Study on material and preparation technology of large diameter grinding ball

With the large-scale ball mill and more and more using of large-scale ball mill, the comprehensive performance of large-diameter ball grinding requirements are higher, consumption is higher. The main failure forms of large diameter grinding balls are breakage, burst, and low wear resistance, etc. In view of this situation, considering the reasonable distribution of hardness and toughness, this paper puts forward the design of new large-diameter grinding ball material and reasonable forging technology.

A low alloy steel suitable for large diameter grinding ball was designed and the effect of alloying elements on the structure and properties of the grinding ball was studied. This low-alloy steel is based on medium-carbon steel with silicon and manganese as the main alloying elements and with a small amount of chromium, molybdenum, and Microboron added. By testing the mechanical properties, microstructure and economic evaluation of 150 mm-ball after forging and air cooling treatment, the best material of large diameter grinding ball was determined. The results show that the large diameter grinding ball is dominated by Bainite, martensite and residual austenite, and the center of the grinding ball is the same as the outer structure. The volume hardness ≥50 HRC and impact toughness ≥10 j / CM2 of the large diameter ball prepared by this method after air cooling treatment after forging. Compared with the performance of other materials, this kind of grinding ball has not only high hardness but also good toughness.

The preparation method of large diameter grinding ball was determined to be forging, and the process was optimized by experiment, including the preparation of blank, forging process and post-forging treatment. At the same time, the effect of different forging and pressing technology on the properties of grinding ball was analyzed. The results show that the effect on the hardness of grinding ball is very small, but the effect on the toughness of grinding ball is great.

On this basis, the effect of low temperature tempering heat treatment on the properties of large diameter grinding balls was investigated. The results showed that the ball treated by air quenching and low-temperature tempering had the best volume hardness of more than 60HRC, about twice as much as the 65 mn ball with the large diameter, and impact toughness of more than 20J / CM2. However, due to the high hardness of the grinding ball, the heat treatment process still needs to be further optimized. The wear properties of the ball and 65Mn materials were investigated by impact abrasive wear test, and the impact wear mechanism of the two materials was analyzed. The results show that the wear resistance (w 1) of the material exceeds that of 65Mn by nearly 40 %, the impact wear mechanism of the material is fatigue wear and multiple plastic deformations wear, and the impact wear mechanism of the material is plastic deformation.