Improvement of quality indicators of cast iron rolling rolls applicable to the production of balls

Abstract

It is stated that rolling rolls of different materials are used for the production of grinding balls. The main indicators of the quality of these tools are the level of mechanical properties: hardness, toughness, tensile strength, tensile strength, thermal endurance. Operating conditions of rolling rolls are characterized by cyclical effects of temperature and specific pressures. Therefore, the directions of research of ways to improve such an indicator of the quality of rolling rolls as thermal endurance are especially important. It is noted that the rolls of mills in the production of bullets of large diameter (80-120mm) have a much lower load on the gauges than in the rolling of bullets of small diameter, so for their production it is advisable to use high-strength cast iron with spherical graphite. Analysis of the use of cast iron rolls showed that their quality indicators are significantly affected by the shape and size of graphite inclusions. To increase the level of mechanical properties and thermal endurance of cast iron by obtaining the "correct" shape of graphite of the required size, studies were performed on the modification of the melt of the rolls of SSHNM-46. During the research it was found that the ratio of barium and magnesium in the modifier in the range of ~ 1.4: 2.0 determines the highest level of plasticity due to the optimal size of graphite inclusions. Increasing the recommended ratio of Ba: Mg over 2.3 leads to an increase in the size of graphite inclusions (more than Graz 360) and at the same time to a deterioration of their shape (up to Gf ​​9). Increasing the size of graphite inclusions leads to a decrease (by 23 ... 28%) of mechanical properties. Based on the results of research, it is determined that the highest quality indicators - the level of mechanical properties and thermal endurance has cast iron containing 3.8% C, 1.84% Si, 0.30% Mn, 2.00% Ni; up to 0.10% Cr, 0.30% Mo, up to 0.04% Mg, 2.5% Cu; up to 0.04% Ce; up to 0.08% Ba. The thermal endurance of such cast iron is 3120 cycles before failure (20 ↔600 ° C). Rolls from the offered pig-iron, having higher level of properties, are capable to provide decrease in their specific expense in 1.2 - 1, 5 times and will promote reduction of downtimes of conditions on transshipments.