NATIONAL STANDARD OF THE GRINDING BALLS IN CHINA(6)

6. Test Method

6.1 The diameter of the casting grinding ball is measured by a tool with an accuracy of not less than 0.01 mm.

6.2 The analysis method of the chemical composition should be according with the standards of GB/T 223. 3, GB/T 223. 4, GB/T 223.11, GB/T 223. 18, GB/T 223. 23, GB/T 223. 26, GB/T 223. 28, GB/T 223. 60, GB/T 223. 63, GB/T 223. 67.GB/T, 69 and GB/T 223. 72. Spectral analysis, x-ray analysis and other analytical methods can also be used.

6.3 Rockwell Hardness test should be accord with the requirements of GB/T230.1 – 230.3. The surface hardness shall be measured within 3 mm below the surface of the grinding ball. The grinding ball hardness test surface shall be made by mechanical machining, wire cutting or electric spark technology. However, wire cutting or Electrical discharge machining must be machined to remove at least the 0.5mm thickness to avoid the heat affected zone.

6.4 The impact fatigue test of grinding balls shall be carried out according to the method specified in Appendix A.

6.5 The determination and calculation of the broken ball rate shall be carried out in accordance with the provisions of Appendix B.

6.6 The metallographic examination methods, including Matrix structure, morphology of carbide or graphite and amount of eutectic phosphorus, were performed according to GB / T 13298, GB / T 8263, GB / T 7216 and GB / T 9441 The spheroidizing grade of nodular cast iron is according to GB / T 1318.

6.7 The calculation of wear rate shall be carried out in accordance with the provisions of Appendix C.