The steel grinding balls surface hardness measurement

The grinding balls surface hardness defines on two diametrically opposite platforms.

Four measurements perform at each platform for the hardness determination by Rockwell method.

The first three measurements perform at the vertices of imaginary equilateral triangle with a side length from 5 to 8 mm. These measurements are tentative and the results don’t record in test report.

The fourth measurement performs in the center of the triangle. This measurement’s result records in test report.

You can previously draw points in the measurement locations for easy measurements. Three dots draw in form of triangle vertices and a fourth dot draws in form of center this triangle.

Four measurements must be providing according to Rockwell hardness measurement method (GOST 9013):

• The first three measurements are not counted after the change of the tip, the working table or stand.
• The prints number in the hardness measurement; the processing method and the measurements results indicate in the normative-technical documentation for metal products.

This measurement technique indicates in the DSTU in order to press the tip against to the grinding ball surface in these three measurements and obtain a fourth measurement with a minimum error.

The device dial have several scales:

• Scale C – a diamond cone with 120 ° angle at the apex and a 150 kgf load uses as indenter for measurements. Measure unit is HRC.
• Scale B – a 1/16 inch ball of tungsten carbide (or hardened steel) and a 100 kgs load uses as an indenter for measurements. Measure unit is HRB.

We perform a Rockwell hardness test on a scale C, i.e., the measurement provide by inserting into the sample an indenter – a diamond cone tip. The device dial arrows movement corresponds to 10 kgf preload at the first stop, and to 150 kgf full load at the second stop.