STUDIES OF THE INFLUENCE OF TECHNOLOGICAL PARAMETERS OF THE PRODUCTION OF GRINDING BALLS FROM THE REJECTION OF RAIL STEEL ON THEIR IMPACT RESISTANCE

Abstract

Based on the conducted research, a list of technological parameters of steelmaking and rolling processing that have a significant impact on the impact resistance of grinding balls from the rejection of K76F grade rail steel in the conditions of JSC "Guryev Metallurgical Plant" has been determined. Using standard methods of statistical and metallographic analyses, the degree and nature of the influence of these parameters on the rejection of grinding balls based on the results of copra tests has been established. It is determined that an increase in the content of carbon, hydrogen and sulfur in steel leads to an increase in the rejection of grinding balls according to the results of impact resistance tests. At the same time, the influenceof carbon is associated with the formation of cementite–type carbides when the carbon content increases to over-eutectoid values, the influence of hydrogen is associated with the formation of floccenes, and the influence of sulfur is associated with the formation of non-plastic sulfides. According to the rolling conversion, a significant effect of an increase in the temperature of rolling balls on an increase in their impact resistance was established, due to an increase in the plasticity of K76F steel in the actual rolling temperature range (an increase in the probability of defects brewing during deformation). It is determined that the total relative degree of influence of the parameters of steelmaking and rolling processing on the rejection of balls during impact resistance tests is 71%, the remaining 29% relate to the influence of the parameters of the heat treatment of balls, which is confirmed by the results of metallographic studies (quenching cracks were detected in the fracture of the balls).