THE RESULTS OF BALL HARDNESS MEASUREMENT: HOW THE SURFACE PREPARATION OF SAMPLES AFFECT MEASUREMENT ACCURACY?

We have emphasized in our articles that it is very important to observe the requirements specialized GOST when preparation the grinding ball surface for the hardness measuring.

In this publication, we will give one example that will demonstrate the dependence of hardness measurements results on the correct surface preparation.

In February 2021, we received a complaint from one of our clients. We are talking about steel grinding balls 120mm in diameter.

10 grinding balls were selected for the quality control. All samples were prepared for hardness measurement. The surface hardness test showed an average hardness of 49.37HRC. Furthermore, the range of values oscillated from 31HRC to 60HRC. The results of the firmness measurements differed significantly from those noted in the batch certificate.

In order to resolve this situation, we have requested the above samples. The presence of the «overburn» metal and the high roughness of the measuring surface were observed on all samples. All these facts indicated that the preparation of the hardness measurement surface was not in compliance with all the requirements.

All the samples received were once again prepared at the Energosteel Laboratory. The results showed that the mean hardness of the samples obtained was 58.2HRC. The range was 56-60HRC.

So improper preparation of the surface to measure the hardness of a metal can significantly distort the result. In this particular case, the measurement error was approximately 20 per cent.

Energosteel has its own certified metal laboratory, which specializes exclusively in grinding media. Every year all our measuring equipment is subject to state inspection and certification. On several occasions, external organizations that document exports of similar used our laboratory.

We guarantee the declared quality of our grinding balls and are always ready to prove it.