important because the inherent resistance of the surface to withstand friction or erosion by oil, steam, and water, typically increases with the relative hardness of steel.

The higher the steel hardness, the more resistant the surface will be. This creates difficulties in surface operations, such as cutting and machining. There is no one quality that influences the hardness of steel, or that can be termed ‘hardness’. There are various empirical steel hardness tests. The most important and popular of these measures are Brinell, Rockwell, and Vickers.

The hardness tests do not measure hardness in units, but as an index. Because each of the steel hardness tests are so common, the index is given as a number followed by a code to indicate the test method.

Which steel hardness test to use

Traditionally, Brinell is used for softened steels and Vickers is used more widely. These tests measure the diameter of the indentation left on the surface of the metal. The Rockwell method assesses steel hardness by measuring the depth of penetration of an indentation.

Brinell steel hardness test

The Brinell test was the first widely used standardised steel hardness test. It requires a large test piece and leaves a large indentation; therefore, it is limited in its usefulness. The acronym BHN is used to show a Brinell Hardness Number. The term ‘Brinelling’ has come to mean the permanent indentation of any hard surface. The test involves a large, heavy ball, which is pushed against steel at a predetermined level of force. The depth and diameter of the mark are measured and indexed to provide a BHN.

Rockwell steel hardness test

The Rockwell scale is also based on the diameter of an indentation. A Rockwell hardness tester is much lighter and more mobile. It determines steel hardness by putting pressure on steel. It was developed in the US to determine the change in hardness between steel and heat treated steel.

Vickers steel hardness test

Developed in the UK as an alternative to the Brinell test, the Vickers hardness test can test all materials, whether hard or soft. It was the widest scale of indices, and is easier to use than the other steel hardness tests. The Vickers hardness test provides a Vickers Pyramid Number (HV) or a Diamond Pyramid Hardness (DPH) number. This is because the indentor is a pyramid or cone shape.

Steel hardness conversion

Because there are so many different types of steel hardness tests, a conversion table, such as the one below, allows us to take one measure and estimate the relative hardness on another measurement scale. Please bear in mind that you need to denote that a measurement is converted, as each of the scales offer different measurements, which means that conversions remain in estimate form only. Download the ShapeCUT Steel Hardness Conversion Table as a handy fact sheet.

For all your steel cutting needs, call ShapeCUT. We have been working with steel for over 20 years, and our modern machines enable us to provide high-quality same-day service.

Hardness Conversion Table

Tensile
Strength 
(N/mm2)

Brinell Hardness 
(BHN)
Vickers Hardness 
(HV)
Rockwell
Hardness 
(HRB)
Rockwell Hardness 
(HRC)
285 86 90
320 95 100 56.2
350 105 110 62.3
385 114 120 66.7
415 124 130 71.2
450 133 140 75.0
480 143 150 78.7
510 152 160 81.7
545 162 170 85.0
575 171 180 87.1
610 181 190 89.5
640 190 200 91.5
675 199 210 93.5
705 209 220 95.0
740 219 230 96.7
770 228 240 98.1
800 238 250 99.5
820 242 255 23.1
850 252 265 24.8
880 261 275 26.4
900 266 280 27.1
930 276 290 28.5
950 280 295 29.2
995 295 310 31.0
1030 304 320 32.2
1060 314 330 33.3
1095 323 340 34.4
1125 333 350 35.5
1155 342 360 36.6
1190 352 370 37.7
1220 361 380 38.8
1255 371 390 39.8
1290 380 400 40.8
1320 390 410 41.8
1350 399 420 42.7
1385 409 430 43.6
1420 418 440 44.5
1455 428 450 45.3
1485 437 460 46.1
1520 447 470 46.9
1555 456 480 47.7
1595 466 490 48.4
1630 475 500 49.1
1665 485 510 49.8
1700 494 520 50.5
1740 504 530 51.1
1775 513 540 51.7
1810 523 550 52.3
1845 532 560 53.0
1880 542 570 53.6
1920 551 580 54.1
1955 561 590 54.7
1995 570 600 55.2
2030 580 610 55.7
2070 589 620 56.3
2105 599 630 56.8
2145 608 640 57.3
2180 618 650

57.8

DISCLAIMER: This specification is for information purposes only. ShapeCUT takes no responsibility for the suitability of the steels referred to in this specification without prior notification. ShapeCUT takes no responsibility for any errors or omissions, or for any consequences resulting from its use.