Hardness of steel grinding balls determined on attorneys devices. The hardness measurement of grinding balls carried out at room temperature. The support surface of the table, instrument stands must be free from foreign matter (scale, grease, etc.).
In the measurement of hardness must be met these conditions (pic. 1):
- Gradual bringing a tip into contact with the working surface of the ball;
- Gradual application of preliminary force F0 and the main force F1 (for 2-8 sec);
- Gradual removal the main forces F1 through 1-3 sec after a sharp slowing or stopping of the indicator arrows.
Picture 1. Schematic of the hardness measuring by Rockwell method (where, F0 – preliminary force, H (kgf); F1 – the main force, H (kgf); F – the total force F0 + F1, H (kgf))
The distance between the centers of two adjacent imprints must be not less than four imprint diameters (but not less than 2 mm). Rockwell hardness value determined on a scale indicator durometer rounded to 0.5 unit of hardness. For measuring a surface hardness of the grinding ball perform two diametrically opposite platforms, as shown in Picture 2.
Picture 2. Platform preparation for measuring the hardness of the ball Ø40mm
For compliance confirmation grinding balls with fourth group of hardness prepared one platform of flat surface by removing the metal of ball to a depth of 0.5 radius (Picture 3).
Picture 3. Platform preparation for measuring the hardness of the grinding ball Ø40mm to a depth of 0,5 R
