Hardness testing is a common practice used to identify the surface of a material. The hardness of a substance determines how much force is needed to make an indentation on the surface. Several different scales are used for this measurement, each with its own individual measuring system.
This article details the Brinell to Rockwell hardness conversion chart, which explains how the test results of one scale can be translated into another. The Brinell and Rockwell scales use varying levels of force to determine an object’s hardness. However, these two systems use different formulas to calculate this value. Read on to learn more about converting between these two scales.
I. What is BHN/HB in Hardness?
Brinell hardness number (BHN) and Brinell hardness (HB) are two scales that measure an object’s hardness. They both use different measurement techniques but provide the same information. Hardness is calculated by measuring how much force is needed to make a dent or scratch in an object. BHN and HB only measure the indentation or scratch and do not consider other factors like an object’s size or mass. The larger these factors are, the more unimportant they become when measuring hardness.
II. What is HR in Hardness?
HR is used to represent the Rockwell hardness scale. It is measured by applying a known force to a standard test block and measuring the resulting indentation. The Rockwell scale can be used on any surface made of either metal or plastic. The hardness ranges from 30-100, with 100 being the hardest surface.
Rockwell hardness testing has several uses in industries like construction, manufacturing, oil and gas, automotive, etc. It allows individuals to understand how well certain materials will hold up against pressure or abrasions.
III. How does Brinell Hardness Relate to Rockwell Hardness?
Brinell hardness is related to Rockwell hardness by a conversion chart. There are conversion charts that detail the value of the indentation seen in one scale or another. It also provides a common measuring system used between scales.
Both these scales use the ASTM standards to determine and represent the different hardness levels of metallic materials. The Brinell and Rockwell method uses diamond or steel ball indenters to conduct the hardness test on the test material.
IV. Is Rockwell more Accurate than Brinell?
The Brinell scale uses a diamond indenter, and the Rockwell scale uses a hardened ball or a diamond-tipped hammer. The Brinell hardness test also uses a microscope to measure the indents made by the indenter. For this reason, the Brinell scale is more accurate than the Rockwell scale. However, using the Brinell hardness test method is more expensive because of the optical measurement system setup. The Rockwell method is easier and faster, making it cheaper than the Brinell hardness method.
V. How do you Convert BHN to HR?
Several different conversion charts are used to convert between the Brinell and Rockwell hardness scales. These charts provide the values of indentation in one scale and the other. The charts show comparable hardness levels and provide a common measuring system.
Related Article: How to Convert Brinell Hardness To HRC?
Related Article: Hardness Test Comparison: Rockwell vs Brinell
VI. Brinell to Rockwell Conversion Chart
Brinell (Tungsten Carbide Ball 3000kg) | Rockwell A Scale (60kg) | Rockwell B Scale (100kg) | Rockwell C Scale (150kg) |
– | 85.6 | – | 68.0 |
– | 85.3 | – | 67.5 |
– | 85.0 | – | 67.0 |
767 | 84.7 | – | 66.4 |
757 | 84.4 | – | 65.9 |
745 | 84.1 | – | 65.3 |
733 | 83.8 | – | 64.7 |
722 | 83.4 | – | 64.0 |
712 | – | – | – |
710 | 83.0 | – | 63.3 |
698 | 82.6 | – | 62.5 |
684 | 82.2 | – | 61.8 |
682 | 82.2 | – | 61.7 |
670 | 81.8 | – | 61.0 |
656 | 81.3 | – | 60.1 |
653 | 81.2 | – | 60.0 |
647 | 81.1 | – | 59.7 |
638 | 80.8 | – | 59.2 |
630 | 80.6 | – | 58.8 |
627 | 80.5 | – | 58.7 |
601 | 79.8 | – | 57.3 |
578 | 79.1 | – | 56.0 |
555 | 78.4 | – | 54.7 |
534 | 77.8 | – | 53.5 |
514 | 76.9 | – | 52.1 |
495 | 76.3 | – | 51.0 |
477 | 75.6 | – | 49.6 |
461 | 74.9 | – | 48.5 |
444 | 74.2 | – | 47.1 |
429 | 73.4 | – | 45.7 |
415 | 72.8 | – | 44.5 |
401 | 72.0 | – | 43.1 |
388 | 71.4 | – | 41.8 |
375 | 70.6 | – | 40.4 |
363 | 70.0 | – | 39.1 |
352 | 69.3 | – | 37.9 |
341 | 68.7 | – | 36.6 |
331 | 68.1 | – | 35.5 |
321 | 67.5 | – | 34.3 |
311 | 66.9 | – | 33.1 |
302 | 66.3 | – | 32.1 |
293 | 65.7 | – | 30.9 |
285 | 65.3 | – | 29.9 |
277 | 64.6 | – | 28.8 |
269 | 64.1 | – | 27.6 |
262 | 63.6 | – | 26.6 |
255 | 63.0 | – | 25.4 |
248 | 62.5 | 24.2 | |
241 | 61.8 | 100.0 | 22.8 |
235 | 61.4 | 99.0 | 21.7 |
229 | 60.8 | 98.2 | 20.5 |
223 | – | 97.3 | 20.0 |
217 | – | 96.4 | 18.0 |
212 | – | 95.5 | 17.0 |
207 | – | 94.6 | 16.0 |
201 | – | 93.8 | 15.0 |
197 | – | 92.8 | – |
192 | – | 91.9 | – |
187 | – | 90.7 | – |
183 | – | 90.0 | – |
179 | – | 89.0 | – |
174 | – | 87.8 | – |
170 | – | 86.8 | – |
167 | – | 86.0 | – |
163 | – | 85.0 | – |
156 | – | 82.9 | – |
149 | – | 80.8 | – |
143 | – | 78.7 | – |
137 | – | 76.4 | – |
131 | – | 74.0 | – |
126 | – | 72.0 | – |
121 | – | 69.8 | – |
116 | – | 67.6 | – |
111 | – | 65.7 | – |
Conclusion
The different measuring systems between the Brinell and Rockwell hardness scales can be confusing. You must understand the differences between the two scales for your results to be accurate.
Several conversion charts are available to help determine the hardness of the material in both scales. This reference guide will help you to convert the Brinell scale to the Rockwell scale following the ASTM standards.
Related Article: ASTM Brinell Hardness Standard Test Reference Guide
Related Article: ASTM Rockwell Hardness Standard Test Reference Guide