Brinell hardness test is a common method of testing the hardness of metals. Brinell hardness (HB) is a measure of the ability of a surface to resist penetration when an HB probe impacts it. The Brinell test method measures the indentation left on a specimen when the surface is hit with 20 high-pressure indents on a fixed area. The hardness number is based on the weight of the test hammer. The conversion between Brinell and Rockwell hardness tests is straightforward but not intuitive because they measure different properties. When converting from Brinell to Rockwell, you must also account for whether testing was performed on raw or heat-treated steel. This article explains how you can convert Brinell hardness to HRC.
I. What is Brinell Hardness(HB/ BHN)?
Brinell hardness (HB) is a measure of resistance to indentation of a surface with a defined area of the point of an HB probe under a defined load. The HB indentation is produced when a probe made of hardened steel and weighted according to the specified formula strikes the specimen surface. The HB test can be performed on any flat surface material, including a sheet, rod, wire, or plate.
II. What is HRC?
The Rockwell hardness test or Rockwell scale is a comparative hardness test method used to measure the hardness of metal materials by measuring the force required to deform and penetrate a specimen of a known cross-section. RHC is a scale that measures the resistance to indentation of a specific area of the specimen surface. RHC is the average indentation hardness measured in small areas, each with its shape.
Related Article: Importance of Hardness Conversion: Rockwell Hardness C Scale
Related Article: What is the Rockwell Scale?
III. How does Brinell Hardness Relate to Rockwell Hardness?
Brinell hardness is a measure of the ability of the surface to resist penetration by an HB probe and is generally used on unhardened metals. Rockwell hardness (HRC) relates to the resistance of the metal to penetration by an HRC probe and is generally used on hardened metals. HRC provides a measurement of resilience or elasticity under constant stress. Hardness tests provide information about both material strength and abrasion resistance.
IV. How do you Convert HRC to BHN? (HRC to HB/ BHN Conversion)
Brinell(3000kg 10mm ball: Standard Ball/ Tungsten Carbide Ball) – Rockwell C(150kg Diamond)
(HRC) Rockwell C scale hardness | Brinell hardness (HB) 10mm ball load 3000kgf | |
Standard ball | Tungsten carbide ball | |
68 67 66 65 64 | – – – – – | – – – (739) (722) |
63 62 61 60 59 | – – – – – | (705) (688) (670) (654) (634) |
58 57 56 55 54 | – – – – – | 615 595 577 560 543 |
53 52 51 50 49 | – (500) (487) (475) (464) | 525 512 496 481 469 |
48 47 46 45 44 | 451 442 432 421 409 | 455 443 432 421 409 |
43 42 41 40 39 | 400 390 381 371 362 | 400 390 381 371 362 |
38 37 36 35 34 | 353 344 336 327 319 | 353 344 336 327 319 |
33 32 31 30 29 | 311 301 294 286 279 | 311 301 294 286 279 |
28 27 26 25 24 | 271 264 258 253 247 | 271 264 258 253 247 |
23 22 21 20 (18) | 243 237 231 226 219 | 243 237 231 226 219 |
(16) (14) (12) (10) ( 8) | 212 203 194 187 179 | 212 203 194 187 179 |
( 6) ( 4) ( 2) ( 0) | 171 165 158 152 | 171 165 158 152 |
HB(10mm ball, 3000kg load) – HRC (120 degree cone, 150kg)
Brinell hardness (HB) 10mm ball load 3000kgf | Rockwell C HRC (120 degree cone 150 kg) |
800 | 72 |
780 | 71 |
760 | 70 |
745 | 68 |
725 | 67 |
712 | 66 |
682 | 65 |
668 | 64 |
652 | 63 |
626 | 62 |
614 | 61 |
601 | 60 |
590 | 59 |
576 | 57 |
552 | 56 |
545 | 55 |
529 | 54 |
514 | 53 |
502 | 52 |
495 | 51 |
477 | 49 |
461 | 48 |
451 | 47 |
444 | 46 |
427 | 45 |
415 | 44 |
401 | 43 |
388 | 42 |
375 | 41 |
370 | 40 |
362 | 39 |
351 | 38 |
346 | 37 |
341 | 37 |
331 | 36 |
323 | 35 |
311 | 34 |
301 | 33 |
293 | 32 |
285 | 31 |
276 | 30 |
269 | 29 |
261 | 28 |
258 | 27 |
249 | 25 |
245 | 24 |
240 | 23 |
237 | 23 |
229 | 22 |
224 | 21 |
217 | 20 |
211 | 19 |
206 | 18 |
203 | 17 |
200 | 16 |
196 | 15 |
191 | 14 |
187 | 13 |
185 | 12 |
183 | 11 |
180 | 10 |
175 | 9 |
170 | 7 |
167 | 6 |
165 | 5 |
163 | 4 |
160 | 3 |
156 | 2 |
154 | 1 |
152 | – |
150 | – |
147 | – |
145 | – |
143 | – |
141 | – |
140 | – |
135 | – |
130 | – |
114 | – |
105 | – |
95 | – |
90 | – |
81 | – |
76 | – |
Conclusion
Converting between Brinell’s hardness and Rockwell’s hardness requires understanding the relationship between these two hardness tests. In general, properties of a material such as elasticity, resilience and strength are measured by measuring the resistance to indentation of a surface. The difference between Brinell hardness and Rockwell hardness is that Rockwell provides measurements of both abrasion resistance and stress durability while Brinell measures only the latter.