IS THE IDENTITY TRUE: «HIGH VOLUME HARDNESS» = «QUALITY»?

Not long ago, we announced the appearance of the 6th hardness grade in DSTU 8538:2015. The innovations were more focused on the volumetric hardness of grinding balls. In this article, we want to talk about the fact that even a high value of this indicator does not guarantee high quality.

The volumetric hardness of grinding balls is a calculated measure of hardness that generalizes (averages) its value over the entire volume of the grinding ball.

The volumetric hardness (VH) is calculated by the formula:

where H_surf, H_0,25,H_0,5, H_0,75, H_c, – the hardness at a distance from the surface of the grinding ball in parts of the radius.

Frequently comparing our grinding balls with competitors, the end-user makes a simple comparison of this indicator. In other words, where the value is higher, it is better. This is not always true. For illustration below we shall give a comparison of hardness of steel ball with diameter of 80mm 6 of hardness grade (volume hardness – 59 HRC) of «Energosteel Plant» production with forged ball (volume hardness – 57 HRC) of one foreign producer:

As shown in figure, both samples have approximately the same volumetric hardness.

In fact we observe that the ball (analogue) is considerably less in hardness than the ball of «Energosteel» production, especially at the depth 0.60R (radius). This indicates that after a certain period of operation the ball (analogue), the unit consumption will increase significantly and a situation of grinding deterioration may occur. When using steel grinding balls of «Energosteel» production the probability of this situation is reduced to zero.

Grinding balls of 6 hardness grade according to DSTU 8538:2015 produced by LLC «Plant «Energosteel» have uniform volumetric hardness on all cross section of grinding ball. I.e. the ball is equally hard on the surface and in the centre. This unique feature of our grinding balls guarantees our clients that grinding balls will wear out evenly, regardless of the service life. This in turn will lead to a reduction in specific consumption.

We hope that our information will help you to understand and correctly choose the manufacturer of grinding balls, as well as help to avoid a situation where acquired grinding balls, as you were sure, with «increased hardness» will result in an increase of the specific consumption and a decrease in the productivity. Energosteel specialists are always ready to give you any advice and guarantee that our grinding balls will have a positive effect on the grinding process in your company.