Hardness is an important characteristic of metal that is measured in the manufacturing industry. The most common test used for hardness measurement is the Rockwell hardness test. These tests are used to determine the strength and resistance of the material which also ensures the quality of the product which is to be manufactured.
But what specifically makes Rockwell hardness test important? Why is it so popular? How do you measure the hardness from this testing method? Why and how to use scale in this test? Are some important questions which we need to look at for better understanding. In this blog, we will answer all of these questions.
I. What is the Rockwell Hardness Test?
The Rockwell hardness test is an indentation testing method standardized by ASTM E-18 and is the most used hardness test method. The indenter used here is a conical diamond or a steel ball. It is the method for the measurement of hardness of metallic and polymer elements usually. Hardness measured by the Rockwell test can describe the strength, resistance, and many other properties of the testing material. The test is widely used because of its low cost and simple procedure.
II. What is Rockwell C Scale?
Rockwell C scale is a measurement to process indentation test. This Rockwell C scale is used for the prior preparation of the hardness test such as it is important for selecting and driving the proper intender with the specimen for the test and for estimating the outcomes of hardness due to the indentation depths.
III. Why Use Rockwell Hardness Scale?
Rockwell hardness scale is widely used because of the following reasons
- Uniformity reporting test results
- Acknowledges by all industries
- Worldwide acceptance as a hardness baseline in the testing method
- Self-contained, simple and easy to use
- Fast and reliable.
- Microscopic study is not required.
- Measured by mathematical calculations and scales
IV. How Rockwell Hardness Gets Measured?
Measuring Rockwell hardness is an easy process. Generally, the recording measurement process is utilized in this test by applying a static test load for a specific time on a surface made of metal only. Then Rockwell testers are used to calculate the values with the help of the Rockwell C hardness standard scale and associate mathematical formula. For example, if you are testing Industrial knives then according to the Rockwell C hardness scale, the value lies between 40 to 65. These values are then used to calculate hardness outcomes.
The Rockwell hardness testing procedure is completed in two different steps- calculation of Value A and value B.
For accessing value, A which acts as the basis of the test, a small pressure with light controlled force is applied to the object. This caused little impression by the intender on the testing metal object.
For calculation value B, a bigger pressure with high force is applied to the specimen causing a lot of penetration on the same spot. Then the value B is also accessed and saved.
Afterward, related professional technicians subtract value (A) from the value (B). Then they compare the answer with the same value in the Rockwell C scale and the corresponding number in the table of the C scale becomes the hardness indicator of the testing metal.
V. Rockwell Hardness C Scale Conversion Chart
C | A | D | 15N | 30N | 45N | HV | HK | HB |
150kgf | 60 kgf | 100kgf | 15kgf | 30kgf | 45kgf | scale | >50gf | 10/3000 |
Daimond |
|
|
| |||||
68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 | 85.6 85.0 84.5 83.9 83.4 82.8 82.3 81.8 81.2 80.7 80.1 79.6 79.0 78.5 78.0 77.4 76.8 76.3 75.9 75.2 74.7 74.1 73.6 73.1 72.5 72.0 71.5 70.9 70.4 69.9 69.4 68.9 68.4 67.9 67.4 66.8 66.3 65.8 65.3 64.8 64.3 63.8 63.3 62.8 62.4 62.0 61.5 61.0 60.5 | 76.9 76.1 75.4 74.5 73.8 73.0 72.2 71.5 70.7 69.9 69.2 68.5 67.7 66.9 66.1 65.4 64.6 63.8 63.1 62.1 61.4 60.8 60.0 59.2 58.5 57.7 56.9 56.2 55.4 54.6 53.8 53.1 52.3 51.5 50.8 50.0 49.2 48.4 47.7 47.0 46.1 45.2 44.6 43.8 43.1 42.1 41.6 40.9 40.1 | 93.2 92.9 92.5 92.2 91.8 91.4 91.1 90.7 90.2 89.8 89.3 88.9 88.3 87.9 87.4 86.9 86.4 85.9 85.5 85.0 84.5 83.9 83.5 83.0 82.5 82.0 81.5 80.9 80.4 79.9 79.4 78.8 78.3 77.7 77.2 76.6 76.1 75.6 75.0 74.5 73.9 73.3 72.8 72.2 71.6 71.0 70.5 69.9 69.4 | 84.4 83.6 82.8 81.9 81.1 80.1 79.3 78.4 77.5 76.6 75.7 74.8 73.9 73.0 72.0 71.2 70.2 69.4 68.5 67.6 66.7 65.8 64.8 64.0 63.1 62.2 61.3 60.4 59.5 58.6 57.7 56.8 55.9 55.0 54.2 53.3 52.1 51.3 50.4 49.5 48.6 47.7 46.8 45.9 45.0 44.0 43.2 42.3 41.5 | 75.4 74.2 73.3 72.0 71.0 69.9 68.8 67.7 66.6 65.5 64.3 63.2 62.0 60.9 59.8 58.6 57.4 56.1 55.0 53.8 52.5 51.4 50.3 49.0 47.8 46.7 45.5 44.3 43.1 41.9 40.8 39.6 38.4 37.2 36.1 34.9 33.7 32.5 31.3 30.1 28.9 27.8 26.7 25.5 24.3 23.1 22.0 20.7 19.6 | 940 900 865 832 800 722 746 720 697 674 653 633 613 595 577 560 544 528 513 498 484 471 458 446 434 423 412 402 392 382 372 363 354 345 336 327 318 310 302 294 286 279 272 266 260 254 248 243 238 | 920 895 870 846 822 799 776 754 732 710 690 670 650 630 612 594 576 558 542 526 510 495 480 466 452 438 426 414 402 391 380 370 360 351 342 334 326 318 311 304 297 290 284 278 272 266 261 256 251 | – – – 739 722 705 688 670 654 634 615 595 577 560 543 525 512 496 481 469 455 443 432 421 409 400 390 381 371 362 353 344 336 327 319 311 301 294 286 279 271 264 258 253 247 243 237 231 226 |
Conclusion
This is all about the Rockwell hardness test and its conversion scale. It should be apparent from the above that if the technician is professional and trained on testing methods and formulas, the testing environment is properly set and the chart is followed properly then you will get reliable and accurate results. Rockwell hardness testing is a procedure off quality commitment for developing durable and reliable items at affordable prices in the industry. To learn more about the hardness measurement tests methods and their hardness conversion scales visit our website.